Performance evaluation approach for solar heat storage systems using phase change material

Compared to the sensible heat storage, latent heat storage with phase change material offers an alternative approach with higher energy storage density as well as less space requirement, and has been widely used in actual applications in recent years. A performance evaluation approach is necessary to judge whether a system design is feasible. In this study, typical solar latent heat storage systems were described and a performance evaluation approach was proposed. Five design cases including different mass flow rates of heat transfer fluid and solar collecting areas were subsequently evaluated by the proposed method for one example of the typical solar latent storage systems. A 3D numerical model was also established to simulate the transient melting process inside the latent heat storage unit and validated by experiment. The model was used to obtain the transient correlation between the inlet temperature and the outlet temperature of the storage unit. The evaluation results showed that the water mass flow rate has a slight effect on the thermal performance of the solar latent heat storage system while the collecting area has a significant one, and case 1 with the solar collecting area of 2 m2 and the water mass flow rate of 0.028 kg/s showed the best thermal performance among the five designed cases. Based on the investigation of five designed cases, it is concluded that the proposed approach can be used for performance evaluation of the solar latent heat storage systems and assist relevant professionals to optimize the system design.