Wind Turbine Underperformance Issues Require Cost Effective Solutions
According to a 2021 technical report by NREL, “On average, modern wind power plants in the U.S. underperform their expected annual energy output by 3.5-4.5%.”
There is a litany of potential causes of wind turbine underperformance. Among these are forms of underperformance caused by rotor-disrupted and/or poorly calibrated nacelle-based wind sensors that in turn feed inaccurate wind data to core wind turbine systems.
To date, wind turbine underperformance has been mostly cost-prohibitive. The budget required to utilize incumbent first-rate wind measurement technologies has been, in most cases, higher than the potential revenue generated from optimizing wind turbines’ energy generation.
3rd party wind measurement devices, such as nacelle based LiDARs, can cost 1.5X-2X the potential value of an additional 4.5% of energy produced by a wind turbine with a 2-megawatt capacity. As a result, it is common for operators to defer to inaction and absorption of consequential energy production losses.
In 2018, First Airborne, an Israeli technology company, started developing Windborne™— a proprietary an industry verified aerodynamic payload that deploys from a drone at unobstructed (non-waked) and optimal wind measurement points across a wind farm site.
The robotic system, which conceptually is like a flying wind mast, aims to enhance the economic viability of wind turbine performance testing and AEP recovery efforts due to its mobility and ability to extract wind data without physically interfacing with wind turbines.
Yaw Misalignment Campaign with Northern Texas Based Wind Farm Operators
Starting in August 2023, First Airborne launched a yaw misalignment detection campaign in a wind farm in Northern Texas.
The operators of the 90-turbine wind farm, had concerns that prevalent yaw misalignments across multiple wind turbines on-site were causing significant AEP losses. Preliminary random photography of the wind site displays concerning evidence of misalignment—especially given that the terrain is flat and not prone to complex wind patterns. The image below illustrates how nacelles throughout the wind farm are clearly facing different directions during rotation (wind speed > 8m/s).
Tasked with the problem, First Airborne set out to deploy Windborne throughout predesignated measurement points across the site in order to swiftly detect potential yaw misalignment.
What is Yaw Misalignment?
Yaw misalignment occurs when the nacelle of a wind turbine is not aligned with the prevalent wind direction.
Misalignment can manifest in both static and dynamic forms. Static yaw misalignment occurs when the signal consistently deviates from the actual wind direction. Dynamic yaw misalignment, on the other hand, happens when the turbine is slow to adjust to changing wind directions.
Why is this problem important?
- Power Output Impact: Misalignment directly hinders a wind turbine’s ability to efficiently face and adapt to changing wind directions, resulting in suboptimal power output.
- Component Stress and Lifespan Reduction: Beyond design limits, misalignment places additional stress on vital components. This heightened load may accelerate wear and tear, potentially shortening the overall lifespan of the wind turbine.
First Airborne’s Yaw Misalignment Detection Process
Step 1: Northing Assessments
Prior to measuring yaw misalignments for any of the wind turbines on-site, a northing assessment process is completed for each turbine. Utilizing image capturing drone technology and a reliable reference azimuth, First Airborne takes a set of overhead images for each wind turbine to identify the exact positioning of a turbine’s nacelle within a defined set of time.
These overhead images are then compared with the operator’s SCADA to pinpoint the real nacelle heading of a specific WTG on-site.
For this project, northing assessments were completed for all 90 WTGs.
After each WTG’s real nacelle heading is made available, the nacelle misalignment detection process begins.
Step 2: Wind Data Collection
Once northing is completed, wind data can be collected across the entire wind farm site.
For this specific project, the measurement locations were distilled to 20 measuring point, each point covering 3-5 wind turbine, insuring strong correlations between the Windborne sensor and the tested turbines.
For each measurement point, 90,000 high resolution data samples were collected.
Image Description: Windborne™ gathering wind data at the Trinity Hills wind farm.
Image Description: Windborne™ gathering wind data at a 2X-4X rotor diameter upwind distance from a wind turbine.
Step 3: Analysis
Utilizing the proprietary data gathered with Windborne™ and SCADA data provided by Phoenix Wind Repower LLC, First Airborne’s automated back-end analytics determined the extent to which certain wind turbines were inaccurately measuring wind direction and, therefore, experiencing persistent yaw misalignment. All misalignment detections fulfilled the industry standard statistical significance requirements.
Campaign Results:
According to industry norms, specifically as outlined by Deutsche WindGuard GmbH, a misalignment of up to 5 degrees is regarded as anticipated.
Out of 90 turbines measured:
- 10 of the wind turbines contained misalignments above 6° — 3 of which were misaligned above 8°. This translates to losses ranging approximately between 1.5-2% AEP.
- 5 of the wind turbines contained misalignments ranging between 5° to 6°, This translates to losses of ~1% AEP.
- 8 of the wind turbines contained misalignments ranging between 4° to 5°. Although 4° is less than the 5° misalignment tolerance threshold, addressing these misalignments can still lead to valuable AEP improvements.
Conclusions:
By leveraging Windborne™ technology, First Airborne identified evidence of yaw misalignment for 25% of the wind turbine fleet. Through standard yaw offsetting adjustments, the operators of the wind farm can recover an average of about 1%+ of lost AEP for entire wind farm — with benefits from this additional AEP for years to come. Overall, this campaign is projected to lead to a 4X return on investment within 3 years of implementing changes.
Alex Alpert
Director of North America
