Energy and economic performance of the heat pump integrated with latent heat thermal energy storage for peak demand shifting

Air-source heat pumps have become a prominent alternative to conventional heaters because of their high efficiency and environmentally friendly features. Coupling the latent heat storage technique with the heat pump allows the operation flexibility to be enhanced, further assisting in demand-side management. This study presents a detailed assessment of the heat pump latent heat storage system for hot water supply from the perspective of storage medium matching and operation strategy evaluation. A simulation platform was developed to demonstrate the application potential of the system, and then a case study for a subtropical residence was formulated. The results revealed that the phase-change material with a melting range of 40–50 °C performed better regarding energy efficiency and cost saving. The unit with a 75 % storage medium operated at the setpoint of 57.5–60 °C noticeably shifted the loads to off-peak periods in wintertime. The energy and economic performance of the system under different operation strategies was compared. Night-heating strategy excelled in flattening peak loads and reducing running costs, while the enhanced-efficiency strategy outperformed in energy conservation. Compared with electric heaters, the system exhibited an average payback period of 7.73 years, achieved a cost saving of HKD 1071.1/year and minimised carbon emissions by 52.5 %.