8492744 Small Scale Wind Energy

8/8/2019 8492744 Small Scale Wind Energy

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This publication draws heavily on SmallWind Electric Systems: A U.S. Consum-ers Guide (DOE/GO-102005-2095), pro-duced by the National Renewable Energy Laboratory (NREL). Material from this

publication is reprinted and adapted herewith permission from NREL.

A Publication of ATTRA - National Sustainable Agriculture Information Service 1-800-346-9140 www.attra.ncat.org

ATTRANational SustainableAgriculture Information Ser-vice is managed by the NationalCenter for Appropriate Technol-ogy (NCAT) and is funded undera grant from the United StatesDepartment of AgriculturesRural Business-CooperativeService. Visit the NCAT Web site (www.ncat.org/agri.html ) for more informa-tion on our sustainableagriculture projects.

Funding for the developmentof this publication was providedby the USDA Risk ManagementAgency.

Contents

By Cathy SvejkovskyNCAT Energy Specialist 2007 NCAT

Small-Scale Wind Energon the FarmWind-generated electricity is attracting the interest of farmers, ranchers, and other landowners acrossthe country. People nd wind energy attractive for a variety of reasons, including its potential economicbenets and its lower impact on the environment when compared to coal and other electric powergeneration fuels. Wind-generated electricity can help farmers and ranchers reduce their energy costs,an important consideration in these days of continually increasing utility rates.

This publication will introduce you to small-scale wind energy to help you decide if wind energy is aneconomical option for your farm or ranch.

IntroductionWind energy systems use the windto generate electricity with a windturbine. More and more peopleare considering wind energy asthey look for affordable and reli-

able sources of electricity. Smallwind electric systems can makean important contribution to ournations energy needs. In 2005,the United States installed more new windenergy capacity than any other country inthe world. The new capacity, totaling 2,431megawatts (MW), was worth more than$3 billion in generating equipment, and itbrought the total national wind energy capac-ity to 9,149 MW. Thats enough electricity topower 2.3 million average American house-holds. In 2006, an additional 2,454 MWwas installed, bringing the nations totalinstalled capacity to 11,603 MW.

Many rural areas have sufficient windspeeds to make wind an attractive alterna-tive, and farms and ranches can often installa small-scale wind energy system withoutimpacting their ability to plant crops andgraze livestock. Most farms and rancheshave enough open land (generally an acre

Farms and ranches, such as this one in southwest Minnesota,can use wind-generated electricity to reduce utility bills.Photo courtesy of NREL.

or more) to provide a signi cant portion of their electricity from wind power.

Why Should I Choose Wind?Wind energy can be a cost-effective small-scale renewable energy system. Depend-ing on your wind resource and the electricconsumption on your farm, a small windenergy system can lower electricity bills,help avoid the high costs of extending util-ity power lines to remote locations, preventpower interruptions, and provide a non-pol-luting source of electricity.

How Do Wind Turbines Work?Wind is created by the unequal heating of the Earths surface by the sun. Wind tur-bines convert the kinetic energy in wind

Introduction ..................... 1Why Should I ChooseWind? .................................. 1How Do Wind TurbinesWork? .................................. 1Is Wind Energy Practicalfor Me? ............................... 2Is There Enough Wind atMy Site? .............................. 3Zoning Issues ................... 4What Size Wind TurbineDo I Need? ......................... 4What are the Basic Partsof a Small Wind ElectricSystem? .............................. 5What Do Wind SystemsCost? .................................... 7How Much Energy WillMy System Generate? ... 7

Grid-ConnectedSystems .............................. 8Can I Sell My ExcessElectricity to theUtility? ................................ 9Financial Incentives ....... 9References ...................... 10


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Page 2 ATTRA Small-Scale Wind Energy on the Farm

Related ATTRAPublications

into mechanical power that runs a genera-tor to produce clean electricity. Todays tur-bines are versatile sources of electricity.Their blades are aerodynamically designedto capture the maximum energy from thewind. The wind turns the blades, whichspin a shaft connected to a generator thatmakes electricity.

