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ATAR SINGH

Dy. DIRECTOR

NPTI FARIDABAD

ENERGY AUDIT OF AUXILIARY POWER CONSUMPTION

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Energy Conservation in Power

Utility

Power plant produces electrical energy

and also consumes a substantial amountof energy in the form of auxiliary

consumption required for various plant

equipments and services

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Energy Conservation in Power Utility

Achieved mainly by:

Operating the equipments at maximumefficiency and

Reduction of auxiliary Power

consumption

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The auxiliary power consumption (APC) varies from 6-14% ,

depending on Size of plant ,use of TDBFP &age of plant

The 500 MW units register the least APC, largely due to the

incorporation of TDBFP.

In some of the old 110 MW plants, APC consumption of 14%is also observed.

Energy audit in a vast thermal power station (TPS) is better

tackled when the thermal power plant operations are

segregated into different sub-areas like:

main plant auxiliaries, draft system (consisting of ID/FD/PAfans), feed water system [consisting of Boiler Fed Pumps

(BFPs) / Condensate Extraction Pumps (CEPs), Circulating

Water (CW) system-including Cooling Tower (CTs)], and off

sites (consisting of coal handling plants, ash handling plants,

air compressors, AC plants, station lightings etc.).

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Auxiliary Power Consumption in ThermalPower Plant is major source of energyconsumption.

During the financial year 2007-08 totalgeneration by coal plant was 488157.46 MUswith PLF 78.75.

Auxiliary Power Consumption was 8.17%.

If this APC gets reduced only by 0.17%then it is equivalent to fresh capacity additionof 120 MW without any investment.

APC Scenario In India

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Trombay Station of Tata Power Co. Ltd achieved lowest

auxiliary power consumption (4.30%) in the country.

Among Central Sector Stations, Talcher

STPS of NTPC achieved the lowest auxiliary

power consumption (5.34%).

Among State Sector Stations, Chandrapur

STPS of MAHAGENCO achieved the lowest

auxiliary power consumption (7.40%).

Among different capacity groups, the lowest

auxiliary power consumption was 6.13% in 500

MW group.

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Requirement of works power with load

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Factors Affecting Auxiliary Power

Consumption

- Unit Generation and load Pattern

- Operation of Plant Auxiliaries

- Service auxiliary such as Illumination , air

conditioning

- Unit Startup / shutdown

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

Data collection

Measurements & Observations

Exploration for energy conservation measures

Report preparation

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

DATA COLLECTION

Motor details required-

ID code, Application, Make, Brief details of drivenequipment, Type of the Motor, Motor kW, Motor frame,

Duty, Rated RPM, Rated p.f., Rated motor efficiency ,Motormake, Motor voltage, Rated current of motor,Year,Operating hours,Energy meter installed or Not , No. oftimes the motor is rewound

Collect the above information for all motors to be covered inthe energy audit.

Collect the motor efficiency curves

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

Instruments Required-

Power Analyzer: Used for measuring electrical parameters

such as kW, kVA, pf, V, A and Hz Infrared pyrometer (In case any heating of cable or

motor is suspected)

Stroboscope: To measure the speed of the driven

equipment and motor

The above instruments can be used in addition to thecalibrated online / plant instruments

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

Parameters to be measured-

Energy consumption pattern of motors (daily / monthly/yearly consumption if available)

Motor electrical parameters (kW, kVA, Pf, A, V, Hz,

etc.) for individual motors Equipment operational details

While conducting the measurement or performanceevaluation of any system simultaneously, the followingneed to be noted

Unit load of the plant Date & time of measurement Instruments used for measurement Frequency of the measurement

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

MEASUREMENTSAND OBSERVATIONS

System detailsDetailed interactions with the plant personnel

Energy consumption Pattern

If the plant is monitoring the energy consumption, itis suggested to record the data and monitor the daily and

monthly consumption pattern

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

Equipment AnnualConsumption

MWH

Average Load

KW

% of TotalGeneration

% of total APC

Air Compressors

Coal Handling Plant

Raw Water pumps

DM water pumps

A/C systems

ESP

Total

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

Equipment AnnualConsumption

MWH

Average Load

KW

% of TotalGeneration

% of total APC

Boiler Feed Pump

Condensate extraction

Pump

CW Pumps

ID Fans

FD Fans

PA Fans

Mils

CT Fans

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MW % MW % MW % MW % MW % MW %

