BSEEP Active Design Guidebook
BSEEP Active Design Guidebook
BSEEP Active Design Guidebook
ACTIVE
DESIGN
FOREWORD
The climate is changing. The earth is warming up. The Intergovernmental Panel on Climate
Change (IPCC) Fourth Assessment Report (AR4) has stated an increase of 0.74C in the
global average surface temperature which could wreck havoc upon humans, radically altering
habitats and accelerating extinction.
International action to combat climate change is necessary. The Global Environment Facility
(GEF) has set up funds to help combat climate change and the Building Sector Energy
Efficiency Project (BSEEP) is one such project financed by those funds. The United Nation
Development Programme (UNDP) and Public Works Department (PWD) Malaysia are the
global and local implementers for BSEEP respectively.
The goal of BSEEP is to reduce annual growth rate of Green House Gas (GHG) emissions from
the building sector in Malaysia by improving energy utilisation efficiency. BSEEP consists of 5
components. This technical guidebook is one of the outputs from Component 4 which is on
information and awareness enhancement.
This guidebook is divided into 2 parts, i.e. (i) Passive and (ii) Active elements in energy
efficient building design. This is the first part of the guidebook which focuses on passive
design.
I hope the designers in this country will find this guidebook relevant and useful in working
towards energy efficient buildings in particular and sustainable development in general.
In closing, I would like to thank and congratulate to all parties involved in the production of
this guidebook. I would also like to give a special mention to the support given by Mr Tang
Chee Khoay, Mr Nic Chin Yee Choong and Mr Kevin Hor Chun Wah in putting together this
guidebook in such a short period of time.
Chairman
National Steering Committee
Building Sector Energy Efficiency Project (BSEEP)
PREFACE
This Energy Efficiency Technical Guideline for Active Design was written specifically for Malaysian climate zone. It is an
attempt to provide a simple and yet useful guideline to practising building designers in Malaysia for design decisions to be
made quickly for the promotion of energy efficiency in buildings.
An industry dialogue was carried out on 13th June 2012 to gain an understanding on the status of current energy efficiency
design practices and to identify the information that is sought after by the industry, for energy efficiency to be practised on
new building developments. 18 industry leaders from both private and public sectors attended the dialogue session. The
valuable contributions by these attendees are recognised herewith:
Name
Organisation
Unit Kecekapan Tenaga dan Tenaga Diperbaharui, Cawangan Kejuruteraan Mekanikal, JKR
Unit Kecekapan Tenaga dan Tenaga Diperbaharui, Cawangan Kejuruteraan Mekanikal, JKR
Ar. Thulasaidas S.
Sandra Shim
A wish list of information was created from the industry dialogue session. From this wish list a few sets of building
energy simulation studies (using the weather data of Malaysia) were developed and conducted to provide the foundation
for the recommendations made in this guideline.
The building energy simulation tool used for the studies made in this guide is IES
<Virtual Environment> version 6.4 from the UK (http://www.iesve.com). This software
meets the requirements of ASHRAE Standard 140 and Cibse AM11 for a building
dynamic energy simulation tool. This software is adequately comprehensive, allowing
different types of passive and active design features to be studied for the purpose of
this guideline.
The weather data used for the energy simulation study is the Test Reference Year (TRY)
weather data from an analysis of 21 years of weather data from the weather station
of Subang Airport in Selangor and is described in detail in Chapter 2 of this guideline.
Building energy simulation studies require a significantly high amount of data to be
provided to model a building accurately. The amount of data that is required is reflective
of the actual situation in a building, where there are thousands of parameters that are
likely to be different from building to building, such as the insulation thickness on the
walls and roofs, occupancy schedules, equipment power, equipment schedules and etc.
Therefore, it is not possible for this guideline to provide a guarantee on the absolute
amount of energy reduction gained by the analysed feature as recommended by a
fellow stakeholder during a stakeholder engagement session for this guideline.
The purpose of this guidebook is primarily to develop an understanding of the various
possibilities and potential to improve energy efficiency in a building with each design
feature. This guidebook is to give building designers a feel of the potential energy
reduction from these features analysed for further and deeper investigation to be made
on the actual building project whenever it is deems appropriate.
The accuracy and reliability of using energy simulation studies for this guidebook can be
justified by the following items:
1. ASHRAE 90.1 recognises the accuracy and dependability of energy simulation studies.
Section 11 and appendix G of ASHRAE 90.1 provides detailed guideline to conduct
energy simulation studies to assess energy efficiencies in buildings.
2. For the past 10 years, many of the published ASHRAE journals on energy efficiency are
based on energy simulation studies. This includes a series of 4 part articles in ASHRAE
journals on optimising air-conditioning system by Steven T. Taylor from 2011 to 2012.
3. The development of Malaysian Overall Thermal Transmission Value (OTTV) in 1987 for
the Malaysian Standard (MS) 1525 was based entirely on the energy simulation of one
typical office building model.
Finally, due to the limited time available to produce this guideline, only one building
model was used to derive all the estimated energy reductions. Different building
sizes, shapes and models will yield slightly different results. However, the results and
recommendations from this guideline is deemed accurate enough as a general guide
to make informed building design decisions quickly in the interest of energy efficiency
in buildings. Building designers are cautioned that if the designed building operational
scenario is significantly different from the assumptions made in Chapter 6, it would be
best to conduct another set of simulation studies based on the expected scenario of
the actual building to provide a more accurate energy reduction potential for the actual
designed building.
ACKNOWLEDGEMENTS
I would also like to acknowledge the following people that helped to complete this guidebook for the industry. It has been
a real honour for me to receive such valuable information, comments and advice from practising industry experts. Thank
you very much for your contributions:
Kevin Hor Chun Wah, whom being the National Project Manager for BSEEP, has a keen interest in lighting systems and
technologies and provided many useful comments for the chapter on lighting.
Qamarrul Ariffin and Ken Lo, from Osram, for helping to review and provide constructive critique on the chapter on
electrical lighting as well.
Darren Lai, Zhao, Lau, Peter, Tan, Ah Chai, Yow and Kuan Yee, from Trane Malaysia, for helping to review and provide
many useful ideas and tips to help us revise the chapters on Air Conditioning System Design, Optimisation of Air-Side AirConditioning System and Optimisation of Water-Side Air-Conditioning System.
And finally, the attendees of the Active Guideline stakeholder engagement on 18th July 2013, for providing extremely
valuable feedback on the draft version and pointing out many issues that needed to be carefully addressed in the active
guideline. These attendees are:
Name
Organisation
James Chua
REHDA, GreenRE
MASHRAE
MASHRAE
Faiz Fadzil
KeTTHA
JKR
BPKS, JKR
Zanita Jaafar
BPKS, JKR
BPKS, JKR
CAST, JKR
Thiagarajen
CAST, JKR
Mohd Fatihi
CAST, JKR
CA, JKR
CA, JKR
CKE, JKR
Mohamed Shahril
CKE, JKR
CKM, JKR
CKM, JKR
CKM, JKR
CKM, JKR
Zulkiflee Umar
Suruhanjaya Tenaga
Norrasmi Mohamed
Mahendra Varman
Universiti Malaya
ACEM/BEM
ACEM/BEM
To all the contributors above thank you very much for your kind assistance in the development of this active guideline for
energy efficiency in buildings.
CK Tang
Lead Consultant
6 | Building Energy Efficiency Technical Guideline For Active Design
ACTIVE
DESIGN
MESSAGES FROM
THE AUTHORS
CK TANG
NIC CHIN
Lead Consultant
Consultant
Dear Readers,
Thank you for your interest in the Building Energy Efficiency Technical
Guideline for Passive and Active Design. We hope that these guidelines
will be useful to you.
This series was developed as part of the Building Sector Energy Efficiency
Project between JKR and UNDP. We have produced this book for
dissemination to the building industry for FREE and hope that the book
will assist building owners, engineers and architects in building more
energy efficient buildings. As intended of a guideline, we hope that the
potential savings estimates will allow you to make informed decisions on
architectural, material and technology choices.
To download a copy of the book, please visit www.jkr.gov.my/bseep. As
with all good guidelines, the Passive and Active Technical Guidelines will
constantly evolve and improve. To receive updates on the book please
register your mailing address at www.jkr.gov.my/cbd/
Best Regards,
Kevin Hor
National Project Manager
Building Sector Energy Efficiency Project (BSEEP)
kevin.hor@jkr.gov.my
CONTENTS
TABLE OF CONTENTS
Foreword
Preface
Messages from the Authors
3
4
8
CHAPTER 1
FUNDAMENTALS OF ENERGY EFFICIENCY IN BUILDINGS
Introduction
A Holistic Approach
Cream Skimming Avoidance
1st Law of Thermodynamics
Fundamentals of Air Properties
Dry Bulb Temperature (C)
Wet Bulb Temperature (C)
Dew Point Temperature (C)
Moisture Content in Air (kg/kg)
Relative Humidity (%)
Effective Sky Temperature (C)
Fundamentals of Heat
Sensible Heat
Latent Heat
17
18
21
21
23
23
23
23
23
23
23
24
24
24
24
26
26
27
28
28
CHAPTER 2
MALAYSIAS WEATHER DATA
Introduction
Source of Weather Data
Location and Sun-Path
Dry Bulb Temperature
Design Potential
Design Risk
31
31
32
34
34
34
35
35
35
36
36
36
CONTENTS
Relative Humidity
Design Potential
Design Risk
Ground Temperature
Design Potential
Design Risk
Wind Speed
Design Potential
Design Risk
Summary
37
37
37
38
38
38
39
39
40
41
41
41
42
42
42
43
43
43
44
44
44
45
45
45
46
46
46
48
CHAPTER 3
ENERGY RATING OF ELECTRICAL APPLIANCES
Introduction
Energy Efficiency Programmes
Energy Star Programme
EU Energy Efficiency Label
Singapore Energy Labelling Scheme
Malaysia Energy Efficiency
51
52
52
54
56
58
60
63
64
CONTENTS
CHAPTER 4
EFFICIENT LIGHTING DESIGN STRATEGIES
Introduction
Key Recommendations
Useful Lighting Terminologies
Candela
Lumen
Lux level (Illuminance)
Lamp
Luminous Efficacy
Colour Rendering Index (CRI)
Luminaire Light Output Ratio
Photometric Distribution (Polar Curve)
Glare Index
Lighting Power Density
Lighting Controls
Dimming Controls
Manual Switches
Occupancy/Motion Sensor
Daylight Sensor
Time Delay Switch
Centralised Lighting Management
Low Ambient Light Level & Task Lighting
Light Zoning
Summary
67
68
69
69
69
70
71
71
71
72
72
73
74
75
75
75
75
76
76
76
77
77
78
80
81
81
81
82
84
84
84
84
85
88
CHAPTER 5
AIR-CONDITIONING SYSTEM DESIGN
Introduction
Key Recommendations
Space Cooling Load
People Heat Gain
Electrical Lighting Heat Gain
Equipment and Appliances Heat Load
Conduction and Solar Radiation Heat Gain
Infiltration Heat Gain
91
92
93
95
96
97
98
101
102
102
CONTENTS
Fan Power
Conduction Heat Gain from Ducts
104
108
109
109
110
111
112
Chiller Load
Chilled Water Pump
Conduction Heat Gain in Pipes
CHAPTER 6
SIMULATION INPUT DETAILS FOR CHAPTER 7 & 8
Introduction
Simulation Engine
Weather Data
Building Model
Base Model Inputs
Air Conditioning System
Air-Side Details
Water-Side - Chilled Water Loop
115
115
116
116
118
120
120
124
127
127
128
129
130
131
132
133
134
135
136
CHAPTER 7
OPTIMISING THE AIR-SIDE AIR-CONDITIONING SYSTEM
Introduction
Key Recommendations
Constant Air Volume (CAV) System
Simulation Studies
Performance of CAV System Operating at Partial Load
139
141
142
143
146
148
149
150
150
151
153
154
156
158
161
162
CONTENTS
CHAPTER 8
OPTIMISING THE WATER-SIDE AIR-CONDITIONING SYSTEM
Introduction
Key Recommendations
Chilled Water Distribution System
Simulation Studies
Results
Chiller Efficiency
Simulation Studies
Results
Summary of Chiller Efficiency
165
166
168
170
170
172
173
174
177
177
178
179
180
182
183
187
188
188
189
189
190
191
192
195
196
198
CHAPTER 9
COMMISSIONING, FINE-TUNING & CONTINUOUS MONITORING
Introduction
Key Recommendations
Appointment of Building Energy Manager
Commissioning
Summary
201
202
203
204
204
205
208
209
209
210
210
210
210
210
210
210
210
210
211
211
212
215
Glossary of Terms
216
Fine-Tuning
Lighting Schedules
Motion Sensor Calibration
Air-Temperature Set-Point
Supply Air Redistribution
Lift Operation Mode
Air-Conditioning Hours
Computers & Other Electrical Appliances
Occupant Awareness Campaign
Continuous Monitoring
Energy Sub-Meters
Energy Management System (EMS)
CHAPTER
FUNDAMENTALS
OF ENERGY
EFFICIENCY
IN BUILDINGS
FUNDAMENTALS OF
ENERGY EFFICIENCY
IN BUILDINGS
INTRODUCTION
Optimising the energy efficiency in
a building is a far more cost effective
measure to reduce carbon emissions
than by using renewable energy.
Unfortunately, there is no magic
silver bullet when it comes to energy
efficiency in office buildings for the
Malaysian climate. In other words,
there does not exist one single item
which can reduce building energy
consumption by 50% or more.
Energy efficiency in office buildings
in this climate has to be addressed
holistically by addressing every
available opportunity.
The typical energy breakdown
in Malaysian office buildings is
50% for air-conditioning, 25% for
electrical lighting and 25% for small
power (equipment). In addition, airconditioning energy consumption is
not only due to heat from solar gain
in the building, but also due to heat
from electrical lighting, electrical
equipment, conduction (through
the building fabric), the provision of
fresh air in the building and human
occupancy. Each of these items
contribute a significant part to the
It is not possible to
reduce the energy
consumption in
a building by
50% or more by
addressing only
one item alone
Due to the rapid technological
advancements in Malaysia in
electrical lighting, air-conditioning
and the availability of cheap energy
from the mid-20th century onwards,
unhealthy energy efficiency design
practices in has crept into building
design and operation. Today, one
can easily identify hundreds, if not
thousands, of items in building
design and construction that can
A HOLISTIC APPROACH
A study on the reformulation of the Malaysian Standard (MS) 1525, Overall Thermal Transfer Value (OTTV) in 2005
by Danida, produced a simple chart on the energy breakdown in typical buildings. This chart is important in this section
because it provides a clear understanding of the typical energy distribution in typical office buildings in Malaysia. This chart
then allows a clear strategy to be developed to address the energy efficiency priorities in buildings.
140
38%
120
21%
kWh/m2/year
100
27%
80
4%
6%
25%
25%
60
40
20%
11%
Fan Gain
18%
20
8%
0
AHU Fan Energy
Lighting Energy
Chiller Energy
A chiller system is used to remove heat from a building to maintain it at a certain temperature for
occupant comfort. Heat in a building is generated from solar radiation, conduction, people, fresh
air intake, electrical lights, electrical fans and electrical equipment. The amount of heat generated
by each element may be marginally different between buildings but will not significant enough to
change the conclusion of the study made in 2005.
The chiller energy breakdown in Chart 1.1 shows the following heat elements that are removed by
the air-conditioning system to provide comfortable conditions in the building:
1 Fan Gain
7 Dehumidification of
People Latent Gain
3 Lighting Gain
8 Dehumidification of
Fresh Air Ventilation
Depending on the cooling load, a typical chiller system may consist of a chiller, chilled water pump, condenser water pump
and cooling tower or just a simple air-cooled compressor unit placed outdoors (as in a split unit air-conditioning system).
The efficiency of the chiller system can vary significantly depending on the combination of equipment selected by the airconditioning system designer based on the available budget and design concept.
Based on Chart 1.1, it can be summarised that energy efficiency in buildings should be prioritised according to these seven
(7) fundamental steps:
2 Lighting Efficiency
4 Fan Efficiency
The key reason why the 1st law of thermodynamics is mentioned in this chapter is to dispel a few building industry myths
that hinder the understanding energy flow in buildings. These are some of the common myths in the industry:
In summary, energy changes form but it cannot be destroyed. By having a clear understanding of energy flow, one can
start to appreciate how energy changes within the building and how improvements made in one area has a cascading effect
on the entire building. Simply put, almost all electrical energy used within the building ends up as heat which the airconditioning system has to remove in order to keep the building conditions comfortable for the occupants.
FUNDAMENTALS OF HEAT
Heat is actually a form of energy. With the right
mechanism, heat can be converted into other forms of
energy such as kinetic or electrical energy. Heat is also
a form of energy that can easily be stored in building
materials with a high thermal capacity such as water,
bricks and stones.
There are two distinct types of heat: Sensible Heat and
Latent Heat.
LATENT HEAT
Latent Heat is heat energy that causes the change of
phase of a substance from one state to another without
affecting the temperature. For example, water remains at
100C while boiling. The heat added to keep the water
boiling is Latent Heat. The quantity of heat that is added to
the water in order for it to evaporate cannot be displayed
by an ordinary thermometer. This is because both the
water and steam remain at the same temperature during
this phase change.
SENSIBLE HEAT
Sensible Heat is heat energy that causes a change in
temperature in an object. In building science, any object
that causes a temperature increase is called Sensible
Heat. These objects include computers, printers, lighting,
solar radiation through windows, etc.
Latent Heat
100C
100C
Sensible Heat
18C
100C
CONDUCTION
CONVECTION
RADIATION
RADIATION
Microscopic view
of a gas
Microscopic view
after condensation
Microscopic view
of a liquid
Microscopic view
after evaporation
FUNDAMENTALS OF
THERMAL COMFORT
There have been many studies linking thermal comfort
to productivity in offices.1 More importantly, compared
to the cost of salary for building occupants, the energy
cost in a building is almost insignificant; making it almost
impossible to justify energy efficiency in a building that
reduces building occupant productivity.2 Therefore,
thermal comfort in a building has a higher priority than
energy efficiency in building. Fortunately, when energy
efficiency is implemented well in a building, the thermal
comfort would be improved as well.
Within building science, thermal comfort is defined
as a heat transfer balance between a person with his/
her surroundings. In many literatures, thermal comfort
is also defined as a condition of mind which expresses
thermal satisfaction within the environment. Because
there are large variations, both physiologically and
psychologically, from person to person, it is not possible
to satisfy everyone in a space with the same conditions.
Many thermal comfort models recommend satisfying
a minimum of 80% to 90% of the occupants as the
minimum criteria for thermal comfort.
Although there are many thermal comfort models
available in the market today; it is recommended to gain
a basic understanding of the three (3) thermal comfort
models that are described in this chapter as a foundation.
These three (3) basic thermal comfort models are:
1. Operative Temperature
2. Fangers PMV-PPD Thermal Comfort Model (for
Conditioned spaces)
3. Adaptive Thermal Comfort Model (for Natural and
Hybrid Ventilation spaces)
The above 3 thermal comfort models are internationally
recognised by both ASHRAE and ISO standards.
1
D.P. Wyon, Indoor environmental effects on productivity. IAQ 96 Paths to better building
environments/Keynote address, Y. Kevin. Atlanta, ASHRAE, 1996, pp. 515.
2
R.Kosonen, F.Tan, Assessment of productivity loss in air-conditioned buildings using PMV index.
Halton OY, CapitaLand Commercial Limited, 2004.
1 OPERATIVE TEMPERATURE
The Operative Temperature is perhaps the simplest and
most useful indicator of thermal comfort in buildings.
Operative Temperature describes the average of Air
Temperature and Mean Radiant Temperature. While Air
Temperature is simply the temperature of the air, the
Mean Radiant Temperature is more complicated; it is the
average surface temperature of the surrounding walls,
windows, roof and floor. Hot equipment like ovens and
halogen lights also add to the Mean Radiant Temperature
of a space. In addition, the view factor (percentage of
exposure) of each surface also contribute to the final
Mean Radiant Temperature of a space.
In a typical conditioned space in Malaysia where the
relative humidity ranges from 50% to 65%, the Operative
Temperature is recommended to be maintained below
25C to provide comfortable thermal conditions. This
means that if the Air Temperature is set to 23C, the
maximum allowable Mean Radiant Temperature is 27C
in order to obtain an Operative Temperature of 25C.
This also means that if a rooms Mean Radiant
Temperature is more than 28C, the Air Temperature of
the room needs to be lower than 22C to provide comfort
to the building occupants. Table 1.1 on the next page
shows the various Air Temperatures in combination with
the Mean Radiant Temperatures to provide the same
comfort condition.
Mean Radiant
Temperature (C)
Operative Temperature
(C)
22
28
25
23
27
25
24
26
25
25
25
25
26
24
25
27
23
25
28
22
25
-2
cold
cool
-1
slightly
cool
+1
slightly
warm
neutral
+2
+3
warm
hot
80
PPD
All six of these factors may vary with time. However, this
standard only addresses thermal comfort in a steady
state. As a result, people entering a space that meet
the requirements of this standard may not immediately
find the conditions comfortable if they have experienced
different environmental conditions just prior to entering
the space. The effect of prior exposure or activity may
affect comfort perceptions for approximately one hour.
60
40
20
0
-3
0.5
1.5
2.5
PMV
Toc
31
29
27
25
90%Thermal
Acceptability
23
21
19
17
15
5
10
15
20
25
30
35
3
Deuble, M.P. and de Dear, R.J. (2012) Mixed-mode buildings: A
double standard in occupants comfort expectations, Building and
Environment, Volume 54, Issue 8, Pages 53-60
4
Denis J. Bourgeois, 2005, Detailed occupancy prediction, occupancysensing control and advanced behavioural modelling within wholebuilding energy simulation, Chapter 6, Thermal adaptation: applying
the theory to hybrid environments
SUMMARY
In a conditioned space, it is recommended to use Fangers PMV-PPD thermal comfort model to predict the comfort
condition. Alternatively, the design operative temperature of not more than 25C is suggested as the simplest design
indicator of thermal comfort in conditioned spaces in this climate zone. However, for a naturally ventilated space, the
Adaptive Thermal Comfort model is recommended to be used instead of Fangers PMV-PPD model. In this climate zone the
Adaptive Thermal Comfort model states that we should maintain operative temperature below 28C for a 90% acceptance
of the comfort level provided.
END OF CHAPTER 1
CHAPTER
MALAYSIAS
WEATHER DATA
2 MALAYSIAS
WEATHER DATA
INTRODUCTION
A clear understanding of Malaysias weather data enables designers to design
buildings that benefit from the climate conditions
The daily climate in Malaysia is fairly consistent throughout the entire year; therefore it is useful to have an overview of
an average days patterns and the maximum and minimum hourly weather values for a full year. This chapter provides
information on dry bulb temperature, wet bulb temperature, relative humidity, humidity ratio (moisture content), dew
point temperature, global radiation, direct radiation, diffuse radiation, cloud cover, wind speed & direction, effective sky
temperature and ground temperature. Charts are provided to make it easier to understand the data and a table of raw cross
tabulation data made using the pivot table function in Excel is also provided for users who wish to make use of this data for
more in-depth analysis on their own.
Units
Cloud Cover
[oktas]
[C]
[C]
Relative Humidity
Global Solar Radiation
[%]
[100*MJ/m2]
Sunshine Hours
[hours]
Wind Direction
[deg.]
Wind Speed
[m/s]
1
Reimann, G. (2000) Energy Simulations for Buildings in Malaysia, Test Reference Year, 18-25.
2
The values are integrated over a period of one hour, but the exact time interval has not been
specified.
Latitude (N)
Longitude (E)
3.12
101.55
Solar Noon
13:11
2. Penang
5.30
100.27
13:16
3. Johor Bharu
1.48
103.73
13:02
4. Kota Bharu
6.17
102.28
13:08
5. Kuching
1.48
110.33
12:36
6. Kota Kinabalu
5.93
116.05
12:13
The sun-path diagram for the 6 locations above is presented in this section and shows that the
sun position is almost the same for all six (6) locations, except for the time of the Solar Noon.
The Solar Noon (when the sun is at its highest point) is 13:11 in Kuala Lumpur, while in Kota
Kinabalu it is about an hour earlier at 12:13.
The sun-path is generally from east-west with the sun approximately 25 to the north during
summer solstice and 25 to the south during winter solstice for all locations in Malaysia.
The sun-path diagram is a useful tool to help in the design of external shading devices. The
sun-path diagram is used to estimate the suns angle at various times of the day and year,
allowing architects and engineers to design shading devices to block or allow direct sunlight
into the building at any time of the day.
CHART 2.1.1 | LARGE SUN-PATH OF KUALA LUMPUR
Minimum
Maximum
34
32
30
28
26
24
22
Average
24.6
24.3
24.1
23.9
23.8
23.7
23.8
25.2
27.3
29.0
30.1
30.9
31.3
31.3
30.7
29.8
28.9
28.0
26.9
26.2
25.7
25.4
25.0
24.8
Minimum
22.5
22.0
21.8
21.5
21.0
20.8
20.6
22.1
22.8
23.7
23.8
23.9
22.3
24.1
23.4
23.2
23.4
23.4
23.3
23.0
22.8
22.8
22.8
22.5
Maximum
27.0
26.8
26.5
26.3
26.2
26.0
26.3
28.5
30.8
32.4
33.4
34.0
34.8
35.2
35.6
34.8
33.8
33.0
30.4
29.8
28.8
28.6
28.1
28.0
Std Dev.
0.9
0.9
0.9
0.9
0.9
0.9
0.9
1.1
1.4
1.5
1.5
1.7
1.9
2.1
2.5
2.6
2.4
2.1
1.7
1.4
1.2
1.1
1.0
0.9
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
6:00:00 AM
20
3:00:00 AM
Average
36
12:00:00 AM
Degree Celcius
Average
Minimum
Maximum
30
28
26
24
22
20
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
6:00:00 AM
18
3:00:00 AM
DESIGN POTENTIAL
The wet bulb temperature is a good indicator
of the potential of a direct evaporative
cooling strategy. If the direct evaporative
cooling system is 100% efficient, the lowest
air temperature that can be achieved by
the evaporative cooling system is the wet
bulb temperature. The efficiency of direct
evaporative cooling devices depends on the
system water droplet size, wetted surface
area and air speed, and an efficiency of up
to 90%3. During the daytime, the dry bulb
temperature is significantly higher than the
wet bulb temperature; therefore, evaporative
cooling will work well. However, during the
night time, the dry bulb temperature is very
close to the wet bulb temperature, therefore
the effectiveness of evaporative cooling is
reduced significantly, i.e. the reduction of
air temperature is very small with the use of
evaporative cooling, even at 90% efficiency.
12:00:00 AM
DESIGN RISK
The wet bulb temperature is not much affected
by the urban heat island effect. Therefore, the
wet bulb temperature provided by the TRY is
reliable to be used.
Degree Celcius
Average
23.8
23.6
23.5
23.3
23.2
23.1
23.2
23.9
24.5
24.8
25.0
25.2
25.3
25.4
25.3
25.2
25.0
24.8
24.7
24.5
24.4
24.2
24.1
23.9
Minimum
21.9
21.5
21.3
20.9
20.7
20.1
19.9
21.1
21.9
22.3
22.1
22.6
22.2
22.5
22.4
22.4
22.4
21.9
22.6
22.2
22.1
22.0
21.9
22.0
Maximum
26.0
25.8
25.4
25.4
25.2
25.0
25.2
25.9
26.5
26.9
26.9
27.2
27.4
28.4
27.8
27.8
27.5
27.3
26.9
26.7
26.3
26.4
26.3
26.0
Std Dev.
0.7
0.7
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.9
0.9
0.8
0.9
1.0
1.0
1.0
0.9
0.9
0.8
0.8
0.8
0.8
0.7
0.8
http://www.wescorhvac.com/Evaporative%20cooling%20white%20paper.htm
Minimum
Maximum
24
22
20
18
16
14
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
3:00:00 AM
6:00:00 AM
12
12:00:00 AM
DESIGN POTENTIAL
The humidity ratio gives us information
about how much water is in one kilogram
of air; therefore, it gives a potential water
quantity that can be squeezed out from the
air. The following known methodologies for
squeezing water out from the air are:
g/kg
40%
36.2%
35%
% of Hours in a Year
30%
25.4%
25%
20.0%
20%
15%
9.1%
10%
5.0%
5%
0%
0.0%
0.0%
0.2%
0.8%
<12
12 - 13
13 - 14
14 - 15
2.6%
15 - 16
16 - 17
17 - 18
18 - 19
19 - 20
20 - 21
0.7%
0.1%
0.0%
0.0%
21 - 22
22 - 23
23 - 24
>24
Average
18.4
18.2
18.1
17.9
17.8
17.7
17.8
18.3
18.3
18.1
17.9
17.9
17.9
18.0
18.2
18.4
18.4
18.6
18.8
18.8
18.8
18.7
18.7
18.5
Minimum
15.0
14.6
14.8
15.3
15.0
14.4
14.2
14.8
15.1
13.8
13.7
13.5
13.2
13.0
13.2
13.9
14.4
15.1
15.1
14.9
15.0
15.1
15.0
15.1
Maximum
21.3
20.8
20.5
20.5
20.3
20.0
20.0
20.7
21.1
21.0
20.7
21.0
21.2
23.7
21.6
22.2
22.6
22.6
21.7
21.7
21.4
21.2
21.2
20.9
Std Dev.
