Mitigating the space charge effect in a thermionic energy converter by controlling the interelectrode distance in-situ

The space charge cloud formed near the surface of an electron emitter inhibits further electron emission and transport. This effect significantly reduces the conversion efficiency in thermionic energy converters (TEC). We devised a variable interelectrode distance TEC device with an yttria-coated iridium disc emitter and a tungsten sheet collector. By reducing the interelectrode gap from 550 $\mu\mathrm{m}$ to 50 $\mu\mathrm{m}$, we observed a two-orders-of-magnitude increase in the collector current.