Is Wind Energy Practical for Me?A small wind energy system can provideyou with a practical and economical sourceof electricity if:

your property has a good windresource

you have at least one acre of land ina rural area

your local zoning codes or covenantsallow wind turbines

you have high electric costs

your property is in a remote loca-tion that does not have easy accessto utility lines

you are comfortable with long-terminvestments

Its important to examine your reasons forwanting to purchase a wind energy system. If your reasons are purely economic, you couldend up disappointed, since wind energysystems can have long payback periods. If

you are also interested in bene ts such asenvironmental protection, independence,or energy security, you may nd the costand payback period to be perfectly accept-able. Make sure you fully understand theresults you can expect, as well as potentialobstacles, such as zoning laws, generationcapacity, maintenance requirements, andwarranty coverage.

Renewable EnergyOpportunities onthe Farm

Wind-PoweredElectric Systems forHomes, Farms, andRanches: Resources

Effi cient AgriculturalBuildings: AnOverview

Wind turbines operate in harmony with farming and ranching. Photo courtesy of NREL.

First Things First:Make Your Farm Buildings asEnergy-Effi cient as Possible

Before choosing a wind system for your farmor ranch, you should reduce your energy con-sumption as much as possible. This topicis discussed in greater detail in the ATTRApublication Effi cient Agricultural Buildings: An Overview . Energy conservation is almostalways more cost-effective than renewableenergy systems, and could reduce the size of your wind energy system. From wall insula-tion to light bulbs, there are many ways tomake your farm buildings more effi cient.

Reduce your heating and cooling needs byup to 30% by investing just a few hundreddollars in proper insulation and weather-ization products.

Save money and increase comfort by prop-erly maintaining and upgrading your heating,ventilation, and air-conditioning systems.

Install double-paned, gas-lled windowswith low-emissivity (low-e) coatings toreduce heat loss in cold climates and spec-trally selective coatings to reduce heat gainin warm climates.

Replace your lights in high-use areas with u-orescents. Replacing 25% of your lights cansave about 50% of your lighting energy bill.

When shopping for products such as light-ing, windows, and heating and coolingsystems, look for the ENERGY STAR label.ENERGY STAR products have been identi-ed by the U.S. Environmental ProtectionAgency and U.S. Department of Energy asbeing the most energy-effi cient productsin their classes.


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Page 3 ATTRA www.attra.ncat.org

Is There Enough Wind atMy Site?Does the wind blow hard and consistentlyenough at your site to make a small windturbine system economically worthwhile?That is a key question and not always eas-ily answered. The wind resource can varysigni cantly over an area of just a few milesbecause of local terrain in uences on thewind ow. Yet, there are steps you can takethat can help answer this question.

As a rst step, a wind resource map canhelp you estimate the wind resource inyour region. State wind resource maps,such as those found on the Wind Pow-ering America website ( www.eere.energy.

gov/windandhydro/windpoweringamerica/ wind_maps.asp ) will help you understandthe resources in your specific region.Note that maps for some states show windspeed estimates at 50 meters above theground and depict the resource that couldbe used for utility-scale wind develop-ment. DOEs future plans include provid-ing wind speed estimates at 30 meters,which are useful for identifying smallwind turbine opportunities.

You can nd additional wind resourcemaps, showing region-speci c data, in

NRELs Wind Energy Resource Atlasof the United States, available online athttp://rredc.nrel.gov/wind/pubs/atlas. Forwestern regions, consult windpowermaps.org and The Renewable Energy Atlas of the West, available at www.energyatlas.org . For California only, consult Califor-nia Wind Resource Maps at www.energy.ca.gov/maps/wind.html. Note that windmaps provide only broad est imatesthewind speed for any part icular site is oftena prediction based on terrain, ratherthan an actual measurement. The actualwind resource at a speci c site may differconsiderably from these estimates. Forsite-speci c wind resource data, consulta turbine dealer or install an anemometer(a device that measures wind speed) onyour property.

In general, the highest average windspeeds in the United States are found

along seacoasts, on ridgelines, and in theGreat Plains; however, many areas havewind resources strong enough to powera small wind turbine economically. Thewind resource estimates on the map abovegenerally apply to terrain features that arewell-exposed to the wind, such as plains,hilltops, and ridge crests.

