Germany's Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) this week presented the results of a four-year study on the performance of various heat pump systems installed in existing residential buildings across the country.
In total, the institute’s researchers analyzed 77 commercially available heat pumps operating in single- to three-family homes, some dating back as far as 1826 and others being finalized in 2001. The buildings represented a mix of fully renovated properties and others still in need of energy-efficiency upgrades.
“The results clearly show that heat pumps can be operated efficiently even in older buildings and that they provide climate-friendly heating without the need for the buildings to be renovated to new construction standards,” said Danny Günther, team leader for ‘Heat Pumps and Transformation of Existing Buildings' at Fraunhofer ISE. “However, we have also uncovered optimization potential.”
The measurements were taken via a least-minute-accurate recording concerning compressors, controls, and heating rods, as well as the hydraulic circuits of the heat source and the heat utilization system, energies, performances, flow rates, and temperature.
The analysis showed that the 77 heat pumps performed better than those examined in a previous Fraunhofer ISE study completed in 2019. In the latest testing, air-to-water heat pumps achieved an average seasonal performance factor (ASPF) of 3.4, compared to 3.1 in the earlier project.
Ground-source heat pumps delivered the highest efficiency, with an average ASPF of 4.3 and values ranging from 3.6 to 5.4. The researchers also found no correlation between the age of the buildings and the heat pumps’ performance.
The team also found that when operated in combination with residential PV systems, heat pumps can deliver significant savings for homeowners.
“The results of the analysis of six heat pump–PV combinations show that, without battery storage, buildings equipped with PV systems achieve 25% to 40% energy autonomy and 22% to 37% self-consumption,” the researchers explained. “When a battery is added, these figures rise considerably — to 32% to 62% for autonomy and 40% to 83% for self-consumption.”
The testing also revealed that many of the heat pumps were oversized relative to the actual heating demand of the households and that some units exhibited “excessively high” switching frequencies.
Major heat pump manufacturers such as Daikin, Viessmann, Panasonic, and Vaillant participated in the project.
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That’s good to read about, however one of the other factors is the amount of space needed for all the equipment when compared to a simple wall hung gas boiler. Many homes do not have a plant room!