Fuel Cell Simulation Model for Aircraft Integration Analysis in Early Design Phases

Air traffic's rapid expansion necessitates aircraft reconfiguring to mitigate greenhouse gas emissions. Hydrogen propulsion presents a promising alternative to reduce aviation's environmental impact, yet it introduces numerous new challenges, particularly in the design of novel system architectures. One promising solution is the hydrogen fuel cell (FC), which can generate electricity without CO2 emissions, with water as its unique byproduct. A versatile mathematical model is essential to analyze the behaviour and performance of these innovative devices during the early stages of aircraft design. This model must interact seamlessly with all Balance of Plant (BoP) components - devices facilitating the fuel cell's operation. A fuel cell modelling approach based on defining an equivalent circuit is adopted. This approach can capture these devices' typical losses and dynamic behaviour. The core model, adapted and refined from a zero-dimensional model in existing literature, includes several key assumptions: dynamic effects during transients are considered, the operating temperature is constant, the membrane is optimally hydrated, and high current densities are excluded. This model can accurately represent the behaviour of both Proton Exchange Membrane Fuel Cells (PEMFCs) and Solid Oxide Fuel Cells (SOFCs). To enhance the model's fidelity, we incorporated two formulations for modelling heat production: one employs a detailed enthalpy balance of reactants and products, while the other uses a simplified energy balance. The mathematical model is implemented in the Modelica language, enabling the creation of a fuel cell block with acausal interfaces. These interfaces allow integration with other components, such as electrical loads, the hydrogen tank, the air intake, and a cooling system. Specifically, the acausal model is designed to represent the behaviour of PEMFCs. Validation with real PEMFC stack data, sourced from the market and collected in databases, confirmed the model's accuracy. Importantly, the model's parameters are directly derived from fuel cell stack datasheets, guaranteeing flexibility and ease of use. To demonstrate the model's practical application, a rudimentary BoP was constructed around it to simulate a realistic case study. The mission profile of an ATR 72-based aircraft utilizing hydrogen-powered electric propulsion is simulated. This model allows for examining various parameters, including the quantity of hydrogen required for the mission, electrical and thermal energy production, and overall system efficiency. Simulations were conducted using two different fuel cells: one from the early 2000s with lower performance and another incorporating the latest aviation technologies. This comprehensive model is a valuable tool for studying different configurations of hydrogen fuel cell systems during the preliminary design phases of new aircraft. It allows detailed analysis of hydrogen consumption, energy production, and system efficiency and facilitates the development of more sustainable aircraft.