Environmental Engineering Reference
In-Depth Information
In 2008, the Montana Public Service Commission set a rate up to $0.00565/MWh for integrated
wind power into the Northwestern Energy utility from the Two Dot wind farm. The integration rate
is then subtracted from the amount Northwestern Energy would pay the wind farm for power, which
would reduce the utility payment for wind-generated electricity to as low as $44.25/MWh.
11.3 REGULATIONS ON INSTALLATION AND OPERATION
Permits are required in residential areas for construction, and even in rural areas in some states. The
major zoning issues are tower height, setbacks, noise, aesthetics, environmental impact, and safety.
The probability of failure, such as a thrown blade, is the most common objection. However, risks
are accepted from other areas, such as cars, utility lines (electric and gas), etc. Signs, trees, and even
utility poles have failed in high winds or under conditions of icing.
Tower access needs to be controlled, as does access to the high voltage. One factor that can never
be dismissed is that anything that interferes with TV will be unacceptable to the public. When the
metal blades on the MOD-0A interfered with TV reception on Block Island, Rhode Island, the
DOE had to install cable for the residents. Most locations do not have specific zoning regulations
for wind turbines. Before installing a small wind turbine, be prepared to educate public boards and
your neighbors [9-13].
11.4 ENVIRONMENT
The main environmental issues are visual impact, noise, birds, and bats. The visual impact can
be detrimental, especially in locations that are close to scenic areas or parks. It is the same story:
people are in favor of renewable energy, but “not in my backyard.” The turbines should be drab
colors, not highly reflective, and the rotors should be rotating in the same direction.
Some people are adamantly opposed to wind farms, most are neutral, and the rest are in favor.
For those opposed, generally the visual impact is the most important concern [14]. The photo gal-
lery of Stopillwind has before and after photos of wind farms. The ones most in favor of wind farms
receive an economic return from the wind farm, whether directly or indirectly. The wind farm
developer needs to do community education as soon as the project is official. Economic develop-
ment in rural areas is very powerful from a political standpoint.
Noise measurements have shown in general that wind turbines are below the ambient noise;
however, the repetitive nose from the blades stands out, and one would not want a residence in the
middle of a wind farm. The whine from gearboxes on some units is also noticeable. However, with
larger wind turbines at higher hub heights and new airfoils, the noise has been much reduced. The
farmers who live close to the wind turbines at the White Deer, Texas, wind farm (eighty 1 MW
turbines) report that noise is not a problem.
The rotor area for a 90 m diameter wind turbine is over 6,000 m 2 , the rpm is around 10 revolu-
tions/min, and the velocity of the blades is different from the root to the tip. Large wind turbines
have a slower rpm than small wind turbines; however, the tip speed ratios are similar, so either
blade has a large enough velocity to kill a bird. So factors for the question of mortality of birds by
wind turbines are fatalities, bird species, season, the threat to the population, and possible forms of
mitigation [15]. Collision rates per turbine per year vary from 0.01 to 23; the latter was for a coastal
site in Belgium, which included gulls, terns, and ducks. Other coastal sites in northwest Europe had
yearly average collision rates ranging from 0.01 to 1.2 birds per turbine. None of these examples has
been associated with significant population decline. Flocks of geese and ducks entering an offshore
wind farm decrease by a factor of 4.5. At night, more migrating flocks entered the wind farm; how-
ever, they increased their distance from the wind turbines. Overall, less than 1% of the ducks and
geese flew close enough to the turbines to be at any risk of collision [16].
In general, migratory birds fly well above the heights of wind turbines [17]; however, overcast
and ground clouds may lower the flight paths. Two large wind farms near the coast, south of Corpus
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