to rotate turbine of a thermal power plant, we use water as working fluid which has got very high heat capacity due to which lot of coal is to be burnt to generate lot of heat. Why don't we use some other working fluid which has lower heat capacity than water so that a lot of fuel may be saved?

Dear student,

To generate electricity we have to mechanically rotate the ‘rotor’. Energy is required to rotate the generator. Energy available in various forms like coal, oil and gas has to be converted to mechanical energy to rotate the generator. This conversion can take place in many different ways. The power plant does this conversion from the primary energy source to mechanical rotation and then to electricity. A small form of this generator is what we have in our car, the alternator. The car’s engine rotates the alternator which generates power for the car. A slightly bigger version is the portable generator driven by a petrol or diesel engine, normally used as a standby in case of a mains power failure.