The Dow Chemical Company and General Motors this week launched the second phase of their joint project to prove the viability of hydrogen fuel cells for motor vehicles and possibly for distributed power generation.The project´s single test cell is converting to a plant with multiple fuel cells at Dow´s factory in Freeport, Texas, the companies said Monday. The plant will supply energy for Dow´s Texas operations. GM and Dow are seeking to demonstrate the reliability of fuel cells, the companies said.GM is trying to reduce the cost of fuel cells. A unit large enough to run a car is about 100 times more expensive than a gasoline engine producing the same power. Fuel cells have been used for decades in spacecraft.If Phase II proves successful, the project will transition to Phase III, large-scale commercialization by 2007. Ultimately, Dow and GM could install up to 400 fuel cells at Dow facilities, to generate 35 megawatts of electricity, equivalent to the amount of power needed for 25,000 average sized American homes.