Harrison on Viability

John Harrison continues to produce high-quality papers on a variety of wind-turbine-related topics. Amherst Island, where John lives, is slated for a 75-mw project that is now in the planning stages. In an effort to give the financial backers of such a project something to think about, he looked at the economics of the Amherst project and their underlying assumptions – many of which are unrealistic and uncertain. In summary, there are any number of very plausible (even expected) things that can cause the returns from such a project to go negative.

Financial Viability of the Ontario Wind Energy Generating System

To me, the most important new news from this study was the surprising (at least until you start thinking about it) reduction in Capacity Factor of about 2% per year that wind turbines are subject to. This loss of efficiency is normally hidden behind the year-to-year variability of the winds and the consequent variability of the generator output. John normalized the average wind speed and the consequent output (recalling that it is a cubed relationship) and the loss in CF stands out like a sore thumb. Intrigued, I ran the numbers for Denmark and obtained a fairly consistent 1.5% annual loss. And when you are lucky to start at a CF of 28% (as Denmark did here), 2% per year is a bunch.  Here is the picture of what I got.  The spreadsheet that produced it is available for the asking.


UPDATE  – September 11, 2011.  John has released a similar report customized for Amherst Island.

UPDATE – January 15, 2012.  John updated the Amherst Island version of the report and I’ve reposted about it.  He continues to improve it, to the point where the AI-specific report is has valid cautions applicable to everyone.



4 thoughts on “Harrison on Viability”

  1. I have done a rough calculation for the CF for The Arklow Banks in Ireland and have come up with a similar result. There is an unexpalined drop in CF over 3 years 2008 to 2010 of 5%. I was about to start to determine if similar CF drops could be detected in Danish figures that I have.

    Yours Sincerely

    John Dooley

  2. England also has add a similar drop in 2010, that was explained by a “bad year in wind”, I need to see the more recent stats but I do expect to see it confirmed.

    Like the wings of an airplane, the blades of a turbine get constantly dirtied by bugs. Private pilots clean the wing of their airplane after every and each flight. The bugs change the aerodynamic profile of the blade which make it less and less efficient.
    This is a very serious problem. Either you don’t clean, and suffer an efficiency reduction, or you clean, but the cost over a large farm gets certainly very large very fast.

    Some actually use helicopter for the cleaning :
    Most use platforms that obviously are a dangerous and unsafe method.
    See the brochure http://www.ismhelp.com/pdf/Microsoft%20Word%20-%20new%20balde%20Access%20Brochure.pdf

    Actually there’s one Spanish company that has a much better solution. I don’t want to seem to advertise for them but I just hope nobody get killed falling from one of those obviously dangerous platforms.
    Here it is, there have a mechanic system that crawls along the tower and spreads water that cleans the blade when it runs through it (you just don’t even stop the blade, their movement is used for the cleaning) : http://www.opinno.com/blade-cleaning/

    A second linked problem is that the blades kill birds, but certainly don’t escape unharmed. This time you can actually slightly break the edge of the blade. Accumulate such events, and you absolutely need to repair the blade with some resin. But whatever you do, you won’t get your pristine aerodynamic profile back. Over years, this will accumulate and make the blade into a wearing part.

    But from what I’ve seen reported, it may be that off-shore wind has actually an even worst problem to fight : salt. Salt will slowly deposit itself on the blade. And this time we are talking about something that not only changes the aerodynamic profile, but that’s heavy. Of course the deposit is very thin, but where talking for recent wind turbines of blades that are the size of a A380, and made as light as possible using carbon fiber. Even a small added weight is a big problem for them.

    And to remove the salt you probably needs some serious scrubbing of the blade.

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