A typical coal-fired power plant burns 310 metric tons of coal every hour to generate 790 MW of electricity. 1 metric ton= 1000 kg. The density of coal is 1500 {\rm kg}/{\rm m}^{3} and its heat of combustion is 28 \;\rm MJ/kg. Assume that all heat is transferred from the fuel to the boiler and that all the work done in spinning the turbine is transformed into electrical energy.

Question

A typical coal-fired power plant burns 310 metric tons of coal every hour to generate 790 MW of electricity. 1 metric ton= 1000 kg. The density of coal is 1500 {\rm kg}/{\rm m}^{3} and its heat of combustion is 28 \;\rm MJ/kg. Assume that all heat is transferred from the fuel to the boiler and that all the work done in spinning the turbine is transformed into electrical energy.
What is the power plant's thermal efficiency?

bobpursley · Answer

heat in fuel:

massflowrate*heat/kg
310tons/hr*1000kg/ton*1hr/3600sec*28MJoule/kg

efficiencty= 790MW/above

check my thinking. That is about typical for a thermal plant. In very high pressure, high temp (3000F, 3000PSI), efficencies are boosted some, but the elec generators hold the eff lower.