Dense Wire Mesh as a High-Efficiency Solar Volumetric Absorber

Abstract

Heating a gas to over 1,000°C with concentrated sunlight can enable advanced high-performance applications such as solar-driven combined cycles and solar thermo-chemical processes. Solar receivers using volumetric porous absorbers are intended to produce the ‘volumetric effect’ leading to reduced heat loss and high absorber efficiency. However, experiments on volumetric absorbers have not shown this effect, and the absorbers’ efficiency is usually in the range of 70–80% rather than the desirable range of over 90%. Several porous structure geometries, including the well-known ceramic honeycomb and ceramic foam, were investigated with a numerical model. The results show that even optimal configurations still fall short of the desired range of absorber efficiency. A new candidate structure, a dense wire mesh, was investigated and compared to the conventional absorbers. The volumetric convection coefficient was also measured experimentally to provide validation of the single report found in the literature for this structure. An attractive solution with high efficiency of 90% was found for a dense wire mesh with pore diameter of 1 mm and porosity of 0.83. This geometry seems then a promising candidate for future volumetric absorbers.