Small-Scale Wind Energy on the Farm


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Small-Scale Wind Energy on the Farm

  1. 1. Small-Scale Wind Energy on the Farm A Publication of ATTRA - National Sustainable Agriculture Information Service • 1-800-346-9140 • www.attra.ncat.orgBy Cathy Svejkovsky Wind-generated electricity is attracting the interest of farmers, ranchers, and other landowners acrossNCAT Energy Specialist the country. People find wind energy attractive for a variety of reasons, including its potential economic© 2007 NCAT benefits and its lower impact on the environment when compared to coal and other electric power generation fuels. Wind-generated electricity can help farmers and ranchers reduce their energy costs, an important consideration in these days of continually increasing utility rates.Contents This publication will introduce you to small-scale wind energy to help you decide if wind energy is an economical option for your farm or ranch.Introduction ..................... 1Why Should I ChooseWind? .................................. 1 This publication draws heavily on SmallHow Do Wind Turbines Wind Electric Systems: A U.S. Consum-Work? .................................. 1 er’s Guide (DOE/GO-102005-2095), pro-Is Wind Energy Practical duced by the National Renewable Energyfor Me? ............................... 2 Laboratory (NREL). Material from thisIs There Enough Wind at publication is reprinted and adapted hereMy Site? .............................. 3 with permission from NREL.Zoning Issues ................... 4What Size Wind TurbineDo I Need?......................... 4 IntroductionWhat are the Basic Partsof a Small Wind Electric Wind energy systems use the windSystem? .............................. 5 to generate electricity with a windWhat Do Wind Systems turbine. More and more peopleCost? .................................... 7 are considering wind energy asHow Much Energy WillMy System Generate? ... 7 they look for affordable and reli-Grid-Connected able sources of electricity. Small Farms and ranches, such as this one in southwest Minnesota, can use wind-generated electricity to reduce utility bills.Systems .............................. 8 wind electric systems can make Photo courtesy of NREL.Can I Sell My Excess an important contribution to ourElectricity to the nation’s energy needs. In 2005, or more) to provide a significant portion ofUtility? ................................ 9Financial Incentives ....... 9 the United States installed more new wind their electricity from wind power.References ...................... 10 energy capacity than any other country in the world. The new capacity, totaling 2,431 Why Should I Choose Wind? megawatts (MW), was worth more thanFunding for the development $3 billion in generating equipment, and it Wind energy can be a cost-effective small-of this publication was provided brought the total national wind energy capac- scale renewable energy system. Depend- ity to 9,149 MW. That’s enough electricity to ing on your wind resource and the electricby the USDA Risk ManagementAgency. power 2.3 million average American house- consumption on your farm, a small wind holds. In 2006, an additional 2,454 MW energy system can lower electricity bills, was installed, bringing the nation’s total help avoid the high costs of extending util-ATTRA—National Sustainable installed capacity to 11,603 MW. ity power lines to remote locations, preventAgriculture Information Ser-vice is managed by the National power interruptions, and provide a non-pol- Many rural areas have sufficient windCenter for Appropriate Technol- luting source of electricity.ogy (NCAT) and is funded under speeds to make wind an attractive alterna-a grant from the United States tive, and farms and ranches can often install a small-scale wind energy system without How Do Wind Turbines Work?Department of Agriculture’sRural Business- CooperativeService. Visit the NCAT Web site( impacting their ability to plant crops and Wind is created by the unequal heating ofhtml) for more informa- graze livestock. Most farms and ranches the Earth’s surface by the sun. Wind tur-tion on our sustainableagriculture projects. have enough open land (generally an acre bines convert the kinetic energy in wind
