The activities in the field of fuel cells are mainly devoted to improving power density, increasing life-time and reducing cost of fuel cells and stacks. DLR is mainly active in research and development of fuel cells for aircraft applications, auxiliary power units (APUs) as well as stationary energy supply.
Diagnostic methods – like innovative approaches to measure the local current density and temperature with high resolution – have been developed at the Institute. Controls of cell and stacks based on the detailed information obtained from these measurements are under development enabling self-regulating of cells and stacks. DLR has developed proprietary manufacturing methods for low and high temperature fuel cells.
For polymer electrolyte fuel cells a low cost, dry rolling technique for membrane-electrode production is used which has shown superior performance especially for direct methanol fuel cells. But also for hydrogen polymer electrolyte fuel cells this manufacturing method stands out regarding its cost-effectiveness and flexibility. Thin layer solid oxide fuel cells (SOFC) manufactured by plasma spraying in planar design for temperatures around and below 800 °C have been developed. The metal-supported cells of DLR are especially suited for dynamic operation and are stable against fast temperature changes and redox cycles. Therefore, they are designed to be used as engine independent electrical power sources (Auxiliary Power Units (APU)).
Among them are the research on transport systems e.g. analysis of the structure of transport systems, whereby DLR uses models developed for the analysis of air traffic. Other fields are the application of adaptronics and telematic in vehicle technology or use of advanced light weight materials for vehicle construction. It is well known that the transport sector contributes increasingly to the CO2 emissions. Therefore hybrid and fuel cell vehicles are discussed in order to reduce these emissions. A number of car manufacturers are currently developing fuel cell powered vehicle.
DLR has performed research in fuel cells for space and stationary application for a number of years. A part of these capacities has been put into the transport division. There exist different types of temperature Polymer Electrolyte Fuel Cell (PEFC). The operating temperatures are around 800 C and around 80 C. Generally the PEFC is considered as the most promising type of fuel cell for power trains. Actually hydrogen is used as a fuel for the PEFC. The following paper deals with the PEFC. The design of fuel cell systems is a multi- disciplinary task. The fuel cell itself is an electrochemical energy converter. The detailed modeling of an fuel cell requires knowledge e.g. in electrochemistry, heat and mass transfer, multiphase thermodynamics, fluid dynamics.
A fuel cell system consists of several sub systems:
– fuel cell
– air supply system
– fuel supply system = hydrogen supply system
– cooling system (heat and water management)
– control system
The air supply system has to deliver the oxidant usually oxygen to the fuel cell. It consists of blowers, fans valves and pipes. The fuel supply system could be a tank where the hydrogen is.