High temperature thermal storage for solar gas turbines using encapsulated phase change materials

Abstract

The development of high temperature thermal storage systems is required to increase the solar share of solar-hybrid gas turbine cycles. This paper proposes a pressurised packed bed of Encapsulated Phase Change Materials (EPCM) as a thermal storage system for a gas microturbine. Sodium sulphate, with a melting temperature of 884 oC, was identified as a suitable low cost PCM and both macro and micro-encapsulation techniques were analysed. A numerical model of the EPCM concept was developed and used to compare the storage system with sensible heat storage in ceramic media. The results show that the discharge time of EPCM storage is comparable (<10 % improvement) with a packed bed of alumina particles, while the total storage mass is reduced by up to 31%. The decrease in ceramic material costs must be higher than the encapsulation costs for this storage technology to be viable. A preliminary cost analysis is provided for the maximum allowable encapsulating costs.