This Lessons Learnt Report outlines the key learnings Meridian Energy Australia has learnt from the period between May 2020 – September 2020.
Lesson learnt No.1: Accurate wind speed extrapolation is critical for LIDAR-based forecasts, in particular within semi-complex to complex topography.
Objective: Other (Use of LIDAR data in forecasts)
Details: The topography surrounding the Mount Mercer wind farm is moderately complex and generally tending towards the South. When measuring the wind field along a conical surface, the sampling altitude of the LIDAR changes considerably according to which sector is being probed. Assuming wind vectors follow the topography, the wind field has to be extrapolated to hub-height before being propagated forward in time to produce forecast.
Investigations showed that the accuracy of the LIDAR forecast is highly sensitive to the methodology used to extrapolate wind vectors to hub-height. In particular, rigorous wind speed extrapolation requires a priori knowledge of the atmospheric stability conditions at the time of forecast and these should be estimated with extreme care.
Implications for future projects: Whenever possible, the forecaster using a scanning head LIDAR should aim to probe the incoming wind field as close as possible to hub height to reduce the uncertainty associated with wind speed extrapolation. Hub height extrapolation should account for atmospheric stability conditions and surrounding topography.