You may not be aware of this but across America each year thousands of birds of prey are killed at wind farms. The public perception of wind turbines is that of slow moving blades turning in the wind on a ridge line. The power and danger of the prop design wind turbine is not well understood. Probably the hardest aspect for the public to grasp is that of "tip speed." The killer of eagles and all birds at wind farms is blade tip speed. This is what kills and this is what the wind industry does not publicize or put in their environmental documents.

The potential for growth, most analysts argue, is clear. But bottlenecks and political setbacks, not to mention technological glitches, will create many bumps in the road ahead. Indeed, fears that the most euphoric investors were overlooking such obstacles seem to have contributed to a sharp fall in clean-energy stocks earlier this year-although they have since recovered much of the lost ground. Such jitters caused several green-energy firms to cancel planned flotations. “There’s legitimate debate about a couple of segments,” says Keith Raab, boss of Cleantech Venture Network. In some instances, valuations accorded to firms with no profits-and little chance of making any soon-were reminiscent of the excesses of the dotcom bubble. As Douglas Lloyd, of Venture Business Research, puts it, “There’s too much money chasing too few opportunities. How is it possible that this many solar companies are going to succeed? They’re not.”