General Motors and Toyota are in talks about collaborating on a fuel cell partnership, according to news reports this week.However, researchers conclude in an article to be published in June that it could take "several decades" to overcome daunting technical challenges standing in the way of the mass production and use of hydrogen fuel cell cars.The article, to appear as the cover story in the June issue of the AIChE Journal published by the American Institute of Chemical Engineers, notes that hydrogen fuel cell "success is not certain." The article says that hydrogen's "wide-scale use is laden with potential technical, economic and societal impasses." In case fuel cells never do become practical for cars, the researchers conclude, it would be wise for the nation to "maintain a robust portfolio of energy research and development" in other areas.Current obstacles to a fuel-cell economy include:--the high cost of power. Today's fuel cells generate power at a cost of greater than $2,000 per kilowatt, compared with $35 per kilowatt for the internal combustion engine.--operating life. Fuel cells in cars last less than 1,000 hours of driving time, compared with at least 5,000 hours of driving time for an internal combustion engine.--vehicle cost. A fuel-cell car built with today's technology costs about $250,000.--storage and transportation. Hydrogen is a light gas, meaning it needs more space than a normal gas tank to provide the same amount of power to an engine. Transporting hydrogen would be more expensive as well. --method of hydrogen production. Industry now extracts hydrogen from natural gas, oil and coal. These fossil fuels will eventually run out and pose potential environmental hazards.--infrastructure. Plants dedicated to hydrogen production, as well as filling stations, would need to be built at a cost of billions of dollars. Who would foot the bill is not certain."I believe we can probably solve the technological problems related to making hydrogen fuel cells practical as a replacement for the internal combustion engine, but it won't be easy and it likely won't happen very soon," said article co-writer Rakesh Agrawal, Purdue University's Winthrop E. Stone Distinguished Professor of Chemical Engineering. "An optimistic prediction would be that a significant number hydrogen fuel cell cars will be entering the marketplace around 2020, and by 2050 everybody will be driving them."The article was written by Agrawal, Martin Offutt, from the National Research Council, and Michael P. Ramage, a retired executive from ExxonMobile Corp.