03-Chapter - 3 Motors PDF
03-Chapter - 3 Motors PDF
03-Chapter - 3 Motors PDF
Chapter - 3
Electrical Utilities
3.1
Electrical Motors
Electric motors convert electrical energy into mechanical energy. There are
basically 3 types of motors:
1.
2.
3.
AC Induction Motors
AC Synchronous Motors
DC Motors
D.C. Motors
Brushless D.C
Brush D.C
Shunt Wound
Separately Excited
Series wound
Compound wound
Induction
Reluctance
Split Phase
Squirrel cage
Linear
Induction
Synchromous
Slip ring
Synchronous
Electric motors are inherently very efficient. Their efficiencies vary from 85%
to 95% for motors of sizes ranging from 10 HP to 500 HP. It is still possible to
improve the efficiency of these motors by 1 to 4% by improving the design of motor
.
3.1.1
a)
If the voltage is in Volts and the current in Amperes, the power will be in Watts (w).
The power in Watts divided by 1000 is kilowatts (kW). The power input to the
motor varies with the output shaft load.
Electrical Power input (kW) =
Variations of motor efficiency and power factor with load are shown in Fig. 3.1
Torque speed and current speed characteristics of different types of rotors are
shown in Fig.3.2. The load vs full load current is shown in Fig. 3.3. The following
may be noted from these curves.
75
3.
4.
5.
6.
7.
100
1.0
90
0.9
80
0.8
70
0.7
60
0.6
50
0.5
40
0.4
30
0.3
20
0.2
10
0.1
100
90
SMALL MOTOR
(BELOW 25 HP)
80
% Full Load Current
2.
The motor efficiency remains almost constant upto 50% load. Below 50% load,
the efficiency drops significantly till it reaches zero at 0% load.
At a particular operating voltage and shaft load, the motor efficiency is fixed by
design, it cannot be changed externally.
The power factor reduces with load. At no load the p.f. is in the range of 0.05 to
0.2 depending on size of the motor.
At no load, the power consumption is only about 5% or so, just sufficient to
supply the iron loss, friction and windage losses.
The no load current is however of the order of 30% to 50% of full load current.
This amount of magnetizing current is required because of air gap in the motor.
The starting torque is 100% to 200%, the maximum torque is 200% to 300% of
rated torque.
The starting current remains at a high value of more than 500% of rated current
upto 75% to 80% speed and then drops sharply.
70
60
LARGE MOTOR
(25 HP & ABOVE)
50
40
30
20
25
75
50
100
pf
1.
Motors can run without problems for 20 years or more with good protection and
routine maintenance. However, if they are running inefficiently, it is worthwhile
replacing them as running costs are much more than first costs. Motors can be
considered as consumable items and not capital items, considering the current
energy prices. The importance of running cost can be seen from Table 3.1. The
following points may be noted:
Table 3.1 : Importance of Motor Running Cost
0
0
25
50
75
100
% Load j
Efficiency
7.5
+ Power Factor
Low
Efficiency
37
High
Efficiency
Low
Efficiency
High
Efficiency
Efficiency
0.86
0.88
0.92
0.93
8.72
8.52
40.22
39.78
Running Hours
6000
6000
52320
51120
6000
241320
6000
238680
Running Cost
209280
204480
965280
954720
2092800
2044800
9652800
9547200
12000
12000
70000
70000
0.57
0.59
0.72
0.73
1.
2.
Fig 3.2 : Performance with Tee Bar, Deep Bar, Trapezoidal and Double Cage
Rotors
76
Even a small motor of 7.5 kW consumes, at full load, electricity worth Rs. 20
lakh in 10 years. Similarly, a 37 kW motor consumes about Rs. 1 crore worth of
electricity in 10 years.
The first cost is only around 1% of the running cost for 10 years, hence running
costs are predominant in life cycle costing.
77
3.
4.
3.1.3
1.
2.
3.
4.
5.
6.
7.
8.
9.
Current (star)
Current (Delta)
Power factor (star)
Power factor (Delta)
Efficiency (star)
Efficiency (Delta)
Speed (star)
Speed (Delta)
Change overline
Table 3.2 Shows the effects of oversized motors on the energy bill and
investment
15
30
55
15
89
16.85
101100
15
89
16.85
101100
15
84
17.85
107100
0.89
18.93
25000
-
0.75
22.44
55000
0.50
35.70
6000
24000
95000
30000
70000
Voltage (V)
Current (A)
Power Factor
Power Input (kW)
Speed (rpm)
78
79
Before
Implementation
(Delta)
415
18.5
0.5
6.72
1469
After
Implementation
(Star)
415
9.5
0.87
5.96
1454
Saving /
Improvement
9.0
0.37
0.76
Energy Saving
Energy Saving
Energy Savings
Annual Saving
Investment
Payback Period
:
:
:
:
Annual savings
Annual saving
Investment
Payback period
:
:
:
:
1,16,000 kWh
Rs. 0.47 Million
Rs. 0.5 Million
13 months
Case Study 2: Use of Soft Starter to Facilitate Large Motor Starting with Power
Supply from Captive D.G. Set
Case Study 4: High Efficiency Gear in Place of Low Efficiency Gear (for a
Reactor with Worm Gear )
Brief
Energy Saving
Application
Motor Details
Starting Using Star/Delta Starter
Initial Starting kick
Maximum Starting Current
Continuous Current
Low efficiency
gear
Worm gear
Saving/Improvement
7.5
3.75
3.75
Actual Motor
3.75
3.75
3.0
3.0
0.75
0.75
Input (kW)
Case Study 5:
Parameter
Brief
The Ring Frame motor rating was 40 kW. A standard efficiency motor was
compared with an energy efficient motor as given in table below:
Energy Saving
Standard Motor vs EE Motor
Benefits : Starting current kick reduced by about 60%. Any dip in voltage at the
main busbar of DG Set is reduced. The expenditure on maintenance of the motor
and the attached mechanical load is also reduced.
Description
Motor rating, kW
40
40
Efficiency %
92
94.5
96.22
92.54
44
44.5
2.187
2.080
9564
Brief
Valve position
20% open
Power consumption
53.5 kW
Fully open
40 kW
Power Saving
13.5 kW
80
81
Standard
Energy Efficient
(Low Eff) Motor
(EE) Motor
Output
Frame Size
Supply System
RPM
Efficiency
Fan
Ambient
Taking annual running hours
Input kW at full load
Input kW difference
Unit Rate (Rs/kWh.)
Annual Savings
Net Unit Price (Rs.)
Price difference
Payback
3.1.4
Standard Motor
15 kW
160 L
415 V +_ 6%; 50 Hz V +_ 3%
1445
89%
Plastic
40 C
7165
16.85
15 kW
160 L
415 V +_ 10%; 50 Hz V +_ 5%
1475
93%
C.I
50 C
7165
16.13
0.72
4
20,635
32200
10,260
19 months
21940
-
Notes
New Motors
Superconductor
2 to 10
Copper Rotor
1 to 3
Switched Reluctance
Permanent Magnet
5 to 10
Written Pole
3 to 4
Controls
MagnaDrive
Up to 60
PAYBACK drive
Up to 60
Advanced ASDs
Emerging motor system improvements can be categorized into the following three
areas of development opportunities:
1.
Technology
3.2
3.1.5
Electric Furnaces
Electricity is a very clean but costly fuel for heating and melting applications. There
are number of advantages in electricity use like improved product quality due to
absence of fuel impurities, excellent power control, clean environment (pollution is
transferred to central power station) and high efficiency at end use point. But since
conversion efficiency of fuel to electricity is only 35% at the power station, the
overall efficiency from fuel to end use heating is likely to be 15 to 25%. Hence
keeping the overall energy scenario in view, electricity should be used for only
special heating applications. Fuel should be used directly to the extent possible. For
many conventional heating applications like billet heating and heat treatment,
alternate fuels, especially natural gas where available, must be considered. Many
companies have changed over from electric heating to heating by other fuels to
reduce costs.(However for Induction and Arc Furnances no alternatives are
presently available ) Table 3.4 gives the inter-fuel substitution.
Primary specific electrical energy savings for particular motor applications are
summarized in Table 3.3.
82
83
Cost
Heat Value
Coal
Oil
Natural Gas
Electricity
Rs. 2000/MT
Rs. 20/Kg
Rs. 8/Nm3
Rs. 4.50/kWh
4000 kCal/Kg.
