Toshiba Corporation, the world leader in fuel-cell technology for handheld electronic devices, announced the prototype of a highly compact direct methanol fuel cell (DMFC) that can be integrated into devices as small as digital audio players and wireless headsets for mobile phone.At a compact 22 x 56 x 4.5mm (maximum of 9.1mm, for the fuel tank), the slim prototype DMFC is as long and wide as a woman’s thumb, a size advantage that will give greater design freedom for developers of handheld electronic devices. The latest prototype, with its total weight only 8.5g, is small enough for integration into a wireless headset for mobile phones, but still efficient enough to power an MP3 music player for as long as 20 hours on a single 2cc charge of highly concentrated methanol.
The new fuel cell outputs 100 milliwatts of power, and can continue to do so, non-stop, for as long as users top up its integrated fuel tankÃ³a process that is as simple as it is safe.
The new DMFC adopts a “passive” fuel supply system* which feeds methanol directly into the cell.
In developing a passive DMFC, Toshiba found a solution to the potential problem of “methanol crossover,” in which methanol and oxygen combine without an energy-producing reaction. The company has optimized the structure of the fuel cell’s electrodes and polymer electrolyte membrane that trigger the reaction.
This approach allows use of a highly concentrated methanol solution** as a fuel, which also overcomes a major obstacle to small fuel cells: achieving a very small fuel tank. The cumulative result of these advances is the world’s smallest 100mW fuel cell; a more compact, more efficient DMFC that outperforms its predecessors by a factor of five in terms of power output.
Toshiba is a recognized leader in development of active DMFC for PCs and other portable devices. The company’s latest announcement confirms its parallel leadership in passive fuel cells that can power the smallest portable devices on the market
Today’s announcement demonstrates that Toshiba remains a step ahead of its competitor’s in fuel cell miniaturization and operating efficiency. Toshiba expects to commercialize DMFC for PCs in 2004 and for smaller handheld devices in 2005.
Active and Passive Fuel Supply System
Two types of DMFC are being brought to products: “active” and “passive”. Active systems use a pump and fan to feed methanol and oxygen into a cell stack, where the oxygen reacts with the methanol to produce electricity.
Active systems are more complex and output more energy than passive systems, and are better suited for larger fuel cells. However, passive DMFC have a simpler structure that requires no pump or fan, and use the concentration gradient to deliver and circulate methanol and oxygen in the cell stack.
Methanol in a fuel cell delivers power most efficiently when mixed with water in a concentration of less than 10%Ã³a dilution requiring a fuel tank that is much too large for use with portable equipment.
Toshiba overcame this and developed a system that allows a higher concentration of methanol to pass into the cell stack and produce electricity efficiently. As the result, Toshiba’s new DMFC realizes a fuel tank less than 1/10 the size of that required for storing the same volume of methanol in a concentration of less than 10%.
Fuel tank: H9.1mm
Basic Concept of DMFC