Wind Farms Often Don’t Produce as Much Energy as Advertised: Report

A new study from the John Muir Trust–not the sorts who would attack wind farms just for the fun of it–debunks five important industry claims.



Ethonomic Indicator of the Day: U.K. wind power only reached 21.14% of capacity in 2010.

As interest in renewable energy grows, wind power companies are rushing to build giant installations; it sometimes seems that a new “biggest wind farm ever” arrives every month (the most recent one is in Germany, to replace all their scary nuclear power). But wind farms of all sizes may not produce as much energy as advertised, according to a new report (PDF) from the John Muir Trust. These are not the kind of people who are going to attack wind farms just for the fun of it. The report examines five common assertions of the wind industry–and then debunks them all, using stats from the U.K.. Below, the assertions, and why they don’t make sense.

  • Wind turbines will generate on average 30% of their rated capacity over a year. Using publicly-reported data from November 2008 to December 2010, the John Muir Trust analysis shows that the average output from wind in the U.K. was just 27.18% of capacity in 2009, 21.14% of capacity in 2010, and 24.08% between November 2008 and December 2010.
  • The wind is always blowing somewhere. Actually, it isn’t, at least if the report’s statistics are to be believed. There were 124 times between November 2008 and December 2010 when total generation from wind farms feeding into the National Grid measured less than 20 MW. The capacity for these wind farms was over 1,600 MW. That’s for the entire country.
  • Periods of widespread low wind are infrequent.  Again, nope. The average frequency and duration of a “low wind event” (defined as an output of 20 MW or less) between November 2008 and December 2010 was once every 6.38 days for 4.93 hours at a time.
  • The probability of very low wind output coinciding with peak electricity demand is slight. During the four highest peak electricity demand periods of of 2010, wind output was was never higher than 6% of total capacity. Not so helpful.
  • Pumped storage hydro can fill the generation gap during prolonged low wind periods.  If all four U.K. pumped storage hydro plants ran at the same time at full capacity, the stored water would run out in a day.

None of this means that wind power should be abandoned. It does mean that certain assertions (i.e. “so-and-so’s gargantuan wind project will produce enough power for 300,000 homes”) should be scoffed at. This report also confirms what we already knew: energy sources have to be diversified–covering the planet in wind turbines would leave us in the dark, at least part of the time.

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Read More: How Wind Farm Technology Can Be Improved

About the author

Ariel Schwartz is a Senior Editor at Co.Exist. She has contributed to SF Weekly, Popular Science, Inhabitat, Greenbiz, NBC Bay Area, GOOD Magazine and more