International Journal of Computer Applications (0975 8887)

Volume 9 No.7, November 2010

Application of RELUX Software in Simulation and Analysis

of Energy Efficient Lighting Scheme
Shailesh K R Tanuja S Raikar
Senior Lecturer Lecturer
Department of E & E Engineering Department of Computer Science Engineering
MIT, Manipal University - 576104, India MIT, Manipal University - 576104, India

ABSTRACT Integrated artificial and daylight harvesting schemes with energy-

Designing a building with maximum utilization of daylight and efficient luminaires and lighting controls can help reduce the
use of energy efficient luminaires will reduce the cost of energy electrical demand and improve vision efficiency of the building
use. In the present study, by means of computer simulations occupants [1, 2]. Proper daylight-linked lighting controls have a
using RELUX software, the interaction between natural and strong potential for reducing building electricity use. As daylight
artificial light and the related illumination conditions expected in produces less heat per unit of illumination than many artificial
a commercial office building in Mumbai, India have been lighting systems, day lighting may reduce cooling requirements
simulated and analysed. In this way, it was possible to evaluate when it replaces artificial lighting [3-5]. Heat gain and heat loss
the relevant loads for artificial illumination that has been through windows, glare control, and variations in daylight
considered not as the principal but a complementary light source. availability must be carefully balanced. Recently, strong
The main goal of this study is to show the potential of drastically recognition has been given to the contribution that daylight can
reducing the electrical energy consumptions for illumination, by make to energy conservation in buildings [68]. A number of
adopting day lighting harvesting solutions. Comparison were design strategies can be applied in new buildings and in the
done using two different lighting schemes one with Fluorescent retrofit of existing buildings. Field measurements on commercial
Luminaires and without daylight harvesting and other one with buildings using daylight-linked light controls revealed that the
LED fixtures with daylight harvesting using combined occupancy annual lighting energy can be saved by 3060% of total electric
and daylight dimming sensors. With the latter scheme a saving of lighting consumption [9,10]. The energy savings derived through
80% can be achieved on energy and operating costs for a period the use of day lighting not only facilitate the sparing use of
over 25 years. electric lighting and reduced peak electrical demand, but also
reduce cooling loads and offer the potential for smaller air-
conditioning plants to be built [11,12].The determinations of
General Terms daylight illuminance and lighting energy savings can be
Computer Aided Design, RELUX Simulation performed computer simulations [13] or simple calculation
methods [14]. Daylight helps reduce the electricity use for
Keywords: electrical lighting. Also, because of the high luminous efcacy,
Day light; Lighting control; Occupancy sensor; Computer less heat will be dissipated for the same lighting requirement
simulation; Relux; and, hence, there will be less demand for cooling. This is
particularly benecial to tropical and subtropical regions. In
tropical Mumbai, air-conditioning and lighting account for over
two-thirds of total electricity use for typical non-residential
1. INTRODUCTION buildings [downloaded paper]. It is not difficult to understand
The construction sector in India is witnessing a fast growth due that day lighting controls can result in signicant energy savings.
to increased demand for housing, strong demographic impetus,
expansion of organized retail, increased demand for commercial This paper highlights the importance of proper integration of
office spaces by multinationals and IT (information technology) artificial and day lighting schemes in saving energy costs in a
hubs, and coming up of SEZs (special economic zones). Most commercial building in Mumbai. Computational analysis using
Indian buildings are also copying western energy-intensive RELUX software has helped to evaluate the performance of the
building concepts such as high air-conditioning and heat integrated artificial-day lighting scheme in the office building
radiating glass. Making Indian buildings energy efficient is thus over a period of one year. The study showed that day lighting
crucial. In the most commercial offices in India, artificial light is measures are only efficient when the performance of artificial
the main contributor to the visual environment, even though lighting systems is also addressed with new efficient lamps and
there is an abundance of daylight and the working hours in luminaries and an advanced control system are installed. The
offices utilise much of the daylight hours. Strategies for more paper aims at providing building professionals, practitioners and
daylight inclusion is needed for office interiors in context of any researchers more information and a better understanding of
city which has a growing demand on electricity, far in excess of daylight-artificial light integrated schemes for promoting
its production. effective day lighting designs.

