It's a dream that's been pursued for years: Mass-producing affordable hydrogen-powered cars that spew just clean water from their tailpipes. So Shanghai's Horizon Fuel Cell Technologies decided to start small. Really small. This month, it will begin sales of a tiny hydrogen fuel-cell car, complete with its own miniature solar-powered refueling station. The toy is a step toward introducing the technology to the public and making it commercially viable. Though prototype hydrogen cars exist, they're far from practical or affordable. Horizon's H-Racer and fueling station solve those problems on a very small scale. The price: $80 for the set. The toy's fuel cell, like those envisioned for real cars, relies on an electrochemical reaction...that powers the gadget's electric motor. The only byproducts are electricity, heat and water. The fuel is supplied by its alarm clock-sized refueling station. A small electric current, generated by the solar cells, extracts hydrogen from water. With the flip of a switch, the car takes off and runs for 4 minutes on a full tank. At Horizon's headquarters...Wankewycz and former Eastman Chemical Co. colleague George Gu demonstrated prototypes of a hydrogen-powered electric bicycle and a golf caddy they are converting from lead acid batteries to hydrogen power. We're working on the smaller things until the infrastructure is ready," he says. On the Net: Horizon Fuel Cell Technologies: http://www.horizonfuelcell.com