Mitsubishi Gas Chemical Company Inc exhibited a fuel cell-based portable power supply unit at ECO-MAnufacture2008 (ECOMA), which took place in Tokyo Big Sight from Sept 10 to 12, 2008.
The power supply unit incorporates an active-type direct methanol fuel cell (DMFC) and has an output of 300W (AC 100V). The fuel cell can operate continuously for about eight hours with a 4-liter fuel tank. The unit measures 380 (W) mm x 450 (D) x 300mm(H), and its dry weight is 22kg. It runs on a methanol-water solution with a concentration of 54%.
The company adopted DuPont's polymer electrolyte membrane called "Nafion" for the electrolyte membrane and reportedly used its proprietary technologies to form a catalyst layer, electrodes and a separator. The outer dimensions of the fuel cell stack, which consists of 40 stacked cells and weighs 3.9kg, are 120 x 120 x 125mm.
The cell has a power density of 130mW/cm2. This is high even for an active system, which controls the fuel supply and the recirculation of reaction water by a sensor and a pump.
Hitachi Ltd prototyped a similar DMFC-based portable power supply unit for Japan Broadcasting Corp (NHK). The unit was used to broadcast news from the Hokkaido Toyako Summit in July 2008 (See related article). Although it weighed only 6kg, its output was merely 100W and the continuous operating time was 2.5 hours (It ran on 500mL methanol-water solution with a concentration of 40%).
Adopted for Suzuki's electric wheelchair
According to Mitsubishi Gas Chemical has promoted a joint development of electric wheelchair using this fuel cell unit for several years with Suzuki Motor Corp, the company said. It only takes a power supply of about 300W to drive an electric wheelchair because it moves slowly.
When riding on the existing wheelchair driven by a rechargeable battery, the users are always worried about battery exhaustion. The major advantage of the fuel cell-based wheelchair is that it can solve such a problem, the company said. (It runs for 60km with 4L fuel.) The wheelchair is not commercially available at the moment, however, as it is still being feasibility tested.