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Investigating Safety Impacts of Energy Technologies on Airports and Aviation (2011)

Chapter: Chapter Four - Wind Energy and Potential Impacts

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Suggested Citation:"Chapter Four - Wind Energy and Potential Impacts." National Academies of Sciences, Engineering, and Medicine. 2011. Investigating Safety Impacts of Energy Technologies on Airports and Aviation. Washington, DC: The National Academies Press. doi: 10.17226/14590.
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Suggested Citation:"Chapter Four - Wind Energy and Potential Impacts." National Academies of Sciences, Engineering, and Medicine. 2011. Investigating Safety Impacts of Energy Technologies on Airports and Aviation. Washington, DC: The National Academies Press. doi: 10.17226/14590.
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Suggested Citation:"Chapter Four - Wind Energy and Potential Impacts." National Academies of Sciences, Engineering, and Medicine. 2011. Investigating Safety Impacts of Energy Technologies on Airports and Aviation. Washington, DC: The National Academies Press. doi: 10.17226/14590.
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Suggested Citation:"Chapter Four - Wind Energy and Potential Impacts." National Academies of Sciences, Engineering, and Medicine. 2011. Investigating Safety Impacts of Energy Technologies on Airports and Aviation. Washington, DC: The National Academies Press. doi: 10.17226/14590.
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Suggested Citation:"Chapter Four - Wind Energy and Potential Impacts." National Academies of Sciences, Engineering, and Medicine. 2011. Investigating Safety Impacts of Energy Technologies on Airports and Aviation. Washington, DC: The National Academies Press. doi: 10.17226/14590.
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Suggested Citation:"Chapter Four - Wind Energy and Potential Impacts." National Academies of Sciences, Engineering, and Medicine. 2011. Investigating Safety Impacts of Energy Technologies on Airports and Aviation. Washington, DC: The National Academies Press. doi: 10.17226/14590.
×
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Suggested Citation:"Chapter Four - Wind Energy and Potential Impacts." National Academies of Sciences, Engineering, and Medicine. 2011. Investigating Safety Impacts of Energy Technologies on Airports and Aviation. Washington, DC: The National Academies Press. doi: 10.17226/14590.
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This section describes the existing body of information on the potential impacts of wind energy on airports and aviation. Impacts of wind turbines on aviation include physical pene- trations of airspace, communication system interference, and rotor blade-induced turbulence. Although wind turbines like other electricity generation emit electromagnetic fields, owing to the design and size of the generator they do not cause elec- tromagnetic interference (CAA 2010). An additional issue noted in this section is the increased propagation of meteoro- logical test towers (also known as met towers) erected to mea- sure the potential wind energy generating capacity of an area. PHYSICAL PENETRATION OF AIRSPACE The FAA undertakes a systematic review of projects that physically penetrate airspace. Project review is coordinated by the Obstruction Evaluation Office and reviews are under- taken by different divisions within the FAA that have spe- cialized expertise, including airports, technical operations, services, frequency management, flight standards, and flight procedures office (see Regulatory Review Processes in chap- ter two). The FAA also coordinates with the military and local airports, and the review is subject to a 30-day public com- ment period. Utility-scale wind turbine generators rise above 200 ft (see Figure 14) and therefore are subject to FAA review under Part 77 regardless of a project’s proximity to an airport. The FAA may issue a Notice of Presumed Hazard if a wind tur- bine is located in an approach area to a runway if the wind turbine exceeds the approach minimums. Wind turbines that are not proposed in airport approach areas are often issued a No Hazard Determination with the conditions that the wind turbine be equipped with FAA-approved marking and/or light- ing (FAA 2007). The FAA does not require all wind turbine generators in a wind farm to be marked. The volume of wind turbine applications to the FAA has increased dramatically in recent years, from 3,030 in 2004 to 25,618 in 2009 (Kaufman 2010). There have been uncom- mon cases where the Part 77 review overlooked information suggesting that a project will impact procedures and systems. In those cases, the FAA will attempt to modify approvals before construction begins. Where construction has already occurred, the FAA is limited to making adjustments to flight procedures (F. Beard, personal communication, FAA Air- 20 space Review, 2010). An example of this latter case is the Wild Horse Wind Farm in Washington State located 13 miles away from Bowers Airport (ELN). After the wind farm was constructed, the FAA flight procedures office assessed the potential impact of the constructed wind farm on instru- ment approach and missed approach procedures. It deter- mined that the wind farm presented an Adverse Obstacle and raised the height above airport minimums from 421 ft to 801 ft (Rowbothan 2010). Chain of communication break- down can also occur. For example, in the Shepherd Flats review, the local Air Force base initially signed off on the project, when it required review from other people in the agency (Robyn 2010). Although utility-scale wind turbines exceed 200 ft above ground triggering an airspace review, met towers often do not. Met towers have even been positioned at heights just under 200 ft, specifically to avoid triggering an airspace review and marking requirements. As a result, state agencies have expressed concern about the potentially undocumented haz- ard posed by met towers (Bingner 2010; S. Brummond, per- sonal communication, 2010). However, the FAA has informed South Dakota that federal law preempts the states on any matter of regulating airspace (Whitlow 2009). The FAA issued a notice in the January 5, 2011, Federal Register requesting comments on proposed revisions to AC 70/7460-1, Obstruction Marking and Lighting, that provide guidance for voluntary marking of met towers under 200 ft above ground level. The FAA is recommending that met towers include alternate orange and white painting, and also seeks comments on sleeves around the guy wires to make the facilities more visible (“Marking Meteorological Evalu- ation Towers” 2011). Just two weeks after the FAA’s notice, a crop dusting aircraft hit a met tower in the Sacramento– San Joaquin River Delta of California and crashed killing the pilot. The met tower was 197 ft tall and therefore did not require FAA airspace review or obstruction marking (“NTSB: Pilot . . .” 2011). COMMUNICATIONS SYSTEMS INTERFERENCE There has been a considerable amount of study on the poten- tial impacts of wind turbines on aviation navigation and com- munications systems. Initial concern came from the DoD and the potential effect of wind turbines on military training. In a CHAPTER FOUR WIND ENERGY AND POTENTIAL IMPACTS

