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Small Electric Systems A U.S. Consumer’s Guide Small Wind Electric Systems

Location—A home in Charlotte, Vermont Capacity—10 kilowatts manufacturer—Bergey Windpower Company Photo credit—Trudy Forsyth, NREL/PIX09123

Location — Wales Wind Project, Wales, Alaska Capacity — 0.1 MW Turbine manufacturer — Atlantic Orient Corporation Developer — Kotzebue Electric Association Photo credit — Steve Drouilhet, NREL/PIX09674

Capacity—10 kilowatts Turbine manufacturer—Bergey Windpower Company Photo credit—Bergey Windpower Company, NREL/PIX02102

Location—A ranch near Wheeler, Capacity—1 kilowatt Turbine manufacturer— Photo Credit—Elliott Bayly/PIX07169

Location — A farm in western Kansas Capacity — 10 kilowatts Turbine manufacturer — Bergey Windpower Company Photo credit — Warren Gretz, NREL/PIX09618

Location—A cabin in South Park, Colorado Capacity—600 watt Turbine manufacturer—Southwest WindPower Photo credit—E. McKenna, NREL/PIX04712 Small Wind Electric Systems  Small Wind Electric Systems A U.S. Consumer’s Guide

Introduction Can I use wind energy to power my home? This question is being asked across the country as more people look for affordable and reliable sourc- es of electricity. Small wind electric systems can make a significant contribution to our nation’s energy needs. Although wind large enough to provide a significant portion of the electricity needed by the average U.S. home gen- erally require one acre of property or more, approximately 21 million U.S. homes are built on one-acre and larger sites, and 24% of the U.S. population lives in rural areas. A small wind electric system will for you if: Bergey Windpower/PIX01476 • There is enough wind where you Homeowners, .ranchers, .and .small .businesses .can .use .wind- generated .electricity .to .reduce .their .utility .bills . .This .grid- live connected .system .installed .for .a .home .in .Norman, .Oklahoma, . • Tall towers are allowed in your reduces .the .homeowner’s .utility .bill .by .$100 .per .month . neighborhood or rural area • You have enough space Contents • You can determine how much Introduction ...... 1 electricity you need or want to First, .How .Can .I .Make .My .Home .More .Energy .Efficient? . . . 2 produce Is .Wind .Energy .Practical .for .Me? ...... 3 • It works for you economically. What .Size .Wind .Turbine .Do .I .Need? ...... 4 The purpose of this guide is to pro- What .are .the .Basic .Parts .of .a .Small .Wind .Electric .System? . . 5 vide you with the basic information What .Do .Wind .Systems .Cost? ...... 7 about small wind electric systems to Where .Can .I .Find .Installation .and .Maintenance .Support? . . . 8 help you decide if wind energy will How .Much .Energy .Will .My .System .Generate? ...... 9 work for you. Is .There .Enough .Wind .on .My .Site? ...... 11 Why Should I Choose Wind? How .Do .I .Choose .the .Best .Site .for .My .Wind .Turbine? . . . . 14 Wind energy systems are one Can .I .Connect .My .System .to .the .Utility .Grid? ...... 15 of the most cost-effective home- Can .I .Go .“Off-Grid”? ...... 19 based systems. Glossary .of .Terms ...... 21 Depending on your wind resource, a For .More .Information ...... 22  Small Wind Electric Systems

small wind energy system can lower Home Energy Use your electricity bill by 50% to 90%, Based on national averages help you avoid the high costs of extending utility power lines to Water remote locations, prevent power heating interruptions, and it is nonpolluting. 14% Heating and How Do Wind Turbines Work? Lighting, cooling Wind is created by the unequal heat- cooking, 44% and other ing of the Earth’s surface by the sun. appliances Wind turbines convert the kinetic 33% energy in wind into mechanical

power that runs a generator to 02979309m produce clean electricity. Today’s Refrigerator 9% turbines are versatile modular sources of electricity. Their blades are aero- The .largest .portion .of .a .utility .bill .for .a .typical . dynamically designed to capture the house .is .for .heating .and .cooling . maximum energy from the wind. The wind turns the blades, which spin a • Save money and increase shaft connected to a generator that comfort by properly maintaining makes electricity. and upgrading your heating, First, How Can I Make ventilation, and air-conditioning systems. My Home More Energy Efficient? • Install double-paned, gas-filled windows with low-emissivity Before choosing a wind system for (low-e) coatings to reduce heat your home, you should consider loss in cold climates and spectrally reducing your energy consumption by selective coatings to reduce heat making your home or business more gain in warm climates. energy efficient. Reducing your energy consumption will signifi- • Replace your lights in high-use cantly lower your utility bills and will areas with fluorescents. Replacing reduce the size of the home-based 25% of your lights can save about renewable energy system you need. 50% of your lighting energy bill. To achieve maximum energy effi- • When shopping for appliances, ciency, you should take a whole- look for the Energy Star® label. building approach. View your home Energy Star® appliances have as an energy system with interrelated been identified by the U.S. parts, all of which work synergisti- Environmental Protection Agency cally to contribute to the efficiency and U.S. Department of Energy of the system. From the insulation in as being the most energy-efficient your home’s walls to the light bulbs products in their classes. in its fixtures, there are many ways to • For more information on how to make your home more efficient. make your home energy efficient, • Reduce your heating and see Energy Savers in the For More cooling needs by up to 30% by Information section. investing just a few hundred dollars in proper insulation and weatherization products. Small Wind Electric Systems 

