| Authors | K. Boorsma |
| Journal | ECN |
| Year | 2015 |
| Link | https://publications.tno.nl/publication/34629334/4v9P5I/e15042.pdf |
| Keywords | Wind farm flow control, Active wake control, Field Campaign, Experiment |
This report gives a description of part of the work done within the framework of the FLOW project on Active Wake Control. Hereto, available field measurements at the ECN wind turbine test site EWTW are analyzed. The report is a follow up of, and largely based on a previous report on this topic, now extended with data from all available turbines in a row.
An increase in combined power is observed for the wake situation, i.e. when the downwind turbine is located downstream of the upwind located turbine. This increase amounts to roughly 8% for a 2° pitch angle, and is limited to the optimum tip speed ratio regime. It should be noted that this figure holds for this row of turbines only and is not necessarily representative for a farm configuration. A quantitative comparison of the different pitch angle settings is hampered by the limited size of the datasets and the fact that the turbulence intensity is not equal for the different configurations. In addition to that, the resulting power of the waked turbines will not only be influenced by the the lower incident wind speed, but also by a different tip speed ratio and corresponding Cp due to the control configuration of the turbines under consideration.
For the loads, presented in terms of flat- and edgewise fatigue equivalent blade root moments, the effect of pitch angle adjustment is as expected mostly present in the flatwise component. Reductions in the order of 10% for the downwind turbine are measured at a 2° pitch angle of the upwind turbine, which occur for the higher wind velocities. As for the power results, a quantitative comparison of the differ- ent pitch angle settings is hampered by the limited size of the datasets together with variations of the turbulence intensity.
To reduce the standard error of the field data and correct for turbulence intensity variations, it is recommended to obtain more measurements. To increase the available data for pitch angle configurations, it would be beneficial if the wind turbines can be operated at a specified pitch angle for a limited time period. Furthermore it is recommended to extend the results from the current row of turbines to a representative farm configuration (number of turbines and their respective distance). To come to a conclusion on the overall benefits of the active wake control concept, a large wind farm experiment seems to be the way forward.