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Wind Turbines
https://pursuitengineering.blogspot.com/2017/02/wind-turbines.html
• A wind turbine works the opposite of a fan
• wind turbines use wind to make electricity.
• The wind turns the blades, which spin a shaft, which connects to a
generator and makes electricity.
• Wind turbines convert the kinetic energy in the wind into mechanical
power.
• This mechanical power can be used for specific tasks (such as grinding
grain or pumping water) or a generator can convert this mechanical
power into electricity.
• If the mechanical energy is then converted to electricity, the machine
is called a wind generator.
Types of Wind Turbines
Wind turbines are classified into two general types
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Horizontal axis
Vertical axis
A horizontal axis machine has its blades rotating on an axis
parallel to the ground
A vertical axis machine has its blades rotating on an axis
perpendicular to the ground
Horizontal-axis wind turbines (HAWT)
Theses wind turbines typically either have two or three
blades. These three-bladed wind turbines are operated
"upwind," with the blades facing into the wind.
Horizontal-axis wind turbines (HAWT)
Up-Wind Turbines
Some wind turbines are designed to
operate in an upwind mode (with the
blades upwind of the tower). Large
wind turbines use a motor-driven
mechanism that turns the machine in
response to a wind direction. Smaller
wind turbines use a tail vane to keep
the blades facing into the wind
Horizontal-axis wind turbines (HAWT)
Down-Wind Turbines
Other wind turbines operate in a
downwind mode so that the
wind passes the tower before
striking the blades. Without a tail
vane, the machine rotor
naturally tracks the wind in a
downwind mode.
Horizontal-axis wind turbines (HAWT)
Shrouded Wind Turbines
Some turbines have an
added structural design
feature called an
augmentor. The
augmentor is intended
to increase the amount
of wind passing through
the blades.
Vertical-axis wind turbines (VAWT)
Vertical-axis wind turbines (VAWT)
Savonius Wind Turbine
The Savonius turbine is S-shaped if
viewed from above. This drag-type
VAWT turns relatively slowly, but
yields a high torque. It is useful for
grinding grain, pumping water, and
many other tasks, but its slow
rotational speeds make it unsuitable
for generating electricity on a largescale
Vertical-axis wind turbines (VAWT)
Flapping Panel Wind
Turbine
This illustration shows
the wind coming from
one direction, but the
wind can actually come
from any direction and
the wind turbine will
work the same way
Vertical-axis wind turbines (VAWT)
Darrieus Wind Turbine
The Darrieus turbine is
the most famous vertical
axis wind turbone. It is
characterized by its Cshaped rotor blades
which give it its
eggbeater appearance.
It is normally built with
two or three blades.
Vertical-axis wind turbines (VAWT)
Giromill Wind Turbine
The giromill is typically
powered by two or three
vertical aerofoil’s attached to
the central mast by
horizontal supports. Giromill
turbines work well in
turbulent wind conditions
and are an affordable option
where a standard horizontal
axis windmill type turbine is
unsuitable
Parts of a Wind Turbine
• The nacelle contains the key components of the wind turbine,
including the gearbox, and the electrical generator.
• The tower of the wind turbine carries the nacelle and the
rotor. Generally, it is an advantage to have a high tower, since
wind speeds increase farther away from the ground.
• The rotor blades capture wind energy and transfer its power
to the rotor hub.
• The generator converts the mechanical energy of the rotating
shaft to electrical energy
• The gearbox increases the rotational speed of the shaft for
the generator
Installing a Wind Turbine
• The basic steps for installing a small wind turbine on your
property are:
• Determine whether the wind resource in your area
makes a small wind system economical.
• Determine your household electricity needs by checking
your monthly or yearly electricity usage.
• Find out whether local zoning ordinances allow wind
turbine installations.
• Purchase and install a wind turbine sized to the needs of
your household.
Siting a Wind Farm
• Winds
Minimum class 4 desired for utility-scale wind farm (>7
m/s at hub height)
• Transmission
Distance, voltage excess capacity
• Permit approval
Land-use compatibility
Public acceptance
Visual, noise, and bird impacts are biggest concern
• Land area
Economies of scale in construction
Number of landowners
Advantages of Wind Power
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Environmental
Economic Development
Fuel Diversity & Conservation
Cost Stability
small project size
Short/flexible development time
Dispatch ability
Disadvantages
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Generally remote location
Grid connectivity -- lack of transmission capability
Intermittent output only when the wind blows
Low capacity factor
Birds of Prey (hawks, owls, golden eagles) in jeopardy
Shutting down all the turbines for at least two months
each winter
• Replace all before permits expire in 13 years
Wind Energy and Power
Atmospheric pressure differences accelerate and
impart kinetic energy into the air
Wind energy conversion machines (WEC) convert
wind energy into electrical or mechanical forms
How much power can we extract?
Wind Energy Natural Characteristics
• Wind Speed
Wind energy increases with the cube of the wind
speed 10% increase in wind speed translates into 30%
more electricity
2X the wind speed translates into 8X the electricity
Wind energy increases with height to the 1/7 power
2X the height translates into 10.4% more electricity
• Air density
Wind energy increases proportionally with air density
Humid climates have greater air density than dry
climates
Lower elevations have greater air density than higher
elevations
Wind energy in Denver about 6% less than at sea level
Blade swept area
Wind energy increases proportionally with swept area
of the blades
• Blades are shaped like airplane wings
10% increase in swept diameter translates into
21% greater swept area
Longest blades up to 413 feet in diameter,
resulting in 600 foot total height
• Height
Wind energy increases with height to the 1/7
power
2X the height translates into 10.4% more
electricity