Is Wind Energy Practical structures permitted in residentially for Me? zoned areas, although variances are A small wind energy system can often obtainable. Most zoning ordi- provide you with a practical and nances have a height limit of 35 feet. economical source of electricity if: You can find out about the zoning restrictions in your area by calling • your property has a good wind the local building inspector, board of resource supervisors, or planning board. They • your home or business is located on can tell you if you will need to obtain at least one acre of land in a rural a building permit and provide you area with a list of requirements. • your local zoning codes or In addition to zoning issues, your covenants allow wind turbines neighbors might object to a wind that blocks their view, or • your average electricity bills are they might be concerned about noise. $150 per month or more Most zoning and aesthetic concerns • your property is in a remote can be addressed by supplying objec- location without easy access to tive data. For example, the ambient utility lines noise level of most modern residential • you are comfortable with long-term wind turbines is around 52 to 55 deci- investments. bels. This means that while the sound of the can be picked out Zoning Issues of surrounding noise if a conscious Before you invest in a wind energy effort is made to hear it, a residential- system, you should research poten- sized wind turbine is no noisier than tial obstacles. Some jurisdictions, for your average refrigerator. example, restrict the height of the

In .Clover .Valley, . Minnesota, .this . . 3-kW .Whisper . H175 .turbine .on .a . . 50-foot .tower .is . connected .to .the . utility .grid .to .offset . the .farm’s .utility- supplied .electricity . World Power /PIX07168  Small Wind Electric Systems

What Size Wind Turbine Turbines used in residential applica- Do I Need? tions can range in size from 400 watts The size of the wind turbine you need to 100 kW (100 kW for very large depends on your application. Small loads), depending on the amount of turbines range in size from 20 watts electricity you want to generate. For to 100 kilowatts (kW). The smaller or residential applications, you should “micro” (20- to 500-watt) turbines are establish an energy budget to help used in a variety of applications such define the turbine size you will need. as charging batteries for recreational Because energy efficiency is usually and sailboats. less expensive than energy produc- tion, making your house more energy One- to 10-kW turbines can be used in efficient first will probably be more applications such as pumping water. cost effective and will reduce the size Wind energy has been used for centu- of the wind turbine you need (see ries to water and grind grain. How Can I Make My Home More Although mechanical still Energy Efficient?). Wind turbine provide a sensible, low-cost option manufacturers can help you size for pumping water in low-wind areas, your system based on your electricity farmers and ranchers are finding that needs and the specifics of local wind wind-electric pumping is a little more patterns. versatile and they can pump twice the volume for the same initial A typical home uses approximately investment. In addition, mechanical 10,000 kilowatt-hours (kWh) of elec- windmills must be placed directly tricity per year (about 830 kWh per above the well, which may not take month). Depending on the average the best advantage of available wind wind speed in the area, a wind tur- resources. Wind-electric pumping bine rated in the range of 5 to 15 kW systems can be placed where the wind would be required to make a signifi- resource is the best and connected to cant contribution to this demand. A the pump motor with an electric cable. 1.5- kW wind turbine will meet the needs of a home requiring 300 kWh per month in a location with a 14- This .1-kW .Whisper . mile-per-hour (6.26-meters-per-sec- turbine .provides . ond) annual average wind speed. The direct .AC .power .for . the .water .pump .for . manufacturer can provide you with stock .tanks .on .a . the expected annual energy output ranch .in .Wheeler, . of the turbine as a function of annual Texas . average wind speed. The manufac- turer will also provide information on the maximum wind speed at which the turbine is designed to operate safely. Most turbines have automatic overspeed-governing systems to keep the from spinning out of control in very high . This information, along with your local wind speed and your energy budget, will help you decide which size turbine will best meet your electricity needs. Elliott Bayly/PIX09681 Small Wind Electric Systems 

What are the Basic Parts of a Small Wind Electric System? Rotor Home wind energy systems gener- ally comprise a rotor, a generator or Generator/ Tail alternator mounted on a frame, a tail alternator (usually), a tower, wiring, and the “balance of system” components: controllers, inverters, and/or batter- 02979312m ies. Through the spinning blades, the rotor captures the of Tower the wind and converts it into rotary motion to drive the generator. Wind Turbine Most turbines manufactured today are horizontal axis upwind generator from a 60-foot tower height with two or three blades, which are to a 100-foot tower involves a 10% usually made of a composite material increase in overall system cost, but it such as fiberglass. can produce 29% more power. The amount of power a turbine will There are two basic types of tow- produce is determined primarily by ers: self-supporting (free standing) the diameter of its rotor. The diameter and guyed. Most home of the rotor defines its “swept area,” systems use a guyed tower. Guyed or the quantity of wind intercepted by towers, which are the least expensive, the turbine. The turbine’s frame is the can consist of lattice sections, pipe, or structure onto which the rotor, genera- tubing (depending on the design), and tor, and tail are attached. The tail supporting guy wires. They are easier keeps the turbine facing into the wind. to install than self-supporting tow- ers. However, because the guy radius Tower must be one-half to three-quarters Because wind speeds increase with of the tower height, guyed towers height, the turbine is mounted on require enough space to accommodate a tower. In general, the higher the them. Although tilt-down towers are tower, the more power the wind more expensive, they offer the con- system can produce. The tower also sumer an easy way to perform Tilt-down .towers . raises the turbine above the air maintenance on smaller light-weight provide .easy . turbulence that can exist close to turbines, usually 5 kW or less. maintenance .for . the ground because of obstructions turbines . such as hills, buildings, and trees. A Tilt-Down Tower general rule of thumb is to install a Tilt-up tower wind turbine on a tower with the bot- in the normal tom of the rotor blades at least 30 feet operating Tilt-up tower in the position (9 meters) above any obstacle that lowered position for is within 300 feet (90 meters) of the maintenance or tower. Relatively small investments in hurricanes increased tower height can yield very high rates of return in power produc- tion. For instance, to raise a 10-kW 02979311m  Small Wind Electric Systems

