This problem was solved several years ago. Such

firms as Quantum (partly owned by GM) and Dynetek now sell filament-wound carbon-fiber tanks lined with an aluminized polyester bladder instead of the traditional solid metal liner (cutting weight by half and materials cost by a third). Such carbon tanks have 9–13 times the performance of an aluminum or steel tank, but can’t corrode and are extremely rugged and safe, unscathed by crashes that flatten steel cars and shred gasoline tanks. The car isn’t driving around with highly pressurized hydrogen pipes, either, because the hydrogen is throttled to the fuel cell’s low pressure before it leaves the tank. Such aerospace-style tanks holding up to 700 bar (10,000 psi) and proven over 1,655 bar (24,000 psi) have been tested by GM and others in fuel-cell cars and are legally approved in Germany; U.S.authorities, who have licensed 5,000-psi (350-bar) hydrogen tanks, are expected to follow suit shortly. Linde AG recently installed a 700-bar German filling station for Adam Opel AG. Such carbon-fiber tanks could be mass-produced for just a few hundred dollars, and at the currently U.S.-approved safety factor of 2.25, they can hold 11–12% hydrogen by mass. A 350-bar hydrogen tank (2.7 MJ/L at LHV and 300 K) is nearly ten times the size of a gasoline tank for the same energy content. However, the 2–3-fold efficiency advantage of the fuel cell, i.e., less energy expended per mile, compared to a gasoline engine reduces this enlargement to 3.2–4.8-fold — even less when you include the saved size and weight of other parts of the car that are no longer needed, such as the catalytic converter. That factor shrinks still further — making the hydrogen tank only modestly bigger than a samerange gasoline tank in today’s cars, but far lighter — when cars are designed to use two-thirds less power to move them, hence two-thirds less stored hydrogen for the same driving range. This requires cars with much lower aerodynamic drag, rolling resistance (energy losses to heating tires and road), and especially weight. Their weight can be halved, yet they can maintain superior crash safety even when hitting a heavy metal car, by making them from carbon-fiber composites. These space-age materials can absorb up to five times as much crash energy per pound as steel, and can crush more smoothly, using the crush length up to twice as effectively. Carbon-fiber racecars are expensively handmade, but a new patent-pending manufacturing process is expected to be affordable at automotive volumes (10,000–100,000 cars per year). In 2000, its developer, Hypercar, Inc. — a technology development firm spun off from Rocky Mountain Institute in 1999 to commercialize lightweight and efficient vehicle technology— de-signed an ultralight concept car called the Revolution (see sidebar) to illustrate the implications of ultralight autobodies and highly integrated design. This conceptual midsize SUV would have the size, safety, comfort, and performance of a Lexus RX300, yet with five times its Dfficiency —a modeled average of 99 mpg equivalent. Detailed production cost analysis suggests that such a concept car could be manufactured at mid-volume (50,000/year) at a cost competitive with comparable-class vehicles in today’s market.

Automotive high-pressure hydrogen tanks are filled in a few minutes via a small-diameter but rugged hose with a securely locking metal fitting, similar to those used to refuel with compressed natural gas. The hydrogen gas simply flows from a prefilled storage tank that’s typically at about one-fifth higher pressure, like the self-contained Air Products Hydrogen Fueler with its 427-bar storage. Hydrogen refueling may become automated: it’s no more suitable than is gasoline for dispensing by careless people, although even in the event of a mishap, the consequences would probably be less grave than with gasoline

We’d need to lace the country with ubiquitous hydrogen production, distribution, and delivery infrastructure before we could sell the first hydrogen car, but that’s impractical and far too costly — probably hundreds of billions of dollars.