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Cheaper, more efficient fuel cells on the way

Hybrid cars like the popular Toyota Prius are facing greater competition after a Silicon Valley-based company developed cheaper, more efficient fuel cells.Toyota

Hybrid electric/gasoline cars may have even greener competition in a few years now that a tiny Mountain View company has figured out how to make a cheaper, more efficient fuel cell membrane.

By using nanoengineering techniques to align the material's molecules, SRI spin-off PolyFuel can produce a membrane — the thin filter at the heart of a fuel cell system — capable of working within a broader range of temperatures and producing more power per square centimeter than fuel cell membranes in use today.

While PolyFuel has not yet tested its membrane outside a research laboratory, several major car manufacturers have validated the company's results. Results have been so promising, says Jim Balcom, CEO and president, that a viable test engine could be built within two to five years.

"Most market analysts are projecting early fleet introductions in the 2007 time frame, and that's based on the membrane technology that people are already using today," he says. "Those initial cars will have limited capabilities, but we should see high-volume commercial production based on (PolyFuel) membranes by the middle of next decade."

Industry analysts are cautious, but excited to see fuel cell technology advancing from the processes first developed 40 years ago for the Gemini space program.

“Preliminary results are looking good,” says Atakan Ozbek, director of energy research at ABI Research in Oyster Point, N.Y. “A commercially viable fuel cell for automotive applications is sort of the holy grail among developers of advanced technology vehicles. This is headed in the right direction.”

Using PolyFuel's new membrane, so-called PEM fuel cells — or proton exchange membrane fuel cells — would continue to produce electricity by converting hydrogen and oxygen into water.

In this type of fuel cell, hydrogen gas enters the system on the anode side and is forced through a catalyst, often a thin layer of platinum. The catalyst splits each hydrogen molecule into two hydrogen protons and two electrons. The electrons move through the anode to an external circuit, providing electrical power, and eventually return to the cathode side of the cell.

At the same time, oxygen is forced through the catalyst on the cathode side, forming two negatively charged oxygen atoms. The oxygen atoms attract the hydrogen protons through the fuel cell's membrane to the cathode, where they combine with the returning electrons to form a water molecule.

Until now, fuel cell membranes have been based on a perfluorinated material in the same chemical family as DuPont's Teflon, the pots and pans coating, and the so-called “miracle” fabric Gore-Tex. While effective, membranes made with this material — DuPont's trademark on the name is Nafion — don't last very long, are expensive to make, operate within limited temperatures, and require expensive supporting structures to maintain proper humidity and cooling.

PolyFuel's membranes are made of hydrocarbon molecules converted into polymers, or plastics. By forcing the material to self-assemble into structural blocks and conductive blocks, PolyFuel can make membranes that not only are 16 times stronger, but also allow the hydrogen protons to flow more freely to the cathode side of the cell.

Even after PolyFuel develops a commercially viable fuel cell, however, Mr. Balcom acknowledges that other barriers to adoption of the new technology exist. Fuel suppliers would have to learn how to step up hydrogen production learn how to step up hydrogen production and figure out how to transport it to filling stations. Manufacturers would need to determine how best to store the hydrogen inside the car and feed it efficiently to the fuel cell.

Drivers would have to become accustomed to replacing fuel cell membranes periodically, much as they do spark plugs today. And engine makers would have to figure out how to run the engines at temperatures hovering just under the boiling point of water — 212 degrees Fahrenheit — without ever allowing the water in the fuel cell to boil, halting the chemical reaction that makes electricity.

And all that, of course, assumes that PolyFuel's development work continues to go well, says Mr. Ozbek.

“These are, of course, lab results, but I don't want to downsize the importance of what they've accomplished here,” he says. “If they can drive the humidity (requirements) lower and increase the durability then they have a serious case going for them.”

No problem, Mr. Balcom says.

“We're just at the beginning of the development path,” he says. “Our chemists know they can drive it towards the ideal characteristics required to compete head-to-head with the internal combustion engine.”