Despite the rapid growth of compute power in the last decades, the full-fledged, 3D mathematical models of fuel cells are not a viable option when it comes to applications requiring real-time capability; on the other hand, the current crop of 1D models apply boundary conditions pertinent merely to a single point in the cell – to provide data for effective fuel cell system design, a balance needs to be struck. The predictive power of a lower dimensionality fuel cell model can provide a reasonably detailed and accurate assessment and tracking of the fuel cell state and cater data to model-based control algorithms or define requirements for the selection of balance of plant components. To cover a wide parametric space and allow a rapid generation of the corresponding fuel cell system states, a combination of two 1D stationary models (a pseudo-2D model) has been chosen. One model defines the inlet conditions and tracks their evolution along a gas flow channel in a bipolar plate, while the second model (in our case the MMM1D published by Vetter and Schumacher) solves the evolving boundary-value problem throughout the membrane-electrode assembly (MEA) and calculates the fluxes of species, heat and charge exchanged between the gas flow channel and the MEA. Because the most significant changes in the media state (temperature, pressure, composition and flow rate) occur at the cell level, the model can estimate stack outlet conditions from the inlet conditions, extending the cell level model to a fuel cell system context. The results obtained for several operating points are used to discuss the choice of some system components.

The automotive industry is facing the challenge to realize the turn over to a climate-neutral mobility. The use of fuel cell powertrains are a promising way. Especially the short duration for the refueling of the tank in combination with an acceptable range and the separation of energy production and the refueling process show the advantages of the powertrain technology against the battery electric vehicle for the customer. Current vehicle concepts use PEM based fuel cells, which provide in combination with low battery capacities the power for the electric motor. The efficiency of the entire powertrain is influenced on the one side by the design of the fuel cell and the battery size and on the other side by the dynamic power split. The actual series standard of powertrain topologies are fuel cell vehicles with a big fuel cell system and a small battery size. These powertrains shows advantages regarding maximum speed, efficiency and performance. Due to their size these powertrains show big challenges in terms of complexity, costs and long life durability. IAV used their 0D/1D simulation framework to layout a fuel cell based hybrid powertrain (fuel cell system and battery) with a very long range and high durability for the use in a medium-size passenger car. Beside the long range also very low costs can be achieved by the use of a small stack, less components and a low effort for the calibration of the fuel cell system. This powertrain is simulated by different cycles to show the performance in terms of different target values. Furthermore the innovative fuel cell system powertrain is compared with a battery electric vehicle in terms of long range capability. This publication closes with a cost analysis of the fuel cell based powertrain for the automotive market in 2025.

Efficiency-enhancing measures are evaluated for a serial hybrid fuel cell vehicle over a drive cycle. The regarded powertrain consists of fuel cell system, battery, DC-DC converter, inverter and electrical machine. Within the fuel cell system, the air supply is the largest parasitic load. For the lowest dissipation, different air compression architectures are optimized by a scaling algorithm and compared. Phase switching reduces DC-DC losses. Additionally, a variable DC-link voltage increases efficiency of electrical machine and inverter. Dynamic Programming (DP) is used to evaluate these measures. The DP was extended by start-up and shutdown energy of the fuel cell system to model realistic cycle consumptions. Finally, all these efficiency enhancing measures lead to a reduction of energy consumption by 6.4 % for the serial hybrid fuel cell vehicle over a drive cycle.