New Technology to Convert Heat Energy into Electricity

WASHINGTON — New advancements in the research of thermionic conversion have allowed physicists to develop a new technology that converts heat energy, such as sunlight or heat burned from fossil fuels, into electricity.

Described in the American Institute of Physics’ Journal of Renewable and Sustainable Energy (JRSE), the thermoelectronic generator can convert heat energy into electricity with very high efficiency, according to researchers. The generators produce electricity by using the temperature difference between a hot and a cold metallic plate.

“Electrons are evaporated or kicked out by light from the hot plate, then driven to the cold plate where they condense,” said Jochen Mannhart of the Max Planck Institute of Solid State Research, lead author of the JRSE article, in a statement.

Previously, attempts to construct such a generator were unsuccessful due to the “space-charge problem,” which is created when the negative charges of the electron cloud that are exiting the hot plate cause other electrons to leave the hot plate as well. This was corrected, researchers said, by using an electric field to pull the charge cloud away from the hot plate, allowing electrons to fly to the cold plate. Because of this, the thermoelectronic generator developed in this study was much more efficient than those in the past.

“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,” Mannhart said. “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 JRSE article concluded that though the development of thermoelectronic generators will require further efforts, “no obstacles of fundamental nature appear to impede highly efficient power generation based on thermoelectronic energy converters.”