PCM Solar Energy Storage for High-Efficiency Energy Utilization in Buildings

摘要

This study is on the development and characterization of a phase change material (PCM)-based solar energy storage system. The system is capable of simultaneous energy utilization and energy storage so that it can supply energy to a building even when sunshine is not available. Evacuated tube solar collector was used to transfer thermal energy to water circulated by a solar-operated pump. The water flows through a heat exchanger embedded in the phase change material in a storage tank, thus transferring energy to the PCM which changes phase and stores thermal energy. Another pump circulates water through a secondary heat exchanger also embedded in the PCM tank to recover energy from it. The heated water can be diverted to a liquid-to-air heat exchanger by means of a three-way valve. A fan blows air through one of the heat exchangers so that hot air for building heating in addition to hot water for other purposes can be obtained from the system. Solar energy conversion was applied in the system to power all the electrical components. The PCM used is vegetable-based. It is stable, non-toxic, non-flammable, renewable and biodegradable as opposed to chemical-based PCMs that could be toxic. Analytical and experimental studies were performed to investigate the performance of the system leading to useful results and design strategies for high-efficiency building energy utilization. In terms of efficiency, the system performed best during the summer period. However, more than half of the energy absorbed at the solar collector was stored by the system irrespective of the season. Relatively lower heat transfer fluid flow rates produced the best thermal energy storage and recovery.