We’re surrounded by inexhaustible clean-energy sources—the sun, the wind, the ocean, plants, atoms, the earth’s core—but the technology and economic rationale for tapping them have lagged behind our imaginations. The world’s insatiable and destructive appetite for energy is now making some of the more far-fetched clean-energy concepts seem increasingly plausible and necessary. Here we survey six innovative energy technologies in various stages of development. Some of these ideas have been tinkered with by scientists and entrepreneurs for decades; others moved from drawing boards to pilot projects only recently. All have serious backing and profound potential—and none are a sure bet.

High Winds
 
The Idea
Conventional wind turbines stop when the wind dies. Turbine-bearing balloons or rotors could intercept powerful, reliable winds 1,000 to 15,000 feet up.
 
Key Player
Ottawa-based Magenn Power expects to ship the world’s first commercial high-altitude turbine—a 60-foot-diameter helium-filled blimp—by 2010.