Tue May 9th, 2006 at 11:26:45 AM EST
Or at least, that's what Frits van den Berg concludes from his PhD study on wind turbines in the windfarm in Rhede, Gemany, just across the Dutch border. He will be defending his thesis on 12 May at the University of Groningen.
Translated from the press release (in Dutch):
It is surprising how little windfarm owners know about their "raw material", wind, opines Frits van den Berg. His measurements from, among others, the windfarm in Rhede show that during the night wind can be virtually absent at ground levels while there is a strong wind at greater height. During the day, this effect is not present. Because of this (known metrological effect) wind turbines make more noise during the night than during the day. Windfarm owners have long denied this or played the effect down. Van den Berg: "They base their expected production numbers on the mean wind velocity at a height of about ten meters through the entire year. Yet many wind turbines are nowadays much higher with heights up to eighty meters. At that height, wind can be considerably stronger while at the ground there is less than a breath. Windfarm owners should be able to verify this for themselves: at night the more modern, higher turbines render more energy than during the day."
Although Van den Berg opines further in the piece he is not against the wind industry, he argues for a better acknowledgement of this recurring complaint concerning wind turbine noise and cautions that continuing to evade this topic will risk the wind industry getting a bad rep. With a little digging I found a PDF of Van den Berg's work in English, here.
It's on a site against windfarms, so they probably appreciate the hits, even when I would like to query for further debate and thoughts on this topic to advance wind industry further...