Source: NWCC
Guidelines
Successful wind project siting depends on
negotiation to balance concerns and benefits.
Details vary widely from site to site, but the
National Wind Coordinating Committee (NWCC)
recommends a few guidelines, including
significant public involvement, reasonable time
frames, clear decision criteria, coordinated
siting processes, expedited judicial review and
advance site planning.
Early public involvement allows the public to
have its interests factored in early in the siting
process. Without this, there is a much greater
likelihood of later opposition and costly
litigation. The public, particularly residents
living near a proposed site, should be notified
of the siting application, and the siting agency
should hold public meetings and accept public
comments.
Open siting processes with long delays are a
legitimate concern for wind developments.
Establishing reasonable time frames for review
of applications, hearings and a final decision
from the siting agency is one way to avoid
unnecessary delays.
The siting agency should make the criteria for
its decisions clear at the beginning. The agency
should list all the factors to be considered,
specify how the factors are weighed against
each other, and set minimum requirements to
be met by the project. The factors will vary
depending on the circumstances.
Land Use
Unlike most power plants, wind generation
projects are not land intensive. On a MW output
basis, the land required for a wind project
exceeds the amount of land required for most
other energy technology, but the physical
project footprint covers only a small portion of
that land. For example, a 50 MW wind facility
may occupy a 1,500-acre site, but it will only
use three to five percent of the total acreage,
leaving the remainder available for other uses.
Because wind generation is limited to areas
with strong and fairly consistent wind
resources, most wind generation is sited in rural
and relatively open areas that are often already
used for agriculture, grazing, recreation, forest
management or seasonal flood storage.
To ensure that a wind project is compatible
with existing land uses, the layout and design
of the wind project can be adjusted in a variety
of ways, including:
selecting equipment with minimal guy
wires,
placing electrical collection lines
underground,
placing maintenance facilities off site,
consolidating equipment on the turbine
tower or foundation,
consolidating structures within a selected
area,
using the most efficient or largest turbines
to minimize the number of turbines
required,
increasing turbine spacing to reduce
density of machines,
using roadless construction and
maintenance techniques, or
using existing access roads.
Other land use strategies include buffer zones
and setbacks to separate wind projects from
sensitive or incompatible land uses. Land use
agencies in California have established
setbacks ranging from two to four times the
height of a turbine or a minimum of 500 to
1,200 feet from any residential area. Minnesota
has established minimum setbacks of 500 feet
from occupied dwellings.
For the Birds
The problem of birds, especially raptors, flying
into wind turbines has been the most
controversial biological consideration affecting
wind siting. Wind developments have produced
enough bird collisions and deaths to raise
concern from wildlife agencies and conservation
groups. On the other hand, some large wind
facilities have been operating for years with
only minor impacts on birds. Smokestacks and
radio and television towers have actually been
associated with much larger numbers of bird
deaths than wind facilities have, and highways
and pollution account for a great many as well.
Whether or not this becomes a serious sighting
issue tends to depend on the protective status
or number of bird species involved. Most raptors
are protected by state and federal laws and any
threat to them may cause siting concerns.
Both the wind industry and government
agencies are sponsoring or conducting research
into this problem. Studies are under way
comparing mortality at lattice and tubular
towers and investigating birds' sensory
physiology and how it affects their ability to
detect components of wind turbines. One study
is painting colors on turbine blades to observe
birds' reactions.
Wind farms are thought to affect wildlife in
several other ways, including:
direct loss of habitat,
indirect habitat loss from increased human
presence, noise or motion of operating
turbines,
habitat alteration resulting from soil
erosion or construction of obstacles to
migration,
collision with structures, turbine blades or
wires, and
electrocution from contact with live
electrical wires.
The NWCC recommends several strategies for
dealing with biological resource siting issues
Planning and coordination with permitting
agencies can reduce the chances of project
delays. Most permitting agencies recommend
wind developers consult with them and
appropriate natural resource protection agencies
early in the site selection process to determine
the potential for conflicts. It is important to
find out whether protected plants and animals
inhabit, use or migrate through the area.
Unique or rare habitat types, such as savannas,
can raise interest and alternative sites may be
needed.
Biological surveys can be helpful, but the timing is important.
