Due to the relative high uncertainty in pre-construction yield assessment there is often a difference between the production estimated in the pre-construction analysis and the realised production of a finalized wind farm. The post-construction yield analysis will therefore be the best long term estimate of annual production. It is also a great source of additional information about the wind farm. The analysis will identify if the wind farm performances as expected. Often problems such as low turbine performance, yaw misalignment, higher than expected ice-losses or large forest effects are captured, and in some instances mitigation efforts can be put in place.
Post-construction yield assessment is typically conducted based on site measurements and wind farm SCADA data, but the measured production and turbine performance must also be related to a long term context. This is achieved by using long term mesoscale data time series and CFD downscaling.