In the realm of wind energy, researchers are continually seeking innovative ways to enhance the efficiency and longevity of wind farms. One such researcher, Carlo Cossu, from the University of Rome Tor Vergata, has been exploring the potential benefits of tilting wind turbine rotors to improve wind farm performance.
Cossu’s recent study, published in the Journal of Fluid Mechanics, focuses on the concept of wake redirection, a strategy aimed at mitigating the negative impacts of turbine wakes on wind farm performance. Wakes are regions of reduced wind speed created downstream of wind turbines, which can decrease the efficiency of downstream turbines and increase mechanical stress, potentially reducing their lifespan.
The study demonstrates that tilting the rotors of wind turbines in a spanwise-periodic array can generate coherent streamwise vortices. These vortices deflect the wakes towards the ground, allowing higher-momentum fluid from above to replace the low-speed wake regions. This process, known as high-speed streaks, can significantly boost the power output of the wind farm.
Cossu’s research reveals that for wind-aligned arrays, substantial power gains can be achieved with positive tilt angles of around 30 degrees. Moreover, these power gains are enhanced when the turbines operate at higher thrust coefficients than in the reference, non-tilted configuration. The study also shows that power gains initially increase with rotor size, reaching a maximum at a rotor diameter of approximately 3.6 boundary layer momentum thicknesses, before decreasing for larger sizes.
Interestingly, the optimal wind-turbine spanwise spacings for maximum power gains are similar to those of large-scale and very large-scale streaky motions naturally amplified in turbulent boundary layers. This finding aligns with previous investigations of passive control of canonical boundary layers for drag-reduction applications.
The practical implications of this research for the energy sector are significant. By implementing rotor tilt in wind farms, operators could potentially increase power output and extend the lifespan of turbines, ultimately improving the overall efficiency and profitability of wind energy projects. However, further research and real-world testing will be necessary to validate these findings and optimize the application of rotor tilt in commercial wind farms.
This article is based on research available at arXiv.