Wind Turbine Radar Interference
Wind turbines, like all structures, can interfere with communication or radar signals when these signals are interrupted by the turbine’s tower or blades. For example, wind turbines can cause electromagnetic interference and affect TV and radio reception. Such interference is infrequent and typically straightforward to mitigate by using satellite TV or wireless cable TV. The interaction of wind turbines and navigational or defense radar signals, however, is more involved and is the subject of considerable recent attention.
During the project development phase, wind developers retain companies with expertise in modeling these signals to assess and mitigate potential problems. Federal agencies offer tools to assist with the process.
Relocating some of the planned turbines is one approach to mitigating signal interference. Radar interference can often be mitigated by working with the Department of Defense (DOD) and the Federal Aviation Administration (FAA) to determine how to change turbine heights, location, or sizes. Making hardware or software alterations to radar stations is another option.
Radar, TV, and Radio Signal Interference
Wind turbines can cause electromagnetic interference and affect TV and radio reception. Electromagnetic interference can be caused by near-field effects, diffraction, or reflection and scattering. Such interference can typically be mitigated by using satellite TV or wireless cable TV.
Although instances of TV or radio interference are infrequent and typically straightforward to mitigate, the interaction of wind turbines and navigational or defense radar signals is the subject of considerable recent attention.
Interference with Navigational and Defense Radar
Wind developers must address navigational and defense radar interference. In the majority of cases, interference is either not present, is not deemed significant, or can be readily mitigated. Understanding the extent of a wind installation’s radar interference potential and developing mitigation techniques can be more complicated than for other forms of potential interference, as it depends on turbine height, rotor-sweep area, blade rotation speed, and the landscape surrounding a wind energy project. Learn more at the Department of Defense Siting Clearinghouse, the Department of Defense Preliminary Screening Tool, and the National Oceanic and Atmospheric Administration NEXRAD Screening Tool.
As wind development continues to increase and projects are constructed in areas that were previously undeveloped, wind turbines have the potential to create interference with our nation’s radar systems. Wind turbines, like other large, metallic structures—such as buildings, TV towers, and satellite dishes—are radar reflectors and can potentially cause radar interference if placed in sensitive locations. The technology features stationary and moving parts. With a tip speed of up to ~230 mph, turbine blades rotate fast enough for radar to sense them as moving objects. If mitigation measures are not employed, such wind development could cause clutter and interference for radar systems involved in air traffic control, weather forecasting, homeland security, and national defense missions. In many cases, interference is either not present, is not deemed significant, or can be readily mitigated.
Types of Interference
Wind turbines, like other large, metallic structures—such as buildings, TV towers, and satellite dishes—are radar reflectors, and as such, have the potential to cause radar interference if placed in sensitive locations.
There are two types of radar interference:
• Direct interference happens with high reflectivity and reduces radar sensitivity, sometimes producing false images (“ghosting”) or shadow areas (“dead zones”).
• Doppler interference creates false targetsand impacts airborne and fixed radar.
Tools and Practices
Tools and practices are available to manage or mitigate the potential impact of wind turbine interference on signal interference, including the following:
• Conducting studies to ensure that the wind farm location is not in an area of high radar activity. Studies should also analyze the potential interference effects of the individual turbines and the wind project as a whole
• Coating equipment with absorbent or reflective materials to minimize the turbine’s radar signature
• Starting early communications between wind developers and the potentially affected federal agencies, such as the Department of Defense and the Federal Aviation Administration, to mitigate potential radar interference
• Installing post-processors or adding hardware (such as processors, transmitters, or receivers)
• Deploying extra radars to cover the shadow spots
• Relocating radar installations to accommodate the new wind farms
• Altering air traffic routes around new wind farms.
Even with these mitigation methods, in some proposed locations wind turbines will cause disruptive radar interference. In such cases, wind development would likely be unable to proceed at the proposed site.
See WINDExchange’s Wind Plants and Radar Interactions slideshow to learn more about wind-radar interference, different radar systems, early coordination and information review with federal agencies to prevent interference issues, and more mitigation options. For additional information, see:
- Federal Interagency Wind Turbine Radar Interference Mitigation Strategy
- Ground-Based Coastal Air Surveillance Wind Turbine-Radar Interference Vulnerability Study: Public Summary
- Wind Turbine Radar Interference Mitigation fact sheet
- IFT&E Industry ReportWind Turbine-Radar Interference Test Summary.