An

Arizona

Consumer's

Guide

Small Wind Electric Systems
Small Wind Electric Systems

Cover photo: This Whisper H40 wind turbine at the Northern Arizona University in Flagstaff supplies power to

the university's renewable energy instructional laboratory. Rob Slack, graduate research assistant at Northern

Arizona University/PIX13165.
our nation's energy needs. Althoughwind turbines large enough to provide a significant portion of the electricity needed by the average U.S.home generally require one acre ofproperty or more, approximately21 million

U.S. homes are built on

one-acre and larger sites, and 24%of the U.S. population lives in ruralareas.A small wind electric system

will

work for you if:• T

here is enough

wind w

here you

live

• Tall towers are allowed in your

neighborhood or rural area

• You

have enough space

• You can determine how

m

uch

electricity you

need or want to

produce

• It works for you economically.

T

he purpose of this guide is to provide you

with the basic information

about small wind electric systems tohelp you decide if wind energy willwork for you.Why Should I Cho

ose Wind?

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

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

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

Bergey Windpower/PIX01476
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d cooling

nvesting

ars in

proper insulation andweatherization products. 

• Save money and increase comfort

by properly maintaining andupgrading your heating,ventilation, and air-conditioningsystems. 

• Install double-paned, gas-filled

windows with low-emissivity (low-e) coatings to reduce heat loss in cold climates and spectrallyselective coatings to reduce heatgain in warm climates. 

• Replace your lights in high-use

areas with fluorescents. Replacing25% of your lights can save about50% of your lighting energy bill. 

• When shopping for appliances,

look for the ENERGY STAR® label.

ENERGY STAR® appliances have

been identified by the U.S.Environmental Protection Agencyand U.S. Department of Energy as being the most energy-efficientproducts in their classes.

• For more information on how to

make your home energy efficient,see Energy Savers, in the For MoreInformation section.

g

p

y 

yp

house is for heating and cooling.
p

• your property is in a remote

location that does not have easyaccess to utility lines

• you are comfortable with long-term

investments.

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

Most zoning and aesthetic concernscan be addressed by supplying objective data. For example, the ambientnoise level of most modern residentialwind turbines is around 52 to 55 decibels. This means that while the soundof the wind turbine can be picked outof surrounding noise if a consciouseffort is made to hear it, a residentialsized wind turbine is no noisier thanyour average refrigerator.

In Clover Valley,Minnesota, this 3-kW WhisperH175 turbine on a 50-foot tower isconnected to theutility grid to offsetthe farm's utilitysupplied electricity.

World Power Technology/PIX07168
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More Energy Efficient?). Wind turbinemanufacturers can help you size yoursystem based on your electricity needs and the specifics of local windpatterns.A typical home uses approximately9400 kilowatt-hours (kWh) of electricity per year (about 780 kWh permonth). Depending on the averagewind speed in the area, a wind turbine rated in the range of 5 to 15 kilowatts (kW) would be required tomake a significant contribution to thisdemand. A 1.5- kW wind turbine willmeet the needs of a home requiring300 kWh per month in a location witha 14-mile-per-hour (6.26-meters-persecond) annual average wind speed.The manufacturer can provide youwith the expected annual energy output of the turbine as a function ofannual average wind speed. The manufacturer will also provide information on the maximum wind speedat which the turbine is designed tooperate safely. Most turbines haveautomatic overspeed-governing systems to keep the rotor from spinningout of control in very high winds. Thisinformation, along with your localwind speed and your energy budget,will help you decide which size turbine will best meet your electricityneeds. 

speed over a specified period of time.

Blades—The aerodynamic surface

that catches the wind.

Brake—Various systems used to stop

the rotor from turning.

Converter—See Inverter.Cut-in wind speed—The wind speed

at which a wind turbine begins togenerate electricity.

Cut-out wind speed—The wind speed

at which a wind turbine ceases to generate electricity.

Density—Mass per unit of volume.Downwind—On the opposite side

from the direction from which thewind is blowing.

Furling—A passive protection for the

turbine where typically the rotor foldseither up or around the tail vane.

Grid—The utility distribution system. 

The network that connects electricitygenerators to electricity users.

HAWT—Horizontal axis wind turbine.Inverter—A device that converts direct

current (DC) to alternating current(AC).

kW—Kilowatt, a measure of power

for electrical current (1000 watts).

Power curve—A chart showing a

wind turbine's power output across a range of wind speeds.

PUC—Public Utility Commission, a

state agency which regulates utilities.In some areas known as Public Service

Commission (PSC).

PURPA—Public Utility Regulatory

Policies Act (1978), 16 U.S.C. § 2601.18CFR §292 that refers to small generator utility connection rules.

