Hybrid mode cesium diode thermionic converter

In the hybrid mode diode thermionic energy converter (HYTEC), a small-current ignited (arc) discharge from a high work function portion of the isothermal emitter surface maintains the plasma and large output current in an adjacent unignited discharge from a low work function emitter portion with nearly zero arc drop. An approximate phenomenological-analytical model of HYTEC, based on similar models of the individual modes of Cs diode operation, accounts quantitatively for features distinguishing experimentally observed characteristics of HYTEC from those of the Cs diode. This degree of agreement suggests practically achievable HYTEC operation with nearly zero arc drop. The emitter temperature 1400 K, at which practical power density and efficiency are achieved experimentally here, permits use of superalloy hot shells in converters rather than the expensive coated refractory metals required before, which is crucial to economic feasibility for terrestrial applications of thermionic energy conversion. Optimization of the operating parameters identified here should permit the performance of HYTEC to be substantially increased even further. Published by AIP Publishing.