24
 International Journal of Computer Applications (0975 8887)
Volume 9 No.7, November 2010

2. CASE STUDY building are made of concrete. Building has no obstruction for at
The commercial building chosen for the case study is just five least 100 metres from the Eastern side. Day light can be
minutes walking distance from Ghatkopar (W) railway station in harvested only along the Eastern side.
Mumbai. The seven storey building exclusively is being made for Table 1. Comparison of structural glazing characteristics
business class offering shops on the ground floor and one office Property Existing Proposed
per floor for the rest of the seven floors. The complex also
provides modern facilities such as multiple cars parking in
basement, two high speed elevators. Type SGG ANTELIO PLUS SGG ANTELIO
(Blue Ray ST 767) PLUS (Emerald Glaze
ST 467)
Light Transmittance 0.39 0.47
Solar Factor 0.37 0.31
Shading Co-efficient 0.43 0.35
Relative Heat Gain 306 W/m2 253 W/m2
(Ashrae Value)
U Value 2.8 W/m2K 1.77 W/m2K

The building owners never planned to use daylight harvesting for

illuminating the office interiors. So authors felt that by taking up
this case study and with the help of RELUX software they could
bring out the advantages of daylight harvesting and its impact on
energy costs. Authors also wanted to highlight the impact of
choosing energy efficient light sources and proper glazing for
effective daylight harvesting and reducing operating costs. The
analysis made by the authors could help in convincing the
builders for changing the fixtures and glazing at an early stage
and go with the recommendations made by the authors.

3. ARTIFICIAL ILLUMINATION
This section deals with detailed RELUX software analysis of
artificial lighting schemes considering both existing Fluorescent
and proposed LED luminaires. It is assumed that the offices are
lit by artificial light sources throughout the office hours without
making use of daylight harvesting. The working service
Figure 1. Floor plan of the office used for study illuminance is considered to be 500 lux as per Indian Standards
[17] and number of working hours considered is 2088 hours for
The building chosen for study is still under construction. The
the entire year.
purpose of choosing this still under-construction building is to
allow implementing the modifications pointed out during the
study in the final ready to occupy building. The building is a
3.1 Existing Illumination Scheme
The existing lighting scheme is provided by Parabolic Troffers
RCC framed earthquake resistant structure with aesthetically
housing three GE made 40W Single Ended Twin Fluorescent
designed appealing elevation with quality structural glazing. The
tubes. The scheme is designed for a service illuminance of 500
structural glazing of type SGG ANTELIO PLUS (Blue Ray ST
767) [15] will supply by Saint Gobain India. The suggested lux as per Indian Standard IS-3646I:1992 [17] assuming a
maintenance factor of 0.8 using RELUX software. Computer
existing glazing is reflective solar control exterior glass that will
simulation of the existing lighting levels in the office floors are
be used in the building to block the incoming heat radiation from
obtained using RELUX software and shown in Figure 3a and
the sun, while allowing in natural light. The characteristics of the
illuminance results are summarised in Table 2. The current
existing (as planned by the builder) and proposed (as suggested
by the authors) glazing are compared in the Table 1. scenario is to use artificial illumination throughout the working
hours for interior illumination. If interior illumination is provided
The building has seven office floors. As per the existing design by the existing Fluorescent luminaires throughout the day, the
proposed by the builder, all the office floors will be illuminated annual energy costs would be around Rs 160,000 at a power
by 2x2 nine cell parabolic troffer [16] housing three 40W TT5 tariff of Rs 6 per KWH. Mumbai is a tropical city and lot of
lamps of GE make. The luminous intensity diagram and fixture daylight is available throughout the day and major portion of the
photograph are shown in Figure 2. As per existing plan the year as seen from RELUX simulations in Figure 4. The
building will rely on artificial lighting during the office hours simulations show when artificial light is required and when
from 09:00hrs to 18:00hrs. The building has structural glazing daylight alone can provide necessary interior illuminance. During
along the Eastern side as seen in Figure 1. All other walls of the the annual operations of the building offices around 96%

25
 International Journal of Computer Applications (0975 8887)
Volume 9 No.7, November 2010

(around 2002 hours of 2088 working hours) of the time daylight but in reality this is not the case as seen from Figures 5 and 6.
alone can provide sufficient working illuminance and only 4% of There is a requirement of artificial illumination even during day
the time the offices require artificial illuminance. If we go by this hours. Due to the building orientation and dimensions of the
observation then Fluorescent luminaires have to be operated only offices not all portions of the offices are illuminated to the
for 86 hours there by resulting in an annual operating cost of Rs desired daylight factor of 5% [6]. Hence the best way to provide
6,400 thereby saving Rs 153,600. It is assumed that daylight will service illuminance is to integrate both artificial and daylight
provide the required illuminance throughout the office interiors, schemes with daylight dependent lighting control system.

