Visitors thronged the booth of NTT DoCoMo Inc of Japan at Wireless Japan 2006, the communications show held from July 19 to 21, 2006, to see the lipstick-sized fuel cell; many expressed wonder that it could charge a mobile phone three times. What attracted their attention was the solid polymer fuel cell jointly developed by NTT DoCoMo and Aquafairy Co of Japan (Fig 1). Usable as an external charger for mobile phones, it measures 24 x 24 x 70mm and weighs 45g. NTT DoCoMo is also co-developing direct methanol fuel cells (DMFC) with Fujitsu Laboratories Ltd of Japan (R)C the new development slashes volume to 25% while doubling output to 2W (Table 1).
The firms were able to reduce the size this much by switching to a hydrogen fuel to make it easier to boost output, and generating the hydrogen from just water and a metal-based hydrogen generation agent, with no reformer. A single 10mL fuel cartridge, holding water and hydrogen generation agent, can generate 10Wh of electric power: enough to charge a mobile phone three times.
Using Pure Iron?
Aquafairy developed the generation cell and hydrogen generator. The firm was established on June 30, 2006 by a technician involved in developing fuel cells at Nitto Denko Corp. He has worked on generation cells since 2002 and hydrogen generators since 2004, beginning joint development with NTT DoCoMo about one year ago.
Details of the hydrogen generator have not been disclosed, but in October 2004 Nitto Denko filed for a patent on a method of generating hydrogen using pure iron made by reducing hydrogen oxide into pure iron, pressed into a porous shape. The new development is thought to use this pure iron.
The developed fuel cell can turn its water supply on and off to match power on/off, and power generation is stable regardless of attitude. The problematic output fluctuations of DMFCs can be ignored, said NTT DoCoMo, because of the high 2W output. This means that the compensatory capacitors and other components are no longer required, so that a standard electrical circuit can be used.
NTT DoCoMo explained, "There is some question about whether the fuels cells will be able to be carried onto an aircraft, but we hope to productize in 2007 if the price works out right."
There are a number of safety issues to be assessed concerning mounting the fuel cell internally, however, and it is likely that actual product could be delayed until 2009 or later.
by Kouji Kariatsumari
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