Large-scale thermionic power generation from fossil fuels

A theoretical analysis is made of the use of thermionic diode convertors in electrical power generation from fossil fuels. It is shown that the best way to use such a diode is as a `thermodynamic topper¿: heat rejected from the diode stage is used in conjunction with a conventional steam generator. Various possible diode schemes are discussed: a diode having a caesium-on-tungsten cathode operating at about 1150°C shows most promise and should lead to an increase in overall efficiency from about 40% for the steam cycle to about 46% for the combined cycle.