Another way to estimate the wind resource

is to get average wind speed informationfrom a nearby airport. Use caution, how-ever, because local terrain and other factorsmay cause the wind speed recorded at anairport to be different from your particu-lar location. Also, airport wind speeds aregenerally measured at heights of only about20-33 feet (610 meters) above ground.

Average wind speeds increase with heightand may be 1525% greater at a typi-cal small wind turbine hub-height of 80

feet (24 meters) than those measured atairport anemometer heights. The NationalClimatic Data Center collects data fromairport s in the United States and makeswind data summaries available for pur-chase. Summaries of wind data fromalmost 1,000 U.S. airports also areincluded in Wind Energy Resource Atlasof the United States, available online athttp://rredc.nrel.gov/wind/pubs/atlas.

Source: U.S. Department of Energy.


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with your local wind speed and your energybudget, will help you decide what size of turbine will best meet your electric needs.

What are the Basic Parts of aSmall Wind Electric System?Home-scale wind energy systems are gen-erally comprised of a rotor, a generator oralternator mounted on a frame, a tail, a tower, wiring, and the balance of systemcomponents: controllers, inverters, and/or batter ies. Through the spinning blades,the rotor captures the kinetic energy of thewind and converts it into rotary motion todrive the generator.

To find wind equipment suppliers andinstallers in your area, as well as sourcesof technical support, see ATTRAs Farm

Energy Search Toolat

http://attra.ncat.org/ energy.php

Wind TurbineMost turbines manufactured today are hor-izontal-axis, upwind machines (the rotorfaces the wind) with two or three blades,which are usually made of a compositematerial such as berglass. These machinesare designed so that turbines rotate arounda horizontal axis, and the rotor is placed on

the windward side of the support tower.The amount of power a turbine wil l produceis determined primarily by the diameter of its rotor. The diameter of the rotor de nes

its swept area, or the quantity of windintercepted by the turbine. The turbinesframe is the structure onto which the rotor,generator, and tail are attached. The tailkeeps the turbine facing into the wind.

Tower Because wind speeds increase with height,the turbine is mounted on a tower. In gen-eral, the higher the tower, the more energythe wind system can produce. The toweralso raises the turbine above the air tur-bulence caused by obstructions such ashills, buildings, and trees. As a generalrule of thumb, the bot tom of the rotorblades should be at least 30 feet (9 meters)above any obstacle that is within 300 feet(90 meters) of the tower. Relatively smallinvestments in increased tower height canyield very high rates of return in energyproduc tion. For instance, raising a 10-kWgenerator from a 60-foot tower height toa 100-foot tower increases system costby about 10%, but can increase energyproduction by 29%.

Mounting turbines on rooftops is not rec-ommended. All wind turbines vibrate andtransmit the vibration to the structure onwhich they are mounted. This can lead

to noise and structural problems with thebuilding, and the roo ine can cause exces-sive turbulence that will shorten the life of the turbine.

Balance of SystemThe parts that you need in addition to theturbine and the tower, or the balance of sys-tem parts, will depend on your application.Most manufac turers can provide you with a system package that includes all the parts

you need for your application. For exam ple,the parts required for a water pumping sys-tem will be much differ ent than what youneed for a residen tial application. The bal-ance of system required will also dependon whether the system is grid-connected(connected to the uti lity grid), stand-alone(independent of the utility grid), or part of a hybrid system (a power system that usesmore than one source of energywind and

Bergey XL-1 horizontal-axis upwind machine.Source: Bergey Windpower.


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photovoltaics, for example). For a residen-tial grid-connected application, the balanceof system parts may include a controller,storage batteries, a power conditioning unit(inverter), and wiring.

Stand-Alone SystemsStand-alone systems (systems not con-nected to the utility grid) often requirebatteries to store excess power for usewhen the wind is calm. They also needa charge controller to keep the batter-ies from overcharging. Deep-cycle batter-ies, such as those used for golf carts, candischarge and recharge 80% of their capac-

ity hundreds of times, which makes thema good option for remote renewable energysystems. Automotive batteries are shallow-cycle batteries and should not be used inrenewable energy systems because of theirshort life in deep-cycling operations.

