Shear Extrapolation by David Matson Allen Becker V-Bar, LLC - (PPT)

摘要

Uncertainties are a part of wind resource assessment and will not disappear. Wind shear represents an important part of the evaluation process, with hub height wind speeds extrapolated from what we know of winds at lower levels. Uncertainty in shear calculations is one of the largest contributions of all the uncertainties we deal with regularly. Other uncertainties include, but are not limited to, sensor accuracy, long-term reference site period of record and quality, reference versus onsite speeds, and turbine micrositing. The ideal solution would be to always measure winds at hub height, but this is more expensive and not always practical. In the future, as turbine size increases, turbine hub heights will increase. Measuring winds at hub height will become more important, and continued efforts are required to reduce this large uncertainty. Until hub height measurements are made, sensors should be placed at well-spaced intervals, starting 10 meters above ground level, or 10 meters above effective tree height.