(567d) PCM-Based Thermal Energy Storage to Enable Cold Climate Operation of R290 Residential Heat Pump

In addition to having good thermodynamic properties, R290 refrigerants are also environmentally friendly (GWP < 3) compared to traditional R-410A (GWP > 2,000). However, due to flammability concerns their charge size is regulated to 150 grams for residential applications, limiting their capacity. This can be overcome by leveraging thermal energy storage solutions. In the experimental investigation, a residential scale R290 heat pump (16 kW) is hydronically coupled with a multi-temp salt-hydrate-based thermal energy storage system (T_m = 30, 40, 60 °C). The multiple temperatures allow for optimized operation to meet space and water heating demands in addition to utilizing the economic benefits of forward capacity and demand flex market. Subsequently, the performance of the heat pump and the HP-TES system is evaluated for different operating conditions. The former set of experiments help characterize the performance and efficiency of the heat pump for different ambient (T_amb = -15 to 40 °C), leaving water temperatures (T_LWT = 7 to 65 °C) and modulation ratios and the latter is used to evaluate the same for the HP-TES system. Using these empirical data, simulation models are built to assess critical cost and efficiency matrices under different operating parameters and weather scenarios to demonstrate and facilitate its adoption for cold climate zones.