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Scientists claim solid-state heat pump breakthrough

The researchers at Fraunhofer IAF are already working on a further development of this electronics demonstrator.
© Fraunhofer IPM

GERMANY: Scientists in Germany are said to have achieved an important milestone in the development of solid-state electrocaloric heat pumps.

Electrocaloric heat pumps are seen as an alternative to current compressor-based technology, require no refrigerants and promise higher efficiencies.

Researchers at Germany’s Fraunhofer Institute for Applied Solid State Physics IAF claim to have reached a milestone in power electronics by creating an ultra-efficient circuit topology for voltage converters with over 99.74% electrical efficiency. 

Due to their technology, today’s heat pumps achieve only about 50% of the physical Carnot limit, while the electrocaloric heat pump can theoretically achieve 85%, researchers claim. Reaching this efficiency, however, depends to a large extent on the efficiency of the integrated power electronics.

The Fraunhofer Electrocaloric Heat Pumps project, or ElKaWe for short, is researching devices based on the semiconductor gallium nitride (GaN) in order to increase power density and efficiency.

For the first time, the researchers have now developed and optimised power electronics specifically for electrocalorics. They have succeeded in implementing an ultra-efficient circuit topology for voltage converters based on GaN transistors, achieving an electrical efficiency of 99.74% in the electrical power path. 

According to the Fraunhofer Institute team, the GaN-based multilevel DC/DC converter far exceeds the previous state of research of less than 90% conversion efficiency for electrical control of these novel heat pumps.

The significant increase in efficiency of the drive electronics has a direct effect on the coefficient of performance of the entire system, the team insists. Until now, electrocaloric heat pump systems were limited by the losses of the electronics, among other things. The increased electrical efficiency leads directly to a higher coefficient of performance of the entire heat pump system and is thus a milestone on the way to more efficient heat pumps. 

“Our ultra-efficient power electronics make it realistic for the first time to achieve well over 50% of the maximum theoretical coefficient of performance with electrocaloric heat pumps, even at the system level,” said Dr Stefan Mönch, a researcher in the field of power electronics at Fraunhofer IAF.

“There is still a lot of research to be done, but in future this technology could become a more efficient and completely emission-free solution for heating and cooling.”

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