Rated output capacity—The output

power of a wind machine operating at the rated wind speed.

Rated wind speed—The lowest wind

speed at which the rated outputpower of a wind turbine is produced.

Rotor—The rotating part of a wind

turbine, including either the bladesand blade assembly or the rotatingportion of a generator.

Rotor diameter—The diameter of the

circle swept by the rotor.

Rotor speed—The revolutions per

minute of the wind turbine rotor.

Start-up wind speed—The wind speed

at which a wind turbine rotor willbegin to spin. See also cut-in windspeed.

Elliott Bayly/PIX09681
Most turbines manufactured todayare horizontal axis upwind machinesthat have two or three blades, whichare usually made of a composite material such as fiberglass. The amount of power a turbine willproduce is determined primarily bythe diameter of its rotor. The diameterof the rotor defines its "swept area," orthe quantity of wind intercepted bythe turbine. The turbine's frame is thestructure onto which the rotor, generator, and tail are attached. The tailkeeps the turbine facing into thewind.TowerBecause wind speeds increase withheight, the turbine is mounted on a tower. In general, the higher thetower, the more power the wind system can produce. The tower alsoraises the turbine above the air turbulence that can exist close to the ground because of obstructionssuch as hills, buildings, and trees. Ageneral rule of thumb is to install awind turbine on a tower with thebottom of the rotor blades at least30 feet (9 meters) above any obstaclethat is within 300 feet (90 meters) ofthe tower. Relatively small investments in increased tower height canyield very high rates of return in

power production. For instance, toraise a 10-kW generator from a 60-foottower height to a 100-foot towerinvolves a 10% increase in overall system cost, but it can produce 25%more power. There are two basic types of towers:self-supporting (free standing) andguyed. Most home wind power systems use a guyed tower. Guyed towers, which are the least expensive, canconsist of lattice sections, pipe, or tubing depending on the design, andsupporting guy wires. They are easierto install than self-supporting towers.However, because the guy radiusmust be one-half to three-quarters of the tower height, guyed towersrequire enough space to accommodatethem. While tilt-down towers aremore expensive they offer the consumer an easy way to perform 

02979311m

Tilt-Down Tower

Tilt-up towerin the normaloperating Tilt-up tower in the position

lowered position formaintenance or hurricanes

Tilt-down towersprovide easymaintenance forturbines.
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the batteries from overcharging.Deep-cycle batteries, such as thoseused for golf carts, can discharge andrecharge 80% of their capacity hundreds of times, which makes them agood option for remote renewableenergy systems. Automotive batteriesare shallow-cycle batteries and shouldnot be used in renewable energy systems because of their short life indeep-cycling operations. 

Can I Go "Off-Grid"?Hybrid SystemsHybrid wind energy systems can provide reliable off-grid power forhomes, farms or even entire communities (a co-housing project, for example) that are far from the nearestutility lines. According to manyrenewable energy experts, a "hybrid"system that combines wind and photovoltaic (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 different times of the day and year, hybridsystems are more likely to producepower when you need it. (For moreinformation on solar electric or PV systems, contact the EnergyEfficiency and Renewable EnergyClearinghouse—see For MoreInformation.)

For the times when neither the windnor the PV modules are producing,most hybrid systems provide powerthrough batteries and/or an enginegenerator powered by conventionalfuels such as diesel. If the batteriesrun low, the engine-generator can provide power and recharge the batteries. 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 be large enough to supply electricalneeds 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 available

or can only be made through an

Trudy Forsyth, NREL/PIX09122 and PIX09123
For safety, batteries should be isolated from living areas and electronics because they contain corrosiveand explosive substances. Lead-acidbatteries also require protection fromtemperature extremes. Grid-Connected SystemsIn grid-connected systems, the onlyadditional equipment required is apower conditioning unit (inverter)that makes the turbine output electrically compatible with the utility grid.Usually, batteries are not needed. What Do Wind SystemsCost?A small turbine can cost anywherefrom $3,000 to $35,000 installed,depending on size, application, andservice agreements with the manufacturer. (The American Wind EnergyAssociation [AWEA] says a typicalhome wind system costs approximately $32,000 (10 kW); a comparablephotovoltaic [PV] solar system wouldcost over $80,000.)A general rule of thumb for estimatingthe cost of a residential turbine is$1,000 to $3,000 per kilowatt. Windenergy becomes more cost effective as the size of the turbine’s rotorincreases. Although small turbinescost less in initial outlay, they are 

proportionally more expensive. Thecost of an installed residential windenergy system that comes with an 80-foot tower, batteries, and inverter,typically ranges from $13,000 to$40,000 for a 3 to 10 kW wind turbine.Although wind energy systemsinvolve a significant initial investment, they can be competitive withconventional energy sources whenyou account for a lifetime of reducedor avoided utility costs. The length ofthe payback period—the time beforethe savings resulting from your system equal the cost of the systemitself—depends on the system youchoose, the wind resource on yoursite, electricity costs in your area, andhow you use your wind system. Forexample, if you live in California andhave received the 50% buydown ofyour small wind system, have netmetering, and an average annualwind speed of 15 miles per hour(mph) (6.7 meters per second [m/s]),your simple payback would beapproximately 6 years.

