Originally invented by Sir William Grove in 1839, fuel cells are now becoming a viable source of power.
Fuel cells can in their simplest from be regarded as generators. But whereas conventional generators use internal combustion engines to rotate an alternator, fuel cells generate power by producing electrons directly, with no moving parts. As a result, they are very efficient and reliable. Moreover, they are almost silent and, other than electricity and heat, they produce only water vapour. This makes them ideal for indoor use.
Fuel cell systems are clean, very quiet and produce no exhaust gases other than water vapour. As there are very few moving parts, maintenance is minimal.
There are many different types of fuel cell technologies adopted today, each having their own characteristics and each being suited to differing applications. The basic principles of any fuel cell are essentially the same, with all fuel cells using an electrochemical reaction to split hydrogen gas molecules (H2) to form hydrogen ions and electrons. A fuel ‘cell’ essentially consists of two plates (the anode and cathode) separated by an ‘ion-conducting’ electrolyte which can come in many different forms.
A fuel (the simplest form being hydrogen) is passed across the anode where it is split by a catalytic reaction into hydrogen ions (H+) and electrons. Simultaneously an oxygen source (usually either air or pure oxygen) is passed across the cathode side of the cell. As the fuel cell’s electrolyte layer is designed only to allow a flow of hydrogen ions through it from anode to cathode, these flow across the membrane forcing the electrons to flow through an external electrical circuit to the cathode side where they then combine with the hydrogen ions and oxygen to form water. This flow of electrons creates the electrical current or power from the fuel cell.
Anode Reaction: 2H2 => 4H+ + 4e-
Cathode Reaction: O2 + 4H+ + 4e- => 2H2O
Overall Cell Reaction: 2H2 + O2 => 2H2O
Each individual fuel ‘cell’ produces only a small amount of power, each cell’s output differing dependent on their design and size. To provide the higher levels of power output required from a fuel cell system for practical use, the cells are then combined to form a fuel cell “stack” the size of which is dependent on its manufacture and requirements. The systems available on the market today are more correctly termed as fuel cell systems as they comprise all the cells in a ‘stack’ plus the electronic controls required to meter the fuel and oxygen, and control the process.