21 report issued in 2006, the DoD concluded that wind turbines have an effect on primary radar and have the potential to “negatively impact the readiness of U.S. forces to perform the air defense mission” (DoD 2006). Data collection efforts have accelerated since and the DoD and FAA have worked with the wind industry to identify areas sensitive to military training and the nation’s radar system. Individual projects continue to require detailed evaluation and consideration of mitigation options. The DoD recently reported in a statement to Congress on the effects of wind turbines on military readi- ness that “the vast majority of all wind turbines proposed through the OE/AAA process raise no concerns for the Depart- ment, and for those that do raise concerns, we can generally find a way to mitigate the problem” (Robyn 2010). For the purpose of this discussion, communications sys- tems include radar and NAVAIDS. Radar can be divided between primary and secondary systems. The FAA operates two basic radar systems: airport surveillance radar (ASR) and air route surveillance radar (ARSR), both of which include primary and secondary radar capabilities (FAA 2008a). The difference between the two systems is that ASR is focused on near airport activities whereas ARSR is a long-range radar deployed at about 100 locations across the country. There are other supplemental radar systems throughout the air naviga- tion system that provide additional information to pilots. Two primary areas of impact are blockage and clutter. Two areas of impact analysis from DoD’s perspective are (1) impacts on long-range radar used for airspace surveillance and air defense, and (2) impacts on testing and training mis- sions that require electromagnetically pristine environments to collect baseline data and assess weapon performance (DoD 2006; Robyn 2010). The DoD has provided a red-yellow- green map on the FAA’s OE/AAA website to alert devel- opers about potential problem areas for wind turbine siting (FAA OE/AAA 2011). Red signifies impact highly likely to Air Defense and Homeland Security radars, aeronautical study required; yellow impact likely to Air Defense and Homeland Security radars, aeronautical study required; and green no anticipated impact to Air Defense and Homeland Security radars, aeronautical study required. Figure 15 shows the output for a fictitious wind turbine proposed in Topeka, Kansas. Primary Radar Interference Primary radar transmits a signal that is reflected back to the radar receiver when it contacts an object within the radar line-of-sight. Modern day WTGs present a significant obsta- cle with a high potential to reflect radar signals and produce images on aircraft and airport radar deemed to be unwanted returns (referred to as clutter) on radar screens. The taller the WTG, the greater is the risk of clutter. Multiple WTGs in wind farms increase the potential for clutter and the closer wind farms are to a radar station the greater potential of false radar returns. Impacts of WTGs on primary radar can be more FIGURE 14 Wind turbines from Klondike Wind Farm, Oregon (courtesy: Stephen Barrett). FIGURE 15 Department of Defense screening tool, Topeka, Kansas (courtesy: FAA website).