  2. 2. you are also interested in benefits such as environmental protection, independence, or energy security, you may fi nd the cost and payback period to be perfectly accept- able. Make sure you fully understand the results you can expect, as well as potential obstacles, such as zoning laws, generation capacity, maintenance requirements, and warranty coverage. First Things First: Make Your Farm Buildings as Energy-Efficient as Possible Before choosing a wind system for your farmWind turbines operate in harmony with farming and ranching. Photo courtesy or ranch, you should reduce your energy con-of NREL. sumption as much as possible. This topic is discussed in greater detail in the ATTRA into mechanical power that runs a genera- publication Efficient Agricultural Buildings: tor to produce clean electricity. Today’s tur- An Overview. Energy conservation is almost bines are versatile sources of electricity. always more cost-effective than renewable Their blades are aerodynamically designed energy systems, and could reduce the size of to capture the maximum energy from the your wind energy system. From wall insula-Related ATTRA wind. The wind turns the blades, which tion to light bulbs, there are many ways toPublications spin a shaft connected to a generator that make your farm buildings more efficient.Renewable Energy makes electricity. • Reduce your heating and cooling needs byOpportunities on up to 30% by investing just a few hundredthe Farm Is Wind Energy Practical for Me? dollars in proper insulation and weather-Wind-Powered A small wind energy system can provide ization products.Electric Systems for you with a practical and economical sourceHomes, Farms, and • Save money and increase comfort by prop- of electricity if: erly maintaining and upgrading your heating,Ranches: ResourcesEfficient Agricultural • your property has a good wind ventilation, and air-conditioning systems.Buildings: An resource • Install double-paned, gas-filled windowsOverview • you have at least one acre of land in with low-emissivity (low-e) coatings to a rural area reduce heat loss in cold climates and spec- trally selective coatings to reduce heat gain • your local zoning codes or covenants in warm climates. allow wind turbines • Replace your lights in high-use areas with flu- • you have high electric costs orescents. Replacing 25% of your lights can • your property is in a remote loca- save about 50% of your lighting energy bill. tion that does not have easy access • When shopping for products such as light- to utility lines ing, windows, and heating and cooling • you are comfortable with long-term systems, look for the ENERGY STAR® label. investments ENERGY STAR® products have been identi- It’s important to examine your reasons for fied by the U.S. Environmental Protection wanting to purchase a wind energy system. If Agency and U.S. Department of Energy as your reasons are purely economic, you could being the most energy-efficient products end up disappointed, since wind energy in their classes. systems can have long payback periods. IfPage 2 ATTRA Small-Scale Wind Energy on the Farm
  3. 3. Is There Enough Wind atMy Site?Does the wind blow hard and consistentlyenough at your site to make a small windturbine system economically worthwhile?That is a key question and not always eas-ily answered. The wind resource can varysignificantly over an area of just a few milesbecause of local terrain influences on thewind flow. Yet, there are steps you can takethat can help answer this question.As a fi rst step, a wind resource map canhelp you estimate the wind resource inyour region. State wind resource maps,such as those found on the Wind Pow-ering America website ( will help you understand Source: U.S. Department of Energy.the resources in your specific region.Note that maps for some states show windspeed estimates at 50 meters above the along seacoasts, on ridgelines, and in theground and depict the resource that could Great Plains; however, many areas havebe used for utility-scale wind develop- wind resources strong enough to powerment. DOE’s future plans include provid- a small wind turbine economically. Theing wind speed estimates at 30 meters, wind resource estimates on the map abovewhich are useful for identifying small generally apply to terrain features that arewind turbine opportunities. well-exposed to the wind, such as plains, hilltops, and ridge crests.You can fi nd additional wind resourcemaps, showing region-specifi c data, in Another way to estimate the wind resourceNREL’s Wind Energy Resource Atlas is to get average wind speed informationof the United States, available online at from a nearby airport. Use caution, how- For ever, because local terrain and other factorswestern regions, consult windpowermaps. may cause the wind speed recorded at anorg and The Renewable Energy Atlas of airport to be different from your particu-the West, available at www.energyatlas. lar location. Also, airport wind speeds areorg. For California only, consult Califor- generally measured at