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Small Wind

ElectricSystems

Small Wind

ElectricSystemsA Guide

Produced for theTennessee Valley

Authority


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Small Wind Electric Systems

Cover photo:This 10-kW Bergey wind turbine at the Alfred State College Farm in New York providespower for the dairy farm and feeds excess energy generated into the utility grid. AWS Scientific, Inc./ PIX13170.


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IntroductionCan I use wind energy to power my

home? This question is being askedacross the country as more peoplelook for affordable and reliablesources of electricity.

Small wind electric systems canmake a significant contribution toour nation's energy needs. Althoughwind turbines large enough to pro-vide a significant portion of the elec-tricity needed by the average U.S.home generally require one acre of property or more, approximately21 million U.S. homes are built onone-acre and larger sites, and 24%of the U.S. population lives in ruralareas.

A small wind electric system willwork for you if:

There is enough wind where youlive

Tall towers are allowed in yourneighborhood or rural area

You have enough space

You can determine how muchelectricity you need or want toproduce

It works for you economically.

The purpose of this guide is to pro-vide you with the basic informationabout small wind electric systems tohelp you decide if wind energy willwork for you.

Why Should I Choo se Wind?

Wind energy systems are one of themost cost-effective home-basedrenewable energy systems.

Small Wind Electric Systems 1

ContentsIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1First, How Can I Make My Home More Energy Efficient? . . . .2Is Wind Energy Practical for Me? . . . . . . . . . . . . . . . . . . . . . .3

What Size Wind Turbine Do I Need? . . . . . . . . . . . . . . . . . . . .4What are the Basic Parts of a Small Wind Electric System? . .5What Do Wind Systems Cost? . . . . . . . . . . . . . . . . . . . . . . . .7Where Can I Find Installation and Maintenance Support? . . . .8How Much Energy Will My System Generate? . . . . . . . . . . . .9Is There Enough Wind on My Site? . . . . . . . . . . . . . . . . . . . .11How Do I Choose the Best Site for My Wind Turbine? . . . . .14Can I Connect My System to the Utility Grid? . . . . . . . . . . . .15Can I Go "Off-Grid"? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Glossary of Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21For More Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

Small Wind Electric SystemsA U.S. Consumer's Guide

Homeowners, ranchers, and small businesses can use wind-generated electricity to reduce their utility bills. This grid-connected system installed for a home in Norman, Oklahoma,reduces the homeowner's utility bill by $100 per month.

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Is Wind Energy Practicalfor Me?A small wind energy system canprovide you with a practical andeconomical source of electricity if:

your property has a good windresource

your home or business is located on

at least one acre of land in a ruralarea

your local zoning codes orcovenants allow wind turbines

your average electricity bills are$150 per month or more

your property is in a remotelocation that does not have easyaccess to utility lines

you are comfortable with long-terminvestments.

Zoning Issues

Before you invest in a wind energysystem, you should research potentialobstacles. Some jurisdictions, forexample, restrict the height of the

structures permitted in residentiallyzoned areas, although variances areoften obtainable. Most zoning ordi-nances have a height limit of 35 feet.You can find out about the zoningrestrictions in your area by callingthe local building inspector, board of supervisors, or planning board. Theycan tell you if you will need to obtain

a building permit and provide youwith a list of requirements.

In addition to zoning issues, yourneighbors might object to a windmachine that blocks their view, orthey might be concerned about noise.Most zoning and aesthetic concernscan be addressed by supplying objec-tive data. For example, the ambientnoise level of most modern residentialwind turbines is around 52 to 55 deci- bels. This means that while the soundof the wind turbine can be picked outof surrounding noise if a consciouseffort is made to hear it, a residential-sized wind turbine is no noisier thanyour average refrigerator.


In Clover Valley,Minnesota, this3-kW WhisperH175 turbine on a50-foot tower isconnected to theutility grid to offsetthe farm's utility-supplied electricity.

