Dynamic analysis of adiabatic CAES with electric resistance heating

Abstract

Over the past decades, the diabatic configuration of compressed air energy storage (CAES) has been combined with various technologies in literature in order to improve the cycle efficiency. Most often these hybrid concepts have focused on heat recovery by utilizing the excess heat after the final expansion stage. Parallel to the heightened pursuit of environmental targets, the interest towards adiabatic CAES has increased. The main argument behind this paper is that the recuperative approach suitable for diabatic CAES should not be the preferable option for adiabatic CAES. As heat fundamentally is as valuable asset as compressed air, the improvements should aim to increase the value of heat before utilising it. Such improvements have the greatest potential in high-temperature systems, as the thermal energy storage (TES) allows greater variation in the operation conditions. In this paper a hybrid concept previously referred as hybrid-thermal CAES is studied with Apros® dynamic simulation software. Model combining high-temperature molten salt TES and electric resistance heating is set up and the challenges related to the operation are studied. Due to the hybridisation, the electricity otherwise curtailed may be directly stored as thermal energy, which increases the flexibility of the system. The dynamic analysis confirms that both the cycle efficiency and the storage time of the system can be improved. Furthermore, novel possibilities to optimise the system operation and income formation are opened due to interdependent valuation of different inputs for electricity.