0.9
0.9
0.9
0.9
0.9
0.9
0.9
1.0
1.1
1.2
1.3
1.3
1.4
1.6
1.5
1.5
1.3
1.2
1.1
1.0
1.0
0.9
0.9
0.9
Minimum
Maximum
29
27
25
Degree Celcius
23
21
19
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
6:00:00 AM
3:00:00 AM
17
12:00:00 AM
45%
41.0%
DESIGN RISK
If there are water features, greenery and
cooking done (evaporation of water) within
the space, the moisture content in the air
may increase and cause the dew point
temperature to increase as well. Therefore,
condensation may occur at a higher surface
temperature due to these micro-climatic
conditions.
35%
% of Hours in a Year
DESIGN POTENTIAL
The dew point temperature provides an
indication when condensation will occur.
As long as the surface temperature is kept
above the dew point temperature, there
will be no condensation. For example, if a
surface temperature exposed to outdoor air
is kept above 25C, the risk of condensation
is less than 5% and above 26C, the risk of
condensation is less than 0.5%. This provides
a possibility to provide radiant cooling to an
outdoor area (e.g. al-fresco dinning, etc.)
where the surface temperature can be kept
above the dew point temperature to avoid
condensation while minimising energy
consumption to cool occupants in an outdoor
space.
40%
30%
25%
22.7%
22.5%
20%
15%
10%
7.0%
4.0%
5%
0%
0.0%
0.0%
0.1%
0.5%
<17
17 - 18
18 - 19
19 - 20
1.9%
20 - 21
21 - 22
22 - 23
23 - 24
24 -25
25 - 26
0.3%
0.0%
0.0%
26 - 27
27 - 28
>28
Average
23.5
23.4
23.2
23.1
23.0
22.9
22.9
23.4
23.4
23.2
23.0
23.0
23.0
23.1
23.3
23.4
23.5
23.7
23.8
23.9
23.9
23.8
23.7
23.6
Minimum
20.3
19.8
20.1
20.6
20.3
19.6
19.4
20.1
20.4
19.0
18.8
18.6
18.3
18.0
18.3
19.1
19.6
20.4
20.4
20.2
20.3
20.4
20.3
20.4
Maximum
25.9
25.5
25.3
25.3
25.1
24.9
24.9
25.4
25.7
25.7
25.4
25.7
25.8
27.7
26.1
26.6
26.9
26.9
26.2
26.2
26.0
25.8
25.8
25.6
Std Dev.
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
1.0
1.1
1.2
1.2
1.3
1.5
1.4
1.4
1.2
1.0
0.9
0.9
0.8
0.8
0.8
0.8
RELATIVE HUMIDITY
CHART 2.6 | RELATIVE HUMIDITY
Average
Minimum
Maximum
105%
100%
95%
90%
85%
Percentage (%)
80%
75%
70%
65%
60%
55%
50%
45%
40%
DESIGN POTENTIAL
A low relative humidity is an indication of
how well evaporative cooling will work. The
lower the relative humidity, the easier it is for
water to evaporate to reduce the dry bulb air
temperature. At a very high relative humidity
level of 90% or more, only a very small amount
of water will be able to evaporate.
DESIGN RISK
Relative humidity is a factor of both the dry
bulb temperature and moisture content. It is
not possible to compute energy changes when
provided with the relative humidity alone.
For example, how much energy will it take to
reduce the relative humidity of 90% to 50%?
It would not be possible to give an answer to
such a question. However, it will be possible to
compute the energy change if the question is
rephrased into how much energy will it take to
reduce the relative humidity of 90% at 25C
to a relative humidity of 50% at 23C. Relative
humidity is useful as an indicator of moisture
in the air only when provided with the dry bulb
temperature.
Average
93.9
94.5
94.8
95.1
95.4
95.4
95.0
89.9
79.6
71.6
66.2
63.6
62.0
62.7
66.0
70.0
73.6
78.3
83.7
87.2
89.6
91.2
92.6
93.3
Minimum
73
72
75
81
84
85
82
75
62
50
47
44
42
40
40
40
47
51
58
62
69
73
72
73
Maximum
100
100
100
100
100
100
100
100
98
96
97
95
99
97
97
97
98
99
98
98
99
98
99
100
Std Dev.
3.7
3.5
3.2
3.1
2.8
2.8
2.9
4.2
7.0
7.8
7.9
8.3
8.9
10.7
12.0
13.0
12.3
10.7
8.6
6.8
5.5
4.8
4.2
4.0
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
6:00:00 AM
3:00:00 AM
12:00:00 AM
35%
Minimum
Maximum
1200
1000
Watt/m2
800
600
400
200
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
6:00:00 AM
3:00:00 AM
12:00:00 AM
Hours
1:00:00 AM
2:00:00 AM
3:00:00 AM
4:00:00 AM
5:00:00 AM
6:00:00 AM
7:00:00 AM
8:00:00 AM
9:00:00 AM
10:00:00 AM
11:00:00 AM
12:00:00 PM
1:00:00 PM
2:00:00 PM
3:00:00 PM
4:00:00 PM
5:00:00 PM
6:00:00 PM
7:00:00 PM
8:00:00 PM
9:00:00 PM
10:00:00 PM
11:00:00 PM
12:00:00 AM
Average
0.0
0.0
0.0
0.0
0.0
0.0
7.7
87.5
253.6
429.0
565.7
631.0
635.9
589.2
474.6
335.2
205.7
93.2
20.0
0.7
0.0
0.0
0.0
0.0
Minimum
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
38.9
120.8
161.1
36.1
23.7
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Maximum
0.0
0.0
0.0
0.0
0.0
0.0
29.2
259.1
516.2
692.8
844.3
1006.4
1003.7
1076.5
958.0
759.7
532.7
254.1
67.7
11.1
0.0
0.0
0.0
0.0
Std Dev.
0.0
0.0
0.0
0.0
0.0
0.0
5.7
42.4
90.7
125.4
143.2
161.3
173.8
186.7
189.3
169.7
122.8
62.4
16.7
1.7
0.0
0.0
0.0
0.0
Maximum
500
450
350
300
250
200
150
100
50
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
6:00:00 AM
3:00:00 AM
0
12:00:00 AM
Watt/m2
400
Hours
1:00:00 AM
2:00:00 AM
3:00:00 AM
4:00:00 AM
5:00:00 AM
6:00:00 AM
7:00:00 AM
8:00:00 AM
9:00:00 AM
10:00:00 AM
11:00:00 AM
12:00:00 PM
1:00:00 PM
2:00:00 PM
3:00:00 PM
4:00:00 PM
5:00:00 PM
6:00:00 PM
7:00:00 PM
8:00:00 PM
9:00:00 PM
10:00:00 PM
11:00:00 PM
12:00:00 AM
Average
0.0
0.0
0.0
0.0
0.0
0.0
7.7
62.8
153.8
231.4
290.4
334.4
356.2
344.1
298.4
228.1
152.3
76.1
18.8
0.7
0.0
0.0
0.0
0.0
Minimum
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
38.7
119.7
158.9
36.0
23.6
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Maximum
0.0
0.0
0.0
0.0
0.0
0.0
29.2
116.1
227.1
316.2
386.1
434.0
459.7
453.3
415.9
350.1
272.5
163.3
57.1
11.1
0.0
0.0
0.0
0.0
Std Dev.
0.0
0.0
0.0
0.0
0.0
0.0
5.7
20.7
38.8
50.8
58.0
62.9
62.5
69.8
78.8
80.4
69.8
41.4
14.6
1.7
0.0
0.0
0.0
0.0
Maximum
900
800
700
600
500
400
300
200
100
Average
0.0
0.0
0.0
0.0
0.0
0.0
0.0
24.7
99.8
197.6
275.2
296.7
279.7
245.1
176.2
107.0
53.4
17.2
1.2
0.0
0.0
0.0
0.0
0.0
Minimum
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.2
1.2
2.3
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Maximum
0.0
0.0
0.0
0.0
0.0
0.0
0.0
203.2
433.1
572.2
677.7
840.6
821.7
864.5
792.2
621.7
401.0
160.8
30.6
0.0
0.0
0.0
0.0
0.0
Std Dev.
0.0
0.0
0.0
0.0
0.0
0.0
0.0
38.2
97.1
146.1
171.1
190.6
193.0
194.2
169.6
125.4
76.0
31.4
4.0
0.0
0.0
0.0
0.0
0.0
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
6:00:00 AM
0
3:00:00 AM
Average
1000
12:00:00 AM
Watt/m2
DESIGN RISK
The direct and diffuse radiation in the TRY is not a
measured value but computed from the measured
horizontal global radiation using the Erbs Estimation
Model. However, the result generally agrees with the
daily observation of solar radiation in this climate. In the
tropical climate where it rains more often in the afternoon
than in the morning creates skies with a heavier average
cloud cover in the afternoon than in the morning.
Direct
Diffuse
700
600
400
300
200
100
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
6:00:00 AM
3:00:00 AM
0
12:00:00 AM
Watt/m2
500
Category
Sky clear
Fine
Fine
Fine
Partly Cloudy
Partly Cloudy
Partly Cloudy
Cloudy
Cloudy
DESIGN POTENTIAL
High Oktas numbers indicate heavy cloud cover in
Malaysias climate. It also means that during the daytime,
the Malaysian sky is normally bright because the sky will
be illuminated by the clouds as opposed to clear blue skies.
Heavy cloud cover also hinders radiation heat transfer
between objects on the ground with the sky. In general the
lower the Oktas number, the better it is for the sky to cool
objects on the ground surface.
Overcast
DESIGN RISK
Oktas measurements are done manually by meteorologists.
They would take a look at the sky and decide how many
eighths of the sky is covered by clouds.
Minimum
Maximum
8
7
Oktas
6
5
4
3
2
1
http://worldweather.wmo.int/oktas.htm
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
6:00:00 AM
3:00:00 AM
12:00:00 AM
Hours
1:00:00 AM
2:00:00 AM
3:00:00 AM
4:00:00 AM
5:00:00 AM
6:00:00 AM
7:00:00 AM
8:00:00 AM
9:00:00 AM
10:00:00 AM
11:00:00 AM
12:00:00 PM
1:00:00 PM
2:00:00 PM
3:00:00 PM
4:00:00 PM
5:00:00 PM
6:00:00 PM
7:00:00 PM
8:00:00 PM
9:00:00 PM
10:00:00 PM
11:00:00 PM
12:00:00 AM
Average
6.8
6.8
6.8
6.8
6.8
6.9
6.9
6.8
6.7
6.7
6.8
6.8
6.9
6.9
6.9
6.9
6.9
7.0
7.0
6.9
6.9
6.8
6.8
6.9
Minimum
4.0
3.0
4.0
4.0
4.0
0.0
0.0
4.0
4.0
4.0
4.0
4.0
4.0
4.0
5.0
5.0
5.0
5.0
5.0
5.0
4.0
4.0
4.0
4.0
Maximum
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
8.0
Std Dev.
0.5
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.7
0.7
0.6
0.5
0.4
0.4
0.4
0.4
0.5
0.4
0.4
0.5
0.5
0.6
0.6
0.5
A roof system that can block heat gain during the daytime
and release heat during the night time will potentially be
an effective means of cooling a building. Buildings that
are mainly used during the night time such as residential
homes will benefit significantly from such a roof design.
Movable roof insulation, cool roof paints that reject solar
radiation during the daytime while having high emissivity
to release heat, etc. may be interesting solutions for
residential homes.
DESIGN RISK
An average effective sky temperature above 20C during
the daytime is not considered to be sufficient to cool
objects on the ground. Therefore, using the sky to cool
objects on the ground will only be useful during the night
time when the effective sky temperature reduces below
20C. In countries where the cloud cover is low and the
ambient air temperature is moderate, it is possible for
the sky to provide a consistent effective sky temperature
below 10C (in some places, even below 0C, making it
possible to make ice in the night sky6). The high effective
sky temperature found in this climate is largely due to the
high moisture content in the air and the heavy cloud cover.
Maximum
30
Degree Celcius
25
20
15
10
5
6
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
6:00:00 AM
3:00:00 AM
12:00:00 AM
Hours
1:00:00 AM
2:00:00 AM
3:00:00 AM
4:00:00 AM
5:00:00 AM
6:00:00 AM
7:00:00 AM
8:00:00 AM
9:00:00 AM
10:00:00 AM
11:00:00 AM
12:00:00 PM
1:00:00 PM
2:00:00 PM
3:00:00 PM
4:00:00 PM
5:00:00 PM
6:00:00 PM
7:00:00 PM
8:00:00 PM
9:00:00 PM
10:00:00 PM
11:00:00 PM
12:00:00 AM
Average
16.20
15.89
15.55
15.24
14.98
14.74
14.56
14.75
16.43
18.51
19.97
20.93
21.66
22.10
22.17
21.72
20.94
20.12
19.33
18.42
17.78
17.31
16.89
16.53
Minimum
12.7
12.7
11.7
11.5
10.9
10.4
9.6
9.5
11.6
12.9
14.6
15.1
15.0
12.7
15.0
13.9
13.6
13.9
13.2
14.2
13.7
13.3
13.4
13.2
Maximum
20.1
19.5
19.2
18.8
18.5
18.1
17.9
18.4
20.3
22.3
23.9
24.4
25.4
26.0
26.6
26.7
26.7
25.1
24.1
22.2
22.0
21.4
21.3
20.7
Std Dev.
1.3
1.3
1.3
1.3
1.4
1.4
1.4
1.4
1.5
1.7
1.7
1.7
1.8
1.9
2.1
2.4
2.5
2.4
2.1
1.8
1.7
1.5
1.4
1.3
Gene Clark and M. Blanpied, 1979. The Effect of IR Transparent Windscreens on Net Nocturnal Cooling from Horizontal Surfaces, Proceedings of the 4th National Passive Solar Conference, Kansas City, MO.
Lesson 1: History of Refrigeration, Version 1 ME. Indian Institute of Technology Kharagpur. Archived from the original on 2011-11-06.
GROUND TEMPERATURE
The ground temperature was computed
from the TRY using Kasudas equation7 at
a 1 meter depth. It was computed that the
soil temperature is constant at 26.9C for
the entire year. Further investigation using
Kasudas equation showed that at any
depth greater than 0.5 meters, the ground
temperature will be constant at 26.9C.
It is also important to note that the
groundwater temperature will also be the
same temperature as the ground (soil)
temperature.
DESIGN POTENTIAL
There exists designs that channel air intake
into a building through an underground
chamber to pre-cool the air before entering
the building. However, this strategy will only
work well in this climate during the daytime
when the outdoor air temperature is higher
than the soil temperature. During the night
time, the outdoor air temperature is lower
than the soil temperature, so channelling night
air into the underground chamber will heat up
the air instead of cooling it down. In short, this
strategy will work well with office buildings
where the building is occupied during daytime;
it will not work well for residential homes
because the homes are normally occupied
during the night time.
DESIGN RISK
Kasudas equation does not account for
rainfall on the soil. As water from the soil will
evaporate at the wet bulb temperature, the
surface of the soil may be cooler on average
for a climate such as Malaysias where it
rains fairly often and consistently throughout
the year. The effect of rainfall on the ground
temperature is expected to be minimal.
However, actual measurement of the on-site
ground temperature is highly recommended.
In addition, further studies are recommended
to ensure that the cooler daytime air achieved
via an underground chamber can be achieved
without increasing the moisture content of
the air. An increase in moisture content will
increase the energy consumption of the airconditioning system.
Excessive groundwater harvesting without
adequate recharge will cause soil properties to
deteriorate and may cause the ground to sink.
Moreover, pumping water over long distances
will also increase the water temperature due
to friction and conduction gain through the
pipes, which may cause the predicted 3C
cooler water temperature to be unachievable.
Kasuda, T., and Archenbach, P.R. 1965. Earth Temperature and Thermal Diffusivity at Selected Stations in the United States, ASHRAE Transactions, Vol. 71, Part 1.
WIND SPEED
DESIGN RISK
The wind speed and wind direction data
should be checked further against other years
data to ensure that the data in the TRY is
reflective of the actual situation. The selected
months of the TRY data was predominantly
selected based on the dry bulb temperature,
global horizontal solar radiation and humidity
ratio. Therefore, it is recommended for
academicians and researchers to investigate
the wind data further to confirm the behaviour
of wind speed and wind direction according to
the hour of the day and day of the year.
Average
Minimum
Maximum
9
8
7
6
5
4
3
2
1
12:00:00 AM
9:00:00 PM
6:00:00 PM
3:00:00 PM
12:00:00 PM
9:00:00 AM
6:00:00 AM
3:00:00 AM
0
12:00:00 AM
DESIGN POTENTIAL
It is important to note that the peak average
wind speed occurs at the same time of high
dry bulb temperature. Similarly, when the dry
bulb temperature is low, the average wind
speed is also low. This indicates that buildings
designed with cross-ventilation at all hours will
on average bring more hot air than cool air into
the building. As the wind speed data showed
that high wind speeds can occur at any time,
it is also possible for cross ventilation to bring
in cool air to benefit the building occupants.
Therefore, cross-ventilation designs need to
consider the hours occupants make use of
the space and also the possibility of diverting
hot wind away from occupants during
certain hours/conditions of the day and to
divert cool air towards the occupants during
certain hours/conditions of the day. Operable
windows, where the building occupant has
control over when cross ventilation is used is
highly recommended.
meter/second
Average
0.44
0.46
0.45
0.48
0.48
0.47
0.54
0.85
1.44
2.15
2.46
2.77
3.05
3.36
3.50
3.30
2.58
1.69
0.94
0.56
0.47
0.43
0.38
0.46
Minimum
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Maximum
6.4
5.4
7.0
6.0
7.0
7.6
5.3
4.1
5.0
6.5
6.9
7.0
6.6
7.1
7.0
7.0
5.8
7.0
5.4
5.3
5.6
4.7
7.2
5.2
Std Dev.
0.9
0.9
0.9
1.0
1.0
0.9
0.9
1.0
1.2
1.4
1.4
1.4
1.4
1.5
1.5
1.5
1.5
1.3
1.0
0.8
0.8
0.8
0.8
0.9
DESIGN POTENTIAL
Capturing wind from the North and
North-West should be the primary
objective to use natural ventilation
to cool the environment. Cool
wind is primary available from the
hours of 5pm to 9am. When the air
temperature is high during noon, it will
not be comfortable to harvest natural
ventilation. Ideally the building
occupants should have control over
the natural ventilation by giving the
building occupants the ability to close
windows or doors, to divert the wind
away from the occupied space when
the wind is hot and to allow wind
towards the occupied space when
the wind is cool. Motorised louvres
with temperature sensors may also
be used to provide this diversion of
natural ventilation without requiring
manual intervention.
DESIGN RISK
The wind speed and wind direction
data should be checked further
against other years data to
ensure that the data in the TRY is
reflective of the actual situation.
The selected months of the TRY
data was predominantly selected
based on the dry bulb temperature,
global horizontal solar radiation
and humidity ratio. Therefore, it is
recommended for academicians and
researchers to investigate the wind
data further to confirm the behaviour
of wind speed and wind direction
according to the hour of the day and
day of the year.
North
1200
1000
North-West
North-East
800
600
400
200
West
East
South-West
ASHRAE 55
South-East
South
All Temperatures
<29C
70
60
50
40
30
20
10
0
NORTH WIND
Freq Hours
Freq Hours
NORTH-WEST WIND
70
60
50
40
30
20
10
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hours
Hours
Freq Hours
EAST WIND
70
60
50
40
30
20
10
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hours
Hours
SOUTH-EAST WIND
SOUTH WIND
70
60
50
40
30
20
10
0
Freq Hours
Freq Hours
Freq Hours
NORTH-EAST WIND
70
60
50
40
30
20
10
0
70
60
50
40
30
20
10
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hours
Hours
70
60
50
40
30
20
10
0
WEST WIND
Freq Hours
Freq Hours
SOUTH-WEST WIND
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hours
70
60
50
40
30
20
10
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hours
SUMMARY
A clear understanding of our local weather data will enable architects and engineers to
become better building designers. Fortunately, the Malaysian climate zone is easy to
comprehend because the seasonal variation is rather small, i.e. every day is more or less
the same for the whole year.
An attempt is made in this chapter to clarify the Malaysian climate on its dry bulb
temperature, wet bulb temperature, dew point temperature, moisture content,
relative humidity, effective sky temperature, ground temperature, solar radiation and
the relationship of wind speed and direction to the air temperature based on the Test
Reference Year weather data. An attempt is also made to provide the Design Potential
based on each of these climatic properties presented, providing the possibility of design
options to harness the climate to benefit the building design for low energy consumption.
There may also be situations where the localised micro-climatic conditions may alter the
design possibilities presented by the Test Reference Year weather data. The Design Risk
is therefore provided for each climatic property presented, allowing building designers to
understand the risk of implementing the design options presented in this chapter.
Building designers are encouraged to make use of the data provided in this chapter to
innovate building designs to benefit from the climate. Ideally, buildings in Malaysia should
benefit from night cooling from the sky, taking advantage of the cooler night time air
temperatures while preventing heat gain during the daytime from solar radiation, warm air
temperatures and high moisture content. The challenge to the building designer is to strike
the right balance between all these various climatic conditions to provide a comfortable
environment for the building occupants while minimising carbon-based energy use.
It is also proposed that the data provided in this chapter be used as a fundamental check
against any new design ideas proposed by designers, suppliers and manufacturers that may
not understand the Malaysian climate well enough. For example, an evaporative cooling
system that seems to work very well in an air-conditioned exhibition hall/showroom
where the air is both cool and dry, will not be effective if used outdoors during the night
time because the relative humidity is very high during the night time in this climate zone,
but it is still possible to use it during the daytime because the relative humidity is lower
during the daytime in this climate zone.
END OF CHAPTER 2
CHAPTER
ENERGY RATING
OF ELECTRICAL
APPLIANCES
ENERGY RATING
OF ELECTRICAL
APPLIANCES
INTRODUCTION
The use of electrical appliances (such as computers,
printers, refrigerators, hot/cold water dispensers,
etc.) in buildings in the Malaysian zone has a
negative impact on energy efficiency. The electrical
energy used by these appliances ends up as heat
within the space where the appliance is, heating
up the environment. The 1st law of thermodynamics
states the law of conservation of energy, that the
total amount of electrical energy used will eventually
end up as heat energy in the building. Since heat is
hardly ever desirable in the Malaysian climate, it is
necessary to minimise the use of energy by electrical
appliances by selecting those that can perform the
same task using a minimum amount of electricity.
There are many products in the market that claim to
be energy efficient. Purchasers are easily confused
by these claims and many have reservations on the
validity of these efficiency claims. Therefore, as an
aid to the consumers, it is necessary to have an
authoritative, independent and publicly accepted
green (eco) label or energy efficiency scheme that
identifies products with the same functions in the
market (Green Label Scheme, Green Council, 2013).
The use of electrical appliances in office buildings
is normally known as plug load or small power.
Plug load has become one of the fastest growing
sources of energy demand in commercial buildings
due to the heavy reliance on computers as opposed
to the typewriter many years ago. In Malaysian
If energy efficient
equipment is used, it
is possible to reduce
the cooling load
which in turn reduces
the cost of the airconditioning system
and the running cost
of the building
Energy Efficiency Guide For Industry In Asia, About Energy Efficiency, United Nations Environment Programme 2006
$88
$144
$24
$40
$216
$352
http://www.energystar.gov/index.cfm?fuseaction=find_a_product.showProductGroup&pgw_code=CO
Extra information
pertaining to the
appliance such
as noise level and
water consumption
is given to provide
consumers with
more information
to make a more
informed choice.
http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31992L0075:EN:NOT
This gives an
indication of how
much energy is used
in Kilowatt hour
under normal usage.
In accordance with the EU Directive2010/30/EU, this label must be attached clearly onto the front of
the appliance while on sale. The scale ranges from A+++ (Dark green) to G (Red) where the former is
most efficient and the latter is least. These rankings are based on the Energy Efficiency Index (EEI) and
the limits for each class differs based on categories.
The importance of this scale is twofold. Firstly, by ranging the scale from A+++, the EU commission hopes
to spur manufacturers to produce goods that are much more energy efficient than currently available
and provide better differentiation for consumers. Secondly, this complements Ecodesign regulations
that prohibits products below a certain ranking from entering the EU market. For instance, in 2013, only
washing machines with a rank A and above were allowed to enter.4
There are significant differences between the EU Energy Efficiency Label and Energy Star although both
are a means of demonstrating energy efficiency.
Table 3.2 | Comparison between the eu energy efficiency label and energy star
EU Energy Efficiency Label
Energy Star
Governing Body
European Commission
Yes
No
Voluntary?
No
Yes
Adopting Countries
EU nations
As listed
Appliances
It is obvious that a product with a higher rating has greater energy efficiency as measured by the Energy
Efficiency Index. This translates to savings on the electricity bill as less energy is required to do the same
amount of work.
Further information on EU rated equipment can be found at the following websites:
http://ec.europa.eu/energy/efficiency/labelling/labelling_en.htm
http://en.wikipedia.org/wiki/European_Union_energy_label
http://europa.eu/legislation_summaries/other/l32004_en.htm
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/69295/pb13466-eu-energy-label.pdf
http://www.energyagency.at/fileadmin/dam/pdf/publikationen/berichteBroschueren/comeonlabels_vergleich.pdf
1.05
1.00
0.95
0.90
0.85
0.80
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
FEATURE
AIR CONDITIONER
REFRIGERATOR
CLOTHES DRYER
1 Ticks
2 Energy
Efficiency Rating
3 Energy
Consumption
Energy consumption
over 24 hours x 365
days expressed in kWh.
4 Capacity
Rated capacity
expressed in kilograms
(Kg) and rounded to one
decimal place.
5 Type
Type of air-conditioners:
Casement
Window
Single Split (non-inverter/
inverter)
Multi split system (noninverter/inverter)
Type of refrigerators:
Refrigerator
Refrigerator Freezer
6 Brand Name
Brand of air-conditioner
Brand of refrigerator
7 Model
Number
8 Test Standard
9 Disclaimer
!0 Registration
Number
A unique number found on the registered models COR, which is issued by NEA upon
successful registration of the model.
PENGGUNAAN TENAGA
ENERGY CONSUMPTION
Peti Sejuk
Refrigerator
Model information
Penggunaan Tenaga Purata Setahun
Average Energy Consumption Per Year
Energy consumption
(in kWh/year)
662
kWh/
year
www.st.gov.my
Eligibility
Air-conditioner (RM100/unit)
Quantity: 65,000 units
Chiller (RM200/RT)
Quantity: 72,000 RT
All Malaysian domestic users registered with SESB or SESCO in Sabah, Labuan and
Sarawak
ENERGY EFFICIENCY OF
OFFICE EQUIPMENT
Office equipment such as computers, printers and copiers can generate high heat gains in a building. Unfortunately,
the actual power consumption is rarely reflected on the nameplate of office equipment. 5 In general, office equipment
with a nameplate power rating up to 480W has been found to consume less than 100W during use. The actual
proportion of the total heat gain to the stated nameplate ranges from 25% to 50%. This could lead to an oversizing
of the cooling load if the nameplate power is used at the design stage. The actual power consumption of each offices
equipment should be evaluated based on the type and model of equipment as it can vary, as well as the operating
hours, taking into account the sleep/standby mode.
For instance, desktop computers power consumption in operation could vary from about 50W to 100W. Table 3.4
below, reproduced from the 2009 ASHRAE Handbook, presents typical computer power consumption values versus
the nameplate values. It shows that the actual power consumption of office equipment only is about 10% to 15% of
the nameplate value.
TABLE 3.4 | NAMEPLATE VERSUS MEASURED ENERGY USE FROM TYPICAL COMPUTER EQUIPMENT (2009
ASHRAE Handbook - Fundamentals, Table 8)
Equipment
Desktop Computer
Nameplate Power
Consumption (W)
Average Power
Consumption (W)
480
73
480
49
690
77
690
48
1200
97
130
36
90
23
90
31
90
29
70
22
50
12
383
90
360
36
288
28
240
27
240
29
240
19
Description
Laptop Computer
Flat-Panel Monitor
TABLE 3.5 | NAMEPLATE VERSUS MEASURED ENERGY USE FROM TYPICAL LASER PRINTERS & COPIERS (2009
ASHRAE Handbook - Fundamentals, Table 9)
Equipment
Multifunction (copy,
print, scan)
Scanner
Copy Machine
Nameplate Power
Consumption (W)
Average Power
Consumption (W)
430
137
890
74
508
88
508
98
635
110
1,344
130
600
30
40
15
700
135
19
16
1,750
1,440
1,850
Medium
936
90
Small
40
20
Manufacturer A
400
250
Manufacturer B
456
140
Description
Fax Machine
Plotter
The energy consumption of personal laser printers in offices varies between 75W to 140W, and the average power
consumption of 110W is recommended to be used. Power consumption for the large photocopy/printer machines ranges
from about 550W to 1,100W in copy mode while the idle mode varies from 130W to 300W. Nameplate values do not
represent actual power consumption and hence it should not be used to estimate energy consumption in buildings.
