Impact of Different Fuel Cell Stack Warm-up Strategies on Drivability and Consumption Using a 1D Multi-Physics System Simulation

Abstract

Fuel cell systems are on track to become a mainstream power generation source for various sectors. The transportation industry has a significant interest in fuel cell technology primarily for economic and sustainability reasons. During the product development of fuel cell systems, suppliers and OEMs are faced with many strategically and technically challenging questions under stringent end user requirements and economics. In order to select a competitive system topology, it is first required to understand the design criteria and limits for a respective market and application. Consequently, engineers are faced with many technical challenges especially in understanding and optimizing complex interactions of fuel cell stacks with the propulsion platforms. One practical example of this is the cold start of a fuel cell. Protecting the stack components from damage and degradation during cold start requires energy and thermal management strategies that enable an optimal balance between energy consumption, cost, and warm-up time. This is particularly challenging because of the large number of hardware possibilities and corresponding use cases. For example, certain measures need to be accounted for to achieve a successful cold start. Such strategies may take place already at the time the vehicle is parked and focus on maintaining a minimum stack temperature during that period. For the warm-up, at the time the vehicle is started, a combination of internal and external heating by electrical or chemical means inside the stack itself or its media supply is possible. This contribution presents a methodology addressing these challenges by means of multi-physical system simulation. An integrated system model of an FCEV is developed with various parameters, boundary conditions and DoE analysis capabilities. It consists of a predictive fuel cell stack model reacting to changes in temperature, pressure and humidity while current to an electric powertrain is supplied. Within the plant model, the fuel cell stack is connected to 1D flow systems for coolant, hydrogen and air. The components of the integrated model allow for rapid adaptation of the subsystem components, topologies and control strategies. This opens the door for optimization and design of experiments methods, which are used to compare and determine fast warm-up strategies with low energy consumption that can be deployed for the FCEV platform.