Heat pumps without compressors: Fraunhofer advances electrocaloric technology

What is an electrocaloric heat pump?

Electrocaloric heat pumps are an innovative, eco-friendly cooling and heating technology that use electricity to move heat without harmful refrigerants. They work by applying an electric field to special materials, making them heat up or cool down, similar to how modern refrigerators work but without gas or moving parts. This makes them quieter, more efficient, and better for the environment.

Latest advances from Fraunhofer

Researchers from the Fraunhofer-Gesellschaft research organisation, Germany, have recently completed a project dedicated to a novel concept: solid-state heat pumps based on electrocaloric materials that do not run on harmful refrigerants and could potentially be more efficient than compressor-based systems.

During the ElKaWe project (ElKaWe is short for electrocaloric heat pump in German), six Fraunhofer institutes worked together on the main technological components of electrocaloric heat pumps.

To enhance heat transfer rates in electrocaloric heat pumps, the team of researchers employed a patented design: active elastocaloric heat pipes (AEH). Here, latent heat transfer is achieved by the evaporation and condensation of a fluid on the caloric material. The fluids used here were ethanol and water, a great advantage over conventional heat pumps using refrigerants.

The approach based on heat pipes enables considerably faster cycle frequencies than conventional active pumping of a liquid. The liquid should evaporate and condense on the surface of the electrocaloric material up to ten times per second. This allows a lot of heat to be transported using little material, making it possible to build particularly cost-efficient systems in the future.

According to simulations, the efficiency of electrocaloric heat pumps with today’s materials is already equal to that of compressor systems. The consortium developed and tested various polymer and ceramic electrocaloric materials. Additional tests involving components made from other materials are still ongoing to determine the potential for an increase of the coefficient of performance.

The ElKaWe project

In the Fraunhofer flagship project “ElKaWe”, six Fraunhofer Institutes under the direction of Fraunhofer IPM have been working on the development of electrocaloric heat pumps for heating and cooling. Today, heat pumps work almost exclusively based on compressor technology. Electrocaloric heat pumps promise significantly higher efficiency and do not require harmful refrigerants. As part of the project, the scientists developed ceramic and polymer-based electrocaloric materials and worked on an innovative system concept that enables particularly efficient heat dissipation.

Participating Fraunhofer-Institutes:

• Fraunhofer Institute for Physical Measurement Techniques IPM (Project Coordinator)

• Fraunhofer Institute for Electron Beam and Plasma Technology FEP

• Fraunhofer Institute for Applied Solid State Physics IAF

• Fraunhofer Institute for Applied Polymer Research IAP

• Fraunhofer Institute for Ceramic Technologies and Systems IKTS

• Fraunhofer Institute for Structural Durability and System Reliability LB

For more information, visit the Fraunhofer website here.