Small wind turbines generate direct current(DC) electricity. In very small systems, DCappliances operate directly off the batter-ies. If you want to use standard appliancesthat use con ventional household alternatingcur rent (AC), you must install an inverterto convert DC electricity from the batteriesto AC. Although the inverter slightly lowersthe overall ef ciency of the system, it allows

Types of Towers

There are three basic types of towers suitable for farm-sized turbines:

Monopole This type of tower is generally the least expensive. The tower is a tilt-up style tower and isgenerally installed using a gin-pole and winch. Monopoles generally have four guy wiresfor support. Maintenance on the turbine is performed by tilting the tower down. Theheight of this type of tower is limited by the weight of the machine and generally 10-kWmachines are the largest that can be placed on such towers. Tilt-up towers require spacefor guy wires and for tipping up and down of the tower.

Guyed latticeGuyed lattice towers are generally more expensive than monopole designs but can sup-port larger turbines at higher heights. Towers are generally installed using gin-pole andwinch. Guyed lattice towers also come with the advantage of either being able to tip thetower down or relatively easy climb-ability for regular maintenance (climbing, if done

with appropriate safety precautions, gear and training,is much safer than tilting a tower up and down everytime maintenance is required). Guyed lattice towersrequire much space for tipping up and down of towerand guy wires. Again, check with turbine manufacturesto see what tower options they recommend with variousturbine models.

LatticeLattice towers, in most cases, are required for machineslarger than 20 kW in size. The installation of these towersis generally more complicated than that of a guyed lat-tice tower because a crane is needed to lift the tower andturbine into place. Maintenance is performed by climbingthe tower. If major work is required on a machine a cranemay be required to remove the turbine from the tower.Check with manufacturers to determine what toweroptions they recommend with different turbine models.

Monopole tower.

Lattice tower.

Guyed lattice tower .

Source: Windustry.org.


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the home to be wired for AC, a de nite pluswith lenders, electrical code of cials, andfuture homebuyers.

For safety, batteries should be isolated fromliving areas and electron ics because theycontain corrosive and explosive substances.Lead-acid batteries also require protec-tion from temperature extremes. Batteriesshould be enclosed in a box, which shouldbe vented to the outside.

What Do Wind Systems Cost?According to the American Wind EnergyAssociation (AWEA), small wind energysystems cost from $6,000 to $8,000 forevery kilowatt of generating capacity,depending on size. Smaller wind systemsare more costly per kilowatt of installedcapacity. Wind energy becomes morecost-effective as the size of the turbineincreases. Although small turbines costless in initial outlay, they are proportion-ally more expensive.

A 10-kW system, for example, can cost$47,000 to $60,000 installed. Rebates,tax credits, and other incentives can reducethese costs. Well-sited small wind turbinescan usually pay for themselves within 15years, about half their serviceable life-times, if the right incentives are applied,says AWEA.

Although wind energy systems involve a significant initial investment, they can

be competitive with conventional energysources when you account for a lifetime of reduced or avoided utility costs. The lengthof the payback periodthe time before thesavings resulting from your system equalthe cost of the system itselfdepends onthe system you choose, the wind resourceon your site, electric costs in your area, andhow you use your wind system.

How Much Energy Will MySystem Generate?As mentioned above, most U.S. manufac-turers rate their turbines by the amountof power they can safely produce at a par-ticular wind speed. Even a small increasein wind speed results in a large increasein power. That is why a taller tower willincrease the productivity of any wind tur-bine by giving it access to higher windspeeds, as shown in the graph below.

Can I Install a Wind EnergySystem Myself?

Most dealers offer either complete turn-key (ready-to-operate) installations or theoption to purchase direct from the fac-tory and install the system yourself. Therst option offers more customer supportfrom the company. Self-installation offerssignicant savings and a hands-on under-standing of the turbine. Prospective own-ers can discuss the options available withmanufacturers to decide which methodbest suits their budget and technical skills.