Tilt-down towers can also be low- application, the balance of system ered to the ground during hazard- parts may include a controller, storage ous weather such as hurricanes. batteries, a power conditioning unit Aluminum towers are prone to (inverter), and wiring. Some wind cracking and should be avoided. turbine controllers, inverters, or other Most turbine manufacturers provide electrical devices may be stamped wind energy system packages that by a recognized testing agency, like include towers. Underwriters Laboratories. Mounting turbines on rooftops is not Stand-Alone Systems recommended. All wind turbines Stand-alone systems (systems not vibrate and transmit the vibration connected to the utility grid) require to the structure on which they are batteries to store excess power gener- mounted. This can lead to noise and ated for use when the wind is calm. structural problems with the building, They also need a charge controller to and the rooftop can cause excessive keep the batteries from overcharging. turbulence that can shorten the life of Deep-cycle batteries, such as those the turbine. used for golf carts, can discharge Balance of System and recharge 80% of their capacity The parts that you need in addition hundreds of times, which makes them to the turbine and the tower, or the a good option for remote renewable balance of system parts, will depend energy systems. Automotive batteries on your application. Most manufac- are shallow-cycle batteries and should turers can provide you with a system not be used in renewable energy package that includes all the parts you systems because of their short life need for your application. For exam- in deep-cycling operations. ple, the parts required for a water pumping system will be much differ- ent than what you need for a residen- tial application. The balance of system required will also depend on whether the system is grid-connected, stand- alone, or part of a hybrid system. For a residential grid-connected

A .Bergey .XL .10, . . 10-kW .wind . turbine .is .part .of . a .grid-connected . wind/photovoltaic . hybrid .system .that . reduces .the .utility . power .used .by .this . home .in .Vermont . . The .balance .of . system .(upper .right) . includes .from .left . . to .right, .a .Trace . inverter .for .the . PV .system, .a . breaker .box, .and .a . Powersync .inverter . for .the .wind .system . . Trudy Forsyth, NREL/PIX09122 and PIX09123 Small Wind Electric Systems 

Small wind turbines generate direct A .Southwest . current (DC) electricity. In very small Windpower .Air . 303, .300-watt . systems, DC appliances operate turbine .is .the .sole . directly off the batteries. If you want to source .of .electricity . use standard appliances that use con- for .this .remote . home .in .northern . ventional household alternating cur- Arizona . rent (AC), you must install an inverter to convert DC electricity from the batteries to AC. Although the inverter slightly lowers the overall efficiency of the system, it allows the home to be wired for AC, a definite plus with lenders, electrical code officials, and future homebuyers. For safety, batteries should be iso- lated from living areas and electron- ics because they contain corrosive and explosive substances. Lead-acid batteries also require protection from temperature extremes.

Grid-Connected Systems Southwest Windpower/PIX09156 In grid-connected systems, the only ranges from $15,000 to $50,000 for additional equipment required is a a 3- to 10-kW wind turbine. power conditioning unit (inverter) that makes the turbine output electri- Although wind energy systems cally compatible with the utility grid. involve a significant initial invest- Usually, batteries are not needed. ment, they can be competitive with conventional energy sources when What Do Wind Systems you account for a lifetime of reduced Cost? or avoided utility costs. The length Installation costs vary greatly depend- of the payback period—the time ing on local zoning, permitting, before the savings resulting from your and utility interconnection costs. system equal the cost of the system According to the American Wind itself—depends on the system you Energy Association, small wind choose, the wind resource on your energy systems cost from $3,000 to site, electricity costs in your area, and $5,000 for every kilowatt of generating how you use your wind system. For capacity. This is much cheaper than example, if you live in California and solar electric systems, but the payback have received the 50% buydown of period can still be lengthy. your small wind system, have , and an average annual Wind energy becomes more cost effec- wind speed of 15 miles per hour tive as the size of the turbine’s rotor (mph) (6.7 meters per second [m/ increases. Although small turbines s]), your simple payback would be cost less in initial outlay, they are approximately 6 years. proportionally more expensive. The cost of an installed residential wind energy system with an 80-foot tower, batteries, and inverter typically  Small Wind Electric Systems

references of past customers with installations similar to the one you are considering. Ask the system owners about performance, reliability, and maintenance and repair requirements, and whether the system is meeting their expectations. Also, find out how long the warranty lasts and what it includes. Where Can I Find Installation and Maintenance Support? The manufacturer/dealer should be able to help you install your machine. Many people elect to install the machines themselves. Before attempt- ing to install your wind turbine, ask yourself the following questions: • Can I pour a proper cement foundation? • Do I have access to a or a way of Warren Gretz, NREL/PIX09615 erecting the tower safely? Small .wind . turbines .like .this . Things to Consider When • Do I know the difference between 10-kW .Bergey . Purchasing a Wind Turbine XL .10 .provide . AC and DC wiring? electricity .for . Once you determine you can install • Do I know enough about electricity home, .farm, .and . a wind energy system in compliance to safely wire my turbine? ranch .applications . with local land use requirements, you can begin pricing systems and compo- • Do I know how to safely handle nents. Comparatively shop for a wind and install batteries? system as you would any major pur- If you answered no to any of the chase. Obtain and review the product above questions, you should probably literature from several manufacturers. choose to have your system installed As mentioned earlier, lists of manu- by a system integrator or installer. facturers are available from AWEA, Contact the manufacturer for help (see For More Information), but not or call your state energy office and all small turbine manufacturers are local utility for a list of local system members of AWEA. Check the yellow installers. You can also check the yel- pages for wind energy system dealers low pages for wind energy system in your area. service providers. A credible installer Once you have narrowed the field, will provide many services such as research a few companies to be sure permitting. Find out if the installer is a they are recognized wind energy licensed electrician. Ask for references businesses and that parts and service and check them out. You may also will be available when you need them. want to check with the Better Business You may wish to contact the Better Bureau. Business Bureau to check on Although small wind turbines are the company’s integrity and ask for very sturdy machines, they do require Small Wind Electric Systems  some annual maintenance. Bolts wind speed results in a large increase and electrical connections should be in power. That is why a taller tower checked and tightened if necessary. will increase the productivity of any The machines should be checked for wind turbine by giving it access to corrosion and the guy wires for higher wind speeds as shown in the proper tension. In addition, you Wind Speeds Increase with Height should check for and replace any graph. The formula for calculating worn leading edge tape on the blades, the power from a wind turbine is: if appropriate. After 10 years, the Power = k C 1/2 ρ A V3 blades or bearings may need to be p replaced, but with proper installation Where: and maintenance, the machine should P = Power output, kilowatts last up to 20 years or longer. Cp = Maximum power coefficient, If you do not have the expertise to ranging from 0.25 to 0.45, maintain the machine, your installer dimension less (theoretical maximum = 0.59) may provide a service and mainte- nance program. ρ = Air density, lb/ft3 A = Rotor swept area, ft2 or How Much Energy Will My π D2/4 (D is the rotor System Generate? diameter in ft, π = 3.1416) Most U.S. manufacturers rate their V = Wind speed, mph turbines by the amount of power they k = 0.000133 A constant to yield can safely produce at a particular power in kilowatts. (Multiplying wind speed, usually chosen between the above kilowatt answer by 24 mph (10.5 m/s) and 36 mph (16 m/ 1.340 converts it to horse- s). The following formula power [i.e., 1 kW = 1.340 illustrates factors that are important ]). to the performance of a wind turbine. The rotor swept area, A, is important Notice that the wind speed, V, has an because the rotor is the part of the exponent of 3 applied to it. This turbine that captures the wind energy. means that even a small increase in

