Theoretical analysis of a high-temperature small-particle solar receiver

Abstract

High-temperature solar receivers that use a gas-particle suspension to absorb concentrated sunlight are currently being studied for heating gases, both to drive a turbine for electricity, and to carry out suitable chemical reactions. Although the geometry of such a receiver is far from finalized, as an example one may consider a large chamber filled with the particle suspension and open on one side (with or without a window) to admit the radiation. In order to design and assess the viability of such a receiver, it is necessary to know how the light is absorbed in the mixture and what the resulting temperature profiles are. In this paper the first three-dimensional model for a rectangular receiver is presented. It includes a simultaneous solution of the radiative transfer equation and the energy equation, together with calculations for particle absorption, scattering, and oxidation (for carbon particles in air). For a theoretical 30 MW th receiver, the results show high receiver and receiver + Carnot cycle efficiencies, fairly low dependence on particle size, and large temperature gradients in the receiver when the particles do not oxidize.