heights of only aboutnia Wind Resource Maps at 20-33 feet (6–10 meters) above Note that wind Average wind speeds increase with heightmaps provide only broad estimates—the and may be 15–25% greater at a typi-wind speed for any particular site is often cal small wind turbine hub-height of 80a prediction based on terrain, rather feet (24 meters) than those measured atthan an actual measurement. The actual airport anemometer heights. The Nationalwind resource at a specific site may differ Climatic Data Center collects data fromconsiderably from these estimates. For airports in the United States and makessite-specific wind resource data, consult wind data summaries available for pur-a turbine dealer or install an anemometer chase. Summaries of wind data from(a device that measures wind speed) on almost 1,000 U.S. airports also areyour property. included in Wind Energy Resource AtlasIn general, the highest average wind of the United States, available online atspeeds in the United States are found ATTRA Page 3
  4. 4. are those taken at hub-height. If there is a small wind turbine system in your area, you may be able to obtain information on the annual output of the system or wind speeds at its location. Zoning Issues Before you invest in a wind energy system, you should research potential obstacles. Some jurisdictions, for example, restrict the height of the structures permitted in resi- dentially zoned areas, although variances might be allowed. Most zoning ordinances have a height limit of 35 feet. You can find out about the zoning restrictions in your area by calling the local building inspector, board of supervisors, or planning board. As a minimum, contact the county commission to ask what, if any, county requirementsFlagging, the effect of strong winds on area vegetation, can help determine area exist. They can tell you if you will need towind speeds. Source: Windustry. obtain a building permit and provide you with a list of requirements. In addition to Another useful, indirect way to measure zoning issues, your neighbors might object the wind resource is by observing vege- to a wind machine that blocks their view, tation. Trees, especially conifers or ever- or they might be concerned about noise. greens, can be permanently deformed by Most zoning and aesthetic concerns can be strong winds. This deformity, known as addressed by supplying objective data. “flagging,” has been used to estimate the For more information about permitting, average wind speed for an area. For more see AWEA’s Small Wind Toolbox: Getting a information on flagging, you may want to Building Permit at obtain A Siting Handbook for Small Wind toolbox2/INSTALL/building_permits.html Energy Conversion Systems, by H. Weg- ley, J. Ramsdell, M. Orgill & R. Drake, Report No. PNL-2521, available from What Size Wind Turbine National Technical Information Service Do I Need? at or (703) 605-6585. The size of the wind turbine you need Direct monitoring by a wind resource depends on your application. Most turbines measurement system at a site provides the are rated according to peak wattage. Small clearest picture of the available resource. turbines are rated from 100 watts to 100 A good overall guide on this subject is kilowatts (one kilowatt equals 1,000 watts). the Wind Resource Assessment Handbook, One- to 10-kW turbines can be used in available online at applications such as pumping water. legosti/fy97/22223.pdf. Wind measure- A wind turbine manufacturer can provide ment systems are available for as little you with the expected annual energy output as $600 to $1,200. This expense may of the turbine as a function of annual aver-This 1-kW wind turbine from or may not be justified, depending on the age wind speed. The manufacturer will alsoWorld Power Technology, exact nature of your proposed small wind provide information on the maximum windInc. is used for pumping system. The measuring equipment must speed for safe operation. Most turbines havewater for 120 head ofcattle at a ranch in Texas. be set high enough to avoid turbulence automatic overspeed-governing systems toSource: World Power created by trees, buildings, and other keep the rotor from spinning out of controlTechnology. obstructions. The most useful readings in very high winds. This information, alongPage 4 ATTRA Small-Scale Wind Energy on the Farm
