Conversion of Heat to Electricity by Thermionic Emission

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Abstract
A heat engine and electric generator is described which is a vacuum or gas filled device containing a hot cathode and a cold anode. Heat at the cathode lifts electrons out of the cathode and to a high (negative) potential in the system. By collecting the electrons on a low work function surface, part of the potential energy may be retained to use in an external circuit. Thus part of the heat that lifts the electrons out of the cathode may be converted into electrical energy. Cs vapor filled tubes have been built and tested as thermionic converters. A hot surface ionized part of the Cs vapor to neutralize space charge between the cathode and anode. The Cs vapor was also used to adjust the work functions of the two surfaces. A thermionic converter has been built which converts 9.2% of the input heat into electricity. The output was 3.1 watts per cm2 of cathode surface—0.78 v at 4.0 amp per cm2 of cathode surface.