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able to help you install your machine.Many people elect to install themachines themselves. Before attempting to install your wind turbine, askyourself the following questions:• Can I pour a proper cement

foundation?

• Do I have access to a lift or a way of

erecting the tower safely?

• Do I know the difference between

AC and DC wiring?

• Do I know enough about electricity

to safely wire my turbine?

• Do I know how to safely handle

and install batteries?

If you answered no to any of theabove questions, you should probablychoose to have your system installedby a system integrator or installer.Contact the manufacturer for help or call your state energy office andlocal utility for a list of local systeminstallers. You can also check the yellow pages for wind energy systemservice providers. A credible installerwill provide many services such aspermitting. Find out if the installer isa licensed electrician. Ask for references and check them out. You mayalso want to check with the BetterBusiness Bureau.

the line is "dead," might not take normal precautions and might be hurt oreven killed by the power from yourturbine. Another concern among utilities is that the power from your facility synchronize properly with theutility grid, and that it match the utility’s own power in terms of voltage,frequency, and power quality.A few years ago, some state governments started developing new standardized interconnection requirements for small renewable energygenerating facilities (including windturbines). In most cases the newrequirements have been based on consensus-based standards and testingprocedures developed by independent third-party authorities, such as theInstitute of Electrical and ElectronicEngineers and UnderwritersLaboratories.Interconnection RequirementsMost utilities and other electricityproviders require you to enter into aformal agreement with them beforeyou interconnect your wind turbinewith the utility grid. In states thathave retail competition for electricityservice (e.g., your utility operates the local wires, but you have a choice of electricity provider) you may have to sign a separate

y 

y 

own and have no control over. Othersconsider the insurance requirementsexcessive and unduly burdensome,making wind energy uneconomic. Inthe 21 years since utilities have beenrequired to allow small wind systemsto interconnect with the grid there has never been a liability claim, letalone a monetary award, relating toelectrical safety.

Warren Gretz, NREL/PIX09
If you do not have the expertise tomaintain the machine, your installermay provide a service and maintenance 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 formula illustrates factors that are important to the performance of a wind turbine.Notice that the wind speed, V, has an 

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

ρ = Air density, lb/ft3

A = Rotor swept area, ft2 or 

π

D2/4 (D is the rotor 

diameter in ft, 

π = 3.1416)

V =

Wind speed, mph

k = 0.000133 A constant to yield 

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

876543210

1 2 3 4 5 6 7

Rotor Diameter, m

Rotor Diameter, m

Relative Size of Small Wind Turbines

40302010

0

Swept area, m2 7 m6 m

5 m

4 m

3 m

2 m

1 m

02979303m

Source: Paul Gipe, Wind Energy Basics
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calculation.To get a preliminary estimate of theperformance of a particular wind turbine, use the formula below. 

AEO = 0.01328 D2 V3

Where:AEO = Annual energy output, 

kWh/year

D = Rotor diameter, feetV = Annual average wind speed, 

mph

The Wind Energy Payback PeriodWorkbook found at http://www.nrel.gov/wind/ under consumer information is a spreadsheet tool that can helpyou analyze the economics of a smallwind electric system and decidewhether wind energy will work foryou. The spreadsheet can be openedusing Microsoft Excel 95 software. It asks you to provide informationabout how you're going to finance thesystem, the characteristics of your site, and the properties of the systemyou're considering. It then providesyou with a simple payback estimationin years. If it takes too long to regainyour capital investment—the numberof years comes too close or is greaterthan the life of the system—windenergy will not be practical for you.

above 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-alone or grid-connected, you will also needto 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 resistance—thelonger the wire run, the more electricity 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 distribution system and are called gridconnected systems. A grid-connectedwind turbine can reduce your consumption of utility-supplied electricity for lighting, appliances, and electric heat. If the turbine cannotdeliver the amount of energy you

ence. When the wind system producesmore electricity than the householdrequires, the excess is sent or sold tothe utility. Grid-connected systems can be practical 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 for

connecting your system to its gridare not prohibitively expensive.

• There are good incentives for the

sale of excess electricity or for thepurchase of wind turbines.

