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Introduction to AlternativeIntroduction to AlternativeEnergiesEnergies
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What potential
does wind hold asan energy source
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Wind Power Wind power has been growing at an average
rate of 25% per year, making wind the fastest growing source of energy in the world since
Wind turbines use moving air to generateelectricity by rotating propeller-like blades
around a rotor, the rotor turns the drive shaft,which turns an electric generator
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Utility companies see wind farms as anenvironmentally attractive way to generateclean power for their customers, so thenumber of wind farms in the U.S. today israpidly increasing
environment by producing clean power , astronger economy by creating wind power-
related employment , and greater energy security by providing a domestic source of energy
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History of Wind PowerWind energy is not a new concept, but one that
has been around before the discovery of electricity
Wind ener has been around since ancienttimes where it was used to power sail boats
Later, wind energy was used, via windturbines, to grind wheat
In the American West, wind power was usedfor saw mills and pumps
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It is interesting to notethat the first windturbine used togenerate electricity wasbuilt in 1888 in
, This generator was a
multi-vane type with
144 vanes and weighedsome 40 tonshttp://www.windpower.org/en/pictures/brush.htm
which includes information and several pictures of the wind generator
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In the late 1930s and early1940s, propeller type windgenerators were developed
After World War II theresearch of wind generators
of oil and its preference forelectricity generation
Wind energy became of interest again, though, withthe 1973 oil crisis
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Interest in wind energycontinues with researchand developmentimproving thetechnology as is evident
cost for wind energy This cost went from 25
cents in 1980 to 5 centsin 1996 for one kWh
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Wind energy is attractive for the following reasons
It has no CO 2 emissionsThe operation of wind turbinesleaves no dangerous residuesuch as that from nuclear There are minimaldecommissioning costs, andthe land occupied from windfarms can be used for otherpurposes such agricultural
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What are the basic
types of wind turbines and
how do they produce energy
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Wind TurbinesThere are several different wind turbine
configurations includingDrag-type
-Magnus effect wind plantsVortex wind plants
The more common drag and lift-type will bediscussed in this section
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Later came the developmentof lift-type wind turbineswhere the force generated is90 to the direction the windis blowing
developments with lift-typeturbines, all of which can be
categorized as either vertical or horizontal
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The vertical lift-typehas a shaft that axially isperpendicular to thedirection of the windblowing
size Darrius designNote the man located
bottom right for sizecomparison
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Possible applications of Darrius turbines areshown here where theyare placed along theroadways using the
vehicles to generateelectricity
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The horizontal lift-typedesign has a shaft thataxially is parallel to thedirection of the windblowing
common, at leasttoday, wind turbines
we see across thecountry
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How a wind turbine works is relatively simple
www.clf.org/.../how_wind_turbine_works.jpg 19
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Most modern wind turbines havethree blades, and operate facinginto the wind
The wind turns the blades, whichspin a shaft, which connects to a
Big, efficient turbines can generateup to 3.6 megawatts each
One megawatt is enough to provide power to about 300 or more homes
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Principles of Aerodynamics Although beyond the scope of this course,
there are several principles of aerodynamicsthat are considered in the design of wind
These concepts of aerodynamics are the sameprinciples used in the design of aircraft
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This figure illustratesthe basic aerodynamicoperating principles
Wind passes over thesurfaces of the rotor
It passes more rapidlyover the longer
(upper) side creating alower- pressure areaabove the airfoil
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The pressuredifferential betweentop and bottom
surfaces results in aforce called
In an aircraft wing,this force causes the
wing to "rise," liftingthe aircraft off theground
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Since the blades of awind turbine areconstrained to move
in a plane with thehub as its center, thelift force causes
ro a on In addition to liftforce, a "drag" force
perpendicular to thelift force impedesrotor rotation
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A prime objective inwind turbine design isfor the blade to have a
relatively high lift-to-drag ratio
varied along thelength of the blade to
optimize the turbinesenergy output atvarious wind speeds
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How do wedetermine theamount of energy
available in our area
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Availability of Wind Energy If you captured all the wind energy available,
it would theoretically be around 3600 TW If you reduced this only to the wind energy
, Obviously we cannot cover all the land, but, if
we used only 10% of this, that would still
amount to 40 TW compared to the 7 TW used by humanity today
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40 TW compared to the 7 TW used by humanity today
Of course this is very optimistic and unrealistic because wind varies and
optimum con itions are rare y met
But you can see that there is great potential for an alternative energy source with wind
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Residential Wind GenerationResidential wind generators are available
today and relatively reasonable as shownSkystream 3.7 costs approximately $12,000 to $15,000 to
,
depending on your site. The generator itself costs $5,400.Depending on the tower and installation costs, wind speedaverage, rebates and local electricity costs, Skystream 3.7 canpay for itself in as quickly as 5 years.
Information taken from the Skystream 3.7 spec sheet at http://www.skystreamenergy.com
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From http://www.skystreamenergy.com
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Power of a Wind Turbine The power of a wind turbine is proportional to
the cube of the applied wind velocity Because of this cubic relationship, the wind
of a site for energy generation from wind Anemometers measure wind conditions,
including velocity, which has to be convertedto wind power density data
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You can roughly determine the power,annual output (kWh/year), by using thefollowing
Annual Output = 0.01328 x D 2 V 3
D2 is the diameter (ft) of the rotor squared
V 3
is the average wind velocity (mph) cubed
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For exampleDetermining the annual output (kWh) of a12 ft diameter (from the Skystream 3.7 specifications) wind turbine with averagewind velocity of 12.5 mph
Annual Output = 0.01328 x D 2 x V 3= 0.01328 x 12 2 x 12.5 3
= 0.01328 x 144 x 1953= 3735 kWh
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Having enough average wind speed is the primary concern in wind turbines
The manufacturers power ratings of windturbines are typically based on optimum windvelocities which may not be true for your area
T e average win ve ocity or area can efound from various internet sites similar to theone below for Ohio
http://www.windexplorer.com/Ohio/ohio.htm
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When looking at wind charts as theone from the noted
web page, be sure towatch the height
speeds are recorded;note this chart is at 30 meters
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Works Cited Da Rosa, A. V. (2005). Fundamentals of Renewable Energy Processes. Burlington, MA,
USA: Elsevier Inc.
Danish Wind Industry Association . (n.d.). Retrieved March 2008, from Windpower.org:http://www.windpower.org/en/pictures/brush.htm
US Department of Energy:http://www.eere.energy.gov/consumer/your_home/electricity/index.cfm/mytopic=10502
Research Institute for Sustainable Energy:http://www.rise.org.au/info/Tech/wave/index.html
http://www.nooutage.com/hydroele.htm#Mesuring%20Head%20&%20Flow
http://www.skystreamenergy.com
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