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 Fe2O3 is used to thermodynamically destabilise BaCO3 and reduce its decomposition temperature from 1400 degrees C to 850 degrees C, which is more suitable for thermal energy storage applications. Fe2O3 is consumed on heating to form BaFe12O19, which is a stable Fe source for promoting reversible CO2 reactions. Two reversible reaction steps were observed that corresponded to, first, the reaction between beta-BaCO3 and BaFe12O19, and second, between gamma-BaCO3 and BaFe12O19. The thermodynamic parameters were determined to be Delta H = 199 +/- 6 kJ mol(-1) of CO2, Delta S = 180 +/- 6 J K-1 mol(-1) of CO2 and Delta H = 212 +/- 6 kJ mol(-1) of CO2, Delta S = 185 +/- 7 J K-1 mol(-1) of CO2, 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.