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Getting Small

The problem with conventional batteries is that they rely on electrochemistry that dates to the late 18th century, and they have some severe limitations. Most notably, once the supply of chemicals inside the battery has finished reacting, the battery goes dead. You must either connect it to a charger plugged into the wall socket or throw it away-preferably in the recycle bin because of toxic ingredients like cadmium and mercury. And batteries aren’t likely to get much better; virtually every chemical combination has been tried, says Shimshon Gottesfeld, chief technology officer at Albany, NY-based Mechanical Technology, a company developing micro fuel cells. “Even the best batteries have little chance to go very much higher” in the power they can produce by weight, he says.

Fuel cells are more complex, but they carry fundamental advantages. As long as there’s a supply of hydrogen or methanol, the fuel cell will produce electricity. Moreover, thanks to the high-energy fuels they use, fuel cells produce more energy for their weight than batteries ever will.

But fuel cells are tough to engineer, and the smaller ones are toughest of all. The design challenges for micro fuel cells start with the choice of fuel. Hydrogen is impractical; it’s a gas and must be compressed at very high pressures, and even then it requires tanks too large for portable electronics. Methanol/water mixtures are more easily stored in a small fuel cell, but using them creates new engineering hurdles. To manage a liquid fuel, tiny pumps and pipes are required. Then there’s the waste water. Not even the most ardent cell-phone users would tolerate power supplies that drip on their shoulders, so fuel cells must evaporate the water. All fuel cells create heat; the small versions operate at anywhere from 15 degrees C to a scalding 60 degrees C. While this provides a means to evaporate waste water, it also requires the right balance of insulation and venting.

Cramming all of this into a nifty package the size of a couple of AA cells presents a real challenge. And given the fierce competition to commercialize a micro fuel cell, most corporate players are cagey about how they’ve begun solving these problems. “There is a lot of posturing among the companies, but that is what you’d expect in the early stages as they try to maintain their positions,” says fuel cell watcher Chris Dyer, editor of the Journal of Power Sources. But, he adds, “This isn’t smoke and mirrors. It’s a real technology and just requires some clever engineering to make it work.”

Most observers predict that the first micro fuel cell on store shelves will be a charging device using methanol. A half-dozen companies are working on variations on this theme, including Manhattan Scientifics. In Hockaday’s design, the fuel cell components aren’t arranged in a stack, like traditional automotive fuel cells. Rather, they’re laid out side by side, like components on a microprocessor, making them amenable to semiconductor-manufacturing techniques.

Mechanical Technology has already cofounded a company that sells refrigerator-sized commercial and residential fuel-cell power plants. Now, Mechanical Technology is setting its sights on smaller things, starting with charging devices. “We are very optimistic about the prospects for commercializing this,” says Mechanical Technology’s Gottesfeld, former director of the Los Alamos lab’s fuel cell research program. “We are not only looking at chargers but a complete system for cell phones. We’re also looking at other possibilities like laptops, the toy market and power tools.”

Motorola and Korea’s Samsung are also actively developing prototypes. Hyuk Chang, a principal researcher at the Samsung Advanced Institute of Technology outside of Seoul, says the company’s goal is to demonstrate working models in a year, again with charging devices leading the way. “I think it will take another two years to get from the lab into customers’ hands,” says Chang. “The hard question is what will be the first application.”

At Motorola, fuel-cell project leader Jerry Hallmark is pursuing a strategy that promises smaller fuel cartridges. He says the company has developed tiny fluid systems that would continually recycle the water in the methanol-water fuel mixture. Replacement cartridges could just carry undiluted methanol. “The fuel cell can’t run on concentrated methanol; it needs a dilute solution. But you don’t want to carry a dilute fuel,” he says. Hallmark adds it will likely take three to five years for any company-including Motorola-to begin selling a product.

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