Hydrogen has been touted as an environmentally friendly wonder fuel that can be used in vehicles and burns to produce only water as a by product. The problem with hydrogen is that producing it is far from environmentally friendly and storing it in a fuel tank is extremely hazardous. Researchers are turning to nanotechnology to overcome these problems.
Difficulties With Hydrogen
Highly flammable hydrogen presents storage and transport problems as it is an easily ignited, bulky gas. Modern gasoline powered vehicles tend to have a range per tank of around 450-500km. Using current technologies, a hydrogen fuel tank would need to have a capacity of around 200litres to give a vehicle this range. To be of an acceptable size the tank should store at least 6% by weight of hydrogen when compared to the tank or 0.045kg/L.
It would also need to resist rupture and leakage in the event of an accident, while freely releasing the hydrogen as required.
New Hydrogen Storage Methods
Several new methods are being developed for the storage of hydrogen. These systems are based around a range of materials but the two most promising systems use carbon nanotubes and metal hydrides as the storage medium.
The high surface area of carbon nanotubes allows the construction of a microporous material where the hydrogen is held like water is held in a sponge. Unfortunately unless run at cryogenic temperatures, this system currently leaks hydrogen.
Metal hydrides are able to meet and surpass the storage density problem but at this stage require extremely high temperatures in order to release the hydrogen.