Methods for long-term correction in a post-construction energy yield analysis

摘要

Post-construction energy yield analyses are useful for re-financing and when a wind farm is going to be sold. The total uncertainty in a post-construction yield analysis is typically half of that in a pre-construction yield analysis [1]. The long-term adjustment of the measured power is one of the major tasks in the post-construction yield analysis. There are different methods available to do the long-term adjustment and the most suitable method depends on the quality of the operational data. The results based on four methods from two wind farms have been compared. The wind farms are located in areas affected by icing during the cold part of the year. This will cause a seasonal dependence in the data availability that is affecting the results. This also mean that some of the conclusions drawn might be valid mainly for wind farms were icing occur regularly. It is important to select the most proper method(s) in a post-construction energy yield analysis. The uncertainty in the long-term correction depends on the length of the operational period and by the used methods. By calculating the annual energy production (AEP) for different operational periods using several methods it is possible to estimate this uncertainty. The long-term adjustment methods used in this analysis can be divided into two different categories, "Historical power curve methods" (HPCM) and "Index methods" (IM). Common for all methods is that only data from when turbines are operating in full-performance should be used. Full-performance is defined as "The WTGS is operative and generating according to design specifications with no technical restrictions or limitations which affect generation." [2].