Model based performance prediction of variable-speed heat pumps – an option to reduce certification costs?
Heat pumps are essential for decarbonizing the heating sector, particularly air-water heat pumps, which are favored for their low costs and ease of installation. In case of unrefurbished existing buildings, hybrid heat pumps – combining heat pump and gas boilers – offer the possibility to decouple the replacement of the heating system from further renovation measures to the building envelope. For tailoring the heat pump capacity to the building demand, manufacturers offer different variants with different nominal capacities that are based on similar hardware, but certification costs quickly add up if each different combination of heat pump and boiler needs to be measured. To this end, we evaluate the possibility of using standard test data for monoenergetic electric heat pumps to derive operation points required by EN14825 for different hybrid heat pump capacities. To achieve this, we present and evaluate a semi-analytical heat pump model. The model predicts the efficiency (COP) and heat flow rates across various ambient conditions and operating points. When developing the model, care was taken to achieve a good match between measurement and prediction using a minimum of parameters. As a result, the model requires a small experimental dataset of 9 laboratory measurements and only 5 input parameters to fit 5 unknown parameters. Using 50 performance measurements of five commercial machines tested in a certified laboratory, the prediction quality is evaluated and benchmarked against an innovative Machine Learning method. Initial results indicate that the model can predict COP with an average error margin of 6.6% for norm measurements, and SCOP with a maximum error of 9.2%. The predicted values do not alter the efficiency class of the machines according to the Ecodesign regulation (EU 813/2013).