This is an excerpt from EERE Network News, a weekly electronic newsletter.

October 04, 2006

Report Details Wind Turbine Interactions with Military Radars

A photo of a line of at least seven wind turbines stretching into the distance, with the wind turbine blades blurred by their motion.

Wind turbines have a fixed base, but their blade tips achieve high speeds, a combination that can confuse military radars.
Credit: Warren Gretz

The U.S. Department of Defense (DOD) released a report on September 27th detailing how wind turbines interact with military radar. While the report supports wind energy's role in meeting U.S. energy needs, it also notes that in certain circumstances, wind turbines can impede radar systems and operations. To detect intruding aircraft and missiles at long ranges, the military relies on a variety of techniques to subtract the radar signal of ground-based "clutter," such as buildings or transmission lines. Unfortunately, these techniques weren't designed to handle large, quickly moving objects such as wind turbine blades, and so the wind turbines can potentially interact with radar signals in ways that could lower the radar's effective sensitivity. The report concludes that more needs to be done to understand this interaction and to develop ways of mitigating the impacts. See the report, "The Effect of Windmill Farms on Military Readiness" (PDF 1.2 MB). Download Adobe Reader.

There are a number of technical mitigation options available today, such as upgrading the software or adding new signal processing filters to existing radars or replacing older radar systems. For example, a new digital processing system developed by BAE Systems was tested in the United Kingdom in June, and though an official report on the test has not been released yet, BAE Systems announced in July that the test was a success. In the United States, the National Wind Coordinating Committee (NWCC) held a special forum on wind turbine and radar interactions in July, and DOE is currently working with radar system experts across the country and overseas to catalogue the known mitigation techniques, identifying today's most promising options and those that are worth of developing in the future. See the BAE Systems press release and the presentations from the NWCC forum.

Concerns about wind turbines interacting with radars had caused the delay of a number of wind power projects in the Midwest for several months. According to the American Wind Energy Association (AWEA), the Federal Aviation Administration recently approved 614 applications for individual wind turbines that total more than 1,000 megawatts of new wind power across Illinois, Minnesota, South Dakota and Wisconsin. One such project is the 150-megawatt MinnDakota Wind Power Project, which straddles the border of Minnesota and South Dakota. PPM Energy began construction on that project in September. The approval of these projects demonstrates that the review and evaluation process for impacts of wind projects protects civilian and military operations as well as the development of wind energy. See the press releases from AWEA and PPM Energy.