Electrolysis of water consumes electricity to produce hydrogen and oxygen. The fuel cell, which was discovered in 1839, uses the opposite principle. It would be more precise to use the plural—fuel cells—because there are several different kinds. The kind most used to equip vehicles is based on the proton exchange membrane technology (PEM).
The electricity produced by the fuel cell running on hydrogen meets a variety of needs: power supply in an isolated region, emergency power supply for strategic sites, and the direct production of electricity in a vehicle, allowing it run cleanly and quietly.
Fuel cells use H2 (hydrogen) and O2 (oxygen) to generate electricity and heat, emitting only water. The H2 molecule is composed of 2 atoms, each of which contains a positive nucleus, called a proton or H+, and an electron.
Regarding the PEM technology (Proton Exchange Membrane), the electrochemical system contains a membrane inserted between two metallic conduction plates. This polymer membrane only lets H+ protons, the nucleus of hydrogen atoms, pass through.
The hydrogen molecule comes into contact with the electrodes. The reaction is triggered by a catalyst, which is composed of nanoparticles of platinum coated on carbon particles. When the hydrogen comes into contact with the platinum, the hydrogen molecule gives birth to two protons and two electrons.
The protons pass through the membrane and move toward the other side of the cell. The electrons, which cannot pass through this barrier, pass into the electrical circuit. Simultaneously, on the other side of the membrane in contact with a new catalyst, the protons react with the oxygen and the electrons of the circuit, to form water, the fuel cell’s only by-product.
This clean reaction takes place in each of the basic cells that are combined to constitute an energy module of the desired power. A fuel cell is an assembly of several cells in a series or in parallel in a stack, which makes it possible to obtain different voltages and current output.
The output of a fuel cell varies from 30 to 70%. It is generally 50%. This means that 50% of the hydrogen energy is converted into electricity and 50% is converted into heat. The combination of the fuel cell and the electric engine (which also has a high output) is thus more efficient than an internal combustion engine.
The fuel cell is very quiet. Only the compressor and the ventilation system produce a slight noise. Overall, the fuel cell emits only low noise levels (from about 40 to 50 dB at 1 meter), which is far less than the noise level generated by a normal human conversation (around 60 dB).
It is made up of elementary cells. Stacked in series or in parallel circuits, they generate an electrical current whose voltage and intensity can be precisely calibrated to the intended use.
PEM fuel cells consume about 0.8 Nm3 of hydrogen per kWh produced. A car needs 1.6 kilogram of hydrogen for every 100 miles covered.
© L.Lelong - PE.Rastoin