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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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