The first widespread application of hydrogen fuel-cell technology might not be in cars but in vacuum cleaners. Industry giant Electrolux said last week that it is close to developing a fuel-cell vacuum that would be lighter than conventional models, much quieter, and, of course, free of a power cord. Big advances in pollution reduction are expected when automakers and energy companies begin using fuel cells on commercial scale, but such changes might be 10 years down the road. In one test project in Portland, methane collected from the decomposing waste from a sewage plant is providing hydrogen to power a fuel cell that creates enough electricity for more than 100 homes a year.