Combining fuel cells with fuel-fired power plants for improved exergy efficiency

The thermodynamic advantages of fuel-cell systems are studied to: 1.(i) evaluate the increase in plant exergy efficiency when incorporating fuel-cell units into electrical power generating stations and2.(ii) identify and discuss their effect on the components of such plant systems. Topping conventional Rankine cycle power plants with a range of commercial fuel cells is shown to increase the exergetic efficiency of the plant by up to 49%, raising that efficiency from the value of 41.5% for the conventional power plant without fuel cells to about 62% for the fuel-cell-topped power plant. This improvement stems primarily from the improved exergetic efficiency of fuel oxidation in these proposed topping power plants, as contrasted with the highly dissipative combustion process in conventional fuel-fired ones.