On demand

A Canadian research group has developed a hydrogen generator that can be used to provide electricity for applications as wide ranging as mobile phone battery rechargers and cellular transmission towers.

Called HyPOD (Hydrogen Power on Demand) the device removes the need for safe storage of explosive and flammable hydrogen gas by making it available only when needed.

The generator consists of a tank containing water and two electrodes — an anode and a cathode, made of different metal alloys and with different electrode potential (ability to lose electrons). When a switch is turned on, this difference causes a current to flow through the water electrolyte. That starts an electrochemical reactions between anode, cathode and water, so that both electrodes generate hydrogen gas. When the switch is turned off, hydrogen production stops.

The electrodes will eventually be used up in this chemical reaction, and the dissolved by-product of hydroxide ions can be re-used for other purposes.

The HyPOD is looking to open up the market for using proton exchange membrane (PEM) fuel cells as take-anywhere chargers and battery replacements for portable devices such as mobiles, PDAs and laptops.

Co-inventor Dave Ghosh, director of science and technology at Canada's

in Vancouver, is leading the effort to commercialise the device, and said his team is thinking of both micro and large fuel cells applications.

'In the case of micro-fuel cells, it will be a compact, disposable plastic cartridge containing water and electrodes,' said Ghosh. 'You can attach this to a fuel cell, which is integrated into a cell phone, and you can click on the generator to start generating hydrogen to feed the cells.'

He said this will give mobile users extra talk time. 'People are out of their homes for a good 10 hours a day much of the time, and today's cell phone batteries run out after a couple of hours' talk time,' he said. 'This device would provide an extra 12 hours, and could cost around 50p.'

He claimed the device is a significant improvement over other disposable 'energiser devices' currently available. These, he said, use less eco-friendly external batteries that will provide only a couple of hours extra talk time.

Ghosh said NRC researchers have estimated that the global market for such a portable recharger is estimated at C$4bn (£1.8bn) by 2013.

As for the possibilities for larger fuel cells, initial uses include back-up power for applications such as cellular transmission towers and computer servers.

'HyPOD devices for those applications are not going to be disposable, obviously,' said Ghosh. 'Those would be like large cylinders refilled with electrodes and water after they are used.

'The devices are only a back-up so they don't get used very often. Just when the power grid fails and they have to keep a cell tower going. They would be used maybe three of four times a year.'

Ghosh said negotiations are under way with a gas multinational and other back-up power unit developers.

The HyPOD prototype has been able to generate 250W, which Ghosh said is 'an interesting size for portable power that could be used for applications such as emergency road signs.' However, the device will need to be scaled up for larger applications. 'Normal back-up power for a cell tower is from one kW upward,' he said.

But scaling up is going to be easier than scaling down. 'A mobile phone charger is less than five watts,' he said. 'We will have to miniaturise the device, and that is going to be a challenge.'