Lidars Lifted: The Østerild Balconies Experiment

As the share of variable generation wind power plants increase within electrical grids, we discover a rising need for the improvement of energy forecasts with which to schedule and regulate transmission systems. Forecasts on very short time scales (here defined as 15 minutes and less) are largely statistical and physical approaches which rarely outperform simple persistence (reference) models, (C. Monteiro et al, 2009). Errors in predicted vs. actual energy production, along with failures to correctly forecast the arrival and magnitude of ramp events, contribute a significant uncertainty to the real-time operation of balancing markets and operator level windfarm control.

Scanning lidars such as the DTU WindScanner have the ability to synchronously measure wind fields at distances of up to 7km. In the 4 month long Østerild Balconies experiment in North-Western Denmark, two WindScanners were mounted to masts 4.25km apart and raised to 50m and later 200m AGL in order to measure upwind across a flat horizontal plane. Coordinated PPI, or sector scans were performed on both scanners with an opening angle of 90 degrees. The centre intersecting line is thus collocated in both time and space, providing transect measurements of wind speed and direction upstream of the lidar.

Both general observations and data from the Balconies experiment are presented, including an investigation into the suitability of utilising the upstream measurements as a real-time, very short term wind forecasting system.