Phenomenological based models and optimal design of low-temperature PEM Fuel Cells [thesis]

Ignacio Schmidhalter
Increasing emissions of atmospheric pollutants and greenhouse gases resulting from the use of conventional fossil fuels in electricity generation and transportation systems generate significant environmental problems with air quality and climate change across the globe. Conventional energy conversion systems, in particular, are one of the planet's major sources of pollution. An alternative energy conversion technology, such as fuel cell technology, provides a cleaner mechanism for minimizing
more » ... usage of traditional energy resources. Moreover, fuel cells are an energy conversion system with higher efficiency and much lower emissions than any other energy conversion device. In particular, low-temperature polymer electrolyte membrane fuel cells (PEMFC) are a promising technology able to use for mobile and stationary applications. In such a sense, a deep understanding of the phenomena taking place within a PEMFC through the phenomenological modelling with an integral-balance approach is of great interest. Simplified analytical solutions for gas and liquid flow and gas composition in the Gas Diffusion Layer (GDL) at the cathode side of low-temperature PEMFC were found. Along the GDL length, gas phase collinear molar flow changes the direction pointing to the channel or to the membrane and hence, dividing the GDL into two regions according to this change. Just at the boundary of these regions, liquid water is found in the portion closer to the membrane giving rise to the determination of a wet region within GDL. Analytical expressions for the gas collinear molar flow and for the species mole fraction were derived for each region. Normalized collinear molar and diffusive gas phase flows as well as condensation and evaporation are analytically computed. Our results show that both collinear molar and diffusive flows play an important role in the fuel cell efficiency, being both of the same orders of magnitude and consequently, solutions neglecting collinear molar flows are not appropriate to understand the mass transport [...]
doi:10.18725/oparu-43946 fatcat:mautjj3pznf75d5ysd3rz47qey