Bio-inspired flow fields for pem fuel cells- decoupling pressure and distribution effects on performance and identifying design opportunities

The performance of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) is significantly impacted by flow distributor geometry. The effects of flow distributor geometry on PEMFCs was explored in two ways in this study. Firstly, the relative effects of pressure and distribution characteristics of different flow fields on fuel cell unit and system level performance were considered. A method of decoupling these effects was proposed and demonstrated by application to the traditional serpentine and parallel flow field designs.The performance of these two designs were modeled computationally and it was shown that, of the 17% better performance of the serpentine design, 12% was due to mass transport effects, while 5% was due to the effect of increased pressure loss. Secondly, the idea of Bio-Inspired design for creating new fuel cell flow field geometries was investigated to determine the window of opportunity in fuel cell applications for gaining maximum benefit from bio design. It was determined that the area of opportunity for bio design was when having a minimal pressure loss across the flow field was a dominate design constraint. A set of design principles for creating bio flow fields under this design constraint was developed. These principles were then demonstrated by creating an example bio flow field, and simulating its performance computationally, along with that of the traditional parallel design as a reference. The bio design was shown to have lower pressure losses which allowed it to produce 2-3 times better power output per pumping power input than the parallel design, while also maintaining better reactant distribution. Lastly, a new method of determining operating conditions when using low humidity supply gas was developed to help alleviate water management issues. This method, which has been termed Water Balanced operation, was tested on both the bio and parallel design, and was shown to improve performance in both cases --Abstract, page iv