Experimental assessment of a PCM-based heat pump water heater under EN 16147 domestic-hot-water test conditions

This paper presents, to the authors’ knowledge, the first systematic TRL 6 technology assessment of a novel phase-change-material-based heat pump water heater (PCM-HPWH) using R290 as refrigerant. The complete system prototype was tested in accordance with EN 16147, including continuous draw-off tests, standardized 24 h load profiles, off-peak operation, and standing-loss measurements, thereby demonstrating the domestic-hot-water performance of this emerging concept under realistic operating conditions. Unlike conventional HPWHs, the investigated prototype uses PCM integrated into densely finned aluminum flat multi-port extrusion (MPE) tube heat exchangers. The prototype passed the EN 16147 test for load profile L and provided sufficient storage capacity for load profile M in off-peak operation. However, the charging and discharging behavior of the PCM storage differed markedly from conventional water tanks, with the useful mixed-water volume strongly depending on draw-off rate, frequency, and pause duration. These results show that PCM-based HPWHs can meet standardized domestic-hot-water requirements, but that their usable storage capacity is highly sensitive to transient draw-off conditions. Consequently, while EN 16147 is useful for characterizing realistic use cases, its performance indicators are not fully suited for direct comparison with conventional water-based storage tanks.