If you want to provide off-the-grid power for your own home, there's only been one solution: solar panels. Wind power is usually deployed on a utility-scale, in vast farms of mighty turbines that feed directly into the grid. That's a scale that helps explains why more than 10,000 MW of wind power were installed in the U.S. in 2009. Solar has always been the choice for homeowners who want to stop paying electricity bills and start generating their own juice.
But if wind can do big, it can also do small — and it does rooftops as well. The startup Windtronics is developing mini-wind turbines that can be installed on any flat root, either alone or in larger arrays. Each turbine measures about 6 ft. in diameter and looks like a large, circular window fan, but it can generate an average of 1,500 KW/h a year, with more or less depending on wind strength. And unlike utility-scale turbines, the Windtronic turbine contains no rotating gearbox to generate electricity, and is thus much quieter. In an ordinary wind turbine, the blades moves the gears, the gears turn a generator, and the generator creates electricity. With a Windtronics model, the blades are equipped with magnets at the tips and are enclosed in a wheel that contains coiled copper, so the entire turbine is an electric generator. That makes the Windtronics turbine silent — something your neighbors will appreciate.