Hydrogen Storage

Hydrogen is the most abundant element in the universe and has great potential as an energy source. It can be easily generated from a renewable energy source and is non-polluting. This lighter-than-air gas makes the perfect fuel as it contains three times the energy of liquid hydrocarbons and when it reacts with oxygen to produce energy, forms water as a harmless by-product. But, one of the biggest challenges to using hydrogen as a fuel is finding a way to store it.

Hydrogen in gaseous form occupies a large volume; a gram of hydrogen gas occupies approximately 2.9 gallons of space at atmospheric pressure. The goal is to pack hydrogen as close as possible, i.e. to reach the highest volumetric density , hence, the gas must be intensely pressurized to several hundred atmospheres and stored in a pressure vessel. In liquid form, hydrogen can only be stored under cryogenic temperatures. However both these options are not practical for everyday use and hydrogen gas storage in small tanks, especially for mobile applications, is difficult.

There exists several alternatives of storing hydrogen with specific advantages and drawbacks. Storing hydrogen can be done in the following main ways :-

Storage in compressed form
Hydrogen is normally compressed to between 200 and 250 bar for storage in cylindrical tanks of up to 50 litres.

Storage in liquid form
The advantage of liquid hydrogen is its high energy, which is triple times that of gasoline. It is the most energy dense fuel in use nowadays. Liquid hydrogen typically has to be stored at minus 253° C. The hydrogen storage tanks are insulated, to preserve temperature, and reinforced to store the liquid hydrogen under pressure.

Storage by chemical bonding (Metal Hydride Tanks)
This method uses an alloy that can absorb and hold large amounts of hydrogen by bonding with hydrogen and forming metal and liquid hydrides.

Glass Spheres
A glass sphere is heated, which increases the permeability of its walls, and filled by being immersed in high-pressure hydrogen gas. After that the spheres are cooled, locking the hydrogen inside of the glass balls.

Storage by the reformation process
The reforming process involves removal of hydrogen from the original fossil fuel. The reformed hydrogen is then cleaned of excess carbon monoxide, which can poison certain types of fuel cells, and then utilized by the fuel cell.