10000 kCal/Kg.
9000 kCal/Nm3
860 kCal/kWh
Energy Balance
Cost Per
1000 kCal
Rs. 0.50
Rs. 2.00
Rs. 0.88
Rs. 5.23
Electricity is used in arc furnaces, induction furnaces, heat treatment furnaces, billet
heaters, ovens, infrared heaters, etc.
Case Study 6 : Replacement of Electric Oven by Gas Fired Oven in an
Engineering Industry
Energy
Percentage
(kWh/tonne)
(%)
Input Energy
660
100
Useful Heat
380
58.5
Coil I R
130
20
Radiation Losses
97.5
15
Conduction Losses
34
5.2
Other Unaccounted
18.5
1.3
Brief
Energy Input
822.75 kWh
Heat In Charge
167.00 kWh
Electrical Oven
Annual Savings:
Payback Period
3 Months
204.00 kWh
Outer Bell
136.10 kWh
Inertia Loss
250.90 kWh
44.50 kWh
Unaccounted Loss
20.25 kWh
Steel Plant 2 : 30 T
Furnace
Energy Input
= Rs. 3,65,040
Cost of LPG Fired Oven
Soaking Heating
Electrical Energy
426
682
Carbon Combustion
126
126
70
70
48
64
Total
Energy Output
670
942
(exothermic)
:
:
:
:
:
Grey Iron
3200 Kg
1600 kg/hr.
733 kW
968 volts
392
426
Exhaust Gases
104
120
57
76
Electrical Losses
47
60
170
Conduction, Radiation
40
60
12
84
12
Unaccounted Losses
18
18
Total
670
942
85
Energy (kWh)
Percentage
37.4
100
3.8
10
13.0
8.6
23
Useful Heat
10
27
Unaccounted Losses*
10
27
Energy Saving
Annual energy saving
Investment
Payback period
: 30,000 kWh
: Rs.61,000/: 13 months
a) Operate at full power and capacity as far as possible to get as high a utilization
rate as possible. Poor capacity utilization of electric furnaces cause a large
wastage of energy. Holding periods can be kept to a minimum. Separate
holding furnaces can sometimes be useful.
b) Minimise tapping time and frequency to reduce radiation losses and to reduce
operation at low power levels.
c) Charging system should be such that charging time and frequency are
minimised. Possibility of charge compacting and preheating can be explored.
d) Molten metal handling and transfer system including ladles can be designed in
such a fashion that transfer time and loss in temperature are minimised. Ladle
preheating system lead to savings. Well insulated ladles are also necessary.
e) Opening of furnace lids, slagging door etc. must be minimised.
f) For heat treatment furnaces, production can be so planned that once a furnace is
started, it can be utilised continuously, otherwise a lot of energy is wasted in
heating the furnace itself. Capacity utilisation is also very important.
g) For many heat treatment applications, it may be worthwhile collecting jobs so
that full capacity utilisation is achieved.
h) Weight of jigs and fixtures for heat treatments should be minimised.
i) Surface temperature may be kept at 45oC to 60oC for heat treatment furnaces to
reduce radiation losses.
j) Process parameters, like heat treatment cycle time and temperatures, have to be
checked.
It was decided to replace the 28 kW oven with a smaller 12 kW oven. The important
difference between the old oven and the new oven are highlighted in Table below.
Brief
The plant is equipped to produce about 350 tonnes of Malleable Iron and S.G. Iron
Castings per month.
Steel scrap is melted in two 4 tonne / 1150 KVA mains frequency furnaces. The
product mix consists of a large number of relatively low and medium weight
castings. Moulds are made on automatic moulding machines (Pneumatic). The
castings are shot blasted, annealed in electric furnaces (600 kW). Fettling and
grinding also uses pneumatic tools. These are fed by two compressors of 93 kW
each, working one at a time.
The present production level is around 220 Tonnes / month. Energy consumption is
about 700,000 kWh/month with a maximum demand of around 2700 kVA.
Approximate percent consumption of major equipments are given in the Table
below.
86
87
% of Total
load
Total
load
100
Melting
Furnaces
60
Annealing
furnaces
17.14
Compressors
11.48
Sand
Plant
2.55
Other
Loads
6.52
Energy saving was achieved through operational improvement like compacting the
scrap and loading it with crane, closing the furnace lid, shutting off the ventilation
fans for capacitor cooling during favorable ambient conditions etc.
Energy Saving
Brief
A cable manufacturing industry, has several annealing ovens, which account for a
significant portion of the electricity consumption. A 317 kW oven is used for
annealing aluminum conductor in large drums. The oven was large for the jobs
being handled. It was redesigned for the job, cutting ceiling height and the
insulation was changed to ceramic fibre. The observations are as follows :
Parameters
Parameter
Saving/Improvement
Before
After
Implementation
Before
After
Implementation
Implementation
SEC (kWh / T)
900
700
( - ) 200
10
(-)6
Production
( - ) 1,22,070
500
( - ) 1,00,000
15
NIL
Savings/Improvement
Implementation
1930
500
( - ) 1430
8.5
3.5
( - ) 5.0
3.0
5.0
(+ ) 2.0
( - ) 30,000 kWh/annum
Energy saving
capacitors (HP)
Annual Savings
Investment
Payback period
Brief
These inefficient arc furnaces were replaced with one medium frequency (3000 Hz)
induction furnace of capacity 125 kW, having two pots 50 kg and 100 kg
respectively. The 50-kg pot is rated at 90 kW while for the 100-kg pot rating is
125 kW.
Energy Saving :
Particulars
Monthly energy
consumption
Metal tapped per month
No of heats per month
Specific energy
consumption per Mt.
Annual energy
consumption
Cost of energy
Annual energy savings
Annual cost savings
Investment incurred
Payback period
Units
Before implementation
(Indirect arc Furnaces)
After
impleme
ntation
Improve
ment
%
Improve
ment
8267
12447
60
kWh
30 kg
IAF
14434
80 kg
IAF
6280
Total /
avg.
20714
Kg
No
kWh
13970
438
968
2100
27
2990
16070
465
1085
13974
330
592
-2096
-135
494
-13
-29
60
kWh
173208
75360
248568
99204
-149364
-60
Rs
kWh
Rs
Rs
Years
621816
270542
892359
-536217
-60
356142
149364
536217
1000000
1.86
2
88
89
The pump-up test described above gives only an estimate of the compressor
capacity and cannot be considered as very accurate. It is only a simple practical
method under site conditions with minimal instrumentation. A more scientific
method of conducting the pump-up test with proper installed instrumentation is
available in IS:5456-1985.
The power consumption can be measured with portable power meter or energy
meter and the specific power consumption (kW/100cfm) can be calculated. Some
of the common causes of higher Specific Power Consumption are:
-
Brief
It is recommended to replace absorption type air dryer with refrigeration type dryer
as absorption dryer uses 10% - 15% purge air for re-generation of desicant .
Energy Saving
Saving Obtained by installing Refrigeration Dryer in Compressor
Parameter
Actual load (kW)
Total running hours / year
Annual Energy consumption
(kWh)
Before
Implementation
16.6
1800
After
Implementation
14.11
1800
Saving /
Improvement
2.49
-
29880
25398
4482
15780
94000
6
Q=
90
In an engineering unit, moisture traps were found stuck up in either open or closed
condition thus making a loss of compressed air continuously or corroding of
pipeline and other networking devices. On rectifying the faults, savings were as
under:
Energy Saving
Particulars
Annual total energy savings, kWh
Annual Cost savings, Rs. (million)
Cost of implementation Rs. (million)
Simple payback period (months)
91
Leakage tests can be done separately for each section of the plant by isolating the
supply to compressed air to the remaining sections of the plant during the leakage
test.