  5. 5. with your local wind speed and your energy its “swept area,” or the quantity of windbudget, will help you decide what size of intercepted by the turbine. The turbine’sturbine will best meet your electric needs. frame is the structure onto which the rotor, generator, and tail are attached. The tailWhat are the Basic Parts of a keeps the turbine facing into the wind.Small Wind Electric System?Home-scale wind energy systems are gen- Towererally comprised of a rotor, a generator or Because wind speeds increase with height,alternator mounted on a frame, a tail, a the turbine is mounted on a tower. In gen-tower, wiring, and the “balance of system” eral, the higher the tower, the more energycomponents: controllers, inverters, and/ the wind system can produce. The toweror batter ies. Through the spinning blades, also raises the turbine above the air tur-the rotor captures the kinetic energy of the bulence caused by obstructions such aswind and converts it into rotary motion to hills, buildings, and trees. As a generaldrive the generator. rule of thumb, the bot tom of the rotor blades should be at least 30 feet (9 meters)To find wind equipment suppliers and above any obstacle that is within 300 feetinstallers in your area, as well as sources (90 meters) of the tower. Relatively smallof technical support, see ATTRA’s Farm investments in increased tower height canEnergy Search Tool at yield very high rates of return in energyenergy.php production. For instance, raising a 10-kW generator from a 60-foot tower height toWind Turbine a 100-foot tower increases system costMost turbines manufactured today are hor- by about 10%, but can increase energyizontal-axis, upwind machines (the rotor production by 29%.faces the wind) with two or three blades,which are usually made of a composite Mounting turbines on rooftops is not rec-material such as fiberglass. These machines ommended. All wind turbines vibrate andare designed so that turbines rotate around transmit the vibration to the structure ona horizontal axis, and the rotor is placed on which they are mounted. This can leadthe windward side of the support tower. to noise and structural problems with the building, and the roofl ine can cause exces-The amount of power a turbine will produce sive turbulence that will shorten the life ofis determined primarily by the diameter of the turbine.its rotor. The diameter of the rotor defi nes Balance of System The parts that you need in addition to the turbine and the tower, or the balance of sys- tem parts, will depend on your application. Most manufacturers can provide you with a system package that includes all the parts you need for your application. For example, the parts required for a water pumping sys- tem will be much different than what you need for a residential application. The bal- ance of system required will also depend on whether the system is grid-connected (connected to the utility grid), stand-alone (independent of the utility grid), or part ofBergey XL-1 horizontal-axis upwind machine. a hybrid system (a power system that usesSource: Bergey Windpower. more than one source of energy—wind ATTRA Page 5
  6. 6. Types of Towers There are three basic types of towers suitable for farm-sized turbines: Monopole This type of tower is generally the least expensive. The tower is a tilt-up style tower and is generally installed using a gin-pole and winch. Monopoles generally have four guy wires for support. Maintenance on the turbine is performed by tilting the tower down. The height of this type of tower is limited by the weight of the machine and generally 10-kW machines are the largest that can be placed on such towers. Tilt-up towers require space for guy wires and for tipping up and down of the tower. Guyed lattice Guyed lattice towers are generally more expensive than monopole designs but can sup- port larger turbines at higher heights. Towers are generally installed using gin-pole and winch. Guyed lattice towers also come with the advantage of either being able to tip the tower down or relatively easy climb-ability for regular maintenance (climbing, if done with appropriate safety precautions, gear and training, Monopole tower. is much safer than tilting a tower up and down every time maintenance is required). Guyed lattice towers require much space for tipping up and down of tower and guy wires. Again, check with turbine manufactures to see what tower options they recommend with various turbine models. Lattice Lattice towers, in most cases, are required for machines larger than 20 kW in size. The installation of these towers is generally more complicated than that of a guyed lat- tice tower because a crane is needed to lift the tower and turbine into place. Maintenance is performed by climbing the tower. If major work is required on a machine a crane may be required to remove the turbine from the tower. Check with manufacturers to determine what tower Guyed lattice tower . options they recommend