A thermodynamic model for comparing thermal energy storage system to electrochemical, chemical, and mechanical energy storage technologies

Abstract

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.

This paper presents a novel methodology for comparing thermal energy storage to electrochemical, chemical, and mechanical energy storage technologies. The machination of this model is hinged on the development of a round trip efficiency formulation for these systems. The charging and discharging processes of compressed air energy storage, flywheel energy storage, fuel cells, and batteries are well understood and defined from a physics standpoint in the context of comparing these systems. However, the challenge lays in comparing the charging process of these systems with the charging process of thermal energy storage systems for concentrating solar power plants (CSP). The source of energy for all these systems is electrical energy except for the CSP plant where the input is thermal energy. In essence, the round trip efficiency for all these systems should be in the form of the ratio of electrical output to electrical input. This paper also presents the thermodynamic modelling equations including the estimation of losses for a CSP plant specifically in terms of the receiver, heat exchanger, storage system, and power block. The round trip efficiency and the levelized cost of energy (LCOE) are the metrics used for comparison purposes. The results from the modelling are compared with solar power plants in operation and literature. The crux of this modelling can be regarded as a platform for the generation of a thermal energy storage roadmap cocooned in a comprehensive energy storage roadmap from a system of systems perspective.