List of Titles

Numerical modelling of ceria undergoing reduction in a particle-gas counter-flow: Effects of chemical kinetics under isothermal conditions

- Li, Sha, Wheeler, Vincent, Kumar, Apurv, Lipinski, Wojciech

Authors: Li, Sha , Wheeler, Vincent , Kumar, Apurv , Lipinski, Wojciech
Date: 2020
Type: Text , Journal article
Relation: Chemical Engineering Science Vol. 218, no. (Jun 2020), p. 14
Full Text: false
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Description: A numerical model is employed to simulate a single tube reactor featuring a downward particle flow counter to an upward inert gas flow for ceria reduction in the dilute flow regime. The coupled phenomena of mass and momentum transfer as well as chemical kinetics are simulated assuming isothermal operation for the reactor. The model predicts the reduction extent under varying reaction kinetics as well as design and operational choices. The reduction extent is found to increase with the reaction rate constant until achieving the thermodynamic upper limit at a certain critical value. This critical rate constant signifies a transition from a chemical kinetics limited conversion to a gas advection limited conversion. The effect of the reactor length and the particle size on reaction extent is studied for a range of realistic cases. An empirical correlation is developed to quantify the effects of particle and gas flow rates on reduction extent at both slow and fast kinetics. The present work offers insights to help guide reactor design and operation towards achieving the maximum reduction extent. (C) 2020 Elsevier Ltd. All rights reserved.

Thermodynamic guiding principles for designing nonstoichiometric redox materials for solar thermochemical fuel production : ceria, perovskites, and beyond

- Li, Sha, Wheeler, Vincent, Kumar, Apurv, Venkataraman, Mahesh, Muhich, Chrisopher

Authors: Li, Sha , Wheeler, Vincent , Kumar, Apurv , Venkataraman, Mahesh , Muhich, Chrisopher
Date: 2022
Type: Text , Journal article
Relation: Energy Technology Vol. 10, no. 1 (2022), p.
Full Text: false
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Description: Two-step solar thermochemical water splitting is a promising pathway for renewable fuel production due to its potential for high thermal efficiency via full-spectrum sunlight utilization. Such a promise critically relies on simultaneous innovation in the redox materials and the reactor systems. Most prior efforts on material design are focused on improving the fuel yield at lower reduction temperatures. However, developing materials with both high fuel output and efficiency remains a key challenge, requiring a rigorous understanding of the effects of material thermodynamic properties. Herein, a generic thermodynamic framework is described to decipher the material effects by studying both the state-of-the-art and hypothetical materials within a counterflow reactor system. A global efficiency map is presented for redox materials, revealing inevitable tradeoffs among competing factors such as thermal losses, sweep gas and oxidizer demand, solid preheating, and reduction enthalpy. The choice of the most efficient material is closely linked to the system conditions. Ceria-based materials outperform perovskites under most scenarios, and the optimal hypothetical materials tend to favor higher reduction enthalpies and entropies than existing materials. This work offers a valuable material design roadmap to identify solutions toward efficient solar fuel production. © 2021 Wiley-VCH GmbH. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Apurv Kumar” is provided in this record**

Optical characterisation of alumina–mullite materials for solar particle receiver applications

- Chen, Jiangjing, Wheeler, Vincent, Liu, Boqing, Kumar, Apurv, Coventry, Joe, Lipiński, Wojciech

Authors: Chen, Jiangjing , Wheeler, Vincent , Liu, Boqing , Kumar, Apurv , Coventry, Joe , Lipiński, Wojciech
Date: 2021
Type: Text , Journal article
Relation: Solar Energy Materials and Solar Cells Vol. 230, no. (2021), p.
Full Text: false
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Description: Alumina–mullite particles are used in high-temperature solar thermal applications such as solar particle receivers. In this study, optical properties of alumina–mullite materials with variable content of alumina and mullite are determined in the spectral range of 0.193–1.69 μm. Variable angle spectroscopic ellipsometry is performed for alumina–mullite thin films, which are fabricated by magnetron sputtering. The thin films are characterised by scanning electron microscopy, atomic force microscopy, and energy dispersive spectroscopy methods. The B-spline model is employed to generate ellipsometric parameters to fit the measured data and to obtain the optical properties. The investigated materials of variable content of alumina and mullite have a similar refractive index in the considered spectral range. The absorptive index of the alumina–mullite materials in the spectral range of 0.193–0.4 μm is higher than in the range 0.4–1.69 μm. The absorptive index decreases with increasing content of alumina in the spectral range of 0.193–0.4 μm. The material composed of similar proportions of alumina and mullite yields the highest absorptive index in the spectral range of 0.4–1.1 μm. The optical properties determined for the alumina–mullite materials are applied to obtain the radiative properties of spherical homogeneous particles. Mie theory is used to calculate absorption and scattering efficiency factors, as well as the scattering phase function. In addition, the scattering phase functions are obtained using the Henyey–Greenstein approximation and the transport approximation. The Monte Carlo ray-tracing method is employed to study the radiative transfer in a model one-dimensional particle curtain containing polydisperse particles exposed to high-flux solar irradiation. It is found that the overall reflectance, absorptance and transmittance of the particles only weakly depend on the optical properties of the materials investigated. © 2021 Elsevier B.V. Corrigendum to “Optical characterisation of alumina–mullite materials for solar particle receiver applications” [Solar Energy Mater. Solar Cell. 230 (2021) 111170] (Solar Energy Materials and Solar Cells (2021) 230, (S0927024821002130), (10.1016/j.solmat.2021.111170)) Solar Energy Materials and Solar Cells, Volume 231, October 2021, Article number 111225. https://doi.org/10.1016/j.solmat.2021.111225
Description: Alumina–mullite particles are used in high-temperature solar thermal applications such as solar particle receivers. In this study, optical properties of alumina–mullite materials with variable content of alumina and mullite are determined in the spectral range of 0.193–1.69 μm. Variable angle spectroscopic ellipsometry is performed for alumina–mullite thin films, which are fabricated by magnetron sputtering. The thin films are characterised by scanning electron microscopy, atomic force microscopy, and energy dispersive spectroscopy methods. The B-spline model is employed to generate ellipsometric parameters to fit the measured data and to obtain the optical properties. The investigated materials of variable content of alumina and mullite have a similar refractive index in the considered spectral range. The absorptive index of the alumina–mullite materials in the spectral range of 0.193–0.4 μm is higher than in the range 0.4–1.69 μm. The absorptive index decreases with increasing content of alumina in the spectral range of 0.193–0.4 μm. The material composed of similar proportions of alumina and mullite yields the highest absorptive index in the spectral range of 0.4–1.1 μm. The optical properties determined for the alumina–mullite materials are applied to obtain the radiative properties of spherical homogeneous particles. Mie theory is used to calculate absorption and scattering efficiency factors, as well as the scattering phase function. In addition, the scattering phase functions are obtained using the Henyey–Greenstein approximation and the transport approximation. The Monte Carlo ray-tracing method is employed to study the radiative transfer in a model one-dimensional particle curtain containing polydisperse particles exposed to high-flux solar irradiation. It is found that the overall reflectance, absorptance and transmittance of the particles only weakly depend on the optical properties of the materials investigated. © 2021 Elsevier B.V. Corrigendum to “Optical characterisation of alumina–mullite materials for solar particle receiver applications” [Solar Energy Mater. Solar Cell. 230 (2021) 111170] (Solar Energy Materials and Solar Cells (2021) 230, (S0927024821002130), (10.1016/j.solmat.2021.111170)) Solar Energy Materials and Solar Cells, Volume 231, October 2021, Article number 111225

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