An Improvement in the Solar Water Heating Systems using Phase Change Materials

The present work has been undertaken to study the feasibility of storing solar energy using Phase Change Materials (PCMs) and utilizing this energy to heat water for domestic purposes during nighttime. This ensures that hot water is available through out the day. The system consists of two simultaneously functioning heat-absorbing units. One of them is a solar water heater and the other a heat storage unit consisting of PCM (paraffin). The water heater functions normally and supplies hot water during the day. The storage unit stores the heat in PCMs during the day supplies hot water during the night. The storage unit utilizes small cylinders, made of aluminium, filled with paraffin wax as the heat storage medium. It also consists of a Solar Collector to absorb solar heat. At the start of the day the storage unit is filled with water completely. This water is made to circulate between the heating panel (Solar collector) and the PCMs. The water in the storage unit receives heat form the heating panel and transfers it to the PCM. The PCM undergoes a phase change by absorbing latent heat, excess heat being stored as sensible heat. Using parabolic mirrors accelerates the charging of the tower. The water supply in the night is routed to the storage unit using a suitable control device. The heat is recovered from the unit by passing water at room temp through it. As water is drawn from the storage tower, fresh water enters the unit disturbing the thermal equilibrium, causing flow of heat from PCM to the water. The storage tower is completely insulated to prevent loss of heat. The efficiency of this system is scrutinized for the solar conditions