Overview of thermochemical energy storage materials and processes

Due to the global population growth, developing living standards and expectation of comfort levels, energy needs have increased significantly. With the increase in global warming, the need for more heating and cooling has arisen, and in order to meet this need, it is necessary to seek new environmentally friendly technologies that provide sustainable air conditioning. In this context, development of new materials and technologies for thermal energy storage plays a vital role in reducing fossil fuel-based energy use. In the concept thermochemical energy storage (TCES), energy is stored via desorption of water and released by sorption of water (for heating) or reaction with water (for cooling) of the utilized salt. TCES systems could be a more promising alternative compared to sensible and latent heat systems with their advantages such as high energy density, long storage duration and low volume requirement. This study presents an overview with a focus on reaction and sorption-based TCES systems. In particular, the performances of fertilizer-based salts used as TCES materials for cooling applications are emphasised. Additionally composite material development by using porous host matrices for TCES is discussed. Moreover, potential implementation methods of thermochemical based cool thermal energy storage systems are evaluated. Generally, the subject of heating is emphasised in thermochemical heat storage applications, but in this study, potential application methods of thermochemical-based cold thermal energy storage systems are also evaluated. Although some cold thermal storage methods (i.e. ice storage) have been widely researched, studies on TCES for cooling are very limited. Since this method can store cold thermal energy at ambient temperature, it represents a significant potential for solar energy storage for air-conditioning applications. This study could provide important insights on future development of TCES materials and technologies.