Abstract

A novel energy storage system for use in high-temperature CSP systems is described and modelled using a simplified one-dimensional model. The storage makes use of boiling and condensing sodium to convey heat from the receiver to a phase-change material storage composed of melting and freezing sodium chloride salt in trays, with direct contact between salt and sodium. The dynamics of this system are demonstrated, and the exergy efficiency of this energy storage is shown to be greatest for relatively shallow trays of 2 cm depth. The thermal resistance to heat transfer into and out of the PCM results in pressure variations in the sodium vapour space throughout the charging and discharging cycle.