Multi-lidar wind resource mapping in complex terrain
The presentation was given at NREL - Flatiron Campus on October 31, 2019.
Scanning Doppler lidars have great potential for reducing the uncertainty of wind resource estimation in complex terrain. Due to their scanning capabilities, they can measure at multiple locations over large areas. We demonstrate this ability using dual-Doppler lidar measurements of flow over two parallel ridges. The data have been collected using two pairs of long-range WindScanner systems operated in a dual-Doppler mode during the Perdigão 2017 measurement campaign. The lidars mapped the flow along the southwest and northeast ridges 80 m above ground level. By analyzing the collected data, we found that for different flow conditions on average wind speeds are 10% higher over the southwest ridge compared to the northeast ridge. At the southwest ridge, the data shows, depending on the atmospheric conditions, a change of 20% in wind speed along the ridge. For the measurement period, we have simulated the flow over the site using WRF-LES to compare how well the model can capture wind resources along the ridges. We used two model configurations. In the first configuration, surface drag is based purely on aerodynamic roughness whereas in the second configuration forest canopy drag is also considered. We found that the WRF-LES configuration without forest canopy drag usually better predicted the mean wind speed. The implementation with forest drag correlates better with the variations in the measurements but underestimates wind speeds. When compared to the measurements, in the best case scenario WRF-LES results overestimated the wind resources over the southwest and northeast ridges by 6.5% and 4.5% respectively. Overall, this study demonstrates the ability of scanning lidar to map wind resources in complex terrain.