{"id":2740,"date":"2011-02-12T09:19:47","date_gmt":"2011-02-12T16:19:47","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=2740"},"modified":"2011-02-12T09:24:28","modified_gmt":"2011-02-12T16:24:28","slug":"are-wind-turbines-bad-for-aviation","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/are-wind-turbines-bad-for-aviation\/","title":{"rendered":"Are Wind Turbines Bad for Aviation?"},"content":{"rendered":"

It would be a supreme irony if\u00a0a part of environmentally-positive power production halted the possibility of\u00a0“green” aviation by making\u00a0it unsafe to be in the skies.\u00a0 Luckily, this might not be the\u00a0major problem some perceive, and solutions are in place or being developed.\u00a0\u00a0<\/p>\n

For a brief time last April the United States Air Force held up construction of an eastern Oregon wind farm that will be the largest in America.\u00a0 Concerned with the possible interference that 300 new giant wind turbines might cause for radar station transmissions in an otherwise remote part of the state, the Air Force stepped in.\u00a0 That was a short-lived interruption, with Oregon\u2019s Senators countering with concerns about the 706 jobs, $130 million in taxes to local counties over two decades and $2.7 million in royalty payments to farmers and ranchers that would be lost by shutting down the project, even though the Federal Aviation Administration issued a \u201cnotice of presumed hazard\u201d that halted construction of towers above zero feet in height.<\/p>\n

According to the Oregonian<\/em> report<\/a>, \u201cAir Force Gen. Gene Renuart, head of U.S. Northern Command<\/a>, testified before Congress in March that the military is increasingly concerned about wind farms disrupting radar. The number of U.S. wind projects is growing fast amid increasing demand for renewable energy and plentiful government subsidies.\u201d<\/p>\n

The 338 turbine project would generate 845 megawatts, enough to supplant a coal-fired facility in nearby Boardman, Oregon that has been a source of contention with local environmentalists.<\/p>\n

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Wind farms can confuse radar<\/dd>\n<\/dl>\n

The Air Force told the Oregonian<\/em>, \u201cThe Shepherds Flat turbines \u2013 combined with about 1,800 other turbines built or proposed within the Fossil station’s range \u2013 would \u2018seriously impair the ability of the (Department of Defense) to detect, monitor and safely conduct air operations in this region.\u2019” \u00a0\u00a0The Air Force contends that tall turbines can \u201creflect radar signals, creating a blind spot that can erase airplanes on radar screens. The turbine’s rotating blades can also clutter the screens, creating a radar signature that constantly changes as the blades slow down or speed up in the wind.\u201d<\/p>\n

Industry officials say they’re working on radar friendly turbine technologies. Upgrades to radar stations\u00a0– possibly financed by the wind farms\u00a0– would also help. Modern systems are much less affected by spinning turbines.<\/p>\n

Oregon Senators Ron Wyden and Jeff Merkley, and U. S. Representative Greg Walden lobbied the White House and Pentagon while putting three Defense Department nominees on hold to allow Defense Secretary Robert Gates, to agree that \u201chomeland security concerns shouldn\u2019t thwart home grown renewable energy.\u201d\u00a0 Senator Wyden said, \u201cIt was clear to me that he understood it was possible to do both.”<\/p>\n<\/div>\n

In the meantime, radar experts at MIT\u2019s Lincoln Laboratory reviewed the project, and Air Force and industry personnel agreed to work on solutions that would mitigate loss of radar tracking because of turbine activity.<\/p>\n

The hubbub was significant enough to evoke a response from Britain, with Flight Global\u2019s John Croft reporting,<\/a> \u201cThe green roadblock is an example of a growing number of aviation-related compatibility issues arising from renewable energy projects, many of which are located at or near aviation infrastructure. Although solutions are usually found, an expected rise in the number of proposed projects is prompting regulators to be proactive in setting out ground rules.\u201d<\/p>\n

Croft further explained, \u201cDangers can also precede the installation of turbines. Low-level operators for firefighting and other missions in the USA are being warned of 122-152m (400-500ft)-high temporary meteorological test towers that are being installed at potential sites for wind farms to determine whether the site could be profitable.<\/p>\n

\u201cAviation officials in Idaho say the slim towers are difficult to spot if not marked, are installed in a matter of days, and can be gone in 12-18 months.\u00a0\u00a0Many pilots have ‘close call’ stories to relate.”\u00a0<\/p>\n

Flight Global\u2019s<\/em> David Learmount had reported in 2006 that, \u201cBAE Systems has developed a bolt-on, two-chip radar signal processor that can negate the radar-confusing returns that wind turbines generate.\u00a0 The advanced digital tracker (ADT) does not interfere with the radar, but post-processes the signals before they are shown on the display, dismissing the clutter the turbines can create so “real” targets can be detected even close to large wind farms.\u201d<\/p>\n

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11,000 square foot radar signature<\/p><\/div>\n

Because wind turbines have a total radar cross section of 1,000 square meters (11,000 square feet), and the turning blades \u201cconfuse the Doppler-based moving target detectors that primary and secondary radars use,\u201d the potential for problems abounds.<\/p>\n

Originally developed to separate missile radar signatures from those caused by wave action in a \u201charsh naval environment,\u201d the BAE\u00a0 system is a small device that can be \u201cbolted on to any type of radar, and consists of an interface chip to make it compatible with the unit, and another chip hosting the software.\u201d\u00a0 Algorithms can be fine tuned for a particular site because each wind farm has a unique radar signature.\u00a0 BAE has been working on this \u201cfix\u201d since 2002.<\/p>\n

Newcastle airport in the United Kingdom has developed its own software solution <\/a>for the same problem, one which \u201cblanks\u201d wind farm reflections, \u201cwhich have the same characteristics as moving aircraft returns and can thus be dangerously misleading for controllers.\u201d\u00a0 Surrounded by wind farms, Newcastle needed a way to separate the turbines on the ground from the turbines in the air.\u00a0 Their \u201cblanking\u201d approach provides a \u201cpatch\u201d to cover the existing and potential wind farm sites. By not showing radar images for wind turbines, clutter on the controllers\u2019 radar screen is eliminated and potential confusion reduced.<\/p>\n

These developments are important to the CAFE Foundation and researchers working on ways to \u201cfree up\u201d general aviation from the current controller-based air traffic systems.\u00a0 The fifth annual Electric Aircraft Symposium, coming in late April, will address many of these issues and their potential solutions.<\/p>\n