Numerical modeling for high temperature solar thermochemical reactor

Solar energy, especially concentrated solar thermal energy, has vast potential to contribute towards a more sustainable and clean energy portfolio. Utilizing solar energy, thermochemical water splitting and energy storage that produce clean fuels and store energy becomes the focus in recent decades. The engineering design of a solar thermochemical reactor requires a functional model to account for heat transfer, species transport, and chemical reaction.;In this work numerical modelings for simulating the solar thermochemical reactor are concentrated. Using a 1-D finite difference method, chemical kinetics of an iron-based water splitting process is extracted based on experimental data from a lab scale reactor for both oxidation and reduction process. Simulations including preheating and oxidation process for a large scale reactor using a 2-D axisymmetric model are carried out. The computational results are compared with the corresponding experimental data. Lattice Boltzmann equation (LBE) method has been employed to perform pore-scale simulation for strontium oxide carbonation reaction using in thermochemical energy storage process. Flow transport properties such as permeability and Forchheimer constant are evaluated based on a scanned tomographical image. Parametric study of strontium oxide carbonation is also performed to investigate the dependency of volumetric heat flow rate on the system parameters. Chapman-Enskog analyses are carried out to show that the momentum equation recovered from gray lattice Boltzmann equation (GLBE) schemes satisfies Brinkman equation. The need for redefining macroscopic velocity and forces are discussed for several GLBE schemes. A comprehensive transient 3-D model based on LBE and GLBE coupling with Monte- Carlo ray tracing (MCRT) method for H2 and CO production in a solar reactor is presented. The predicted solar-to-fuel energy conversion efficiency based on the simulation varies from 5% to 10%. The simulation results also suggest that high temperatures for both reduction and oxidation steps and near-vacuum pressure (~10-4 atm) for thermal reduction are critical for improved solar-to-fuel conversion efficiency with the ceria-based reactive material.