Federal regulations (specifically, thePublic Utility Regulatory Policies Actof 1978, or PURPA) require utilities to connect with and purchase powerfrom small wind energy systems.However, you should contact yourutility before connecting to their distribution lines to address any powerquality and safety concerns. Your utility can provide you with a list ofrequirements for connecting your system to the grid. The American WindEnergy Association is another goodsource for information on utility 
p

p

like the one on pages 12 and 13 can

be used to estimate the wind resource

in your region. The highest averagewind speeds in the United States aregenerally found along seacoasts, onridgelines, and on the Great Plains;however, many areas have windresources strong enough to power asmall wind turbine economically. Thewind resource estimates on this mapgenerally apply to terrain features thatare well exposed to the wind, such asplains, hilltops, and ridge crests. Localterrain features may cause the windresource at a specific site to differ considerably from these estimates. Moredetailed wind resource information,including the 

Wind Energy Resource

Atlas of United States, published by theU.S. Department of Energy (DOE),can be found at the National WindTechnology Center web site athttp://www.nrel.gov/wind/ and theDOE Windpowering America web site at http://www.eren.doe.gov/windpoweringamerica/.Another way to indirectly quantifythe wind resource is to obtain averagewind speed information from a nearby airport. However, cautionshould be used because local terraininfluences and other factors maycause the wind speed recorded at an

Energy Resource Atlas of the UnitedStates (see For More Information).Another useful indirect measurementof the wind resource is the observation of an area’s vegetation. Trees,especially conifers or evergreens, canbe permanently deformed by strongwinds. This deformity, known as"flagging," has been used to estimatethe average wind speed for an area.For more information on the use of

Wind Speeds Increase with Height

02979308m 150

120

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0 0

Increase in wind power, %

Tower height, ft

41 75 100 124
Small Wind Electric Systems 13
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output of the system and also windspeed data if available.

How Do I Choose the BestSite for My Wind Turbine?You can have varied wind resourceswithin the same property. In additionto measuring or finding out about theannual wind speeds, you need toknow about the prevailing directionsof the wind at your site. If you live incomplex terrain, take care in selectingthe installation site. If you site yourwind turbine on the top of or on thewindy side of a hill, for example, youwill have more access to prevailingwinds than in a gully or on the leeward (sheltered) side of a hill on thesame property. In addition to geologicformations, you need to considerexisting obstacles such as trees, houses, and sheds, and you need toplan for future obstructions such asnew buildings or trees that have notreached their full height. Your turbineneeds to be sited upwind of buildings

p

p

like the one on pages 12 and 13 can

be used to estimate the wind resource

in your region. The highest averagewind speeds in the United States aregenerally found along seacoasts, onridgelines, and on the Great Plains;however, many areas have windresources strong enough to power asmall wind turbine economically. Thewind resource estimates on this mapgenerally apply to terrain features thatare well exposed to the wind, such asplains, hilltops, and ridge crests. Localterrain features may cause the windresource at a specific site to differ considerably from these estimates. Moredetailed wind resource information,including the 

Wind Energy Resource

Atlas of United States, published by theU.S. Department of Energy (DOE),can be found at the National WindTechnology Center web site athttp://www.nrel.gov/wind/ and theDOE Windpowering America web site at http://www.eren.doe.gov/windpoweringamerica/.Another way to indirectly quantifythe wind resource is to obtain averagewind speed information from a nearby airport. However, cautionshould be used because local terraininfluences and other factors maycause the wind speed recorded at an

Energy Resource Atlas of the UnitedStates (see For More Information).Another useful indirect measurementof the wind resource is the observation of an area’s vegetation. Trees,especially conifers or evergreens, canbe permanently deformed by strongwinds. This deformity, known as"flagging," has been used to estimatethe average wind speed for an area.For more information on the use of

02979310m

ggs-Putnam Index of Deformity

II III IV V VI VII

9-11 11-13 13-16 15-18 16-21 22+

4-5 5-6 6-7 7-8 8-9 10
above 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-alone or grid-connected, you will also needto 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 resistance—thelonger the wire run, the more electricity 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 distribution system and are called gridconnected systems. A grid-connectedwind turbine can reduce your consumption of utility-supplied electricity for lighting, appliances, and electric heat. If the turbine cannotdeliver the amount of energy you

ence. When the wind system producesmore electricity than the householdrequires, the excess is sent or sold tothe utility. Grid-connected systems can be practical 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 for

connecting your system to its gridare not prohibitively expensive.

• There are good incentives for the

sale of excess electricity or for thepurchase of wind turbines.

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

place your windturbine fromobstacles suchas buildings ortrees, the lessturbulence youwill encounter.
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Most of North America gets morewind in the winter than in the summer. For people using wind energy todisplace a large load in the summerlike air-conditioning or irrigationwater pumping, having an annualNEG credit allows them to produceNEG in the winter and be credited inthe summer.