American Wind Energy Association

T o w e r

H e

i g h t ,

f t

Increase in wind power, %

Wind Speeds Increase with Height

0 41 75 100 1240

30

60

90

120

150


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The larger the rotor, the more energy it can

capture. The air density changes slightlywith air tempera ture and with elevation.The ratings for wind turbines are based onstandard conditions of 59 F (15 C) at sea level. A density correction should be madefor higher elevations as shown in the graphabove. A correction for temperature is typi-cally not needed for predicting the long-term perfor mance of a wind turbine.

The best mea sure of wind turbine perfor-mance is annual energy output. The dif-ference between power and energy is thatpower (kilowatts [kW]) is the rate at whichelectric energy is consumed, while energy(kilowatt-hours [kWh]) is the quantity con-sumed. An estimate of the annual energyoutput from your wind turbine, kWh/year,is the best way to determine whether a par-ticular wind turbine and tower will produceenough electric energy to meet your needs.

A wind turbine manufacturer or dealer

can help you estimate the energy produc-tion you can expect. They will use a cal-culation based on the particular wind tur-bine power curve, the average annual windspeed at your site, the height of the towerthat you plan to use, the elevation, and (if available) the frequency distribution of thewindan estimate of the number of hoursthat the wind will blow at each speed dur-ing an average year. Contact a wind turbine

manufacturer or dealer for assistance withthis calculation.

To get a preliminary estimate of the perfor-mance of a particular wind tur bine, use theformula below.

AEO = 0.01328 D2 V3

Where:

AEO = Annual energy output, kWh/year

D = Rotor diameter, feet

V = Annual average wind speed, mph

Wind Powering Americas Wind EnergyPayback Period Workbook is a spreadsheettool that can help you analyze the econom-ics of a small wind electric system anddecide whether wind energy will work foryou. The spreadsheet can be found online atwww.eere.energy.gov/windandhydro/ windpoweringamerica/docs/wind_payback.xls. The tool asks you to provide informationabout how youre going to nance the sys-tem, the characteristics of your site, and theproperties of the system youre considering.It then provides you with a simple payback estimate in years.

Grid-Connected Systems

Small wind energy systems can beconnected to the electric distribution sys-tem and are then called grid-connectedsystems. Grid-connected systems requirea power conditioning unit (inverter), whichmakes the turbine output electricallycompatible with the utility grid. Usually,batteries are not needed. A grid-con-nected wind turbine can reduce your con-sumption of utility-supplied electricity forlighting, appliances, and electric heat. If the turbine cannot deliver the amount of energy you need, the utility makes up thedifference. When the wind system pro-duces more electricity than the householdrequires, the excess is sent or sold to theutility. Grid-connected systems can bepractical if the following conditions exist:

You live in an area with averageannual wind speed of at least 10mph (4.5 m/s).

E l e v a t

i o n

, f t

Air Density Change with Elevation

0

1,000

80 85 90 100957570

2,000

3,000

4,0005,000

6,000

7,000

8,000

9,000

10,000


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Utility-supplied electricity is expen-sive in your area (about 10 to 15cents per kilowatt-hour).

The utilitys requirements for con-necting your system to its grid arenot prohibitively expensive.

There are good incentives for thesale of excess electricity or for thepurchase of wind turbines.

Can I Sell My ExcessElectricity to the Utility?Federal regulations (speci cally, the Pub-lic Utility Regulatory Policies Act of 1978,

or PURPA) require utilities to connectwith and purchase power from small windenergy systems. However, you must contact

your utility before connecting to its distribu-tion lines to address any power quality andsafety concerns. Be aware that some utili-ties are more welcoming to interconnectionthan others. It is important that, early onin your planning process, you contact yourutility to learn about its interconnectionpolicies and expected costs. The AmericanWind Energy Association is another goodsource for information on utility intercon-nection requirements.

Financial IncentivesFinancial incentives can make wind energymore affordable for farmers and ranchers.You can nd out what incentives exist atboth state and federal levels at the Databaseof State Incentives for Renewable Energy(DSIRE) at www.dsireusa.org.

Wind energy can be an attractive alterna-tive for farms and ranches across the coun-

try, offering numerous bene

ts, includingreduced energy costs, reduced environ-mental impact, and increased energy inde-pendence. However, as with all renewableenergy systems, there also are challengesto these systems. Conduct a careful analy-sis of your energy needs and wind resourcepotential, as well as system economics, ben-e ts, and potential obstacles, to see if windis a good choice for your farm or ranch.

