Wind Turbine Wake Mixing via Dynamic Blade Pitch Control
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Solution Overview
Problem
Wind turbine arrays face efficiency losses due to the wake effect, where downwind turbines operate at reduced efficiency, typically 75% of nominal performance, and spreading turbines out to increase efficiency compromises land use and economies of scale.
Innovation Solution
Manipulating the induction factor of wind turbine blades by adjusting pitch angle and tip speed to increase turbulent mixing in the wake, using techniques like cyclic pitching, permanent pitching, and yaw variations to synchronize blade rotation behavior across multiple turbines, allowing closer spacing without sacrificing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If wind turbines are spaced closely together to maximize land use and economies of scale, then land utilization and construction costs improve, but the wake effect reduces the efficiency of downwind turbines to 75% of nominal performance
Solution Approach 1:
The patent applies dynamics by making the blade pitch angle variable rather than fixed. The control system dynamically adjusts the pitch angle of blades on upwind turbines based on their position relative to downwind turbines, creating time-varying wake patterns that reduce shadow effects and improve overall array efficiency while maintaining close spacing
Solution Approach 2:
The patent implements periodic action through cyclic pitching, where the pitch angle of turbine blades is varied periodically during rotation. This creates oscillating wake patterns that enhance turbulent mixing and accelerate wake recovery, allowing downwind turbines to access higher velocity wind and improving array productivity without increasing land area
2Productivity
If wind turbines are spaced farther apart to increase the efficiency of individual turbines, then wake effects are reduced, but land use increases and economies of scale are compromised
Solution Approach 1:
The patent changes physical parameters of blade operation, specifically the pitch angle and tip speed ratio. By optimizing these parameters dynamically based on turbine position in the array, the system enhances wake mixing and reduces shadow effects, enabling closer spacing without sacrificing individual turbine efficiency
Solution Approach 2:
The patent applies different pitch angle settings to turbines based on their local position within the array. Upwind turbines use different pitch strategies than downwind turbines, with settings optimized for each turbine's specific location and wake exposure, thereby maximizing overall array efficiency on limited land area
3Productivity
If the pitch angle is increased to reduce the induction factor and wake effects, then downwind turbine performance improves, but the power capture of the upwind turbine decreases
Solution Approach 1:
The patent uses periodic variation of pitch angle during blade rotation rather than a constant high pitch angle. The pitch angle is modulated cyclically, creating time-varying induction factors that enhance wake mixing while maintaining adequate power capture on average, resolving the trade-off between upwind power and downwind performance
Solution Approach 2:
The system dynamically adjusts pitch angle in real-time based on operating conditions and turbine position. This dynamic control allows the upwind turbine to optimize its power capture while simultaneously creating wake conditions that benefit downwind turbines, balancing the competing objectives through continuous adaptation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach shortens the relaxation length of the wake, enhancing the efficiency of downwind turbines and overall array performance by increasing kinetic energy transfer within the wake, thereby improving annual energy production without requiring more land or infrastructure.
Implementation Method 1
manipulating the induction factor for a rotor to increase the turbulent mixing process in the wake of a wind turbine
Implementation Method 2
Wind turbine arrays (i.e., multiple wind turbines arranged into wind parks) are becoming an increasing popular technique for generating electricity from wind energy
Data Source
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AI summary
Embodiments of the present invention provide methods and apparatus for increasing turbulent mixing in the wake of at least one wind turbine. Doing so, increases efficiency of a wind turbine located in the wake by transferring energy to the wake that was lost when the wind passed through the upwind turbine. Turbulent mixing may be increased by changing the induction factor for a rotor by, for example, altering the pitch of the blades, the RPMs of the rotor, or the yaw of the nacelle. These techniques may be static or dynamically changing. Further, the different induction factors for a plurality of wind turbines may be synchronized according to a predetermined pattern to further increase turbulent mixing.