Figure 2. Luminaires - existing fluorescent luminaire (Luminaire 1) and suggested LED luminaire (Luminaire 2) for the
building

Table 2. Results overview

Details Fluorescent Luminaire LED luminaire
Number of Luminaires required in each office floor 14 27
Wattage Per Luminaire (Watts) 130 52
Average Illuminance (LUX) - EAV E 538 535
Minimum Illuminance (LUX) - EMIN 271 343
Maximum Illuminance (LUX) EMAX 660 621
Uniformity Ratio - EMIN/EAV E 0.50 0.64
Uniformity Ratio - EMIN/EMAX 0.41 0.55
Total Luminous Flux of all luminaires (Klum) for all seven office floors 926 719
Total Power (Kilo Watts) for all seven office floors 12.74 9.82
Annual Energy Costs (approximate) Rs 160,000 Rs 120,000

26
 International Journal of Computer Applications (0975 8887)
Volume 9 No.7, November 2010

Figure 3. Lighting levels for the office floors with existing fluorescent luminaires (a) and proposed LED luminaires (b)

Figure 4. Exterior Illuminance isolux curves

27
 International Journal of Computer Applications (0975 8887)
Volume 9 No.7, November 2010

Figure 5. Illuminance levels in the office interior due to daylight under CIE Overcast sky

Figure 6. Illuminance levels in the office interior due to daylight under CIE Clear sky

28
 International Journal of Computer Applications (0975 8887)
Volume 9 No.7, November 2010

Reducing the wattage of lighting system represents only one 120,000 a saving of 22% for 2088 hours of operation. Further
part of the energy saving opportunity; other part is to minimize with daylight harvesting the annual operating costs will be Rs
the use of those loads using right control system. This involves 4,900 thereby saving Rs 115,100.
the application of occupancy sensing, automatic switching and
The next section discusses in detail the quality and life cycle cost
dimming according to the availability of daylight. It is planned to
comparisons for the two schemes.
implement daylight dependent light control system in the
building for maximum daylight harvesting for interior
illumination. Daylight harvesting systems are typically designed
3.3 Life Cycle Cost and Quality Analysis
to maintain a minimum recommended light level. All daylight In this section we will compare the two schemes based on
harvesting systems use a light level sensor to detect the Uniformity of Illuminance, Luminance Distributions, Glare and
prevailing light level. The signal from the sensor is interpreted Life Cycle Costs.
by a lighting control module in the electric lighting system, and
the electric lighting can be reduced, if appropriate. If the electric
3.3.1 Uniformity of Illuminance
Uniformity of lighting depends on the type and arrangement of
lighting is dimmable, then the artificial lighting may be
the luminaires, on the geometry of the lighting system and on the
continually reduced in proportion to the amount of daylight
type of surfaces being illuminated. Local uniformity of lighting is
available. If the electric lighting is on-off only, then the electric
important for comfort and visual performance. Uneven luminance
lighting must remain on at full output until daylight can meet the
and illuminance can lead to camouflage zones in which there is
entire recommended light level for the space.
inadequate contrast between objects and their surroundings, and
because our eyes have to adapt and re-adapt often, they tire
3.2 Proposed System quickly.IS-3646 [17] recommend that, the ratio of illumination
The suggested architectural lay-in LED luminaire [18] shown in
level between the task area and the background should be less
Figure 2 is an amazing combination of technical innovations,
than 3. This means that ratio of minimum illuminance to
including breakthroughs in optical design, electronics design,
maximum illuminance on the work plane should be around 0.67
mechanical design, and thermal management. The LEDs used in
or more. In practice it is too tight to meet exact ratios. As seen
the suggested LED luminaire are ENERGY STAR qualified
from Table 2, with LED luminaire a uniformity ratio of 0.64 is
products. The core of the innovation is a new way to generate
achieved compared to 0.5 in the case of Fluorescent luminaires.
white light with LEDs. The design of traditional lay-in fixtures is
limited by the use of fluorescent technology. Lighting It can be seen from Figure 3 the spread of illuminance and
requirements dictate the use of multiple large sources that are luminance in one of the office floors of building for both types of
challenging to accommodate, restricting aesthetic possibilities. luminaires. Also one can see an important fact from Table 2, the
LED technology does not have these constraints; enabling total luminous flux from all lamps for all floors of the building
products that is suggested to break the norms of lay-in fixture has come down from 926 Kilo lumens for Fluorescent luminaires
design and create fresh and contemporary solutions. Many to 719 Kilo lumens for LED luminaires an improvement of
fluorescent luminaires are very bright when viewed from a nearly 20%. This suggests that LED luminaires are efficient
distance. This creates a busy appearance with scores of bright enough to spread the luminous flux more evenly on the work
squares scattered across the ceiling. In the suggested luminaire, plane and improve the quality of illuminance than compared to
lens is recessed into the lower reflector to provide mechanical Fluorescent luminaires. In case of Fluorescent luminaires there is
shielding and a soft, low brightness appearance when viewed at a no uniformity in luminance distributions compared to LED
distance - blending into the ceiling plane. luminaires.
Suggested LED luminaire has a luminous efficacy of 73
3.3.2 Glare
lumens/watt compared to the existing Fluorescent luminaire
The Uniform Glare Rating (UGR) is an approximate model that
which has a similar luminous efficacy of 72 lumens/watt. But
expresses the chance of direct glare by luminaires. The higher
LED luminaire has a longer life of 50,000 hours compared to
this figure, the greater the chance of glare.UGR values are
20,000 hours of Fluorescent luminaire. Hence in a life cycle of
usually expressed in steps of 3. For example a typical office
25 years one need not have to replace LED luminaire compared
environment requires a UGR of 19 or less [17].
to more than two times replacement of a Fluorescent luminaire.
As seen from RELUX simulations in Figure 7 both the
From RELUX simulations one can see lot of positives for the
luminaires achieve a UGR of around 19 for four critical observer
suggested LED luminaire. It can be observed from the Table 2
positions, guaranteeing a glare free working environment.
that annual energy costs have come down from Rs 160,000 to Rs

