Page 295 - Fluid Power Engineering

Environmental Impact of W ind Projects 261

for every 25 ft of radial distance from the airport edge. Note the above
specifies that any structure that is 200 ft or higher in height, regardless
of its proximity to an airport, requires FAA notification. Notification
is also required for temporary structures like met-towers that exceed
200 ft. in height above the ground level.
The criteria used by the FAA to deem a structure to be an ob-
struction to the navigable airspace is defined in http://edocket.access.
gpo.gov/cfr 2004/janqtr/pdf/14cfr77.23.pdf.
After the FAA completes the OE/AAA study, there are three pos-
sible outcomes:
1. No objection.
2. Conditional determination. The proposed project is acceptable
as long as the lighting and marking standards are imple-
mented.
3. Objectionable. The proposed project is determined to be a haz-
ard.
An objectionable ruling is not necessarily the death of a project.
TheFAAwillworkwithaprojectsponsortodeterminehowtheimpact
of structures can be mitigated. In the case of wind farm, this may
involve relocating a few turbines.

Electromagnetic Interference
Telecommunications towers use radio waves to transmit and receive
microwave, TV, radio, and radar signals. If a telecommunications
tower is in close vicinity of a wind turbine, then there is likely to be
interference with microwave antenna. A large wind turbine can
change the impedance of high-gain antenna that is used by microwave
signal. This interference is significant within a radius of 200 m.
Outside of this radius, interference is because of obstruction of the
direct signal or scattering of signal, which is described next.

Microwave
Microwave transmissions (300 MHz–300 GHz) are used for a vari-
ety of purposes, including backhaul in cellular networks, microwave
radio relay links for TV and telephone, and communication with
satellites. It is a line-of-sight transmission of radio signals in the mi-
crowave frequency range between a transmitting tower and receiving
tower. Microwave antennas are parabolic dishes in tall towers. In the
United States, the Federal Communications Commission (FCC) issues
licenses to operate microwave links and is a repository of all the in-
formation pertaining to locations of microwave towers.
Since the transmission is point-to-point and line-of-sight, interfer-
ence by moving blades of a turbine or any other part of the structure of