Thermal modelling of a solar thermochemical reactor for metal oxide reduction

Metal-oxide redox cycling holds potential as a high-temperature, energy-dense storage strategy for off-sun operation of solar thermal power plants. The reactor enabling the reduction process is a key component that interfaces concentrated solar flux and a solid-gas reacting system. A transient heat transfer model is developed to study the thermal performance of a 2.4 kWth, fluidized bed, laboratory-scale reduction reactor operating at temperatures up to 1800 K. The Monte Carlo ray-tracing method is employed to model radiative transfer from a diffuse light source to the reactor cavity and thermal emission from the heated reactor surfaces. The finite volume method is employed along with the explicit Euler scheme to solve an unsteady energy equation in the reactor tube and walls. The model is used to predict temperature distributions, the start-up time, and the energy efficiency for the proposed reactor concept. An estimate of the chemical conversion rate is also provided.