Challenges of measuring wind at turbine heights
Onshore wind turbines now tower up to 170 meters. As performing measurements at these elevations is expensive and/or cumbersome to install, available lower-height wind speed characteristics are generally vertically extrapolated to the altitude of interest. Extrapolation is done by using the mean wind speed variation with height, also known as vertical wind shear coefficient. Currently, measurement campaigns to obtain a representative wind shear coefficient are extended to a full year to account for seasonal variability.
Investigating shorter measurement campaigns
This study evaluated the feasibility of reducing measurement campaigns to up to three months. Data from 50 European campaigns revealed that autumn and spring campaigns were highly representative, with an average error of only 0.1%. However, errors increased significantly in winter and summer, highlighting the need for corrections.
A method to correct seasonal biases
To address seasonal inaccuracies, we developed a correction method using atmospheric reanalysis data (ERA5) to adjust short-term measurements. For example, applying this correction to a summer campaign reduced the average error on wind shear coefficients from 11.6% to less than 0.1%, with lower uncertainty.
Timing matters for campaign success
While the correction method performed well for summer and winter campaigns, it overcorrected in spring and autumn. This underscores the importance of carefully selecting campaign timing and assessing whether to apply the correction method.
Expert insights for efficient wind shear evaluation
Our renewable energy consultants use this methodology in two specific use cases: (1) to obtain a representative wind shear when extrapolating wind data from lower-height measurements to higher elevations, and (2) to conduct preliminary wind resource assessments when evaluating site viability during early development phases. The tool ensures accurate and representative wind shear data, determining whether corrections are needed to provide project developers with reliable, faster and cost-effective insights.
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