Masters Theses

Date of Award

12-2020

Degree Type

Thesis

Degree Name

Master of Science

Major

Mechanical Engineering

Major Professor

Matthew M. Mench

Committee Members

Doug Aaron, Kivanc Ekici

Abstract

In the face of increasing demand for renewable energy sources to replace fossil fuels, current technologies face the issue of steady energy supply from source to power distribution. As most current renewable energy methods either rely on intermittent natural sources or are geographically bound, they require an energy storage medium. Polymer Electrolyte Water Electrolyzers are a theoretically ideal solution to this demand, but they require some performance improvements in practice to be economically viable. This study analyses the current distribution in such electrolyzers in the aim of gaining insight to improve their performance. The current distribution diagnostic can capture local regions of low performance and offers valuable insight into mass transport phenomena for cells with different flow fields and diffusion media. Two types of flow fields and four different diffusion media were used. The parallel flow field showed better performance under normal operating conditions. The current distributions for the two flow fields showed small variations, though local high spots could be observed around the bends for the triple serpentine flow field. Experiments were carried out with low flow-rates or at mass transport limited conditions. Current distribution data showed a high current towards the inlet and a low current towards the outlet for these cases, indicating gas accumulation towards the cell outlet. Results showed that the thin foil LGDLs were more sensitive to starvation than the baseline titanium felts, indicating that the felt's ability for transport of reactants and products underneath lands can be a reason for improved mass transport. The parallel flow field showed worse performance than the triple serpentine under these conditions, indicating that a low liquid flow rate in the channels could cause bubble accumulation due to slower bubble removal. This work demonstrates the benefit of the current distribution diagnostic technique and offers further insights into mass transport phenomena for different flow fields and diffusion media in a PEWE. As high-performance catalysts undergo innovation, these mass transport phenomena will become increasingly important in commercial systems.

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