A: At the moment, small wind systems near buildings seem to have a larger market penetration. One of the new entrants to the small wind market is Edinburgh-based Renewable Devices Ltd, maker of the Swift rooftop wind energy system. The 'slow' turning five-blade rotor, has an unusual patented ring diffuser, which the company claims minimizes noise. Swift, of Scotland, has installed some model turbines on UK rooftops such as rooftop turbines installed at each of five Fife Primary schools in their 2005 pilot, as well as in Malawi and Japan.

Mike Bergey, President of Bergey Windpower Co. of Norman, OK states, "The plain facts are that roofs weren't designed for wind turbines and the wind over roofs is hard on a wind turbine. It's the hardest and worst place to put a wind turbine".

Southwest Windpower (Flagstaff, AZ) Vice President Andy Kruse was more sanguine, "There are conditions where a roof top mounted wind generator can work. However, like solar, an improperly mounted wind generator can be worthless or worse, cause damage to the roof. A wind generator must always be mounted on the upwind side of the structure and if at all possible more than 10' above the roof. Structural engineering must be completed on any building where a wind generator above 1kw is installed."

Since we have cellular towers and HVAC units on roofs, undoubtedly wind systems will migrate there too - but challenges relating to roof structure, noise, and building codes - all pose impediments for fast market penetration.

- Scott Sklar