Environmental measurement specialist Vaisala has collaborated with WindSim, a pioneer in computational fluid dynamics (CFD) modeling, on a study that demonstrates how the effects of complex terrain on wind measurements collected by remote sensing units can be mitigated. The collaboration has included the most extensive complex terrain validation of remote sensing data undertaken in the wind energy sector to date. The results establish a methodology for considerably reducing the uncertainty of data collected by the Triton Wind Profiler in complex terrain, opening the door to more effective measurement campaigns in areas of untapped resource. For wind energy developers prospecting at more challenging, off-grid sites such as on ridge lines, hillsides and in heavily forested areas the versatility, maneuverability and size of remote sensing devices means that they offer numerous potential advantages over measurement towers (met towers). Validating the accuracy of a remote sensing system in complex terrain removes one of the few remaining barriers to the widespread adoption of the technology across the industry. Pascal Storck, director of renewable energy at Vaisala, said, While remote sensing devices are increasingly supplanting met towers as the preferred technology for wind measurement campaigns, concerns over the way both sodar and lidar technologies respond to complex airflows have posed an obstacle. Our study with WindSim shows how topographical factors can reliably be accounted for. Vaisalas extensive complex terrain validation study spanned 20 individual sites, each with a collocated Triton Wind Profiler and met mast, collecting simultaneous measurements for a period of 1-4 months. These sites were distributed across the globe and exhibited a variety of local terrain complexity. Using publicly available elevation and land cover data, WindSim configured CFD simulation domains surrounding each collocation site and conducted simulations for a variety of inflow conditions. From these simulations, Vaisala developed correction factors to account for windflow curvature, for each measurement height and wind direction sector. By applying these CFD-based corrections to Triton data, Vaisala found a reduction in the mean wind speed difference between the Tritons and met towers from -1.7% to -0.1%; and in the standard deviation from 2.5% to 2.1%. The correction therefore not only eliminated the overall bias, but also reduced the spread of error among the sites. Dr Arne Gravdahl, founder and chief technical officer, WindSim, said, The accuracy of remote sensing data has widely been recognized as on a par with that of met towers in all aspects except when it comes to operating in complex terrain. Using CFD simulations to adjust Triton data removes this concern, leveling the playing field in terms of data quality, and allowing developers to take full advantage of the Tritons versatility. Our study shows that its a reliable, repeatable methodology, and were looking forward to seeing the impact it has for Vaisalas clients as they pioneer wind development in those parts of the world where the best resource isnt always on flat terrain. Click here to view the full results of the complex terrain validation study.
Helen has worked for UKi Media & Events for more than a decade. She joined the company as assistant editor on Passenger Terminal World and has since progressed to become editor of five publications, covering everything from aviation, logistics and automotive to meteorology. She has a love for travel and property and has redeveloped three houses in three years. When she’s not editing magazines, she’s running around after her two boys and their partner in crime, Pete the pug.