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 Fe 2 O 3 is used to thermodynamically destabilise BaCO 3 and reduce its decomposition temperature from 1400 °C to 850 °C, which is more suitable for thermal energy storage applications. Fe 2 O 3 is consumed on heating to form BaFe 12 O 19 , which is a stable Fe source for promoting reversible CO 2 reactions. Two reversible reaction steps were observed that corresponded to, first, the reaction between β-BaCO 3 and BaFe 12 O 19 , and second, between γ-BaCO 3 and BaFe 12 O 19 . The thermodynamic parameters were determined to be Δ H = 199 ± 6 kJ mol -1 of CO 2 , Δ S = 180 ± 6 J K -1 mol -1 of CO 2 and Δ H = 212 ± 6 kJ mol -1 of CO 2 , Δ S = 185 ± 7 J K -1 mol -1 of CO 2 , 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.