Thermochemical energy storage in barium carbonate enhanced by iron(III) oxide.

Renewable energy requires cost effective and reliable storage to compete with fossil fuels. This study introduces a new reactive carbonate composite (RCC) where FeO is used to thermodynamically destabilise BaCO and reduce its decomposition temperature from 1400 °C to 850 °C, which is more suitable for thermal energy storage applications. FeO is consumed on heating to form BaFeO, which is a stable Fe source for promoting reversible CO reactions. Two reversible reaction steps were observed that corresponded to, first, the reaction between β-BaCO and BaFeO, and second, between γ-BaCO and BaFeO. The thermodynamic parameters were determined to be Δ = 199 ± 6 kJ mol of CO, Δ = 180 ± 6 J K mol of CO and Δ = 212 ± 6 kJ mol of CO, Δ = 185 ± 7 J K mol of CO, respectively, for the two reactions. Due to the low-cost and high gravimetric and volumetric energy density, the RCC is demonstrated to be a promising candidate for next generation thermal energy storage.