Safety RequirementsWhether or not your wind turbine isconnected to the utility grid, theinstallation and operation of the windturbine is probably subject to the electrical codes that your local government (city or county) or in someinstances your state government hasin place. The government’s principalconcern is with the safety of the facility, so these code requirementsemphasize proper wiring and installation, and the use of components that have been certified for fire andelectrical safety by approved testinglaboratories, such as UnderwritersLaboratories. Most local electricalcodes requirements are based on theNational Electrical Code (NEC),which is published by the NationalFire Protection Association. As of1999, the latest version of the NEC didnot have any sections specific to theinstallation of wind energy facilities,

If you do not have the expertise tomaintain the machine, your installermay provide a service and maintenance 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 formula illustrates factors that are important to the performance of a wind turbine.Notice that the wind speed, V, has an 

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

ρ = Air density, lb/ft3

A = Rotor swept area, ft2 or 

π

D2/4 (D is the rotor 

diameter in ft, 

π = 3.1416)

V =

Wind speed, mph

k = 0.000133 A constant to yield 

power in kilowatts. (Multiplyingthe above kilowatt answer by 1.340 converts it to horsepower. [i.e., 1 kW = 1.340 horsepower]).
the line is "dead," might not take normal precautions and might be hurt oreven killed by the power from yourturbine. Another concern among utilities is that the power from your facility synchronize properly with theutility grid, and that it match the utility’s own power in terms of voltage,frequency, and power quality.A few years ago, some state governments started developing new standardized interconnection requirements for small renewable energygenerating facilities (including windturbines). In most cases the newrequirements have been based on consensus-based standards and testingprocedures developed by independent third-party authorities, such as theInstitute of Electrical and ElectronicEngineers and UnderwritersLaboratories.Interconnection RequirementsMost utilities and other electricityproviders require you to enter into aformal agreement with them beforeyou interconnect your wind turbinewith the utility grid. In states thathave retail competition for electricityservice (e.g., your utility operates the local wires, but you have a choice of electricity provider) you may have to sign a separate

y 

y 

own and have no control over. Othersconsider the insurance requirementsexcessive and unduly burdensome,making wind energy uneconomic. Inthe 21 years since utilities have beenrequired to allow small wind systemsto interconnect with the grid there has never been a liability claim, letalone a monetary award, relating toelectrical safety.

This gridconnected,10 kW Bergeywind turbineoffsets electricalpowerconsumption fora small businessin Norman,Oklahoma.

Bergey Windpower/PIX07166
you can ask

 regulatory

private

r to the 

in the case

).

ment

e one agrees

 loss or

 act or

ity. In 

wned

Customer ChargesCustomer charges can take a varietyof forms, including interconnectioncharges, metering charges, and standby charges, among others. Youshould not hesitate to question anycharges that seem inappropriate toyou. Federal law (Public UtilityRegulatory Policies Act of 1978, orPURPA, Section 210) prohibits utilitiesfrom assessing discriminatory chargesto customers who have their own generation facilities.

For safety, batteries should be isolated from living areas and electronics because they contain corrosiveand explosive substances. Lead-acidbatteries also require protection fromtemperature extremes. Grid-Connected SystemsIn grid-connected systems, the onlyadditional equipment required is apower conditioning unit (inverter)that makes the turbine output electrically compatible with the utility grid.Usually, batteries are not needed. What Do Wind SystemsCost?A small turbine can cost anywherefrom $3,000 to $35,000 installed,depending on size, application, andservice agreements with the manufacturer. (The American Wind EnergyAssociation [AWEA] says a typicalhome wind system costs approximately $32,000 (10 kW); a comparablephotovoltaic [PV] solar system wouldcost over $80,000.)A general rule of thumb for estimatingthe cost of a residential turbine is$1,000 to $3,000 per kilowatt. Windenergy becomes more cost effective as the size of the turbine’s rotorincreases. Although small turbinescost less in initial outlay, they are 

proportionally more expensive. Thecost of an installed residential windenergy system that comes with an 80-foot tower, batteries, and inverter,typically ranges from $13,000 to$40,000 for a 3 to 10 kW wind turbine.Although wind energy systemsinvolve a significant initial investment, they can be competitive withconventional energy sources whenyou account for a lifetime of reducedor avoided utility costs. The length ofthe payback period—the time beforethe savings resulting from your system equal the cost of the systemitself—depends on the system youchoose, the wind resource on yoursite, electricity costs in your area, andhow you use your wind system. Forexample, if you live in California andhave received the 50% buydown ofyour small wind system, have netmetering, and an average annualwind speed of 15 miles per hour(mph) (6.7 meters per second [m/s]),your simple payback would beapproximately 6 years.

