For as long as I can remember, whenever anyone spoke of the prospects for putting hydrogen-powered fuel cell cars on American streets, the number "10" figured prominently in the statement. We were always "10 years away" from having the cars on the streets, 10 years away from making fuel cells doable. Until yesterday.

Yesterday, for the first time, 10 became five, when hydrogen fuel cell innovator Ballard Power (NASDAQ:BLDP) released a statement making a "public commitment" to "demonstrate the commercial viability of automotive fuel cell stack technology by 2010." What that means, Ballard went on to elaborate, is that within the next five years, Ballard is going to prove that it's possible to build a fuel cell stack that can take the internal combustion engine's place in running a car. To fulfill its commitment, the company will need to come up with a stack that has at least a 5,000-hour lifespan (enough to travel about 136,000 miles) before it needs to be replaced, that can operate in minus-30-degree Celsius conditions and produce a satisfactory amount of locomotive power, and that can be manufactured at a commercially viable price.

That last one is key -- because the fact of the matter is that we already do have some fuel-cell-operated vehicles on the road today. But they don't come cheap. In fact, on the same day that Ballard released its announcement, General Motors (NYSE:GM) announced that it has inked a deal with the U.S. Department of Energy (DOE) to build a 40-vehicle fleet of fuel cell cars to demonstrate the technology's commercial viability. This deal will stretch over the next five years (there's that new number again) and cost a total of $88 million, with half coming out of GM's pocket and the DOE (that's you and me, my fellow taxpayer) anteing up the other half.

Break out your handy-dandy calculator now, and you'll see that each of these vehicles costs a whopping $2.2 million. "Commercially viable" for Messrs. Gates and Buffett, perhaps, but for the rest of us -- we're not quite there yet.

In a related development, DaimlerChrysler (NYSE:DCX) signed its own deal with the DOE yesterday. Daimler entered into a (surprise!) five-year project, in which the German-American automaker will invest $70 million to further build out its 100-strong fleet of fuel cell vehicles and collect driver feedback on how to make a better hydrogen-powered mousetrap.

It's been a long time coming, but we just may be approaching the brighter end of this long fuel cell tunnel.

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Fool contributor Rich Smith has no position in any of the companies mentioned in this article.