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Although small wind turbines arevery sturdy machines, they do requiresome annual maintenance. Bolts andelectrical connections should bechecked and tightened if necessary.The machines should be checked forcorrosion and the guy wires forproper tension. In addition, youshould check for and replace any

worn leading edge tape on the blades,if appropriate. After 10 years, the blades or bearings may need to bereplaced, but with proper installationand maintenance, the machine shouldlast up to 20 years or longer.If you do not have the expertise tomaintain the machine, your installermay provide a service and mainte-nance program.

How Much Energy Will MySystem Generate?Most U.S. manufacturers rate theirturbines by the amount of power theycan safely produce at a particularwind speed, usually chosen between24 mph (10.5 m/s) and 36 mph(16 m/s). The following formulaillustrates factors that are importantto the performance of a wind turbine.Notice that the wind speed, V, has an

exponent of 3 applied to it. Thismeans that even a small increase inwind speed results in a large increasein power. That is why a taller towerwill increase the productivity of anywind turbine by giving it access tohigher wind speeds as shown in theWind Speeds Increase with Heightgraph. The formula for calculating

the power from a wind turbine is:Power = k Cp 1/2 A V3

Where:P = Power output, kilowattsCp = Maximum power coefficient,

ranging from 0.25 to 0.45,dimension less (theoreticalmaximum = 0.59)

= Air density, lb/ft3

A = Rotor swept area, ft2or D2/4 (D is the rotordiameter in ft, = 3.1416)

V = Wind speed, mphk = 0.000133 Aconstant to yield

power in kilowatts. (Multiplyingthe above kilowatt answer by1.340 converts it to horse-power. [i.e., 1 kW = 1.340horsepower]).


8

7

6

5

4

3

2

1

0

1 2 3 4 5 6 7Rotor Diameter, m

R o

t o r

D i a m e

t e r , m

Relative Size of Small Wind Turbines40

30

20

10

0

S w e p

t a r e a ,

m 2

7 m

6 m

5 m

4 m

3 m

2 m

1 m 0 2 9 7 9 3 0 3 m

Source: Paul Gipe,Wind Energy Basics


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Small Wind Electric Systems12


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and trees, and it needs to be 30 feetabove anything within 300 feet. Youalso need enough room to raise andlower the tower for maintenance, andif your tower is guyed, you mustallow room for the guy wires.Whether the system is stand-aloneor grid-connected, you will also need

to take the length of the wire run between the turbine and the load(house, batteries, water pumps, etc.)into consideration. A substantialamount of electricity can be lost as aresult of the wire resistancethelonger the wire run, the more electric-ity is lost. Using more or larger wirewill also increase your installationcost. Your wire run losses are greaterwhen you have direct current (DC)instead of alternating current (AC).So, if you have a long wire run, it isadvisable to invert DC to AC.

Can I Connect My Systemto the Utility Grid?Small wind energy systems can beconnected to the electricity distribu-tion system and are called grid-connected systems. Agrid-connectedwind turbine can reduce your con-sumption of utility-supplied electrici-ty for lighting, appliances, andelectric heat. If the turbine cannotdeliver the amount of energy you

need, the utility makes up the differ-ence. When the wind system producesmore electricity than the householdrequires, the excess is sent or sold tothe utility.Grid-connected systems can be practi-cal if the following conditions exist: You live in an area with average

annual wind speed of at least10 mph (4.5 m/s). Utility-supplied electricity is

expensive in your area (about 10 to15 cents per kilowatt-hour).

The utility's requirements forconnecting your system to its gridare not prohibitively expensive.

