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Sanjeev Agarwal

In our childhood days our grandparents used to say “” Boond Boond se ghada Bharta Hai, ( Every single drops makes ocean), when we remember these word the expression and accent in which they used to say make us sentimental and make more effect on us then any English idiom synonyms to this.

These phrase are more relevant to Power Generation company as follow of of these word by saving every unit can save tremendous amount of auxiliary Power, which may lead to save terrific saving of Natural resources like Coal,water,etc, which will ultimately effect reducing cost of generation resulting in increasing EBDITA

Thermal power plants have played a vital role in improving the power and economic position in India. In every economy, power is a critical input for its development . Quality of life is measured by per capita power consumption, in developed countries per capita consumption of power is Higher than developing countries,hence it is said that quality of life is better in developed countries than developed country.

Also Power is the critical for the economy development of a country. As the economy grows, the need for more and more power . Post independent there is substantially Increase in Installed capacity, from 1362 MW to 3,31,118 MW as on 31ST oct 2017.

Auxiliary power is consumption of power by various process auxiliaries to generate electricity, following are the main process in a Thermal power Station ;

  • Coal preparation consist of Fuel preparation system, dryers,Magnetic Separators .
  • Boiler and auxiliaries the basic components are Furnaces and Burners and steam and superheating.
  • Air pre heater and Re heater
  • Steam turbine
  • Condenser
  • Boiler feed Pump
  • Cooling tower
  • Ash handling system
  • Generator

Auxiliary power consumption is calculated by following formula :

Auxiliary power consumption (APC) plays an important role for mitigating fuel consumption and generating electricity with the same configuration of the plant.

APC% = (Gross Generation-Energy Export)*100

Gross Generation

Thus if in a plant which is having capacity of 600 MW and working on 100% PLF on any particular day and Energy sent out is 546 MW then Auxiliary power would be 9% Calculated as below :

APC%= (600MW-546M W) *100


Financial Impact of Saving of Auxiliary power :

Financial impact of saving in 1% of Auxiliary power can be understand by following table Showing comparison of Qty of coal required and cost of Auxiliary Power of a Thermal power plant which is having capacity of 600 MW and Running at Plant load factor 90% :

Table (1) : Showing comparison coal water at 9% and 8% Auxiliary power consumption

Auxiliary Power consumption
Sr no Particulars UOM 9% 8%
1 Capacity MW 600.00 600.00
2 Generation daily MU 12.96 12.96
3 Generation yearly MU 4730.40 4730.40
4 Auxiliary Power Consumption MU 425.74 378.43
5 Energy Sent Out MU(4-5) 4304.66 4351.97
6 Heat Rate (Kcal/Kwh) 2400.00 2400.00
7 Average GCV (Kcal/Kg) 4000.00 4000.00
8 Coal consumption Per Unit(7/8) 0.60 0.60
9 Coal cost Rs/KG 4.00 4.00
10 Yearly cost of Generation Rs in crore 1135.30 1135.30
11 Per unit cost of Energy sent out Rs/kwh(10/5) 2.64 2.61
12 Saving in per unit cost of Generation 0.03
13 Coal Qty for Auxiliary Power Lakh MT(4*8) 2.55 2.27
14 Saving on coal Qty Lakh MT 0.28
15 Cost of Auxiliry Power consumption(yearly Rs crore(4*8*9) 102.18 90.82
16 Saving in total coal cost Rs crore 0.00 11.35

Table (2) Showing comparison water cost and qty at 9% and 8% Auxiliary power consumption

Auxiliary Power consumption
Sr no Particulars UOM 9% 8%
1 Capacity MW 600.00 600.00
2 Generation daily MU 12.96 12.96
3 Generation yearly MU 4730.40 4730.40
4 Auxiliary Power Consumption MU 425.74 378.43
5 Energy Sent Out MU(4-5) 4304.66 4351.97
6 Per unit water Required Ltr 2.30 2.30
7 Water required for Auxiliary power Cum meter 979192.80 870393.60
8 Saving in water QTY Cum meter 108799.20
9 Water cost per Cubic meter Rs 15.00
10 Saving in water cost Rs 1631988.00

From comparison of two table at 9% and 8% auxiliary power we can conclude :

  • There is saving of 28000 MT coal due to saving of 1% Auxiliary power
  • Coal cost come down by 11.35 crore, which will increase EBDITA of the company.
  • Saving of water is 1.08 cubmic meter resulting in Rs 16 lakh saving.

We can see that how both natural resources water and coal can be save, both are available in abundant and saving of these resources are high priority of the day .

Table 3 : Showing reduction in Variable billing charges due to Decrease in Auxiliary power

Auxiliary Power
Sr no Description Formula Units 9% 8%
1 Price of Primary Fuel Pp Rs/Kg 4.00 4.00
2 Auxillary Consumption Aux % 0.09 0.08
3 Gross Heat Rate Heat Rate kCal/kWh 2400.00 2400.00
4 Average GCV of Primary fuel GCV kCal/kg 4000.00 4000.00
8 Quantity of Primary fuel Qp = (HR-QsxOCV)/GCV kg/kWh 0.60 0.60
9 Rate of Energy Charge (REC) 100 x {Pp x Qp }/(100-Aux) Rs/kWh 2.64 2.61
10 Reduction of Variable billing Charges Rs/kWh 0.0287

With reduction of Auxiliary power there is saving of variable charges, this will increase Merit order of Dispatch of power company.

Steps for saving in Auxiliary Power

As we can see there is massive impact of Auxiliary power consumption (APC) plays an important role in EBDITA and Saving of Natural Resources, following are the step which can be taken for same :



By analyzing energy saving potential areas energy can be conserve efficiently.
2. Performance monitoring of each unit should be performed which include auxiliaries such as coal handling
3. plant, ash handling plant, water treatment plants and compressors.
4. Monthly performance tests should be conducted to evaluate boiler efficiency, condenser performance,
5. turbine cylinder efficiency, LP/HP heater performance, turbine heat rate etc.
6. Installation of variable feed drive should be done which can save 14% to 27% of energy.
7. Flue gas leakage can be reduced by replacing metallic joints with fabric joints
8. Use of soft starters can save considerable energy for the motors which operate on continuously variable load.
9. The moisture of coal should be removed before use otherwise it increases the load on boiler and hence decreases its efficiency.
10. Proper crushing of coal should be done which reduces the unburnt carbon and bottom ash.
11. Monitoring of Oxygen and CO to ensure a complete combustion and control combustion air to limit the dry gas losses.
12. Regular monitoring operating controllable parameters to gain efficiency and availability.
13. Monthly performance monitoring of the station should be reported in meting to the head of department.
14. Annual overhaul of units and auxiliaries should be done regularly based on the performance deterioration.


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July 2024