Chemical looping based utility-scale energy storage

Recent developments in renewable energy have highlighted the need for energy storage at utility or grid-scale. Currently, the energy storage at this scale is mainly realised by pumped hydro storage, compressed air energy storage, flywheel, and batteries. However, these technologies suffer from one or more significant disadvantages, such as geographical constraints, high capital costs, poor scalability, and negative environmental impacts. An alternative solution for achieving utility-scale energy storage is to adopt a chemical looping approach and store energy in thermochemical form. The chemical looping energy storage approach has no geographical limitations, is of low to medium costs and medium to high energy storage density, can be easily scaled up and has negligible environmental impacts. A wide range of material candidates has been examined for chemical looping energy storage. Among these candidates, BaO2/BaO, Co3O4/CoO, Mn2O3/Mn3O4, CuO/Cu2O, and Fe2O3/Fe3O4 have attracted the most research attention. This is primarily because of their excellent performance over a range of operational temperatures, high energy storage density, and low material costs. Nevertheless, most of the previous research on chemical looping energy storage focused on the characterisation of materials. Consequently, the utility-scale performance of chemical looping energy storage from a process point of view remains unexplored. This, in turn, hinders further development and commercial deployment of this promising energy storage technology. To address the above capability gap, this thesis aims to investigate and assess the effectiveness of the chemical looping concept for the utility-scale energy storage from a process perspective. The energy storage performance of these systems is mainly characterised by round-trip efficiency, energy storage density, exergy efficiency, oxygen production, and economic feasibility. In this research, modelling, experiment, and economic analysis were employed. Specifically, the modelling work was carried using the simulation package Aspen Plus and the experiments were mainly conducted using thermogravimetric analysis (TGA). In terms of the economic assessment, a life-time cost method was applied to calculate the levelised cost of electricity and net present value.