02/17/2022
By Sokny Long

The Francis College of Engineering, Department of Mechanical Engineering, invites you to attend a doctoral dissertation defense by Rasool Elahi on "Computational Modeling of Solar-Enhanced Microwave Plasma Decomposition of Carbon Dioxide.”

Ph.D. Candidate: Rasool Elahi
Date: Tuesday, March 1, 2022
Time: 10 to 11:30 a.m. EST
Location: This will be a virtual defense via Zoom. Those interested in attending should contact Rasool_elahi@student.uml.edu and committee advisor, Juan_Trelles@uml.edu, at least 24 hours prior to the defense to request access to the meeting.

Committee Chair (Advisor): Prof. Juan Pablo Trelles, Associate Professor, Mechanical Engineering, University of Massachusetts Lowell

Committee Members:

  • Prof. Ofer Cohen, Assistant Professor, Department of Physics, University of Massachusetts Lowell
  • Prof. His-Wu Wong, Associate Professor, Department of Chemical Engineering, University of Massachusetts Lowell
  • Prof. Hunter Mack, Associate Professor, Department of Mechanical Engineering, University of Massachusetts Lowell

Brief Abstract:
The use of renewable energy to convert carbon dioxide (CO2) into higher-value products can help meet the demand for fuels and chemicals while reducing CO2 emissions. Solar-Enhanced Microwave Plasma (SEMP) CO2 conversion aims to combine the advantages of solar thermochemical methods (direct use of the most abundant form of renewable energy) and plasmachemical approaches (high efficiency and continuous operation). SEMP exploits the greater absorption of solar photons by CO2 in low-temperature plasma Non-Local Thermodynamic-Equilibrium (NLTE) state, in which the temperature of free electrons is significantly greater than that of the heavy-species (molecules, atoms, ions), compared to CO2 in LTE state. This doctoral dissertation research focuses on understanding and quantifying the interaction between microwave plasma and concentrated solar radiation in a specific SEMP implementation. As a first step towards evaluating the potential of SEMP CO2 conversion, the absorption of solar energy by a plasma-enhanced solar reactor is analyzed via zero- and one-dimensional models. The models are comprised by the spectral radiative transfer equation (RTE) and energy conservation equations for electrons and heavy-species. Simulation results for a representative solar-plasma reactor show up to 48% and 90% net-absorption of solar radiation by CO2 in NLTE at electron temperatures of 1 and 2 eV, respectively, and heavy-species temperatures of ~ 2000 K, common in solar thermochemical processes. In contrast, less than 0.2% of solar radiation is absorbed by CO2 in LTE under similar conditions. Subsequently, A computational study of a built SEMP reactor operating with up to 900 W of microwave power together with up to 525 W of incident solar power, and an Ar-CO2 mixture at atmospheric pressure is presented. The study is based on a fully-coupled 2D computational model comprising the description of fluid flow, heat transfer, energy conservation for electrons and heavy-species, radiative transport in participating media, and Ar-CO2 chemical kinetics through the discharge tube, together with the description of the microwave electromagnetic field through the waveguide and the discharge tube. Numerical simulations reveal that the plasma is concentrated near the location of incident microwave energy, which is aligned with the radiation focal point, and that CO2 decomposition is highest in that region. The incident solar radiation flux leads to more uniform distributions of heavy-species and moderately greater temperatures throughout most of the discharge tube. Modelling results show that, at 700 W of electric power, conversion efficiency increases from 6.4% to 9.8% with increasing solar power from 0 to 525 W, in good agreement with experimental findings. The enhanced process performance appears to be the consequence of the greater power density of the microwave plasma due to solar radiation absorption.

All interested students and faculty members are invited to attend the online defense via remote access.