A grid-connected wind turbinecan reduce your consumptionof utility-supplied electricity.

Source: U.S. Department of Energy.

Small wind turbines can provide supplemental power for farms and ranches, such as this farm in westernKansas. Excess power is fed back into the utility grid.Source: Warren Gretz, NREL.


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Advantages and Disadvantages of Wind Energy , U.S.Department of Energy, Wind & Hydropower Technolo-gies Program. www1.eere.energy.gov/windandhydro/ wind_ad.html

Consumers Guide to Renewable Energy in Arkansas,

Arkansas Energy Of

ce, October 2005.www.arkansasrenewableenergy.org/consumers_guide.pdf

The Consumers Guide to Small Wind and Solar Photo-voltaic Generation , NorthWestern Energy, 2007.

The Economics of Small Wind, American Wind EnergyAssociation. www.awea.org/smallwind/toolbox/TOOLS/

fs_economics.asp

Small Wind Electric Systems: A U.S. Consumers Guide,National Renewable Energy Laboratory, (NREL).March 2005. www.eere.energy.gov/windandhydro/

windpoweringamerica/pdfs/small_wind/small_wind_ guide.pdf

Wind Energy: Harnessing the Wind to Generate Elec-tricity, Environmental and Energy Study Institute , May2006. www.eesi.org/publications/Fact%20Sheets/EC_Fact_Sheets/Wind_Energy.pdf

Montana Wind Power: A Consumers Guide to Harness-ing the Wind, NorthWestern Energy , December 2004.www.montanagreenpower.com/pdf/montanawindpower

pub.pdf

Wind Powering America program brochure, www.eere.energy.gov/windandhydro/windpoweringamerica/pdfs/ wpa/35873_21century.pdf

ResourcesAmerican Wind Energy Associationwww.awea.org

Farm Energy Search Toolhttp://attra.ncat.org/energy.php

National Renewable Energy Laboratorywww.nrel.gov/wind

National Wind Coordinating Collaborativewww.nationalwind.org

Union of Concerned Scientistswww.ucsusa.org

U.S. Department of EnergyWind and Hydropower Technologies Programwww1.eere.energy.gov/windandhydro/

Windustrywww.windustry.org

Publications/LinksBurton, Tony, David Sharpe, Nick Jenkins, and ErvinBossanyi. Wind Energy Handbook, November 2001

Farming the Wind: Wind Power and Agriculture, Unionof Concerned Scientists. www.ucsusa.org/clean_energy/ renewable_energy_basics/farming-the-wind-wind-power-

and-agriculture.htmlGipe, Paul. Wind Energy Basics: A Guide to Smalland Micro Wind Systems, April 1999.

Gipe, Paul. Wind Power, Revised Edition: RenewableEnergy for Home, Farm, and Business. April 2004.

Paul, Greg, New and Improved Wind Power, MotherEarth News, June/July 2007. www.motherearthnews.com/Alternative-Energy/2007-06-01/Improved-Wind-Power.aspx

A Primer on Small Turbines, Bergey Windpower Co.www.bergey.com/School/Primer.html

Sullivan, Dan. Farming the Wind: The nuts and boltsof blade design, site selection and tower technology,The New Farm, www.newfarm.org/features/0504/ wind2.shtml

Wind Energy FAQs for Consumers, U.S. Department of Energy Wind and Hydropower Technologies Program.www1.eere.energy.gov/windandhydro/wind_consumer_

faqs.html

Wind Energy Payback Period Workbook, WindPowering America. www.eere.energy.gov/windandhydro/ windpoweringamerica/docs/wind_payback.xls

References


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Page 12 ATTRA

Small-Scale Wind Energy on the FarmBy Cathy SvejkovskyNCAT Energy Specialist 2007 NCAT

This publication is available on the Web at:www.attra.ncat.org/attra-pub/smallscalewindenergy.html orwww.attra.ncat.org/attra-pub/PDF/smallscalewindenergy.pdf

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8492744 Small Scale Wind Energy