A review on high-temperature thermochemical energy storage based on metal oxides redox cycle

Thermochemical energy storage is a promising technology which helps to address intermittent problems of energy sources in renewable energy technologies, in particular concentrated solar thermal plants. Compared to latent and sensible energy storage which have been extensively studied, thermochemical energy storage is still at its early development stage yet it is featured with a much greater energy storage density and limitless storage duration. Among various thermochemical energy storage technologies, metal oxides redox energy storage inherits a wide range of advantages, for instance, high-temperature operation, using air as both the reactant and heat transfer medium, and simple products separation due to gas-solid reactions. Over the past 40 years, an increasing number of studies on the performance of the metal-oxides-based energy storage systems have been carried out. Therefore, the present review aims to make a detailed summary of that valuable knowledge and experience in this technical area. More specifically, high-temperature redox energy storage systems including pure and mixed metal oxides systems were reviewed. Design characteristics including operating temperature, energy storage density, reversibility, kinetics, economics and reactor selection and development for various types of redox systems were summarized and discussed in details. It should be noted that the current work is limited to metal oxides redox systems using air as the reactant and the applications of metal oxides redox systems in other areas such as chemical looping are not included.