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

Federal regulations (specifically, thePublic Utility Regulatory Policies Actof 1978, or PURPA) require utilitiesto connect with and purchase powerfrom small wind energy systems.However, you should contact yourutility before connecting to their dis-tribution lines to address any powerquality and safety concerns. Yourutility can provide you with a list of requirements for connecting your sys-tem to the grid. The American WindEnergy Association is another goodsource for information on utility


20 H2 H

Obstruction of the Wind by a Buildingor Tree of Height (H)

0 2 9 7 9 3 0 7 m

H2 H

Regionof highlyturbulent

flow

The farther youplace your windturbine fromobstacles suchas buildings ortrees, the lessturbulence youwill encounter.


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Can I Go "Off-Grid"?Hybrid Systems

Hybrid wind energy systems canprovide reliable off-grid power forhomes, farms or even entire com-munities (a co-housing project, forexample) that are far from the nearestutility lines. According to manyrenewable energy experts, a "hybrid"system that combines wind andphotovoltaic (PV) technologies offersseveral advantages over either singlesystem. In much of the United States,wind speeds are low in the summerwhen the sun shines brightest andlongest. The wind is strong in thewinter when there is less sunlightavailable. Because the peak operatingtimes for wind and PV occur at differ-ent times of the day and year, hybridsystems are more likely to producepower when you need it. (For moreinformation on solar electric orPV systems, contact the EnergyEfficiency and Renewable EnergyClearinghousesee For MoreInformation.)

For the times when neither the windnor the PV modules are producing,most hybrid systems provide power

through batteries and/or an engine-generator powered by conventionalfuels such as diesel. If the batteriesrun low, the engine-generator canprovide power and recharge the bat-teries. Adding an engine-generatormakes the system more complex, butmodern electronic controllers canoperate these systems automatically.An engine-generator can also reducethe size of the other componentsneeded for the system. Keep in mindthat the storage capacity must belarge enough to supply electrical

needs during non-charging periods.Battery banks are typically sized tosupply the electric load for one tothree days.An off-grid hybrid system may bepractical for you if: You live in an area with average

annual wind speed of at least9 mph (4.0 m/s).

A grid connection is not availableor can only be made through an


Regulation andconversion

Load

Battery bank

AC orDC

Windturbine

PV modules

Generator

Hybrid Power SystemsCombine multiple sources to deliver non-intermittent electric power

0 2 9 7 9 3 0 1 m

A hybrid systemthat combines awind system with asolar and/or dieselgenerator canprovide reliable off-grid power aroundthe clock.


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Government Agencies

Energy Efficiency and RenewableEnergy Clearinghouse, P.O. Box 3048,Merrifield, Virginia 22116 800-DOE-EREC (363-3732). http://www.eren.doe.govNational Climatic Data Center,Federal Building, 151 Patton Avenue,Asheville, North Carolina, 28801-5001.(828) 271-4800. Fax (828) 271-4876.http://www.ncdc.noaa.govU.S. Department of Commerce,National Technical InformationService, 5285 Port Royal Road,Springfield, Virginia 22161. (800)553-6847. http://www.ntis.gov/ordering.htm

Non-Government Organizations

American Wind Energy Association,122 C Street, N.W. 4th Floor,Washington, D.C. 20001. (202) 383-2500. http://www.awea.orgSolar Energy InternationalShortcourses on renewable energy andsustainable development, inCarbondale, Colorado. (970) 963-8855.http://www.solarenergy.org

Periodicals

"Apples and Oranges" by Mick SagrilloAcomprehensive compari-son of available small wind turbines.On Home Power Magazine Web site:http://www.homepower.comHome Power MagazineThe defini-tive bimonthly magazine for thehomemade power enthusiast.(800)707-6586 or on the Web at:http://www.homepower.com

Videos

An Introduction to Residential WindSystems with Mick SagrilloA63-minute video answering questionsmost often asked by homeownersas they consider purchasing andinstalling their own wind power

systems. Order from AWEA (202) 383-2500, http://www.awea.org

Web Sites

AWEASmall Wind Systems WebsiteIncludes answers to frequentlyasked questions and information onU.S. manufacturers. http://www.awea.org/smallwind.html