Case Study 14 : Cost of compressed air leakage from holes at different
pressures
QxT
T+ t
Where,
Q = Compressor capacity, in m3/min (as estimated from the pump-up test)
T = Time on load ,min
t = Time on unload, min
Leakage points can be identified from audible sound. For small leakage, ultrasonic
leakage detectors can be used. Soap solution can also be used to detect small
leakage in accessible lines. The following points can help reduce compressed air
leakage:
a)
b)
c)
d)
e)
f)
g)
92
0.211
0.0207
744
1/32
0.845
0.083
2981
Cost of Wastage,
Rs. (for 8000 hrs/year)
@ Rs. 4.50/kWh
3.38
0.331
11925
1/8
13.5
1.323
47628
1/4
54.1
5.3
190865
1/64
0.406
0.069
2485
1/32
1.62
0.275
9915
1/16
6.49
1/8
26
4.42
159120
1/4
104
17.68
636480
Leakage of compressed air is a major reason for the poor overall efficiency of
compressed air systems. It may be noted that, at 7 bar (100 psig), about 100 cfm air
leakage is equivalent to a power loss of 17 kW i.e. about Rs. 0.62 million per annum.
1/64
1/16
The leakage level can be estimated by observing the average compressor loading
and unloading time, when there is no legitimate use of compressed air on the shop
floor.
Power
Wasted kW
Energy Saving
Particulars
Annual total energy savings, kWh
Annual Cost savings, Rs. (million)
Cost of implementation Rs. (million)
Simple payback period (months)
Air Leakage
Scfm
Orifice Diameter
(in inches)
1.10
39719
93
Brief
Units
Inlet pressure
bar, abs
Air flow
scfm
100
100
1.
Length of pipe
meter
100
100
75
100
Pressure drop
bar
2.1
0.5
psi
30.9
7.3
3" Header
4" Header
Normally, the velocity of compressed air should not be allowed to exceed 6 m/s.
Pipe fittings like valves, elbows & no. of bends etc. also contribute to additional
pressure losses.
Case Study 16 : Pressure Drop (in bar) In different Pipe sizes of 100 ft. Length
Brief
50
75
100
125
150
10
4.39
3.70
2.68
2.09
1.72
1.46
2
3
4
20
50
100
0.54
0.43
0.41
0.46
0.36
0.34
0.33
0.26
0.25
0.26
0.20
0.19
0.21
0.17
0.16
0.18
0.14
0.14
200
0.24
0.21
0.19
0.16
0.14
0.11
Manage end use of air. This includes proper understanding of end use
requirement, often termed as the ultimate goal to be achieved.
2. Match the system with the end use requirement in the most efficient way.
3. Improve the efficiency of compressors and related equipments through
maintenace.
4. Scouring (moisture removal) by compressed air can be replaced by high
pressure blowers. The energy saving can be 80%.
5. Material conveying applications can be replaced by blower systems or
preferably by a combination of belt/screw conveyers and bucket elevators.
6. For applications like blowing of components, use of compressed air amplifiers,
blowers or gravity-based systems may be possible.
7. Use of compressed air for cleaning should be discouraged.
8. Replacement of pneumatically operated air cylinders by hydraulic power
packs can be considered.
9. Use of compressed air for personal comfort cooling can cause grievous injuries
and is extremely wasteful. If a " hose pipe is kept open at a 7 bar compressed
air line for personal cooling for at least 1000 hours/annum, it can cost about
Rs. 1.0 lakh/annum. Operating cost of a 1.5 TR window air conditioner
for the same period would be only about Rs. 12,000/- per annum.
10. Use vacuum systems in place of venturi system.
11. Mechanical stirrers, conveyers, and low-pressure air may mix materials
far more economically than high-pressure compressed air.
12. Air conditioning systems can cool cabinets more economically than
vortex tubes that cool by venting expensive high pressure air.
Case Study 18 :
Brief
Case Study 1 7 : Reduction in pressure drop in the compressed air.
Brief
A leading bulk drug company has three reciprocating compressors having the
capacity of 280 cfm and the corresponding power consumption was 58 kW at 7.5
kg/cm2. The actual air requirement at user end was only 6.0 kg/cm2. The pressure
drop in the system was taking place of the order of 1.5 kg/cm2. On analysis, it was
found that high pressure drop in the system was due to under sizing of the piping.
The existing(2") piping was replaced by suitable sized piping (3"). Overall saving
in energy was as under:
Energy Saving
Particulars
Energy Saving
Particulars
Annual total energy savings, kWh
Annual Cost savings, Rs. (million)
Cost of implementation Rs. (million)
Payback period (years)
The chemical plant has five process fermentors, where the compressed air is used as
raw material and as well as for the agitation. Five large compressors in use were of
reciprocating, single stage, double acting, horizontal, non-lubricated type having
the capacity of 4000 m3/hr, rated pressure 1.5 kg/cm2, rated motor 200 kW. In view of
the variations in the load and the energy lost due to bleed off, variable speed drive
was installed to adjust the speed based on requirement.
1320
0.580
1.52
2.0
16
95
Case Study 19 :
Brief
Brief
In a paper and pulp industry, for supplying instrument air, two compressors working
at 10 kg/cm2 and 1 m3 per minute were running. The air leakage in the system
increased and the air compressors started running for more than 20 hrs a day to meet
the requirement. Upon installation of the hour meters, it became easy to monitor the
running hours of compressors and also estimate the air consumption as well as
leakages .The leakages were arrested and also a reduction in total running hrs of
compressors was achieved . Savings effected were as under:
Energy Saving
Energy Saving
Particulars
Particulars
Actual energy savings
Annual total energy savings, million kWh
0.873
Annual Cost savings, Rs. (million)
2.9
Cost of implementation Rs. (million)
2.0
75,000
0.3
2,000
<1
Brief
Brief
In an automobile plant, it was reported that the maximum air pressure requirement
at machine end is 6.5-7.0 kg/cm2 but plant is maintaining 7.0- 8.5 kg/cm2.
Generating higher pressure than required is a loss of power i.e roughly 4% loss in
maintaining 1 kg/cm2 higher pressure. The details of losses are as follows:
Energy Saving
Pressure requirement
: 6.5-7.0 kg/cm2
Pressure maintained
: 7.0-8.5 kg/cm2
Rated Compressor power
: 75 kW for 458 cfm compressor
Rated Avg. compressor power
: 65 kW
( ON and OFF load)
Avg. compressor power (ON and OFF load)
after reduction in pressure by 1 kg / cm2 : 62.4 kW
Particulars
Annual total energy savings,kWh
Annual Cost Savings, Rs.
Cost of Implementation
Payback Period
96
A leading automobile unit, which produces 2 wheelers, has seven large compressors
with a rated output of 7500 cfm. Compressors consume about 60 lakh units annually
(i.e about 12 % of total power consumption). The compressed air is mainly used in
pneumatic tools, instruments, control valves. During the recently concluded energy
audit, it was observed that the leakage in the system was 1400 cfm, which was
about 20% total air consumption. After arresting the leakages, the savings to the
company were as under:
Energy Saving
Particulars
0.864
3.0
0.2
97
3.4
Pumping of water and blowing of air are very basic needs. This can be done by
either positive displacement systems like reciprocating pumps, gear pumps, roots
blowers etc. or by the centrifugal pumps and blowers. Centrifugal devices do not
use a rubbing barrier as in positive displacement equipments but depend upon the
kinetic energy imparted to water or air due to rotating motion. They are used in
majority of applications needing FLOW due to their inherent reliability,
ruggedness and reasonably good efficiency.
Basic energy is proportional to the product of FLOW and TOTAL PRESSURE
HEAD. The head is mainly friction head and static head.
The static head is a function of choice of location and inherent system design while
the friction head varies inversely with fifth power of pipe diameter and other flow
passages as also to the square of FLOW. The friction based energy is thus decided
by CUBE OF FLOW.
The equations relating rotodynamic pump performance parameters of flow, head
and power absorbed, to speed are known as the Affinity Laws and are as follows:
Q N
H N2
3
P N
Where:
Q = Flow rate
H = Head
P = Power absorbed
N = Rotating speed
Efficiency is essentially independent of speed
Flow: Flow is proportional to the speed
The operation of fan is similar. There is no static head. The head in the heat
exchanger is small compared to head lost in ducts, bends and dampers. In addition
to the elegant universally applicable variable speed method of capacity control, we
can use variable pitch designs and inlet guide vane control for fans.
3.4.1 Energy Saving in Pumps
Basically, for an ideal system with given piping, the open valve system
characteristics should cut the pump curve at BEP flow (Best Efficiency Point Flow).
But this is rarely possible. Hence, a practical system suffers in varying degrees by :
1.
2.
3.
4.
5.
6.
7.
8.
9.