Table 3.6 below compares energy star rated printers to those that are not energy star rated.
Table 3.6 | Compiled data from various manufacturing websites about energy
consumption of printers
Energy
Star
PPM
(Pages Per Minute)
Ready Power
Consumption (Avg.)
Printing Power
Consumption (Avg.)
Yes
16
8W
295W
Yes
33
7.3W
570W
Canon LBP6000
No
19
1.6W
850W
Samsung ML-2165W
No
21
<30W
<310W
Printer
Based on Table 3.6 above, it can be concluded that for printers in the same category, printers with the Energy Star
rating consume less power in Ready and print mode.
Type
Basic Specifications
Desktop
Apple iMac/Intel
27-inch
(purchased late 2009)
Desktop
Desktop
104 - 162
Dell XPS 12
Notebook
38 - 40
Notebook
49 - 53
Notebook
55 - 58
66
92 - 96
From Table 3.7, it is interesting to note that desktop systems have a higher power consumption than notebooks.
This is because most manufacturers have focused on designing mobile devices such as notebooks with low power
consumption to increase battery life. By using notebooks in the office rather than desktop systems, employees
are able to get basic word processing, spread sheets and other rudimentary functions achieved with lower power
consumption. The drawback is that notebooks generally lack processing power compared to desktops which
would be unsuitable for offices which require such processing power such as visual designers and video editors.
It is also important to note that newer computer systems are getting more energy efficient. The newer
motherboards and CPUs are more energy efficient due to newer manufacturing processes. Intel Core i7 and
Haswell chips are known to be very energy efficient. In addition, todays computer operating systems have
very good energy management software built-in. Energy management software, when activated, will put the
computer to sleep, hibernation or shut down automatically when the computer is not in use for a set amount of
time. By investing into newer technologies, companies will benefit from energy savings in the long run.
http://www.upenn.edu/computing/provider/docs/hardware/powerusage.html
SUMMARY
Energy labelled equipment has an advantage by giving consumers greater
awareness about the energy requirements of the product and give a clear
indication of its energy efficiency, allowing consumers to make an informed
choice. Both the European Union Commission and the Environmental
Protection Agency have set stringent standards for appliances to be given
their respective ratings which far surpass conventional standards. By favouring
energy labelled equipment, a consumer is assured that the product has been
tested and proven to be energy efficient. This also leads to energy savings in
the long term which offsets short term losses in terms of higher initial price
points, and at the same time also reduces CO2 emissions that cause global
temperatures to rise.
Aside from taking the green procurement route, many buildings can benefit
from the easiest fix, which is to Switch Things Off and Turn Things Down.
REFERENCES
1. Energy Efficiency Policies around the World: Review and Evaluation, Executive Summary World Energy Council 2008, retrieved on the 22nd of
April 2013, online from http://89.206.150.89/documents/energy_efficiency_es_final_online.pdf
2. Energy Efficiency Statistical Summary, Department of Energy and Climate Change, November 2012, retrieved on the 22nd of April 2013, online
from https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/65598/6918-energy-efficiency-strategy-statisticalsummary.pdf
3. The Potential of Energy Efficiency, An Overview, The Bridge, Linking Engineering and Society, L. B. Lave, Improving Energy Efficiency in the
Chemical Industry, J. J. Patt and W. F. Banholzer, Energy Efficiency in Passenger Transportation, D. Sperling and N. Lutsey, Building Materials,
Energy Efficiency, and the American Recovery and Reinvestment Act, R. Roy and B. Tiniaov, Coming of Age in New York: The Maturation of Energy
Efficiency a China, M. D. Levine, N. Zhou, and L. Price, National Academy of Engineering of the National Academies, Vol. 39, No. 2, Summer 2009,
retrieved on the 22nd of April 2013, online from http://www.nae.edu/File.aspx?id=14867
4. Energy Efficiency Guide for Industry In Asia, About Energy Efficiency, United Nations Environment Programme 2006, retrieved on the 22nd of
April 2013, online from http://www.energyefficiencyasia.org/aboutee.html
5. Singapore Air Con: Energy Labelling Scheme, 2007, retrieved on the 25th of April 2013, online from http://singapore-aircon-label.blogspot.com/
6. E2 Singapore, The Energy Efficiency Revolution, retrieved on the 25th of April 2013, online from http://www.nea.gov.sg/cms/ccird/E2%20
Singapore%20(for%20upload).pdf
7. National Climate Control Committee, 2013, retrieved on the 25th of April 2013, online from http://www.nccc.gov.sg/
8. Energy Efficiency Policy in the United States: Overview of Trends at Different Levels of Government, National Renewable Energy Laboratory,
Innovation for Our Energy Future, December 2009, E. Doris, J. Cochran, and M. Vorum, retrieved on the 25th of April 2013, online from http://
www.nrel.gov/docs/fy10osti/46532.pdf
9. Energy labels explained, Which? works for you, 2013, retrieved on the 25th of April 2013, online from http://www.which.co.uk/energy/savingmoney/guides/energy-labels-explained/eu-energy-efficiency-labels/
10. Malaysia Launches Green Labelling Scheme, Green Prospects 2012, retrieved on the 19th of April 2013, online from http://www.
greenprospectsasia.com/content/malaysia-launches-green-labelling-scheme
11. Conserve Energy and Reduce Costs, Save Energy Save Money, Ministry of Energy, Green Technology and Water, 2013, retrieved on the 25th of
April 2013, online from http://www.saveenergy.gov.my/conserve-energy-and-reduce-costs
12. Peer Review on Energy Efficiency in Malaysia, Asia-Pacific Economic Cooperation (APEC), Report for the APEC Energy Working Group, 11-12 May
2011, retrieved on the 26th of April 2013, online from http://www.ewg.apec.org/documents/9b_Malaysia%20PREE%20Report_Final%20
Draft.pdf
13. RM50M Triggers Energy Efficient Habit, Rakyat empowered to be more energy efficient, retrieved on the 25th of April 2013, online from http://
peterchin.my/wp-content/uploads/2011/07/PRESS-RELEASE-RM50M-TRIGGERS-ENERGY-EFFICIENT-HABIT.pdf
14. SAVE Rebate Programme, Tenaga Nasional Berhad, 2013, retrieved on the 25th of April 2013, online from http://www.tnb.com.my/residential/
discounts-rebates-and-offers/save-rebate-program.html
15. Smart Grid, A smarter Planet, IBM, 2013, retrieved on the 26th of April 2013, online from http://www.ibm.com/smarterplanet/my/en/smart_
grid/ideas/
16. Energy and associated greenhouse gas emissions from household appliances in Malaysia, R. Saidur, H. H. Masjuki, M. Y. Jamaluddin, S. Ahmed,
2006, retrieved on the 26th of April 2013, online from http://www.sciencedirect.com/science/article/pii/S0301421506002047
17. 2009 ASHRAE handbook Fundamentals
END OF CHAPTER 3
CHAPTER
4
EFFICIENT LIGHTING
DESIGN STRATEGIES
EFFICIENT LIGHTING
DESIGN STRATEGIES
INTRODUCTION
There is a very common misconception in the
Malaysian building industry (even amongst
engineers) that only a portion of electricity
consumed by the lights ends up as heat in a room.
It is also common for Malaysian air-conditioning
engineers to use a higher lighting power density
to size the air-conditioning load than as actually
installed in the building. Such an assumption seems
to say that electrical lighting would produce more
heat energy than the electrical energy consumed
by it. Unfortunately both of these assumptions are
fundamentally incorrect.
The 1st law of thermodynamics says that energy
cannot be created or destroyed; therefore 100%
of electricity used by the lighting appliance will
become heat in the room where the electrical
energy is consumed. Since the first explicit
statement of the 1st law of thermodynamics in the
1850s by Rudolf Clausius, it has never been proven
wrong until today. Even the findings of Higgs Bosons
(nicknamed the god particle, smallest particle
ever discovered) and the entire universe of galaxies
and planetary systems does not violate the 1st law
of thermodynamics. Therefore, please have faith
in the 1st law of thermodynamics and do not invent
new theories or make assumptions that go against
Lighting terminologies
Lighting technologies
Lighting controls, and
Current energy efficiency
status of LED
lighting systems
KEY RECOMMENDATIONS
There are just two (2) rules in the design of an energy efficient lighting system that will lead to
efficient lighting in a building:
1. Ensure installed lighting power density (W/m2) is as low as possible while providing the
required amount of light and quality.
2. Ensure that electrical lights are switched off when they are not required.
The first rule is to ensure that the installed lighting power densities are as low as possible for a
building within the budget available.
As a recommendation, Table 4.1 below shows the lighting power densities in an office space that
can be achieved today to light up an office space with an average of 350 lux level.
Table 4.1 | Recommended Typical Efficient Lighting Power Density for an Office Space
For Office Spaces with an Average of 350 lux
7 to 9 W/m2
4 to 6 W/m2
Reduction of lighting power density also directly reduces cooling load and energy use in a building.
The reduction of 1 kW of installed lighting power in building would contribute to the following:
1. Peak load reduction of 1 kW of sensible heat.
2. Energy reduction in an air-conditioned area can be estimated using Equation 4.1 below.
EQUATION 4.1
ER = LPR x H +
Where:
ER
LPR
H
SCOP
LPR x H
SCOP
*For a typical Split Unit System, use a value of 3.0 for SCOP, if a full chilled water system is used, the SCOP
may be as high as 6.0 in this climate zone. Please consult with your air-conditioning system designer for
the most accurate value to use.
Lifecycle costing, financial payback or internal rate of return should be computed using Equation
4.1 to estimate the feasibility of implementing low lighting power densities in a building.
The second rule of energy efficiency in lighting systems is to ensure that lightings are switched
off when they are not required, especially when a space is not in use or when daylight provides
adequate lighting levels for the space. This can be achieved by ensuring that lightings are zoned
according to the opportunities of having them switched off using manual switches, motion
sensors or photocell sensors.
1 CANDELA
The candela (cd) is the standard unit of luminous intensity in the
International System of Units (SI). It is scientifically defined as the
magnitude of an electromagnetic field, in a specified direction, that has
a power level of 1/683 watt (1.46 x 10 -3 W) per steradian at a frequency
of 540 terahertz (540 THz or 5.40 x 10 14 Hz ). Luminous intensity
is a measure of the power emitted by a light source in a particular
direction based on a standardised model of the human eye to the visible
wavelength.
For the rest of us, one unit of candela is roughly equivalent to the
luminous intensity of a typical candle light.
2 LUMEN
The lumen is a measure of the total amount of visible
light emitted from a source. It is defined by Equation 4.2
shown below.
EQUATION 4.2
Lumen = cd.sr
Where:
cd = candela
sr = steradian (measurement of an unit angle in 3D
spherical coordinate system)
ARadiancuts out
a length of a circles
circumference equal
to the radius.
Candela =
ASteradiancuts out
an area of a sphere
equal to the radius
(radius)2.
Length = r
1 Radian
2,550 lumens
4
1 Steradian
Area = r2
r
Lux =
Lumen
m2
The lux level defines the brightness level of a point in space. The lux level requirement
is normally provided on the working plane of a space. For an office space, the lux level
provided defines the brightness on the horizontal surface of a table top.
Figure 4.1 | 1 lux is measured at a distance of 1 meter radius from a
1 candela light source
1 meter radius
1 ol
l lux
or
1 lm/m2
1 m2
Illuminance (or lux level) is the typical indicator of brightness level and is normally
measured at table top height or at working level (or position). A sample of typical lux
level requirement from the Malaysian MS 15251 is provided in Table 4.2 below:
Table 4.2 | Recommended Lux values in MS 1525
Task
Illuminance (Lux)
Lighting for
infrequently used area
100
100
200
300 - 400
200
100
Toilet
100
Bedroom
300 - 500
Classroom, Library
200 - 750
300
Example of Applications
Malaysian Standard (MS) 1525, Energy Efficiency for Non-Residential Buildings, available from Sirim Berhad.
4 LAMP
A lamp is a light emitting device. Fluorescent tubes, incandescent bulbs and solid state lighting (LED)
diodes are considered as lamps. Most suppliers of lamps provide the lumens output and the power
consumption on their packaging and brochures as a quick indicator of their efficiency.
5 LUMINOUS EFFICACY
Luminous Efficacy is an indicator of the efficiency of the lamps. It is defined as:
EQUATION 4.4
Lumen
Watt
Efficacy =
The higher efficacy values indicate higher efficiency, producing more light for the same energy used.
Typical luminous efficacy values are as shown in Figure 4.2 below.
Figure 4.2 | Typical Luminous Efficacy of Various Light Sources
280
70
150
100
90
80
200
160
140
130
100
18
15
50
Efficacy lm/Watt
250
200
l
nt
te
Po
D
ol
Co
LE
Da
yl
(L
ig
ia
ht
)
PS
)
di
re
Pr
w
Lo
es
Pr
gh
Hi
es
su
su
re
Di
So
So
di
se
um
Da
um
yl
(H
ig
PS
ht
ne
hi
ns
ffu
Su
ct
re
re
ou
Fl
Di
sc
en
(2
t(
01
T5
2)
)
LE
t(
en
sc
re
ou
Fl
Lo
Vo
In
lta
ca
ge
nd
Ha
es
lo
ce
ge
T8
nt
Importance
Typical Usage
90 to 100
80 to 90
60 to 80
40 to 60
20 to 40
Street lighting
Output of Luminaire
Output of Lamp
LOR =
A higher or lower LOR can have a dramatic effect on how many luminaires are required to achieve
the same light level for the same area. However, depending on the rooms shape and size, it may
not always be necessary to use the best LOR luminaire. Luminaires with a LOR above 90% are
available in the Malaysian market.
Gamma Angles
90
0
180
105
105
90
90
75
75
60
60
45
45
180
270
270.0
180.0
0.0
90.0
Flux 1200.00 m
Maximum 41111 col
Position C=3000 G=25.00
Efficiency 71.45%
Date: 11-01-2004
5pm on planes 270-90
30
15
15
30
9 GLARE INDEX
Glare evaluation can be quite subjective and varies from person to person.
For example, older folks are more sensitive to glare than younger persons
because their irises are no longer as flexible. The International Commission on
Illumination (CIE) defines glare as:
Visual conditions in which there is excessive contrast or an
inappropriate distribution of light sources that disturbs the
observer or limits the ability to distinguish details and objects.
There are many types of glare indices used by the lighting industry, such as the
CIE Glare Index, CIBSE Glare Index, Visual Comfort Probability (VCP), etc. that
are used as a measurement guide for glare. In recent years, the Unified Glare
Rating (UGR) as recommended by the CIE has become most widely accepted as
a general formula for assessing glare. The formula is given below:
EQUATION 4.6
Where:
= background luminance
= luminance of each light source numbered n
= the solid angle of the light source seen from the observer
= Guth position index
This formula requires the prior knowledge of the position and brightness of each
potential glare source. It is quite accurate but relatively difficult to work with.
It is best used from within some computer software. Such software packages
exist from most major producers of light fittings. These softwares require the
modelling of the scene under investigation and produces a glare index for a
defined position within a room.
The recommended maximum allowable Unified Glare Index (UGR) is provided
in Table 4.4 below.
Table 4.4 | Maximum Allowable Unified Glare Index (UGR) for
Different Type of Spaces
Working Area
Drawing rooms
16
Offices
19
22
25
28
Most luminaire suppliers can provide the maximum UGR computation of their
luminaires for any designed space.
LPD =
This is a useful indicator of the efficiency of the installed lighting system. The MS 15252
have specified the maximum allowable LPD for different types of spaces. A sample is
reproduced herewith:
Offices
15
25
10
Car Parks
Malaysian Standard (MS) 1525, Energy Efficiency for Non-Residential Buildings, available from Sirim Berhad.
3 FLUORESCENT LAMP
2 HALOGEN LAMP
A halogen lamp, also known as a tungsten halogen lamp
or quartz iodine lamp, is an incandescent lamp that has
a small amount of a halogen added chemically through
iodine or bromine. The combination of the halogen
gas and the tungsten filament produces a halogen
cycle chemical reaction which redeposits evaporated
tungsten back onto the filament, increasing its life and
maintaining the clarity of the envelope. Because of this, a
halogen lamps can be operated at a higher temperature
than a standard gas-filled lamp of similar power and
operating life, producing light of a higher luminous
efficacy (than incandescent bulbs) and higher Colour
Rendering Index (close to 100). Due to its small size
and very good CRI values, its use is very popular among
retail shop owners and interior designers to bring out
the quality of products or spaces being displayed.
Ballast
Both T8 and T5 fluorescent lamps require a ballast
(electronic gear) to start and maintain the light source
from the lamp. While it is possible to use either magnetic
or electronic ballasts for T8, the T5 will only work with
electronic ballasts. Magnetic ballasts have traditionally
been consuming up to 12 watts in operation, however,
newer low-loss magnetic ballasts have reduced the
amount to below 6 watts.
Electronic high-frequency ballasts typically increases
the combined lamp-ballast efficacy, leading to
increased energy efficiency and lower operating costs.
Electronic ballasts operate lamps using electronic
switching power supply circuits. Electronic ballasts
are typically more efficient than magnetic ballasts in
6 SODIUM-VAPOUR LAMP
3
2002, David Houghton, PE, Architectural Lighting Magazine, Metal Halide - Advances &
Improvements.
4
Assessment of LED Technology in Ornamental Post-Top Luminaires, Host Site: Sacramento,
California, Prepared for the U.S. Department of Energy by Pacific Northwest National
Laboratory, December 2011.
9 LIGHT FITTING/FIXTURE/LUMINAIRE
The luminaire, or light fitting as it is often referred to, is the equipment that physically
supports the lamp and provides it with a safe connection to the electricity supply. It
also provides protection for the lamp, particularly in hazardous areas and areas where
broken glass would be a particular problem. Light fittings also provide the optical control
that ensures the light is directed to where it is required as well as obstructing it from
those areas where it is not needed. This involves the use of reflectors, refractors and/
or diffusers. Most luminaires also have an appearance or style that can be an important
consideration for the designer. A typical ceiling recessed luminaire is shown below.
Figure 4.4 | Typical Luminaire Cross Section
Housing
Ballast
Ballast Cover
Reflector
Lamp
Lens
Reflection Type
Typical Reflectance
Mixed Specular
0.85
Specular
0.75
Mixed Specular
0.60
Specular
0.90
Aluminised Plastic
Specular
0.85
Super-purity Aluminium
Specular
0.95
Diffuse
0.90
Anodised Al
Stainless Steel
Low reflectance values such as stainless steel (0.60) indicates that only 60% of the light
is reflected, 40% is absorbed by the stainless steel and would end up as heat.
2 Reflector Design
The curvature and placement of the reflector will determine how the light is distributed and
influence the polar curve of the luminaire.
Figure 4.5 | Light Reflection of Various TypeS of Reflector Design
Certain reflectors are designed to deflect the light wide, while some are designed to concentrate
the light at one point. For an office space, light deflectors should be matched with the lamp
output and installation height of the luminaires, to ensure that the light level is evenly distributed
and meets the minimum desired lux level while minimising the number of required luminaires.
Downlight
Uplight
Working Plane
Luminous Efficacy*
CRI*
Working Hours*
Incandescent
8~15
100
750 ~ 2,000
Halogen
11~27
100
1,500 ~ 5,000
Compact Fluorescent
40~75
82
8,000 ~ 20,000
Fluorescent (T8)
60~90
50~98
10,000 ~ 75,000
LED (2012)
80
70~90
15,000 ~ 50,000
Induction Lamps
85
85
30,000 ~ 100,000
Fluorescent (T5)
73~114
70~90
10,000 ~ 45,000
Ceramic Metal-Halide
80~114
80~96
10,000 ~ 20,000
Direct Sunshine
100**
100
Diffuse Daylight
130**
100
70~150
24
14,000 ~ 32,000
100~177
10
12,000
Cool Daylight
(diffuse daylight filtered by
spectrally selective glazing)
200
100
LED Potential5
287
239
70
90
In addition, the efficiency of a lighting system in an office space is a combination of these 3 major factors: lamp,
ballast and luminaires (fixtures). Please keep in mind that specifying T5 lamps alone will not guarantee low
energy usage. It is still best to specify the maximum allowable lighting power density to achieve the minimum
lux level requirement for the desired office space and then allow the lighting designer, supplier and manufacturer
to make the best offer.
Figure 4.7 | Efficiency of a typical office lighting fixture is dependent on these 3 items
Lamp
Ballast
Fixture
Lighting
Energy Efficiency
Consideration
Solid-State Lighting Research and Development, Multi-Year Program Plan, Lighting Research and Development, Building Technologies Office, Office of Energy Efficiency and Renewable Energy,
U.S. Department of Energy, April 2013.
LIGHTING CONTROLS
The function of lighting controls is to ensure that electrical lights are switched off when they are not required to be on.
When rooms are not occupied or when daylight provides adequate lighting, the electrical lights should be switched off
to save energy.
Depending on the situation, lighting control is as simple as providing adequate manual lighting switches, up to a complex
system such as a combined system of motion and photosensors. In addition, the wiring circuitry of lighting should be
carefully designed to allow lighting to be switched off without affecting occupied areas. It is often found that lights for
certain areas cannot be switched off although they are not required (because the space is empty or adequate daylight is
available) because they are connected to lighting circuits in occupied and/or non-daylight areas.
1 DIMMING CONTROLS
2 MANUAL SWITCHES
Case Study of a Highly-Reliable Dimmable Road Lighting System with Intelligent Remote
Control, Chung H.S.H., Ho N.M, Hui S.Y.R., Mai W.Z, e.Energy Technology Ltd, City University of
Hong Kong, Municipal Management Bureau, Heshan City, 2005.
3 OCCUPANCY/MOTION SENSOR
Occupancy sensors are switching devices that respond to the presence and absence of people in the sensors field of
view. The system consists of a motion detector, an electronic control unit, and a controllable switch (relay). The motion
detector senses motion and sends the appropriate signal to the control unit. The control unit then processes the input
signal to either close or open the relay that controls power to the lights. The basic technology behind the occupancy
sensor is derived from security systems developed for residential and commercial applications to detect intruders.
However, the motion sensor has been refined so that it responds not only to the presence of occupants, but also to the
absence of occupants in the space. Other enhancements of the technology have centered on reducing costs, increasing
control intelligence, improving the ability to detect minor movements, and increasing adjustment capabilities.
Similar to photosensor, a manual-on and auto-off strategy is recommended for better energy efficiency. This strategy
is also known as absence detection, requires the lights to be switched on manually by the building occupant via the
manual switch. However, when the system detects that there is no movement in the room, it will automatically switch
the lights off. This prevents the lights from being automatically switched on when a person only needs to retrieve a small
item (pen, car key, hand phone, etc.) quickly from the room.
5
10
15
20
15
Wall-mounted sensor
Infrared sensor range for
detecting limb motion
Ultrasonic sensor range for
detecting full-body motion
Infrared sensor range for
detecting full-body motion
Ultrasonic sensor range for
detecting full-body motion
2 ULTRASONIC SENSORS
4 LIFE SPAN
It is difficult to adequately assess the life span of
occupancy sensor systems. Life cycle testing procedures
seem to suggest that a reasonable life span estimate for
most occupancy sensors would range between 10 to 15
years.7
5 SUGGESTIONS
The price of motion sensors varies depending on the
sensitivity requirements. For example, motion sensors
for an office space requires detection of fine movement,
whereas for a corridor space, the motion sensor is only
required to detect large movements.
Motion sensors are particularly effective in spaces
where the lights are typically left on when the space
is unoccupied, such as infrequently used corridors or
toilets.
It may be necessary in certain situations not to link all
lights to the motion sensor, allowing a couple of lights
to remain switched on at all times, so that the space
will not be pitch black when the lights are switched off
accidentally. In addition, it may also be unpleasant to
walk into a pitch black room and have to wait a couple of
seconds for the motion sensor to respond.
4 DAYLIGHT SENSOR
Daylight sensors can detect a specific user-defined
daylight level in a space and automatically switch
lighting on, off or dim them. It uses photocell technology
to measure the amount of available light.
When using a daylight sensor, it is very important to
position the daylight sensor such that it is not confused
by electrical lights. Designers should also be careful
with motion sensors incorporated with both motion and
daylight sensors as the viewing direction for motion
and daylight may be different.
For the Malaysian climatic zone with plenty of daylight
from the hours of 8am to 6pm, the energy savings
provided by dimming is rather small and is not required
to be used. A simple on/off daylight sensor will provide
very similar energy savings to a dimmable one.
When daylight is harvested in an office space, it is
recommended to practice the strategy of auto-off and
manual-on. This means that the electrical lights are
automatically switched off whenever the measured
daylight is adequate, but to switch on the light when the
daylight drops below the desired lux levels, the building
occupants will have to go to the switch to flick it on
manually. However, in public or common area spaces, it
may be more convenient to program it to automatically
switch the lights on as well when it drops below the
desired lux value.
6 CENTRALISED LIGHTING
MANAGEMENT
In medium to large buildings, it is useful to have a
centralised lighting management system (LMS)
incorporated into the building energy management
system (EMS). This system can be pre-programmed
with a fixed pattern to switch lights on/off for the entire
buildings common areas, accounting for weekdays,
weekends and public holidays. Systems such as this will
ensure that lights are switched off during non-occupancy
hours. It is also common to link occupancy and daylight
sensors to such a system to have a centralised control
to optimise the efficiency of the lighting system for the
building.
However, in office buildings, some occupants may be
working late on certain nights and will require common
areas such as corridor lights to be switched on until
late as well. In such situations, a line of communication
between the occupants and the building operator has to
be established to allow adequate common area lighting
for building occupants to exit the building safely. If this
happens infrequently, it will not be expensive to allow
common area lights to be switched on for a few nights
a year.
However, if this kind of situation happens frequently, it
will be very efficient to combine a centralised lighting
control system with a motion sensor system. An
agreement may be made such that a minimum amount
of night lights are provided for the common areas, while
the rest of the common area lights are fully controlled
via motion sensors after typical working hours.
8
Heschong Mahone Group, Large Office (Ziggurat Building) Site Report, High Efficiency Office:
Low Ambient/Task Lighting Pilot Project, Pacific Gas and Electric Company, 2009.
Existing lighting
Reduction %
13.2
6.0
54%
1.0
1.1
-11%
14.2
7.1
50%
42.0
18.3
56%
13.6
7.0
48%
Their report showed that the low ambient/task lighting configuration reduces lighting energy consumption by 56%, while
the peak lighting load reduced by 48% for the building studied. This was achieved while providing better satisfaction to
the building occupants.
In the Malaysian scenario, the Malaysian Standard (MS) 1525 (2007) recommended lux level brightness for Infrequent
reading and writing is 200 lux, while the recommended lux level for an office space is a maximum of 400 lux. In
addition, the MS 1525 (2007) allowable lighting power density for 400 lux is 15 W/m2. Meanwhile, a typical task light
power consumption ranges from 5 to 19 watts depending on the technology used (LED vs. fluorescent) and will easily be
able to provide up to 800 lux on the table top.
Providing an ambient space with 200 lux will only require a maximum 7.5 W/m2 when 400 lux is achievable using 15 W/
m2. Assuming an occupant density of 10 m2/person and one task light of 11 watts is provided for each person, the task
light power density for the space will be:
11 Watt / person
= 1.1 Watt/m2
10m2 / person
The total installed lighting power density in a low ambient/task light scenario will then be 7.5 W/m2 + 1.1 W/m2 = 8.6 W/
m2. Or a reduction of 43% from 15 W/m2 of installed lighting power density. It should also be highlighted that part of the
task lights will not be switched on due to building occupants attending meetings away from their desks, and some may
not be doing any paper reading work because they are just working on the computer (where 200 lux level is adequate).
In addition, for each Watt of power saved on the lighting, there is approximately 0.2 to 0.35 watts of electricity saved on
the air-conditioning because no heat is produced by the lights that are off.
More interestingly, there will be a cost reduction on the installation of the ambient lighting system because less
luminaires are required to provide a 200 lux level. This saving is approximately the same cost of providing one task light
every 10m2 of space. In short, it is possible to save approximately 50% lighting energy without any additional cost using
this strategy.
8 LIGHT ZONING
One of the quickest and easiest ways to reduce energy consumption in a building is to ensure that electrical lights are
switched off when the space is not being used or daylight is available. However, it is often found that lights in empty or
daylit spaces cannot be switched off because the lighting circuitry is linked to other spaces that require the lights to be
switched on. Therefore, it is important to plan the light zoning carefully.
In addition, it is often found that the same lighting fixture locations may be ideal for emergency, night lighting and security
lighting purposes. However, these three functions, and their operating schedules, should be considered independently,
so that the best system of luminaires and controls can be designed to ensure safety and energy efficiency. Emergency
lighting must meet stringent codes and standards for emergency egress when the building is occupied. Night lighting
provides minimal lighting during generally unoccupied periods, to allow safe passage through unoccupied spaces or
to provide access to light switches or areas controlled by automatic occupancy sensors. Security lighting provides
illumination for security personnel or cameras, and may operate intermittently or continuously, depending on the
continuity of surveillance.
