In the recently completed Fraunhofer lighthouse project ElKaWe, researchers from six Fraunhofer institutes have made significant progress in the development of highly efficient solid-state heat pumps in terms of materials, electronics and system design. The focus was on the use of electrocaloric materials, which do not require harmful refrigerants and potentially work more efficiently. At Fraunhofer IKTS, the potential of ceramic materials was investigated.

Solid-state heat pumps for heating and cooling use the electrocaloric effect to transport heat by applying and removing an electric field. Compared to today's compressor-based heat pumps, electrocaloric heat pumps work without harmful refrigerants. They are also potentially more energy efficient, quieter and require less maintenance because they have no moving parts like compressors.

The electrocaloric active material is crucial for the efficiency and durability of electrocaloric heat pumps. Various polymer and ceramic materials were tested in the consortium.

Fraunhofer IKTS developed ceramic multilayer components based on PMN-PT (lead magnesium niobate/lead titanate) that met the high requirements for dielectric strength and operating frequency. Initial long-term tests prove the high stability of the ceramic components: even after more than 70 million cycles, no change in the electrocaloric effect occurred.

The lead-free barium strontium tin titanate (BSSnT) proved to be another promising ceramic material that can be used to manufacture electrocaloric components in the future in accordance with the applicable RoHS (Restriction of Hazardous Substances) guidelines.

The successful collaboration on the ElKaWe project has led to the development of several demonstrator systems that show the potential of electrocaloric materials for heat pumps. Initial tests have shown that electrocaloric heat pumps can match the efficiency of conventional compressor systems using current materials. The progress in materials development and system integration marks an important step towards marketability and could have a lasting impact on the future of heating and cooling technology.