Loss due to drop in efficiency of the pump for off duty point operation.
Loss in throttling valve to some extent.
Piping size of historical value and layout which can be changed.
A pump of old design which has room for improvement.
An old heat exchanger, where the design emphasis may be on lesser material
content (low first cost) and smaller space giving relatively higher drop for same
function.
It is very important to realise that the effects of flow may be proportional to first
power of Q (heat exchangers have even Q0.8), so that reduction in flow by even
marginal percentage brings about considerable energy savings.
An unquestioned Static Head can be altered in some cases by re-layout and
other innovative changes.
Very large drop (relative) in throttling valve which can be minimised or
eliminated.
There is a fair chance of improving new working point pump efficiency to
increase savings.
The methods for saving energy by altering the pump characteristic are briefly as
under :
1.
2.
3.
4.
5.
6.
Brief
Optimizing the energy efficiency of a pumping system needs attention, action and
investments to use the highest possible pump efficiency, to use the pump around its
Best Efficiency Point (BEP) which is at a unique flow, to minimize pipe and
exchanger losses, minimize/eliminate use of valves and select Minimum Needed
Flow under ALL operating conditions. This may call for variable flow systems in
many cases to suit operation or to SAVE energy. Changing flow will need retuning
the system for optimization.
Figure below shows a system with an unthrottled flow of 12000 lpm and a variation
upto 6000 lpm. The pump efficiency figures are shown on the head-flow curve. The
best efficiency of 85% is at 12000 lpm which is lowered to 69% at 6000 lpm. Static
head is 10 metres. The throttled operation parameter are shown in the Table below.
Q1 / Q2 = N1 / N2
Head: Head is proportional to the square of speed
Incorporating efficient pump and method of flow capacity control at the design
stage or as a retrofit by using variable speed, trimming of impellers, variable pitch
designs (axial flow), changing impellers and change of pumps along with minimal
flow concept and better (bigger) heat exchangers, summarises the total concept of
energy saving measures.
98
99
12000
23.50
23.20
86.00
53.58
97.41
90.00
59.53
99.80
59.65
9000
17.93
27.50
79.50
50.87
92.49
89.60
56.77
99.80
56.88
6000
13.35
29.50
69.00
41.92
76.20
89.00
47.10
99.80
47.20
Original Data
After Modification
Flow
Dia
Cons.
Head
Flow
Dia
Cons.
Head
Saving
M3/hr
Mm
kW
M3/hr
Mm
kW
kW
Condensate
150
321
159
220
150
291
130
180
29
Hot Condensate
150
346
83
175
150
320
70.2
150
12.8
82.1
258
57
155.3
82.1
202
35
146
22
60.2
250
45
158
60.2
203
27
95
18
102
280
63
158
102
NA
38
95
20.2
D.M. Transfer
125
306
60
128
125
294
55.4
118
20.5
350
125
102.6
186
320
104.5
86
20.5
350
125
102.6
186
320
104.5
86
20.5
186
Additionally
1.
2.
Energy Saving
The same system was equipped with an inverter with 97.5%, efficiency changing to
89.5% at reduced load (See Table below).
Case study 25 :
Brief
Flow lpm
System / Pump Pressure (m)
Pump Efficiecny (%)
Pump Input (KW)
Motor RPM
Motor Load % F.L.
Motor Efficiency (%)
Motor Input (kW)
Controller Efficiency %
Input (kW)
Savings Inputs (kW)
% Saving (Throttled - Input)
12000
23.50
86.00
53.58
1450
97.40
93.70
57.18
97
58.95
0.70
1.12
9000
17.93
85.50
31.02
1210
56.40
93.60
33.14
94
35.25
21.63
38.03
6000
13.35
78.00
16.78
1000
30.50
90.00
18.64
89.50
20.83
26.37
55.80
100
In one of the Jal Board boosting stations, there were 6 nos pumps-3 of 125 HP and
other 3 of 100 HP pumps. While the 125 HP pumps were giving their efficiency near
to the rated efficiency of 58 %, the 100 HP pumps were giving efficiency in the range
of 13% to 19 %. The efficiency had gone down as these were run in parallel with 125
HPpumps, which were having different characteristics. Further, the head
generated by these pumps was much higher than required as the flow was being
throttled.
Energy Saving
Replacement of 100 HP pump by energy efficient pump with VFD
Energy saving
Annual saving
Investment
Payback period
101
:
:
:
:
Case study No. 26 : Use of one high capacity pump in place of 4 nos of small
capacity chilled water pumps
Brief
No. of Pumps in parallel
Capacity of pumps
Valve throttled
New pumps (1 no.)
: 4 (20 HP each)
: 20.5 lps, 43.75m
: 60%-80%
: 50 HP
Instead of 4 nos. of Pumps, one big pump of 50 HP motor and energy efficient pump
was installed. Savings effected were as follows:
Energy Saving
Annual energy saving
Annual cost saving
Investment in modification
Simple payback
3.4.2
Fig. 3.6 shows a fan performance curve for flow reduction from 0.66 per unit to
0.50 per unit. The system head characteristic does not have static head in the case of
blowers and fans. The system resistance consists of dampers, ducts with bends etc.
and diffusers or such other equipments. The system curve follows the expression
KQ2 which is a parabola starting from origin.
3.
4.
5.
6.
7.
8.
Fan Name
% of Flow
Cooler fan A
Cooler fan B
Cooler fan C
Air fan
Reverse fan
Mill fan
Cement fan
ESP fan
89.78
127.36
86.74
119.32
99.65
35.03
19.41
30.99
% of Static
Pressure
55.65
45.84
59.09
27.99
27.00
39.08
13.43
13.54
Static
Efficiency
55.00
65.10
58.84
36 .88
16.93
18.70
4.19
9.97
Energy Saving
Calculation for kVA Savings by Changing the Fan Motor (OnlyCooler Fan-1 is
taken for example)
Parameter
Power consumption
(kW)
Power factor
Annual saving (Rs.)
Before
Implementation
108
After
Implementation
78
Saving/
Improvement
( - ) 30
0.80
-
0.85
-
( + ) 0.05
( + ) 4,92,480
By outlet damper - Reduces energy use but relatively large damper loss.
By inlet damper - Reduced suction reduces effective density to give reduced
head/flow. Better compared to outlet damper.
102
* The impeller power for the new fan is calculated by taking 10% margin in present
flow. 15% margin in present static pressure and 90% fan efficiency for cooler than
(for other fans - 75% fan efficiency)
Total energy saving for all the fans in above table (kWh/t clinker) : 1.037
Annual saving
: Rs.2.2 Million
Investment
: Rs.2.4 Million
Payback period
: 13 months
103
Case Study 28: Speed Reduction of Vacuum Blowers and Agitators in Pulp &
Paper Industry
Brief
(a) Some of the vacuum blowers of PM 1 were being operated with dampers closed
to a greater degree. The blowers are belt driven. The pulley sizes are changed
to reduce the speed of the fans.
(b) Speed reduction was carried out on new bleached high density tower agitator.
(c) The plant personnel decided to operate the blower at 2100 rpm and keep the
damper fully open. After implementation, the power consumption was
measured to be 17.4 kW.
Energy Saving
(a) Annual Saving
Investment
Payback period
: Rs.93000
: Rs.15000
: 2 months
:
:
:
:
:
Energy saving
Average running kW of ID fan with VFC
Average running kW of ID fan with VFD
Energy saved/day (42 x 24 hours)
Annual saving
Investment
Payback period
:
:
:
:
:
:
55 kW
13 kW
1008 kWh
Rs. 0.647 Million
Rs. 1.2 Million
2 years
Case Study 31: Installation of Variable Frequency Drive for Control of ID Fans
in place of Inlet Damper Control in Pulp & Paper Industry
Brief
50 tph AFBC boiler was provided with 2 nos. ID fans. The furnace draft was being
controlled by varying the inlet damper position of ID fans. Each ID fan is driven by
90 kW motor, 750 rpm. The normal damper opening when boiler was at full load
awas 55%. It was decided to install 2 nos. 90 kW VFDs for fan control.
