Illustration of a hydrogen fuel cell
Hydrogen fuel cell technology
The fuel is hydrogen gas that reacts with oxygen from the air with aid of a catalyst, typically platinum. This reaction produces electricity to power the vehicle or other devices with the by-products of heat and water vapor. Fuel cells are much more efficient than combustion-based technologies at converting the chemical energy in the fuel to electrical energy. Furthermore, hydrogen can be produced via electrolysis by renewable electricity and can thus be part of a carbon emissions free energy transition.
Hydrogen is fed to the anode of the fuel cell while air is fed to the cathode. A catalyst at the anode separates the hydrogen atoms into protons and electrons, which take different paths to the cathode. The electrons go through an external circuit, creating a flow of electricity. The protons migrate through the electrolyte to the cathode, where they unite with oxygen and the electrons to produce water and heat.
Variables of fuel cell design
The key decision is to select the size of the fuel cell for optimal output. Larger cells provide more power output as there is a larger catalyst surface area but this increases the weight and cost especially with platinum as the typical catalyst. Adjusting the spacing between the electrodes in the fuel cell stack and improving the gas flows through the cell can improve the catalytic reaction and hence the performance instead of increasing size. Another factor being optimized is the movement of the waste water vapor out of the cell to prevent it blocking up the catalytic surfaces. The other waste product of heat also has to be efficiently removed from the cell to prevent overheating.
The test bench enables real world operating conditions to be investigated that will affect the performance of the fuel cells over time. These include changing load conditions caused by starting and stopping, and coping with extremes of temperature and humidity that vehicles operate in. These can stress the mechanical stability of the fuel cell system materials over time. This is important as fuel cell applications require long operation lives. For example, the American Department of Energy has set ultimate targets for fuel cell system lifetime under realistic operating conditions at 8.000 hours for light-duty vehicles, 30.000 hours for heavy-duty trucks, and 80.000 hours for distributed power systems.
Further details on this project can be found at www.zbt.de/en/news/rd-highlights/science-and-projects/detail/News/dynacell-dynamic-modelling-and-model-based-control-of-pem-fuel-cell-systems/.