Relative Size of Small Wind Turbines 40 8

2 30 7 7 m 20 6 6 m

5 m Swept area, 10 5 m

4 0 4 m 1 2 3 4 5 6 7 Rotor Diameter, m 3

Rotor Diameter, m Rotor Diameter, 3 m

2 2 m

1 1 m

0 02979303m Source: Paul Gipe, Wind Energy Basics 10 Small Wind Electric Systems

Air Density Change with Elevation height of the tower that you plan to 10,000 use, and the frequency distribution of 9,000 the wind–an estimate of the number 8,000 of hours that the wind will blow at 7,000 each speed during an average year. 6,000 They should also adjust this calcula- 5,000 tion for the elevation of your site. 4,000 Contact a wind turbine manufacturer Elevation, ft Elevation, 3,000 or dealer for assistance with this 2,000 calculation. 1,000 To get a preliminary estimate of the

0 02979302m 70 75 80 85 90 95 100 performance of a particular wind tur- Density change compared to level, % bine, use the formula below. AEO = 0.01328 D2 V3 So, the larger the rotor, the more Where: energy it can capture. The air density, AEO = Annual energy output, ρ, changes slightly with air tempera- kWh/year ture and with elevation. The ratings D = Rotor diameter, feet for wind turbines are based on standard conditions of 59° F (15° C) V = Annual average wind speed, at sea level. A density correction mph should be made for higher elevations The Wind Energy Payback Period as shown in the Air Density Change Workbook found at www.nrel.gov/ with Elevation graph. A correction for wind/docs/spread_sheet_Final.xls is temperature is typically not needed a spreadsheet tool that can help you for predicting the long-term perfor- analyze the economics of a small wind electric system and decide whether mance of a wind turbine. wind energy will work for you. The Although the calculation of wind spreadsheet can be opened using power illustrates important features Microsoft Excel 95 software. It asks about wind turbines, the best mea- you to provide information about how sure of wind turbine performance is you’re going to finance the system, annual energy output. The difference the characteristics of your site, and the properties of the system you’re between power and energy is that considering. It then provides you with power (kilowatts [kW]) is the rate at a simple payback estimation in years. which electricity is consumed, while If it takes too long to regain your capi- energy (kilowatt-hours [kWh]) is the tal investment—the number of years quantity consumed. An estimate of comes too close or is greater than the the annual energy output from your life of the system—wind energy will wind turbine, kWh/year, is the best not be practical for you. way to determine whether a particular wind turbine and tower will produce enough electricity to meet your needs. A wind turbine manufacturer can help you estimate the energy production you can expect. They will use a cal- culation based on the particular wind turbine power curve, the average annual wind speed at your site, the Small Wind Electric Systems 11

Is There Enough Wind particular location. Airport wind data on My Site? are generally measured at heights Does the wind blow hard and con- about 20–33 ft (6–10 m) above ground. sistently enough at my site to make a Average wind speeds increase with system economi- height and may be 15%–25% greater cally worthwhile? That is a key ques- at a typical wind turbine hub-height tion and not always easily answered. of 80 ft (24 m) than those measured The wind resource can vary signifi- at airport anemometer heights. The cantly over an area of just a few miles National Climatic Data Center collects because of local terrain influences data from airports in the United States on the wind flow. Yet, there are steps and makes wind data summaries you can take that will go a long way available for purchase. Summaries towards answering the above of wind data from almost 1000 U.S. question. airports are also included in the Wind Energy Resource Atlas of the United As a first step, wind resource maps States (see For More Information). like the one on pages 12 and 13 can be used to estimate the wind resource Another useful indirect measurement in your region. The highest average of the wind resource is the observa- wind speeds in the United States are tion of an area’s vegetation. Trees, generally found along seacoasts, on especially conifers or evergreens, can ridgelines, and on the Great Plains; be permanently deformed by strong however, many areas have wind winds. This deformity, known as resources strong enough to power a “flagging,” has been used to estimate small wind turbine economically. The the average wind speed for an area. wind resource estimates on this map For more information on the use of generally apply to terrain features that flagging, you may want to obtain are well exposed to the wind, such as plains, hilltops, and ridge crests. Local Wind Speeds Increase with Height terrain features may cause the wind resource at a specific site to differ con- 150

siderably from these estimates. More 02979308m detailed wind resource information, including the Wind Energy Resource 120 Atlas of United States, published by the U.S. Department of Energy (DOE), can be found at the Technology Center Web site at www. 90 nrel.gov/wind/ and the DOE Wind Powering America Web site at www. windpoweringamerica.gov. height, ft Tower 60 Another way to indirectly quantify the wind resource is to obtain average wind speed information from a 30 nearby airport. However, caution should be used because local terrain influences and other factors may cause the wind speed recorded at 0 0 41 75 100 124 an airport to be different from your Increase in wind power, % 12 Small Wind Electric Systems Small Wind Electric Systems 13 14 Small Wind Electric Systems