Energy Saving
16 kWh
96000 kWh
Rs. 0.48 Million
Nil
Immediate
:
:
:
:
:
84 kW (each motor)
58 kW (each motor)
Rs. 0.75 Million
Rs. 1.1 Million
18 months
Brief
Brief
Industry
Application
Motor Rating
:
:
:
Previous System
Problem Observed
Present System
There are 7 nos. of 3000 cfm (6" head) blower for machine exhaust. It is suggested
to inter-connect the blower with damper so that minimum number of blowers can be
run common to all machines and can also be run independently if required.
Energy Saving
Annual saving
Investment
Payback period
: Rs. 1,62,940
: Rs. 25000
: 2 months
Paper
Pump (Water Suction)
3 Phase AC Induction Motor
Rating : 130 HP - Volt : 415 V
Current : 160 A - RPM : 1440
Motor was run through Star-Delta Starter
104
Previous System
Present System
105
Freq
(Hz)
50
25 to 40
Amp.
kW
100
40 to 50
60
40
Water m3 / hr.
130
130
Drain Valve
50 to 70 open
100% (Average)
Energy Saving
Actual capacity of 100 kW motor
Actual requirement for process
Without drive power consumption
With AC Drive power consumption
Energy Saving
Annual Saving
Investment
Payback period
Option (a)
:
:
:
:
:
:
:
:
500 m3/hr
130 m3/hr
60 kW
40 kW
480 kWh/day
Rs 0.65 Million
Rs 0.325 Million
5 months
a)
Impeller trimming
= 90 x 1.2
= 108 m3/hr
Pressure developed across fan, H2
= 80-(65-20)
= 35 mm WC
New fan static efficiency
= 68 -5
= 63%
For flow Q1 = 90 m3/s, H1 =?, Q2 = 108 m3/s and H2= 35 mm WC
(Q2/ Q1)2 = (H2/H1)
(108/90)2 = (35/H1)
H1 = (90/108)2 x35
= 24 mm )
Power developed at fan shaft
= 90 x 24
102 x 0.63
= 33.61 kW
New impeller diameter (D2)
Considering the fan law
(D1 / D2) = (Q1/Q2) = (N1/N2)
D1 = 70 mm, Q1=108, Q2 = 90, D2 = 58 mm, N1= 850 RPM
New impeller diameter, D2
= 58 mm
New RPM
= 90/108 x 850
= 708 RPM
Option (b)
For option (a), if original impeller size were 70 mm in diameter, what would be
the new impeller diameter if efficiency drops by 5%?
For option (b), what would be the required reduction in RPM if fan was
originally running at 850 RPM and efficiency at reduced RPM is expected to
be 66%?
We finally find out the differential energy savings between the two options at
8760 hours/annum and at Rs.4 / unit.
Motor power drawn
Power input at fan shaft (BHP)
= 120 kW
= 120 x 0.86
= 103.2 kW
Flow, Q1
= 90 m3/s
Pressure developed across fan, H1 = 80 mm
Original impeller diameter (D1) = 70 mm
Original RPM
= 850 RPM
Fan static efficiency
= Flow x Pressure developed across fan x100
102 x Power developed at fan shaft
= 90 x 80 x 100
102 x 103.2
= 68 %
106
= 66%
= 90 x 24
102 x 0.66
= 32.08 kW
= 1.53 / 0.86 x 8760 hours/annum x Rs.4 / kWh
= Rs. 62340
B) A centrifugal pump pumping water operates at 35 m3/hr and at 1440 RPM. The
pump operating efficiency is 68% and motor efficiency is 90%. The discharge
pressure gauge shows 4.4 kg/cm2. The suction is 2m below the pump
centerline. If the speed of the pump is reduced by 50 % estimate the new flow,
head and power
Flow
= 35 m3/hr
Head developed by the pump = 44 - (-2) = 46 m
Hydraulic Power = Q (m3/s) x Total head, hd - hs (m) x (kg/m3) x g (m2/s)/1000
Power drawn by the motor = (35/3600) x 46 x 1000 x 9.81
1000 x 0.68 x 0.9 (i.e. efficiency of pump & motor)
= 7.2 kW
Flow at 50 % speed Q2
:
35 / Q2 = 1440/720
Q2
= 17.5 m3/hr
Head at 50 % speed H2
:
46 / H2 = (1440/720)2
H2
= 11.5 m
Power at 50 % speed P2 :
7.2/kW2 = 14403 / 7203
P2
= 0.9 kW
107
Power kW
COP
Vapour compression machines are used extensively for refrigeration. This system
requires motive power to drive a compressor, which is supplied by an electric motor
or engine.
With increasing electricity prices, there is renewed interest in Absorption
Refrigeration machines, wherein heat is used for cooling. Users having waste heat
or economical heat energy sources are using the absorption chillers.
10.78
6.62
5.75
19.7
0.61
32.20
21.38
5.32
18.2
0.66
48.30
32.06
5.32
18.2
0.66
64.40
42.75
5.32
18.2
0.66
7.00
4.62
15.8
0.76
13.90
12.10
4.03
13.8
0.87
42.00
34.50
4.28
14.6
0.82
6.00
20.5
0.59
2.9 to 2.3
7.8 to 10
1.2 to 1.5
329.94
1.8 to 2.3
Note : The above data is based only on the compressor power consumption,
auxiliary power for pumps, fans etc. is excluded.
= 3023 kcal/hr
= 3.51 kWthermal
= 12000 Btu/hr
The commonly used figures of merit for comparison of refrigeration systems are
Coefficient of Performance (COP), Energy Efficiency Ratio (EER) and Specific
Power Consumption (kW/TR). The definition of these terms are given below.
If both refrigeration effect and the work done by the compressor (or the input
power) are taken in the same units (TR or kcal/hr or kW or Btu/hr), the ratio is
COP = Refrigeration Effect
Work done
If the refrigeration effect is quantified in Btu/hr and the work done is in Watts, the
ratio is
EER
1.5
108
Table 3.10 : COP, EER & Specific Power for Vapour absorption Systems (for
chilled water at 8oC with water cooled condensers)
Capacity TR
COP
EER
Btu/hr/W
Specific
steam cons.
Kg/hr/TR
0.61
2.10
8.75
1.10
1.13
1.13
1.17
3.76
3.86
3.86
4.00
4.90
4.75
4.76
4.59
0.96
3.28
0.96
3.27
0.35
m3/hr/TR
0.36
lit/hr/TR
Comments :
(b)
a)
The approximate thumb rule is that for every 1oC higher temperature in the
evaporator, the specific power consumption will decrease by about 2% to 3%.
(c )
b) Centrifugal compressors, which are generally used for cooling loads about 150
TR, can have COP of about 6, EER greater than 20 and Specific Power
Consumption of 0.59 kW/TR.
When the refrigeration system's cooling capacity is significantly more than the
actual cooling load, expansion valve control based on superheat sensing often leads
to supercooling, resulting in an energy penalty due to unnecessarily lower
temperature and also lower COP at lower temperatures.
c)
(e)
-5
Condens er Temperature o C
Capacity
+35
151
94
+40
143
102.7
+45
135
110.6
+50
127
117.8
Sp.Power (kW/TR)
0.62
0.72
0.82
0.93
Capacity (TR)
129
118
111
104
90
96.8
103
108.9
Sp.Power (kW/TR)
Capacity (TR)
Power cons. (kW)
0.70
103
84.2
0.82
96
89.6
0.93
90
94.7
1.05
84
99.4
Sp.Power (kW/TR)
0.82
0.93
1.05
1.19
110
Capacity (TR)
Power cons. (kW)
(g) Use Evaporators and Condensers with Higher Heat Transfer Efficacy
111
Brief
Before
Implmentation
39.9
10
323
After
Implementation
32.3
6.7
267
Saving /
Improvement
7.6
3.3
56
Brief
:
:
:
:
18371 kWh
Rs. 82670
Rs. 0.12 Million
1.5 years
1. Shutting down the compressor, keeping the fan running and allowing
the space heat to melt the frost.
2. Using out side warm air to melt the frost after isolating the coil from
the cold room.
3. Using electric resistance heaters in thermal contact with the coil.
4. Bypass the condenser and let the hot gas into the evaporator to melt
the frost.
