TRAINING FEED BACK ON SAVING ELECTRICITY IN INDUSTRIAL PLANTS &

COMMERCIAL BUILDINGS

BY:D.N.JAKASANIABY:D.N.JAKASANIA

ORGANIZED BY:

DEVKI ENERGY CONSULATNCY PVT. LTD.

BARODA

DATE: 09TH & 10TH AUGUST,2004

VANUE:

HOTEL NALANDA, AHMEDABAD

TOPICS COVERED IN SEMINARTOPICS COVERED IN SEMINAR

ELECTRICAL MOTORSELECTRICAL MOTORSLIGHTINGLIGHTINGPUMPS/FANSPUMPS/FANSCOMPRESSORSCOMPRESSORS

EFFICIENT USE OF ELECTRICITY: EFFICIENT USE OF ELECTRICITY: WHY SAVE ELECTRICITY?WHY SAVE ELECTRICITY?

1. 80% of the power gen. in India is by thermal power stations, with efficiencies in the range of 30% to 35%. The Transmission and Distribution losses are 20% to 25%.One unit of electricity at the users end requires four units of primary fuel at the generating stations. Thus Electricity is a very expensive physical resource.

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2. The capital costs of power stations are

Rs 4 to 5 crores per MW i.e.

Rs. 40,000/- to Rs 50,000/- per KW.If transmission and distribution cost are considered, this figure increases by another 50% to 60%. Thus electricity is also a very expensive economic resource.

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3. The construction of the power stations requires a gestation time of 5 to 10 years due to problems related to investment, fuel linkages and environmental clearances.

4. There is no simple, economically viable technology for storing electricity; hence demand and supply have to match instant. The capacities created to meet peak demand remain idle during off-peak periods. Continue……Continue……

5. Energy conservation projects can be executed in periods ranging 6 to 24 months at costs ranging from Rs 0.2-1.0 crore per MW i.e.Rs 2,000 to 10,000 per kW.Saving electricity leads to reduction in environmental pollution, which is good for the society as a whole.

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6. 1 Kwh of electricity generated at thermal power stations leads to 3015 k cal of waste heat,1kg of CO2,0.6kg of NO2,0.9kg of CO,0.007kg of SO2,

0.201kg of fly ash.

ELECTRICAL MOTORSELECTRICAL MOTORS

Electricity consumption:

70% by Electrical motor

10% by Lighting

10% by Electrochemical application

10% by Heating and similar applications.

ELECTRIC MOTORS

OPPORTUNITIES FOR ENERGY CONSERVATION

1. Stopping idle or redundant running of motors

2. Matching motor with driven load

3. Improving transmission efficiency

4. Use of high efficiency motors

5. Improvement in motors systems

STOPPING IDLE & REDUNDANT OPERATIONS OF MOTOR

Idle running of conveyor, air comp., exhaust fan, cooling tower fan etc. is likely in any plant.

Redundant operation is equipment operating without any significant impact on quality & quantity of production.

Automatic or manual switching off of equipment gives good energy saving with small or zero investment.

OVERSIZED MOTORSOVERSIZED MOTORS

Motor efficiency remains almost constant or drops very marginally up to 50% load and then drops quite sharply at loads below 50%.

VARIATION OF MOTOR EFFICIENCY WITH LOAD

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A. Higher investment cost due to large size.B. Higher running cost due to decrease in efficiency.C. Higher maximum demand due to poor power factorD. Higher cable losses and demand charges.E. Higher switch gear cost.F. Higher space requirement.G. Higher installation costs.H. Higher rewinding cost (in case of motor burnt out)

OVERSIZED MOTORS LEAD TO THE FOLLOWING PROBLEMS:

V-belt drives have an efficiency of 85% to 90%.

Modern synthetic flat belt have an efficiency 96% to 98%

5% to 8% savings can be done by replacing V belt by synthetic flat belt

IMPROVING TRANSMISSION EFFICIENCY

High efficiency motors are being manufactured by some Indian manufacturers and most foreign manufacturers.

High efficiency motors provide good energy saving opportunities, especially for new purchases.

HIGHER EFFICIENCY MOTORS

While purchasing new motors, life cycle costing ,Which considers both initial cost and running cost for about 10 years, should be done in Table given below:

Motors Rating(kW)

7.5 7.5 37 37

Efficiency 0.86 0.88 0.92 0.93Power i/p kW 8.72 8.52 40.22 39.78Running hours 6,000 6,000 6,000 6,000

Energy i/p 52,320 51,120 2,41,320 2,38,680Running cost@Rs 5/kWh

2,61,600 2,55,600 12,06,600 11,93,400

Running cost for 10 yrs

26,16,000 25,56,000 1,20,66,000 1,19,34,000

First cost(Rs) 20,000 22,000 1,00,000 1,10,000First cost as % of Running cost for 10 yrs

0.8 0.8 0.8 0.9

Where the existing operating efficiencies of motors may be poor, replacement of motors with new, properly sized, efficient motors may be worthwhile. Following points may be noted:1. Even a small motor of 7.5 kW consumes, at

full load ,electrically worth Rs 23 lakhs in 10 yrs. Similiarly, a 37kW motor can

consume electricity worth Rs 1 crore in 10 years.

