FCEV Performance Assessment - Electrochemical Fuel Cell and Battery Modelling on Vehicle Level 2020-01-0857
The worldwide trend to establish CO2-neutral mobility requires innovative powertrain technologies. The application of proton exchange membrane fuel cells, together with green hydrogen, is an emission neutral technology. In order to make fuel cell powered vehicles (FCEV) successful on the market, acquisition costs for the consumer must be reduced, while energy efficiencies and lifetime must be raised. Efficiencies and operating conditions are key for the design of fuel cells and batteries, as both components are prone to degradation phenomena during their lifetime. Model based development approaches are therefore inevitable to master the complexity of a complete FCEV. Advanced multi-domain system level simulations need to incorporate detailed descriptions of individual components. This way, detailed intra-component phenomena, inter-component interactions and inter-domain exchanges can be addressed simultaneously, providing the basis for approaching engineering limits early in the development process.
The study presents a FCEV model. The model comprises 7 domains. A mechanical network transports the power from e-motor to wheels considering gearboxes, differential, brakes etc. (1). An electrical network, operated at different voltage levels, connects the fuel cell with battery and e-motor (2). Gas path networks support the fuel cell with conditioned feed gases of air and hydrogen (3). The thermoregulation is handled by incompressible flow networks of water and oil (4). A generic info-flow network connects, via sensor and actuator components, the plant model with corresponding control functions (5). The fuel cell is modeled with an advanced and computationally fast 3D resolved approach considering all relevant transport phenomena in the channels, the gas diffusion layer and electrochemical reactions in the catalytic membrane. High computational performances arise from a dedicated analytical-numerical approach (6). The Li-ion battery model follows the electrochemical approaches from Doyle, considering the impact of material properties on the electro potential and species concentration fields (7). All domains are linked with a specifically developed multi-rate co-simulation framework to establish an overall real-time capable simulation performance. The vehicle model is parameterized with data from literature while keeping the complexity of the control units at a reasonable level. The fuel cell and battery models are validated with experimental data and reference results from 3D-CFD simulations. The latter comparison shows potential of combining 3D CFD with vehicle system level models in a consistent simulation workflow. The full vehicle model is used to analyze the entire chain from vehicle system parameters down to spatially and temporary resolved parameters in both electrochemical devices. Thereby a causal relation between required power output, intra-component phenomena and component efficiency is established for the first time within a transient vehicle simulation.
Johann C. Wurzenberger, Davor Rašić, Gregor Tavcar, Thomas Glatz, Igor Mele, Tomaz Katrasnik
AVL LIST GmbH, AVL-AST d.o.o., University of Ljubljana