5. Spray water on the coils to melt the frost.
Match the Refrigeration System Capacity to the Actual Requirement
Monitor Performance of Refrigeration Machines
Energy Saving
Annual savings
Annual savings
Investment
Payback period
112
The chilled water system had primary (chiller side) and secondary (process side)
pumps with a hot well and cold well arrangement. Since the chilled water
requirement for the plant was reasonably steady, it was decided to eliminate the
primary pump and connect the warm chilled water from the secondary side directly
to the chiller, bypassing the hot well. In view of the increased pressure requirement,
a new, efficient pump of appropriate head requirement was recommended. The
power consumption scenario before and after this change is as follows:
Energy Saving
Parameter
Operating hrs. of primary pump
(hrs.)
Energy consumption (kWh/day)
Operating hrs. of secondary
pump (hrs.)
Energy consumption (kWh/day)
Total power consumption
(kWh/day)
Before
Implementation
10
After
Implementation
NIL
Saving /
Improvement
-
85
24
NIL
24
271
356
139
139
132
217
During the study the pressures, temperatures & water flow in the cooling water
circuit were measured. It was observed that there was a high discharge pressure
and low suction pressure due to heavy scaling in condenser.
Consequent upon study, the condensers were replaced. Valves were replaced with
butterfly valves and cooling coils were cleaned. Filters of AHU units were also
replaced.
Energy Saving
Annual energy saving
Annual Saving
Investment
Payback period
:
:
:
:
21275 kWh
Rs. 75,000
Rs. 0.16 Million
2 years
Case study 36 : Savings due to stopping bypass through idle pumps and idle
condensers.
Brief
In an automobile plant, condenser water was flowing through the idle pumps and
the idle condensers resulting in loss of head as the valves had broken down and
were passing. By stopping by-pass though idle pumps and idle condensers the
energy savings was as follows :
Energy Saving
Annual Energy Saving
Annual Saving
Investment
Payback
3.5.3
:
:
:
:
2760 kVAh
Rs.979800
Nil
Immediate
Brief
The cooling tower specification is given below:
Cooling Towers
In many plants, after the cooling tower has been in service for a few years, the need
for improving its performance is felt. This may be due to:
a) Deterioration of efficiency of the cooling tower,
b) Deterioration in the efficiency of the heat exchangers (coolers, condensers
etc.) at the end-use side,
c) Additional heat rejection due addition of equipment, plant capacity etc.
Two parameters, which are useful for determining the performance of cooling
towers, are the Temperature Range and Temperature Approach.
Sl.
No.
1.
Location
Cooling Plant
Cooling tower
Specification
Capacity
200 TR
Actual
Power kW
11.5
5.93
Replace the aluminum blades by new energy efficient FRP blades. By using FRP
blades there will be a minimum saving of 10% in the energy.
Savings obtained by conversion of aluminium blades to FRP blades.
Energy Saving
115
Install automatic temperature controller for cooling towers (28-30 C). The
controller switches off the fan when the cold well temperature goes below the set
temperature and switches on when temperature goes above the set temperature (2830 0C).
Energy Saving
Parameter
Annual Power
Consupmtion (kWh)
Before
Implementation
114423
After Implementation
80096
Annual Saving
Investment
Payback period
3.6
Saving/
Improvement %
30%
: Rs.137300
: Rs.50000
: 5 months
Losses in Transformers
Transformer losses consist of two parts: No-load loss and Load loss
1. No-load loss (also called core/iron loss) is the power consumed to sustain the
magnetic field in the transformer's steel core. Core loss occurs whenever the
transformer is energized; core loss does not vary with load. Core losses are
caused by two factors: hysteresis and eddy current losses. Hysteresis loss is
that energy lost by reversing the magnetic field in the core as the magnetizing
AC rises and falls and reverses direction. Eddy current loss is a result of
induced currents circulating in the core.
2. Load loss (also called copper loss) is associated with full-load current flow in
the transformer windings. Copper loss is power lost in the primary and
secondary windings of a transformer due to the ohmic resistance of the
windings. Copper loss varies with the square of the load current. (P = IR)
For a given transformer, the manufacturer can supply values for no-load loss, PNOLOAD, and load loss, PLOAD. The total transformer loss, PTOTAL, At any load level can
then be calculated from:
PTOTAL = PNO-LOAD + (%Load/100) x PLOAD
Where transformer loading is known, the actual transformers loss at given load can
be computed as:
2
kVA Load
= No load loss + Rated kVA x (full load loss)
116
117
Energy saving
[( pf1 ) - 1 ]
2
: 1000 kWh
: Rs.10000
: Nil
: Immediate
Thus, if p.f. is 0.8 and it is improved to unity, the saving will be 56.25% .
Case study 40 : Reallocation of the load of transformer
Brief
Table 3.12 summarises the variation in losses and efficiency for a 1000 kVA
transformer and also shows the difference in losses by using a 1600 kVA
transformer for the same. The 1000 kVA transformer has a no load loss of 1700
watts and load loss of 10500 Watts at 100% load. The corresponding figures for
1600 kVA transformer are 2600 Watts and 17000 Watts respectively. Loading is by
linear loads. Temparatures assumed equal.
Presently there are 3 numbers of transformers in a plant. From the data given it can
be seen that Transformer No.3 i.e. 1250 kVA transformer is loaded only 28.70% i.e.
359 kVA against 1250 kVA. It is recommended to shift the load to a lower capacity
transformer of 750 kVA which is lying idle.
Transformer
TRANSFORMER-2
1600 kVA. No load
losses = 2600 W
Difference
in losses,
W
1
2
3
4
Rated
kVA
2000
2000
1250
750
Voltage
Current
Loading kVA
440
440
440
440
1200
1280
471
-
914.94
953.29
358.87
-
Loading
%
45.72
47.66
28.70
Idle
Load
Load
losses
Total
losses
Output
kW
Efficiency
%
Load
losses, W
Total
losses,
W
0.1
105
1805
100
98.23
60
2660
861
0.2
420
2120
200
98.9 5
265
2865
745
0.4
1680
3380
400
99.16
1062
3662
282
0.6
3780
5480
600
99.09
2390
4990
-490
0.8
6720
8420
800
98.96
4250
6850
-1570
1.0
10500
12200
1000
98.18
6640
9240
-2960
Calculations
The efficiency of 1000 kVA transformer is maximum at about 40% load. Using a
1600 kVA transformer causes under loading for 1000 kW load. The last column
show the extra power loss due to oversized transformer. As expected, at light loads,
there is extra loss due to dominance of no load losses. Beyond 50% load, there is
saving which is 2.96 kW at 1000 kW load.
The saving by using a 1600 kVA transformer in place of a 1000 kVA transformer at
1000 kW load for 8760 hours/annum is 25930 kWh/year @ Rs .5.0/kWh, this is
worth Rs 0.129 Million. The extra first cost would be around Rs 1.5 Million. Hence
deliberate oversizing is not economically viable.
3.6.2.3 Reduction of losses due to improvement of power factor
Transformer load losses vary as square of current. Industrial power factor vary
from 0.6 to 0.8. Thus the loads tend to draw 60% to 25% excess current due to poor
power factor. For the same kW load, current drawn is proporational to kW/pf. If
p.f. is improved to unity at load end or transformer secondary, the saving in load
losses is as under.
118
Transformer Loading:
= 358.87 kVA
= 1250 kVA
= 28.70%
= 750 kVA
= (0.2870)2 x 6 x 24 x 330
= 3914 kWh
= 0.59 kW
(where 6 kW = full load copper loss of existing 1250 kVA transformer-considering
330 days 24 hrs operation in a year)
Iron loss for 1250 kVA transformer
= 2.5 x 24 x 365 = 21900 kW
(Where 2.5 kW = iron loss for1250 kVA transformer)
Total loss for 1250 kVA transformer
On replacement of 1250 kVA transformer with 750 kVA transformer, the average
loading of 750 kVA transformer will be
= 359 = 47.85%
750
Copper loss for 750 kVA transformer
=(0.4785)2 x 4 x 330 x 24
= 7255 kWh
(where 4 kW = full load copper loss of 750 kVA transformer-considering operating
hours 24 for 330 days)
Iron loss for 750 kVA transformer
= 1.95 x 365 x 24
= 17082 kWh
(where 1.95 kW = iron loss for 750 kVA transformer)
Total losses for 750 kVA transformer
119
= 7255 + 17082
= 24337 kWh
Monetary saving
Investement
Payback period
Energy Saving
Savings in kWh
Annual Savings @ Rs.4.20 per kWh
Case study 41:
= 25814 24337
= 1477 kWh
=1477 x 4.20
= Rs. 6203
Brief
3.7
Power is received from the electricity board and 3 nos. of 10000 kVA, 33kV/ 433
volts transformer are installed for stepping it down to 433 volts for plants
distribution. Each transformer feeds its own P.C.C. and facility is available to run
the transformer in parallel.
