Effects of Wind Turbines Wake Turbulence on General Aviation Aircraft and Airports

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Benedict Lyons
6 years ago
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1 ACRP Problem Statement: Effects of Wind Turbines Wake Turbulence on General Aviation Aircraft and Airports Recommended Funding Amount: $400,000 ACRP Staff Comments FAA has completed numerous studies in this area. This research is already available in ACRP Report 108: Guidebook for Energy Facilities Compatibility with Airports and Airspace. TRB Aviation Group Committee Comments AIRFIELD AND AIRSPACE CAPACITY AND DELAY: The idea is relevant due to the importance of GA safety issues in airspace operations; however it should be pursued by FAA-AVS. AVIATION SYSTEM PLANNING: This topic has been extensively studied as well as published, both from the wind turbine turbulence perspective and from the aircraft response to turbulence perspective. It is unclear what additional research is needed and if more is needed, it would more appropriately be conduced by the FAA, perhaps in conjunction with NASA. Review Panel Comments Recommended. The audience for the proposed research is potentially large (39 states). There are studies that could be compiled and augmented for GA and GA airports. Research should start with a synthesis of what has been done. The challenge would be to determine the scale of the problem and how broad the impact.

AIRPORT COOPERATIVE RESEARCH PROGRAM ACRP Problem Nor 15-03-05 PROBLEM STATEMENT I. PROBLEM TITLE Effects of Wind Turbines Wake Turbulence on General Aviation Aircraft and Airports II.

2 AIRPORT COOPERATIVE RESEARCH PROGRAM ACRP Problem Nor PROBLEM STATEMENT I. PROBLEM TITLE Effects of Wind Turbines Wake Turbulence on General Aviation Aircraft and Airports II. BACKGROUND Wind power has increased exponentially since the dawn of the 21 st century. The amount of operating wind energy capacity has increased more than 16 times from 2000 to 2012 (American Wind Energy Association, 2014). Every state in the United States has either an operational wind energy project or a wind-related manufacturing facility, or both. By the end of 2012, the U.S. had 45,100 operating wind turbines across 39 states and Puerto Rico (American Wind Energy Association, 2014). Wind turbines and wind farms are especially popular and common in states where there is a strong wind resource and other critical factors are present, such as access to land and access to the transmission lines. Examples include Kansas, Nebraska, Iowa and South Dakota. Today s modern wind turbines capture the natural wind s kinetic energy from our atmosphere and convert it into electricity. Most wind turbines have three blades and sit atop a steel tubular tower, and they range in size from 80-foot-tall turbines that can power a single home to utility-scale turbines that are over 260 feet tall and power hundreds of homes (American Wind Energy Association, 2014). As the blades of the wind turbine turn, a wake downwind of each turbine is formed and the shear layer at the edge of the wake quickly becomes unstable. This instability acts to break down the organized spiral of the tip and root vortices within a rotor diameter downwind of the rotor plane. (National Renewable Energy Laboratory, 2012) The Airport Cooperative Research Program s Synthesis 28 explains that wind turbines disrupt uniform air flow causing unseen turbulence produced downstream of wind turbines. Figure 1 below illustrates the effects of rotor wake turbulence. Figure 1. Fog trailing from Horns Rev Offshore Wind Farm, Denmark. Source: Vattenfall Energy, Christian Steiness, Sweden, 2007.

