- In this work, a hybrid thermochemistry compressed air energy storage (CAES) system is investigated. Following a review on chemical reactions investigated for use in thermochemical energy storage (TCES) systems, from these chemistries, the conversion of magnesium carbonate, MgCO3, to magnesium oxide, MgO, and carbon dioxide, CO2, was further analyzed for use in an indirect heat transfer system in conjunction with CAES. A mathematical model was constructed to simulate a steady-state CAES and chemical reactor system which uses hydrostatic compensation technology developed by Hydrostor Inc. to maintain constant pressure throughout operation. The model consists of the following components: 1) compressors; 2) a chemical reactor; 3) a packed bed for sensible heat storage (SHS); and 4) a turbine to generate power. The model indicates the advantages of using TCES appear during long storage durations and when the SHS wall overall heat transfer coefficient is increased. Energy remains trapped in the chemical bonds of the TCES material, whereas it can be lost to the surrounding environment when using SHS. For short storage periods where SHS can be well-insulated, the costs of using TCES will likely outweigh any benefits.