29
 International Journal of Computer Applications (0975 8887)
Volume 9 No.7, November 2010

Figure 7. Glare Rating (UGR) for four observer positions - Fluorescent luminaire (a) to (d) and LED luminaire (e) to (g) for
positions 1, 2, 3 and 4 respectively
3.3.3 Life Cycle Cost Analysis Table 3 Life Cycle Cost Analysis
To evaluate the economic impacts of the LED lighting Details Fluorescent LED
alternative, an analysis was done for 25-year life cycle. As this Luminaire Luminaire
was a new construction project, the LED lighting costs were Luminaire Cost (Including Lamps) Rs 10,600 Rs 22,900
compared to the costs of purchasing the Fluorescent fixtures. The Lamp Life in hours 20,000 50,000
LED light fixtures cost Rs. 4,328,100 compared to Rs. 1,038,800
Annual Energy Costs Rs 159,607 Rs 123,125
of the Fluorescent fixtures almost four times expensive.
Lighting Equipment Cost Rs. 1,038,800 Rs. 4,328,100
The Fluorescent fixtures consumed significantly more energy
Lighting Installation Cost Rs 9,800 Rs 18,900
than the LED fixtures. Each Fluorescent fixture consumes 120W
for the lamps plus 10W for the ballast. The LED fixtures each Wiring & Service/Distribution Cost Rs 1,415,556 Rs 1,092,000
consume 52W. The total lighting load with Fluorescent fixtures Life Cycle Energy Cost for 25 Rs. 10,104,978 Rs. 7,795,268
is 12.74KW as compared to 9.82KW for LED fixtures. Taking a years
power tariff of Rs 6 per KWH and assuming around 6 to 8% rise Life Cycle Cleaning Costs for 25 Rs. 620,455 Rs. 1,196,592
in power tariffs every year it can be seen from Table 3 an overall years
savings of 22% on Life Cycle Energy Costs with LED fixtures as Life Cycle Replacement Costs for Rs. 5,177,194 Replace Only
compared to Fluorescent fixtures. 25 years Once
The LED fixtures offer extremely long lamp life 50,000 hours Total Life Cycle cost Rs. 18,366,782 Rs. 14,430,860
of use before considering replacement. A lifetime of 50,000 Life Cycle Cost per fixture per year Rs. 7,497 Rs. 3,054
hours represents 24 years assuming 8 hour-a-day operation. After
50,000 hours, the lights are not out. Instead, they simply have
reduced light output 70% of the original output. After 50,000 This analysis can be considered a conservative one in that energy
hours, or 24 years, the LED modules in the fixtures can be costs are likely to increase much faster than the 6 to 8% assumed
replaced. Fluorescent fixtures have a life of 20,000 hours; they here. Furthermore, capabilities of the LED light fixtures offer the
have to be replaced more than twice during 25 years life cycle. option to use occupancy control to further reduce the energy
There is an extra cost of Rs. 5,177,194 for replacement in consumption and extend the service life of the fixtures.
comparison with LED fixtures. The total cost of owning an LED
lighting system is much cheaper compared to Fluorescent 4. DAYLIGHT ANALYSIS
lighting system as Life Cycle Cost per fixture per year is less for As analysed in Section 3.1 if daylight harvesting is done we can
LED fixtures than Fluorescent fixtures. save nearly 96% of the energy costs. However in practice not all
portions of the office interior will receive desired amount of

