Development and experimental investigation of hybrid phase change material thermal energy storage prototype by utilising power-to-heat concept

Abstract

The paper presents experimental research on the hybrid water and phase change material-based thermal energy storage (PCM HTES) prototype. The prototype is designed to apply the concept of power-to-heat, enhance energy storage density by utilising PCM, and be used to prepare domestic hot water (DHW) within the temperature range of 40–65 °C. This design solution was chosen to implement the external arrangement of PCM in a hybrid system and analyse the influence of such geometry on the thermal performance of PCM HTES. Several parameters have been analysed, including the temperature of the water, PCM, and heat exchanger fins, mass flow rate and quantity of DHW, the power and energy consumption of the electric heating element, and thermal energy absorbed and released. The PCM HTES charging experiment is carried out in three charging steps (CS) to compare the thermal performance under different initial conditions. The discharging experiment showed that the prototype could provide 46.0 L of 40 °C mixed water (DHW) for up to 8 min 38 s at a constant mass flow rate of 0.09 kg/s. Overall, experimental results showed the feasibility of the power-to-heat concept in high energy storage density PCM-based TES for DHW systems. However, the results revealed a large inertia and temperature gradient, which led to incomplete melting and solidification of the PCM. The results also indicated important areas for improvement and optimisation of PCM HTES to achieve greater energy efficiency and improved integration with the power-to-heat concept and renewable energy sources.