8492816 small wind electric systems

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LocationA home in Charlotte, Vermont

Capacity10 kilowatts

Turbine manufacturerBergey Windpower Company

Photo creditTrudy Forsyth, NREL/PIX09123

Small Wind Electric Systems

Location Wales Wind Energy Project, Wales, Alaska

Capacity 0.1 MW, completed in 2000

Turbine manufacturer Atlantic Orient Corporation

Developer Kotzebue Electric Association

Photo credit Steve Drouilhet, NREL/PIX09674

Capacity10 kilowatts

Turbine ManufacturerBergey Windpower Company

Photo creditBergey Windpower Company, NREL/PIX02102

LocationA ranch near Wheeler, Texas

Capacity1 kilowatt

Turbine manufacturerSouthwest WindPower

Photo CreditElliott Bayly

Location A farm in western Kansas

Capacity 10 kilowatts

Turbine manufacturer Bergey Windpower Company

Photo credit Warren Gretz, NREL/PIX09618

LocationA cabin in South Park, Colorado

Capacity600 watt

Turbine manufacturerSouthwest WindPower

Photo creditE. McKenna NREL/PIX04712


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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 ofsupervisors, 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 conscious

effort is made to hear it, a residential-sized wind turbine is no noisier thanyour average refrigerator.

Small Wind Electric Systems 3

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

WorldPowerTechnology/PIX07168


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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, theblades 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 their

turbines 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 V

3

Where:

P = Power output, kilowatts

Cp = Maximum power coefficient,ranging from 0.25 to 0.45,dimension less (theoreticalmaximum = 0.59)

= Air density, lb/ft3

A = Rotor swept area, ft2 orD2/4 (D is the rotordiameter in ft, = 3.1416)

V = Wind speed, mph

k = 0.000133 Aconstant to yieldpower 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

RotorDiameter,m

Relative Size of Small Wind Turbines

40

30

20

10

0

Sweptare

a,m2

7 m

6 m

5 m

4 m

3 m

2 m

1 m02979303m

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 runbetween 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 isexpensive 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 ofrequirements 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 Building

or Tree of Height (H)

02979307m

H

2 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 can

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

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


Regulation and

conversion

Load

Battery bank

AC or

DC

Windturbine

PV modules

Generator

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

02979301m

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.gov

National Climatic Data Center,Federal Building, 151 Patton Avenue,Asheville, North Carolina, 28801-5001.

(828) 271-4800. Fax (828) 271-4876.http://www.ncdc.noaa.gov

U.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.org

Solar Energy InternationalShortcourses on renewable energy andsustainable development, inCarbondale, Colorado. (970) 963-8855.http://www.solarenergy.org

Periodicals

"Apples and Oranges" by MickSagrilloAcomprehensive compari-son of available small wind turbines.On Home Power Magazine Web site:http://www.homepower.com

Home 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

AWEA Small 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.html

Green Power Network Net MeteringWeb SiteNet metering programs arenow available in 30 states. Visit thisDOE Web site for information:http://www.eren.doe.gov/greenpower/netmetering

Small 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].

Wind Energy for HomeownersThisWeb site discusses things you shouldconsider before investing in a smallwind energy system and providesbasic information about the systems.http://www.eren.doe.gov/wind/homeowner.html



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Notes

Small Wind Electric Systems


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U.S. Department of Energy Regional Officeswww.eren.doe.gov/rso.html

Atlanta Regional Office75 Spring Street, S.W., Suite 200Atlanta, GA 30303(404)562-0555http://www.eren.doe.gov/aro/

Boston Regional OfficeJFK Federal Building, Suite 675Boston, MA. 02203(617)565-9700http://www.eren.doe.gov/bro/

Chicago Regional OfficeOne South Wacker Drive, Suite 2380

Chicago, IL 60606-4616(312) 353-6749http://www.eren.doe.gov/cro/

Denver Regional Office1617 Cole Blvd. MS1721Golden, CO 80401(303) 275-4826http://www.eren.doe.gov/dro/

Philadelphia Regional Office

1880 John F. Kennedy Boulevard, Suite 501Philadelphia, PA 19103(215) 656-6950http://www.eren.doe.gov/pro/

Seattle Regional Office800 Fifth Ave., Suite 3950Seattle, WA 98104-3122(206)553-1132http://www.eren.doe.gov/sro/

States in Region

Alabama, Arkansas, Florida, Georgia,Kentucky, Mississippi, North Carolina,South Carolina, Tennessee, Puerto Rico,U.S. Virgin Islands

Connecticut, Maine, Massachusetts,New Hampshire, New York, Rhode Island,Vermont

Illinois, Indiana, Iowa, Michigan,

Minnesota, Missouri, Ohio, Wisconsin

Colorado, Kansas, Louisiana, Montana,Nebraska, New Mexico, North Dakota,Oklahoma, South Dakota, Texas, Utah,Wyoming

Delaware, Washington DC, Maryland,New Jersey, Pennsylvania, Virginia,West Virginia

Alaska, Arizona, California, Hawaii, Idaho,Nevada, Oregon, Washington, AmericanSamoa, Guam, Palau, North Marianas

U.S. Department of Energy

Office of Energy Efficiency and Renewable EnergyWind and Hydropower Technologies Program

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

DOE/GO-102001-1293May 2001, Revised October 2002

8492816 small wind electric systems

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