heat pump field tests, seasonal performance factors, annual coefficient of performance, domestic hot water, state of the art
carried out by the Heat Pump Test Center (WPZ) in Buchs SG, Switzerland. In the current study, heat pumps for hydronic heating systems in single family houses within Switzerland have been investigated since 2016. So far, over 20 air-source and geothermal heat pumps have been added to this governmental quality assurance program (Swiss Federal authority EnergieSchweiz). For each heat pump system, more than 40 measured variables are recorded at a time interval of 10 s with calibrated sensors with very low measurement uncertainty. The aim of this field study is to record the real heat pump system efficiency in operation and to draw comparisons with characteristic values from laboratory measurements and manufacturer data. The study presented, is divided into two parts. The first part that is entitled “Technology, Methods and State of the Art of the field studies” focuses on the procedure, system boundaries and measuring technology of past and current field studies at WPZ Buchs and provides an insight to the state of the art of field performance measurements of domestic heat pumps carried out in Switzerland. The second part is entitled “Results, Analysis and Optimization of current field studies” and concentrates on various measured figures and the improvement potential of the investigated heat pump systems. Compared to the former studies made in the 1990s and early 2000s, the measurement methodology and data acquisition have changed considerably to date. Nowadays, thanks to digitalization, much more data is available. Short sampling intervals are used to describe temporal processes in heat pump systems in detail, enabling an easier detection of defects such as heat losses and unwanted circulation. Thanks to carefully defined system boundaries like JAZ, WNG and SNG heat pump systems can be compared and optimized effectively. Great importance is attached to the measurement of temperature because of its major influence on the overall uncertainty. Therefore, temperature is measured with an uncertainty of ±0.1 K/±0.02 K (absolute/relative) using directly immersed PT-100 sensors and four wire technology. Together with the prior calibration of the whole measuring equipment in the laboratory, an overall uncertainty of the target values (COP, JAZ) of 10% was achieved.