3 The turbulence impacts are primarily limited to General Aviation (GA) aircraft due to their lightweight airframes and propensity to operate at lower altitudes where turbulence could occur (ACRP, 2013). It is for these reasons that some general aviation pilots, agricultural and air ambulance operators, airports managers, aviation associations, and the available research on the topic express concerns about the wake turbulence that the spinning blades of the wind turbines are creating. The potential hazard caused by wind turbine vortex wakes seems to be viewed as two different types: the induced roll hazard on the aircraft and the gusty crosswind from the vortex (University of Kansas, 2013). III. OBJECTIVE The objective of this study is to understand the wake turbulence generated by wind turbines and wind farms; determine if these structures present any hazard and negative impact on general aviation aircraft, specifically including agricultural aircraft, air ambulance aircraft and operations around nearby airports; establish parameters for the safe operation of general aviation aircraft near wind turbines; and identify opportunities for improvement of the Federal Aviation Administration s (FAA s) Obstruction Evaluation process. PROPOSED TASKS The proposed research should include, but not be limited to the following tasks: - Conduct an extensive literature review on previous studies and work performed on this topic to understand the research that has already been done and expand upon it. Consider studying the impact of wind turbines on other industries, such as agriculture and marine. - Study the operation of wind turbines (how they are built, how they work, what their parameters and limitations are, etc). - Analyze and examine the air flow and turbulence caused by wind turbines in a wind tunnel. - Select several different examples of wind turbines and farms based on topography and weather patterns across the country. State aviation directors could help identify some of wind farms to be studied within their states. - Analyze and examine the obtained data using previously identified techniques and methods to explore and evaluate the impact of wake turbulence and: o Determine the amount and pattern of wake turbulence from a single wind turbine under different weather conditions, o Determine the amount and pattern of wake turbulence from wind farms of different sizes under different weather conditions, both in a horizontal direction and in a vertical direction,

4 o Correlate the strength of the vortices to aircraft performance and define safe operating limitations (based on different general aviation aircraft and using FAA definitions), and o Provide recommendations concerning the maximum height and location (direction and distance) of wind farms in relation to airports, runways, and their local wind and weather patterns. - Identify opportunities for the FAA s Obstruction Evaluation Group to incorporate the study results during their Obstruction Evaluation process, including revising FAA Order , to allow for the study of dynamic structures. - Identify needs for future research to address unresolved issues. - Prepare a draft final guidebook documenting the findings of the research and submit it to the Project Panel for review and comment. Revise report to address Panel concerns and suggestions and submit to ACRP for publication. An interim report should be prepared to document the findings from the literature review and data collection efforts before commencing subsequent tasks. It should also present the work plan for the remainder of the project to allow the Project Panel to review it, suggest alternatives and approve the work plan. IV. ESTIMATED FUNDING It is estimated that the proposed research to conduct this study and prepare the report would require a funding level of $400,000. V. ESTIMATED RESEARCH DURATION It is anticipated that the proposed research would require 18 months to complete by a suitably experienced research team, including the final three months for review and revision of the draft final report. VI. RELATED RESEARCH A literature review by the team has revealed very little research related to the proposed problem. However, a reasonable amount of research was found regarding the radar interference caused by wind turbines and farms, their impact to land use zoning and airspace penetration, as well as the need for marking and lighting wind turbines and meteorological test towers (met towers, temporary structures used to measure wind speed and direction to identify locations for future wind turbines) to mitigate risks to lowaltitude aviation operations. According to the University of Kansas 2013 study on the subject, the turbines on a wind farm can set up a circular vortex as far away as 3 miles, which can catch a small plane and spin it around if it gets too close. However, they also say that more research is needed. Their study only raised the red flag of the problems wind farms can have on small airports and aircraft in close proximity.

5 VII. PROCESS USED TO DEVELOP PROBLEM STATEMENT The problem statement was initiated and developed by the following authors with collaboration with industry experts and stakeholders: Yasmina Platt; Central Southwest Regional Manager, Aircraft Owners and Pilots Association (AOPA); 421 Aviation Way, Frederick, Maryland 21701; ph: (301) ; Jesse Romo; Director, Division of Aviation, Kansas Department of Transportation; 700 SW Harrison Street, 9 th floor, Topeka, Kansas 66603; ph: (785) ; jromo@ksdot.org VIII. DATE AND SUBMITTED BY Date of submission: March 19, Submitted by: Yasmina Platt; Central Southwest Regional Manager, Aircraft Owners and Pilots Association (AOPA); 421 Aviation Way, Frederick, Maryland 21701; ph: (301) ; yasmina.platt@aopa.org

Wind Energy Ordinances

INFORMATION GUIDE: Wind Energy Ordinances Wind turbines are multiplying across the U.S., and most are installed in rural areas overlooking crops, cattle, timber, and lakes. Rural communities have experienced