Steady state and transient modeling of a PEM fuel cell power plant for transportation applications

UTC Fuel Cells recently developed a freeze capable fuel cell power plant for automotive applications. Steady state and dynamic system models were developed for design and performance characterization. The results of the power plant performance testing indicate very good agreement with these models. Testing showed that the power plant achieves stable performance at all power levels including low power holds. UTC Fuel Cells' cell stack technology enables operation of the power plant at near-ambient pressure. Additionally the low system pressure drop allows the power plant to achieve very high electrical efficiencies at all power levels. The peak efficiency is about 58% at approximately 20% of rated power. Since the power plant does not require compressors, the auxiliary power requirement and acoustic noise level for the system are also low. The cell stack's capability of internal water management and ability to operate at low reactant stoichiometric ratio result in a very stable and predictable transient capability to ramp up from low power to rated power in < 2 sec and also to step down from rated power to low power levels instantaneously in a stable manner.