More importantly, careful planning of lighting zones is a very effective, low-cost solution that can potentially provide
very high efficiency yields.
1 INDIVIDUAL ROOMS
No matter how small the individual office room is, it is always a good practice to provide a separate lighting zone for
the lights in the room. Typical individual office rooms are occupied by high ranking office staff that are important to the
company. It is very common that individual office rooms are empty for a significant part of the office hours because
important staff are often required to attend meetings outside their own office room, perhaps more than they are required
to be working in their own room.
2 DAYLIT AREAS
It is useful to map out the areas of daylight
harvested in a building. This is easily done in an
existing building by having a walkthrough in the
building. However, in new buildings, the potential
daylit spaces are not as obvious. In the case of
new building design, it is recommended that the
lighting designer should always have a discussion
with the architect to understand the design intent
of the windows and skylight provided in the
design to map out the potential spaces that will
be daylit due to the architectural design.
Windows
Zone 1
Flow of daylight
Zone 2
Light fixture
Zone 3
9, 10
11
4 EMERGENCY LIGHTING
Emergency luminaires are those designed to operate when there is an interruption in normal building
power. They are often selected from the luminaires providing general building illumination. In addition to
meeting all the relevant codes and standards, emergency lights should be located and aimed to orient the
occupants to the most direct paths of egress, with the least amount of confusion and glare. In addition,
emergency luminaires receive emergency power directly from a circuit breaker panel that is connected
to an emergency generator, or are powered by individual emergency ballasts.
If emergency lights are used for normal space lighting, any controls that dim them or turn them off (for
daylight harvesting, pre-set scenarios, dimming, etc.) must be wired in such a way that the luminaires
will revert to full operation in case of a loss of power. Manufacturers of lighting or dimming controls can
assist the design team in achieving this configuration.
5 NIGHT LIGHTING
A night lighting system serves several functions in buildings. It allows the first few occupants in the
morning or the last few occupants after hours to safely navigate circulation paths in a familiar building
until ambient lights can be manually turned on or off. It is also provided for security personnel to move
from area to area without leaving all the lights on in between. Finally, it allows firemen, police, or other
emergency personnel to find light switches in an unfamiliar building. This can generally be accomplished
by activating only a few luminaires for a short amount of time. Night lighting should be designed to
prevent energy wastage by a careful examination of the actual needs for after hours lighting. Some
combination of dawn-to-dusk operation only of lights at entry doors, combined with low-level lighting
activated by occupancy sensors, should be considered.
Design of night lighting requirements in office buildings in Malaysia is commonly practiced by providing
50% of the corridors light for night use without any other considerations. However, a significant amount
of lighting energy can be saved while providing a better environment to the building occupants if more
effort is made during the design stage to plan the night lighting requirements.
Night lighting in offices is also required to be provided to create a safe environment for building occupants
that work late beyond the normal office hours. In situations such as this, it useful to plan all possible
travelling routes (from desk to pantry, toilet or exit) and provide the necessary night lighting strategy
for it. While it may not be necessary to provide the full light level on these routes when not in use, it is
practical to allow the building occupants to fully light up these routes when they are using it via manual,
time-delay, or motion sensor switches.
In addition, it is often a good idea to enable lights to be switched on at strategic places, adequate enough
for late night workers to feel safe in the building. If this is not done, it is common for office workers to light
up the entire floor even though only a small area is used by them.
Strategies should be in place that a late night office worker leaving the building should be able to take
actions to turn off the lighting in the office space. This may be done manually from strategically placed
manual switches, motion sensors or by informing the guards on duty.
6 SECURITY LIGHTING
Security personnel can often use the night lighting system to move around a facility, and activate higher
levels of lighting only when it is necessary. Security lighting should operate continuously only if the space
or camera images of the space are directly and continuously viewed, and immediate action can be taken.
Otherwise, lights associated with security cameras can be controlled by occupancy sensors, so that both
lights and cameras are activated by an intruder. In security cases, advanced motion sensor technologies
such as microwave or tomographic sensors may be considered for a higher level of safety provision.
SUMMARY
Electrical lights in an office building contributes up to 25% of the energy used in the building. It also contributes up to 20%
of the heat gain for the air-conditioning system. Therefore, it is highly desirable to design lighting systems in buildings
with low lighting power density. Low lighting power density can be achieved using efficient lamps in combination with
efficient ballasts and efficient light fittings that distribute light wide and evenly. For fluorescent lights, the efficiency of
the ballasts (gears) will also contribute to the final efficiency of the lighting system.
In addition to having an installed low lighting power density, lighting controls are important to ensure that lights are
switched off when they are not required. Adequate manual switches, building occupant awareness training, occupancy
sensors, daylight sensors, light schedules, delay timers, lighting management systems, etc. are used to improve the
energy efficiency of the lighting system in building by ensuring that lights are switched off when not required.
It is also important to plan for night lighting requirements, security lighting requirements, fire safety lighting requirements
and faade lighting requirements. Making plans for such lighting systems early will ensure that the energy efficiency
considerations during the operation stage will be taken into account.
Finally, the lighting system should be properly commissioned, fine-tuned and be continuously monitored. This will ensure
that the installed lighting system is optimised for the comfort of the building occupants and yet energy efficient for the
life-time of the building.
The combination of all these measures mentioned will help to reduce lighting energy consumption in a building
significantly and is recommended to be practiced in all building designs.
END OF CHAPTER 4
CHAPTER
AIR-CONDITIONING
SYSTEM DESIGN
AIR-CONDITIONING
SYSTEM DESIGN
INTRODUCTION
The cooling load calculation of a building
determines the air-conditioning capacity that is
required to be installed in the building. This design
calculation has a large impact on the initial cost
of the air-conditioning system for the building.
The right-sizing of the air-conditioning system
will lead to a lower air-conditioning system cost
and lower running cost because the system is
running close to its optimal design point. If the
computation is done too conservatively (which is
usually the case), the initial installation cost of the
air-conditioning system will be more expensive
(and wasteful) for the building owner, who will
also have to pay for higher running costs during
operation because the equipment was oversized
and would not be running at its optimal design
point.
On the other end, if the air-conditioning system is
undersized, the building will not be provided with
adequate cooling and will cause significant distress
to both the building owner and design engineers
due to complaints from the building occupants.
Due to this reason alone, most air-conditioning
system designers tend to be conservative in their
design and oversize the air-conditioning system.
The level of conservativeness of each designer
depends on the persons understanding of the
various components of a buildings cooling load. A
designer with a clear understanding of the various
contributors to the cooling load in a building will be
able to make the necessary design assumptions
to optimise the capacity of the air-conditioning
system without excessively oversizing the cooling
system.
Over the years, over-reliance on computers to
KEY RECOMMENDATIONS
It is important to understand all the contributing components of heat gain in each part of the air-conditioning system
to ensure that the entire system is sized correctly for each part of the system. A complete understanding of heat gain
components reduces the need to put in extra safety factors during the design stage to cater for unknown factors that
might arise during the operational stage. Figure 5.1 is provided as a summary of the various components of heat gain at
each stage of the cooling load as heat is transferred from a space in the building to the outdoors.
Figure 5.1 | Heat Gain Components for Each Cooling Load IN a Typical Air-Conditioning System
LOAD
HEAT
Space
Cooling
Load
Cooling
Coil
Load
1. Internal Gain
2. External Gain
2. Fan Power
3. Duct Conduction
Heat Gain
Heat
Rejection
Load
Chiller
Load
1. Chilled Water
Pump Power
2. Pipe Conduction
Heat Gain
1. Chiller Power
2. Condenser Water
Pump Power
The following heat gains have to be addressed to compute the space cooling load:
1) Internal Gain
a) People
b) Electrical lights
c) Equipment and appliances
2) External Gain
a) Heat gain entering from the exterior walls and roofs
b) Solar heat gain transmitted through the fenestrations
c) Conductive heat gain coming through the fenestrations
d) Heat gain entering from the partition walls and interior doors
e) Infiltration of outdoor air into the air-conditioned space
In a cooling coil load, the following heat gains are in addition to the space cooling load:
1) Mechanical Fresh Air Intake
2) Fan Power
3) Fresh Air (or Return) Duct Conduction Heat Gain (if it is located outside the air-conditioned space)
In a chiller load, the following heat gains are added to the cooling coil load:
1) Chilled Water Pump Power
2) Chilled Water Pipe Conduction Heat Gain (if it is located outside the air-conditioned space)
In a heat rejection load, the following heat gains are added to the chiller load:
1) Chiller Power (Electrical load used by chiller)
2) Condenser Water Pump Power
These are all the heat gain components that need to be accounted for to size air-conditioning systems properly. The rest of
the chapter will describe the boundaries of input values for these heat gain components.
In a typical office building scenario, latent heat is only produced by people and infiltration. However,
designers are cautioned that latent heat can also be produced by any other moisture source such
as boiling water, leaking roofs, etc.
The supply air flow rate due to sensible heat is provided by Equation 5.3 below.
EQUATION 5.3
AFsensible =
Where:
AFsensible
Qtotal sensible
Cp
=
=
=
=
=
Qtotal sensible
Cp T
The supply air flow rate due to latent heat is provided by Equation 5.4 below.
EQUATION 5.4
AFlatent =
Where:
AFlatent
Qtotal latent
Hv
=
=
=
=
=
Qtotal latent
Hv X
In theory, air flow rates for both the sensible and latent cooling load should be computed and
the higher flow rate is used to ensure adequate sensible and latent cooling is delivered to the
space. In actual practice, for an office building scenario, the sensible cooling load dominates
the latent cooling load significantly; therefore the air flow rate is normally computed from the
sensible cooling load only. Designers are advised to be especially careful if the higher air flow
rate is caused by the requirements of the latent load, because at this flow rate, it will over-cool
the space beyond the design air temperature.
Latent Heat
(W/person)
70
35
70
45
75
55
75
55
Bowling
170
255
Degree of Activity
From the building occupancy density in m2 per person, the total sensible and latent heat
from people can be calculated.
The building occupant density is normally well defined by the building owner or
developer. Typically, it ranges from a dense value of 8m2 per person to a sparse occupant
density of 16m2 per person.
It is also often useful to understand the diversity of occupant density as it will help
to reduce the peak cooling load in a building. Designers are encouraged seek out this
information from the potential building owner or intended tenant. It the building owner is
currently occupying an existing building, a site visit is highly encouraged, just to observe
the existing work culture in their organisation.
2009 ASHRAE Fundamentals, F18, Non-Residential Cooling and Heating Load Calculations, Table 1.
Offices
15
25
10
Car Parks
Malaysian Standard (MS) 1525, Energy Efficiency for Non-Residential Buildings, available from Sirim Berhad.
Load Factor
W/m2
Light
5.4
Medium
10.8
Medium/Heavy
16.1
Heavy
21.5
Description
Again, whenever possible, designers are highly encouraged to ask the intended building
occupants about the type of equipment that will be brought into the building. In addition, it is
also important to learn about the intended building occupants work culture, which may lead
to a potential use of diversity factor for equipment and appliances, especially if some of the
computers are switched off when the building occupants are not in their office space.
Finally, in the evolution of the green and/or sustainable global movement, many manufacturers
of computers, monitors and other electrical appliances are rapidly reducing their equipments
energy consumption. Therefore, office space heat gain from equipment and appliances may
reduce in the near future. In addition, advancements in technology is also rapidly changing the
way people usually work, leading to building occupants using tablets instead of computers to
do their work. This may further reduce the heat load caused by equipment in an office building.
Designers are encouraged to keep themselves abreast with the changes that are happening in
the office environment and account for the effects they may have on air-conditioning system
load calculations.
3
4
2009 ASHRAE Fundamentals, F18, Non-Residential Cooling and Heating Load Calculations, p 6-14.
2009 ASHRAE Fundamentals, F18, Non-Residential Cooling and Heating Load Calculations, Table 11.
MS 1525
35.1
33.3
35.6
30.9
26.3
27.2
25.9
28.4
Descriptions
The computed psychrometric from the above conditions are shown in Table 5.5 below:
Table 5.5 | Air psychrometric properties at various design conditions
Descriptions
Enthalpy (J/kg)
ASHRAE design
weather database
v4.0
MS 1525
79,300
84,200
77,300
91,100
47.9
60.9
44.0
82.1
17.2
19.8
16.2
23.4
22.4
24.7
21.4
27.5
The MS 1525 recommends a design condition with higher enthalpy than the ASHRAE design weather database.
Comparisons with the hourly weather data of Kuala Lumpur in the Test Reference Year (TRY) as described in Chapter 2
shows that the ASHRAE recommended design weather data is similar to the conditions of the peak dry bulb temperature
in the TRY. However, at this design condition (peak dry bulb temperature), the enthalpy of the air properties is 15% lower
than the peak enthalpy found in the TRY and may cause an undersize of the latent load in the building.
From this simple comparison, the MS 1525 recommended design condition seems to be a good compromise, accounting
for both sensible and latent heat gain and references well to the peak conditions of the TRY weather data.
CONDUCTION
Conduction heat gain in a building is a combination of the following:
1 Colour of Wall
The colour of the wall/roof influences the conduction of heat into buildings. Dark colours absorb heat and light colours
reflect heat away from the building. The impact of this is computed by most computer programs as an input for the wall/
roof solar absorption value (). Light colours have solar absorption values close to zero, while dark colours have solar
absorption values close to 1.
2 Conductivity of Building Materials
Conductivity (commonly known as K-value) and thickness of the building material influences the rate of heat transfer
through wall/roof. Together with the surface film resistance on both sides, the U-value of wall/roof is computed. The
U-value is a simplified indicator of steady state heat conduction through the wall/roof. In reality, heat transfer through
the wall/roof of a building is never in a steady state.
3 Surface Film Resistance
Resistance Layers
Rsi = 0.17
Room Hear Loss
Upwards Through
Roof Space
Rse = 0.04
Rsi = 0.18 Rse = 0.04
Rsi = Resistance Surface Internal
Rse = Resistance Surface External
Units of Resistance = K/W
Rsi = 0.17
Rse = 0.04
Room Heat Loss
Downwards Through
Ground Floor
SOLAR RADIATION
All air-conditioning sizing computer programs will compute the solar radiation
and effect of local shade based on the ASHRAE methodology (or similar) for a
clear sky condition for direct and diffuse solar radiation. The important things
to take note of for solar radiation properties for the Malaysian climate are the
following:
Ezzuddin Ab Razad, CK Tang, Public Works Department (PWD), Kuala Lumpur, Malaysia. Control Of Moisture & Infiltration For Advanced Energy Efficient Buildings
In The Tropics, Conference on Sustainable Building South East Asia, 4-6th May 2010, Malaysia
Once the occupant density is known, the total fresh air requirement per person is easily computed using Equation 5.5
shown below:
EQUATION 5.5
m2
person
0.3 l/s
m2
2.5 l/s
person
Table 5.6 | Total Fresh Air RequirementS per Person for Different Occupant DensitIES
Occupant Density
(m2/person)
Floor Area
Requirement
l/s per person
People
requirement
l/s per person
Total l/s
per person*
Total cfm
per person*
Total l/s
per m2
Total cfm
per ft2
2.4
2.5
4.9
10.4
0.61
0.121
10
3.0
2.5
5.5
11.7
0.55
0.108
12
3.6
2.5
6.1
12.9
0.51
0.100
14
4.2
2.5
6.7
14.2
0.48
0.094
16
4.8
2.5
7.3
15.5
0.46
0.090
18
5.4
2.5
7.9
16.7
0.44
0.086
20
6.0
2.5
8.5
18.0
0.43
0.084
* Valid for most cooling delivery systems with the exception of low velocity displacement achieving unidirectional flow and thermal stratification (in which case,
divide the numbers in the table by 1.2) and where the total fresh air is less than 15% of the minimum primary supply air flow rate.
Table 5.6 above is valid in most cases except for these two (2) situations mentioned below, where further computation is
required:
1. Where, cooling is provided via low velocity displacement achieving unidirectional flow and thermal stratification.
This method of air quality delivery is deemed to have a higher distribution effectiveness compared to the other
methods of delivery, allowing a reduction of 20% of the fresh air requirement. It is also important to note that in
Table 6-2 in ASHRAE 62.1, floor supply of cool air and ceiling return provided that the 150 fpm (0.8 m/s) supply jet
reaches 4.5 ft (1.4 m) or more above the floor. Note: Most underfloor air distribution systems comply with this provision,
does not qualify for a reduction of 20% of the fresh air requirement.
2. Where, the percentage of total fresh air supply flow rate is higher than 15% of the minimum primary supply air
flow rate. When this situation occurs, an increased fresh air supply is required to maintain adequate air quality in
a building. In the Malaysian climatic zone, this situation will likely arise from the use of variable-air-volume (VAV)
systems (where the minimum flow rate may be as low as 30% of the design air flow rate) or from the use of any type
of radiant cooling system, where the recirculated air flow rate is minimal, therefore the percentage of fresh air in
such systems may be higher than 15%. Refer to ASHRAE 62.1, System Ventilation Efficiency, for details to compute
the minimum fresh air requirement for these conditions.
2 FAN POWER
The 1st law of thermodynamics states that energy cannot be destroyed, therefore, the use of
fans to deliver cold air into spaces also causes heat gain for the cooling system. In most cases,
100% of the power used by the fan is converted into heat gain seen by the cooling coil (the only
case where this is not so is when the motor for the fan is located outside the air-conditioned
space). The heat gain produced by the fan has to be captured in the air-conditioning system
sizing computation. Most computer programs that conduct cooling load calculations provide
inputs for the basic fan power design parameters. Usually the typical input parameters are:
1. Total Flow Rate
2. Total Fan Pressure
3. Total Fan Efficiency
Wf =
Where:
Wf = Fan Power (Watt)
Q = Volume of Air Flow Rate (m3/s)
Pt = Total Fan Pressure (Pa)
f = Total Fan Efficiency (%)
Q Pt
f
Designers are recommended to keep duct length as short as possible to reduce static pressure in ducts.
The location of the AHU will have a significant influence on this design factor.
Upsizing ducts will also help to reduce the static pressure drop in ducts.
2. Air Dynamic Pressure
Air dynamic pressure is a factor of air speed and is determined by the fan inlet and outlet area.
3. Pressure Drop Due to Air Filters
Selection of low pressure loss air filters will also help to reduce the coil cooling load. In addition to the
Minimum Efficiency Reporting Value (MERV, filtration efficiency rating) rating of air-filter, it is also
important to specify the maximum allowable pressure loss in air filters. For typical office buildings, a
MERV rating of 5 to 8 is typically used with an allowable peak pressure drop of 150Pa.
Energy efficient air filters will be able to provide a MERV rating of 5 to 8 while reducing pressure loss to
below 100Pa.
The key criterion that reduces pressure loss in a mechanical air filter is the reduction of the air-speed that
flows across the air-filter. The reduction of air speed is achieved by having a large surface area for the
air to flow through the air-filter. Air-filters that have a W or V-shaped design and other types of folded
designs are made to increase the surface area, to reduce the pressure drop across the air-filters.
Cooling coil selection would also contribute to the pressure drop. High fin density and increased number
of coil rows will increase the air pressure drop in cooling coils. Air pressure drops ranging from a low of
30Pa to a high of 300Pa is possible depending on the design flow rate parameters and coil height.
The key criterion that reduces the pressure drop in cooling coils is the exposed surface area of the
cooling coil. The larger the surface area provided for the return air intake, the less pressure losses there
will be. Unfortunately, a larger surface area also increases the costs of the AHU due to the use of more
materials to construct it.
FEt = Fe x Me x Be x Ve
Where:
FEt = Fan Total Efficiency (%)
Fe = Fan Efficiency (%)
Me = Motor Efficiency (%)
Be = Fan Belt Efficiency (%)
Where:
Be = 100%, if fan is direct driven by the motor
Ve = Variable Speed Drive Efficiency (%)
Where,
Ve = 100%, if no Variable Speed Drive is used
A. FAN EFFICIENCY
Type of Fan
Forward Curved
Backward Curved
Centrifugal
Air Foil
Radial Blade
Propeller
Tube Axial
Axial
Vane Axial
Mixed Flow
1,800
52
3,400
60
6,800
62
10,200
67
13,600
67
17,000
67
1,800
72
3,400
76
6,800
77
10,200
78
13,600
78
17,000
80
1,800
75
3,400
79
6,800
81
10,200
82
13,600
83
17,000
83
1,800
60
3,400
60
6,800
61
10,200
63
13,600
65
17,000
65
1,800
52
3,400
55
6,800
56
10,200
56
13,600
56
17,000
62
1,800
60
3,400
63
6,800
63
10,200
626
13,600
64
17,000
66
1,800
63
3,400
63
6,800
63
10,200
67
13,600
67
17,000
70
1,800
63
3,400
63
6,800
65
10,200
70
13,600
73
17,000
74
B. MOTOR EFFICIENCY
Most motors operate at a constant speed. A typical constant speed of motor ranges from 500
to 1,800 revolutions per minute (RPM). The power consumption of a motor is basically the
rotational Torque multiplied by the RPM. Since the RPM is fixed, the power consumption of a
motor is directly linked to the Torque.
The MS 1525 (2007) provides the following recommended minimum efficiencies for motors:
Table 5.8 | 4 Poles Motor Minimum Efficiency
Motor Efficiency (%)
Motor Capacity
(kW)
1.1
76.2
83.8
1.5
78.5
85.0
2.2
81.0
86.4
82.6
87.4
84.2
88.3
5.5
85.7
89.2
7.5
87.0
90.1
11
88.4
91.0
15
89.4
91.8
18.5
90.0
92.2
22
90.5
92.6
30
91.4
93.2
37
92.0
93.6
45
92.5
93.9
55
93.0
94.2
75
93.6
94.7
90
93.9
95.0
Motor Capacity
(kW)
1.1
76.2
82.8
1.5
78.5
84.1
2.2
81.0
85.6
82.6
86.7
84.2
87.6
5.5
85.7
88.6
7.5
87.0
89.5
11
88.4
90.5
15
89.4
91.3
18.5
90.0
91.8
C. BELT EFFICIENCY
AHU belt efficiency typically ranges from 95% to 98% depending on the size and belt
type. Most fan manufacturers (such as Kruger or Nicotra) will be able to provide the
total fan efficiency inclusive of fan, motor and belt during the fan selection process.
Direct driven fans are more efficient because there are no belt losses.
Belt Drive
DIRECT Drive
DISADVANTAGES
4 bearings required
Belt dust
Load on bearings exceeds wheel weight
ADVANTAGES
No drive losses (typ. 3.5%)
No belt wear
No belt tensioner required
Less bearing load - Longer bearing life
No belt noise
ADVANTAGE
Change pulleys to adjust capacity
DISADVANTAGES
Adjust width to adjust capacity
Depending on the actual design, fan power can range from less than 2 W/m2 to a high
of 10 W/m2 of the conditioned space. In other words, the heat gain caused by fan power
may be has high as electrical lighting or equipment (appliances plug load) if it is not
designed well. The authors have personally encountered many air-conditioning systems
sized with the fan energy assumed to have zero static pressure. This may explain the
reason behind why some air-conditioning system designers insist on using 20 W/m2
for lighting power density to size the air-conditioning system regardless of the lower
installed lighting power density used.
CHILLER LOAD
In addition to the heat from the cooling coil, the chiller load has additional heat gains from the
chilled water pump and conduction heat gains in pipes. These heat gains are described below.
Default design chilled water supply temperature is 44F (6.7C) and 56F (13.3C) for
return, providing a T of 12F (6.7C).
Higher T reduces flow rate and pump power requirements. However, at the same time,
the efficiency of the chiller is reduced if the supply temperature is lowered below 44F
(6.7C). Moreover, cooling coil pressure (both air and water-side) may increase due to
the longer distance travelled in the cooling coil for the heat transfer to be made, increasing
energy consumption. Designers are recommended to conduct adequate computations
to ensure that the advantages gained from such implementation reduces the net energy
consumption of the system.
Pump Head
The pump head is a factor of the flow rate, pipe size, number of bends/elbows and fittings
used.
Typical pump heads in office buildings in Malaysia range from 15m to 45m of water height.
Keeping the pump head low reduces energy consumption.
3 Pump Efficiency
The Energy Efficiency and Conservation Guidelines for Malaysian Industries published by Pusat Tenaga
Malaysia in 2008 provides the following recommendations for minimum pump efficiency for different
flow rates and pump types.
Table 5.10 | Recommended minimum pump efficiency
Efficiency (%)
Horizontal
/ Vertical
Split Casing
(centrifugal and
closed impeller
types)
(%)
Vertical
Multistage
& Horizontal
Multistage /
Closed Coupled
(closed impeller
types)
(%)
Submersible
(semi open and
open impeller
types)
(%)
Process Pump
(open impeller
types)
(%)
100
50 60
55 75
48 55
48 52
110 250
65 75
73 76
68 75
48 55
48 52
300 450
75 80
75 79
70 75
55 65
48 52
460 600
78 82
75 79
55 65
48 52
700 1000
80 85
78 82
65 72
48 52
1100 1500
83 87
78 82
60 68
1600 2500
83 87
78 83
60 70
Flow (gpm)
2600 3600
80 86
70 75
3700 4000
82 86
75 80
> 5000
80 88
75 80
The recommendations are the same as Fan Motor Efficiency in on page 107.
1 CHILLER POWER
The electrical power used by the chiller to drive the compressor will end up as
heat in the condenser (heat rejection) part of the chiller. From the coefficient
of performance (COP) curve of a chiller, the electrical power can be estimated
from the chiller cooling load. In a hermetically sealed chiller, where the motor
is cooled by the refrigerant, 100% of the power used by the chiller will end up
as heat on the condenser side.
2 CONDENSER PUMP
The condenser water pumps heat contribution to the heat rejection system
is exactly the same as the chilled water pump. The recommendations for the
chilled water pump is applicable here as well.
SUMMARY
This chapter provides an overview of all possible components of heat load
for an office building. It is intended to provide a clear comprehension of the
various heat load components. Hopefully, by understanding the heat flow
process in an air-conditioning system, designers will be able to make better
design decisions and assumptions, reducing the oversizing of systems. This
will lead to lower installation costs by building developers and yet improving
the energy efficiency in the building, providing a win-win situation for all.
It has been shown in this chapter that typical air-conditioning system cooling
load computations in buildings can be broken-down into the following loads:
1. Space Cooling Load
2. Cooling Coil Load
3. Chiller Load
4. Heat Rejection Load
For each of the cooling loads, the various heat gain components and their
corresponding typical design values are provided in this chapter.
It is strongly recommended that designers should always keep in mind the 1st
law of thermodynamics, that energy (as in heat for the air-conditioning system)
cannot appear out of nowhere and energy also cannot disappear into the thin
air. As long as a designer has accounted for all the various potential heat gains
in a building, it is unnecessary to use design values that are not based on actual
design conditions, for example, using a lighting power density of 20 W/m2 for
air-conditioning sizing computations, when the actual designed lighting power
density is only 10 W/m2.
END OF CHAPTER 5
CHAPTER
SIMULATION INPUT
DETAILS FOR
CHAPTER 7 & 8
SIMULATION INPUT
DETAILS FOR
CHAPTER 7 & 8
INTRODUCTION
The outputs and recommendations in Chapter 7 & 8 rely heavily on the simulation case studies of
test case reference scenarios of a Malaysian reference building. Therefore Chapter 6 is dedicated to
describing the reference building scenarios.
This chapter describes the simulation engine, weather data, internal gain, building fabric and the airconditioning system in detail.
SIMULATION ENGINE
The software used for the building energy simulation for Chapter 7 & 8 is the VE-Pro software IES,
UK, version 2012.
The VE-Pro software consists of a suite of modules and tools for detailed energy simulations that
comply to all the requirements of ASHRAE 90.1 (2007).
WEATHER DATA
The hourly weather data of Kuala Lumpur used in this
chapter was based on a Test Reference Year (TRY)1
weather data developed in University Teknologi Malaysia
(UiTM) under the DANCED (Danish International
Assistant) project for Energy Simulations for Buildings in
Malaysia. The TRY is based on 21 years (1975 to 1995) of
weather data from the Malaysian Meteorological Station
in Subang, Klang Valley, Selangor. The hourly weather
data that was obtained from this station is as shown in
Table 6.1 below.
TABLE 6.1 | WEATHER DATA COLLECTED IN SUBANG
Subang Meteorological Station
(Klang Valley, Selangor, Malaysia)
Longitude: 101deg 33
Latitude: 3deg 7
Parameters (hourly2)
Units
Cloud Cover
[oktas]
[C]
[C]
Relative Humidity
[%]
[100*MJ/m2]
Sunshine Hours
[hours]
Wind Direction
[deg.]
Wind Speed
[m/s]
1
Reimann, G. (2000) Energy Simulations for Buildings in Malaysia, Test Reference Year, 18-25.
2
The values are integrated over a period of one hour, but the exact time interval has not been
specified.
BUILDING MODEL
A medium-rise building of 17 floors is assumed for this study. The floor to ceiling height is assumed
to be 4 meters. The floor areas are as described in the table below.
