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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]).
Small Wind Electric Systems 9
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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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
Small Wind Electric Systems 15
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
Small Wind Electric Systems 19
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