Flagging, .the .effect . of .strong .winds .on . Flagging 0 I area .vegetation, . Prevailing wind No Brushing can .help .determine . deformity and slight area .wind .speeds . . flagging

II III IV Slight Moderate Complete flagging flagging flagging

V VI VII Partial Complete Carpeting throwing throwing

02979310m

Griggs-Putnam Index of Deformity Index I II III IV V VI VII Wind mph 7-9 9-11 11-13 13-16 15-18 16-21 22+ Speed m/s 3-4 4-5 5-6 6-7 7-8 8-9 10

A Siting Handbook for Small Wind How Do I Choose the Best Energy Conversion Systems (see For Site for My Wind Turbine? More Information). You can have varied wind resources Direct monitoring by a wind resource within the same property. In addition measurement system at a site pro- to measuring or finding out about vides the clearest picture of the avail- the annual wind speeds, you need to able resource. A good overall guide know about the prevailing directions on this subject is the Wind Resource of the wind at your site. If you live in Assessment Handbook (see For More complex terrain, take care in selecting Information). Wind measurement the installation site. If you site your systems are available for costs as low wind turbine on the top of or on the as $600 to $1200. This expense may or windy side of a hill, for example, you may not be hard to justify depending will have more access to prevailing on the exact nature of the proposed winds than in a gully or on the lee- small wind turbine system. The mea- ward (sheltered) side of a hill on the surement equipment must be set high same property. In addition to geologic enough to avoid turbulence created formations, you need to consider by trees, buildings, and other obstruc- existing obstacles such as trees, tions. The most useful readings are houses, and sheds, and you need to those taken at hub-height, the eleva- plan for future obstructions such as tion at the top of the tower where the new buildings or trees that have not wind turbine is going to be installed. reached their full height. Your turbine If there is a small wind turbine sys- needs to be sited upwind of build- tem in your area, you may be able to ings and trees, and it needs to be 30 obtain information on the annual feet above anything within 300 feet. output of the system and also wind You also need enough room to raise speed data if available. and lower the tower for maintenance, Small Wind Electric Systems 15

Obstruction of the Wind by a Building or Tree of Height (H)

Region of highly 2 H turbulent H flow 02979307m

2 H 20 H The .farther .you . place .your .wind . and if your tower is guyed, you must requires, the excess is sent or sold to turbine .from . allow room for the guy wires. the utility. obstacles .such . as .buildings .or . Whether the system is stand-alone Grid-connected systems can be practi- trees, .the .less . or grid-connected, you will also need cal if the following conditions exist: turbulence .you . will .encounter . to take the length of the wire run • You live in an area with average between the turbine and the load annual wind speed of at least (house, batteries, water , etc.) 10 mph (4.5 m/s) into consideration. A substantial amount of electricity can be lost as a • Utility-supplied electricity is result of the wire resistance—the lon- expensive in your area (about 10 to ger the wire run, the more electric- 15 cents per kilowatt-hour) ity is lost. Using more or larger wire • The utility’s requirements for will also increase your installation connecting your system to its grid cost. Your wire run losses are greater are not prohibitively expensive when you have (DC) • There are good incentives for the instead of alternating current (AC). sale of excess electricity or for the So, if you have a long wire run, it is purchase of wind turbines. advisable to invert DC to AC. Federal regulations (specifically, the Can I Connect My System Public Utility Regulatory Policies Act to the Utility Grid? of 1978, or PURPA) require utilities Small wind energy systems can be to connect with and purchase power connected to the electricity distribu- from small wind energy systems. tion system and are called grid- However, you should contact your connected systems. A grid-connected utility before connecting to their dis- wind turbine can reduce your con- tribution lines to address any power sumption of utility-supplied electric- quality and safety concerns. Your ity for lighting, appliances, and utility can provide you with a list of electric heat. If the turbine cannot requirements for connecting your sys- deliver the amount of energy you tem to the grid. The American Wind need, the utility makes up the differ- Energy Association is another good ence. When the wind system produces source for information on utility more electricity than the household interconnection requirements. The 16 Small Wind Electric Systems

A .grid-connected . Grid-connected Systems wind .turbine . can .reduce .your . consumption .of . Meter utility-supplied . electricity . AC

Inverter Load Wind turbine 02979301m

following information about utility Most of North America gets more grid connection requirements was wind in the winter than in the sum- taken from AWEA’s Web site. For mer. For people using wind energy to more detailed information, visit www. displace a large load in the summer awea.org/ or contact AWEA (see For like air-conditioning or irrigation More Information). water pumping, having an annual NEG credit allows them to produce Net Metering NEG in the winter and be credited in The concept of net metering programs the summer. is to allow the electric meters of cus- tomers with generating facilities to Safety Requirements turn backwards when their generators Whether or not your wind turbine are producing more energy than the is connected to the utility grid, the customers’ demand. Net metering installation and operation of the wind allows customers to use their genera- turbine is probably subject to the tion to offset their consumption over electrical codes that your local gov- the entire billing period, not just ernment (city or county), or in some instantaneously. This offset would instances your state government, has enable customers with generating in place. The government’s principal facilities to receive prices for concern is with the safety of the more of the electricity they generate. facility, so these code requirements Net metering varies by state and emphasize proper wiring and installa- by utility company, depending on tion and the use of components whether net metering was legis- that have been certified for fire and lated or directed by the Public Utility electrical safety by approved testing Commission. Net metering programs laboratories, such as Underwriters all specify a way to handle the net Laboratories. Most local electrical excess generation (NEG) in terms of codes requirements are based on payment for electricity and/or length the National Electrical Code (NEC), of time allowed for NEG credit. If which is published by the National the net metering requirements define Fire Protection Association. As of NEG on a monthly basis, the consum- 1999, the latest version of the NEC did er can only get credit for their excess not have any sections specific to the that month. But if the net metering installation of wind energy facilities’ rules allow for annual NEG, the NEG consequently wind energy installa- credit can be carried for up to a year. tions are governed by the generic provisions of the NEC. Small Wind Electric Systems 17