No
Description
Floor Area
Units
1,650
m2/floor
AC
Lift Lobby/Walkway
170
m2/floor
AC
AHU Rooms
100
m2/floor
AC
Lift Shafts
165
m2/floor
NV
Pantry
22
m2/floor
Fire Staircases
72
m2/floor
NV
Toilets
80
m2/floor
2,259
m2/floor
17
floors
38,403
m2
Ventilation Concept
Offices
Offices
Toilet
AHU
Offices
Walkway
Offices
Pantry
Offices
Offices
Lift Shaft
Stairs
Offices
Offices
Description
Toilet Ventilation
Strategy
Mechanically ventilated for 10 ACH as exhaust air. Fan Static Pressure of 2 w.g. (500 Pa) assumed.
Combined fan, motor and belt (total) efficiency of 50% assumed. Fan operates during occupancy hours of
9am to 6pm.
Toilet Lighting
Strategy
100% electrical lights at 10W/m2, switched on during occupancy hours. Occupancy sensor is assumed to
be installed. It is assumed that the toilet lights is only switched on 50% of the time during occupancy hours
and switched off during non-occupancy hours.
Pantry Lighting
Strategy
100% electrical lights at 10W/m2, switched on during occupancy hours. Occupancy sensor assumed as well,
that will keep the lights switched off 50% of the time.
Pantry Ventilation
Strategy
Air-conditioned as part of Office space with same operating hours of Office space.
2 W/m2
Lights are switched on 24 hours daily.
Lift Lobby/Walkway
100% lights at 10 W/m2 switched on during occupancy hours from 9am to 6pm weekdays. 50% lights on
during other hours and weekends.
Because this space is air-conditioned, it will always be assumed to be located away from an external wall.
i.e. since it is an air-conditioned space, locating it with an external wall would give it the same conditions as
an office space, which would defeat the purpose of this study.
AHU Rooms
Always assumed to be located away from the external wall because it does not benefit in terms of daylight
harvesting or view out and because it is also an air-conditioned space.
Office Lighting
Strategy
10
15 W/m2 peak load is assumed during office hours of 9am to 6pm with 30% dip in power consumption from
12:30 noon to 1:30pm on weekdays. 35% of the peak load is assumed for all other hours.
Description
Assumptions
11
12
Glazing Properties
13
External Wall
Properties
Typical 100mm thick Concrete Wall with 15mm Cement Screed, U-value 3.2 W/m2K
1
2
14
Internal Wall
Properties
Typical Internal Brick Wall with Cement Screed, U-value 2.0 W/m2K
15
Roof Properties
Insulated Flat Roof, Heavy Weight with 50mm polystyrene foam used for a U-value of 0.52 W/m2K
16
Base Ventilation
System
VAV
Fan Total Pressure: 3 w.g. (750 Pa)
Fan Total Efficiency: 65%
Turn Down Ratio: 30%
Design Off-coil Temperature: 12C
17
18
Base Chiller
19
Base Condenser
System
20
Cooling Tower
21
22
Infiltration
The infiltration rate of the building is based on the assumption of a crack along the window perimeter.
Windows are assumed to be 2.8m height (for 70% WWR with ribbon window layout) and each piece of
window is 1.2 meters width. It is also assumed that 2 pieces of window is required to make the total height
of 2.8 meters.
The assumption of crack coefficient is based on 0.13 (l s-1 m-1 Pa-0.6) for a weather-stripped hinged window.1
The simulation study uses the wind pressure coefficients taken from the Air Infiltration and Ventilation
Centres publication Air Infiltration Calculation Techniques An Applications Guide2. These coefficients are
derived from wind tunnel experiments.
23
Office Occupancy
Weekdays: 10 m2/person, 9am to 6pm, with 50% reduction at lunch time of 12.30 noon to 1.30pm.
Weekends: Empty
24
Lift Core
Lift Core is assumed to have an infiltration rate of 1 ACH during occupancy hours and 0.5 during nonoccupancy hours.
Lift power is ignored in this study.
25
26
All other miscellaneous power use is ignored. These items include potable water pumps, escalators, security
access systems, etc.
An Analysis and Data Summary of the AIVCs Numerical Database. Technical Note AIVC 44, March 1994. Air Infiltration and Ventilation Centre.
Air Infiltration Calculation Techniques An Applications Guide, Air Infiltration and Ventilation Centre. University of Warwick Science Park. Sovereign Court, Sir William Lyons Road, Coventry CV4 7EZ.
VAV Controller
Toilets
AHUs
Lift
Lobby
Pantry
Office
N
Office
E
Office
W
Office
S
Office
C
Fraction of Full-Load
Power
0.30
0.13
0.50
0.30
0.70
0.54
0.90
0.83
1.00
1.00
6 COOLING COIL
Cooling coil is auto-sized
during system sizing run. A
cooling coil contact factor of
0.91 is assumed. Cooling coil
is oversized by 15% as per
ASHRAE 90.1 requirements.
1 CHILLED WATER
DISTRIBUTION
The chilled water pump is oversized
by 15% and 0% distribution losses
are assumed as per ASHRAE 90.1
requirements. Chilled water supply
temperature is set at 6.67C (44F) and
a T of 6.67C (12F) is assumed. The
cooling coil in the AHU is automatically
sized to these requirements based on
the design off-coil temperature.
A primary only variable pump is
assumed with a specific pump power of
545 W per l/s.
2 CHILLERS
Three (3) chillers are required for this building model. These chillers are sized equally
and are sequenced to operate in a stack mode, i.e. when one of the chillers has reached
maximum capacity, an additional chiller is turned on to provide cooling.
The base chiller is a centrifugal chiller with a COP of 5.7 and has a peak cooling
capacity of 2,138 kW (608 ton) per chiller.
Region
Malaysia
Latitude
3.12 N
Longitude
101.55 E
Altitude
22.0m
8.0 hours
0.0 hours
From
Through
Adjustment for other months
0.0 hours
Site Data
Ground reflectance
0.2
Terrain type
Suburbs
Normal
SubangTRY.fwt
99.6 %
0.4 %
22.0C
35.1C
26.3C
Humidity
Solar Radiation
Linke Turbidity Factor
Jan
25.50
34.00
24.50
2.74
Feb
25.80
34.80
24.90
2.70
Mar
26.40
35.10
25.20
2.68
Apr
26.50
34.90
26.20
2.76
May
26.90
34.80
26.30
2.79
Jun
26.00
34.20
25.40
2.85
Jul
26.00
34.00
25.40
2.86
Aug
26.10
34.10
25.30
2.80
Sep
26.00
34.00
25.20
2.72
Oct
26.10
34.00
25.50
2.74
Nov
25.60
33.20
25.60
2.71
Dec
25.60
33.20
25.00
2.75
Room Type
Room ID
Name
External Ventilation
[AHU_0000]
01 AHU
[AHU_0001]
02 AHU
NCM Activity
[AHU_0002]
03 AHU
Room Conditions
[AHU_0003]
04 AHU
Heating
[AHU_0004]
05 AHU
Profile
off continuously
[AHU_0005]
06 AHU
Setpoint: Constant
19 C
[AHU_0006]
07 AHU
0.00 l/(hpers)
[AHU_0007]
08 AHU
[AHU_0008]
09 AHU
Cooling
Profile
off continuously
[AHU_0009]
10 AHU
Setpoint: Constant
23 C
[AHU_0010]
11 AHU
[AHU_0011]
12 AHU
Model Settings
Solar Reflected Fraction
0.05
[AHU_0012]
13 AHU
1.00
[AHU_0013]
14 AHU
[AHU_0014]
15 AHU
Systems
HVAC System
Main system
[AHU_0015]
16 AHU
Main system
[AHU_0016]
17 AHU
DHW system
Main system
Heating
Radiant Fraction
0.20
Capacity
0.00 kW
Cooling
Radiant Fraction
0.00
Capacity
unlimited
Humidity Control
Min. % Saturation
0%
Max. % Saturation
100 %
0.30 l/(sm2)
0.00 AC/h
Variation Profile
off continuously
Internal Gains
None
Air Exchanges
Infiltration Non-AC Hours
Type
Infiltration
Variation Profile
NonAC Hours
Adjacent Condition
External Air
0.50 AC/h
Room Type
Room ID
Name
External Ventilation
[LFTS0000]
01 LiftShaft
[LFTS0001]
02 LiftShaft
NCM Activity
[LFTS0002]
03 LiftShaft
Room Conditions
[LFTS0003]
04 LiftShaft
Heating
[LFTS0004]
05 LiftShaft
Profile
off continuously
[LFTS0005]
06 LiftShaft
Setpoint: Constant
19 C
[LFTS0006]
07 LiftShaft
0.00 l/(hpers)
[LFTS0007]
08 LiftShaft
[LFTS0008]
09 LiftShaft
Cooling
Profile
off continuously
[LFTS0009]
10 LiftShaft
Setpoint: Constant
23 C
[LFTS0010]
11 LiftShaft
[LFTS0011]
12 LiftShaft
Model Settings
Solar Reflected Fraction
0.05
[LFTS0012]
13 LiftShaft
1.00
[LFTS0013]
14 LiftShaft
[LFTS0014]
15 LiftShaft
Systems
HVAC System
Main system
[LFTS0015]
16 LiftShaft
Main system
[LFTS0016]
17 LiftShaft
DHW system
Main system
Heating
Radiant Fraction
0.20
Capacity
0.00 kW
Cooling
Radiant Fraction
0.00
Capacity
unlimited
Humidity Control
Min. % Saturation
0%
Max. % Saturation
100 %
0.30 l/(sm2)
0.00 AC/h
Variation Profile
off continuously
Internal Gains
None
Air Exchanges
Lift shaft infiltration
Type
Infiltration
Variation Profile
Infiltration
Adjacent Condition
External Air
1.00 AC/h
Internal Gains
Room Type
External Ventilation
3744.00 W
3744.00 W
NCM Activity
Radiant Fraction
0.22
Room Conditions
Fuel
Electricity
Heating
Variation Profile
Off SmPwr
Profile
off continuously
Setpoint: Constant
19 C
0.00 l/(hpers)
Cooling
AIR EXCHANGES
None
ROOMS USING THIS TEMPLATE
Profile
AC Hours
Room ID
Name
Room ID
Name
Setpoint: Constant
23 C
[FFC10000]
01 Office1N
[FFC30008]
09 Office3S
[FFC20000]
01 Office2E
[FFC40008]
09 Office4W
Model Settings
Solar Reflected Fraction
0.05
[FFC30000]
01 Office3S
[FFC10009]
10 Office1N
1.00
[FFC40000]
01 Office4W
[FFC20009]
10 Office2E
[FFC10001]
02 Office1N
[FFC30009]
10 Office3S
Systems
HVAC System
Main system
[FFC20001]
02 Office2E
[FFC40009]
10 Office4W
Main system
[FFC30001]
02 Office3S
[FFC10010]
11 Office1N
DHW system
Main system
[FFC40001]
02 Office4W
[FFC20010]
11 Office2E
[FFC10002]
03 Office1N
[FFC30010]
11 Office3S
Heating
Radiant Fraction
0.20
[FFC20002]
03 Office2E
[FFC40010]
11 Office4W
Capacity
0.00 kW
[FFC30002]
03 Office3S
[FFC10011]
12 Office1N
[FFC40002]
03 Office4W
[FFC20011]
12 Office2E
Cooling
Radiant Fraction
0.00
[FFC10003]
04 Office1N
[FFC30011]
12 Office3S
Capacity
unlimited
[FFC20003]
04 Office2E
[FFC40011]
12 Office4W
[FFC30003]
04 Office3S
[FFC10012]
13 Office1N
Humidity Control
Min. % Saturation
0%
[FFC40003]
04 Office4W
[FFC20012]
13 Office2E
Max. % Saturation
50 %
[FFC10004]
05 Office1N
[FFC30012]
13 Office3S
[FFC20004]
05 Office2E
[FFC40012]
13 Office4W
0.55 l/(sm2)
[FFC30004]
05 Office3S
[FFC10013]
14 Office1N
0.00 AC/h
[FFC40004]
05 Office4W
[FFC20013]
14 Office2E
Variation Profile
AC Hours
[FFC10005]
06 Office1N
[FFC30013]
14 Office3S
Internal Gains
[FFC20005]
06 Office2E
[FFC40013]
14 Office4W
[FFC30005]
06 Office3S
[FFC10014]
15 Office1N
3744.00 W
[FFC40005]
06 Office4W
[FFC20014]
15 Office2E
3744.00 W
[FFC10006]
07 Office1N
[FFC30014]
15 Office3S
Radiant Fraction
0.45
[FFC20006]
07 Office2E
[FFC40014]
15 Office4W
Fuel
Electricity
[FFC30006]
07 Office3S
[FFC10015]
16 Office1N
Variation Profile
[FFC40006]
07 Office4W
[FFC20015]
16 Office2E
Dimming Profile
on continuously
[FFC10007]
08 Office1N
[FFC30015]
16 Office3S
[FFC20007]
08 Office2E
[FFC40015]
16 Office4W
90.00 W/P
[FFC30007]
08 Office3S
[FFC10016]
17 Office1N
60.00 W/P
[FFC40007]
08 Office4W
[FFC20016]
17 Office2E
Occupant Density
25.00 people
[FFC10008]
09 Office1N
[FFC30016]
17 Office3S
Variation Profile
Off Ppl
[FFC20008]
09 Office2E
[FFC40016]
17 Office4W
INTERNAL GAINS
Room Type
External Ventilation
9774.00 W
9774.00 W
NCM Activity
Radiant Fraction
0.45
Room Conditions
Fuel
Electricity
Heating
Variation Profile
Dimming Profile
on continuously
Profile
off continuously
Setpoint: Constant
19 C
0.00 l/(hpers)
Cooling
90.00 W/P
60.00 W/P
Profile
AC Hours
Occupant Density
65.00 people
Setpoint: Constant
23 C
Variation Profile
Off Ppl
Model Settings
0.05
9774.00 W
1.00
9774.00 W
Radiant Fraction
0.22
Systems
HVAC System
Main system
Fuel
Electricity
Main system
Variation Profile
Off SmPwr
DHW system
Main system
Heating
AIR EXCHANGES
Infiltration NonAC Hours
Radiant Fraction
0.20
Type
Infiltration
Capacity
0.00 kW
Variation Profile
NonAC Hours
Adjacent Condition
External Air
0.50 AC/h
Cooling
Radiant Fraction
0.00
Capacity
unlimited
ROOMS USING THIS TEMPLATE
Humidity Control
Min. % Saturation
0%
Room ID
Name
Max. % Saturation
50 %
[FFC50000]
01 Office5C
[FFC50001]
02 Office5C
0.55 l/(sm2)
[FFC50002]
03 Office5C
0.00 AC/h
[FFC50003]
04 Office5C
Variation Profile
AC Hours
[FFC50004]
05 Office5C
[FFC50005]
06 Office5C
[FFC50006]
07 Office5C
[FFC50007]
08 Office5C
[FFC50008]
09 Office5C
[FFC50009]
10 Office5C
[FFC50010]
11 Office5C
[FFC50011]
12 Office5C
[FFC50012]
13 Office5C
[FFC50013]
14 Office5C
[FFC50014]
15 Office5C
[FFC50015]
16 Office5C
[FFC50016]
17 Office5C
Name
[PNTR0000]
01 Pantry
[PNTR0001]
02 Pantry
[PNTR0002]
03 Pantry
[PNTR0003]
04 Pantry
[PNTR0004]
05 Pantry
[PNTR0005]
06 Pantry
[PNTR0006]
07 Pantry
[PNTR0007]
08 Pantry
[PNTR0008]
09 Pantry
[PNTR0009]
10 Pantry
[PNTR0010]
11 Pantry
[PNTR0011]
12 Pantry
[PNTR0012]
13 Pantry
[PNTR0013]
14 Pantry
[PNTR0014]
15 Pantry
[PNTR0015]
16 Pantry
[PNTR0016]
17 Pantry
Room Type
Room ID
Name
External Ventilation
[STR_0000]
01 Stair
[STR_0001]
02 Stair
NCM Activity
[STR_0002]
03 Stair
ROOM CONDITIONS
[STR_0003]
04 Stair
Heating
[STR_0004]
05 Stair
Profile
off continuously
[STR_0005]
06 Stair
Setpoint: Constant
19 C
[STR_0006]
07 Stair
0.00 l/(hpers)
[STR_0007]
08 Stair
[STR_0008]
09 Stair
Cooling
Profile
off continuously
[STR_0009]
10 Stair
Setpoint: Constant
23 C
[STR_0010]
11 Stair
[STR_0011]
12 Stair
Model Settings
Solar Reflected Fraction
0.05
[STR_0012]
13 Stair
1.00
[STR_0013]
14 Stair
[STR_0014]
15 Stair
SYSTEMS
HVAC System
Main system
[STR_0015]
16 Stair
Main system
[STR_0016]
17 Stair
DHW system
Main system
Heating
Radiant Fraction
0.20
Capacity
0.00 kW
Cooling
Radiant Fraction
0.00
Capacity
unlimited
Humidity Control
Min. % Saturation
0%
Max. % Saturation
100 %
0.30 l/(sm2)
0.00 AC/h
Variation Profile
AC Hours
INTERNAL GAINS
Fluorescent Lighting : Stairs Lighting
Max Sensible Gain
144.00 W
144.00 W
Radiant Fraction
0.45
Fuel
Electricity
Variation Profile
on continuously
Dimming Profile
on continuously
AIR EXCHANGES
None
Room Type
Room ID
Name
External Ventilation
[TLT_0000]
01 Toilet
[TLT_0001]
02 Toilet
NCM Activity
[TLT_0002]
03 Toilet
Room Conditions
[TLT_0003]
04 Toilet
Heating
[TLT_0004]
05 Toilet
Profile
off continuously
[TLT_0005]
06 Toilet
Setpoint: Constant
19 C
[TLT_0006]
07 Toilet
0.00 l/(hpers)
[TLT_0007]
08 Toilet
[TLT_0008]
09 Toilet
Cooling
Profile
off continuously
[TLT_0009]
10 Toilet
Setpoint: Constant
23 C
[TLT_0010]
11 Toilet
[TLT_0011]
12 Toilet
Model Settings
Solar Reflected Fraction
0.05
[TLT_0012]
13 Toilet
1.00
[TLT_0013]
14 Toilet
[TLT_0014]
15 Toilet
Systems
HVAC System
Main system
[TLT_0015]
16 Toilet
Main system
[TLT_0016]
17 Toilet
DHW system
Main system
Heating
Radiant Fraction
0.20
Capacity
0.00 kW
Cooling
Radiant Fraction
0.00
Capacity
unlimited
Humidity Control
Min. % Saturation
0%
Max. % Saturation
100 %
0.00 l/(sm2)
0.00 AC/h
Variation Profile
AC Hours
Internal Gains
Fluorescent Lighting : Toilet Lights Core
Max Sensible Gain
800.00 W
800.00 W
Radiant Fraction
0.45
Fuel
Electricity
Variation Profile
AC Hours
Dimming Profile
on continuously
Air Exchanges
Infiltration Non-AC Hours
Type
Infiltration
Variation Profile
NonAC Hours
Adjacent Condition
External Air
0.50 AC/h
Room Type
Room ID
Name
External Ventilation
[WLKW0000]
01 Walkway
[WLKW0001]
02 Walkway
NCM Activity
[WLKW0002]
03 Walkway
Room Conditions
[WLKW0003]
04 Walkway
Heating
[WLKW0004]
05 Walkway
Profile
off continuously
[WLKW0005]
06 Walkway
Setpoint: Constant
19 C
[WLKW0006]
07 Walkway
0.00 l/(hpers)
[WLKW0007]
08 Walkway
[WLKW0008]
09 Walkway
Cooling
Profile
AC Hours
[WLKW0009]
10 Walkway
Setpoint: Constant
23 C
[WLKW0010]
11 Walkway
[WLKW0011]
12 Walkway
Model Settings
Solar Reflected Fraction
0.05
[WLKW0012]
13 Walkway
1.00
[WLKW0013]
14 Walkway
[WLKW0014]
15 Walkway
Systems
HVAC System
Main system
[WLKW0015]
16 Walkway
Main system
[WLKW0016]
17 Walkway
DHW system
Main system
Heating
Radiant Fraction
0.20
Capacity
0.00 kW
Cooling
Radiant Fraction
0.00
Capacity
unlimited
Humidity Control
Min. % Saturation
0%
Max. % Saturation
50 %
0.30 l/(sm2)
0.00 AC/h
Variation Profile
AC Hours
Internal Gains
Fluorescent Lighting : Lobby Lighting
Max Sensible Gain
1700.00 W
1700.00 W
Radiant Fraction
0.45
Fuel
Electricity
Variation Profile
Lobby Lights
Dimming Profile
on continuously
Air Exchanges
Infiltration Non-AC Hours
Type
Infiltration
Variation Profile
NonAC Hours
Adjacent Condition
External Air
0.50 AC/h
Total shading
coefficient
(glazed only)
No. of
rooms
ID
Description
Roof
FROOF2
0.522
187
Ceiling
CCR101
2.283
187
External Wall
STD_WAL2
3.179
187
Internal Partition
IWP1B
1.965
187
Ground Floor
STD_FLO2
0.821
187
Door
DOOR
wooden door
2.194
External Glazing
GDPK6
5.322
0.779
68
Internal Glazing
GSP4I
3.689
1.006
Rooflight
RGDPK6
2.103
0.736
END OF CHAPTER 6
CHAPTER
OPTIMISING
THE AIR-SIDE
AIR-CONDITIONING
SYSTEM
OPTIMISING
THE AIR-SIDE
AIR-CONDITIONING
SYSTEM
INTRODUCTION
The air-side air-conditioning system consists of
the supply air, return air, ducts, diffusers, fresh
air intake systems, air filters, cooling coils, motors
and fans. The combination of air filter, cooling
coil, fan and motor is commonly known as an Air
Handling Unit (AHU) or Fan Coil Unit (FCU). An
AHU is a larger system that is typically installed
on each floor inside an AHU room, while a FCU is
a description used for smaller units of AHU that
are installed within the ceiling plenum, ceiling or
are wall mounted.
The intent of the information provided in this
chapter is to promote energy efficiency on the
air-side air-conditioning equipment by providing
an estimate of the energy efficiency potential in
air-side optimisation based on case studies of a
typical office building scenario. It is hoped that
by providing the energy reduction potential,
readers of this chapter will be able to design and
implement systems of higher efficiency by being
able to gauge the potential efficiency gains on the
air-side system.
The Active Design guideline is focused on
providing the fundamentals of energy efficiency in
buildings. Therefore, this chapter only addresses
Constant Air Volume (CAV) and Variable Air
Volume (VAV) systems and will not address
This chapter also provides estimates of building energy index (BEI) reduction for each energy efficiency
feature assessed based on the test model described. These estimates of energy reduction in this chapter
should be used as a first round guesstimate to evaluate the financial feasibility of any proposed energy
efficiency feature as described in this chapter. These results are provided for designers and building owners
to make quick decisions and to evaluate if such features are worth the effort to be investigated further by
the design team.
The actual BEI reduction on a specific building will likely vary from the numbers provided here as the actual
building operational scenario will not be exactly the same as the simulation case scenario. Variations
on passive design features such as window-to-wall ratios, windows, wall and roof properties, occupant
density, operational hours and active design features such as the number of chillers, pump efficiencies,
fan efficiencies, static pressure, etc. will cause the predicted BEI in this chapter to be different from the
actual building scenario. In addition, the predicted BEI reduction is also highly dependent on the sequence
implementation of energy efficient features in a building. For example, if the building already has a very
efficient chiller, the reduction of lighting power density will not provide as significant a reduction on chiller
energy used, compared to a case with inefficient chillers.
Conducting energy simulations on buildings can be very time consuming, therefore a guideline such as this
is required to fill the gap to allow building designers to make quick decisions on the building design and to
proceed with further investigations when deemed necessary.
Finally, it is recommended to test the actual building design performance on the actual building being
designed, using building energy simulation tools such as IES <VE>, DesignBuilder, Equest, Trnsys, TAS,
EnergyPlus, HAP-2, etc. whenever feasible for a project. Such software will help to establish the exact
potential efficiency gains on the building based on the actual design proposal. Experienced energy modelers
will be able to provide realistic assumptions and input data into the simulation engine to provide fairly
accurate results for the building. Conversely, inexperienced energy modelers may use assumptions that are
incorrect and provide results that may be unrealistically high or low.
It has also been advised that the provision of BEI reduction in this chapter for each energy efficiency feature
may be misleading to the industry and it has been advised not to provide these estimates to the industry.
However, it is the authors opinion that the absence of such rule-of-thumb information for the building
industry in Malaysia is one of the key obstacles for the industry to practice energy efficiency in buildings. In
addition, the absence of such rule-of-thumb BEI reduction in the industry has also led to the propagation
of design myths about the practice of energy efficiency in buildings. Many of these industry myths are
not supported by actual facts and data, but mostly by the gut feelings of experienced design engineers,
incomplete data and rumours among practitioners.
It is hoped that the provision of these case study results will challenge both inexperienced and experienced
design engineers to re-examine some of the industry myths, to pay attention to the actual fundamentals
engineering and to make proper engineering evaluations by conducting their own investigations before
accepting industry rumours as the holy truth.
KEY RECOMMENDATIONS
1
qa =
Where:
qa
Htotal sensible
Cp
=
=
=
=
=
Htotal sensible
Cp T
In this chapter, it was assumed that the space peak sensible cooling load is already optimised and is a fixed value. The
space design temperature is normally fixed around 23C or 24C depending on the comfort condition that it is designed
for, leaving the design supply air temperature as the only design parameter that can be varied by the designer. Higher
design supply temperature reduces and increases the supply air flow rate. Lower design off-coil temperature increases
and reduces the supply air flow rate.
The fan power equation is provided below as Equation 7.2 below.
EQUATION 7.2
qa x P
From Equation 7.2 above, it can be seen that a higher supply air flow rate increases fan power, while a lower air flow rate
reduces fan power. However, a lower supply air flow rate also increases moisture (latent heat) removal by the cooling
coil that will increase the energy consumption of the chiller due to the additional latent heat removed by the cooling coil.
Finally, the supply air temperature is required to be compared against the room dew point temperature. If the supply air
temperature is lower than the room dew point temperature, condensation will occur at the supply air outlet diffusers.
Interestingly, the room dew point temperature is also a function of the supply air off-coil temperature. The lower the offcoil temperature, the more moisture would be removed from the supply air, thereby reducing the moisture content in the
air-conditioned room, reducing its dew point temperature.
Reduces
Increases fan energy and leads to a higher sensible heat load from the
fan due to higher flow rate.
Increases cost for fan and motor due to higher flow rate required.
Figure 7.1 | Total Building Energy Index (BEI) of a CAV system
at Different Design Supply Air TemperatureS
180
175
170
kWh/m2.year
SIMULATION
STUDIES
165
160
155
150
6
10
11
12
13
14
15
16
The simulation results showed that in a CAV system, reducing the design offcoil temperature improves the overall efficiency of the building. This indicates
that it is more important to keep the fan power as low as possible rather
than trying to reduce the latent heat removal in a building via a high off-coil
temperature setup.
From Figure 7.1 above, the optimum design off-coil air temperature of a CAV
system is shown to be 8C. However, the supply air temperature at design offcoil of 8C is below the room dew point temperature and will therefore cause
condensation at the outlet diffusers. The limiting factor of reducing the design
off-coil temperature to optimise energy efficiency on a CAV system is found
to be the risk of condensation at outlet diffusers. Further analysis showed that
the lowest possible design off-coil temperature for a CAV system is 11C (in
a draw-through AHU configuration) without condensation happening at the
outlet diffusers.
It is important to take note that the cooling coil required to provide lower off-coil temperatures will be larger. The increase
of cooling coil costs should be factored in to compute the financial payback study for the implementation of this design
feature. It is also important to consider the need for cleaning access to large cooling coils. Cleaning of cooling coils is
addressed in ASHRAE 62.1 (2007), Section 5.12.2, where it states the following:
Individual finned-tube coils or multiple finned-tube coils in series without adequate intervening access space(s) of at least 18 in.
(457 mm) shall be selected to result in no more than 0.75 in. w.c. (187 Pa) combined pressure drop when dry coil face velocity is
500 fpm (2.54 m/s). Exception: When clear and complete instructions for access and cleaning of both upstream and downstream
coil surfaces are provided.
Please note that the heat gained from the energy used to move the fluid through the pipes will cause the chilled water
temperature to be higher than 6.67C when it finally reaches the cooling coils in a building. In addition, any conduction
heat gain along the pipe distance will further increase the chilled water supply temperature. The simulation study made
for this chapter ignored conduction heat gained by pipes as per the modelling recommendation of ASHRAE 90.1 (2007).
Therefore, it is important that the sizing of the cooling coil should account for these potential increases in chilled water
supply temperature.
Figure 7.1 can also be used as a quick approximation of the potential savings of CAV system between two design off-coil
temperatures as shown in the calculation example below.
CALCULATION EXAMPLE
How much energy can be saved in a CAV system with fixed chilled water supply temperature if the design
off-coil temperature is reduced from 13.5C to 11C? The building GFA is 55,000 m2.
