John Harrison was the first person (at least in public) to notice the year-to-year degradation of the output of Ontario wind turbines. Then I followed up with Denmark and Mars Hill, and Paul-Frederick Back chimed in with more Denmark. While our numbers vary, and none of us is completely happy with the accuracy of our results, there’s little doubt remaining that the efficiency of a wind turbine decreases, sometimes fairly dramatically, over time.
John’s latest effort is another look at Ontario, now with another year’s data. His new numbers show a Capacity Factor decline averaging 1.1% per year, down from his earlier ~2%. His summary graph:
His second major point was that Capacity Factors were increasing with newer turbines. The newer turbines are sometimes called “high efficiency” but that is a misnomer. The increase is due to larger diameters and swept areas being able to get more energy out of slower winds (and less out of higher winds, which don’t occur so often). The actual efficiency of doing so at any particular wind speed hasn’t changed. I also covered this in my maturity posting, and John’s work is consistent with what I found.