Theoretical and Experimental Investigations Regarding Open Volumetric Receivers of CRS

Abstract Concentrated sunlight is absorbed in solar thermal power plants by heat resistant absorbers and converted into usable heat which is transferred to a carrier medium. In solar tower power plants such as the plant in Julich porous absorbers can reach temperatures up to 1000 °C and higher. At this power plant air as heat transfer medium is sucked in through the absorber and heated up to about 700 °C. The absorber is composed of highly porous ceramic or metal wire structures. The SIJ investigates the optimization of solar absorption and the convective heat transfer to the air using thermo and fluid mechanical calculations. In such simulations the key quantities are the penetration depth of solar radiation κ and the volumetric heat transfer coefficient α v , which indicates how much energy - depending on the volume and temperature difference - is transferred by convection between solid and fluid. The attenuation of the radiation into the depth of the absorber is described generally by an exponential function with parameter κ . This is accompanied by heat transfer to the structure. Existing models of the key quantities have been validated by experimental data.