30
 International Journal of Computer Applications (0975 8887)
Volume 9 No.7, November 2010

daylight due to building orientation and room dimensions. With RELUX simulations in Figures 5 and 6 we can see that
Therefore there is a requirement of supplementary artificial proposed glazing SGG Antelio Plus Emerald Glaze [15] allows
lighting during day hours. This section analyses the daylight 22% more day lighting in the office floor compared to the
scheme with existing and proposed glazing type and its impact existing glazing. Proposed glazing is better for solar heat control
on heat gain and air conditioner loads. and reducing cooling energy costs. Proposed Glazing costs nearly
15% more than existing glazing. However proposed glazing is a
In order to gain more insight about the indoor day lighting
larger investment initially but will pay for itself by reducing
performance, one of the office floors was simulated using
heating and cooling costs.
RELUX. The simulations where done for two days 23 June and
22 December under both CIE Overcast Sky and CIE Clear Sky The energy and life cycle cost analysis was done for existing and
for 10AM, 11AM, 12PM,3PM,4PM and 5PM.The times where proposed glazing and the results are summarized in Table 4. It
considered based on the maximum occupancies for similar can be seen from the Table 4 that the air conditioner requirement
offices in India. As seen from computer simulation results in to meet solar heat Gain through glazing has come down from 1.5
Figures 5, 6 and 8 and it can be observed that for the office tonnes with existing glazing to 1 tonne with proposed glazing.
building even during daytime there is requirement of This resulted in an annual saving of 20% on energy costs. As
supplementary illumination from artificial light sources. Places seen Table 4 from the cost of owning the proposed glazing is
far away from windows have to be provided with artificial much cheaper compared to existing glazing over a period of 25
lighting even during clear sky conditions throughout the day. In a years life cycle.
side-lit office, the uniformity of the day lighting will depend
mainly on the dimensions of the rooms and the surface 5. DAYLIGHT HARVESTING
reflectance. If a multi-storey building is to be lit by daylight, To take full advantage of daylight integration, buildings should
there will be limits on its overall plan depth. If length of the have automated controls that either turn off or dim artificial
office is too long comparing with the office width and height, lighting in response to the available daylight in the space. This is
then the rear half of the room tends to look gloomy and traditionally called daylight harvesting. Daylight harvesting
supplementary electric lighting will be required. This is proved starts with lighting controls that are flexible enough to
with RELUX simulations, at nearly 4m from the window the accommodate the changing requirements of occupants in a space.
illuminance drops to less than 500 lux under Overcast Sky and at Control flexibility improves lighting energy performance by
7m under Clear Sky. As seen from the results there is no establishing a base level of illumination and then encouraging
requirement of artificial lighting for the areas which are 4m to the use of only those lights that are needed for the activity at
7m away from the window hence there could be significant hand. It also increases occupant satisfaction through user control.
saving in energy in these areas. Further savings in cooling energy On the other hand, while some occupants are quite conscientious
and heat rejection could be obtained due to less sensible heat about manually tuning lighting for their needs, including
gains generated by artificial lighting fittings. turning off or dimming lighting when not needed, automatic
systems tend to result in greater energy savings over the long run.
The existing structural glazing is provided by Saint Gobain Glass
They should always be supplemented with manual override to
type SGG Antelio Plus Blue Ray [15] it is a double glazed unit
accommodate individual differences.
with a relative heat gain of U value of 2.8w/sqmK and light
transmission of 39%. Mumbai requires cooling throughout the Automated systems usually include optical sensors (photocells)
year. Hence it is advisable to go for Low-Solar-Gain Low-E that read ambient light levels to both maintain a base level of
Glass for glazing. Low-E glass provides a higher level of visible illumination, by using as much free natural daylight as possible,
light transmission for a given amount of solar heat reduction. and occupancy sensors to shut lights off when spaces are
Variants on low-solar-gain low-E coatings have also been unoccupied. Using an integrated occupancy and daylight
developed which may appear slightly tinted. This type of low-E dimming sensor will not only guarantee the correct lighting level
product reduces heat loss in winter and substantially reduces in a room at any time but will also make sure that lights are
solar heat gain both in winter and in summer. Thus, low-solar- turned off when a room is not in use. Daylight harvesting control
gain low-E glazing is ideal for buildings located in cooling- strategies can be established so that the controls can be operated
dominated climates. The best possible option is to go for Saint manually by users or automatically using photo sensors. Since
Gobain Glass type SGG Antelio Plus Emerald Glaze a double automatic strategies do not depend on human initiative, they are
glazed unit with low-e coating and a light transmittance of 47% generally more effective at saving energy.
and relative heat gain of U value of 1.77w/sqmK. There by
improving the light transmittance by near 22% and reducing heat 5.1 Combined Occupancy & Daylight
gain thus reducing cooling requirement by 37%. Further the ratio Dimming Sensors
between Solar Heat Gain Coefficient and Visual Transmittance Occupancy Sensors are extremely sensitive PIR Motion Sensors.
is called the light-to-solar gain ratio (LSG.) This provides a They can detect much finer movements and also are a lot smaller.
gauge of the relative efficiency of different glass types in Although simple in concept Occupancy Sensing is probably the
transmitting daylight while blocking heat gains. The higher the single most effective energy saving strategy. For energy saving
ratio number the brighter the room is without adding excessive lighting a full Office Automation system is not necessary.
amounts of heat. The LSG ratio is higher in case of proposed Decentralise, reliable lighting controls often do a much better job
glazing type at 1.4 compared to 0.91 in case of existing glazing (less configuration, less maintenance). Therefore individual
type.

