Kurita Water Industries, the company behind the device, expects it to be on the shelves within three years. Kurita predicts that the discovery will transform the global effort to commercialise fuel cells — the complicated, environmentally friendly technology that many hope will replace fossil fuels as the everyday power source.

The device was revealed yesterday in Tokyo at the FC Expo, the largest convention on fuel cells in the world. The event provides a rare glimpse of a technology “arms race” that obsesses engineers around the world. According to the exhibitors, we are within striking distance of powering cars, laptops, wheelchairs, scooters and even entire houses with fuel cells.

UltraCell, a California-based company, said that it would soon start field tests with the US military. The soldier of the future may take just a couple of fuel cells into battle, rather than dozens of lithium-ion batteries to power night-vision goggles, laser sights and other energy-hungry equipment.

But even among the fuel cell’s most ardent supporters, there are doubts over the rate at which the technology can be commercialised.

Christopher Onder, the Swiss engineer behind the world’s most efficient car — a fuel cell vehicle that can travel 12 miles (20km) on a gram of hydrogen — said that expectations had previously been too high. “Two years ago everyone at these events was saying ‘this will be in use ten years from now’. Now I feel that a new mood of realism has set in, and people are saying, ‘probably 20 years is more like it’,” he said.

It is no coincidence that some of the most devoted pursuers of fuel cell perfection are based in Japan, which is nearly totally reliant on energy imports and has discovered the potential for resource-related conflicts with its neighbour, China.

More than 500 technology companies and academics provided an update at the conference. General Motors and DaimlerChrysler were showing off prohibitively expensive fuel cell cars, while others demonstrated designs for petrol station pumps that allow drivers to refuel with hydrogen without risking explosions. The industry is split between several versions of the technology. Fuel cells harness the power output when hydrogen gas passes through a protonexchange membrane.

The debate is over how best to get the hydrogen into the system efficiently, while making the product small enough to be practical. A chief drawback of early ideas has been the need to supply the cell with fuel safely.

The Kurita cell may present a solution. It uses a disposable fuel cartridge slightly bigger than a postage stamp that slides into the side of a phone.

The company is also the first to exploit the qualities of solid-state methanol. It claims that it can turn methanol into a relatively inert solid so it can be safely stored and transported before being used to power the cell.