Effect of thermal storage and heat exchanger on compressed air energy storage systems

Since thermal storage and heat exchanger (TSHE) technology plays an important role in advanced compressed air energy storage (CAES) systems, this chapter will introduce the TSHE technology in detail and its influence on advanced CAES systems. It is pointed out that TSHE technology is originally used for recovering the compression heat to achieve high system efficiency of CAES systems, then cold storage and recovery technology is introduced in liquid air energy storage systems to further improve the system efficiency significantly. In addition, TSHE technology can also serve as a link between CAES other energy technologies when they are coupled with each other. The main TSHE technologies currentlyusedinCAES are summarizedandcompared, whichincludedouble-tank indirect TSHE, packed-bed direct TSHE, and packed-bed indirect TSHE. Different TSHE technologies can also be combined for better performance. The mathematical models for the heat exchanger, thermal storage tank and packed-bed thermal storage device are introduced, including a thermodynamic model of design point, off-design models and dynamic models. The influence of thermodynamic parameters and dynamic characteristics of TSHE on system performance is summarized. It is found that the variation of system efficiency with the change of one parameter is subject to other parameters, and the trend is not unique. In addition, the dynamic characteristics of packed-bed thermal storage alsohave a significant impactonthe systemperformance, but the systemefficiency tends to be stable after several cycles. Finally, the coupling technologies of CAES with wind energy, solar energy, organic Rankine cycle (ORC) and combined heat and power (CHP) with the aid of TSHE technology are summarized. The research shows that these couplings can improve the utilization of renewable energy, increase the power output of CAES, make more full use of the heat, or improve the system efficiency.