difficult to predict because the wind turbine rotor position changes with wind direction and as a result its potential to reflect radar signals will also change. The following types of impacts from WTGs on primary radar have been identified (CAA 2010): • Receiver Saturation—This condition occurs where the wind facility, because of its location, size, and extent, reflects enough energy back to the primary radar to sat- urate the receiver. This effect can be caused by any large structure and the likelihood of saturation from a wind farm is considered to be low. • Constant False Alarm Rate—The Constant False Alarm Rate affects radar signal processing whereby the filter- ing adjustments tuned to receive signals from aircraft are masked by new signals produced by the wind turbines resulting in a masking of the aircraft targets. • Defeating Moving Target Processing (obscuration)— Filters are used to distinguish between objects based on rate of movement with aircraft radar trained to pick up typical aircraft speeds while effectively filtering out stationary and slow moving objects. Because the speed of the wind blade tip travels at rates within the range of aircraft speed, spinning wind turbines cannot be fil- tered and removed producing clutter. • False Radar Returns (clutter)—The clutter produced by the wind blade tips shows up on radar as a “twinkling” that can be distracting to controllers looking for aircraft targets and easily cause confusion. High levels of clutter can obscure tracking of aircraft targets and pathways. • Plot Extractor/Filter Memory Overload—Some radar systems are equipped with a plot extractor that filters and processes all identified targets. Constant unwanted returns from wind facilities can overload the memory of the plot extractor clutter and cause it to shut down. • Presenting an Obstruction (shadow)—A WTG, even when stationary, will block and reflect a radar signal such as any solid structure, limiting detection of objects on the opposite side from the radar receiver. Secondary Radar Interference Secondary surveillance radar (SSR) identifies and commu- nicates with aircraft that are equipped with transponders. Although clutter is not an issue with secondary radar, two interference issues can occur. • SSR Reflections—Reflections from secondary radar can occur if the object is in the line-of-sight between the receiver and the transponder. The likelihood of this occurring would be greater the closer the WTG is to the secondary radar receiver. The line-of-sight assessment is more difficult to determine however because aircraft response from the transponder can reflect off of a struc- ture and back to the receiver under certain operating conditions, even if the structure is not directly in the line-of-sight. 22 • Presenting an Obstruction—As with primary radar, a WTG can present a physical obstruction to locating aircraft on the backside of the structure, thereby block- ing the signal and preventing its identification by the secondary radar system. NAVAIDs Interference NAVAIDs are systems that support aircraft and pilot nav- igation and location identification. There are more than 2,000 ground-based NAVAIDs available to pilots across the continental United States (FAA 2008b). They include instrument landing systems and very high frequency omni- directional radar. Although adoption of SATNAV (satellite- based navigation) has been evolving since the 1980s, some ground-based system may be retained as a back-up for satel- lite system failure or during periods when satellite signals are interrupted by distortions in the Earth’s atmosphere. NAVAIDs also include visual markings used by pilots oper- ating under visual flight rules. All NAVAIDs have the poten- tial to be impacted by inappropriately sited development including new energy technologies. Regulatory Review Thresholds The FAA provides guidance on criteria used for determining if a structure will have an adverse effect. The first trigger is if the structure exceeds the obstruction standards of Part 77 and/or is found to have physical, electromagnetic, or other line-of-sight impact on aviation prompting the FAA obstruction evaluation review (see Figure 16). In its review, the FAA will determine that an obstruction results in an adverse effect if it: 1. Requires a change to an existing or proposed instru- ment flight rules (IFRs) minimum flight altitude, a pub- lished or special flight procedure, or an IFR departure procedure for a public-use airport; 2. Requires a visual flight rule (VFR) operation to change its regular flight course or altitude; FIGURE 16 Wind Farm at Altamont Pass, California (courtesy: U.S. DOE, Lawrence Berkeley National Laboratories).

