Many long-time handheld users look back with nostalgia to the days when their handhelds ran for weeks or even months on a pair of AAA batteries. Batteries simply haven’t kept up with the increasing power demands made by color screens and faster processors.
A potential solution is the fuel cell. These convert methanol into water and power. Unfortunately, these are mostly still on the drawing board, and the working models are much too large to fit in a handheld.
Still, Toshiba has said that it has a prototype for a Direct Methanol Fuel Cell (DMFC) that can be used to recharge portable devices. This is 3.9 inches by 2.4 inches by 1.2 inches (100 mm by 60 mm by 30 mm). It weighs 4.6 ounces (130 gram). This can produce 1 W of power for about 20 hours with a 1.4 cubic inch (25 cc) methanol canister. According to Toshiba, this is sufficient to recharge a typical handheld or mobile phone six times.
Drawing on know-how gained in its work on DMFCs for laptops, Toshiba achieved the miniaturization necessary by reducing the size of auxiliary parts, such as the fuel tank, the liquid and air transmission pumps, the interface and electric circuits, and the DC-DC converter. The methanol fuel is also stored at a high concentration.
Methanol in a fuel cell delivers power most efficiently when mixed with water in a 3% to 6% methanol concentration — a concentration requiring a fuel tank that is much too large for use with portable equipment. Toshiba overcame this by developing a system that allows a higher concentration of methanol to be diluted by the water produced as a by-product of the power generation process. This allows methanol to be stored at a much higher concentration, and achieves a fuel tank less than 1/10 the size of that required for storing the same volume of methanol in a 3% to 6% concentration.
The company will demonstrate this device at a trade show in Japan this week. Toshiba expects to have it on the market in 2005.