The thermal performance of PCMs in a solar collector-storage unit has been determined to provide the basic design data for house heating and hot water usage. The present solar collector-storage unit consists of three rectangular stainless-steel panels filled with the newly developed heat storage materials [thickened disodium sulfate decahydrate (DSD : $Na_2SO_4\cdot10H_2O$) and sodium acetate trihydrate (SAT : $CH_3COONa·3H_2O$)]. The front surface of the panel is coated with non-grazing black paint to act as a solar absorber.
Melting phenomena of DSD and SAT have been tested in the panels during the domestic heating season (February ~ May). The performance of heat storage considerably depends on ambient temperature, solar radiation, initial temperature and melting temperature of PCM. The latent heat storage performance of DSD has been found to be larger than that of SAT. From the melting performance test, DSD has been found to be a more promising latent heat storage material than SAT in domestic heating season since in case for DSD top 35mm melted on a cold day of February (-5℃) while in case for SAT only top 15mm melted on a sunny day of May (25℃). However, the thermal storage efficiency of solar-collector storage unit increases significantly with the additional heat supply from a flat-plate solar collector having natural convection in a state of closed loop in a collector-storage unit integrated with a flat-plate collector. Consequently, most of the stored SAT in the panel can be melted without auxiliary heat source.
During the heat recovery stage, the recovered heat in the collector-storage unit was measured using the temperature gain in the continuous circulation of water from the variation of water volume of 20 ~ 100 liter in a tank. At the given water inlet temperature and flow rate, the overall heat transfer coefficient has been found to be in the range of 80 ~ 120 W/$m^2$K. The melt thickness has been correlated with the dimensionless temperature, Fourier and Stefan numbers.
