Thermodynamics of Ca(OH)2/CaO Reversible Reaction: Refinement of Reaction Equilibrium and Implications for Operation of Chemical Heat Pump

Abstract Thermochemical energy storage system based on Ca(OH)2/CaO reversible reaction can also be operated as a chemical heat pump to boost the temperature of the delivered energy stream. High energy density and potential to achieve a wide range of high delivery temperatures make this system attractive for application in many high temperature industrial processes. A refinement of the equilibrium relationship between pressure and temperature for the reaction is presented in this paper by incorporating temperature dependence of the thermodynamic properties and vapor phase non-ideality. The results show that incorporation of the temperature dependence of enthalpy leads to prediction of higher equilibrium pressures and the non-ideality in vapor phase can become significant at high pressures. Equilibrium relationships of greater accuracy that are based on sound theoretical foundation are highly desired, as they have significant impact on the design and operation of the chemical heat pump/thermochemical energy storage system.