Biases in preconstruction estimates of wind plant annul energy production

Abstract. Estimating the energy yield of a wind plant during the preconstruction phase is an historically difficult task, even with industry improvements in these estimations. We build on prior research comparing the realized energy production of wind plants and their estimated annual energy production (AEP) P50 values (median energy production), using owner-provided energy production and losses. Similar to prior studies, we found a slightly increasing bias of overestimating median energy production (6.9 % to 6.5 % as opposed to 6.7 % to 5.5 %). In addition to assessing AEP P50 bias, we compared both the 1-year and long-term AEP P90 and uncertainty energy yield assessment (EYA) estimates to the observed long-term corrected energy production. We found that neither the EYA uncertainty nor the P90 are conservative enough compared to the observed distribution of prediction errors, suggesting significant room for improvement in the EYA process.