Engineers developing hydrogenpowered cars could get a welcome boost from discoveries recently made at Lawrence Livermore National Laboratory. A cryogenic pressure vessel developed there can hold liquid hydrogen at -420°F.
Lawrence Livermore National Laboratory |
Tanks currently in use by hydrogen researchers can only hold liquid hydrogen at between 2 and 10 atmospheres for three to four days, even when wrapped in the best thermal insulation available (which is 0.5% as conductive as Styrofoam insulation). Current tanks consist of an inner stainless-steel vessel rated for six atmospheres (maximum working pressure) surrounded by a vacuum space filled with multilayer insulation, then encased in another stainless-steel vessel to keep the insulation performing at its best. (Multilayer insulation works only under a high vacuum.) A tank to store 22 lb of hydrogen would weigh 330 lb and cost $2,500 when mass produced, according to Livermore researchers.
Livermore’s pressure vessel can hold liquid hydrogen at 350 atmospheres for six days without venting, even as the pressure inside increases because of heat transfer from the environment. In fact, the vessel will hold hydrogen indefinitely without venting when the tank is only one-third full. The fuel tank has an aluminum cylinder wrapped in carbon-fiber tape impregnated with epoxy resin. This composite pressure vessel is then surround by multilayer insulation and an outer vacuum vessel. A new tank that holds 22 lb of hydrogen would weigh about 330 lb and cost $4,000 when made in large quantities.
The new tank’s ability to hold and deliver high-density liquid hydrogen without losses could make hydrogen-powered vehicles more practical. Last year, for example, the Lawrence Livermore hybrid vehicle traveled 650 miles on a single tank of hydrogen.