Applicability performance evaluation of cascade heat pump for building electrification in winter

This study aimed to evaluate the performance of indoor air heating and domestic hot water supply using a cascade heat pump system. The focus was on using existing heat pump equipment to satisfy system requirements in the context of building retrofitting. The experimental setup was located in nearly net-zero experimental building of the South Korea. The system was configured to heat air in the low-cycle heat pump and supply hot domestic water in the high-cycle heat pump. The study compared three operational modes: a low-cycle-only mode; a hot water-only mode; and a combined mode. While low-cycle-only mode and hot-water-only mode fulfilled the required condition with 3.94–5.38 COP and 60 °C hot water temperature with a flow rate of 15.8 LPM separately, the combined mode failed to reach the target air temperature fulfilling only hot water temperature. In conclusion, the system demonstrated satisfactory performance when heating indoor air and providing hot water separately. However, the indoor heating performance declined when both functions were operated simultaneously. To address this issue, possible solutions could include revising the system operation logic to better align with heating and domestic hot water usage schedules or altering the refrigerant flow path. •Performance of cascade heat pump was evaluated for indoor air and water heating.•Field test was conducted by manufacturing and installing system in building.•System performance was compared with separated operation mode.•Air and water heating mode showed an improvement compared to the hot water-only mode.•Operating and refrigerant flow path could be adjusted for air heating performance.