The combined average of these measures is −0.43 ± 0.05 percentage points per year, giving −1.6 ± 0.2% annual degradation. The similarity of results from different methods gives us confidence that the underlying trend is robust: the decline in load factor with age is neither an artefact of systematic variation in wind speeds nor of the continual improvement in technology. Questions do however remain as to the exact form of this degradation, for example whether it is linear, quadratic or logarithmic with age; or how degradation rates are changing over time and whether they will be lower in the future. Access to data from more farms, and a more detailed wind resource assessment for each site will be fundamental to furthering our understanding of these issues.
measures
−0.43 ± 0.05 percentage points per year
percentage points per year
annual degradation
−1.6 ± 0.2%
%