2. The first cost is only about 1% to 2% of the running cost for 10 yrs; Running costs are predominant in life cycle costing.

3. A small difference in motor efficiency can have a significant effect on running cost.

4. When economically justified, motors may be replaced, even if these have been

recently installed.

EFFECT OF VOLTAGE UNBALANCE ON MOTOR PERFORMANCE

If measure voltages are 420v,430v,440v. The avg. is 430v and deviation is 10v.

% Un balance =10v * 100 = 2.3%

430

1% voltage unbalance will increase motor loss by 5%

If motor is oversized and continuously loaded below 30% motor can be presently connected in to star connection.

OPERATION OF DELTA CONNECTED MOTOR IN START CONNECTION

CASE STUDY Operation of delta Connected Motor In

Star Connection A 25hp/18.5kw motor was driving a cooling water circulation pump.

The electrical measurements in delta connection were as follows:

Data Delta Star

Voltage 415 415

Current 18.5 9.5

PF 0.505 0.873

Power I/p 6.72 5.96

Speed 1,469 1,454

RESULTS

The power saving was 0.76kw, it may be noted the current has dropped by 49 % but the power saving is only 11%.

RECAPE OF MOTORS

1. Stopping idle or redundant running of motor.

2. Betn. 50% to 100% loading motor efficiency is almost same.below 50% loading motor efficiency drops significantly. Try to ensure motor are not loaded below 50% of their rated load.

3. Explore possibility of connection of motors which are loaded below 30% in star connection.

4. Soft starter to reduce motor starting current.if motor load is less than 30% for long period soft starter will save energy.

5. Use synthetic flat belt in place of v belt drives

LIGHTINGLIGHTING

1. Consider day lighting/ sky lighting to reduce energy consumption during day time.

2. Reduce excessive illumination levels to adequate and comfortable levels by switching off/delamping etc.

3. Considering lowering the fixtures to improve lighting level and also reduce the number of fixtures.

INTEGRATED APPROACH TO LIGHTING

4. Reduce general lighting and use task lighting to facilitate use of low voltage lamp as

specially CFLs. 5. Use voltage controller to reduce illumination

and voltage if excessive voltage persist.6. Control lighting with timers photocell and occupancy sensor.7. Replace mercury vapour lamp with sodium vapour lamp.8. Use more electronics ballasts in place of conventional electromagnetic ballasts.

VARIATION IN LIGHT OUTPUT & POWER CONSUMPTION WITH

VOLTAGE VARIATIONParticulars 10% lower volt 10% higher volt

Fluorescent lamps

Light output Decreased by 9% Increased by 8%

Power input Decreased by 15% Increased by 8.1%

HPMV lamps

Light output Decreased by 20% Increased by 20%

Power input Decreased by 16% Increased by 17%

HPSV lamps

Light output Decreased by 26% Increased by 30%

Power input Decreased by 20% Increased by 26%

PUMPSPUMPS

INTEGRATED SYSTEMS APPROACH TO PUMPING

Optimizing Use of WaterOptimal use of water signifignatly reduce raw

water pumping energy consumption. Instrumentation for flow measurement is to be installed. Selection of Pumps to match Head/Flow Requirements

Pumps have good efficiency in a very narrow flow zone;operation at higher or lower than design flows can lead to drastic drop in efficiency. Mismatch in pump selection is often overcome by throttling of wastage of energy. This leads to drops in pump efficiency and more several drop in the overall system efficiency.

Motor I/P 100%

Motor I/P 100%

Motor 90%

Pump 85%

Head loss in v/v & piping

20%

Losses due to leakage,extra

flow 20%

49 % Useful power for over coming static head & pipe friction losses

12.2% Wasted Power

15.3% Throttling

losses

13.5% pump losses

10% Motor Losses

Motor 85%

25.5% Pump Losses

90% Pump I/P

15% Motor Losses

85% Pump I/P

Pump 70%

Head loss in v/v & piping

50%61.2% output 29.75% output

Losses due to leakage,extra

flow 20%

76.5% Pump O/P 59.5% Pump O/P

29.75% Throttling

losses

14.8% Wasted Power

15 % Useful power for over coming static head & pipe friction losses

Well designed pump system Practically observed pump system

Pump specification 75HS,1600lpm,22m 125HS,3300lpm,25m

Pump efficiency 68% 78%

Pump I/P 9.1 kW 15 kW

Motor efficiency 87% 88%

Motor I/P 10.45 kW 17.04 kW

Annual Energy Cons(@6000 hours)

