• Is Sheffield wind typical?
    May 01,2013

    Is Sheffield wind typical?

    A recent article in The Times Argus reported the statistics of the first full year’s performance of the wind farm at Sheffield. First Wind Inc. has installed 16 2.5-megawatt turbines that have a maximum capacity of 40 megawatts. The article reported they had an unexpectedly poor production year of 81 million kilowatt-hours, down from their projected 115 million kilowatt-hours, but they reported supplying power to 12,300 homes. Here’s a little more to this story.

    The Sheffield project has a maximum capacity of 350 million kilowatt-hours, but the variability of wind and demand means that First Wind rates the expected actual capacity at 115 million kilowatt-hours or about 33 percent efficiency. By comparison, Searsburg has an efficiency of 19.2 percent. In 2012, Sheffield achieved an efficiency of about 23 percent or about 70 percent of its projected production. The U.S. Energy Information Administration rates average household power use at 11,280 kilowatt-hours, meaning Sheffield actually supplied power to about 7,180 homes.

    The reasons given for the lowered production were lower than expected winds and the inability to load the distribution grid with the produced power. The unexpected lower winds apparently did not show up in their two-year study of wind conditions performed prior to construction. This may or may not be a long-term trend as a result of global warming.

    The distribution grid problem exists when the variable wind causes spikes in power production that exceed demand at that time. These wind-powered surges cannot be matched with rapid response rises and falls in power production from the base load power production facility (nuclear, hydro, coal or gas) so the excess power is simply discarded. This means that even when the wind is blowing, there may be no significant reduction in greenhouse gases produced or any drop in base load production.

    Now you have heard the rest of the story, just to keep everything in perspective.

    Tom Watkins


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