A new system has set an efficiency record for propane-based heat pumps, reducing the amount of propane needed to operate them. While heat pumps are an effective way to heat or cool buildings, the refrigerants they use are often harmful to the environment. Propane is a more climate-friendly alternative, but its high flammability has prevented its widespread use in heat pumps. A consortium of heat pump manufacturers and scientists from the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) is working on a research project called LC150 to develop heat pumps that can operate efficiently with minimal amounts of propane.
Since October 2021, the researchers at Fraunhofer ISE have been testing different prototypes for ground-source heat pumps, with components such as evaporators, compressors, condensers, heat exchangers, and expansion valves tested in various configurations for two weeks of continuous operation. The best prototype achieved an efficiency record for propane-based heat pumps, requiring only 124 grams of propane for a heating capacity of 12.8 kilowatts, or about 10 grams of refrigerant per kilowatt. This is significantly less than the 60 grams of propane per kilowatt required by conventional heat pumps.
While the record-breaking heat pump is not yet market-ready, the industrial partners are already working on solutions to make it suitable for long-term use. The project team is also exploring other ways to reduce the amount of propane needed, such as using short pipe lengths and small heat exchanger volumes to minimize the internal volume of the heat pump. The goal is to develop a propane-based heat pump with a cooling capacity of 8 to 10 kilowatts and a maximum of 150 grams of propane, which can be used under real-world conditions.