Some necessary information can only be obtained at a certain time
of the year. Protected plants may only bloom for a few weeks or
months at a time and bird use or migration patterns may need to be
studied over several seasons or years.
Equipment selection can reduce the risk of high
bird mortality, but the best plan is to avoid
sites near major bird feeding, roosting or
resting areas. Research is ongoing, but to date
there are no designs or modifications that have
been statistically proven to significantly reduce
the risk of bird collisions. Unless protected
plants or animals are involved, most permitting
agencies tend to find the non-collision effects
of wind development on wildlife to be
insignificant.
Visionary Planning
Visual or aesthetic concerns are also a common
issue in wind siting. Wind projects tend to be
located in rural or remote areas with few area
residential developments. Potential for visual
impact is sometimes considered as part of the
evaluation of land use, and the degree to which
the visual quality of a project is addressed will
vary. Elements that can influence the visual
impact of a wind project include spacing, design
and uniformity of the turbines, markings on
turbines and other structures, spacing of
turbines, design and uniformity of the turbines,
roads built on slopes, and service buildings.
There is considerable motion in turbine blades
and this motion is intensified when the turbines
are placed close together, are of different
designs or rotate in different directions.
Adequate spacing between turbines and
between rows or tiers of turbines mitigates
visual impact.
When turbines are sited on ridgelines, the units
are visible for greater distances. Against the
sloping terrain, surfaces exposed by
construction of access roads and turbine pads
may contrast with existing soils and vegetation.
From a distance, the visual impact of the roads
may be greater than that of the turbines.
Constructing roads on ridges also may increase
erosion.
It is generally recommended that developers
contact any agencies with jurisdiction for any
maps, plans, guidelines or design standards in
that particular area. Design strategies can be
used to reduce the visual impact, including:
using the local landscape to minimize
visibility of access and service roads and to
protect soils from erosion,
consolidation of roads or use of grating
over vegetation for temporary access
without road construction,
use of low-profile building designs,
use of uniform color, structure types, and
surface finishes,
consolidating electrical lines and roads into
a single right of way or corridor,
limiting the size, color and number of
labels on turbines,
limiting size and number of advertising
signs on fences and facilities, and
using air lift for transport of turbine
components and installation.
Calculating the Wind's Power
Because air has mass moving to form wind, it
has kinetic energy, calculated as:
Kinetic energy (joules) = 0.5 x M x V2
Where:
M = mass (kg)
V = velocity (meters/second)
To calculate power, which changes moment to
moment, calculate energy to equal power times
the time and density. The kinetic energy
equations can be converted to a flow equation
showing the power in the area swept by the
wind turbine rotor.
P = 0.5 x rho x A x V3
Where:
P = power in watts
Rho = air density
A = rotor swept area exposed to the wind (m2)
V = wind speed in meters/sec
This yields the power in a free flowing stream
of wind. It is impossible to extract all the power
from the wind because some flow must be
maintained through the rotor. More terms need
to be included in the equation to get a practical
equation for a wind turbine
P = 0.5 x rho x A x Cp x V3 x Ng x Nb
Where:
P = power in watts
Rho = air density
A = rotor swept area exposed to the wind (m2)
Cp = Coefficient of performance (0.59 is the
maximum theoretically possible and 0.35 is a
good design)
V = wind speed in meters/sec
Ng = generator efficiency (80 percent or more
for a permanent magnet generator or
grid-connected induction generator)
Nb = gearbox/bearings efficiency (up to 95
percent)
Source: Eric Eggleston and AWEA
Top 10 Permitting Issues
1.Land use
2.Noise
3.Birds and other biological resources
4.Visual resources
5.Soil erosion and water quality
6.Public health and safety
7.Cultural and paleontological resources
8.Socioeconomics, public services and
infrastructure
9.Solid and hazardous wastes
10.Air quality and climate
Source: NWCC
References:
"Wind Energy Issue Brief No. 3,"National Wind
Coordinating Committee, www.nationalwind.org
"Permitting of Wind Energy Facilities," National
Wind Coordinating Committee
"How Can I Calculate the Amount of Power
Available at a given Wind Speed?" Eric
Eggleston, www.awea.org