Global energy needs are continuously increasing while fossil fuels remain an uncertain resource. With a growing population and increasing demand for energy, alternative energy is being pursued to power the future. Concentrated solar power (CSP) is a promising method of converting solar energy into electricity and works in conjunction with thermal energy storage (TES) to allow for power generation beyond on-sun hours. One method of TES is thermochemical energy storage (TCES), which is based on storing chemical energy via reversible reactions. An SrO/SrCO3 carbonation cycle offers high temperature heat (ca. 1200 degrees C), leading to higher efficiencies. The carbonation reaction was further investigated to determine the effects of particle size, temperature, partial pressure of CO2, and heat treatment temperature. Unfortunately, high temperatures cause materials to sinter, resulting in a decrease in reactivity over multiple cycles. The use of an inert diluent may help to inhibit sintering by acting as a physical barrier between the particles. Stored energy density of SrO/SrCO3 systems supported by CaSO4 and Sr-3(PO4)(2) was investigated for multiple cycles of 1150 degrees C exothermic carbonation followed by 1235 degrees C decomposition. At 25 and 50 wt%, Sr-3(PO4), stable energy densities of roughly 500 0.05 kJ/kg are achieved. In addition, it was found that the initial moisture content of the material affects performance of the material over several cycles due to a change in particle size. This behavior was thoroughly investigated and is useful for future work in TCES involving carbonation cycles.