BFP's 4.52 2.78 4.29 2.98 4.52 3.39 - - - - 13.34 1.02%

CEP's 0.43 0.26 0.43 0.30 0.41 0.31 1.69 0.45 1.78 0.42 4.73 0.36%

FD's 0.35 0.22 0.31 0.22 0.30 0.23 1.21 0.29 1.26 0.29 3.43 0.26%

ID's 2.26 1.38 2.08 1.44 2.34 1.51 8.18 2.24 7.25 1.51 22.12 1.69%

PA's 2.31 1.41 2.38 1.65 2.36 1.52 4.85 1.34 4.82 1.00 16.72 1.28%

Coal Mills 1.21 0.74 1.53 1.06 1.69 1.08 2.92 0.81 2.92 0.61 10.25 0.79%

CHP 0.57 0.35 0.57 0.39 0.57 0.36 1.11 0.31 1.11 0.23 3.92 0.30%

AHP 0.47 0.29 0.47 0.33 0.47 0.30 0.52 0.14 0.52 0.11 2.45 0.19%Air

Compressors

0.42 0.26 0.42 0.29 0.42 0.27 0.38 0.11 0.38 0.08 2.04 0.16%

Others

(CWPs,

RWPs, DM

Plant, etc )

3.89 2.37 4.21 2.92 4.11 2.64 10.28 2.84 10.22 2.13 32.70 2.50%

Total 16.42 10.06 16.67 11.58 17.18 11.61 31.14 8.53 30.26 6.38 111.70 8.56%

MW %

Total Generation 1305.57 81.60 (of installed capacity)

Auxiliary Power Consumption 111.7 8.56 (of actual generation)

Contribution

To APC By

Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Over All

STEPS INVOLVED IN CONDUCTING ENERGY

AUDIT

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Motor loading survey

Details Rated Kw Rated Efficiency Rated Speed Measurement of parameters Power factor

kVA KW drawn Frequency Harmonics Motor speed Driven Voltage Current

Power equipment speed Driven equipment parameters Operational observations Transmission % loading on the motor

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

Motor loading can be estimated by:

% Loading =

Input kW to motor x 100

---------------------------------------------------------------------

Name plate kW /Name plate full load motor efficiency

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

While conducting motor load survey,

observations on machine side:

parameters such as speed, load, pressure,temperature, etc., (as relevant) are also taken

availability of load-end capacitors for PF

correction & energy meters for monitoring is alsolooked into for each case.

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

Motor Rewinding History

comparison of no load current and stator resistance

per phase of a rewound motor with the original no-load

current and stator resistance at the same voltage can be one

of the indicators to assess the efficacy of rewinding.

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

Power Factor Correction

Induction motors are characterized by power factorsless than unity, leading to lesser efficiency (higher

overall operating cost) associated with a plant'selectrical system.

Capacitors connected in parallel (shunted) with themotor are typically used to improve the power factor

The impacts of PF correction include reduced kVAdrawn , KVAR & current, reduction of transformer load,

Reduction of cable losses, reduction of switch gear rating, Enhanced life of equipment

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

EXPLORATION OF ENERGY CONSERVATION

MEASURES

Replacement / sizing of motors Opting for energyefficient motors, Use of high efficiency motors,

Use of energy efficient transmission

Replacement of pulleys

Direct coupling

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STEPS INVOLVED IN CONDUCTING

ENERGY AUDIT

Analysis of observations

o Loading pattern - % loading

o Comments of power supply quality

The BIS standards specify that a motor should becapable of delivering its rated output with a voltage

variation of 6 % and frequency variation of 3 %. Motor

o Identified motors with less than 50 % loading, 50 75 %

loading, 75- 100 % loading, over 100 % loading

o Identified motors with machine side losses / inefficiencieslike idle operations, throttling/damper operations

o Motor load survey is aimed not only as a measure to

identify motor efficiency areas but equally importantly, as

a means to check combined efficiency of the motor, driven

machine and controller

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AUXILIARY POWER CONSUMPTION

Operating only 4 mills instead of 5 mills in 210 MW units

Shutting of CTs cells in conjunction with favorable weather

conditions and replacing existing aluminum cast and GRP blades

with FRP

avoiding idle running of conveyors & crushers

incorporating soft starter - energy savers etc.

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STRATEGY

Variable frequency drive for PA Fans & ID Fans & CEPs

Air in-leaks in draft system (O2 measurement) blanketing

Replacement of inefficient BFPs as a part of R& M of the oldplants.

Clipping of one stage from the multi stage BFPs to balance thepressure drop requirements between HP heaters, economizer andboiler drum etc.

Use of higher pressure in the deareator to commensurately

reduce BFP power consumption (reduced head developed) Running of two CEPs instead of 3 CEPs (3 CEPs are run to avoidtripping due to lower frequency in some of the power plants)

Application of variable speed drives

Installation of hydraulic turbine instead of feed regulating sectionto avoid pressure drops and to generate additional power

AUXILIARY POWER CONSUMPTION

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