The International Energy Agency’s (IEA’s) Annex 58 project has reviewed the current market for high-temperature heat pump systems with supply temperatures greater than 100°C (212°F) and found at least 17 projects in various stages of development using natural refrigerants as the working fluid.

The working fluids being utilized in the various high-temperature heat pump projects include CO2 (R744), water, hydrocarbons, helium, and ammonia/NH3 (R717) in cascade systems.

This information was shared by Consultant Benjamin Zühlsdorf and Senior Specialist Jonas Poulsen of the Danish Technological Institute (DTI) and Postdoctoral Researcher Florian Schlosser from the University of Paderborn in Germany during the third High-Temperature Heat Pump Symposium, which took place in Copenhagen, Denmark, on March 29-30. The symposium was organized by DTI, Technical University of Denmark (DTU), SINTEF and the European Heat Pump Association (EHPA).

Annex 58, a project under the IEA’s Technology Collaboration Programme on Heat Pumping Technologies, looks at technology awareness and development, process integration and market deployment. One of the aims of the project is to provide an overview of heat pump technologies with supply temperatures over 100°C. 

The technology review includes technologies that are at demonstration level, as well as technologies at lower readiness levels, that will enter the market within two to four years. It includes systems with capacities from 0.03 to 70MW (8.5 to 1,990TR), maximum supply temperatures from 100 to 280°C (212 to 536°F) and average specific costs from 200 to 1,500 euro/kW (793 to 5,947 US$/TR).

The Annex 58 project working group has observed some trends in its data gathering. The first is the higher the capacity of the system, the higher supply temperatures the developers are aiming for. A higher capacity also indicates a longer expected lifetime of the system.

Another trend is the strong inverse correlation between the temperature lift and the indicated COP – the smaller the temperature lift, the higher the COP, though this depends on the application.

Companies working on the development of these high-temperature heat pump systems include well-known natural refrigerant manufacturers like Mayekawa, Emerson, Mitsubishi Heavy Industries, MAN Energy Solutions and Fenagy.

The Annex 58 project started in the beginning of 2021 and is expected to conclude by the end of 2023. It includes partners from Austria, Belgium, Canada, Denmark, France, Germany, Japan, the Netherlands, Norway and Switzerland. Partners from the U.K. and U.S. may join at some point. The Danish technological Institute is the lead on the project.

Annex 58 collects the following data for the high-temperature heat pump project: performance data, capacity range, maximum temperatures, type of working fluid, compressor type, specific investment cost, TRL, expected life time, size and footprint.

More information about each of the natural refrigerants high-temperature heat pump projects under development will be published on the project website in May.

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