Hydrogen storage

Because of its low density, hydrogen must be stored compressed in cylinders. These must be pressure-resistant, shatterproof and very tight to prevent hydrogen leakage. Compressing hydrogen itself is energy intensive. Cryogenic storage tanks with liquefied hydrogen are also used for stationary storage.

Storage in cylinders in vehicles

Hydrogen in vehicles today is usually stored in Type 4 composite cylinders - an aluminium thin-walled container is wrapped with a carbon fibre wrap, forming a very strong unit that resists internal overpressure, destruction and also the penetration of hydrogen molecules through the material itself. The standard operating pressure for today's vehicles is 350 bar (trucks and buses), in passenger cars 700 bar. Piston compressors are usually used to compress the hydrogen to this pressure, and the energy required to compress it to 350 bar is about 30% of the energy in the fuel. A 5 kg hydrogen tank (500 km range) weighs about 100 kg. For an electric car with lithium batteries to have a range of 500 km, the lithium batteries would weigh 600-1 000 kg.

Stationary bulk storage

For stationary hydrogen storage, large-volume steel pressure vessels or cryogenic storage tanks are used, where hydrogen is kept in liquid form at a very low temperature of -253°C. This solution is considered unsuitable for automobiles because even with almost perfect insulation, the hydrogen gradually evaporates and the pressure in the storage tank builds up, and this excess has to be vented outside the tank. Losses with this storage method are typically about 3 % per day. The cost of cryogenic storage is also higher, up to 40% of the total energy contained in the fuel is consumed for the liquefaction itself.