23 3. Restricts the clear view of runways, helipads, taxiways, or traffic patterns from the airport control tower cab; 4. Derogates airport capacity and/or efficiency; 5. Affects future proposed IFR and VFR operations; or 6. Affects the usable length of an existing or future runway. The FAA also considers whether or not the proposal will have an effect on a significant volume of aeronautical activity on an airport, which is a case-by-case determination. Signifi- cant volume effects vary for different activities (e.g., effects on departures and arrivals may be a daily impact, whereas instrument procedures and minimum altitudes may be utilized weekly). The FAA will make a substantial adverse effect determination if the structure causes electromagnetic inter- ference on facilities and aircraft or if there is a combination of adverse effects listed previously and an impact on significant volume (FAA 2008a). Procedures for Handling Airspace Matters provides more specific guidance on whether or not a significant adverse effect will occur. For example, it states that structures that necessi- tate an alteration to a Minimum En Route Altitude cause an adverse effect. However, flight procedures and air traffic per- sonnel may consider conducting more detailed analysis to determine if the structure will result in a substantial adverse effect depending on the location of the structure relative to flight traffic and extent of use. The loss of altitude for a cardi- nal direction is generally considered to result in a substantial adverse effect except when the aeronautical study determines that the Minimum En Route Altitude is not normally flown by aircraft nor used for air traffic control purposes. Another example is provided in Terminal Instrument Pro- cedures (TERPS) guidance (TERPs 2010). A structure that penetrates the 40:1 departure slope for IFR departures is con- sidered to be an obstruction to air navigation. If the obstacle penetrates the departure slope by more than 35 ft, it is pre- sumed to be a hazard and a Notice of Presumed Hazard is issued. Further analysis by flight procedures and air traffic is then necessary to determine if the structure poses a substan- tial adverse effect. Guidance from the Civilian Aviation Authority (CAA) of the United Kingdom states that proposed structures large enough to cause a potential impact to radar (including wind turbines) should notify the CAA for an impact assessment if the structure is within 15 miles of a radar facility. How- ever, impacts are not likely for structures beyond 6.2 miles (or 10 km) (CAA 2010). ROTOR BLADE TURBULENCE Rotor-induced turbulence can occur downwind of a WTG where the wind flow is disrupted after passing through the rotor producing a chaotic and turbulent airflow (see Figure 17). Analysis of the extent of disruption downwind of the wind tur- bine suggests that the amount of turbulence is not significantly different from other large structures and, therefore, additional consideration beyond normal minimum separation distances and obstacle avoidance is not necessary (CAA 2010). Numerical simulations have shown that natural turbu- lence in the atmosphere will destabilize the wind turbine creating vortices at a distance of 2–6 rotor-radii (250–750 ft) (Troldborg et al. 2007). Aircraft flying at the same eleva- tion as the wind turbine rotor (200–450 ft above ground) at a distance where turbulence is projected to occur is deter- mined to be operating in an unsafe location. Turbulence downwind of a wind turbine could be a consideration for assessing the suitability of very light sport aviation such as parachuting, hang gliding, paragliding, and microlight oper- ations (CAA 2010). MITIGATION OPTIONS The following mitigation options have been considered for minimizing impacts of wind farms on aviation: • Allow appropriate siting to avoid physical penetration and communication systems impacts. • Provide developers with the opportunity to fund gap- fill radars or contribute to the cost of replacing long- range radar, thereby providing a dual benefit of allowing renewable energy development and upgrading aging radar systems. • Re-route air traffic around the wind energy facilities to avoid potential shadow effects and disruptions associ- ated with wind farm radar clutter as part of operational mitigation. Negative effects of an increased noise foot- print and CO2 emissions from longer flight tracks need to be considered. • Turn off radar that is receiving false returns for the wind farm area and use supplemental radar that is available in FIGURE 17 Gorgonio Wind Farm, California (courtesy: NASA Earth Observatory website).

