Germany's Fraunhofer ISE is leading a consortium of 20 companies from the heating and housing industries to optimize propane (R290) heat pump systems for existing multi-family homes.
The LC R290 project plans to implement several heat pump pilot projects in residential buildings currently using gas or oil heating, with three conceptual approaches proposed.
Fraunhofer ISE noted that the heating load of the buildings under consideration ranges from 23 kW to 93 kW, requiring a range of heat pumps, including high-output models.
“A particular challenge lies in dealing with the systems for single apartments in which each has their own gas heating system,” the institute said. “Solutions are necessary here predominantly for small apartments in the low-rent segment. These new system solutions should require as little retrofitting and space as possible.”
Image: Fraunhofer ISE
One of the three concepts being developed features a heat pump system with a seasonal coefficient of performance (SCOP) of 3.8, a heating output of 6 kW, and a sink temperature of 55 C.
The second demonstrator is a centrally installed heating system with the heat pump located in the building's basement. It can use heat sources such as geothermal, solar thermal, district heating, air collectors, or a low-temperature heat grid. In the first testing phase, it achieved a SCOP of 3.65, a heating output of 29.5 kW, and a sink temperature of 55 C.
“Optimization calculations suggest that the filling quantity could be reduced to 800 g propane and the SCOP could be increased to 3.7 by implementing optimized control strategies, for example overheating optimization,” said Fraunhofer ISE.
The third pilot project consists of another unspecified type of centrally installed external heat pump for apartment buildings.
“On Fraunhofer ISE’s outdoor performance test field measurements are currently being carried out on the leakage behavior of propane. These results will provide information on how to further increase the safety of propane heat pumps,” said researcher Katharina Morawietz. “Our aim is to keep the amount of propane refrigerant in these type of heat pumps to a minimum.”
Germany's Federal Ministry for Economic Affairs and Climate Protection is funding the two-year research project.
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