Membrane Breakthrough for Fuel Cells

With oil near $50 a barrel, alternatives to gasoline are attracting more attention – including fuel cells, devices that convert hydrogen into electric current with no waste products except heat and pure water.

By MATTHEW L. WALD

Fuel cells have found their way into power systems for laptop computers and into many experimental cars. The main drawback to automotive use of fuel cells, though, has been their cost, which at $100,000 can be 25 times the $4,000 for a gasoline engine of equal power. Lately, some companies, including Honda, have been trying to come up with cheaper versions of the most expensive part of a fuel cell: the membrane that takes the hydrogen fuel and separates it into protons and electrons.
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This morning, a California company, PolyFuel, plans to announce that it has achieved a breakthrough in fuel-cell membranes by using an alternative material: a hydrocarbon that it says costs only about half as much per square meter.

Compared with the fluorine compounds that are the most commonly used for membranes in fuel cells now under testing, PolyFuel says that hydrocarbon membranes allow production of more electricity per square centimeter of membrane. That could mean that a fuel cell could produce the same power as a fluorine-membrane version, but would be smaller and lighter, further adding to efficiency, according to the company.

PolyFuel is quick to say that it has not moved the fuel cell to the point of commercial viability, but now hopes to be closer to that goal. "We’re on a great trajectory here to continue to improve state of the art," said Jim Balcom, the company’s president and chief executive.

Hydrocarbon membranes can also run under a wider range of temperatures, and thus allow better performance, he said. But he acknowledged that other drawbacks to fuel cells would still need to be resolved – including the logistics of producing hydrogren and transporting it to electric-car filling stations. The hydrogen molecule is so small that it would escape through the cracks in the pipes used for natural gas. And it is so light that it must be pumped up to extreme pressures to transport more than a few pounds by tanker truck – requiring more expensive pumps and tanks than are currently in use.

While some other experts say they are skeptical of some of PolyFuel’s claims, a variety of companies, including Honda, which builds prototype fuel-cell cars, are doing work in the area. Gore, the chemical company, has done work on membranes that include hydrocarbons.

The dominant membrane for the fuel cells now in use is a fluorine-based DuPont product called Nafion, which was developed for use in the chemical industry. It is chemically related to Teflon, which DuPont makes. Nafion and other membranes look like plastic food wrap, but are thicker.

According to Mr. Balcom, Nafion will let enough protons slip through to generate about 6.5 kilowatts a meter, but his membrane will generate current of more than 7 kilowatts. (A kilowatt – a thousand watts – would run a single window air-conditioner. A car would require 50 to 75 kilowatts.)

Honda demonstrated a fuel-cell car with a hydrocarbon membrane in Japan in October 2003, according to Ben Knight, vice president for research and development of Honda’s American subsidiary. It has 12 such cars on the road in California and plans to put one in the Northeastern United States soon. A hydrocarbon membrane functions well at temperatures slightly below zero degrees Fahrenheit, he said. Fluorine-based membranes can produce very little power at such low temperatures.

In addition, it can tolerate temperatures near the boiling point, substantially hotter than the fluorocarbon membrane, both men said. This is important because fuel cells generate heat that must be dissipated, and getting rid of heat from a system at 200 degrees is easier than cooling off a device that is already closer to the temperature of ordinary air.

Mr. Balcom said that hydrocarbon membranes also require less humid air, allowing for simpler equipment within the fuel cell.

Skeptics of some of PolyFuel’s claims include Scott G. Ehrenberg, the chief technology officer of Dais-Analytic, a Florida maker of hydrocarbon membranes. He said that operating the membranes too close to water’s boiling point risked surpassing that point – as when a driver quickly accelerated. If the water turned to steam it would tear holes in the membrane, he said.

But he acknowledged the economic importance of cheaper membranes because they can represent nearly half the cost of the fuel cell. In a car, he said, the membranes would require replacement every year or so, the way existing cars require oil and spark plug changes.

Mr. Ehrenberg suggested another advantage to hydrocarbon membranes: they are already mass produced. His company sells millions of square feet of hydrocarbon membranes every year, he said, not for fuel cells but primarily for use in raising the efficiency of commercial air-conditioning systems.

In a commercial building, the ventilation system draws in warm, moist air, chills and dries it, and pumps it inside, and exhausts air that is cool and dry. With a hydrocarbon membrane between those two air flows, the dry air on its way out can suck humidity out of the fresh air on the way in, reducing the workload for the air-conditioner, Mr. Ehrenberg said.

People pursuing hydrocarbon membranes as a cost-cutting measure are "barking up the correct tree," he said.