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WASHINGTON, DC, US, October 11, 2006 (Refocus
Weekly)
The U.S. Department of Defense says construction
of windfarms should proceed, providing the turbines do not interfere
with military radar.
“Given the expected increase in the U.S. wind energy development,
the existing siting processes as well as mitigation approaches need
to be reviewed and enhanced in order to provide for continued
development of this important renewable energy resource while
maintaining vital defense readiness,” concludes the ‘Report to the
Congressional Defense Committees on the Effect of Windmill Farms on
Military Readiness.’ The 62-page report was mandated by Congress, to
assess the effects of windfarms on military readiness, on the
operations of military radar installations and of technologies that
could mitigate any adverse effects on military operations.
“Although wind turbines located in radar line of sight of air
defense radars can adversely impact the ability of those units to
detect and track, by primary radar return, any aircraft or other
aerial object, the magnitude of the impact will depend upon the
number and locations of the wind turbines,” it explains. “Should the
impact prove sufficient to degrade the ability of the radar to
unambiguously detect and track objects of interest by primary radar
alone, this will negatively impact the readiness of U.S. forces to
perform the air defense mission.”
“The mitigations that exist at present to completely preclude any
adverse impacts on air defense radars are limited to those methods
that avoid locating the wind turbines in radar line of sight of such
radars,” and these mitigations may be achieved by distance, terrain
masking or terrain relief, and require case-by-case analysis. An
earlier analysis performed at Cape Cod Air Force Station was “overly
simplified and technically flawed” and “a more comprehensive
analysis followed by development of appropriate offset criteria for
fixed-site missile early warning radars should be performed on an
expedited basis.”
“Wind turbines located in close proximity to Comprehensive Test Ban
Treaty monitoring sites can adversely impact their ability to
perform this mission by increasing ambient seismic noise levels,”
and “appropriate offset distance criteria should be developed to
mitigate such potential impacts,” it continues. The Federal Aviation
Administration is responsible for maintaining safety in U.S.
airspace and the National Weather Service is responsible for
accurate weather forecasting services, and DoD defers to those two
agencies.
By working with FAA to evaluate windfarm proposals on a case-by-case
basis, the DoD can ensure that all mitigation techniques are
explored and developers have the greatest opportunity to build the
projects without delay, and without impact to military radar, it
explains.
The Department of Energy estimates that 60,000 MW of wind capacity
is operating around the world, with 10,000 MW in the U.S., including
installations with several hundred turbines with rotating blades
reaching heights of to 500 feet. “The numbers, height and rotation
of these wind turbines present technical challenges to the
effectiveness of radar systems that must be carefully evaluated on a
case-by-case basis to ensure acceptable military readiness is
maintained,” the report explains.
“For many cases, processes are in place to allow responsible federal
authorities to complete determination of acceptability of wind
turbine impacts on military readiness,” but since installation of
wind turbines is increasing dramatically, “research and inter-agency
coordination is warranted to enhance capability for completing
timely determinations and developing measures for mitigating
readiness impacts.” The report focuses on the effects of windfarms
on air defence and missile warning radars, and the resulting
potential impact on military readiness.
Radar test results from multiple flight trials near windfarms were
performed by the UK Ministry of Defence, which showed that
utility-class turbines can have a significant impact on the
operational capabilities of military air defence radar systems, it
states. The results demonstrated that the large radar cross section
of a turbine, combined with the Doppler frequency shift produced by
its rotating blades, can impact the ability of a radar to
discriminate the turbine from an aircraft, and those tests
“demonstrated that the windfarms have the potential to degrade
target tracking capabilities as a result of shadowing and clutter
effects.”
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