Now the transformers are run independently and the loads in them are not
balanced. The load on the T.R. 2 and 3, which were in service, was monitored for 24
hrs.
These transformers have their maximum efficiency at 25 to 50% of loading. As per
monitoring, transformer 3 is loaded around 50% and transformer 2 is loaded at
less than 25% of their respective rated capacities both operating outside their
maximum efficiency ranges.
These transformers were run in parallel.
Energy Saving
:
:
:
:
:
:
:
:
:
: Rs.52,000
: Nil
: Immediate
75.2 kW
64.5 kW
4035 kWh
Rs.14,204
24. x 365 hrs
66% - 77%
15% - 20%
Nil
Immediate
20
50
70
100
150
200
300
450
1500
3000
Additional localised
lighting for visually
exacting tasks
One transformer is dedicated to one separate annexe building, the other 4 nos are
connected in the configuration of 2 each on east and west wing of the buildings.
Switching off one transformer each on west and east wing load during weekly off
days and transferring the load on the other transformers in line shall save the the
no-load losses of the transformer & the maximum efficiceny of the other 2
transformers can be attained by loading at 40-50 % load.
Energy Saving
: 2kW
: 13,000 kWh
120
The utility of using natural day lighting instead of electric lighting during the day is
well known, but is being increasingly ignored especially in modern air121
Color
Lamp
Rendering Life(hrs)
Index
8 to 17
100
1000
Tungsten Halogen
(Single ended)
75,100,150,500,1000,2000
(no ballast)
13 to 25
100
2000
Tungsten Halogen
(Double ended)
200,300,500,750,1000,1500,
2000 (no ballast)
16 to 23
100
2000
20,40,65
(32,51,79)
31 to 58
67 to 77
5000
18,36,58
(29,46,70)
38 to 64
67 to 77
5000
Compact Fluorescent
Lamps
(CFLs) (without
prismatic envelope)
Compact Fluorescent
Lamps
(CFLs) (with
prismatic envelope)
5, 7, 9,11,18,24,36
(8,12,13,15,28,32,45)
26 to 64
85
8000
9,13,18,25
(9,13,18,25)
i.e. rating is inclusive of
ballast consumption
48 to 50
85
8000
160 (internal
ballast, rating is
inclusive of
ballast
consumption)
18
50
5000
38 to 53
45
5000
80,125,250,400,1000,2000
(93,137,271,424,1040,2085
)
250,400,1000,2000
(268,427,1040,2105)
51 to 79
70
8000
70,150,250
(81,170,276)
62 to 72
70
8000
70,150,250,400,1000
(81,170,276,431,1060)
69 to 108
25 to 60
>12000
35,55,135
(48,68,159)
90 to 133
122
Efficacy
(including
ballast losses,
where
applicable)
Lumens/Watt
123
--
>12000
Table- 3.15 Summarises the replacement possibilities with the potential savings.
Table 3.15: Savings by Use of More Efficient Lamps
Lamp type
Power saving
Sector
Existing
Domestic/Commercial
Industry
Industry/Commercial
GLS
GLS
GLS
TL
HPMV
HPMV
Replace by
100 W
*CFL
25 W
13 W
*CFL
9W
200 W Blended 160 W
40 W
TLD
36 W
250 W HPSV 150 W
400 W HPSV 250 W
Watts
75
4
40
4
100
150
75
31
20
10
37
35
Energy Saving
Annual saving
Investment
Payback period
High pressure mercury vapour lamp of 250W & 400W capacity, halogen lamp of
500 W were used for street lighting in a manufacturing plant. 250W and 400W High
pressure mercury vapour lamp used for street lighting could be replaced with 70W
& 150W High pressure sodium vapour lamp respectively. 500W Halogen lamps
used for street lighting and outside the factory could be replaced with 70W Highpressure sodium vapour lamp.
: Rs.97,700/: Rs.20,000
: 3 months
Brief
The lighting conversion efficiency of the incandescent lamp is 13.8 lumens per watt
which is very low. Blended mercury vapor lamps of 160 W installed had much
higher luminous intensity than required. Blended lamps were very inefficient and
the lighting conversion efficiency was only 18 lumens per watt. Replaced
incandescent and blended type mercury vapor lamps with CFL.
Energy Saving
Annual energy saving
Investment
Payback period
Brief
In a refractory manufacturing unit, there were 150 nos of 10 W filament type lamps
for indication purpose. These used to be glowing for 24 hrs for all the days of the
year. It was consuming 1.2 kW. The total energy consumed was 10512 units on
yearly basis. During the energy audit, it was decided that these can be replaced by
LED type lamps consuming only 1 w power. After replacement by 10 nos of 1 W
LED lamps, the total consumption became of 1051 units per year. The saving
annually was observed of 9461 units, resulting in monetary saving of Rs 0.43 lakh
per year (Rate of Rs 4.50 per unit).
Energy Saving
Annual Saving
Investment
Payback period
: Rs.21,500
: Rs.20000
: 11 months
124
125
Decreases by 9 %
Decreases by 15 %
Increases by 8 %
Increases by 8 %
Decreases by 20 %
Decreases by 16 %
Increases by 20 %
Increases by 17 %
Decreases by 24 %
Decreases by 20 %
Increases by 30 %
Increases by 20 %
Decreases by 30 %
Decreases by 20 %
Increases by 30 %
Increases by 20 %
Decreases by 28 %
Decreases by 20 %
Increases by 30 %
Increases by 26 %
Decreases by 4 %
Decreases by 8 %
Decreases by 2 %
Increases by 3 %
: 4
: 338 kW
After installation
Total Power consumption
Annual Total energy savings
Annual Cost savings
Cost of Implementation
Simple payback period
: 275 kW
: 0.245 Million kWh
: Rs. 0.49 Million
: Rs. 1.24 Million
: 2 .5 years
126
127
:
:
:
:
Type of Lamp
With Conventional
Electromagnetic Ballast
With Electronic
Ballast
Power Savings,
Watts
53
81
42
11
75
40 W Tubelight
70 W HPSV
Electronic ballasts have also been developed for 20W and 65W fluorescent tube
lights, 9W & 11W CFLs, 35W LPSV lamps and 70W HPSV lamps. These are now
commercially available.
Use a lighting control panel with time clock and photocell to control exterior
lighting to turn on at dusk and off at dawn and turn non-security lighting off
earlier in the evening for energy savings.
Case study
Brief
No. of electronic blasts
Hours/annum operation
Brief
: 24000
: 2400
Energy Saving
Annual Energy Saving through electronic ballast
Annual additional saving due to
reduced heat load on air-conditiong (kWh)
Total annual energy saving
Annual saving
Investment
Payback period
: 8,83,200 kWh
: 1,39,100
:
:
:
:
10,22,300 kWh
Rs 6.29 Million
Rs 3.6 Million
7 months
The lighting in the plant was mainly provided by fluorescent lamps. The shop areas
were provided with north light in the roof which provided good lighting in the shop
floor during day time when sky was clear. Apart from this, the machines were also
provided with work lights. In spite of all these provisions the shop artificial lights
were always switched on.
Segregated lighting and fan circuits provided distribution boards exclusively for
lighting. Installed photo electric switches to switch off light in identified areas.
Energy Saving
Annual Energy saving
Annual saving
Investment
Payback period
:
:
:
:
43,800 kWh
Rs.1,57,000/Rs.80,000/6 months
Brief
Automatic control for switching off unnecessary lights can lead to good energy
savings. Simple timers or programmable timers can be used for this purpose.
The process area of the plant was provided with enough lighting by means of
Fluorescent Lamps. Fluorescent lamps were ON throughout the day. It was
observed that translucent sheets were not provided in the roof.
The timings may have to change, once in about two months, depending upon the
season. Use of timers is a very reliable method of control.
128
129
Installed Day Light Switches to switch off lamps and provided translucent sheets in
the roof to get natural light in daytime.
