Plug Power Inc (PLUG)

[Ecomike]

In answer to your question:

http://energy.gov/eere/fuelcells/liquid-hydrogen-delivery

Gaseous hydrogen is liquefied by cooling it to below -253°C (-423°F). Once hydrogen is liquefied it can be stored at the liquefaction plant in large insulated tanks. It takes energy to liquefy hydrogen—using today's technology, liquefaction consumes more than 30% of the energy content of the hydrogen and is expensive. In addition, some amount of stored hydrogen will be lost through evaporation, or "boil off" of liquefied hydrogen, especially when using small tanks with large surface-to-volume ratios