Optical study of using ceramic foams for volumetric solar receivers

Ceramic foams are promising materials for volumetric solar receivers in concentrated solar power (CSP) plants. Understanding the solar heat flux distribution on the receiver is of great importance for optimizing the receiver volumetric efficiency and thermal performance. This work presents a 3D optical analysis of ceramic based volumetric solar receivers. The optical analysis is conducted using a Monte Carlo based solar ray tracing software. Ceramic foams are represented by idealized packed tetrakaidecahedron structures. The absorbed heat flux distribution and the effect of cell size, porosity and absorptivity on the penetration depth of the absorbed heat flux are investigated. Comparisons have been made with extruded honeycomb receivers. The results clearly demonstrate the dependence of flux distribution and penetration depth of solar rays on the material absorptivity and structure. The simulation results show a uniform heat flux distribution on the frontal faces with an intensity that increases with increasing the material absorptivity. Both the porosity and the cell size have a great effect on the penetration depth of the absorbed heat flux. In general, foam structure shows larger penetration depths than extruded honeycombs.