Experimentally assessed efficiency improvement of innovative 3D-shaped structures as volumetric absorbers

Abstract

Solar tower plants are predicted to take on a significant role in the ongoing global energy transition. The open volumetric air receiver technology can provide an alternative to molten salt receivers due to its proven and effective storage capabilities. The key component of this technology are porous absorber structures which are responsible for the absorption of the solar irradiation. Research of porous structures has consistently shown that 3D-shaped absorber designs offer the highest efficiency potential. The realization of such designs is made possible by newer manufacturing techniques. In this publication, experimental results for two groups of new volumetric absorbers are presented. The StepRec absorber is manufactured via ceramic 3D screen printing, its characteristic step-pin sections allow for deep penetration of the solar irradiation. Additionally, metallic foil absorbers were evaluated, they exhibit particularly high specific surface areas due to low wall thicknesses. The new absorbers were tested for flux densities up to 650kWm2 and air exit temperatures up to 735°C. The experiments successfully confirmed the new absorbers' great potential: They outperformed the HiTRec reference, a ceramic honeycomb structure, for all air temperatures. At 650°C, thermal efficiencies up to 91.8% were recorded, an improvement of 6.5%-points w.r.t. to the HiTRec result.