31
 International Journal of Computer Applications (0975 8887)
Volume 9 No.7, November 2010

daylight dimming is suggested for each of the LED luminaire with occupancy & daylight sensor built within the fixture.

Figure 8. Interior Illuminance levels in the office floors during different hours of the day for dates June 23 and December 22
Table 4 Energy and Life Cycle Cost Analysis of Structural Glazing
Existing Glazing Proposed Glazing
Type SGG Antelio Plus Blue SGG Antelio Plus Emerald
Ray Glaze
Light Transmission 39% 47%
U Value(W/m2K) 2.8 1.77
Solar Factor 0.37 0.31
Shading Co-efficient 0.43 0.35
Tonnage Requirement of Air conditioner to meet Solar Heat Gain through Glazing 1.5 1
Annual Energy Costs Rs. 18,792 Rs. 15,284
Initial Cost of Glazing Rs. 465,500.00 Rs. 558,600.00
Cost of Air-conditioning to meet Solar Heat Gain through Glazing Rs. 20,000.00 Rs. 16,000.00

Life Cycle Glazing Cleaning and Maintenance Cost Rs. 781,482 Rs. 781,482
Life Cycle Energy Costs for 25 years Rs. 1,223,802 Rs. 995,359
Total Life Cycle Cost Rs. 2,486,784 Rs. 2,355,441
Life Cycle Cost per Sq.m of Glazing per year Rs. 2,991 Rs. 2,833

