(681h) Improving Compressed Air Energy Storage Via Indirect Heat Transfer to a Thermochemical Reactor

Compressed Air Energy Storage (CAES) has notoriously low efficiency due to thermal losses from the compressed air. Thermal storage can be incorporated in what is known as ‘Advanced Adiabatic’ or AA-CAES to reduce such losses. Previously, our group has studied a new strategy where thermochemical energy storage (TCES) is used to store the thermal energy of the compressed air prior to storage in the form of chemical energy rather than sensible or latent heat. TCES has higher intrinsic energy density than sensible or latent heat storage, as thus, should be more space efficient and cheaper. In our first study, we looked at using BaO/BaO₂ in direct contact with the compressed air. BaO/BaO2 can reversibly lose and gain oxygen even at extreme pressures as long as the temperature is sufficiently high. Unfortunately, since the heat of reaction and heat capacity of these materials is so low, it did not result in appreciably better performance than sensible heat storage with rocks. In this second study, we examine the potential of coupling TCES with CAES using an indirect configuration where the chemical reaction is carried out in separate space from the air which is being cooled. This allows for a much wider solution space in terms of candidate reactions, as the reactions no longer need to be carried out at the CAES pressures, nor must they involve oxygen. Energy/exergy efficiency, as well as system-level considerations will be presented.