The BEI at design off-coil temperature of 13.5C is computed using the curve fit equation shown the trend line
in Figure 7.1 on the previous page.
The BEI at design off-coil temperature of 13,5C is:
BEI = 0.2395(13.5)2 - 3.1558(13.5) + 171.39 = 172.4 kWh/m2.year
The BEI at design off-coil temperature of 11C is:
BEI = 0.2395(11)2 - 3.1558(11) + 171.39 = 165.7 kWh/m2.year
Approximate BEI reduction = 172.4 165.7 = 6.7 kWh/m2.year
Approximate energy saving = 6.7 kWh/m2.year x 55,000 m2 = 368.5 MWh/year
Assuming a fixed electricity tariff of RM 0.43 per kWh (TNB, 2013, Tariff B for commercial building)
Approximated running cost saving per year is: 368,500 kWh/year * RM 0.43/kWh = RM 158,500 per year
This saving should then be compared to the additional cost of the cooling coil needed to reduce the design
off-coil temperature from 13.5C to 11C for computation of payback and rate of return.
*This estimate is based on the simulated model. The actual savings provided by the actual building may differ from
this output. This financial estimate calculation is provided to give an approximate rule-of-thumb for quick estimates
during the conceptual stage to make a quick decision if such a design feature should be considered.
AHU
Chiller
90
80
70
60
kWh/m2.year
50
40
30
20
10
0
7
10
11
12
13
14
15
16
180
6.7C
175
6.7C
13.7C
Fixed Chilled Water
Supply Temperature
6.7C
12.7C
170
6.7C
11.7C
kWh/m2.year
6.7C
6.7C
165
6.7C
8.7C
7.7C
6.7C
160
10.7C
9.7C
6.7C
155
150
6
10
11
12
13
14
15
16
Description
Base Case
Building operates at design condition of 10 m2 per person and 15 W/m2 of equipment load
Case 1
Actual operating occupant and equipment load is reduced by 15% from Base Case.
Air flow rate of CAV system based on peak load design condition.
Case 2
Actual operating occupant and equipment load is reduced by 30% from Base Case.
Air flow rate of CAV system based on peak load design condition.
Case 3
Actual operating Occupant and equipment load reduced by 45% from Base Case.
Air flow rate of CAV system based on peak load design condition.
Case 4
Actual operating Occupant and equipment load reduced by 45% from Base Case.
Air flow rate reduced to match reduced actual operating occupant and equipment load.
180
160
165.6
kWh/m2.year
140
156.4
147.3
138.0
120
100
80
60
40
20
0
0%
15%
30%
45%
This study showed that the energy reduction in the chiller is small, while there are no savings in
fan energy at all in a CAV system that is running at design conditions, even though the cooling
load was reduced significantly (due to the reduction of occupancy and equipment load). The
reduction of the BEI shown in Figure 7.4 above is primarily due to the reduction of equipment
(small power) energy consumption in the building because there is hardly any reduction on the
fan and chiller energy index.
Figure 7.5 below displays the effect of reducing the supply air flow rate of a CAV system
according to the actual cooling load in the building. A very significant building energy reduction
of 8% is achieved, reducing the building energy index (BEI) from 138 to 126 kWh/m2.year, saving
approximately RM155,000 per year on this simulation building model of 17 floors and a GFA of
38,400m2.
Figure 7.5 | Performance of a CAV system at reduced supply air flow rate
to match actual building sensible load at part load
150
8% reduction
140
120
100
80
60
2% reduction
40
45% reduction
20
0
BEI
It was interesting to note that in the simulated model, a reduction of building occupants and
equipment by 45% allowed a reduction of 20% of the supply air flow rate. Modelling the
reduction of 20% of the air flow rate reduces the fan energy by 45%. The fan energy reduction is
from a combined effect of a reduction in total pressure loss and a lower air flow rate (this double
reduction effect is known as the Fan Affinity Law). The fan energy reduction also leads to a
further reduction of 2% in chiller energy consumption due to the lower heat energy produced by
the fan. The compounding effects of reducing the supply air flow rate by 20% in this model lead
to a very significant total building energy reduction of 8%.
Based on this result, it is recommended to provide CAV system with a variable speed drive
(VSD) for all major AHUs in a building, especially for buildings where there is a possibility that
the actual building occupancy may be significantly lower than the design assumptions. This
would make it possible for an energy manager (or facility manager or a commissioning agent) of
the building to fine-tune the AHU system based on the actual operating heat load on site.
A reduction of the supply air flow rate in a CAV system may require rebalancing work to be
conducted again on the duct network to ensure that the supply air is evenly distributed. The need
to rebalance the air flow from diffusers may be minimised by providing a duct network design
that would cater for minor changes in air flow rate in a CAV system.
kWh/m2.year
160
y = -0.05x3 + 2.3284x2 - 33.644x + 314
R2 = 0.97976
150
140
130
120
8
10
11
12
13
14
15
16
Chiller
AHU+Chiller
80
70
60
kWh/m2.year
Dry Bulb
(C)
Relative
Humidity
(%)
Moisture
Content
(g/kg)
30
100
6.7
20
100
7.2
10
10
100
7.7
11
100
8.2
12
100
8.8
13
100
9.4
14
100
10.0
15
100
10.7
50
40
10
11
12
13
14
15
16
BEI
Units
165.6
kWh/m2.year
158.6
kWh/m2.year
7.1
kWh/m2.year
4.3%
Percentage
% VAV improvement
The 2nd scenario, presented in Table 7.3 below, is where both the CAV and VAV systems were designed for full load
conditions, however during operation, the actual occupancy in the building is 45% lower than the design condition (45%
reduction is made for both occupancy and small power during operation). The advantage of a VAV system over the
CAV system increased marginally in this case by 0.4 to 7.5 kWh/m2.year from the 1st case scenario. As expected, this
indicates that a VAV system reduces more energy than a CAV system when a building is operating at part load.
Table 7.3 | Building BEI of CAV vs. VAV system operating at 45% Occupancy,
while flow rate IS maintained at design conditionS of full occupancy
45% Reduction in Occupancy
BEI
Units
138.0
kWh/m2.year
130.4
kWh/m2.year
7.5
kWh/m2.year
5.5%
Percentage
% VAV improvement
The 3rd scenario, presented in Table 7.4 below, is where the air flow rate of a CAV system is reduced to match the actual
operating conditions of peak sensible load of the building with a 45% reduction in occupancy, while the VAV system is
not changed from its design condition. The VAV system is not changed from its design condition because it is likely that a
VAV system, once installed, is assumed to be self-regulating and the facility manager may think that it is not necessary
to recalibrate a VAV system based on actual operating conditions. The result of this scenario showed that it is possible
for a CAV system to have lower energy consumption than a VAV system, by 4.0 kWh/m2.year, when it is recalibrated to
the actual building load that is lower than the design assumption.
Table 7.4 | Building BEI of CAV vs. VAV system operating at 45% Occupancy, where flow rate is
maintained at design conditions of full occupancy for VAV system but flow rate is reduced
for CAV system to match the lower peak cooling load of the building at reduced occupancy
BEI
Units
130.4
kWh/m2.year
126.4
kWh/m2.year
4.0
kWh/m2.year
3.1%
Percentage
Offices
Toilet
Offices
Pantry
Walkway
AHU
Offices
Lift Shaft
Offices
Offices
Stairs
Offices
Offices
One AHU system (i.e. fan) was modelled to be delivering the supply air into these 7 zones. Refer to Chapter 6 for details.
The air flow rate for both the CAV and VAV system was sized according to the peak flow rate for these 7 zones. On the
CAV system, the flow rate is fixed for these 7 different zones, and the supply air temperature is regulated based on the
average return air temperature, while on the VAV system, the supply air temperature is fixed and each VAV zone air
temperature is regulated by the amount of supply air flow rate. The temperature set point of both systems was fixed at
23C (or a minimum of 22C and a maximum of 24C).
A comparison of CAV and VAV air temperatures of the offices showed that a CAV system has a much wider variation of
air temperatures compared to a VAV system. This result is more or less expected due to the fact that a VAV system can
control the air temperature in each zone independently, while a CAV system controls the return air temperature, which
is the average of all 7 zones air temperatures.
Figure 7.9 | Simulated Air Temperature Distribution in the Office space of a CAV and VAV
system during Occupancy Hours at different design off-coil temperatures
SPACE AIR TEMPERATURE OF VAV SYSTEM
80%
Percentage of AC Hours
Percentage of AC Hours
60%
40%
20%
0%
<22.00
22.00 to
23.00
23.00 to
24.00
24.00 to
25.00
25.00 to
26.00
26.00 to
27.00
80%
60%
40%
20%
0%
27.00 to
28.00
<22.00
22.00 to
23.00
23.00 to
24.00
8C
9C
10C
11C
12C
24.00 to
25.00
25.00 to
26.00
26.00 to
27.00
27.00 to
28.00
13C
14C
15C
8C
9C
10C
11C
12C
13C
14C
15C
The results also showed that the air temperature in the office space is not influenced much by the design off-coil
temperature. The controls provided are generally adequate to maintain the desired air temperature in the office space
for the various tested design off-coil temperatures. However, it is shown in Figure 7.10 below that the design off-coil
temperature has a significant influence on the office spaces relative humidity, especially on a CAV system. From the
results of these studies, it is recommended not to design off-coil temperatures of 13C or higher for a CAV system,
because it will lead to a relative humidity that exceeds 70% (the recommended limit by MS 1525) for a significant
percentage of the occupancy hours. Fortunately, it was shown earlier that a CAV system is more efficient when
operating at lower design off-coil temperatures, which would also help in keeping the relative humidity within the
recommended limits.
The office space relative humidity for a VAV system is shown to remain below 70% even with design off-coil temperatures
as high as 15C. This is because in a VAV system, the off-coil temperature will always be fixed at the design condition
of 15C, while in a CAV system, the off-coil temperature is higher than the design temperature of 15C during part-load
conditions.
Figure 7.10 | Simulated Air Relative Humidity Distribution in the Office space of a CAV and VAV
system during Occupancy Hours at different design off-coil temperatures
SPACE RELATIVE HUMIDITY OF VAV SYSTEM
100%
Percentage of AC Hours
Percentage of AC Hours
80%
60%
40%
20%
0%
<50.00
50.00 to
60.00
60.00 to
70.00
70.00 to
80.00
80.00 to
90.00
90.00 to
100.00
100%
80%
60%
40%
20%
0%
<50.00
50.00 to
60.00
60.00 to
70.00
8C
9C
10C
11C
12C
70.00 to
80.00
80.00 to
90.00
90.00 to
100.00
13C
14C
15C
8C
9C
10C
11C
12C
13C
14C
15C
Mandatory Preventative Maintenance Standard, August 1999, Integrated Workplace Solutions (IWS), Vancouver, British Columbia.
(Vo2 Vi2)
Where:
170
y=0.0081x +172.81
R2 = 0.98556
169
168
167
166
165
164
0
200
400
600
800
1000
1200
1400
From the simulation case studied, it was estimated that the impact on BEI due to the change in
Fan Total Pressure is:
EQUATION 7.5
In short, this case study showed that the building energy index increases by 2 kWh/m2.year for
an increase of 100 Pa Fan Total Pressure. An increase of 1,000 Pa (4 w.g.) will increase BEI of
this case study by 20 kWh/m2.year.
166
164
y = 0.0201x + 143.44
R2 = 0.99987
162
160
158
156
154
152
0
200
400
600
800
1000
1200
1400
It should be highlighted that these cooling loads and BEI reduction estimates are provided for
the simulated case scenario of a typical office building, operating from 9am to 5pm weekdays.
These estimates are provided for air-conditioning designers and building owners to make a quick
estimate of potential savings from the implementation of fan total pressure reduction. Buildings
that operate longer hours will provide higher BEI reductions than the estimates shown here,
however these buildings would have a higher BEI in the first place. In summary, it becomes more
important to have efficient equipment in buildings that operate for longer hours.
FEt = Fe x Me x Be x Ve
Where:
FEt = Fan Total Efficiency (%)
Fe = Fan Efficiency (%)
Me = Motor Efficiency (%)
Be = Fan Belt Efficiency (%) Where, Be = 100%, if fan is direct driven by the motor
Ve = Variable Speed Drive Efficiency (%) Where, Ve = 100%, if not used
The simulation study on the impact of Fan Total Efficiency on cooling loads and energy
consumption yielded a polynomial curve fit. However, to keep it simple, a straight-line estimate
is provided instead, while providing a decent coefficient of determination (R 2) of 0.986. The
impact of Fan Total Efficiency on the cooling coil load can be estimated using Equation 7.7 as
shown below:
EQUATION 7.7
168.0
y = -8.7313x + 172.81
R2 = 0.98556
167.5
167.0
166.5
166.0
165.5
165.0
40%
45%
50%
55%
60%
65%
70%
75%
80%
85%
90%
The impact of Fan Total Efficiency on the BEI can be estimated using Equation 7.8 as shown below:
EQUATION 7.8
From this case study, the BEI reduces by approximately 2.1 kWh/m2.year for an increase of 10%
Fan Total Efficiency. A 30% increase in Fan Total Efficiency will reduce the BEI by 6.3 kWh/m2.year
on the case study building.
160
Y = -20.649X + 172.21
R2 = 0.98098
159
158
157
156
155
154
40%
45%
50%
55%
60%
65%
70%
75%
80%
85%
90%
No CO2 sensor
167.0
164.7
Difference
2
3
2.3
In terms of energy efficiency, the benefit of using a demand controlled fresh air intake becomes more significant when
the actual building occupant density is below the design occupant density. The estimated BEI savings due to the use
of a CO2 sensor at different percentages of occupancy is shown in Figure 7.15 below and Equation 7.9 is provided for
a quick estimation of the BEI reduction due to the use of a CO2 sensor for the tested case building scenario.
EQUATION 7.9
BEI = 5.26 x Oc
Where:
BEI = Change of Building Energy Index (kWh/m2.year)
Oc = Change in Occupant Density from Design Scenario (10 m2/person) (%)
The following rule-of-thumb is derived from this study on the use of a CO2 sensor; for every 10% reduction of occupant
density from the design scenario of 14 m2/person, the BEI reduces by 0.5 kWh/m2.year.
BEI (kWh/m2.year)
156.5
y = 5.2557x + 151.96
R2 = 0.99737
156.0
155.5
155.0
154.5
154.0
153.5
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Finally, the energy saved due to the use demand controlled fresh air intake system is also closely linked to the CO2
set point level. Figure 7.16 on the next page shows the results of different CO2 set points in the case where the actual
building occupancy is only at 40% of the design occupancy (i.e. 25 m2/person instead of 10 m2/person). The sparsely
occupied building does not increase the energy consumption at all by reducing the CO2 level from 900ppm to 700ppm
because the low number of people in the building has kept the CO2 level below 700ppm from the minimum fresh air
supplied (based on ASHRAE area requirements). However, reducing the CO2 set point below 700ppm increases the
BEI significantly. It can be seen from Figure 7.16 on the next page that in a sparsely occupied building, that below the
700ppm set point, every additional 100ppm reduction of the CO2 set point increases the BEI by 3.9 kWh/m2.year.
Figure 7.16 | Impact on BEI based on CO2 set point in a sparsely occupied
building (40% Design Occupancy)
163
162
161
BEI (kWh/m2.year)
160
159
158
157
156
155
154
153
400
500
600
700
800
900
1000
Table 7.6 | BEI (kWh/m2.year) with and without CO2 sensor at various building
occupancy LEVELS
Description
No CO2 Sensor
Design Condition
Design Condition
Add 50% FA
Add 100% FA
Full Occupancy
157.3
158.6
164.1
169.8
80% Occupancy
156.1
157.6
162.8
168.5
60% Occupancy
155.1
156.6
161.7
167.4
40% Occupancy
154.1
155.6
160.7
166.1
Table 7.6 shows that if the fixed fresh air supply system is supplying 50% more fresh air than is
specified by the ASHRAE 62.1 (2007) requirement, the savings from the use of a demand controlled
fresh air intake increases to 6.7 kWh/m2.year. If the fixed fresh air supply system is supplying 100%
more fresh air than specified by the ASHRAE 62.1 (2007) requirement, the savings from the use of
a demand controlled fresh air intake increases to 12.3 kWh/m2.year. This result indicates that it is
very important to commission a building to ensure that the fixed fresh air intake system is operating
according to the design assumptions. Over-provision of the fresh air intake is shown to be very
expensive. Unfortunately, it is not a common practice to measure the fresh air intake during the
commissioning of buildings in Malaysia. Based on this result, it is strongly recommended that all
buildings in Malaysia should at the very least, measure and tune the fresh air intake into the building
during the commissioning stage or implement CO2 sensors to regulate the fresh air intake.
156
y = 7.9179x + 156.87
R2 = 0.99972
154
152
150
0%
10%
20%
30%
40%
50%
60%
70%
80%
Figure 7.17 shows that the BEI of the simulated building case study would reduce
at a rate of 0.8 kWh/m2.year for each 10% efficiency gain of both sensible and
latent heat recovery between the exhaust air and fresh air intake.
Figure 7.18 | Relationship between BEI and Infiltration Rate from the use
of Heat Recovery at 55% efficiency of both sensible and latent heat
5.0
4.0
3.0
y = -1.4933 x 5.0107
R2 = 0.99578
2.0
1.0
0.0
0
0.5
0.1
1.5
2.0
2.5
Figure 7.18 displays the results of a heat recovery system with 55% efficiency on both sensible
latent heat exchanges at various infiltration rates in the building. The higher infiltration rate in
the building reduces the need for fresh air supply from the system, i.e. less fresh air is treated by
the heat recovery system. While a higher exfiltration rate from the building reduces the available
exhaust air for the heat exchanger to pre-cool and pre-dry the fresh air intake, reducing its
effectiveness. In short, these results show that it is important to keep the building air-tight to
increase benefits from a heat recovery system.
SUMMARY
This chapter is a set of simulation case studies to provide the approximate impact of optimising
the air-side air-conditioning system on the peak cooling load and energy consumption in a
typical office building scenario. However, it should be noted that the rules-of-thumb provided in
this chapter is based on the simulation studies of a standard base case office building scenario
as described in Chapter 6.
There may be instances that certain buildings may not behave like this standard base case
building. In such cases the energy savings predicted in this chapter may under or over achieve.
In such instances, it is recommended that designers engage a building simulation professional
to model the building as it is. This would test the feasibility of the ideas presented in this chapter
based on the actual building designed.
On this note, it is recommended that building design engineers should pick up building energy
modelling skills to enhance their design capabilities for the building industry. Building energy
simulation tools are much easier to use today than it was 10 years ago. Software such as IES
<Virtual Environment>, DesignBuilder, TAS, Trnsys, Visual-DOE, Equest and HAP are fairly well
known dynamic energy simulation softwares in the market place today.
It is also important to note that there are hundreds, if not thousands of input parameters in a
complex simulation model. Therefore, it is important to engage experienced energy modelers to
obtain accurate results. The term GIGO for garbage in, garbage out is applicable here.
END OF CHAPTER 7
CHAPTER
OPTIMISING THE
WATER-SIDE
AIR-CONDITIONING
SYSTEM
OPTIMISING THE
WATER-SIDE
AIR-CONDITIONING
SYSTEM
INTRODUCTION
The water-side air-conditioning system consists of the chilled water distribution system, chiller,
condenser water distribution system and cooling tower. The current version of the Malaysian Standard,
MS 1525 (2007), for non-residential buildings, provides a minimum performance requirement for
chillers but it does not provide any minimum performance or recommendations for the chilled water
distribution system, condenser water distribution system and cooling tower performance. The current
MS 1525 (2007) only contains minimum performance requirements on the chiller Coefficient of
Performance (COP) for the water-side air-conditioning system.
Figure 8.1 | Schematic of Typical Air-Conditioning System in Malaysia
CHW Pump
O/A Intake
Damper
Evaporator
Compressor
Condenser
Cooling Coil
CCW
Pump
Cooling Tower
Fan
Recycle
Air Damper
Filter
Spill Air Damper
This chapter is an energy simulation study of the energy saving potential by optimising the
efficiency of the water-side air-conditioning equipment. Readers should be aware that the study
conducted for this guideline is based on a typical office building scenario. The energy savings
predicted in this document should only to be used as a general guide for quick decision making
and in most cases should be reasonably accurate. Readers should be cautioned against using this
document as a performance guarantee because building simulation studies require hundreds
(and in a detailed model thousands) of input parameters. Therefore, it would be impossible to
provide all possible variations of a building performance in a guideline such as this.
The emphasis of this guideline is to provide rules-of-thumb that are applicable for the Malaysian
climatic zone to optimise the water-side air-conditioning system in large buildings. The key
topics addressed in this chapter are the following:
1. Energy impact of different types of chilled water distribution systems
2. Energy impact of various chilled water supply and return temperatures
3. Energy impact of chilled water pump efficiency
4. Energy impact of chiller types and efficiency
5. Energy impact of condenser flow rate and system efficiency
6. Energy impact of cooling tower temperature set point and system efficiency
7. Pipes and pump installation recommendations
The intent of the information provided in this guideline is to promote an efficient, practical design
that advances standard design practices to achieve cost-effective energy reduction in buildings.
The input assumptions made for this Chapter is based on the building model as described in
Chapter 6 of this guidebook.
KEY RECOMMENDATIONS
From the simulation studies conducted for this chapter, it was found that the following items are
important for an optimised chilled water distribution system:
The term specific pump power is explained on the next page. It is basically a simple way to
understand the most fundamental efficiency rating of a water pumping system. Try to keep this
number as low as possible for energy efficiency.
Variable primary flow was found to be the most efficient system of distributing chilled water,
however the advantage gained is small when specific pump power is low to start with.
All tested high T chilled water supply scenarios were found to be more efficient than standard
T scenarios, however, the high T supply temperature of 5.56C (42F) and return of 14.44C
(58F) was found to increase efficiency without a significant increase in cooling coil size. It is
recommended to conduct a lifecycle analysis, taking into account of the additional cooling coil
cost and space used versus the energy reduction potential for higher T options.
4 Chiller Efficiency
It was found from the case studies conducted for this chapter that an improvement of COP by
1.0 reduces the building energy consumption by approximately 10 kWh/m2.year. In addition, it
is recommended to ensure that VSD chillers are operating at part load conditions to gain the
optimum benefit from it. The advantage of operating VSD chillers at full load condition is only
marginally better than non-VSD chillers.
It was found that reducing the condenser flow rate to 2 gpm/ton (a supply temperature of 36.11C
(97F) and return at 29.44C (85F)) has a higher efficiency than the standard 2.4 gpm/ton (a
supply temperature of 35C (95F) and return at 29.44C (85F)). The energy reduction of the
condenser pump due to the lower flow rate exceeds the energy gained by the chiller due to the
loss of chiller efficiency on all tested specific pump power on the simulated building scenario.
The selection of an efficient cooling tower by its fan energy (kW) use per heat rejection ton
(HRT) is the most fundamental method to improve cooling tower fan efficiency. In addition,
a VSD cooling tower fan was found to provide a significant energy reduction as well. Finally,
upsizing (or downsizing) cooling tower has a minimal impact on net energy efficiency of the
simulated building.
It was observed that most pipe and pump installations in Malaysia do not follow the
recommended straight pipe of 5 to 10 pipe diameter lengths before pump suction. Having a pipe
bend right before the pump suction reduces the pump efficiency significantly. It is recommended
for engineering consultants to be meticulous in the installation details of pipes and pumps by
contractors to ensure long term efficiency and problem-free operation by observing the simple
installation guide as provided at the end of this chapter.
Where:
= Specific Pump Power (W per l/s)
= Fluid Density (Water = 1,000 kg/m3)
= Gravity (9.81 m2/s)
= Pump Total Pressure (m of water)
= Pump Total Efficiency (%)
Since the fluid density and gravity are constants, the pump specific power is only related to pump
total pressure and pump total efficiency.
CHILLED WATER
DISTRIBUTION SYSTEM
Pump power equation is provided as Equation 8.2 below, and is shown to be a factor of chilled
water flow rate, pump total pressure and pump total efficiency, while the fluid density and
gravity is a constant.
EQUATION 8.2
Where:
= Pump Power (kW)
= Flow Capacity (m3/h)
= Fluid Density (kg/m3), Water = 1,000 kg/m3
= Gravity (9.81 m2/s)
= Pump Total Pressure (m of water)
= Pump Total Efficiency (%)
A decrease in flow rate and pump total pressure (head) reduces pump power, while a reduction
in pump total efficiency increases pump power. Therefore, in the interest of energy efficiency, it
is desirable to reduce flow rate and pump total pressure (head), while increasing the pump total
efficiency.
Three (3) types of chilled water distribution systems were tested in this
chapter, these are:
1 Primary Constant
The chilled water is circulated from the chiller to AHU/FCU in the building at a constant flow
rate. A three-way valve is located at the AHU/FCU to divert excess flow back to the return pipe.
This is the conventional way of circulating chilled water in a building because it is the simplest
method to deliver chilled water around the building.
2 Primary/Secondary Variable
This is a system where the chilled water is circulated at a constant flow rate through a primary
loop to the chiller, while a secondary loop is provided with a VSD pump to provide a variable flow
rate as required by the AHU/FCU. In this case, a two-way valve is installed at the AHU/FCU that
closes the valve to increase the pressure in the pipe at part load conditions. The secondary loop
has a pressure sensor that will detect the increase or decrease in pressure in the pipe and send
a signal to the VSD pump to reduce or increase the pump speed to maintain the pressure in the
chilled water pipe. The secondary loop pump power reduces significantly at a reduced flow rate,
following the pump affinitys law.
3 Primary Variable
Improvements in the latest technology allows variable flow through a number of chillers
(unfortunately, not all chillers today allow this technology to be implemented). With the use
of such chillers, it is possible to implement a primary variable flow chilled water distribution
system. Energy reduction in pump power is achieved by allowing a reduction of the chilled water
flow rate during part load. In addition, this system is also cheaper to implement than a primary/
secondary system.
Figure 8.2 | Conventional Primary Only System
Chiller # 3
VSD
Chiller # 2
Automatic Isolation
Valve - Typical
VSD
Chiller # 1
VSD
Primary Pumps
Bypass Value
Typical Coil
Chiller # 3
Chiller # 2
Secondary Pumps
Chiller # 1
VSD
Primary Pumps
VSD
Typical Coil
VSD
SIMULATION STUDIES
In order to study the energy efficiency impact of these various chilled water distribution technologies, the
following set of simulation runs were conducted:
Description
Specific pump power of 545 W per l/s + 10% = 599.5 W per l/s
Primary/Secondary Variable Flow
Primary Constant Pump: assumed 20% of 599.5 = 119.9 W per l/s
Secondary Variable Pump: assumed 80% of 599.5 = 479.6 W per l/s
Specific pump power of 545 W per l/s + 20% = 654 W per l/s
Primary/Secondary Variable Flow
Primary Constant Pump: assumed 20% of 654 = 130.8 W per l/s
Secondary Variable Pump: assumed 80% of 654 = 523.2 W per l/s
Specific pump power of 545 W per l/s + 30% = 708.5 W per l/s
Primary/Secondary Variable Flow
Primary Constant Pump: assumed 20% of 708.5 = 141.7 W per l/s
Secondary Variable Pump: assumed 80% of 708.5 = 566.8 W per l/s
10
Specific pump power of 280 W per l/s + 30% = 364 W per l/s
Primary/Secondary Variable Flow
Primary Constant Pump: assumed 20% of 364 = 72.8 W per l/s
Secondary Variable Pump: assumed 80% of 364 = 291.2 W per l/s
RESULTS
The results of this simulation study showed that at a high specific pump power of 545 W per l/s, a primary
variable system reduces the building energy index (BEI) by 5 kWh/m2.year compared to a primary constant flow
system. Meanwhile a primary/secondary system is shown to reduce between 2.3 to 3.7 kWh/m2.year compared
to a primary constant flow system depending the increase of pumping power required by a primary/secondary
system.
BEI (kwh/m2.year)
Figure 8.4 | BEI Reduction due to Various Chilled Water Pumping SystemS at Specific
Pump Power of 545 W per l/s
161
160
159
158
157
156
155
154
153
152
Base
2.3%
2.0%
1.7%
1.4%
3.1%
Primary
Constant
Primary
Variable
Primary
Secondary
Primary
Secondary
(pump power
add 10%)
Primary
Secondary
(pump power
add 20%)
Primary
Secondary
(pump power
add 30%)
Type of System
Table 8.2 | BEI Reduction due to Various Chilled Water Pumping SystemS at Specific
Pump Power of 545 W per l/s
Case
1
BEI (kWh/
m2.year)
BEI reduction
(kWh/m2.year)
%
Improvement
160.2
Base
Base
Primary Variable
155.1
5.0
3.1%
Primary Secondary
156.5
3.7
2.3%
156.9
3.3
2.0%
157.4
2.8
1.7%
157.8
2.3
1.4%
At a low specific pump power of 280 W per l/s, the primary variable system provided an energy reduction
of 2.6 kWh/m 2.year, while a primary/secondary system provided an energy reduction range between 1.2
to 1.9 kWh/m 2.year.
