The effect of irradiation directional distribution on absorption in volumetric solar receivers

Volumetric solar absorbers are designed to enable the penetration of radiation deep into the absorber in order to improve the efficiency of the energy transfer from incoming radiation to the working fluid. The design of such absorbers is usually based on the irradiation energy flux distribution. We show that the directionalfeatures of the irradiation also affect the absorption characteristics of volumetric absorbers, present criteria for the characterization of directional attributes, and describe a method for their calculation. The significance of the directional data is demonstrated for two types of volumetric absorbers. Receiver design and modeling guidelines are presented.