Review on micro/nano phase change materials for solar thermal applications

Solar energy, which is well–known for its inexhaustible and environmentally friendly properties, is among the most promising sources of energy. Solar energy is usually collected by a heat medium–heat transfer fluid (HTF) in the form of heat and is then transported to production and human use. Due to the challenges of variant weather, climate and seasons, solar heating or power supply devices based on thermal energy storage (TES) components that can operate continuously and without interruption are needed. Phase change materials (PCMs) as latent heat storage material have considerably smaller weights and volumes to store larger amount of energy, which can help the solar thermal equipment capture more solar energy. Nevertheless, conventional PCMs with low thermal conductivity (TC) lead to long energy storage/release times for TES components, which significantly reduces the TES efficiency. To improve the overall TES performance, the key is to accelerate the heat storage/release process via boosting the TC of the PCMs. Based on cutting–edge theoretical and experimental studies, we review the typical thermal enhancement advances in micro/nano–PCMs in this field.