Table 8.3 | BEI Reduction due to Various Chilled Water Pumping SystemS at Specific
Pump Power of 280 W per l/s
Case
7
BEI (kWh/
m2.year)
BEI reduction
(kWh/m2.year)
%
Improvement
156.2
Base
Base
Primary Variable
153.6
2.6
1.6%
Primary Secondary
154.3
1.9
1.2%
10
155.0
1.2
0.8%
In summary, a primary variable system is the most efficient option among the 3 options studied. It is also
important to note that a primary/secondary system is shown to be more efficient than a primary constant
system in this tested office scenario. Since an office cooling load is fairly consistent daily, it is expected that
a variable flow system will provide an even higher energy reduction in buildings where the cooling load varies
significantly; for example, retail malls usually have low cooling loads during weekdays and high cooling loads
during weekends.
In addition, it was also shown that it is possible for a primary constant system at a low specific pump power to
have a lower BEI than using a primary variable system with a high specific pump power. This shows that it is
possible to design a constant flow pump system with a low specific pump power to be as efficient as a variable
chilled water pump system with a moderate specific pump power.
Building Energy Efficiency Technical Guideline for Active Design | 171
H = 1.16 Q T
Where:
H = Cooling Load (kW)
Q = Chilled Water Volume Flow Rate (m3/h)
T = Temperature Difference (C)
Rewriting it,
EQUATION 8.4
Q =
H
1.16 T
Where:
H = Cooling Load (kW) (~constant at this stage of design)
Q = Water Volume Flow Rate (m3/h), reduces with higher T
SIMULATION STUDIES
The following set of simulation cases were conducted to study the energy efficiency impact of
these various T chilled water flow options:
Table 8.4 | Simulation Case Studies of Various T ScenarioS
Case
Description
Cases below are for a Primary Constant System. Specific pump power remains at 545 W per l/s, assuming
that pipe size will be reduced to maintain same pressure at lower flow rates.
T = 6.67C (12F)
Supply Temperature: 6.67C (44F)
Return Temperature: 13.33C (56F)
Primary Constant System @ 545 W per l/s
T = 7.78C (14F)
Supply Temperature: 6.67C (44F)
Return Temperature: 14.44C (58F)
Primary Constant System @ 545 W per l/s
T = 8.89C (16F)
Supply Temperature: 6.67C (44F)
Return Temperature: 15.56C (60F)
Primary Constant System @ 545 W per l/s
T = 10.00C (18F)
Supply Temperature: 6.67C (44F)
Return Temperature: 16.67C (62F)
Primary Constant System @ 545 W per l/s
T = 8.89C (16F)
Supply Temperature: 5.56C (42F)
Return Temperature: 14.44C (58F)
Primary Constant System @ 545 W per l/s
Cases below changes from a Primary Constant System to a Primary Variable System. Specific pump
power remains at 545 W per l/s, assuming that pipe size will be reduced to maintain same pressure at
lower flow rates.
T = 6.67C (12F)
Supply Temperature: 6.67C (44F)
Return Temperature: 13.33C (56F)
Primary Variable System @ 545 W per l/s
T = 7.78C (14F)
Supply Temperature: 6.67C (44F)
Return Temperature: 14.44C (58F)
Primary Variable System @ 545 W per l/s
T = 8.89C (16F)
Supply Temperature: 6.67C (44F)
Return Temperature: 15.56C (60F)
Primary Variable System @ 545 W per l/s
T = 10.00C (18F)
Supply Temperature: 6.67C (44F)
Return Temperature: 16.67C (62F)
Primary Variable System @ 545 W per l/s
10
T = 8.89C (16F)
Supply Temperature: 5.56C (42F)
Return Temperature: 14.44C (58F)
Primary Variable System @ 545 W per l/s
Cases below reduces Specific Pump Power. This is assuming pipe sizes remain the same as base design.
i.e. no reduction in pipe size, pressure will be lower at lower flow rates.
11
T = 7.78C (14F)
Supply Temperature: 6.67C (44F)
Return Temperature: 14.44C (58F)
Primary Variable System @ 409 W per l/s, pipe sizes same as case 1
12
T = 8.89C (16F)
Supply Temperature: 6.67C (44F)
Return Temperature: 15.56C (60F)
Primary Variable System @ 327 W per l/s, pipe sizes same as case 1
13
T = 10.00C (18F)
Supply Temperature: 6.67C (44F)
Return Temperature: 16.67C (62F)
Primary Variable System @ 259 W per l/s, pipe sizes same as case 1
14
T = 8.89C (16F)
Supply Temperature: 5.56C (42F)
Return Temperature: 14.44C (58F)
Primary Variable System @ 327 W per l/s, pipe sizes same as case 1
Cases below test conditions with a low specific pump power of 280 W per l/s.
15
T = 6.67C (12F)
Supply Temperature: 6.67C (44F)
Return Temperature: 13.33C (56F)
Primary Constant System @ 280 W per l/s
16
T = 8.89C (16F)
Supply Temperature: 5.56C (42F)
Return Temperature: 14.44C (58F)
Primary Constant System @ 280 W per l/s
17
T = 6.67C (12F)
Supply Temperature: 6.67C (44F)
Return Temperature: 13.33C (56F)
Primary Variable System @ 280 W per l/s
18
T = 8.89C (16F)
Supply Temperature: 5.56C (42F)
Return Temperature: 14.44C (58F)
Primary Variable System @ 280 W per l/s, pipe sizes reduced to maintain pressure
19
T = 8.89C (16F)
Supply Temperature: 5.56C (42F)
Return Temperature: 14.44C (58F)
Primary Variable System @ 140 W per l/s, pipe sizes same as case 17
RESULTS
Regardless of the chilled water distribution system in use, increasing the T increases energy
efficiency. This indicates that it is possible to reduce energy consumption while reducing pipe
size, providing a reduction in capital costs as well as running costs. However, designers are
cautioned that there will be an increase in the size of the cooling coil to provide a high T return
temperature. A lifecycle analysis between the reduction of costs in pipes and an increase in
costs of cooling coil should be studied alongside the reduction of energy consumption to
derive the optimum solution for a building.
The energy saved on a primary constant system from the use of a high T chilled water system
is higher than a primary variable system. This is because a primary variable system is already a
more efficient system than a primary constant system.
Figure 8.5 | BEI Relationship with Different T of Chilled Water for a Primary
Constant System
BEI (kwh/m2.year)
162
Base
0.7%
160
1.3%
158
1.7%
1.2%
156
154
152
150
DT 12F
(44/56F)
DT 14F
(44/58F)
DT 16F
(44/60F)
DT 18F
(44/62F)
DT 16F
(42/58F)
Figure 8.5 shows that with a higher T of chilled water, the BEI reduction is higher. It was also
interesting note that reducing the supply chilled water temperature while maintaining the same T
reduces the BEI marginally due to the lower chiller efficiency.
It should also be highlighted that the cooling coil size becomes larger when the temperature of
chilled water supplied is higher, even for the same rate of heat transfer (same T).
Therefore the design selection of supply chilled water temperature and T is a choice between the
cooling coil size (and cost increment) and the savings that are provided by it due to a reduced flow
rate, reduced pump size, pipe size and a reduced BEI.
Figure 8.6 | BEI Relationship with Different T of Chilled Water for a Primary
Variable System
162
BEI (kwh/m2.year)
160
158
156
Base
0.25%
0.45%
0.57%
0.40%
DT 16F
(44/60F)
DT 18F
(44/62F)
DT 16F
(42/58F)
154
152
150
DT 12F
(44/56F)
DT 14F
(44/58F)
Figure 8.7 | BEI Relationship with Different T of Chilled Water for a Primary
Variable System with Pipe Size Designed for a Standard T
162
BEI (kwh/m2.year)
160
158
Base
156
0.7%
1.1%
1.3%
DT 16F
(44/60F)
DT 18F
(44/62F)
154
1.0%
152
150
DT 12F
(44/56F)
DT 14F
(44/58F)
DT 16F
(42/58F)
BEI
(kWh/m2.year)
BEI Reduction
(kWh/m2.year)
% Reduction
C1
160.2
Base
Base
C2
159.0
1.2
0.7%
C3
158.1
2.0
1.3%
C4
157.5
2.7
1.7%
C5
158.2
1.9
1.2%
3.1%
C6
155.1
5.0
Remarks
C7
154.8
5.4
3.4%
C8
154.4
5.7
3.6%
C9
154.3
5.9
3.7%
C10
154.5
5.6
3.5%
C11
154.0
6.1
3.8%
C12
153.4
6.7
4.2%
C13
153.1
7.1
4.4%
C14
153.6
6.6
4.1%
C15
156.2
4.0
2.5%
C16
155.2
4.9
3.1%
C17
153.6
6.6
4.1%
C18
153.4
6.8
4.2%
4.6%
C19
152.7
7.4
100
50 60
110 250
65 75
73 76
300 450
75 80
75 79
460 600
78 82
75 79
700 1000
80 85
78 82
1100 1500
83 87
78 82
1600 2500
83 87
78 83
2600 3600
80 86
3700 4000
82 86
> 5000
80 88
Flow (gpm)
SIMULATION STUDIES
The following set of simulation studies were made to study the impact of chilled water pump efficiency on the BEI:
Table 8.7 | Simulation Cases to Study the Impact of Pump Efficiency and Pump Head
Specific Pump Power
Case
Total Pump
Efficiency
Total Pump
Head
W per l/s
W/gpm
C1
72%
45
613.1
38.7
C2
72%
35
476.9
30.1
C3
72%
25
340.6
21.5
C4
72%
15
204.4
12.9
C5
50%
35
686.7
43.3
C6
60%
35
572.3
36.1
C7
70%
35
490.5
30.9
C8
80%
35
429.2
27.1
RESULTS
Based on the results provided in Figure 8.8 to 8.10 below, it is recommended to use the
term specific pump power to represent the chilled water pump efficiency because it was
found that the BEI has a linear relationship with the specific pump power, while it has
a polynomial relationship with pump efficiency. The specific pump power was already
defined on page 167 and a simplification of the specific pump power formula is made
below for a typical chilled water system:
EQUATION 8.5
Where:
= Specific Pump Power (W per l/s)
= Pump Total Pressure (m of water)
= Pump Total Efficiency (%)
PRIMARY
CHILLED
PUMP
HEAD
Figure
8.8 | VARIABLE,
BEI Relationship
atWATER
Different
Pump
Head@
BEI (kwh/m2.year)
156.0
155.5
155.0
y = 0.0797x + 151.96
R2 = 0.9999
154.5
154.0
153.5
153.0
0
10
20
30
40
50
Figure
8.9 | VARIABLE,
BEI Relationship
at WATER
Different
Pump
Efficiency
PRIMARY
CHILLED
PUMP
HEAD
@ 35 M
BEI (kwh/m2.year)
156.5
156.0
155.5
155.0
154.5
154.0
40%
45%
50%
55%
60%
65%
70%
75%
80%
85%
158.0
BEI (kwh/m2.year)
157.0
156.0
y = 0.0059x + 151.93
R2 = 0.99979
155.0
154.0
153.0
152.0
100
200
300
400
500
600
700
800
Figure 8.11 | A Summary of BEI Relationship of Different Chilled Water Distribution OptionS
160
Base
158
-3.3
-5.0
156
-5.6
154
-6.2
-7.4
152
150
148
Primary
Constant
Primary
Variable
Primary
Secondary
(pump power
add 10%)
Pump
Variable
High T,
reduced
pipe size
Pump
Variable
High T,
maintained
pipe size
Specific
Pump Power
(545 to 340)
CHILLER EFFICIENCY
Chiller efficiency is represented by the Coefficient of Performance (COP). The COP is defined as:
EQUATION 8.6
COP =
Since the nominator and denominator is both kW, the term COP is a unit-less number. In Malaysia, it is
also common to use the term kW per ton (where ton is refrigeration tonnage, equivalent to average
heat transfer rate of 1 short ton of ice that melts at 0C in 24 hours) to represent the chiller efficiency.
The relationship between COP and kW per ton is shown below:
EQUATION 8.7
kW per ton =
EQUATION 8.8
12
COP x 3.412
OR
COP =
kW/ton
2.50
1.41
3.00
1.17
3.50
1.00
4.00
0.88
4.50
0.78
5.00
0.70
5.50
0.64
6.00
0.59
6.50
0.54
7.00
0.50
12
kW per ton x 3.412
Typically, the chiller efficiency is requested from the chiller manufacturer. More efficient chillers are usually more
expensive. The MS 1525 (2007) provides a range of minimum efficiency requirements for various types of chillers and
capacities. A highlight of the MS 1525 is provided below together with known very good COP that is available today:
Table 8.9 | Recommended Minimum Chiller Efficiencies in MS 1525
Equipment
Sub-category
Minimum COP
(MS 1525, 2007)
Split system
2.7
2.9
Single package
2.7
2.9
19 kWr and
< 35 kWr
2.6
2.9
35 kWr
2.5
2.9
< 19 kWr
3.0
3.3
19 kWr and
< 35 kWr
3.5
3.8
35 kWr
3.6
3.9
Size
Minimum COP
(MS 1525)
Known Good
COP*
2.6
3.0
2.7
3.1
2.8
3.2
2.9
3.4
All capacities
4.0
5.0
4.0
5.0
4.4
5.4
5.4
6.1
5.2
6.3
5.7
7.0
Size
< 19 kWr
Air conditioners:
Air cooled with condenser
Air conditioners:
Water and evaporatively cooled
Equipment
*Designers are recommended to request for the latest COP ratings from chiller manufacturers.
Due to the recent interest in energy efficiency worldwide, chiller manufacturers are improving their chiller efficiencies
rapidly. It is recommended that ACMV designers keep up to date with the latest chiller efficiencies available from the
respective manufacturers instead of relying on the table provided.
SIMULATION STUDIES
A set of simulation studies were conducted to test the impact of the use of different types of chillers and efficiency
ratings. The simulation case model required the use of 3 chillers to meet the building cooling load, to keep each chiller
below the 1,000 ton refrigerant capacity. The case studies made are shown below:
Table 8.10 | Chiller Simulation Case Studies
Case
Type of Chiller
3 Chillers,
Operating Sequence*
Screw
4.0
Stacked
Screw
4.5
Stacked
Screw
5.0
Stacked
Screw
5.5
Stacked
Centrifugal
5.0
Stacked
Centrifugal
5.5
Stacked
Centrifugal
6.0
Stacked
Centrifugal
6.5
Stacked
VSD
5.0
Stacked
10
VSD
5.5
Stacked
11
VSD
6.0
Stacked
12
VSD
6.5
Stacked
13
Screw
5.5
Parallel
14
Centrifugal
5.5
Parallel
15
VSD
5.0
Parallel
16
VSD
5.5
Parallel
17
VSD
6.0
Parallel
18
VSD
6.5
Parallel
The default performance curves for screw, centrifugal and VSD chillers from DOE-21 were used for these simulations.
The chiller performance curves by DOE-2 account for the following variations:
1. Cooling capacity curve based on entering condenser water temperature, chilled water leaving temperature
and datum temperature. This curve adjusts the available capacity of the chiller as a function of evaporator and
condenser temperature (or lift).
2. Water temperature dependence curve based on chilled water supply temperature, entering condenser water
temperature and datum temperature. This curve adjusts the efficiency of the chiller as a function of evaporator
and condenser temperature (or lift).
3. Part-load dependence curve based on part load fraction, chilled water supply and entering condenser water
temperature. This curve adjusts the efficiency of chiller as a function of part-load operation.
In addition, DOE-2 has recently included a new model for variable-speed-chillers that includes temperature terms in the
curve fit equations. The variable speed chiller model was based on an ASHRAE Symposium paper, Development and
Testing of a Reformulated Regression Based Electric Chiller Model. 2
1
DOE-2 is a computer program for the design of energy-efficient buildings. Developed for the U.S. Department of Energy by Lawrence Berkeley National Laboratorys Simulation Research Group, DOE-2
calculates the hourly energy use and energy cost of a commercial or residential building given information about the buildings climate, construction, operation, utility rate schedule, and HVAC equipment.
2
Hydeman, M.; N. Webb; P. Sreedharan; S. Blanc. Development and Testing of a Reformulated Regression Based Electric Chiller Model. ASHRAE, Atlanta GA. HI-02-18-02.2002.
RESULTS
Figure 8.12 displays the BEI of various types of chiller. These chillers were all assigned with the same COP of
5.5. Based on the chiller performance curve provided by DOE-2, the centrifugal chillers were shown to have a
higher BEI than the screw chillers. The VSD chillers are shown to have the lowest BEI among the tested chillers.
Moreover if VSD chillers were run in parallel to ensure that it is kept on part load most of the time, the BEI is the
lowest even though all the chillers have the same COP of 5.5. However, it should also be pointed out that chiller
lifespan is highly dependent on its operating hours. Running VSD chillers in parallel mode to force it to operate
at a more efficient part load condition will increase chiller operating hours significantly, thereby, reducing its
lifespan. Additionally, VSD chillers are known to be more expensive than non-VSD chillers, therefore, it is a
more likely scenario that VSD chillers are coupled with non-VSD chillers to be used in practice. An additional
simulation case study was added in this chapter where one VSD chiller is used in combination with two non-VSD
chillers. The results indicate that this chiller configuration is as efficient as running all VSD chillers in a stacked
mode. Since non-VSD chillers are less expensive, the capital cost is lower than purchasing all VSD chillers.
Figure 8.12 | BEI Performance of Different Types of Chiller at COP of 5.5
+1.2
158
BEI (kWh/m2.year)
+3.5
+3.1
160
Base
156
-1.4
-1.3
154
152
-6.0
150
148
146
144
Screw,
Stacked
Screw,
Parelled
Centrifugal,
Stacked
Centrifugal,
Parallel
VSD,
Stacked
VSD,
Stacked
1 VSD,
2 Centrifugal,
Parallel
Figure 8.13 below provides the curve fit equation for quick estimates of BEI reduction due to the type of chiller used
and COP selection.
CHILLERS
Figure
8.13 BEI
| BEI Performance of Different Types of Chiller at Various COP
BEI (kWh/m2.year)
180
170
160
150
y = 1.3132x2 - 22.64x + 234.21
R2 = 0.99998
140
130
4.0
4.5
5.0
5.5
6.0
6.5
7.0
Chiller COP
VSD Chiller Parallel
In general, a quick rule-of-thumb to estimate the BEI reduction due to the selection of chiller efficiency, COP is
provided in Figure 8.14 below. The BEI is reduced approximately by 10.5 kWh/m2.year for a COP increase of 1.0.
Figure
8.14EFFICIENCY
| Curve Fit of
BEI and COP
of Chillers
CHILLER
IMPACT
ON BEI
200
180
BEI (kwh/m2.year)
160
140
y = -10.535x + 213.22
R2 = 0.83884
120
100
80
60
40
20
0
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
Figures 8.15 to 8.20, display the simulated operating chiller COP due to the building load. The COP value is
not a fixed value at the peak building load because it is also related to the weather at the point of time of the
building peak load. The outdoor wet bulb temperature changes the return condenser water temperature from the
cooling tower, which will influence the operating COP of the chiller (where a lower condenser water temperature
increases chiller efficiency).
A screw chiller with rated COP of 5.5 operates mostly between a COP of 5.5 and 6.0 when it is operated in
stacked sequencing mode. However, when the same screw chiller is operated in parallel sequencing, its COP is
mostly operating between 5.0 to 5.5 for a building load up to 80% and only become more efficient with a COP
of 5.5 to 6.0 when the building load exceeds 80%. This shows that a screw chiller is most efficient when it is run
close to the full load.
Figure 8.15 | Operating COP of Screw Chiller when Chillers are operated in Stacking Sequence
6.5
1 Chiller Running
2 Chillers Running
3 Chillers Running
COP
6.0
5.5
5.0
4.5
4.0
0%
10%
20%
30%
40%
50%
Building Load (%)
60%
70%
80%
90%
100%
Figure 8.16 | Operating COP of Screw Chiller when Chillers are operated in Parallel Sequence
6.5
3 Chillers Running
COP
6.0
5.5
5.0
4.5
4.0
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
A centrifugal chiller with a rated COP of 5.5 operates mostly between a COP of 5.0 and 6.0 when it is operated
in stacked sequencing mode. However, when the same centrifugal chiller is operated in parallel sequencing, its
COP dropped to as low as 4.5 when the building load is at 40%, and increases incrementally up to a COP of 6.0
at building load of 100%. This shows that a centrifugal chiller is also most efficient when it is running close to
the full load.
Figure 8.17 | Operating COP of Centrifugal Chiller when Chillers are operated in Stacking Sequence
6.5
1 Chiller Running
2 Chillers Running
3 Chillers Running
COP
6.0
5.5
5.0
4.5
4.0
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Figure 8.18 | Operating COP of Centrifugal Chiller when Chillers are operated in Parallel Sequence
6.5
3 Chillers Running
COP
6.0
5.5
5.0
4.5
4.0
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Figures 8.19 and 8.20 display the results of VSD chillers with a rated COP of 5.5, operating in stacked sequencing
mode and parallel mode respectively. The default VSD chiller performance curve from DOE-2 was used in this
study. When these VSD chillers were operating in a parallel mode, each VSD chiller is forced to operate at part
load condition for an extended length of time. It was interesting to note from the simulation results that VSD
chillers operating in parallel sequencing mode, have a significant number of hours where the COP of the VSD
chiller was higher than 7.0 (during part load conditions). However, when the same VSD chillers are operated in
stacked sequencing mode, there are hardly any hours where its COP exceeds 7.0.
Operating VSD chillers in parallel mode is shown in this case study to provide much better efficiency than
running them in stacked mode. A proper lifecycle analysis should be conducted to assess the benefit of running
VSD chillers in parallel mode to force it to operate at part load for better energy efficiency, taking into account
of the potential reduction of chiller lifespan.
It is likely the most financially feasible solution is to use one VSD chiller in combination with the rest being nonVSD chillers (results shown in Figure 8.21). In this design configuration, the non-VSD chillers are operated at
peak load conditions while the VSD chiller is used to fill in the part load conditions. Non-VSD chillers should be
coupled with constant flow pumps, while the VSD chillers should be coupled with variable flow pumps to cater
for part-load conditions. Since the supply and return chilled water temperature is the same for all the chillers
(installed in parallel), the constant flow pump will ensure that non-VSD chillers are operating at peak load all
the time, while the VSD chiller is used at part load condition with the variable speed pump for optimum system
efficiency.
Figure 8.19 | Operating COP of Centrifugal Chiller when Chillers are operated in Stacking Sequence
7.5
1 Chiller Running
2 Chillers Running
3 Chillers Running
7.0
COP
6.5
6.0
5.5
5.0
4.5
4.0
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Figure 8.20 | Operating COP of Centrifugal Chiller when Chillers are operated in parallel Sequence
7.5
3 Chillers Running
7.0
COP
6.5
6.0
5.5
5.0
4.5
4.0
0%
10%
20%
30%
40%
50%
Building Load (%)
60%
70%
80%
90%
100%
Figure 8.21 | Operating COP of 1 VSD Chiller and 2 Centrifugal Chillers when Chillers are operated in
Stacking Sequence with the VSD Chiller operating at Part-Load whenever possible and Centrifugal
Chillers are only operated at Full-Load
6.5
1 Chiller Running
2 Chillers Running
3 Chillers Running
COP
6.0
5.5
5.0
4.5
4.0
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
SIMULATION STUDIES
The following set of simulation studies were conducted to study the impact of 3 sets of condenser flow rates
against a range of specific pump power. The rationale behind this set of simulation cases was to test the
crossover point where increasing the condenser flow rate would increase the energy consumption of the
system due to a high specific pump power requirement.
Table 8.11 | Condenser Pump Efficiency Test Cases
Case
T (C)
T (F)
Flow Rate
(gpm/HRT)
Specific Pump
Power (W per l/s)
4.45C
(33.89/29.44)
8 F
(93/85)
3.0
679.15
4.45C
(33.89/29.44)
8 F
(93/85)
3.0
528.23
4.45C
(33.89/29.44)
8 F
(93/85)
3.0
377.31
4.45C
(33.89/29.44)
8 F
(93/85)
3.0
226.38
5.56C
(35.00/29.44)
10 F
(95/85)
2.4
679.15
5.56C
(35.00/29.44)
10 F
(95/85)
2.4
528.23
5.56C
(35.00/29.44)
10 F
(95/85)
2.4
377.31
5.56C
(35.00/29.44)
10 F
(95/85)
2.4
226.38
6.67C
(36.11/29.44)
12 F
(97/85)
2.0
679.15
10
6.67C
(36.11/29.44)
12 F
(97/85)
2.0
528.23
11
6.67C
(36.11/29.44)
12 F
(97/85)
2.0
377.31
12
6.67C
(36.11/29.44)
12 F
(97/85)
2.0
226.38
RESULTS
The simulation results in Figure 8.22 below indicates that in the Malaysian climatic zone, it is beneficial to
design a reduced condenser flow rate from the current standard T option of 35.00/29.44C (95/85F)
to a high T option of 36.11/29.44C (97/85F) (from 2.4 gpm/ton to 2 gpm/ton of condenser flow
rate). The energy reduction from the condenser pump power exceeds the chiller energy increment for all
conditions tested on the base case building with centrifugal chillers.
Figure 8.22 | BEI relationship to Condenser Flow Rate and Condenser Specific
Pump
Power FLOW RATE IMPACT ON EFFICIENCY
CONDENSER
168
164
BEI (kWh/m2.year)
y = 0.0168x + 145.02
R2 = 0.99995
160
y = 0.0279x + 144.54
R2 = 1
156
152
y = 0.0233x + 144.63
R2 = 1
148
144
0
100
200
300
400
500
600
700
800
3.0 gpm/ton
2.4 gpm/ton
2.0 gpm/ton
SIMULATION STUDIES
A set of simulation studies were developed to study the impact of cooling tower optimisation based on all the
issues raised on the previous page.
Table 8.12 | COOLING TOWER Efficiency Test Cases
Case
Descriptions
kWe/HRT
Design Cooling
Tower Leaving Water
Temperature (C/F)
C1
0.045
29.4/85
21.1/70
C2
0.035
29.4/85
21.1/70
C3
0.025
29.4/85
21.1/70
C4
0.015
29.4/85
21.1/70
C5
0.035
29.4/85
21.1/70
C6
0.035
29.4/85
21.1/70
C7
0.035
28.9/84
21.1/70
C8
0.035
28.3/83
21.1/70
C9
0.035
27.8/82
21.1/70
C10
0.035
30.0/86
21.1/70
C11
0.035
30.6/87
21.1/70
C12
0.035
31.1/88
21.1/70
C13
0.035
29.4/85
23.9/75
C14
0.035
29.4/85
26.7/80
C15
0.035
29.4/85
27.2/81
C16
0.035
29.4/85
27.8/82
C17
0.035
29.4/85
28.3/83
C18
0.035
29.4/85
28.9/84
C19
0.035
29.4/85
29.4/85
C20
0.035
29.4/85
30.0/86
C21
0.035
29.4/85
30.6/87
C22
0.035
29.4/85
31.1/88
C23
0.035
29.4/85
32.2/90
RESULTS
Figure 8.23 shows that for an improvement of cooling tower fan efficiency by 0.01 kWe/HRT, the BEI will reduce
by approximately 1.5 kWh/m2.year on a constant fan speed cooling tower.
Figure 8.23 | BEI relationship to Cooling Tower Efficiency at Constant Fan Speed
y = 146.92x + 149.34
R2 = 1
BEI (kWh/m2.year)
156
155
154
153
152
151
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
0.050
Figure 8.24 shows that there is almost no efficiency gain with the use of a 2-speed fan or variable speed fan
when the cooling tower leaving water temperature set point was fixed at a low value of 21.11C (70F). This is
because our climate does not have such a low wet-bulb temperature in the first place for this temperature setpoint to be achieved; therefore, the cooling tower fan will be running at full speed for all conditions.
Figure 8.24 | BEI relationship to Cooling Tower Fan Options with Leaving Water
Temperature Set Point of 21.11C
BEI (kWh/m2.year)
160
154.48
154.46
154.39
140
120
100
Constant Speed
80
2 Speed Fan
60
40
20
O!
Constant Speed
2 Speed Fan
Fan Options
Figure 8.25 is the simulated result of the testing an upsized or downsized cooling tower. The upsizing of a cooling
tower is conducted via the design of a lower leaving water temperature from the cooling tower. The current
standard of practice in the industry is to size the cooling tower for a water leaving temperature of 29.44C
(85F). Sizing it for a lower leaving water temperature will a require larger cooling tower, while a sizing for a
higher leaving water temperature will indicate a smaller cooling tower is used. The simulated results in Figure
8.25 indicate that reducing the cooling tower size reduces building energy consumption due to the smaller fan
power used. The results show that the loss of chiller efficiency is minimal due to the use of a smaller cooling
tower and fan. Finally, it is very important to note that the impact on energy efficiency due to the upsizing or
downsizing of the cooling tower is very minimal. Therefore, designers should not be too concerned over upsizing
or downsizing cooling tower to achieve better efficiency in a building.
