CARMAKERS’ plans to use hydrogen as a fuel looks like it will avoid the dead end that the gas reached in keeping airships aloft. A series of announcements about hydrogen-powered vehicles at recent big car shows in Tokyo and Los Angeles have reinvigorated its claim as a fuel of the future. Hyundai could have a car in production by next year. But the drawbacks to hydrogen still threaten its re-emergence as one of the clean fuels of the future. None of the successors to the internal-combustion engine has yet set much of a pace. Electric cars are costly; their batteries take a long time to charge but drain quickly. Hybrids, which combine battery and petrol engines, are also expensive and complex. So the need to comply with strict new mileage and emissions standards around the world has renewed the faith of some carmakers in fuel cells. These use hydrogen drawn through a permeable membrane coated with a layer of platinum where the gas combines with oxygen from the air to create water vapour and current that can be used to run electric motors.

Hydrogen power is back in fashion partly because of constant tinkering with the technology. Honda has reduced the size of its fuel-cell “stack” by a third, making it small enough to stuff under the bonnet where a conventional engine would go. Hyundai claims to have cut manufacturing costs by 50% over the past two years. Both unveiled new fuel-cell vehicles in Los Angeles. Toyota revealed its new model car in Tokyo. Several others, including General Motors, which recently formed a fuel-cell partnership with Honda, are close to announcing new hydrogen cars.

Reducing the price of fuel cells helps hydrogen to compete with battery-laden competitors. Moreover, a hydrogen tank can be refilled in the same time it would take to fill up with petrol. And where most electric vehicles have a range of below 160km, all three of the new hydrogen cars are promising up to 480km.

Getting the gas to fill up a fuel-cell tank is a more fundamental problem. Hydrogen is usually tied up in more complex molecules, such as hydrocarbons. Proponents advocate extracting it from natural gas, which is cheap in America thanks to the fracking boom. The problem is that compressed or liquefied natural gas is already being used directly in trucks and other fleet vehicles. Some carmakers have launched natural-gas version of current models, which have modified internal-combustion engines, making them far cheaper than fuel-cell alternatives.

Another source is hydrolysis, using electricity to split water into hydrogen and oxygen. But the energy required to collect, store and convert hydrogen back to electricity means that approach “only makes sense if you use green energy,” contends Rudolf Krebs, Volkswagen’s head of electric propulsion. VW sees fuel-cells as a future backup for batteries in hybrids.

Nissan’s boss, Carlos Ghosn, a hydrogen sceptic, raised another concern at the Tokyo show. “Where is the infrastructure? Who’s going to build it?” There are only a handful of hydrogen filling stations in California, the likely first market for fuel-cell cars, though state lawmakers have approved funding for a scheme that would set up 100 by 2020. Similar plans are afoot in Germany and Japan. Hydrogen may find a role in cleaning up driving. But battery power and ever more frugal versions of gasoline and diesel engines will make for a traffic jam of likely alternative power sources for the future motorist.