62,700kWH 1,02,272 kWH

Annual Running Cost(@Rs5.00per kWH)

Rs.3,13,500/- Rs.5,11,360/-

Running cost for 10 years

Rs.31,35,000/- Rs.51,13,600/-

Initial cost (Pump & motor0

Rs.40,000/- Rs,70,000

Initial cost as % of running cost for 10 years

1.3% 1.4%

Motor and Pump efficiency

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SHAFT POWER FOR MOTOR & FLOW FOR PUMP

MOTORS

PUMPS

Use of Variable Speed drivesUse of mechanical, electrical or electronic variable speed drives can help in improving the pumping system efficiency in cases that require variable flow or incases where the pumps are oversized and the flow is controlled by throttling of valves. This is a powerful technology for drastically improving pumping system efficiencies.

VARIABLE SPEED DRIVE VARIABLE SPEED DRIVE OPTIONSOPTIONS

Steam TurbinesSteam TurbinesVariable cone pulleysVariable cone pulleysStepped pulleysStepped pulleysGears with stepped speed ratiosGears with stepped speed ratiosPositive infinitely variable (PIV) drivesPositive infinitely variable (PIV) drivesHydraulic couplingsHydraulic couplingsEddy current couplingsEddy current couplingsMulti-speed motorsMulti-speed motors

Optimizing Pipe line Sizes

Pipe friction losses depends on the pipe diameter,material, surface condition and age. Use of larger pipe can reduce losses.

Pipe pressure drop α (pipe diameter)5. Pipe fitting like valves and bends should be sized and designed correctly to minimize losses.

• Maintenance

Wear and Tear of the pumps and scaling of pipes and heat exchangers can affect the energy consumption. Proper maintenance of pumps and proper water

treatment is necessary to maintain reasonable efficiencies.

PUMP & FAN PERFORMANCE CHARACTERISTICS

Typical performance characteristics of centrifugal pumps & fan are shown below

(a) Head or pressure α flow

(b) Power α flow

(c) Efficiency α flow

A. The pump head pressure decreases with increase in flow.Blowers also have a similar characteristic.except that the pressure increases slightly from zero flow & the decreases with increasing flow.

HEAD OR PRESSURE α FLOW

B. Due to reduction in pump/blower efficiency at lower than design flow, the power consumption does not drop significantly at lower flows are achieved by throttling of valve/dampers. At 0 flow (valve damper shut-off condition) pumps & blowers consume about 40% of their rated power. In case of electric motor at 0% of shaft load power consumption is only 5% of rated load.

POWER α FLOW

EFFICIENCY α FLOW

C. The pump/blower efficiency increases with flow. reaches a maximum & then decreases with further increase in flow. The efficiency drops significantly on both sides of the best efficiency point. In the case of pump/blowers ,at 50% flow, The efficiency can be even 20% points below the best efficiency.

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Pump Performance Characteristics

Operation of pumps at flow less than 25% can lead vibration, premature failure of seals etc.

Operation of pumps at flows which are significantly higher than the rated values, can lead to serious operational problems like cavitations, impeller wear out etc.

Operation of blowers at very low flows can lead to unstable operation leading hunting.

ENERGY SAVING BY MATCHING PUMPS & FANS WITH THEIR SYSTEM

Changing Impellers Pumps are generally designed to accommodate Impellers of Different diameters in the same casing, so that the same model can cater to a reasonably wide range of head/flow requirements

Trimming of Impellers If mismatch between the system and the pump is small, trimming (reduction of impeller diameter by machining) of impellers can shift the pump head/flow characteristics downward to match the system head.

Change of pump or fan speed also shifts the head/flow charac.This is very convenient method of matching the pump/fan charac with system charac. Flow α Speed Head α (Speed)2

Power α (Speed)3

CHANGE OF SPEED

REPLACEMENT BY PROPERLY MATCH & EFFICIENT PUMP

Mismatch between pumps/fans and system are large, replacement of pumps/fans by new properly match pump of good efficiency can leads to significant energy saving

RECAP FOR PUMPS/FANS

1. Check whether the pump/fan is properly sized. Check whether the head/pressure/flow is matched to the system requirement.

2. Any excessive throttling of valves or dampers indicates that the pump/fan is mismatched to the system. Consider change of speed, impeller replacement or replacement of pumps/fans with appropriate high efficiency pump/fan.