If your wind turbine is connected to provider. In the case of private (inves- the local utility grid so that any of the tor-owned) utilities, the terms and power produced by your wind tur- conditions in these agreements must bine is delivered to the grid, then your be reviewed and approved by state utility also has legitimate concerns regulatory authorities. about safety and power quality that need to be addressed. The utility’s principal concern is that your wind Some utilities require small wind turbine automatically stops deliver- turbine owners to maintain liability ing any electricity to its power lines insurance in amounts of $1 million or during a power outage. Otherwise more. Utilities consider these require- line workers and the public, thinking ments necessary to protect them from that the line is “dead,” might not take liability for facilities they do not own normal precautions and might be and have no control over. Others hurt or even killed by the power from consider the insurance requirements your turbine. Another concern among excessive and unduly burdensome, utilities is whether the power from making wind energy uneconomic. In your facility synchronizes properly the 21 years since utilities have been with the utility grid and it matches the required to allow small wind systems to interconnect with the grid, there utility’s own power in terms of volt- This .grid- age, frequency, and power quality. has never been a liability claim, let connected, . . alone a monetary award, relating to 10-kW .Bergey . A few years ago, some state govern- electrical safety. wind .turbine . ments started developing new offsets . standardized interconnection require- In seven states (California, Georgia, electrical .power . Maryland, Nevada, Oklahoma, consumption .for . ments for small renewable energy a .small .business . generating facilities (including wind Oregon, and Washington), laws in .Norman, . turbines). In most cases, the new or regulatory authorities prohibit Oklahoma . requirements are based on consen- sus-based standards and testing pro- cedures developed by independent third-party authorities, such as the Institute of Electrical and Electronic Engineers and Underwriters Laboratories. Interconnection Requirements Most utilities and other electricity providers require you to enter into a formal agreement with them before you interconnect your wind turbine with the utility grid. In states that have retail competition for electricity service (e.g., your utility operates the local wires, but you have a choice of electricity provider) you may have to sign a separate agreement with each company. Usually these agreements are writ- ten by the utility or the electricity Bergey Windpower/PIX07166 18 Small Wind Electric Systems

utilities from imposing any insurance facility. Although the basic principle requirements on small wind sys- is sound—utilities should not be tems that qualify for “net metering.” held responsible for property - In at least two other states (Idaho, age or personal injury attributable Virginia), regulatory authorities have to someone else—indemnity provi- allowed utilities to impose insurance sions should not favor the utility but requirements but have reduced the should be fair to both parties. Look for required coverage amounts to levels language that says, “each party shall consistent with conventional residen- indemnify the other . . .” rather than tial or commercial insurance policies “the customer shall indemnify the (e.g., $100,000 to $300,000). If your utility . . .” insurance amounts seem excessive, Customer Charges you can ask for a reconsideration from regulatory authorities (in the case of Customer charges can take a variety private investor-owned utilities) or of forms, including interconnection the utility’s governing board (in the charges, metering charges, and case of publicly owned utilities). standby charges. You should not hesitate to question any charges that Indemnification seem inappropriate to you. Federal An indemnity is an agreement law (Public Utility Regulatory Policies between two parties in which one Act of 1978, or PURPA, Section 210) agrees to secure the other against loss prohibits utilities from assessing dis- or damage arising from some act or criminatory charges to customers who some assumed responsibility. In the have their own generation facilities. context of customer-owned generat- ing facilities, utilities often want customers to indemnify them for any potential liability arising from the operation of the customer’s generating

Connecting to the Utility Grid: A Success Story This 10-kW Bergey wind turbine, installed on a farm in Southwestern Kansas in 1983, pro- duces an average 1700–1800 kilowatt-hours per month, reducing the user’s monthly utility bills by approximately 50%. The turbine cost about $20,000 when it was installed. Since then, the cost for operation and maintenance has been about $50 per year. The only unscheduled main- tenance activity over the years was repair to the turbine required as a result of a lightning strike. Insurance covered all but $500 of the $9000 cost of damages. The basic system parts include: Bergey XL.10 wind turbine 100-foot free-standing lattice tower Inverter Warren Gretz, NREL/PIX09634 Small Wind Electric Systems 19

Hybrid Power Systems A .hybrid .system . Combine multiple sources to deliver non-intermittent that .combines .a . wind .system .with .a . solar .and/or .diesel . generator .can . provide .reliable .off- grid .power .around . the .clock . . PV modules

Generator

AC or Load Regulation and DC conversion Wind turbine 02979301m

Battery bank

Can I Go “Off-Grid”? For the times when neither the wind Hybrid Systems turbine nor the PV modules are pro- ducing, most hybrid systems provide Hybrid wind energy systems can power through batteries and/or an provide reliable off-grid power for -generator powered by conven- homes, farms, or even entire com- tional fuels such as diesel. If the bat- munities (a co-housing project, for teries run low, the engine-generator example) that are far from the near- can provide power and recharge est utility lines. According to many the batteries. Adding an engine- renewable energy experts, a “hybrid” generator makes the system more system that combines wind and complex, but modern electronic photovoltaic (PV) offers controllers can operate these systems several advantages over either single automatically. An engine-generator system. In much of the United States, can also reduce the size of the other wind speeds are low in the summer components needed for the system. when the sun shines brightest and Keep in mind that the storage capac- longest. The wind is strong in the ity must be large enough to supply winter when less sunlight is available. electrical needs during non-charging Because the peak operating times periods. Battery banks are typically for wind and PV occur at different sized to supply the electric load for times of the day and year, hybrid one to three days. systems are more likely to produce power when you need it. (For more An off-grid hybrid system may be information on solar electric or PV practical for you if: systems, contact the Energy Efficiency • You live in an area with average and Renewable Energy Information annual wind speed of at least Portal—see For More Information.) 9 mph (4.0 m/s) • A grid connection is not available or can only be made through an 20 Small Wind Electric Systems

expensive extension. The cost of • You would like to gain energy running a power line to a remote independence from the utility site to connect with the utility grid • You would like to generate clean can be prohibitive, ranging from power. $15,000 to more than $50,000 per mile, depending on terrain.

