Renewable energy generation is inherently variable. Solar energy shows seasonal (summer–
winter), daily (day–night), and hourly (clouds) variations. Thermal energy storage (TES)
systems correct the mismatch between the solar supply and the demand for thermal energy.
Hence, TES is a key technology for solar thermal energy utilization with growing present and
future importance. This chapter gives a broad overview of different TES materials and technologies.
The text follows the classification commonly adopted in the academic literature. The
three major TES types are sensible (Sec. 2), latent (Sec. 3), and thermochemical (Sec. 4). The
chapter focuses on high-temperature applications in the area of concentrated solar power
(CSP) generation.