3. Check sizing or pipes and ducts from the point of friction losses. Consider the use of larger pipes/ducts if relevant.

4. For equipment at very high levels, consider the use of booster cooling water pumps or separate small pumps instead of selecting the main pumps with very high heads.

5. Check pumps/fans which are noisy and have high vibration. These may be due to mis-alignment, lose belts or off-point operation. All these can contribute to higher energy losses. Cavitations pumps can lead to damage of impellers

COMPRESSORSCOMPRESSORS

Compressed air is very expenssive utility and should be used optimally.At 7 bar Pressure 100CFM air requires 16 to 17 KW.Utilization efficiency of compressed air is very poor due to leakage, pressure, losses and poor conversion efficiency of pneumatic equipments

COMPRESSORS

Pressurized Air in Receiver

10% Distribution losses due to piping

10 to 50% Air leakage

35% Conversion losses

Useful Energy

INTEGRATED SYSTEMS APPROACH TO COMPRESSED AIR:

Reducing Compressed Air Use1. Uses of compressed air like cleaning, material conveying,

are not justified.

2. For applications like cleaning and conveying, blowers can be used.

3. Electrical tools can replace pneumatic portable tools.

4. In many plants,pneumatically operated controls are being replaced by electric and electronic controls, thus reducing the requirement for the instrumentation air.

In all these cases, the potential for energy saving is @ In all these cases, the potential for energy saving is @ 80 % 80 % to 90 %.to 90 %.

PRESSURE REDUCTION

1) A through study of pressure requirements and the compressor discharge pressure should be done.

2) 10% reduction in compressor discharge pressure reduces energy consumption by about 5%; the saving due to leakage reduction are additional.

AIR LEAKAGE REDUCTION1) Compressed air leakage can vary from 5% to

70 % or higher depending on the house keeping efforts on the compressed air distribution system.

2) All plants should attempt to operate at leakage levels below 5%.Even a small leakage of 50 CFM is equaling to a loss of Rs 3.0 lakhs per annum (@ Rs 4.50 per kWh).

3) Air leakage generally take place from threaded pipe joints, hose connections, valve stems, buried underground lines etc.

ENERGY LOSS DUE TO COMPRESSED AIR LEAKAGE AT 7 BAR

Hole

Dia in Inches

Free air wasted CFT/Annum

Energy wasted Kwh/year

3/8 7,99,00,000 2,19,000

1/4 3,55,00,000 97,200

1/8 88,80,000 24,300

1/16 22,20,000 6,060

1/32 5,53,000 1,510

Maintenance

Routine maintenance checks on compressors and the distribution system is necessary to ensure efficient compressed air generation and utilization. The performance of reciprocating compressors can deteriorate significantly due to poor maintenance.

Drive Transmission

For belt driven compressor, the possibility of use of more efficient, synthetic flat belt should be explored.

Electric Motor

The motor should be selected close to the rated power requirement of the end-use equipment. For the new purchases, high efficiency motors may be preferred.

AIR INTAKE TEMPERATURE

Cooler in take air results in lower energy consumption, every 30C drop in suction air temperature improves the compressor efficiency by 1%.Hence care can be taken to ensure that the compressor room is well ventilated and the room temperature is as closed as possible to the ambient temperature

INTER-COOLER PERFORMANCE

Poor heat transfer in the inter-cooler, due to fouling, will result in high air temperature in the next stage. The higher specific volume of air results in higher energy consumption. The proper water treatments important to maintain the efficacy of inter-cooler.  

ESTIMATION OF AIR LEAKAGE LEVEL

The leakage level can be estimated by observing the average compressor loading and unloading time,

On load time Air Leakage = Q x ------------------------------------ On load time + Off load time

Where,Q = Compressor capacity (as estimated from the pump-up test)

1. Reduce compressor air leakage to as low as possible .

2. Avoid use of compressed air for application like cleaning, material cleaning etc.

3. Close valves of compressed air line to the equipment which are not in use.

4. Use properly engineered nozzle to reduce air consumption.

5. Replace pneumatic controls by hydraulic options. Continue..

RECAP OF COMPRESSOR

6. Reduce air compressor discharge pressure to lowest acceptance level.

7. Use Flow/Pressure regulators for sub headers of sections of large plant and use of pressure regulator at end use points.

8. Increase storage capacity to take care of sudden impulse demand of compressed air. Do not increase the pressure setting to catch demand.

9. Estimate pressure drops in pipe lines. A drop of 0.3 bar from compressed air station to farthest end use point is permissible check line filters for excess pressure drops.

10. Reduce air inlet temperature Colder air is denser and thus for each volume of compressed, allows the compressor to deliver more kg of air.

11. Use more efficient compressors.

Wastage of Energy is a Wastage of Energy is a crimecrime

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