Effect of a novel cooling window on a recuperated solar-dish Brayton cycle

Abstract

A recuperated solar-dish Brayton cycle using an off-the-shelf turbocharger as a micro-turbine and a rectangular cavity receiver with integrated thermal storage is considered in this study. Due to the high temperatures that these solar receivers operate at, a considerable amount of heat is lost to the environment through the aperture, decreasing the solar-to-mechanical efficiency of the cycle. In this work, the heat losses from the solar receiver were reduced by utilising a novel glass channel on the inside of the cavity receiver, running parallel to the receiver walls and cooled by the working fluid (air) flowing from the compressor. The objective of this conceptual study was to investigate the impact of the novel air-cooled window on the performance of the cycle at steady state. An entropy generation minimisation technique combined with a SolTrace analysis was used. Results showed that the maximum solar-to-mechanical efficiencies were on average between 41% and 45% lower than for the cycle without the window. However, it was found that the exhaust temperature of the cycle with the window was higher. Therefore, a higher energy utilisation factor of between 9% and 11% was found when cogeneration was included.