Connecting to the Utility Grid—A Success StoryThis 10-kW Bergey wind turbine, installed on afarm located in Southwestern Kansas in 1983,produces an average 1700–1800 kilowatt-hoursper month, reducing the user's monthly utilitybills by approximately 50%. The turbine costabout $20,000 when it was installed. Since then,the cost for operation and maintenance has beenabout $50 per year. The only unscheduled maintenance activity over the years was repair to theturbine required as a result of damage caused bya lightning strike. Insurance covered all but $500of the $9000 cost of damages. The basic systemparts include:Bergey XL.10 wind turbine100-foot free-standing lattice towerInverter 

, 
Can I Go "Off-Grid"?Hybrid SystemsHybrid wind energy systems can provide reliable off-grid power forhomes, farms or even entire communities (a co-housing project, for example) that are far from the nearestutility lines. According to manyrenewable energy experts, a "hybrid"system that combines wind and photovoltaic (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 different times of the day and year, hybridsystems are more likely to producepower when you need it. (For moreinformation on solar electric or PV systems, contact the EnergyEfficiency and Renewable EnergyClearinghouse—see For MoreInformation.)

For the times when neither the windnor the PV modules are producing,most hybrid systems provide powerthrough batteries and/or an enginegenerator powered by conventionalfuels such as diesel. If the batteriesrun low, the engine-generator can provide power and recharge the batteries. 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 be large enough to supply electricalneeds 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 available

or can only be made through an

Battery bank

turbine

029
Most turbines manufactured todayare horizontal axis upwind machinesthat have two or three blades, whichare usually made of a composite material such as fiberglass. The amount of power a turbine willproduce is determined primarily bythe diameter of its rotor. The diameterof the rotor defines its "swept area," orthe quantity of wind intercepted bythe turbine. The turbine's frame is thestructure onto which the rotor, generator, and tail are attached. The tailkeeps the turbine facing into thewind.TowerBecause wind speeds increase withheight, the turbine is mounted on a tower. In general, the higher thetower, the more power the wind system can produce. The tower alsoraises the turbine above the air turbulence that can exist close to the ground because of obstructionssuch as hills, buildings, and trees. Ageneral rule of thumb is to install awind turbine on a tower with thebottom of the rotor blades at least30 feet (9 meters) above any obstaclethat is within 300 feet (90 meters) ofthe tower. Relatively small investments in increased tower height canyield very high rates of return in

power production. For instance, toraise a 10-kW generator from a 60-foottower height to a 100-foot towerinvolves a 10% increase in overall system cost, but it can produce 25%more power. There are two basic types of towers:self-supporting (free standing) andguyed. Most home wind power systems use a guyed tower. Guyed towers, which are the least expensive, canconsist of lattice sections, pipe, or tubing depending on the design, andsupporting guy wires. They are easierto install than self-supporting towers.However, because the guy radiusmust be one-half to three-quarters of the tower height, guyed towersrequire enough space to accommodatethem. While tilt-down towers aremore expensive they offer the consumer an easy way to perform 

y 

install a hybrid electric system poweredby wind, solar, and a generator for a costof about $19,700. The parts of the systeminclude:Bergey 1.5 kW wind turbine, 10-ft (3-m)diameter rotor, 70-ft. (21-m) tower Solarex PV panels, 480 watts24 DC battery bank, 375 ampere-hoursTrace sine wave inverter, 120 AC, 1 phase,4 kWOnan propane-fueled generator, 6.5 kWrated (3 kW derated for altitude) Electric appliances in the home includetelevision, stereo, two computers, toaster,blender, vacuum cleaner, and hair dryer.The largest electric loads are created by a well pump and washing machine. Thegenerator runs about 20% of the time,particularly when the washing machine is in use. Propane serves the other majorloads in the home: range, refrigerator, hotwater, and space heat. Solar collectors onthe roof provide pre-heating for the hotwater.

Jim Green, NREL/PIX02796
speed over a specified period of time.

Blades—The aerodynamic surface

that catches the wind.

Brake—Various systems used to stop

the rotor from turning.

Converter—See Inverter.Cut-in wind speed—The wind speed

at which a wind turbine begins togenerate electricity.

Cut-out wind speed—The wind speed

at which a wind turbine ceases to generate electricity.

Density—Mass per unit of volume.Downwind—On the opposite side

from the direction from which thewind is blowing.

Furling—A passive protection for the

turbine where typically the rotor foldseither up or around the tail vane.

Grid—The utility distribution system. 

The network that connects electricitygenerators to electricity users.

HAWT—Horizontal axis wind turbine.Inverter—A device that converts direct

current (DC) to alternating current(AC).

kW—Kilowatt, a measure of power

for electrical current (1000 watts).

