(89d) Steady State Modeling and Optimization Studies of a Tubular Proton Exchange Membrane Fuel Cell (PEMFC) Validated with Experimental Studies

A significant reduction in cost is required to make the PEMFC (Proton Exchange Membrane Fuel Cell) technology commercially viable. Several options are being explored for reducing the cost. In this work, a tubular architecture is considered for reducing the cost. The design also significantly improves the power/weight ratio of the cell compared to the commercial planar PEMFCs. It can be mentioned that a significant increase in the power/weight ratio can reduce the parasitic losses in the system especially for automotive applications of the cell.

The tubular cell is designed and manufactured for both air breathing and pressurized cell applications. Commercially available hardware components are used for manufacturing the cells. Testing of the cell is done with a Scribner Associates 850E HT system. The performance of the pressurized cell is found to be better than the state-of-the-art planar PEMFC available commercially. The power/weight ratio of the tubular cell is found to be higher by an order of magnitude than its commercial counterpart. The design also results in a simplification of the complicated flow-field design typically used for enhancing the performance of planar PEMFCs. In addition, the design improves the water management, particularly at a high current density.

A theoretical model of the cell is also developed. In this isothermal half cell model, mass and momentum conservation equations are considered inside the cathode gas flow channel. Mass/species conservation equations are written for the gas diffusion layer and the reaction layer. The reaction layer is characterized as both macro homogenous and spherical agglomerate models. Effects of these characterizations on the model predictions will be presented. In order to reduce the time for computations, the method of Thiele Modulus and effectiveness factor are adopted for the spherical agglomerate characterization. The model of both the air-breathing and the pressurized cells are developed. Both the models are validated by the experimental data collected over a wide range of air flow rate and operating pressure.

A dimensional optimization study is done with the developed steady state model. A nonlinear constrained multiobjective optimization problem is solved to generate the optimum dimensions for the tubular cell that results in an enhanced performance of the cell compared to the base case. The optimized dimensions are used to fabricate a new cell. The performance of the optimized cell in comparison with the base case cell and that of the theoretical prediction will also be presented.