Session: K6-07: Thermal Energy Storage Systems - II

Paper Number: 195116

195116 - Multiphysics Simulation of Redox Behavior in Porous Mgmno Rods for High-Temperature Thermochemical Energy Storage 

Abstract: 

Thermochemical energy storage (TCES) systems offer a promising pathway toward high-density, low-cost heat storage for industrial and grid-scale applications. Among the various materials investigated for reversible redox-based TCES, magnesium–manganese oxide (MgMnO) has recently emerged as one of the most promising candidates due to its high cyclability, favorable energy density, and elevated operating temperatures. Additionally, MgMnO maintains structural integrity without coalescence when used in pelletized or flowing-particle reactor configurations, making it suitable for scalable thermal battery concepts. Prior studies have demonstrated its redox performance in both packed-bed configuration and particle-flow reactors, confirming the viability MgMnO for a variety of systems, ranging from large-scale heat-storage deployment to smaller localized units.

This work presents the development of a multiphysics numerical model to simulate the high-temperature redox behavior of MgMnO under controlled gas-flow conditions. The material is considered in the form of a stationary porous rod subjected to radiant heating. The surrounding gas changes from air to an inert gas (nitrogen or water vapor), depending on the cycle considered. The model couples transient radiative heat transfer, gas–solid diffusion, and temperature-dependent redox kinetics. A finite element framework was implemented in COMSOL Multiphysics to solve the governing equations, which incorporate temperature-dependent thermophysical properties and interfacial reaction rates. Material conductivity, heat capacity, and gas-phase viscosity were implemented as time-dependent functions, enabling prediction of internal temperature gradients and local oxygen concentration profiles throughout the porous medium.

Simulations of the oxidation step were performed at 1000 °C using air as the oxidizing gas, while reductions were simulated at 1500 °C using either nitrogen or water vapor as the sweep gas to remove the oxygen released. The model captures the transient evolution of oxygen concentration, temperature, reaction front propagation, and overall conversion within the MgMnO rod. Distinct oxygen consumption and release signatures were reproduced during cycling, resulting in temporally varying oxygen-partial-pressure profiles consistent with redox progression.

Model predictions were compared with experimental results obtained from high-temperature cycling tests performed on porous MgMnO rods. Validation measurements utilized a controlled gas-flow system, thermocouple-based temperature tracking, and a real-time oxygen analyzer. Simulated and experimental results show strong agreement in terms of oxidation extent, total oxygen uptake and release, and characteristic reaction times. Additional parametric studies quantify the influence of porosity, the pore sizes, and sweep-gas composition on reaction kinetics and storage capacity. Overall, the modeling framework provides a physics-based tool for designing MgMnO-based thermochemical reactors and supports scaling strategies for integrating high-temperature thermal batteries into industrial and grid-level heat-storage systems.

Presenting Author: Farshid Kassaei Michigan State University

Presenting Author Biography: Farshid Kassaei is currently a Ph.D. student of Mechanical Engineering at Michigan State University, specializing in thermochemical energy storage and renewable energy systems. He is currently working on metal oxides as a thermochemical heat storage material.

Authors:

Farshid Kassaei Michigan State University
Andre Benard Michigan State University