Review of solar water heaters incorporating solid-liquid organic phase change materials as thermal storage

Highlights: • Thermal and light absorption properties of composite PCMs are reviewed. • Research gap that limits the practical application of PCMs in SWH is discussed. • Types of PCM and their performance in SWH are reviewed. • Recent development in the designs of SWHs incorporating PCMs as TES is reviewed. • Recommendation on tank design is included to optimize performance of SWH. - Abstract: Solar water heater (SWH) incorporating solid-liquid organic phase change materials as thermal energy storage (TES) have attracted attention since 1970s. However, the development of these PCMs to practical application had been restricted by its low thermal stability and thermal conductivity. Recently many type of composite solid-liquid organic PCMs had been developed and studied to overcome these problems. The effect of polymer/porous materials composition, nanoparticles loading and photo-absorption properties of photothermal energy conversion material on the thermal stability, thermal conductivity and light absorption of composite PCMs are reviewed and analyzed. Besides, practical application of PCMs in SWHs are reviewed and compared as well. Research gaps for future development and application of composite PCMs had been identified and discussed as well.