Database of State Incentives forRenewable EnergyOn the Web athttp://www.dcs.ncsu.edu/solar/dsire/dsire.htmlGreen Power Network Net MeteringWeb SiteNet metering programs arenow available in 30 states. Visit thisDOE Web site for information:http://www.eren.doe.gov/greenpower/netmeteringSmall Wind "Talk" on the WebAWEA's Home Energy Systems elec-tronic mailing list is designed as a

forum for the discussion of small-scaleenergy systems that include wind. Tosubscribe, send a subscription [email protected] Energy for HomeownersThisWeb site discusses things you shouldconsider before investing in a smallwind energy system and provides basic information about the systems.http://www.eren.doe.gov/wind/homeowner.html



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TVA Green Power Switch GenerationPartners ProgramTVA and participating power distributors currently

offer a dual metering option to residential and smallcommercial consumers (non-demand metered)through the Green Power Switch GenerationPartners Program. The output (green power)generated from this program will be counted asa TVA Green Power Switch resource.Through this program, TVA will purchase the entireoutput of a qualifying system ($0.15 per kWh)through a participating power distributor, and thesystem owner will receive a credit for the powergenerated. Participation in this program is entirelyat the discretion of the power distributor. Until atotal capacity of 150 kW has been reached, theowner of a qualifying residential system will receivea $500 payment (only one $500 payment per site)when the site is connected to the grid. The credit of$0.15/kWh is available for a minimum of 10 yearsfrom the signing of the contract, regardless of theamount produced.Qualifying sources include wind turbine systems witha minimum output of 500 W AC and a maximum of50 kW. Qualifying systems must be used primarily toprovide all or part of the energy needs at a particularsite and must not have previously generated powerfor the grid. Installations must also comply with localcodes and adhere to specific interface guidelinesestablished by the program.

Participating Power Distributors include:Caney Fork Electric Cooperative, McMinnville,Tennessee; Dickson Electric Department, Dickson,Tennessee; Harriman Utility Board, Harriman,Tennessee; Lenoir City Utilities Board, Lenoir City,Tennessee; Prentiss County Electric PowerAssociation, Booneville, Mississippi; and SevierCounty Electric System, Sevierville, Tennessee.For more information, go to www.tva.com/ greenpowerswitch/partners/index.htm.

Contact:Gary HarrisTennessee Valley AuthorityGreen Power SwitchP.O. Box 292409, OCP- 2E-400Nashville, TN 37229-2409Phone: (615) 232-6124Fax: (615) 232-6038E-mail: [email protected] site: www.tva.com/greenpowerswitch/ There are seven states in TVAs power serviceterritory, including Alabama, Georgia, Kentucky,Mississippi, North Carolina, Tennessee, and Virginia.Information on incentives for small wind projectsin any of these states can be found by going toThe Database of State Incentives for RenewableEnergy (DSIRE), which can be accessed at www.dsireusa.org. DSIRE is a comprehensive source ofinformation on state, local, utility, and selected fed-eral incentives that promote renewable energy.

Small Wind Electric Systems

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Other Contacts

Dwight BaileyU.S. Department of EnergyAtlanta Regional Office75 Sprint Street, S.W.Atlanta, GA 30303-3308

Phone: (404) 562-0564Fax: (404) 562-0538E-mail: [email protected] site: www.eere.energy.gov/aro

Wind Powering Americawww.windpoweringamerica.gov

A Strong Energy Portfolio for a Strong AmericaEnergy efficiency and clean, renewable energy will mean a stronger economy, a cleaner environment, and greater energyindependence for America. Working with a wide array of state, community, industry, and university partners, the U.S.Department of Energys Office of Energy Efficiency and Renewable Energy invests in a diverse portfolio of energy technologies.

Produced for the U.S. Department of Energy by theNational Renewable Energy Laboratory,a DOE national laboratory

For more information contact:EERE Information Center1-877-EERE-INF (1-877-337-3463)

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