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.
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.