Designing a Solar Heat Storage System using Heat Pipe and Phase-Change Material (PCM)

Abstract

Phase change material (PCM) is used as a storage medium in a thermal heating system. The PCM's ability to store heat for a long time is suitable for combining with solar energy. PCM can absorb or release large amounts of latent heat at relatively constant temperatures. However, the PCM has poor thermal conductivity. The superconductive heat pipe is suitable to enhance the heat transfer in the PCM. The study aims to prove the concept of a unique thermal storage system that combines solar Fresnel lens, heat pipe, and phase change materials technologies. This study presented a detailed design and testing of the combined system under an actual outdoor environment. Four Fresnel lenses refracted the sunlight and focused on a heat collector. The lenses can be manually adjusted according to the sun's position. The heat is transferred to the PCM storage tank via a finned heat pipe. The testing results showed that the paraffin wax (PCM) has a melting temperature between 54 -59 °C. The highest temperature recorded in the paraffin wax tank was 121 °C which is suitable for many future applications. The system could store the heat up to 730 kJ by using 2 kg of paraffin. During the solidification of PCM (discharging), the system retained 120 kJ of heat for almost 7 hours with minimal heat loss. The system was proven to function well for storing the heat after the sunset, and it can be used for a passive power generation system, such as using thermoelectric cells.