32
 International Journal of Computer Applications (0975 8887)
Volume 9 No.7, November 2010

5.1.1 Individual Daylight Dimming - One Sensor per months of the year. Four different schemes where considered,
one with only LED lighting and no occupancy detection or
fitting daylight harvesting, three of the daylight harvesting schemes
Integrated Occupancy and Daylight Harvesting Sensor suggested where considered with different control schemes like presence
[19] for the project is shown in Figure 9. These sensors are control in daylight section of the office floor using Manual
specifically designed for very demanding applications, e.g. On/Off and Manual On & Auto/Off. Similarly for presence
persons working concentrated at a PC where the only motion is control in artificial lighting section using Manual On/Off and
typing on a keyboard. When there is no daylight, this sensor Manual On & Auto/Off.
work just like the simpler On/Off sensors. However, as soon as a
certain amount of daylight is available, the artificial light will be
reduced gradually.

Figure 9. Integrated occupancy and daylight harvesting sensor

suggested for the project

5.1.2 Computer Simulations for Sensor calculations

The Figure 10 shows the detection range of one sensor when
placed at the centre of the office building. The size of this
observation area can be adjusted by pulling out the shading ring
around the sensor lens. The sensor has detection capabilities in
360o, it has a circular detection range for seated persons at
2.50m, tangential at 10 m and radial at 6m.
Using RELUX software, the sensor layouts where fixed and the
detection ranges of all the sensors put together where simulated
as shown in Figure 19. One can see from the results that the
sensors presence detection range covers almost entire office Figure 10. Detection range of selected sensor as simulated in
floor there by effectively detecting occupancy and light levels for RELUX software
energy efficient daylight harvesting.
In comparison to Fluorescent lighting scheme without daylight
5.2 Energy Cost Analysis harvesting and lighting controls in Daylight Harvesting Scheme
Using RELUX-Energy, energy evaluation was done for the office 3, which incorporates Combined Occupancy & Daylight
floor using EN15193 standards. The software separates the day Dimming Sensors, we can be seen that maximum energy saving
lit section (75 m2) and artificial light sections (65 m2) in the up to 70% can be achieved over the Fluorescent Scheme. Further
office floor. The energy evaluation gives details of energy this scheme also reduces the Life Cycle Cost per fixture per year
consumption profiles for different sections within the office floor from Rs 3,054 to Rs 2,095 a saving of further 33% as
for different daylight control schemes. As we can see from the summarised by Table 6. Compared to the existing Fluorescent
Table 5 and Figure 11 which summarizes the energy scheme nearly 80% can be saved in energy costs and Life Cycle
consumptions under different control schemes for different Cost per fixture per year.

33
 International Journal of Computer Applications (0975 8887)
Volume 9 No.7, November 2010

Figure 11. Energy costs with different lighting schemes

Table 5 Energy cost comparison with different lighting schemes

Only LED Lighting Daylight Harvesting Daylight Harvesting Daylight Harvesting
Scheme 1 Scheme 2 Scheme 3
Daylight Section (75 m2)
Presence Control Manual Manual Manual / Auto Off
Daylight Depending Control System Manual Manual Automatic,
Daylight
dependent
Percentage of Total Energy 41% 46% 5%
Consumption in Day lit Section
Artificial Light Section (65 m2)
Presence Control Manual Manual /Auto Off Manual/Auto Off
Percentage of Total Energy 59% 54% 95%
Consumption in Artificial lighting
section
Parasitic Power in Watts 6538 6538 6538
Annual Energy Costs Rs 123,126 Rs 92,370 Rs 81,426 Rs 46,218

