3.6 The Carnot Efficiency

Practice

For a coal fired utility boiler, the temperature of high pressure steam would be about 540 degrees C and T_cold, the cooling tower water temperature would be about 20 degrees C. Calculate the Carnot efficiency of the power plant?

Step 1
Convert the high and low temperatures from Celsius to Kelvin:

Step 2
Determine the efficiency using the Carnot efficiency formula:

From the Carnot Efficiency formula, it can be inferred that a maximum of 64% of the fuel energy can go to generation. To make the Carnot efficiency as high as possible, either T hot should be increased or T cold (temperature of heat rejection) should be decreased.