The application of latent thermal energy storage with heat pumps has been extensively studied in recent years. The combination of phase change heat storage and a heat pump can improve the performance of the heat pump and the utilization of renewable energy; however, further cost reduction and efficiency increase are required. Therefore, this study reviews the progress of heat pumps coupled with solid-liquid phase change materials and summarizes the applicable conditions and characterization methods for phase change materials applied to heat pumps. The optimization approaches for the performance of the heat pump system are summarized, including the selection and improvement of phase change materials, the optimal setting of the heat exchanger, and the dynamic optimization control strategy of the system. The outstanding performance of heat pumps with cascade heat storage in improving the supply-side comfort and utilization rate of renewable energy indicates the broad prospect of cascade heat storage being applied to heat pump energy storage systems. Herein, mixed, non-eutectic phase change materials are proposed as alternative materials for cascade heat storage. Notably, summarizing and developing new methods for adjusting the thermophysical properties of phase change materials for energy storage is necessary for adapting the selection and improvement of phase change materials to the optimization of the thermodynamic cycle of cascade heat storage devices and further improving the heating decarbonization ability of latent heat storage heat pumps.

To improve heat dissipation in the thermal management of batteries for electric vehicles, this study proposes a bionic structure based on shark scales. The design optimizes a phase-change material (PCM) heat sink in conjunction with axial air cooling to regulate battery temperature. Based on performance tests of the battery, a three-dimensional model was built to investigate and compare the heat dissipation of the battery under different conditions, including natural convection, forced convection, forced convection coupled with PCM, and forced convection coupled with bionics-optimized PCM. The results indicate that the temperature rise of the battery with the forced convection coupled with bionics-optimized PCM is only 33.6% of that with natural convection at a 2 C discharge rate, and the average temperature of the battery is 41.8 ℃, which keeps the battery within a suitable temperature range. In addition, the bionic structure can reduce the pressure drop at the inlet and outlet by 4% compared with the traditional method.

Fatty acids as phase change materials (PCMs) are extensively used to alleviate the energy crisis of buildings. The PCM of lauric acid-myristic acid-stearic acid (LA–MA–SA) was synthesized. LA–MA–SA/EG/DE stabilized composite PCMs were synthesized via melting impregnation with an expanded graphite (EG) and a diatomaceous earth (DE). The microstructures and thermal physical properties of the stabilized composite PCMs were determined. The results show that LA–MA–SA is physically adsorbed with EG and DE and has a good adsorption effect. The steady-state tests of thermal conductivity indicate that EG can effectively improve the thermal conductivity of PCM, and the addition of 2%–10% EG can enhance the thermal conductivity by 29.7%–708.2%. The addition of DE can play an active role in shaping for compound and prevents the leakage of PCM. After 100 DSC cycles of the stabilized composite PCM, there is little difference from the phase change temperature and latent heat of the PCMs. According to the results of the heating and cooling tests, the gypsum board of LA–MA–SA/10% EG/10/% DE shows a good heat storage and release performance and a relative thermal comfort time for 0.82 h.