the region but not affected by the clutter fill in the area of the wind farm by a technique called data fusion on in-fill radar. Also referred to as a mosaic radar, this can only be accomplished where the primary radar can selec- tively turn off specific areas, there is a supplemental radar coverage to provide in-fill, and the two radar systems can be pieced together and displayed. • Improve radar coverage for areas where low-level radar coverage is not required through physical or terrain masking. This would necessitate moving the radar facility to a higher elevation or constructing a man-made struc- ture to create an artificial radar horizon. Planning this type of mitigation would require detailed study to ensure that the proposed design would resolve the interference issues. Furthermore, this masking technique would only be appropriate if some loss of radar coverage in the area would be acceptable. • Use radar absorbent materials on WTG towers and nacelles to reduce the radar cross section of the struc- ture that produces clutter. However, materials for use on blades has not been effectively developed, which is particularly problematic because the blades caused the greatest amount of interference. • Fund research (collaboratively between government and industry) on technical mitigation that collects additional information of existing wind turbine affects, designs parameters for gap-filler radar, characterizes wavelengths used in current radar systems to reduce signatures, and advances software processing. • Develop new and modified radar facilities. For example, multi-lateration involves establishing a secondary radar system with a number of strategically located receiver stations in the area to provide networked radar coverage. These receiving stations would identify aircraft equipped with transponders and calculate their location through triangulation based on the data collected from multiple locations. This type of system is a more basic and in- expensive form of a SSR system that might be employed today. • Create non-auto-initiation zones (NAIZs) with some advanced primary radar plots that filter out tracks cre- ated by the wind turbines while not filtering out tracks characteristic of aircraft. The problem with a NAIZ is that although the wind turbine tracks are not displayed, the false returns still exist and, depending on frequen- cies, could affect the display of nearby aircraft tracks producing incorrect information. Furthermore, aircraft gaining elevation from low altitudes and emerging into and above an established NAIZ will not be picked up by radar until above the NAIZ, which is the primary reason why NAIZs are generally discouraged. • Use advanced tracking algorithms to take advantage of high-speed computer processing capabilities to con- duct nontraditional aircraft tracking and data filtering. Although promising, the accuracy of the analytical methods has yet to be fully tested and there may still be a risk of error. 24 • Create transponder mandatory zones (TMZs) that would allow SSR to provide full augmentation for primary radar. However, TMZs are uncommon at this time. • Consider a model program where airspace over specified wind farms is restricted to transponder carrying aircraft. WIND TURBINE IMPACT EXAMPLES Several examples are provided here to illustrate wind turbine impacts and how they were addressed. Travis Air Force Base—Fairfield, California Three wind energy development companies are proposing to construct a combined 142 wind turbines in Solano County, California. The area currently supports 833 turbines, with the closest structure located 4.65 nautical miles southeast of Travis Air Force Base (TAFB). The 60th Air Mobility Wing (AMW) at TAFB expressed concern that the proposed tur- bines could interfere with the base’s ability to provide safe and efficient air traffic services to aircraft operating in the vicinity of the projects. In particular, the AMW focused on the potential impact caused by wind turbines on the terminal surveillance radar used by air traffic controllers to provide radar services to aircraft (Solano County 2010). The airspace over the project area is complex and includes operations from Buchanan Field, located in Concord, and Rio Vista Municipal Airport (O88), as well as IFR traffic between the Sacramento and Oakland. The airspace is designated as Class E (with the exception of Class D airspace within 5 miles of the AFB), with a floor of 700 ft above ground level. The airspace does not require radar service, although airspace in the area is safer and more efficient as a result of TAFB’s enhanced capabilities [Digital Airport Surveillance Radar model-11 (DASR-11), state-of-the-art terminal surveillance radar], which became operational in February 2009. In moving to resolve potential issues of concern, the U.S. Transportation Command (parent to the 60th AMW) entered into a Cooperative Research and Development Agreement (CRADA) with the three wind energy companies, with the objective of determining the “projected impact of wind turbine development upon air traffic operations near TAFB” (U.S. Transportation Command 2010). Other parties of the CRADA were the U.S. Air Force Flight Standards Agency and the Idaho National Laboratory. Under the CRADA, three specific tasks would be completed: (1) obtain reliable, objective data to assess current air traffic operational radar coverage in the TAFB area; (2) run a simulation to assess the predicted air traf- fic operational impact potentially caused by proposed wind turbine development; and (3) assess the operational impact on the TAFB air traffic control areas of Shiloh III, Montezuma Wind, and Solano Wind Phase 3 wind projects. A working group evaluated both baseline (data recorded in October 2009 from TAFB) and simulation data. The overall

