PEM (Proton Exchange Membrane) Fuel Cell is an electrochemical converter. It converts the chemical energy from hydrogen (H2) through an electrochemical reaction with oxygen (O2) into electricity. The by-products are heat and water. The global reaction is given below:
A fuel cell is a modular device. It is composed of a number of cells defining the total voltage. The total current is proportional to the cell surface. The best PEM Fuel Cells reach a power density of 1 W/cm² and a total power density of 3 kW/kg.
The electrochemical reactions occur in the two electrodes: hydrogen oxidation occurs within the anode and the oxygen reduction occurs within the cathode. Both electrodes are separated by a membrane exchange of protons (thickness around 30 μm). More specifically, to accelerate the electrochemical reactions, a catalyst (platinum nano particles of around 5 nm for example) is necessary. The electrochemical reactions are produced on the surface of the catalyst particles. These particles are supported by an electronic conductor. The one most commonly used is an agglomerate of black carbon particles (size around 100 nm). Moreover, to ensure protonic conductivity until the active sites on the catalyst surface, these agglomerates of carbon and catalyst are enveloped by a thin film of ionomer (same material as the membrane). The whole of these agglomerates is a porous media and it is called the active layer. The thickness of the active layer is around 5 μm for the anode size and 10 μm for the cathode size.
To increase the gases transportation (H2 and O2) and the water produced into the cathode and the heat evacuation, one or two layers of a micro porous media (based on carbon fibers) are added between the active layer and the bipolar plate. The thickness of the gas diffusion layer (GDL) is around 300 μm.
The whole, composed of the membrane, active layer and GDL is called MEA (Membrane Electrode Assembly).
Moreover, the bipolar plates ensure the gas distribution and the water evacuation from the MEA. The design of the channels and the material used for the bipolar plates is determinant for the fuel cell performance.
Finally, a fuel cell needs a complex system to run at high efficiency level. Indeed, the performances of the fuel cell depend on gas pressure, hygrometry, temperature, stoichiometry and demanded current. Moreover, to also optimize the durability of the fuel cell, the operating conditions must be controlled. The different subsystems must distribute and condition the gases (pressure, hygrometry, flow, temperature) and also evacuate the water and heat by a cooling loop system. The different components of the system must be controlled by a supervisor.
A fuel cell produces electricity from hydrogen on its place of use, with no greenhouse gas or particle emissions, and no noise. Hydrogen can be produced from a wide range of energy sources, in particular natural gas, as well as renewable energy sources. Hydrogen therefore has great potential as a source of clean energy and for guaranteeing secure supply. In the HYCARUS project, the partners Air Liquide will develop high-pressure storage systems and supply of hydrogen gas onboard for the fuel cell . The system must be compatible with the special constraints imposed by an aeronautic environment: mass, lack of space, temperature, vibrations, etc.
A galley is the kitchen on board an aircraft. Usually the galley is laid out in a typical efficient style, all to efficiently utilize the usually limited space on board an aircraft. Most of today’s commercial aircrafts are equipped with one or more galleys.
Main function of the galley is to store and prepare food and drinks. Oven units can be installed which can heat the food before serving it to the passengers. To serve hot drinks like coffee or thee, coffee makers or water boilers can be installed. Under the work deck trolleys are stowed. These trolleys can be used to serve the food and drinks to the passengers but they also are used to store food and drinks during the flight. Part of the food and drinks requires to be chilled. To accommodate this cooling requirement a refrigerator can be installed or the galley can be equipped with cooled trolley compartments.
For the HyCARUS project an Airbus A320 G4 galley is used. This Galley is located in the rear of the aircraft, in combination with a lavatory.