Gm Enters Next Phase Of Fuel Cell Program - Brief Article - Statistical Data Included

Automotive Industries,  May, 2000  by John McCormick

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Dr. Erhard Schubert says the preferred candidates for on-board fuel processing include reformulated gasoline with low sulfur content, naptha-like fuel, or synthetic fuels produced from natural gas.

Claiming to have produced the most advanced "operational" fuel cell to date, General Motors recently fleshed out its alternative propulsion strategy. While the Precept diesel-electric hybrid concept revealed earlier this year in Detroit demonstrated the basic large sedan package suitable for the U.S. market, the Opel Zafira-based vehicle unveiled at the Geneva Auto Show puts fresh emphasis on reducing the size of the whole powertrain.

Compared to a previous European-focused GM fuel cell project vehicle, which was also based on the Zafira compact minivan, the latest version differs in several important respects. First, the Zafira's hydrogen is stored in liquid form in a 17 gallon (75 liter) insulated stainless steel tank, located under the rear seat. The earlier concept derived its hydrogen from an on-board methanol reformer.

Most importantly the fuel cell stack itself has been reduced in size and is now claimed to be 15% smaller than rivals. The complete stack -- comprising 195 single cells -- and the 55 kW, three-phase AC motor, weigh just 150 pounds (68kg). The whole assembly fits in the Zafira's stock engine bay.

The location of the liquid hydrogen tank raises the rear seat height 30 mm. This also means the cargo area loses its foldaway seats and sits 100 mm higher. But otherwise, Opel says, the Zafira's functionality is unimpaired, and the company adds that computer crash simulations prove the tank's location would not be a safety hazard in an accident.

Overall the five-seat project vehicle weighs 300 pounds more than the standard Zafira's 3,135 pounds. With 185 lb-ft of torque (251 Nm) available from standstill, Opel claims the fuel cell Zafira will accelerate from zero to 62 mph in 16 seconds. A top speed of 90 mph and range of 250 miles (impressive for the vehicle's size) are claimed.

In conjunction with the Zafira project, GM fuel cell experts in Germany and Detroit report important breakthroughs in dealing with the fuel cell's inherent cold start challenges.

Repeated starts at minus 20 C have been achieved with full power delivered in 30 seconds. Tests are now being carried out at minus 40 C.

According to Dr. Erhard Schubert, director of Opel's Global Alternative Propulsion Center in Russelsheim, Germany, the Precept and the latest Zafira concepts highlight the fact that GM is concentrating on hydrogen as the fuel of choice.

"We are convinced that long term there will be hydrogen as a retail fuel. We do not know how long it may be, possibly 10 years, or 20 or 30. One could easily build up a localized infrastructure for hydrogen in Japan, for example, or in certain areas in Europe or the U.S., although not nationwide in America."

Schubert adds that GM favors certain fuels for on-board reforming systems, as an intermediate step before a hydrogen infrastructure can be established.

"We have internally decided what we would prefer with respect to on board processing fuel. We are not in favor of using methanol for large-scale applications; it is not a problem for a fleet operator with a closed environment. But as a retail fuel at a public filling station we have concerns with toxicity, and the fact that oil companies would need to invest in expensive new filling equipment. It also would mean that the companies would not want to invest quickly afterwards in hydrogen filling stations. So it would delay our vision for hydrogen.

"Our strategy is to use the existing infrastructure as far as possible," he continues, "so our preferred candidate for on-board processing is gasoline-like fuels -- for example, reformulated gasoline with low sulfur content, a naptha-like fuel, or maybe synthetic fuels produced from natural gas. These are the candidates which allow us to promote fuel cell technology, live with it and in parallel, work out a long-term solution to come closer to our hydrogen vision."

Schubert says GM is still working on the technology for on-board gasoline reforming. "We know exactly what we have to do to get it but we think it's better to work a little bit longer on the fundamentals. In this way we can find answers to questions of dynamic behavior; how can you handle heavy load changes? How can you handle impurities in the gasoline fuel processing system? To have a total sulfur-free fuel is a tough challenge, so we need to concentrate on whether we can live with fuel with between five and 10 ppm (parts per million) sulfur."

The current Zafira fuel cell is the most operational yet, states Schubert, because its "systems architecture is better and its stack performance is superior to its rivals." In the future, the stack will become even more compact, he promises.

COPYRIGHT 2000 Cahners Publishing Company
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