25 result of this work indicated that the construction and opera- tion of the three identified projects would not reduce the prob- ability of detection more than the 5 percentage point margin identified by the working group to protect the safety and effi- ciency of operations in proximity to the area. The following issues were considered when making this determination: • There would be no impact on aircraft utilizing active transponders or transponder-equipped VFR aircraft because wind turbines do not impact secondary radar signals. • Because the FAA established a minimum level of safety for Class E airspace that does not require surveillance coverage, degradation of radar coverage caused by wind turbines would not result in a reduction of safety below the minimum standard set by the FAA. However, because radar coverage exists, and that radar coverage increases the safety and efficiency of operations within the air- space, degradation of service caused by the wind tur- bines could decrease the overall safety and efficiency of operations. Therefore, it was necessary to identify an acceptable level of degradation in radar coverage and, more specifically, the ability to accurately detect nontransponder-equipped aircraft over the area. • The number of false targets presently observed by the controllers is expected to be reduced, if not eliminated, after a correction to the Standard Terminal Automa- tion Replacement System (STARS) configuration. (The STARS system receives data and flight plan information and presents the information to air traffic controllers on color displays, allowing the controller to monitor and control air traffic.) This correction was temporarily demonstrated by the working group in December 2009, which clearly showed that the use of track eligibility coupled with existing STARS tracking algorithms elim- inated false targets even during significant wind activ- ity over the area. • To further assess the level of impact, the working group considered the number of nonparticipating aircraft likely to be operating at any given time within the lateral lim- its of the area. Based on the data collection, the number of nonparticipating aircraft was estimated to be minimal. The working group found that approximately 30 primary- only flight tracks occurred in October 2009 over the area. • Considering all these factors (the airspace classification, operational configuration, air traffic service requirements, and traffic workload), the working group determined that degradation of radar detection resulting from addi- tional wind turbine development in the area could result in a degradation of radar services provided to nonpar- ticipating aircraft; however, given the “see and avoid” requirement, would not constitute a significant degra- dation of air safety. • The working group agreed that a minor reduction in probability of detection over the area would not create an unsafe operating environment, but would decrease the safety and efficiency of operations. Because there was no reference point from which to determine the demarcation between acceptable and unacceptable impact, the work- ing group took into consideration the type and frequency of operations over the area to determine a level of degra- dation of surveillance coverage that would meet the oper- ational needs of the Air Force. Additionally, the working group considered what services would be lost as a result of that degradation and determined that in the best inter- est of safety and the efficiency of air traffic operations, an average degradation not greater than 5 percentage points below the established baseline values (current performance) of the probability of detection would be acceptable. Heritage Aviation, Burlington, Vermont Heritage Aviation of Burlington, Vermont, erected a 130-ft WTG on airport property that it leases from the Burlington International Airport (BTV) to generate electricity for its hangar and facilities (see Figure 18). As part of the project approval, Heritage filed a Form 7460 and provided informa- tion on potential impacts of physical penetration of airspace and potential impacts on communication systems. Westslope Consulting provided an analysis of the potential impact of the wind turbine on existing Airport Surveillance Radar (ASR-11). The physical cross section that might block radar signals and produce false returns was projected to be an additional 52 ft, given that the existing building height of the Heritage hangar is 53 ft and the proposed height of the wind turbine is 98 ft to the top of the tower. The radar impact analy- sis assumed that the cross section of impact was limited to the tower because the blades and nacelle are made of fiberglass- reinforced polyester and the blades are 120 degrees apart and moving (Westslope 2009). The shadow area is constrained by the close distance of the wind turbine and the ASR and because the terrain rises approximately 2 miles beyond the wind turbine. Using a 6-ft-diameter tower as the obstruction, the shadow modeling predicts a cross range of 12 ft directly behind the tower spreading to 74 ft in width at the hill 2 miles away. The analysis concluded that aircraft would be operating in an envi- ronment in this area because of their need to fly at very low altitudes and close to the wind turbine to encounter the radar FIGURE 18 Wind turbine at Burlington International Airport, Vermont (courtesy: Christopher Hill, Heritage Aviation).

