A comparative study of the Adiabatic Compressed Air Energy Storage (A-CAES) and Pumped Thermal Energy Storage (PTES) systems

With the increasing penetration of renewable energy sources into the power grid, Electrical Energy Storage (EES) systems are receiving more and more attention from the researchers, among which the A-CAES and PTES are very promising ones. Although numerous studies have been carried out for each individual system, a comparative study of A-CAES and PTES from the thermo-economic perspective is still largely absent. Therefore, in this paper, the analytical and numerical models are built for the two energy storage systems, the expressions of system efficiency and energy density are derived for the baseline cases and their sensitivities to different loss parameters and operating parameters are analysed individually. After that, different variants of PTES and A-CAES are introduced and compared, and multi-objective optimizations are carried out for each of them. The results show that the A-CAES usually has higher system efficiency and lower unit storage cost than the PTES, whilst the PTES enjoys higher energy density and more siting freedom than the A-CAES. With non-conventional compressor/expander, working fluid and system pressurization, the PTES can be as cheap as the A-CAES. On the other hand, with an isobaric air reservoir and hybrid TES system, the thermo-economic performance of A-CAES can be further enhanced.