Living Off-Grid: A Success Story This home, built near Ward, Colorado (at an elevation of 9000 feet), has been off-grid since it was built in 1972. When the house was built, the nearest util- ity was over a mile away, and it would have cost between $60K–$70K (based on 1985 rates) to connect to the utility lines. The owners decided to install a hybrid electric system powered by wind, solar, and a generator for a cost of about $19,700. The parts of the system include: Bergey 1.5-kW wind turbine, 10-ft (3-m) diameter rotor, 70-ft. (21-m) tower Solarex PV panels, 480 watts 24 DC battery bank, 375 ampere-hours Trace sine wave inverter, 120 AC, 1 phase, 4 kW Onan propane-fueled generator, 6.5 kW rated (3 kW derated for altitude) Electric appliances in the home include television, stereo, two computers, toaster, blender, vacuum cleaner, and hair dryer. The largest electric loads are created by a well pump and washing machine. The generator runs about 20% of the time, par- ticularly when the washing machine is in use. Propane serves the other major loads in the home: range, refrigerator, hot water, and space heat. Solar collectors on the roof provide pre-heating for the hot water. Jim Green, NREL/PIX02796 Small Wind Electric Systems 21

Glossary of Terms kWh—Kilowatt-hour, a measure —The shape of the blade cross- of energy equal to the use of one section, which for most modern hori- kilowatt in one hour. zontal axis wind turbines is designed MW—Megawatt, a measure of power to enhance the lift and improve tur- (1,000,000 watts). bine performance. —The body of a -type Ampere-hour—A unit for the quantity wind turbine, containing the gearbox, of electricity obtained by integrating generator, blade hub, and other parts. current flow in amperes over the time O&M .costs—Operation and mainte- in hours for its flow; used as a mea- nance costs. sure of battery capacity. Power .coefficient—The ratio of the Anemometer—A device to measure power extracted by a wind turbine the wind speed. to the power available in the wind Average .wind .speed—The mean wind stream. speed over a specified period of time. Power .curve—A chart showing a Blades—The aerodynamic surface that wind turbine’s power output across catches the wind. a range of wind speeds. Brake—Various systems used to stop PUC—Public Utility Commission, a the rotor from turning. state agency which regulates utilities. Converter—See Inverter. In some areas known as Public Service Commission (PSC). Cut-in .wind .speed—The wind speed at which a wind turbine begins to PURPA—Public Utility Regulatory generate electricity. Policies Act (1978), 16 U.S.C. § 2601.18 CFR §292 that refers to small Cut-out .wind .speed —The wind speed generator utility connection rules. at which a wind turbine ceases to generate electricity. Rated .output .capacity—The output power of a wind machine operating Density —Mass per unit of volume. at the rated wind speed. Downwind —On the opposite side Rated .wind .speed—The lowest wind from the direction from which the speed at which the rated output wind blows. power of a wind turbine is produced. Furling —A passive protection for the Rotor—The rotating part of a wind turbine in which the rotor folds either turbine, including either the blades up or around the tail vane. and blade assembly or the rotating Grid—The utility distribution system. portion of a generator. The network that connects electricity Rotor .diameter—The diameter of the generators to electricity users. circle swept by the rotor. HAWT —Horizontal axis wind turbine. Rotor .speed—The revolutions per Inverter—A device that converts direct minute of the wind turbine rotor. current (DC) to alternating current Start-up .wind .speed—The wind speed (AC). at which a wind turbine rotor will kW—Kilowatt, a measure of power for begin to spin. See also Cut-in wind electrical current (1000 watts). speed. 22 Small Wind Electric Systems

Swept .area—The area swept by the Wind Energy Basics turbine rotor, A = π R2, where R is the Paul Gipe radius of the rotor. ISBN 1-890132-07-01 Tip .speed .ratio—The speed at the tip A comprehensive guide to modern of the rotor blade as it moves through small wind technology. the air divided by the wind velocity. American Wind Energy Association This is typically a design requirement (202) 383-2500 for the turbine. www.awea.org or Turbulence—The changes in wind Chelsea Green Publishing Company speed and direction, frequently www.chelseagreen.com caused by obstacles. Wind Energy Resource Atlas of the Upwind—On the same side as the United States direction from which the wind is D. Elliott et al. blowing—windward. American Wind Energy Association VAWT—Vertical axis wind turbine. (202) 383-2500 www.awea.org Wind .farm—A group of wind tur- rredc.nrel.gov/wind/pubs/atlas bines, often owned and maintained by one company. Also known as a wind Wind Power for Home, Farm, and power plant. Business: Renewable Energy for the New Millenium Yaw—The movement of the tower top Paul Gipe turbine that allows the turbine to stay ISBN-1-931498-14-8 into the wind. Completely revised and expanded For More Information edition of Wind Power for Home and Business Books Chelsea Green Publishing Company A Siting Handbook for Small Wind www.chelseagreen.com Energy Conversion Systems Wind Power Workshop H. Wegley, J. Ramsdell, M. Orgill and Hugh Piggott R. Drake Provides an overview on how to Report No. PNL-2521 Rev.1, 1980 design a home-built wind turbine. National Technical Information The Center for Alternative Service Technology 5285 Port Royal Rd. Machynlleth, Powys Springfield, VA 22151 SY20 9AZ, UK (800) 553-6847 Phone: 06154-702400 www.ntis.gov E-mail: [email protected] Energy Savers Tips on Saving Energy www.foe.co.uk/CAT and Money at Home — A consumer’s guide for saving energy and reducing utility bills. www.eere.energy.gov/ consumerinfo/energy_savers Small Wind Electric Systems 23