34
 International Journal of Computer Applications (0975 8887)
Volume 9 No.7, November 2010

Table 6 Life Cycle Cost Comparison for LED Lighting and [3]. Kurian CP, Aithal RS, Bhat J, George VI. Robust control
Integrated Daylight & LED Lighting with Daylight dependent and optimization of energy consumption in daylight-articial
lighting control system light integrated schemes. Light Res Technol 2008;40(1):7
24.
Illumination Provided by Only LED Daylight [4]. Doulos L, Tsangrassoulis A, Topalis F. Quantifying energy
lighting Harvesting savings in daylight responsive systems: the role of dimming
Annual Energy Costs Rs. 123,126 Rs 46,218 electronic. Energy Build 2008;40(1):3650.
Additional Costs on Lighting control NA Rs 378,000 [5]. Loutzenhiser PG, Maxwell GM, Manz H. An empirical
system (Includes occupancy sensors, validation of the daylighting algorithms and associated
control circuitry and installation costs ) interactions in building simulation programs using various
shading devices and windows. Energy Int J
Life Cycle Energy Cost for 25 years Rs 7,795,268 Rs 2,885,311 2007;32(10):185570.
Total Life Cycle Cost for 25 years Rs. Rs. 9,898,903 [6]. Chel A, Tiwari GN, Chandra A. A model for estimation of
14,430,860 daylight factor for skylight: an experimental validation using
Life Cycle Cost per fixture per year Rs 3,054 Rs 2,095 pyramid shape skylight over vault roof mud-house in New
2 Delhi (India). Appl Energy 2009;86(11):250719.
Life Cycle Cost per m of total floor Rs 610 Rs 426
area per year [7]. Ruck NC. International Energy Agencys solar heating and
cooling task 31 daylighting buildings in the 21st Century.
Energy Build 2006;38(7):71820.
6. CONCLUSION [8]. To DWT, Leung KS, Chung TM, Leung CS. Potential
Faced with the skyrocketing cost of energy and environmental energy saving for a side-lit room using daylight-linked
concerns, builders, architects and lighting specialists are uorescent lamp installations. Light Res Technol 2000;
increasingly turning to day lighting as a primary source of 34(2):12133.
illumination in mainstream construction. Day lighting will
[9]. Li DHW, Lam JC. Evaluation of lighting performance in
provide tremendous operating cost reductions if properly
ofce buildings with daylighting controls. Energy Build
integrated with an electrical lighting control system. For
2001;33(8):793803.
successful daylight integration, certain principles need to be
followed in terms of optimum building placement: the location, [10]. Li DHW, Lam TNT, Wong SL. Lighting and energy
design and selection of materials for fenestration (windows, performance for an ofce using high frequency dimming
skylights, etc.) and electrical lighting design. In general, the controls. Energy Convers Manage 2006;47(910):113345.
earlier in the design process of new buildings that day lighting [11]. Li DHW, Lam TNT, Wong SL, Tsang EKW. Lighting and
issues are addressed, the more successful the daylight harvesting cooling energy consumption in an open plan ofce using
project will be. The designer should evaluate if the quality, solar lm coating. Energy Int J 2008;33(8):128897.
distribution or amount of day lighting could be improved during
pre-design and schematic design phases. Simulation software [12]. Li DHW, Lam TNT, Chan WWH, Mak AHL. Energy and
like RELUX can be used to evaluate the full integration of cost analysis of semi-transparent photovoltaic in ofce
daylight harvesting and electric lighting controls with buildings building applications. Appl Energy 2009;86(5):7229
characteristics. [13]. Ward GL, Shakespeare R. Rendering with RADIANCE. The
art and science of lighting visualization. Los Altos, CA:
In summary,
Morgan Kaufman; 1998.
1) An in-depth analysis has to be performed on the daylight [14]. CIBSE. Applications manual: window design. Chartered
harvesting potential of a building at the earliest possible stage Institution of Building Services Engineers, London; 1987.
before construction.
[15]. Saint Gobain India. 2010. Reflective Glass with Nano
2) Total building automated lighting controls should be used to Coating - SGG ANTELIO PLUS. http://in.saint-gobain-
maximize daylight harvesting benefits and energy savings. glass.com/
3) Energy efficient lighting equipment such as LED fixtures can [16]. Philips. 2010. DPA2G9LP3FT 3 Feet 9 Cell 2x2 3 Lamp
be used to help cut lighting operational costs TT5 Parabolic. http://www.lightolier.com/
[17]. Bureau of Indian Standards. Code of practice for interior
7. REFERENCES illumination (IS 3646). 1992
[1]. Wu MKT, Lam KK. Ofce lighting retrot using T5
uorescent lamps and electronic ballasts. Hong Kong Inst [18]. Cree Lighting. 2010. LR24-38SKA35 Architectural Lay-ins.
Eng Trans 2003;10:5560. http://www.creelighting.com/

[2]. ztrk LD. Determination of energy losses in lighting in [19]. Luxomat. 2010. PD9-M-DIM-GH-FC.
terms of good vision efciency. Archit Sci Rev http://www.luxomat.com/
2008;51(1):3947

35