Readers will no doubt recall the study by Gordon Hughes, which suggested that wind farms are wearing out much more quickly than previously thought. This was the subject of a bit of to and fro at BH the other day, when Prof David Mackay, the chief scientist at DECC, appeared in the comments to dispute the findings. There were some further developments at around the same time, which I have been meaning to post since before Christmas.
At around the same time he appeared in the comments at BH, Prof Mackay published a more detailed rebuttal of Hughes at his own blog, which he said showed that Hughes' results were spurious. Hughes' model has parameters for the age-related performance of the wind farm, one for the windiness of the place in which it is located, and another to relate its performance to other windfarms. Mackay's case is that Hughes' model is non-identifiable, which means that the fit to the data is arbitrary: Hughes could, according to Mackay, explain the data say with a fast decline in performance and an increase or windiness, but could also do it with a slow decline in performance and a decrease in windiness. This point was disputed by Hughes.
The following day the Renewable Energy Foundation published some background, explaining that the two sides had in fact been discussing the issue since the original Hughes paper appeared in 2012. Hughes had apparently met with Mackay and had at that time apparently persuaded him that the model was in fact identifiable. Mackay had then shifted position somewhat, claiming only that the decline in performance was overstated (he suggested 2% per annum compared to Hughes' 5%). However, by May Mackay had apparently reverted to his earlier position, namely that Hughes' model was non-identifiable.
The REF's summary of the story to date ended with this strikingly robust statement:
Professor Mackay has made considerable efforts, first to persuade us to withdraw Professor Hughes’ paper, and now publicly, and on dubious grounds, to discredit work which is obviously original and draws attention to a previously undiscussed phenomenon, the decline in load factor over time, that was not acknowledged, for example, in the Department of Energy and Climate Change’s own levelised cost estimates for wind power. This is extraordinary behaviour for a Chief Scientific Advisor to government. Rather than shooting the messenger, Professor Mackay might more fruitfully be advising government on how best to ensure that consumer gets better value for their subsidy, and that we present a more economically compelling example of the low carbon economy to the developing world.