In-Su Han

Development of a 25kW-Class PEM Fuel Cell System for the Propulsion of a Leisure Boat

A 25kW-class polymer electrolyte membrane (PEM) fuel cell system has been developed for the propulsion of a leisure boat. The fuel cell system was designed to satisfy various performance requirements, such as resistance to shock, stability under rolling and pitching oscillations, and durability under salinity condition, for its marine applications. Then, the major components including a 30kW-class PEM fuel cell stack, a DC-DC converter, a seawater cooling system, secondary battery packs, and balance of plants were developed for the fuel cell system. The PEM fuel cell stack employs a unique design structure called an anodic cascade-type stack design in which the anodic cells are divided into several blocks to maximize the fuel utilization without hydrogen recirculation devices. The performance evaluation results showed that the stack generated a maximum power of 31.0kW while maintaining a higher fuel utilization of 99.5% and an electrical efficiency of 56.1%. Combining the 30-kW stack with other components, the 25kW-class fuel cell system boat was fabricated for a leisure. As a result of testing, the fuel cell system reached an electrical efficiency of 48.0% at the maximum power of 25.6kW with stable operability. In the near future, two PEM fuel cell systems will be installed in a 20-m long leisure boat to supply electrical power up to 50kW for propelling the boat and for powering the auxiliary equipments.

Optimal Sizing of the Manifolds in a PEM Fuel Cell Stack using Three-Dimensional CFD Simulations

Polymer electrolyte membrane (PEM) fuel cell stacks are constructed by stacking several to hundreds of unit cells depending on their power outputs required. Fuel and oxidant are distributed to each cell of a stack through so-called manifolds during its operation. In designing a stack, if the manifold sizes are too small, the fuel and oxidant would be maldistributed among the cells. On the contrary, the volume of the stack would be too large if the manifolds are oversized. In this study, we present a three-dimensional computational fluid dynamics (CFD) model with a geometrically simplified flow-field to optimize the size of the manifolds of a stack. The flow-field of the stack was simplified as a straight channel filled with porous media to reduce the number of computational meshes required for CFD simulations. Using the CFD model, we determined the size of the oxidant manifold of a 30 kW-class PEM fuel cell stack that comprises 99 cells. The stack with the optimal manifold size showed a quite uniform distribution of the cell voltages across the entire cells.

Effect of gas diffusion layer compression on the polarization curves of a polymer electrolyte membrane fuel cell: Analysis using a polarization curve-fitting model

The effect of gas diffusion layer (GDL) compression on the polarization curves of a polymer electrolyte membrane fuel cell was analyzed using a polarization curve-fitting model. The polarization curves measured at four different GDL compression ratios were fitted with the model and were decomposed into an open circuit voltage and three over-voltages resulting from activation, ohmic, and mass-transport losses, respectively. The model fitting was excellent enough to use the model in the subsequent analysis of the GDL compression effect. The relationship between the over-voltages and the compression ratio was investigated by analyzing the estimated model parameters, and an optimal compression ratio was determined for the fuel cell. The proposed analysis method based on the polarization curve-fitting model can be applied to identifying quantitative differences of polarization curves under various operating conditions and designs for fuel cells.