Performance assessment method for air-to-air heat pumps: onfield implementation and hardware-in-the-loop testing
Due to their high efficiency, heat pumps (HP) are a key technology as part of the necessary decarbonisation of the building sector. Evaluation of their real performances is thus crucial to guarantee their efficiency. Real performances depend on many factors that cannot always be predicted, making in-situ measurement necessary for each installation. However, for air-to-air HP, measuring accurately the real heating capacity is not easy, since measuring the air enthalpy and mass flow rate is challenging. In that context, several thesis projects have led to the development of a HP performance assessment method. It is a non-intrusive internal method based on the compressor energy balance. It can calculate the coefficient of performance (COP) for different types of HP, including air-to-air systems, thanks to real-time measurements, without interfering with normal operation of the system. In this study, a first on-field implementation, on a monosplit air-to-air heat pump, is presented. Complementary results, obtained from laboratory tests, are then presented, allowing the validation of the method under real operating conditions. The first part of the paper presents the principle and the necessary instrumentation of the performance assessment method. The second part details its implementation on a real installation in a meeting room of an office building in the Paris area. The same HP is also tested in a controlled environment using a hardware-in-the-loop set-up in the EDF R&D laboratory, in which real weather conditions are reproduced, and additional reference measurements are performed. Finally, the results, in terms of HP behaviour and performances, are presented and discussed, highlighting the relevance of this in-situ approach for reliable performance assessment.