Thermoelectronic generator design improves efficiency of heat and solar energy into electricity
The thermionic generator’s design, which is described in AIP Publishing’s Journal of Renewable and Sustainable Energy (JRSE), claims to circumvent the ‘space-charge effect’ problem that has limited current flow between the plates in previous attempts by using an electric field to pull the evaporated electrons away from the generator’s hot plate (emitter) and allows more of them to reach the cold plate (collector).
"Electrons are evaporated or kicked out by light from the hot plate, then driven to the cold plate, where they condense," explained experimental solid-state physicist Jochen Mannhart of the Max Planck Institute for Solid State Research in Stuttgart, Germany, the lead author of the JRSE paper. The resulting charge difference between the two plates yields a voltage that, in turn, drives an electric current, "without moving mechanical parts".
Mannhart, along with his former students Stefan Meir and Cyril Stephanos, and colleague Theodore Geballe of Stanford University, circumvented this problem using an electric field to pull the charge cloud away from the hot plate, which allowed electrons to fly to the cold plate.
"Practical thermionic generators have reached efficiencies of about 10 percent. The theoretical predictions for our thermoelectronic generators reach about 40 percent, although this is theory only," noted Mannhart. "We would be much surprised if there was a commercial application in the marketplace within the next five years, but if companies that are hungry for power recognize the potential of the generators, the development might be faster."
The hot test generator in action
Credit: J.Mannhart/MPG.de
More information about the research in the paper: ‘Highly-Efficient Thermoelectronic Conversion of Solar Energy and Heat into Electric Power‘
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