The hydrogen fuel cell is one of the leading alternative fuel technologies. Even though it has been in existence for at least fifty years, the recent developments represent a huge step forward in fundamental technology. Moisture plays an important role in determining the efficiency, quality and safety of hydrogen fuel cells. High moisture content within the hydrogen fuel cell makes it more efficient and precise moisture measurements of the hydrogen during production are required.
There are several different types of fuel cell. Because of its low operating temperature, the fuel cell used to power motor vehicles is the Proton Exchange/ Polymer Electrolyte Membrane (PEM) fuel cell.
In principle, a fuel cell operates like a battery. Unlike a battery, a fuel cell does not run down or require recharging. It will produce energy in the form of electricity and heat if fuel is supplied. A fuel cell consists of two electrodes sandwiched around an electrolyte. Oxygen passes over one electrode and hydrogen over the other, generating electricity, water and heat. Hydrogen fuel is fed into the anode of the fuel cell.
Oxygen (or air) enters the fuel cell through the cathode. Encouraged by a catalyst, the hydrogen atoms split into protons and electrons, the PEM allows only the protons to pass through it to the cathode, the electrons must take a path through an external circuit, creating an electrical current. The protons and electrons then recombine with the oxygen at the cathode, to form water. A fuel cell system which includes a "fuel reformer" can utilise the hydrogen from any hydrocarbon fuel -from natural gas to methanol, and even gasoline. Since the fuel cell relies on chemistry and not combustion, emissions from this type of a system would still be much smaller than emissions from the cleanest fuel combustion processes. Typical process efficiency of 80% can be achieved, which is more than double that of an internal combustion engine.