Fortis Saxonia is
supported by:
Fuel Cell
The fundamental science of fuel cell technology originates from the middle of the 19th century. Christian Friedrich Schönbein discovered the pricipal of the fuel cell. Sir William Robert Grove developed the first prototype utilising hydrogen and oxygen to create an electric potential. This discovery was not put into practise for a long time. In the middle of the 20th century fuel cell technology began to be exploited for military purposes. This technology has had and will continue to have great significants for space programs. It has only been used for civilian applications for the last 25 years. In order for civilian applications to become more widely viable it will be necessary for costs to be reduced, the efficiency to be improved, the life span to be extended and for hydrogen distribution to become more wide spread.
The working principal of the fuel cell is comparatively straight-forward. It consists of two electrodes, an anode and a cathode, separated by an electrolyte which also acts as a membrane. Chemically, the process is a redox reaction. Oxidation occurs at the anode which consumes hydrogen, or another fuel (e.g. methanol). At the cathode the oxidant (e.g. oxygen) is reduced. In this case the heart of the fuel cell is the semipermeable membrane. The cathode and anode are coupled via this semipermeable membrane which allows hydrogen ions but not elemental hydrogen to pass through. This process results in a controlled reaction as opposed to the potentially violent exothermic reaction that would otherwise occur. Effectively, it is a cold combustion process. Electrons are collected at the anode and travel via an electrical load to the cathode where an electron deficit was created. At the cathode, hydrogen ions react with oxygen from air to form pure water. It is due to this external transfer of electrons that it is possible to make use of the energy which was produced.
Different types of fuel cells exist, depending on the membrane material and the kind of fuel. The fuel cell used in SAX I incorporates a polymer membrane. This type of fuel cell utilizes:
- graphite, metal and other conductors for the anode and cathode,
- polymer membrane as the electrolyte,
- hydrogen as reductant,
- oxygen as oxidant.
The entire fuel cell unit consists of the stack and peripherals. These peripherals are vital to supply the reactive gas to the stack. In a similar fashion to an internal combustion engine, the reaction process within the fuel cell is begun using an external battery until the reaction becomes self-sustaining. When calculating the overall efficiency of the fuel cell unit the peripheral energy consumption has to be taken into account. The remaining power from the stack can be used externally.
