On-sun testing of Miscibility Gap Alloy thermal storage

• Published in: Solar energy 2019-01, Vol.177, p.657-664
• Main Authors: Copus, Mark, Fraser, Benjamin, Reece, Roger, Hands, Stuart, Cuskelly, Dylan, Sugo, Heber, Reed, Samuel, Bradley, James, Post, Alexander, Kisi, Erich
• Format: Article
• Language: English
• Subjects: Alloys; Charging; Concentrated solar power; Cooling; Energy storage; Enthalpy; Heat storage; Latent heat; Metals; Miscibility; Phase change material; Phase transitions; Sensible heat; Solar absorption; Solar energy; Solar radiation; Sun; Temperature; Thermal energy; Thermal storage; Zinc
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2018.11.048

•An MGA thermal storage block was used to directly absorb concentrated sunlight.•Sensible and latent heat storage was demonstrated over a period of hours.•The material was shown to be quite resistant to rapid changes in incident flux.•The thermal conductivity was found to be 55 W/mK.•Integration of solar receiver, storage and heat exchanger appears possible. 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.