Optimization of the optical particle properties for a high temperature solar particle receiver

Abstract

A non-homogeneous slab of particle dispersion composed of two-layers at high temperature, submitted to a concentrated and collimated solar radiation flux with a reflective receiver back wall is considered as a model of a solar particle receiver. The Radiative Transfer Equation (RTE) is solved using a two-stream method and an appropriate hybrid modified Eddington-delta function approximation. The single particle optical properties are modeled using the Lorenz–Mie theory, the single particle phase function is approximated by the Henyey–Greenstein phase function. A Particle Swarm Optimization (PSO) algorithm is used to optimize the particle radius (0.1μm⩽r≤100μm), the volume fraction (1×10-7⩽fv⩽1×10-4) and the refractive index (2.0⩽n≤4.5 and 0.0001⩽k≤25) of an ideal theoretical material to use in a solar particle receiver. Single- and two-layer receivers with known temperature profiles were optimized to maximize the receiver efficiencies. Spectral selective behavior of the optimized refractive index is discussed with the influence of particle radii and volume fractions. The theoretical ideal optical properties found for the particles have given the maximum efficiency reachable by the studied receivers and have shown that an optimized single-layer receiver will perform as well as a two-layer receiver.