NTT develops hydrogen fuel cell for mobile phones

IDG News Service - Nippon Telegraph and Telephone Corp. (NTT) said yesterday that it has developed a prototype fuel cell that it hopes to commercialize within three years at a size small enough to fit inside mobile phones and other portable consumer electronics devices.
The prototype is a micro polymer-electrolyte fuel cell (PEFC) that works by combining hydrogen with oxygen, generating electricity and water, and is more powerful than the direct methanol fuel cells (DMFC) now being developed by many companies, said Kazuya Akiyama, a researcher at the energy systems project at NTT's energy and environment systems laboratories.
The power density of the NTT cell -- a measure of the amount of power it can generate relative to its size -- is up to 200 milliwatts per square centimeter. When the fuel cell is commercialized, it will be able to provide a third-generation mobile phone that uses 2.5 watts of power with about nine hours of talk time, Akiyama said in a presentation at NTT's Yokosuka R&D Center.
In contrast, a DMFC developed by NEC Corp. last year offered a power density of 70 milliwatts per square centimeter. NTT calculates that to match the size of lithium ion batteries used in mobile phones, a fuel cell must have a power density of about 160 milliwatts per square centimeter or more, he said.
"DMFCs can't do it. There isn't enough power," Akiyama said.
NTT believes that the extra power advantage means hydrogen-fueled PEFCs will be able to replace lithium ion batteries inside mobile phones. In tests, the prototype has been able to power a phone long enough to allow a video or voice call, he said.
NTT's prototype is currently 13mm by 42mm by 80mm and weighs 104 grams. It will take two years before the company can shrink it so that it can fit inside a cell phone, Akiyama said.
The hydrogen-fueled PEFC technology does have at least one disadvantage compared with DMFC technology, he said. Methanol fuel cells can work off small, nonpressurized cartridges of the liquid, whereas hydrogen-fueled PEFCs require pressurized hydrogen gas. While the hydrogen is only pressurized to two or three atmospheres, the industry has yet to create a small, safe and standardized container for that.
NTT has designed a hydrogen storage unit that is slightly bigger than an automobile battery that can store 50 liters of hydrogen. In the home, it could be used as a refueling station for a number of types of fuel cells, although the unit is too big for portable use.
Building a supply andcontainer infrastructure, creating international packaging standards and making a legal framework to allow transportation of hydrogen canisters will take about three years, a year longer than it will take to resolve similar issues with methanol, Akiyama estimated. Regulations to allow passengers to carry methanol fuel canisters aboard commercial airliners should be completed around 2007.
"The fuel canisters we are using are very heavy and we need to make them smaller and lighter, and safety is a big concern," he said.