Experimental Investigation on Solar Water Heater Integrated with Thermal Battery Using Phase Change Material and Porous Media

Evacuated tube heat pipe solar collector as a passive solar water heating system is a simple, reliable, and cost-effective way to capture the sun’s thermal energy to supply hot water to homes. In the proposed system, the manifold is reshaped to a tank and filled with phase change materials (PCM) and porous media, which the PCM acts as a latent heat thermal energy storage medium. In order to increase the heat flux from the heat pipe to the PCM and overcome the low thermal conductivity of the PCM, porous media is used. The porous media is connected to the heat pipe condenser to collect the heat and distribute it uniformly throughout the PCM filling the pores. This design of the manifold acts as a heat storage tank or thermal battery. Another pipe in the tank transfers heat from the PCM to the water. Experiments were conducted in 2 modes: charging/discharging and periodic draw-off. The results demonstrated that this thermal battery design could provide homes with the hot water they require on sunny days, while it needs an auxiliary heater or larger solar collector to provide enough hot water on rainy/cloudy days. Considering the solar radiation fluctuation, the efficiency of the thermal battery is 50% ± 9.3%. The thermal battery can warm up the cold water higher than the operating temperature on a sunny day (more than 120 L per day at 38 °C). Using porous media provides better heat distribution in the PCM.