Question

the adiabatic flame temperature (theoretical maximum temperature) of black coal in air is over 2000^oC. If the ambient temperature is 20^oC then the theoretical maximum efficiency of a coal fired power station is approximately 87%.

Why then is the efficiency of even the best coal fired power stations less than 50%.

Answer 1

The efficiency of even the best coal fired power stations less than 50%, because the Energy loss in conversion of heat energy to electrical energy are very high. The steps for conversion of Heat energy from Coal to electrical energy. First is to heat water in the boiler which generate steam, than that high pressure steam is supplied to turbine from the turbine mechanical energy transfers to the generator and generate convert mechanical energy to electrical energy. So there are so many loss in the conversion of Chemical Energy(Coal) to Heat to Mechanical to electrical. So the theoretical maximum efficiency of coal combustion (i.e to convert chemical energy to heat ) is 87 %, but when we add the losses or efficiency of boiler, turbine and generator, it will come 50 % or less.The efficiency of even the best coal fired power stations less than 50%, because the Energy loss in conversion of heat energy to electrical energy are very high. The steps for conversion of Heat energy from Coal to electrical energy. First is to heat water in the boiler which generate steam, than that high pressure steam is supplied to turbine from the turbine mechanical energy transfers to the generator and generate convert mechanical energy to electrical energy. So there are so many loss in the conversion of Chemical Energy(Coal) to Heat to Mechanical to electrical. So the theoretical maximum efficiency of coal combustion (i.e to convert chemical energy to heat ) is 87 %, but when we add the losses or efficiency of boiler, turbine and generator, it will come 50 % or less.