Comprehensive performance of building systems using sensible-latent heat composite energy storage structure under all-day solar radiation conditions

In this study, a novel sensible-latent heat composite energy storage structure is constructed by filling the bottom of the phase change material with water. Based on the thermal conductivity of water, the heat transfer and sensible heat storage are enhanced, and the energy storage performance of different material proportions under constant heat flux and solar thermal radiation conditions is explored. The effects of sensible heat material filling height and heat flux of heat source on internal PCM melting process and overall energy storage performance are studied by numerical simulation, and an experimental system is constructed to conduct model reliability analysis. The comprehensive performance improvement of the composite structure under all-day solar radiation conditions in Xi'an summer is further studied. The results show that under constant heat source density (q_const= 1000 W/m²), the melting time of Case 6 structure with 50 % water is 43.04 % lower than that of Case 1 structure with pure paraffin. However, at the end of melting, the sensible and total energy absorption of PCM in Case 6 decreased by 74.67 % and 56.20 %. Comparing the solar thermal radiation conditions from 6:00 to 18:00 on a sunny day in Xi'an for Case 1 and Case 6, the total heat energy obtained by Case 6 after 12 rounds of heat storage throughout the day is increased by 16.12 % compared with Case 1. Although the volume of PCM in Case 6 is reduced by half, the overall energy storage rate is higher.