Calculating TI: a key challenge for the wind energy sector
Atmospheric turbulence, characterised by turbulence intensity (TI), influences the fatigue design of wind turbines and the modelling of wake effects. The consequence is an increase in CAPEX and, therefore, a rise in LCOE. To reduce estimation errors, we have developed TwinDAR©, an innovative solution that evaluates TI from lidar measurements. This approach combines the variance method with a TI reconstruction algorithm developed by France Energies Marines. Applicable to both onshore and offshore wind, our methodology ensures improved component design.
A unique solution for assessing TI using profiling lidar
The variance method
Profiling lidars present three inherent sources of error in turbulence intensity measurements. These errors limit the reliability of the classical TI calculation method when device measurements are used without correction. To overcome these limitations, we developed the variance method, a major advancement that corrects two of these errors: inter-beam effects and instrumental noise. To be applicable in all wind directions, this method requires at least six beams. These can be obtained either from two Vaisala WindCube v2.1 lidars positioned at 45° (10 beams in total) or from a six-beam Lumibird lidar.
TwinDAR© for floating lidar systems
In offshore conditions, a fourth source of error appears: buoy motion. To address this, we developed a spectral motion-correction method. Applied as a preliminary step to the variance method, it ensures reliable turbulence measurements at sea.
Our associated service offering
Our experts support you at every stage to define and deploy a methodology for calculating turbulence from lidar measurements.
- We configure lidar positioning
- We supervise data acquisition
- We analyse the data using our TwinDAR© TI reconstruction algorithm
Our experience at your service
- We have seven years of experience developing a unique methodology dedicated to calculating TI from lidar measurements for both onshore and offshore wind.
- Our innovative approach has been developed through major national and international projects.
- Our operational and validated TI reconstruction algorithm significantly reduces calculation errors.
The benefits of our support
Improved TI calculation
Our solution enables a 35% reduction in MRBE* and a 40% reduction in RRMSE** for TI measurements compared with the classical method.
*MRBE : Mean Relative Bias Error
**RRMSE : Relative Root Mean Squared Error
Improved component design
TwinDAR© enables performance optimisation, cost reduction, and increased system reliability.
Reduced CAPEX and LCOE
Our solution reduces both CAPEX and LCOE. It improves project profitability and strengthens competitiveness in the market.
A tested and proven methodology
The variance method, applied to thirty days of measurements from a dual Vaisala WindCube v2.1 lidar system installed on the Fécamp mast, was compared with the traditional method. The variance method reduced MRBE* by 35% and RRMSE** by 40% compared with the classical approach. It therefore offers greater reliability and a more robust basis for project.
*MRBE : Mean Relative Bias Error
**RRMSE : Relative Root Mean Squared Error
