On-sun testing of miscibility gap alloy thermal storage

The ability of a C-Zn Miscibility Gap Alloy (MGA) material to operate as a combined solar receiver and storage was investigated. MGA thermal energy storage materials comprise metallic PCM particles embedded within a conducting metal or semi-metal matrix to form a macroscopically solid combined latent heat/sensible heat storage material. A receiver containing 4 × 1L MGA storage modules was mounted on a solar concentrating dish. The storage material was directly illuminated by concentrated solar radiation at a flux of approximately 105 kW/m², readily attaining surface temperatures of 520–530 °C, well above the phase change temperature of 420 °C. Single step charging led to a state of charge of 80% without exceeding a nominal surface temperature of 530 °C. Cycling on and off sun in the range 460–520 °C was used to achieve a state of 99% charged. Thermal performance of the MGA during solar charging and its discharge by natural cooling is presented and analysed.