Management of compressed air expansion dynamics in piston expander by pressure and heat impingement

Abstract Scientists and engineers recognise the main disadvantage of microscale compressed air energy storage (CAES) installations as their low round-trip storage efficiency. This is attributed to the unstable generation of electrical energy, associated with pressure fluctuations during the discharge of the air tank, and the exothermic and endothermic nature of the compression and expansion processes. Here, we focus on operational processes where Hutchinson’s theory of impinging pressure feeding the piston expander and Steinfeld’s experiments on thermal energy storage will be implemented. Hutchinson’s theory involves air wave impinging on a cylinder, transporting energy and momentum that are converted into the motion of the piston. Control of the heat input is crucial to increase the thermodynamic efficiency of the gas expansion process in the expander, involving the selection of the input location and method to achieve a process as close to isothermal as possible. The essence of this approach lies in selecting a compressed air expansion and heat injection strategy to be pulsed, intermittent, or continuous to achieve the highest possible expander efficiency. Computer simulations showed that with proper heat management efficiency can increase by 0.12.