shadow cast by the WTG. Furthermore, if an aircraft were to pass through the shadow, the detection level would be below the tolerance level though the modeling report shows the prob- ability of detection percentage decreasing from 100% to 40% in an area approximately one-quarter to one-half of a mile behind the turbine at turbine height and decreasing at distance. FAA approval included clear conditions that the appli- cant would be subject to conducting and paying for miti- gation necessary to address unforeseen degradation to the ASR-11 system. Specifically, this included ceasing opera- tion of the wind turbine while mitigation is implemented, payment for upgrades to the system, and permanent dis- mantling of the system at the owner’s expense should other mitigation options not succeed (FAA 2009). Ivanpah Wind Project A wind energy developer proposed the construction of 83 wind turbine generators on Table Mountain approximately 10 miles 26 west of the proposed Ivanpah Valley International Airport, a new airport proposed near Las Vegas. The FAA issued a No Hazard Determination for the wind project, which was appealed to the U.S. Court of Appeals by Clark County, the sponsor of the new airport. On April 18, 2008, the FAA was ordered to reconsider its decision to allow the construction of a wind farm near the site of the new Las Vegas Airport. The evidence presented indi- cated that the turbines would interfere with the airport’s radar systems. Specifically, the court agreed with evidence presented by an aerospace consultant for the county that each wind turbine would have a radar signature similar to a jumbo jet and that the wind farm would appear on the radar similar to a fleet of jumbo jets. The report also stated that the sig- nature could appear and disappear rapidly based on chang- ing wind conditions, which would hamper the air traffic controller’s ability to control aircraft in the area. The federal district court determined that the FAA’s determination was arbitrary and capricious (Clark County 2008).

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TRB’s Airport Cooperative Research Program (ACRP) Synthesis 28: Investigating Safety Impacts of Energy Technologies on Airports and Aviation explores physical, visual, and communications systems interference impacts from energy technologies on airports and aviation safety.

The energy technologies that are the focus of this report include the following:

• solar photovoltaic panels and farms,

• concentrating solar power plants,

• wind turbine generators and farms, and

• traditional power plants.

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