Energy and exergy analyses of a solar magnesium-chlorine thermochemical plant for methane production

Abstract

Solar power as the most available type of renewable energy can be used as a clean driving source in the thermal systems. One of the ways to overcome the intermittency problem of solar energy is to convert it into a chemical that can be used whenever it is required. Hydrogen is a good candidate for using it as a fuel. Thermochemical methods for the production of hydrogen are considered as promising candidates. magnesium-chlorine (Mg-Cl) thermochemical cycle is one of the water-splitting cycles that can be used to produce hydrogen. Due to the problems related to storing hydrogen, it is more convenient if we convert it into another chemical like methane. A novel integrated system has been proposed in this study for the production of methane through the Mg-Cl thermochemical cycle. For the base case, hydrogen can be produced with a mass flow rate of 188.32 kg/h. Energy and exergy efficiencies of the Mg-Cl cycle are calculated as 26.25% and 59.88%, respectively. If the produced hydrogen is converted into methane, the methane production capacity of the plant would be 352.98 kg/h. Our results indicated that the energy and exergy efficiencies of the overall system are 7.04% and 60.28%, respectively.