Figure 8.25 | BEI relationship to Design Cooling Tower Water Leaving Temperature
BEI (kWh/m2.year)
154.7
154.6
154.5
154.4
154.3
y = -0.1002x + 163.01
R2 = 0.99539
154.2
154.1
154.0
81
82
83
84
85
86
87
88
89
*Take note of the scale of BEI presented on the Y-axis, which is very small.
Figures 8.26 to 8.28 indicates the energy efficiency of using variable speed drive (VSD) fan on a cooling tower
with different set points of water leaving temperature. The VSD will reduce the fan speed when the leaving
water temperature meets the set point temperature to reduce the cooling tower fan energy consumption. The
results of the simulation show that it is most efficient to run a VSD on a cooling tower with a water leaving
temperature set point of 28.33 30.00C (83 - 86F). Somehow the results show that having the water leaving
temperature set point at 27.78C (82F) and 30.56C (87F) increases chiller energy consumption significantly
via a reduction of chiller efficiency. Further investigation showed that this result is largely due to the centrifugal
chiller performance curve-fit used in this study, where the efficiency of the chiller is particularly low then the
water leaving temperature set point is fixed at 27.78C (82F) and 30.56C (87F) .
Figure 8.27 shows that as the leaving water temperature from a cooling tower increases, the cooling tower
fan energy reduces with the use of a VSD. Figure 8.28 shows that as the leaving water temperature from a
cooling tower increases, the chiller energy increases with a particular spike at the water temperature set point
of 27.78C (82F) and 30.56C (87F). The most ideal water leaving temperature set point for a cooling tower
with a VSD is found between 29.44C (85F) and 30C (86F).
Figure 8.26 | BEI relationship to Set Point Temperature of a Variable Fan Speed
Cooling Tower
VARIABLE SPEED FAN, TEMPERATURE SETPOINT
kWe/HRT = 0.035, DESIGN 29.4C/85F
158
BEI (kwh/m2.year)
157
156
155
154
153
152
80
81
82
83
84
85
86
87
88
89
90
91
Figure 8.27 | Heat Rejection Energy Index* relationship to Set Point Temperature
of
a Variable
Fan Speed
HEAT
REJECTION ENERGY
INDEXCooling Tower
16.0
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
78
80
82
84
86
88
90
92
*Heat Rejection Energy = Condenser Pump Energy + Cooling Tower Fan Energy, since condenser pump is kept constant in this study,
the change of heat rejection energy index is only attributed to the cooling tower leaving water temperature set point.
Variable Fan
Speed Cooling
CHILLER
ENERGY
INDEXTower
56
Energy Index (kWh/m2.year)
55
54
53
52
51
50
49
48
47
78
80
82
84
86
88
90
92
BEI (kWh/m2.year)
-0.3
154
-1.5
-1.6
153
152
Base
CT Fan Efficiency
(0.035 to 0.025
kWe/HRT)
DownSize CT Fan
(sized for 88F)
INSTALLATION RECOMMENDATIONS
FOR PUMPS AND PIPES
The following list of recommendations are provided to ensure that air-conditioning pumps
and piping systems are installed efficiently:
Source
10 D
lr elbow
Eccentric Reducer
Source
3
ASHRAE Fundamentals (2008) mentioned that suction
diffusers may be installed in lieu of the straight pipe
requirement where spacing is a constraint. However,
suction diffusers increases the pump head and will
increase the long term energy consumption.
Proper Selection
CORRECT
Pump Suction
Pump Suction
Pump Suction
3D
HEADER FLOW
HEADER FLOW
Pump Suction
WRONG
CORRECT
SUMMARY
This chapter is a set of simulation case studies to offer a simple form of
guidance for building designers to optimise the water-side air-conditioning
system. The simulation studies were based on a typical office building scenario
in the Malaysian climatic zone. Many simulations were conducted to test
various theories of energy efficiency on a water-side air-conditioning system
to understand the impact on the buildings net efficiency within a Malaysian
climatic zone.
Users of this guideline are recommended to be careful with the data provided
in this guideline when it is extrapolated to other building types. As a general
rule-of-thumb, any energy efficiency feature that is financially feasible for an
office building, is likely to provide a faster payback if applied on buildings with
longer air-conditioning hours, as the benefit gained is over a longer operating
period.
Finally, as recommended in previous chapters, building design engineers are
encouraged to pick up building energy modelling skills to enhance their design
capabilities for the building industry. Building energy simulation tools are much
easier to use today than they were 10 years ago. Software such as IES <Virtual
Environment>, DesignBuilder, TAS, Trnsys, Visual-DOE, Equest and HAP are
fairly well known dynamic energy simulation softwares in the market place
today and can be used to optimise the actual building design instead of relying
solely on this guidebook.
END OF CHAPTER 8
CHAPTER
COMMISSIONING,
FINE-TUNING &
CONTINUOUS
MONITORING
9 COMMISSIONING,
FINE-TUNING &
CONTINUOUS
MONITORING
INTRODUCTION
The experience in the Low Energy Office (LEO) Demonstration Project in Parcel E4/5 in
Putrajaya, Malaysia, showed that proper commissioning and fine-tuning of a building reduced
the buildings energy index (BEI) of the LEO building from a high of 170 kWh/m2.year down to
120 kWh/m2.year (a reduction of 30%) within the first 3 months of occupancy in 2003.
One of the key lessons learned from the LEO demonstration building is that building designed
to be energy efficient will not operate efficiently until proper commissioning and fine-tuning is
conducted on it. It is therefore very important that buildings are commissioned and fine-tuned
to operate optimally based on the actual building operational needs to ensure that efficiency is
obtained in reality.
This fact is supported by many other case studies around the world with some estimates that it
is possible for a properly commissioned and fine-tuned building to reduce energy consumption
by (as high as) 40%.1 Another report states that the commissioning of projects in over 10,000
buildings in the US resulted in a median whole-building energy reduction of 16% with a payback
time of 1.1 years in existing buildings. 2 A typical office building with an area of 50,000m2 would
have an approximate energy cost of RM3.6 million per year (based on current electricity tariff) in
Malaysia. A reduction of 16% energy consumption will yield a significant saving of approximately
RM600,000 per year for the building owner.
It is not a simple task to translate the buildings projected energy performance during the design
stage into real, actual energy performance during operation. Furthermore, Malaysian energy
costs, along with the rest of the world, is likely to maintain an upward trend in the short and
long term scenario, hence the need to ensure that buildings are operating energy efficiently has
become more important than ever before. The basic elements that are needed to bridge the gap
between design and operational efficiency in building are:
Appointment of Building Energy Manager
Commissioning
Fine-tuning, and
Continuous Monitoring
1
National Renewable Energy Laboratory, 2013 http://www.nrel.gov/tech_deployment/climate_neutral/energy_efficient_building_management.html
2
Evan Mills, Lawrence Berkeley National Laboratory, Building Commissioning - A Golden Opportunity for Reducing Energy Costs and Greenhouse Gas Emissions,
California, USA, p 1, 2009.
KEY RECOMMENDATIONS
1 APPOINT A BUILDING ENERGY MANAGER
A building energy manager should be appointed to ensure successful implementation
of energy efficiency in a building. It is also important to ensure that the building energy
manager receives adequate training to ensure that this person will be able to perform his/
her duties adequately.
The building energy manager may be the same person as the building facility manager or
any other person that is close to the buildings top management. This person is then put in
charge to ensure that the building is energy efficient during operation.
2 COMMISSIONING
Commissioning is more than just a functional test of equipment. Commissioning should
measure all performance parameters to ensure that all major equipment is operating as per
the design intent. For example, variable speed drive fans and pumps should be tested to be
operating as per the design intention at full-load and part-load conditions.
Commissioning should also provide adequate data to enable the efficiency of major
equipment to be measured on-site. Any equipment that is measured to be performing at
efficiencies significantly lower than the supplier data may indicate an installation fault that
needs to be corrected before the handing over of the building by the contractor.
It is also recommended to start commissioning early in the design process to ensure that
essential installation guides, testing and commissioning requirements are captured early in
the contractual documentation for the appointed contractor to avoid any disputes at the end
of the project stage.
3 FINE-TUNING
All new buildings are required to be fine-tuned during the actual operation of the building
to optimise the buildings performance based on actual occupant behaviour. This may refer
to reprogramming operational hours of common area lighting, reprogramming the airconditioning pre-cooling hours, etc. It may even involve complicated manoeuvres such as
optimising the air-conditioning supply air flow rate based on the actual measured sensible
load to reduce the buildings energy consumption if the building is not fully occupied as per
the design assumptions.
4 CONTINUOUS MONITORING
Finally, it is important to establish a system of continuous monitoring of the buildings
energy performance via a set of sub-meters in the building. A weekly summary of energy
consumption of major sub-meters in the past 6 months should be provided to the buildings
top management to ensure that any drastic changes are captured, analysed and acted upon
when necessary to maintain the buildings energy efficiency performance.
These keys recommendations made are also applicable for existing buildings.
It is fairly common in existing buildings that failure of non-critical equipment such as the
temperature sensors, motorised damper/valves, etc. are not repaired to its original design
intent state. The priority of most building facility technicians is to fix the system to get some
sort of air-conditioning to the building occupants. Energy efficiency is the last thing on their
mind when the system is not working. Unfortunately, the failure of these non-critical equipment
will lead to significantly higher energy consumption in a building due to inadequate feedback
and control to optimise buildings energy during use. The implementation of these four (4) basic
recommendations in an existing building will allow these issues to be identified and fixed for the
long term benefit of the building.
Finally, the Malaysian Standard (MS) 1525 provides detailed guidance on Energy Management
Systems (EMS) and is highly recommended to be practiced by the building industry for buildings
where the air-conditioned area exceeds 4,000m2.
APPOINTMENT OF BUILDING
ENERGY MANAGER
It is highly recommended to appoint one person that answers directly to the building owner to
be the building energy manager that is responsible for the efficient energy performance of the
building. Although it is easiest to appoint the building facility manager as the building energy
manager as well, this may not necessarily be the best option. If the building energy manager is
appointed early during the design stage of the building, he/she will be able to learn from the
whole design process and the decisions made on energy efficiency for the building along the
way. In addition, the building energy manager can also help to contribute to the design process
by ensuring the energy efficiency needs are addressed during the entire design, construction
and commissioning process.
The appointed building energy manager will also need to have the authority and support of the
management to take necessary action, such as setting aside a yearly budget for maintaining
(and improving) energy efficiency in the building. This budget can be used on promotional
programmes to instill energy efficiency awareness for the building occupants, to repair
equipment that has failed or any other work that will bring added benefit to reduce the energy
consumption in the building without compromising on the occupants comfort.
It is also very important for the building energy manager to be properly trained for this role.
There are many regular training programmes available in Malaysia. A few of these regular
training programmes are listed below:
AEMAS Energy Management Training Course by GreenTech Malaysia
(www.greentechmalaysia.my)
Energy Manager Training Course by Malaysia Association of Energy Service Companies (MAESCO)
(www.measco.org.my)
Electrical Energy Manager Qualification Course by Malaysia Productivity Corporation (MPC)
(www.mpc.gov.my)
Certificate in Energy Management by Federation of Manufacturer, Malaysia (FMM)
(www.fmm.org.my)
COMMISSIONING
The commissioning process is a quality-oriented process for verifying and documenting the performance
of facilities, systems and assemblies installed in the building. A commissioner uses various methods and
tools to carry out the verifications throughout the delivery of the project. Commissioning activities happen
in each phase of the project, beginning from the pre-design to completion stage. To provide the optimal
performance of the building, the commissioner needs to coordinate work with the different team members
in each phase with the aim of ensuring every energy efficiency feature is implemented properly.
It is also recommended to nominate a person in the design team to be the leader in energy efficiency at the
start of a building project, whose specific task is to look into all aspects of energy efficiency for the building.
The energy efficiency leader should be someone that has a reasonable knowledge of energy efficiency in
buildings and should have the ability to evaluate different options of energy efficiency design features by
providing estimated payback and return on investment studies. The following is a list of potential candidates
that could qualify as an energy efficiency leader for a project:
2 DESIGN PHASE
In the design phase, the Commissioning Team should perform a commissioning design review. This ensures that the
documented OPR are being implemented. Additional design reviews are made in areas of special concern to the owner.
The main energy efficiency leader duties during this phase are the following:
3 Commissioning Specifications
There should be specific commissioning process requirements to be included in the contractors documents. It
specifies equipment details and component performance requirement checklists with appropriate cross-references.
Such specifications should include any special equipment or instrumentation that must be available in order to obtain
measurements during functional testing. Additional monitoring points, test ports and gauges can make the building
more commissioning-friendly.
The specifications should ensure that all major equipment should be tested at its peak design condition as well as at
partial load conditions to ensure that all the controls are functioning as per the design intent.
A proposed list of measurement points during commissioning is provided below to establish the performance of a typical
chilled water plant air-conditioning system. It may also be advantageous to provide continuous monitoring of some of
these proposed points in a building management system (BMS) or energy management system (EMS). Continuous
monitoring of this data will ensure that the building is monitored to be operating at optimum conditions at all times. Any
deviation or loss of efficiency can also be easily detected when adequate monitoring points are provided.
PROPOSED MEASUREMENT POINTS DURING COMMISSIONING
1) AHU System
a. P Total Pressure between the inlet and outlet of the fan (Pa)
This data verifies the computed pressure loss in ducts, air filters, cooling coil and dynamic air pressure.
This data is also required to compute the Fan Total Efficiency.
b. P Static Pressure between the air filter (Pa)
This data verifies the pressure drop across the air filter.
In addition, a permanent monitoring of this data is recommended as an indicator of service requirement on the
air filter. Unless, this is monitored, it is not possible to know the optimum time to service or change the air filter.
c. Supply Air Flow Rate
The measured supply air flow rate provides many opportunities for ACMV optimisation. These opportunities
are:
1. Computation of Sensible, Latent and Total Heat Load
2. Computation of Fan Total Efficiency
3. Potential to reduce peak air flow rate during fine-tuning period to reduce building energy consumption
especially if building is not fully occupied
d. On-coil Air Temperature
This data is required to compute the sensible cooling load.
This data is also required as a verification of the installation meeting the design intention.
c. Chilled Water Supply Temperature from Chiller (C)
This data is required to compute the total cooling load supplied.
d. Chilled Water Return Temperature to Chiller (C)
This data is required to compute the total cooling load supplied.
e. Pump Power (kW)
This data is required to compute the Total Pump Efficiency.
f. Total Cooling Load Provided (kW)
This data is required to compute the Chiller COP.
g. Total Pump Efficiency (%)
If the efficiency is far below the pump performance curve, the building energy manager should investigate the
cause of it. This may be due to improper pump/pipe installation.
3) Chiller
a. Chiller Power
This data is required to compute the Chiller COP.
It is also required to compute the System COP.
b. Chiller Coefficient of Performance
Continuous monitoring the Chiller performance ensures that any performance lost by the Chiller is observed
and action can be taken.
c. System Coefficient of Performance
This is the simplest indicator of system performance. Continuous monitoring of this data is recommended.
d. Total Heat Rejection Power
This data is computed from the total cooling load delivered, Chiller power and Condenser pump power.
This data is then used to estimate the condenser flow rate based on the condenser supply and return
temperature.
4) Condenser Water Distribution System
a. Condenser Water Supply Temperature (C)
This data is required to compute the condenser flow rate.
b. Condenser Water Return Temperature (C)
This data is required to compute the condenser flow rate.
c. Pump Power (kW)
This data is required to compute the Total Pump Efficiency.
d. P Total Pump Head between the Suction and Supply Side of the Pump (m of H2O)
This data is required to compute the Total Pump Efficiency.
e. Condenser Flow Rate (l/s)
This data is required to compute the Total Pump Efficiency.
f. Total Pump Efficiency
Computed Pump Efficiency that is significantly lower than the design/supplier efficiency indicates installation
issues.
5) Cooling Tower
a. Fan Power (kW)
This data is required to compute the cooling tower efficiency.
b. Ambient Air Wet Bulb Temperature (C)
This data is required to compute the approach temperature of the cooling tower.
c. Ambient Air Dry Bulb Temperature (C)
This data is useful to estimate the fresh air sensible load.
d. Water Leaving Temperature (C)
This data is required to compute the approach temperature of the cooling tower to ensure that the cooling
tower is meeting design specifications.
e. Approach Temperature
This data indicates the performance of the cooling tower and should be compared to the design specifications.
f. Cooling Tower Efficiency (kWe/HRT)
This value is provided as an indicator of the cooling tower efficiency.
3 CONSTRUCTION PHASE
It is an effective measure to have the Commissioning Team monitor the construction phase on
all items related to energy efficiency in the building. The main tasks to be accomplished during
this stage are as listed below:
1 Kick-off Meeting
The Commissioning Team should carry out a construction phase commissioning kick-off
meeting with the appointed contractors. The role of the Commissioning Team during the
meeting will be to review and discuss the OPR and the communication protocols that the project
team has developed. In this meeting, an outline of the roles and responsibilities of each of the
team members are specified. Procedures for documenting commissioning activities, resolving
issues and reviews of preliminary construction phase commissioning plans and schedules are
made at this stage.
A list of submittal requirements by the contractor should be provided by the Commissioning
Team early in the construction phase. The submittal requirements should provide the contractor
a list of equipment and installation procedures that require approval before installation is allowed
to be conducted on-site. All critical installation layouts that are crucial to the efficient operation
of the installed equipment should be part of the list of submittal requirements. The proposed
functional tests and commissioning procedures before handing over by the contractor should
also be a part of the submittal requirements.
Finally, the Commissioning Team should maintain a record of issues and findings in a log that
requires further attention. The log should be updated regularly and discussed with the project
manager and team and resolved during construction meetings.
2 Submittal Review
The Commissioning Team should review, comment and approve the contractors submittal to
ensure that contractors are providing equipment and installations that meet the design intent
of the project. This is an essential scope of work by the Commissioning Team to ensure that
the procurement of major equipment and installation methods comply with the necessary
specifications to meet the efficiency targets of the OPR.
1 Periodic Testing
Periodic testing should be conducted as per equipment maintenance schedules to ensure the
system is running efficiently. Any testing that is delayed due to site conditions, equipment status
or rainy weather needs to be completed as early as possible and certainly before the end of the
defect liability period.
2 On-going Training
The Commissioning Team will verify the completion of the commissioning process by ensuring
that all related training is provided by the contractor to the building facility management team
as part of the handing-over process. This includes the updating of the system manual and
documentation in a version that can be understood and implemented by the building facility
management team. It is also important to ensure the hand-over of a manual on the building
management system (or energy management system) that is relevant to the building. The
operation manual should provide the typical (and design) operating set points of all equipment
for the installed air-conditioning system.
FINE-TUNING
Fine-tuning in a building is the process of matching the building comfort conditions to the actual requirements of the
building occupants, while optimising building energy performance. Every new building needs a period of fine-tuning to
match the operational needs of the building occupants while improving the energy efficiency in the building. Examples
of typical fine-tuning work to be conducted in new buildings are described below:
1 Lighting Schedules
It is common in many office buildings to turn on the airconditioning system an hour before official working hours
to pre-cool the building to comfortable conditions. During
the fine-tuning stage, the pre-conditioning hour can be
slowly reduced until it is optimal for the actual building
operation. Typically, an office building will require longer
pre-conditioning hours on a Monday morning due to
the reason that the building structure (typically of high
thermal mass) is warmer from the unconditioned hours
of Saturday and Sunday.
3 Air-Temperature Set-Point
Fine-tuning a building also involves setting air
temperatures for optimum comfort of the building
occupants. Building occupants sitting close to the building
external wall may require a slightly lower air temperatures
due to the higher mean radiant temperature in that area.
Chief Executive Officers (CEOs) in large companies may
be dressed in formal business suits during normal working
hours and may require lower air temperatures to provide
comfortable conditions.
6 Air-Conditioning Hours
The above are just a few examples of simple fine-tuning potential that can be made to the building during the occupancy
period. There are many more options for the air-conditioning system such as the off-coil temperature set-point in a Variable
Air Volume (VAV) air-handling unit, chilled water temperature reset, VAV system static pressure reset, cooling tower fan
reset and much more, that can be implemented to fine-tune a building to perform energy efficiently during operation.
The appointed (and trained) building energy manager should propose a list of fine-tuning possibilities for the building
and have them implemented to provide a safe and comfortable environment for the building occupants while minimising
energy consumption in the building.
Finally, fine-tuning of a building is best complimented by continuous monitoring through a set of sub-meters together with
good implementation of an Energy Management System (EMS).
CONTINUOUS MONITORING
Continuous Monitoring helps the building owner to manage energy consumption and maintain optimal
equipment performance by ensuring that critical building systems, such as the HVAC, lighting and
building controls function properly all the time. Continuous monitoring is a process of collecting and
analysing the data from a set of sub-meters and various controlling parameters of a building to ensure
that the building continues to operate at optimum performance for the lifetime of the building.
Without continuous monitoring, degradation of energy performance in a building is often not noticed by
the building owner. This is because the degradation of energy performance in buildings occur in small
increments that are not noticeable from the monthly energy bill. For example, most building owners
will not notice a 1% increase in the energy bill per month. However, three years later, the bill may be
36% higher and they will still have no clue why it has increased so much over the years. Sub-metering
in combination with continuous monitoring will be able to address this issue by ensuring that any
degradation of energy performance in a building is detected early and more importantly, to identify the
source of the performance reduction in the building.
Continuous monitoring in buildings require the following items to be implemented during the design and
construction stage of the building:
1. Energy Sub-Meters, and
2. Energy Management System
1 ENERGY SUB-METERS
Adequate energy sub-meters are recommended to be provided in a building to allow a breakdown of
energy consumption in a manner where it is feasible for a building energy manager to identify the areas
of inefficiency or equipment failure. Without sub-metering, it is nearly impossible to track inefficiencies
(especially in a medium to large sized building) from the bulk energy meter provided by the power utility
company for these following reasons:
1. In a 20 storey building, an increase of 1% per month on the bulk energy meter is not noticeable.
However, an increase of 1% on the bulk energy meter is a noticeable 20% increase on one of the
floors.
2. The building energy manager will have no idea where to start to track down inefficiency in the
building. This person has to make wild guesses as to where the energy increase is happening
in the building and may have to spend a significant amount of time, effort and money (to recommission the building) to track it down if sub-metering is not provided in building.
Therefore, it is very important to ensure that energy sub-meters are planned for and provided from the
beginning of the building design stage.
Unfortunately, the rule of implementing energy sub-metering in a building is not clearly defined. As a
general rule, adequate energy sub-meters should be provided to enable any building energy manager
to identify equipment that is operating inefficiently within a day of detecting a significant increase on
the sub-meter, so that action can be taken quickly to correct any glitches found in the building system.
In an ideal set-up, energy sub-meters should be provided on every floor of a building to provide a
breakdown of energy consumption for lighting, equipment (small power/plug load) and air-conditioning
on each floor. However, it is also possible to provide it based on location or on a departmental basis as
long as it allows the building energy manager to narrow down the search for inefficient equipment in the
building. In addition, sub-meters should also be provided to separately monitor the energy consumption
of major equipment such as chillers, pumps and cooling towers.
It is further recommended in this guideline that the historical records kept by the EMS should be
provided with simple to use analysis tools to provide line charts and bar charts for quick analysis
of the historical records.
1) LINE CHARTS
The line charts must have the ability to add an unlimited number of meters to the chart
for comparison purposes.
Daily, kW and W/m2 (y-axis) vs. time (x-axis)
Last 7 days, kW and W/m2 (y-axis) vs. time (x-axis)
Last 1 month line chart, kW and W/m2 (y-axis) vs. time (x-axis)
At the end of each month, a PDF version of the 1 month line chart shall be created for
each meter and equipment monitored and filed with date of creation on it.
2) BAR CHARTS (kWh ONLY)
The bar charts must have the ability to add an unlimited number of meters to the chart for
comparison purposes.
Weekly Bar charts. Each bar provides (kWh/m2/day) for last 7 days. i.e. 7 bars
Monthly Bar charts. Each bar provides (kWh/m2/day) for 1 month. i.e. 30/31 bars
Yearly Bar charts. Each bar provides (kWh/m2/week) for 1 year. i.e. 52 bars for 1 year
Unlimited yearly bar charts. Each bar provides (kWh/m2/year) for the number of
years the building has been running.
3) GROUPING CHARTS
The following groups (as applicable) are recommended to be provided:
Total Common Area Lighting Power
Total Tenant(s) Small Power
Total Faade/Outdoor Lighting Power
Total Air Handling Unit Power
Total Chiller Power
Total Chilled Water Pump Power
Total Condenser Water Pump Power
Total Cooling Tower Fan Power
Total Car Park Lighting Power
Total Plumbing Power
Total Miscellaneous Power
Total Building Power (Sum of all the power consumption above)
All Grouping Charts shall provide the following displays:
Daily, kW and W/m2 (y-axis) vs. time (x-axis)
Last 7 days, kW and W/m2 (y-axis) vs. time (x-axis)
Last 1 month line chart, kW and W/m2 (y-axis) vs. time (x-axis)
Daily Bar charts per week. Each bar provides (kWh/m2/day) for 7 days
i.e. 7 bars (To be printed out weekly as a report)
Daily Bar charts per month. Each bar provides (kWh/m2/day) for 1 month
i.e. 30/31 bars (To be printed out monthly as a report)
Weekly Bar charts per year. Each bar provides (kWh/m2/week) for 1 year
i.e. 52 bars for 1 year (To be printed out yearly as a report)
Yearly bar charts. Each bar provides (kWh/m2/year) for the number of years the
building has been running (To be printed out yearly as a report)
B For each CO2 meter, the following line charts should be provided with a
minimum logging interval of 10 minutes:
C For each Temperature Meter (air-side and water-side), the following line charts
should be provided with a minimum logging interval of 10 minutes:
D For each Energy Meter (commonly known as BTU meter in Malaysia) for
chilled water, the following line charts should be provided with a minimum
logging interval of 10 minutes for kWcooling provided, Chiller Coefficient of
Performance (COP) and System Coefficient of Performance (SCOP):
E For each Flow Meter provided in the building, the following line charts should
be provided with a minimum logging interval of 10 minutes:
F For each Digital Pressure Sensor provided, the following line charts should be
provided with a minimum logging interval of 10 minutes:
All raw logging data should be kept for a minimum of 28 days (or 1 month) on the server. At
the end the month, a PDF version of the 1 month line chart should be created and filed with
the date of creation on it to ensure that a history of performance is kept for each meter and
equipment. The raw logging data is allowed to be deleted after the PDF file has been created.
This is to streamline the amount of raw data that is collected and stored on the server.
SUMMARY
Even when buildings are designed to be energy efficient, the predicted efficiency
during the design stage will not materialise without the appointment of a building
energy manager, and the implementation of a proper commissioning, fine-tuning
and continuous monitoring work.
The appointment of a building energy manager is essential to the long term energy
efficiency of a building. The additional running cost of an inefficient mid to large
sized building far outweighs the cost of hiring a good and responsible building energy
manager to keep the building efficient at all times by ensuring that equipment is
well maintained for optimum efficiency. Moreover, it is absolutely necessary to
appoint someone to be responsible for the overall efficiency of a building. If no one
is appointed, then no one is responsible for the buildings energy efficiency and no
one will care if the energy bill has increased significantly over the years because it is
assumed that the building owner is still happy paying for it.
It is also essential that building owners, consultants and contractors implement
a set of proper commissioning works before handing over the building to ensure
that the equipment installed in the building is performing to design specifications.
Proper commissioning work is more than just starting the air-conditioning system
to supply cool air into the room. Each part of the system should be tested to
perform to the design intent at full load and part load conditions. In addition, onsite measurement of equipment efficiency is high recommended. Any installation
errors are easily detected from proper commissioning work and can be rectified by
the contractors before they remove themselves from the building site.
Fine-tuning work is required to optimise the buildings energy performance to
the actual building occupant comfort requirements. Its function is to increase
the building occupants comfort level while improving energy efficiency. There
are hundreds of fine-tuning strategies that can be implemented in buildings.
The appointed building energy manager should try to implement as many of the
available fine-tuning strategies as possible to ensure that the building is performing
optimally at all times.
Finally, continuous monitoring of the buildings energy efficiency should be made a
standard operational practice to ensure that the optimum efficiency is maintained
for the life-time of the building. Failure of small and non-critical components in
buildings are often ignored because they only lead to small increments in running
costs of the building. However, when many of these defects (or failure of noncritical components) start to pile up in the building, the energy wastage can be
significant and yet go unnoticed by the building owner because these failures occur
over a length of time and the small incremental cost increases in the energy bill
every month is hardly noticeable. However, by having continuous monitoring of the
buildings energy efficiency via a set of sub-meters, such defects will be quickly
noticed and be rectified to maintain the optimum energy performance of the
building.
END OF CHAPTER 9
GLOSSARY OF TERMS
ACH
ACMV
AHU
BEI
BMS
BSEEP
CAV
CFL
CRI
EMS
FCU
HID
HRT
HVAC
LED
LMS
LOR
LPD
LSG
MERV
OTTV
PIR
PMV
PPD
RPM
SHGC
TRY
UGR
VAV
VLT
VSD
WWR
APPENDIX
Additional information and data for each of the chapters
in this book is available on the BSEEP website:
http://www.jkr.gov.my/bseep/