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.
