Development of a High-Temperature Counter-Flow Particle Receiver for Concentrated Solar Power Applications

Abstract

In concentrated solar power (CSP) plants, solar radiation is concentrated onto a solar receiver and absorbed as high-temperature heat in a heat transfer medium. Using a particle-flow as the heat transfer medium allows for outlet temperature exceeding 1000◦C and for simultaneous thermal energy storage by collecting the hot particles downstream in an insulated silo. Con- trolling the residence time of the particles during direct high-flux irradiation is critical because it has a direct effect on their exit temperature. Here, a solar particle receiver is designed to enable controllability of the residence time. It consists of a cavity-receiver containing a vertical ceramic duct through which particles are falling against a counter-current flow of air. A 1D two- phase heat transfer model of the duct is developed to investigate the influence of different solid volume fractions and particle sizes. For a given solid volume fraction, smaller particles enhance heat transfer but at the same time make them more difficult to handle. Ceramic particles ranging between 200 and 300 μm were found to be appropriate for the present design. In order to investigate how effectively the residence time of the particles can be controlled, a facility with transparent test section and a 20 mm × 20 mm cross-sectional area was designed and built that allows the hydrodynamics of the particle-laden flow to be studied with high-speed imaging under room temperature conditions. The facility enables to vary the solid volume fraction inside the duct from 0.1% to 10%. The 1D heat transfer model captures that for a constant solar cavity temperature, the particle outlet temperature decreases as the solid volume fraction increases. For solid volume fractions between 0.1 % and 1 % and a solar cavity temperature of 1527◦C, the model predicts that particle outlet temperatures above 1000◦C can be achieved.