Phase change materials (PCMs) applications in solar energy systems

The thermal energy storage (TES) is widely used in the industries for waste heat storage, in the cogeneration systems, and for the cooling of electrical devices; however, the integration of TES with the solar systems is most common. Solar energy systems need thermal storage for the off-sun applications and are integrated with TES systems. The major issue with the solar energy is its intermitted nature, being available for daytime only, there are natural fluctuations in the solar flux caused by different environmental factors. The main challenge for the solar power systems is to have a stable output power to maintain energy level between its supply and demands. For such systems, TES system is critically important to reduce the short-term variations and to store heat for the nighttime system operation. The integration of solar systems with the TES is more effective in terms of capital costs and efficiency as compared to other energy storage systems like mechanical or chemical energy storage. Particularly, for solar only devices which completely rely on the solar energy source, a suitable TES system is required for a stable power generation. The latent heat storage system using phase change materials (PCMs) is the more efficient way of the heat storage having advantage on sensible heat storage in terms of high heat storage capacity per unit volume or mass. This chapter aims at giving a complete overview of the thermal storage systems for high-temperature solar systems reported in the literature, describing options concerning CSP plant layouts, providing the theoretical basis for their analytical and numerical modeling, and, finally, showing some relevant applications.