Power curve—A chart showing a

wind turbine's power output across a range of wind speeds.

PUC—Public Utility Commission, a

state agency which regulates utilities.In some areas known as Public Service

Commission (PSC).

PURPA—Public Utility Regulatory

Policies Act (1978), 16 U.S.C. § 2601.18CFR §292 that refers to small generator utility connection rules.

Rated output capacity—The output

power of a wind machine operating at the rated wind speed.

Rated wind speed—The lowest wind

speed at which the rated outputpower of a wind turbine is produced.

Rotor—The rotating part of a wind

turbine, including either the bladesand blade assembly or the rotatingportion of a generator.

Rotor diameter—The diameter of the

circle swept by the rotor.

Rotor speed—The revolutions per

minute of the wind turbine rotor.

Start-up wind speed—The wind speed

at which a wind turbine rotor willbegin to spin. See also cut-in windspeed.
 turbine.

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Paul Gipe—A comprehensive guide to modern small wind technology.Available through AWEA. (202) 383-2500. http://www.awea.org andChelsea Green Publishing Company,White River Junction, Vermont. 1999.ISBN - 0-930031-64-4. http://www.chelseagreen.comWind Power Workshop by Hugh

Piggott—Provides an overview onhow to design a home-built wind turbine. Available from The Center forAlternative Technology, Machynlleth,Powys, SY20 9AZ, UK Phone: 06154-702400, FAX: 01654 702782. E-mail:help@catinfo.demon.co.uk,http://www.foe.co.uk/CATWind Resource Assessment Handbook:Fundamentals for Conducting aSuccessful Monitoring Program—Thishandbook presents industry-acceptedguidelines for planning and conducting a wind resource measurementprogram. These guidelines, which aredetailed and highly technical, emphasize the tasks of selecting, installing,and operating wind measurementequipment, as well as collecting andanalyzing the associated data.Prepared by AWS Scientific, Inc.Available electronically in NREL'spublication database at http://www.nrel.gov/publications.

p

• your property is in a remote

location that does not have easyaccess to utility lines 

• you are comfortable with long-term

investments.

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

Most zoning and aesthetic concernscan be addressed by supplying objective data. For example, the ambientnoise level of most modern residentialwind turbines is around 52 to 55 decibels. This means that while the soundof the wind turbine can be picked outof surrounding noise if a consciouseffort is made to hear it, a residentialsized wind turbine is no noisier thanyour average refrigerator.
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553-6847. http://www.ntis.gov/ordering.htmNon-Government OrganizationsAmerican Wind Energy Association,122 C Street, N.W. 4th Floor,

Washington, D.C. 20001. (202) 383-2500. http://www.awea.orgSolar Energy International—Shortcourses on renewable energy and sustainable development, inCarbondale, Colorado. (970) 963-8855.http://www.solarenergy.org

Periodicals"Apples and Oranges" by MickSagrillo—A comprehensive comparison of available small wind turbines.On Home Power Magazine Web site:http://www.homepower.comHome Power Magazine—The definitive bimonthly magazine for thehomemade power enthusiast.(800)707-6586 or on the Web at:http://www.homepower.comVideosAn Introduction to Residential WindSystems with Mick Sagrillo—A 63-minute video answering questionsmost often asked by homeowners as they consider purchasing andinstalling their own wind power 

now available in 30 states. Visit thisDOE Web site for information:http://www.eren.doe.gov/greenpower/netmeteringSmall Wind "Talk" on the Web—AWEA's Home Energy Systems electronic mailing list is designed as aforum for the discussion of small-scaleenergy systems that include wind. Tosubscribe, send a subscription requestawea-wind-home-subscribe@egroups.com.Wind Energy for Homeowners—This

Web 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
our nation's energy needs. Althoughwind turbines large enough to provide a significant portion of the electricity needed by the average U.S.home generally require one acre ofproperty 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 you

live 

• Tall towers are allowed in your

neighborhood or rural area 

• You have enough space• You can determine how much

electricity you need or want toproduce 

• It works for you economically. 

The purpose of this guide is to provide you with the basic information

about small wind electric systems tohelp you decide if wind energy willwork for you. Why Should I Choose Wind?Wind energy systems are one of themost cost-effective home-basedrenewable energy systems.

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

Bergey Windpower/PIX01476

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Arizona Incentives for Small Wind 

Sales Tax Exemption 

Wind energy equipment purchased from a retailer or

a contractor is exempt from state sales tax. 