Government Agencies Videos U.S. Department of Energy’s Energy An Introduction to Residential Wind Efficiency and with Mick Sagrillo Information Portal A 63-minute video answering ques- www.eere.energy.gov tions most often asked by homeown- ers as they consider purchasing and National Climatic Data Center installing wind power systems Federal Building, 151 Patton Avenue American Wind Energy Association Asheville, North Carolina, 28801-5001 Phone: (202) 383-2500 Phone: (828) 271-4800 www.awea.org www.ncdc.noaa.gov U.S. Department of Commerce Web Sites National Technical Information Small Wind Systems Service Includes answers to frequently asked 5285 Port Royal Road questions and information on U.S. Springfield, Virginia 22161 manufacturers. (800) 553-6847 www.awea.org/smallwind.html www.ntis.gov Database of State Incentives for Non-Government Organizations Renewable Energy www.dsireusa.org American Wind Energy Association 1101 14th St., NW Green Power Network Net Metering 12th Floor Net metering programs are now avail- Washington, D.C. 20005 able in more than 35 states. Phone: (202) 383-2500 www.eere.energy.gov/greenpower/ www.awea.org markets International Small Wind “Talk” on the Web Short courses on renewable energy AWEA’s Home Energy Systems elec- and sustainable development tronic mailing list is a forum for the Phone: (970) 963-8855 discussion of small-scale energy sys- www.solarenergy.org tems that include wind. To subscribe, send a subscription request to awea- Periodicals [email protected]. Apples and Oranges Wind Energy for Homeowners Mick Sagrillo This Web page covers items you A comprehensive comparison of should consider before investing available small wind turbines avail- in a small wind energy system and able on the Home Power Magazine provides basic information about the Web site: �����������������www.homepower.com systems. Home Power Magazine www.nrel.gov/clean_energy/home_ The definitive bimonthly magazine wind.html for the homemade power enthusiast. Phone: (800)707-6586 Handbook www.homepower.com www.nrel.gov/docs/legosti/ fy97/22223.pdf 24 Small Wind Electric Systems

2002 Farm Bill — Wind The amount of the payments depends on the size of the wind installation, the pro- duction of electricity by that system, and Provisions the length of the contract period. Mainstay Renewable Energy Systems and offers 3-, 5-, and 10-year purchase con- tracts. The longer contract periods provide Energy Efficiency Improvements greater incentive payments on a $/kWh Incentive Type: Low-interest loans, loan basis. Typical payments for wind, which guarantees, and grants are made quarterly, range from 0.2¢/kWh Eligible Technologies: Renewable energy to 1.5¢/kWh. systems (energy derived from wind, solar, , geothermal, and hydro- There is a $100 certification fee to get gen derived from biomass or water started with Mainstay Rewards. However, using a renewable energy source) and the fee may be paid with future green tag energy efficiency improvements. sales, and is generally waived for partici- Applicable Sectors: Agriculture, rural pants who opt for 10-year contracts. small commercial The requirements are: Amount: Varies. The grant may not exceed 1. The system must be grid-connected; 25% of the cost of a project, and a com- 2. Net-metering by the utility does not bined grant and loan or guarantee may restrict the system owner from selling not exceed 50% of the cost of a project. the green tags; Terms: 2003 – 2007 3. The system owner must have title to the Date Enacted: 2002 green tags or renewable energy credits. Authority: Farm Bill, Title IX, Section 9006 They cannot have been sold Summary: This law allows direct financial or transferred to any other entity; assistance to farmers, ranchers, and rural 4. The system must be a new renewable, small businesses for the purchase of wind which, in most states, means pow- power and other renewable energy sys- ered up on or after 1/1/1999. See the tems and for energy efficiency improve- Mainstay Energy web site for ments. This program is authorized for exceptions; funding for up to $23,000,000 per year in 5. For any systems over 10 kW, the system 2003-2007, totaling up to $115 million. In generation must be metered separately. determining the amount of a grant or loan, For systems under 10 kW, separate USDA shall consider the type of renewable metering is not necessary. Payments energy system, the quantity of energy likely are made based on estimated to be generated, the expected environmen- production. tal benefits, the extent to which the system Contact: is replicable, and the amount of energy Mainstay Rewards Program savings from energy efficiency improve- Mainstay Energy ments and the likely payback period. 161 E. Chicago Ave. USDA Rural Development State Office Suite 41B contacts can be found at www.rurdev. Chicago, IL 60611-2624 usda.gov/rbs/farmbill/contacts.htm Phone: (877) 473-3682 Fax: (312) 896-1515 USDA Farm Bill Web site: www.rurdev. E-Mail: [email protected] usda.gov/rbs/farmbill/resourc.htm Web site: http://mainstayenergy.com Green Tag Purchase Program Mainstay Energy is a private company offering customers who install, or have installed, renewable energy systems the opportunity to sell the green tags (also known as renewable energy credits, or RECs) associated with the energy gener- ated by these systems. These green tags will be brought to market as Green-e* http://www.green-e.org or state certified products. Participating customers receive regular, recurring payments through the Mainstay Energy Rewards Program. Small Wind Electric Systems

Incentives for Small Wind in the United States For a comprehensive overview of the incentives for small wind projects, visit the DSIRE (Database of State Incentives for Renewables and Efficiency) Web site at www.dsireusa.org U.S. Department of Energy Wind Energy Program www.eere.energy.gov/windandhydro/

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, , 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 For more information contact: National Renewable Energy Laboratory, EERE Information Center a DOE national laboratory 1-877-EERE-INF (1-877-337-3463) www.eere.energy.gov DOE/GO-102007-2465 • August 2007

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