Energy Saving
Annual Energy Saving
Annual Saving
Investment
Payback period
Energy Saving
Annual Energy Saving
Annual saving
Investment
Payback Period
Case Study 53:
:
:
:
:
2,74,176 kWh
Rs.11,67,990
Rs.68000/1 months
Brief
Conventionally, streetlight planning in a Municipal Corporation was not
systematic - it was normally quantity based and not lighting design based.
Photometric & Installation terms were totally ignored and the Selection criteria
for Lamps & Luminaires ignored.
The corporation realized the need for uniform & required level of illumination
with increased energy efficiency. As a part of this innovation, they decided to
develop street lighting on new roads in a scientific and systematic manner by
implementing "Code of practice for lighting of Public thoroughfares IS 1944
(Part I & II), 1970".
During different seasons street light ON / OFF timings are changed.
The ON time varies from 6:00 pm during winters to 7:45 pm during summers.
The OFF time varies from 7:15 am during winters to 5:30 am during summers.
It is necessary to fix ON / OFF timings for the entire year according to sunset
and sunrise timings.
Before
Implementation
8.5 to 10
7 to 8
30
1.5 to 3
15
250
33
66
7,57,100
74,500
Less than10 Lux
After
Implementation
8.5 to 10
10
42
0.9 to 1.25
5o-10 o
250
22 (33% reduction)
44
5,90,000 (22%
saving)
50,100
(32.75%
saving)
30 Lux with 40%
uniformity
130
24400 kWh
Rs.167100
Rs. 240 Million for 21 major roads
54 months
:
:
:
:
:
:
:
:
:
:
:
48 W
29 W
19 W
0.13 Million kWh
Rs 0.6 Million
Rs. 1.2 Million
2 years
Clean fixtures, lamps and lenses every 6 to 24 months by wiping off the dust.
Replace lenses if they appear yellow.
Clean or repaint small rooms every year and larger rooms every 2 to 3
years.
Consider group re-lamping.
131
3.8
Energy saving can be achieved in homes and our day-to-day life by adopting the
following simple measures.
3.8.2
3.8.1
Electricity
Capacity
3000 Watt
1000 Watt
1500 2500 Watt
170 Watt
60 Watt
200/300/500 Watt
1000 2000 Watt
1000 1500 Watt
1000 Watt
800 Watt
750 Watt
100/ 60/ 40 Watt
40/ 20 Watt
36 Watt
7/ 9/ 11/ 13 Watt
180 Watt
800 Watt
120 Watt
Consumption
3 units/ hour
1 unit/ hour
8.5 14.5 units/ day
1.7 units/ day
0.6 unit/ day
2/3/5 unit/ day
1 2 units/ hour
1 1.5 units/ hour
1 unit/ hour
0.8 unit/ hour
0.65 0.75 unit/ hour
0.5/ 0.3/ 0.2 unit/ day
0.28/ 0.15 unit /day
0.26 unit/day
0.06-0.09 unit/ day
0.2 unit/ hour
0.8 unit/ hour
0.13 unit/ hour
Air conditioner
Electric Water heater
Refrigerator
Washing machine
Television
Incandescent lamp
Computer
3.8.3
Rational use of energy does not mean that we sacrifice the need for comfortable
existence. Rational use of energy strictly means to use the available energy more
efficiently and avoid wastage of energy when a particular appliance is not in use.
Energy saving potential in a typical house is 20%-25%. If the electricity bill is Rs.
2000/- p.m., one saves about Rs. 400/- p.m. by proper use of electrical appliances.
132
Washing Machine
Using the machine at full load, the water consumption remains the same
irrespective of load of clothes.
Switch on the washing machine after loading.
Put off the machine from the main switch after use.
Same about 15%-20% of power by setting thermostat to 500C.
3.8.7
Refrigerator
Use stabilizer with refrigerator & set the voltage to 220 volt.
Check the gaskit to avoid ingress of heat from outside.
Avoid frequent opening of refrigerator door.
Do not place the refrigerator in kitchen or congested area.
Regular defrosting to avoid ice accumulation in the freezer.
Cool the food before putting it in the refrigerator.
Purchase 'Star' rated Energy Efficient Refrigerators only.
3.8.6
3.8.5
Air-conditioner
Use stabilizer with air conditioner & act the voltage to 220 V.
Clean the filters, condenser coils and thermostat at regular intervals.
Avoid frequent opening of doors and windows.
Avoid direct sunlight in the air conditioned space.
Installation of reed screens in air-conditioners.
Save Re. 1/- per hour by setting the room temperature to 250C.
Purchase 'Star' rated energy efficient Air Conditioners only.
3.8.4
Television
Switch off the TV from the main switch and not through remote control.
Don't leave TV on stand-by mode as it consumes around 80 watts of power
even when not being viewed.
133
3.8.8 Computers
D. Air Conditioning
System:
1. Effectiveness of
existing Units is
only 64% and
8,10,000 kWh
specific power
consumption is high
2. Cooling water
and chilled
1,20,000 kWh
water is flowing
in idle Units.
3.9
Case Study 55 : Energy Audit of a Bank's Head Quarter building in New Delhi
Brief
Energy Savings
Sl Equipment /
No. Observation
Reason
Expected
Investment
(Rs in Lakh)
Payback
Period
Action Required
Power Factor is
poor and is
sometimes leading
B. DG Set:
1. Specific Power
Generation of DG
sets very low.
C. Illumination:
1.
2.
Use of energy
efficient lights
Use of 28 W, T5
tube lights
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
A. Load Management:
1.
5.88
Nil
References
Punjab National Bank- with its beginning in April, 1895 at Lahore- is at present one
of the foremost banks in India with a network of 4500 offices, serving more than 3.7
crore customers and having a business turn over exceeding Rs 1,94,000 crores. The
focus areas during the Energy Audit were:
1.1
1.2
1.3
1.4
1.5
-Install Screw
Chillers of
39.69 75.00 23 months total 600 TR
capacity
4,23,420 kVAh
12 kL of HSD
11,497 kWh
2,26,000 kWh
20.75
3.96
0.56
11.07
4.00
Minimal
0.14
16.00
18 months
Replacing existing
2000 nos. of tube lights
with 28 W T/L having
electronic chokes.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
134
135
29. 'Pump Hand Book'-I.J. Karassik, WC Krutzsch, W.H. Fraser, J.P. Messina,
McGraw Hill International.
30. 'Analysis of Water Distribution Systems'- T.M. Walski CBS Publishers, Delhi.
31. Refrigeration and Air Conditioning' - W.F. Stoecker and J.W. Jones - Tata
McGraw Hill.
32. 'Technology Menu for Efficient Energy Use'-National Productivity Council,
India and Centre for Energy and Enviornmental- Studies of Princetonne
University.
33. 'Good Practice Guide No. 2' - Energy Efficiency Office, Deptt. of Energy, U.K.
34. 'Energy Saving, with Adjustable Frequency Drive'- Allen Bradley Publication.
35. Saving Electricity in Utiltiy Systems of Industrial Plants, Devki Energy
Consultacny Pvt. Ltd., Vadodara.
36. Industrial Refrigeration Handbook, Wilber F. Stoeker, McGraw Hill .
37. Refrigeration and Air conditioning, M. Prasad, New Age International (P) Ltd.
38. ASHRAE Handbooks, ASHRAE, Atlanta, Georgia, USA.
39. Cooling Tower Technology- Maintenance, Upgrading and Rebuilding, Robert
Burger, The Fairmont Press Inc., Georgia, USA
40. Low-E Glazing Design Guide, Timothy E. Johnson, Butterworth Architecture.
41. Best Practice Manual - Electric Motors Transformers, Lighting : MEDA.
42. Energy Efficient Technologies for Industries, LBNL ,USA.
43. Bureau of Energy Efficiency-Course Material for Energy Manager/Auditor.
44. Websites/Product Information CDs of the following manufacturers:
1. www.energymanagertraining.com
2. Cromptonne Greaves Lighting Division
3. Bajaj Electricals
4. GE lighting, USA
5. Watt Stopper Inc, USA
6. Vergola India Ltd
7. Lighting reasearch centre, USA
Section 3
Energy Conservation
in the
Hydrocarbon sector
Chapter - 4
Chapter - 5
Chapter - 6
Chapter - 7
136
Refining Sector
Exploration & Production
LPG Bottling Plants
Marketing Terminals/ Depots