Sunday, February 15, 2009

It's a bird! It's a plane! It's a ... wind turbine?

As concerns over climate change, geopolitical disputes, and increasing energy demands rise, the United States has recognized wind energy as an integral part of our energy mix in the future. However, agencies such as the U.S. Department of Defense (DoD), U.S. Department of Energy (DoE), Federal Aviation Administration (FAA), and the National Weather Service (NWS) have reported that the towers and rotating turbine blades degrade radar quality due to adverse shadowing and clutter effects in the line-of-sight of radar applications [1,2]. These effects have the potential to threaten national security by impacting the country’s military air defense operations, decrease air safety by reducing Air Traffic Controllers’ ability to monitor the U.S. airspace, and decrease the accuracy of weather prediction [1]. Consequently, the U.S. government has implemented broad restrictions on the development of new wind projects that may interfere with civilian or military radar although mitigation techniques have been proposed that may allow the two to coexist [1].


On February 14, 2009, the FAA spoke out against the 420 MW Cape Wind Project, which includes plans to install 130 turbines in the Nantucket Sound. The site, off the shores of Massachusetts, was chosen because of its characteristically persistent and intense winds, but has been accused of interfering with 3 major FAA radar systems [4]. The FAA claims that the turbines will add extraneous clutter that may reduce its ability to monitor the sky since rotating turbines resemble aircraft on radar. Since this would be the United State’s first off-shore wind project, the FAA’s block forecasts a new era of controversy over off-shore wind projects. The Cape wind project has already weathered years of heavy criticism from the public because of environmental concerns and those who claim it will be an “eyesore” on the horizon [4].


In the near-future governing bodies such as the DoD, DoE, FAA, and NWS, must decide whether they are willing to put in substantial resources into upgrading already very expensive radar systems to filter out wind turbine clutter, or if they will redesign wind turbines to be less obtrusive to radar clutter, which may substantially increase the cost of production due to the need for more expensive radar absorbing materials [2]. The alternative would be to simply block the financing of off-shore projects in areas that would intercept civilian and military radar. In many senses the Cape Wind Project will set the tone for the off-shore wind industry in the next few months based on how this block by the FAA is handled.


1. Report to the Congressional Defense Committees: The Effect of Windmill Farms on Military Readiness, U.S. DoD, September 2006.

2. Rashid, L.S.; Brown, A.K., RCS and radar propagation near offshore wind farms, 2007 IEEE Antennas and Propagation Society International Symposium (9-15 June 2007) pg. 4605 – 4608.

3. “FAA: Controversial Cape Wind project could be radar hazard,” The Boston Herald, February 14, 2009. http://www.bostonherald.com/business/general/view.bg?articleid=1152140&srvc=business&position=3

4. Grad, P. “Offshore USA: The Cape Wind offshore wind farm: a first for the USA?”, Refocus, Volume 6, Issue 5, September-October 2005, Pages 34-36. doi:10.1016/S1471-0846(05)70456-X .

5 comments:

Amos said...

Eliminating the radar clutter caused by wind blade is not only a financial challenge, but a technical one. Most of effective radar absorbing materials are not available commercially due to their primary application to military jets, ships, etc. The military is reluctant to release such technology to the public. Civilian research and advancement in this area lacks far behind the military .
Thus, one could think of radar signature reduction as a way to design wind turbines more radar friendly. Reducing the radar cross section (RCS)(commonly used in design of "stealth" aircraft) requires extensive testing and research in terms of blades, tower, and nacelle design while retaining the efficiency of the turbine itself as shown in this research program report.
Therefore, as long as FAA and other organizations object this wind farm due to safety and national security issues, the project might have no choice but to invest in a long and costly redesign process.

Michael E. Webber, Ph.D. said...

This is a great point--wind, for all its merits, is not without its drawbacks. And, this challenge is particularly confounding for the USAF because they want to make their bases as independent and renewable as possible, and wind is the fastest and cheapest way to do so. If they can't use wind because of the radar problems, then they will have a hard time making up the difference with solar.

Mithun said...

Wind has its own demerits, but we will have to bring a technology change or use mitigation factors to efficiently use wind power. Our radar systems might have to be changed, as time progresses, more such problems will emerge. Such problems have always been there, and will be there in future too as rightly pointed, this shouldnt deter us to use wind power or be prepared to face hard time with other renewable technologies.

David Wogan said...

I would think that national security (radar defenses) would win out over wind turbines most of the time. This shouldn't deter us from using wind turbines, but will require some R&D to solve. Maybe this will result in wind farms being built in areas where interference with radar installations is not a problem, and solar elsewhere?

Zoe said...

How do Denmark and the UK cope with these challenges? Do they not use radar to the extent that the US does?