Qualifying wind systems include wind electric

generators and wind-powered water pumps. The

sales tax exemption does not apply to equipment

like batteries and controls that is not part of the

system. A cap of $5,000 applies to the system cost

rather than each energy device. The exemption

ends December 31, 2010. 

www.azsolarcenter.com/benefits/solarsalestax.html 

Authority 1: ARS 42-5061: www.dsireusa.org/library/

docs/incentives/AZ08F.htm

Authority 2: HB 2322: www.dsireusa.org/library/

docs/incentives/AZ08Fa.htm

Personal Tax Credit 

Residential consumers may take a credit against

their personal income tax in the amount of 25% of

the cost of a wind energy device. The credit can be

claimed in the year of installation and has a

maximum allowable limit of $1,000. If the amount of

the credit exceeds a taxpayer’s liability in a certain

year, the unused portion of the credit may be carried

forward for up to five years. 

www.revenue.state.az.us/brochure/543.pdf 

Authority 1: ARS 43-1083: www.dsireusa.org/

library/docs/incentives/AZ01F.htm

Contact: 

Jim Arwood 

Arizona Department of Commerce 

Energy Office 

1700 W. Washington Street, Suite 220 

Phoenix, AZ 85007 

Phone: (602) 771-1144 

Fax: (602) 771-1203 

E-mail: jima@azcommerce.com 

www.commerce.state.az.us/Energy/default.asp 

Interconnection Standards 

Although Arizona's utilities have individually

developed distributed generation (DG) interconnection agreements, statewide interconnection

rules have not been established. In 1998–1999, the

Arizona Corporation Commission (ACC) convened 

a DG working group to establish recommendations

to the ACC on interconnection. Although the DG

working group report was released in June 2000, the

ACC has not adopted any interconnection rules. A

copy of the DG working group report may be viewed

at www.dsireusa.org/library/docs/additionaldocs/

AZFinalWorkingGroupRpt600.pdf.

The Salt River Project (SRP), which is not regulated

by the ACC on utility matters, developed its DG

interconnection rules and agreement based on the

ACC working group document. Its agreement

establishes separate requirements for units based

on the following size classes:

(a) Class I: 50 kW or less, single- or three-phase

(b) Class II: 51 kW to 300 kW, three-phase

(c) Class III: 301 kW to 5 MW, three-phase 

(d) Class IV: over 5 MW, three-phase

The SRP rules include technical protection

requirements, an interconnection process flow chart,

and a two-page interconnection application. A copy

of the SRP DG interconnection rules may be viewed

at www.dsireusa.org/library/docs/additionaldocs/

AZSRPInterconnectionGuidelines.pdf

Tucson Electric Power and Arizona Public Service,

the other two major electric utilities in Arizona, have

also established their own interconnection rules for

distributed generators, including wind. Commercial,

industrial, and residential customers are eligible.

These standards are not specific to net-metered

systems. 

Contact:

Jerry Smith 

Arizona Corporation Commission 

1200 W. Washington Street 

Phoenix, AZ 85007 

Phone: (602) 542-7271 

Fax: (602) 542-2129 

E-mail: jds@cc.state.az.us 

Web site: www.cc.state.az.us/ 

Dr. Tom Acker or Dr. Earl Duque

Sustainable Energy Solutions 

Northern Arizona University

P.O. Box 15600

Flagstaff, AZ 86011-5600

Phone: (928) 523-2380

Fax: (928) 523-2300

Web site: www.cba.nau.edu/ses/index.asp

Small Wind Electric Systems 
Other Contacts

Jim Arwood

Renewable Energy Coordinator

Arizona Department of Commerce Energy Office

1700 W. Washington, Suite 220

Phoenix, AZ 85007

Phone (602) 771-1144

Fax (480) 771-1202

E-mail: jima@azcommerce.com

Curtis Framel

U.S. Department of Energy

Seattle Regional Office

800 Fifth Avenue, Suite 3950

Seattle, WA 98104-3122

Phone: (206) 553-1004

Fax: (206) 553-2200

E-mail: Curtis.Framel@hq.doe.gov

Web site: www.eere.energy.gov/sro

Wind Powering America

www.windpoweringamerica.gov

A Strong Energy Portfolio for a Strong America

Energy efficiency and clean, renewable energy will mean a stronger economy, a cleaner environment, and greater energy

independence for America. Working with a wide array of state, community, industry, and university partners, the U.S.

Department of Energy’s Office of Energy Efficiency and Renewable Energy invests in a diverse portfolio of energy technologies. 

Produced for the U.S. Department of Energy by the 

National Renewable Energy Laboratory, 

a DOE national laboratory

DOE/GO-102004-1806 • May 2004

Printed with a renewable-source ink on paper containing at least 50% wastepaper, including 20% postconsumer waste.

For more information contact:

EERE Information Center

1-877-EERE-INF (1-877-337-3463)

www.eere.energy.gov