Mechanical and Civil Engineering Seminar

PhD Thesis Defense

Abstract:

The Industrial Revolution was energized by coal, petroleum and natural gas. It is clear that fossil fuels, which drive steam and electrical engines, made possible a monumental increase in the amount of productive energy available to humans. But in the meantime, the constant burning of fossil fuels has changed the natural greenhouse, intensified global warming, deteriorated air quality and eventually caused irreversible environmental damage on our planet. Renewable energy especially solar energy offers a desirable approach toward meeting our growing energy needs while largely reducing fossil fuel burning. The major problems in terms of harvesting energy directly from sunlight turn out to be low energy concentration and intermittency. Building solar-fuel generators, which stores solar energy in chemical bonds, similar to photosynthesis in nature, provides a possible solution to these two problems. Carbon-free chemicals, such as hydrogen gas, which are produced by solar-driven water-splitting, or carbon-neutral chemicals, such as methane and ethylene, which are produced by solar-driven CO2 reduction, are all promising clean fuels for solar storage.

My thesis is focused on studying the performance and solar to fuel conversion efficiency of existing and hypothetical test-bed photoelectrochemical prototypes using multi-physics modeling and simulation to lay a foundation for future implementation and scale-up of the integrated, solar-driven systems. For water-splitting systems, a sensitivity analysis has been made to assess the relative importance of improvements in electrocatalysts, light absorbers, and system geometry on the efficiency of solar-to-hydrogen generators. Besides, an integrated photoelectrolysis system sustained by water vapor is designed and modeled. Under concentrated sunlight, the performance of the photoelectrochemical system with 10× solar concentrators was simulated and the impact of hydrogen bubbles that are generated inside the cathodic chamber on the performance of the photoelectrolysis system was evaluated. For CO2 reduction systems, operational constraints and strategies for systems to effect the sustainable, solar-driven reduction of atmospheric CO2 were investigated. The spatial and light-intensity dependence of product distributions in an integrated photoelectrochemical CO2 reduction system was modeled and simulated. Finally, the performance a flow-through gas diffusion electrode for electrochemical reduction of CO or CO2 was evaluated.

Please click the link below to join the webinar:

https://caltech.zoom.us/j/89078289682?pwd=dUFVUllEUVdxcTBhMDUxTWx1bGF4Zz09

Passcode: 036562