A novel beam-down, gravity-fed, solar thermochemical receiver/reactor for direct solid particle decomposition: Design, modeling, and experimentation

Numerical Modeling and Optimization of an Entrained Particle-flow Thermochemical Solar Reactor for Metal Oxide Reduction

“…The model includes heat and mass transfer, chemical reaction, multiphase flow (particles and inert carrier gas flows), and the coupling of these phenomena. The details of the governing equations can be found elsewhere [4,6,10].…”

“…The solid metal zinc can be used in different industrial and automobile applications such as a fuel cell or battery, or in a water-splitting reaction producing hydrogen and regenerating ZnO which can be further recycled to complete the redox cycle [2,8,13,16]. Although ZnO/Zn thermochemical cycle is known for its high process energy efficiency due to high reaction temperature and reduced number of steps, the operating temperature makes challenging the choice of thermally and chemically stable reactor materials and the appropriate reactor design [10]. In order to obtain and withstand high reaction temperatures in the reactor with acceptable efficiency, it is generally necessary to use the cavity-type receiver concept where the effective cavity absorption effect can be increased by focusing concentrated solar energy through an aperture [9,14,17].…”

“…In order to obtain and withstand high reaction temperatures in the reactor with acceptable efficiency, it is generally necessary to use the cavity-type receiver concept where the effective cavity absorption effect can be increased by focusing concentrated solar energy through an aperture [9,14,17]. Cavity-type receiver systems subjected to incoming concentrated sunlight can further be classified as directly or indirectly heated depending on the mode of heat transfer to the reaction site during the endothermic process (direct irradiation of an absorbing particle flow or indirect irradiation via an opaque heat transfer wall) [10,[18][19][20].…”

High Temperature Flow Visualization and Aerodynamic Window Protection of a 100-kWth Solar Thermochemical Receiver-reactor for ZnO Dissociation

“…This is typically achieved by combining tangentially and radially oriented jets of inert gas. The use of a vortex flow to aerodynamically protect a solar reactor window was first proposed by the Weizmann Institute of Science [4], and has since been studied and used extensively in various solar thermochemical applications [5][6][7].…”

“…Previous flow visualization work at room temperature has been useful in identifying the mechanism by which a swirling flow, and the various stages of vortex breakdown that ensue, can be used to aerodynamically protect reactor windows in geometries defined by a frustum region expanding into a reaction cavity [5]. Further, CFD work has been beneficial in confirming that it is possible to fully suppress particle migration to the reactor window [6,7]. However, neither low temperature flow visualization nor computational work has led to conclusions immediately applicable to the high temperature, on-sun reaction environment, as problems with reactor window contamination are consistently encountered in practice.…”