with different turbine models. Lattice tower. Source: photovoltaics, for example). For a residen- ity hundreds of times, which makes them tial grid-connected application, the balance a good option for remote renewable energy of system parts may include a controller, systems. Automotive batteries are shallow- storage batteries, a power conditioning unit cycle batteries and should not be used in (inverter), and wiring. renewable energy systems because of their short life in deep-cycling operations. Stand-Alone Systems Small wind turbines generate direct current Stand-alone systems (systems not con- (DC) electricity. In very small systems, DC nected to the utility grid) often require appliances operate directly off the batter- batteries to store excess power for use ies. If you want to use standard appliances when the wind is calm. They also need that use conventional household alternating a charge controller to keep the batter- cur rent (AC), you must install an inverter ies from overcharging. Deep-cycle batter- to convert DC electricity from the batteries ies, such as those used for golf carts, can to AC. Although the inverter slightly lowers discharge and recharge 80% of their capac- the overall efficiency of the system, it allowsPage 6 ATTRA Small-Scale Wind Energy on the Farm
  7. 7. be competitive with conventional energy Can I Install a Wind Energy sources when you account for a lifetime of System Myself? reduced or avoided utility costs. The length “Most dealers offer either complete turn- of the payback period—the time before the key (ready-to-operate) installations or the savings resulting from your system equal option to purchase direct from the fac- the cost of the system itself—depends on tory and install the system yourself. The the system you choose, the wind resource first option offers more customer support on your site, electric costs in your area, and from the company. Self-installation offers how you use your wind system. significant savings and a hands-on under- standing of the turbine. Prospective own- ers can discuss the options available with How Much Energy Will My manufacturers to decide which method System Generate? best suits their budget and technical skills.” As mentioned above, most U.S. manufac- –American Wind Energy Association turers rate their turbines by the amount of power they can safely produce at a par- ticular wind speed. Even a small increasethe home to be wired for AC, a definite plus in wind speed results in a large increasewith lenders, electrical code officials, and in power. That is why a taller tower willfuture homebuyers. increase the productivity of any wind tur-For safety, batteries should be isolated from bine by giving it access to higher windliving areas and electron ics because they speeds, as shown in the graph below.contain corrosive and explosive substances.Lead-acid batteries also require protec-tion from temperature extremes. Batteriesshould be enclosed in a box, which should Wind Speeds Increase with Heightbe vented to the outside. 150What Do Wind Systems Cost?According to the American Wind EnergyAssociation (AWEA), small wind energysystems cost from $6,000 to $8,000 for 120every kilowatt of generating capacity,depending on size. Smaller wind systemsare more costly per kilowatt of installedcapacity. Wind energy becomes more Tower Height, ft 90cost-effective as the size of the turbineincreases. Although small turbines costless in initial outlay, they are proportion-ally more expensive. 60A 10-kW system, for example, can cost$47,000 to $60,000 installed. Rebates,tax credits, and other incentives can reducethese costs. Well-sited small wind turbines 30can usually pay for themselves within 15years, about half their serviceable life-times, if the right incentives are applied,says AWEA. 0 0 41 75 100 124Although wind energy systems involve asignificant initial investment, they can Increase in wind power, ATTRA Page 7
  8. 8. Air Density Change with Elevation manufacturer or dealer for assistance with 10,000 this calculation. 9,000 To get a preliminary estimate of the perfor- 8,000 mance of a particular wind turbine, use the formula below. 7,000 6,000 AEO = 0.01328 D2 V3Elevation, ft 5,000 Where: 4,000 AEO = Annual energy output, kWh/year D = Rotor diameter, feet 3,000 V = Annual average wind speed, mph 2,000 1,000 Wind Powering America’s Wind Energy 0 Payback Period Workbook is a spreadsheet 70 75 80 85 90 95 100 tool that can help you analyze the econom- ics of a small wind electric system and The larger the rotor, the more energy it can decide whether wind energy will work for you. The spreadsheet can be found online at capture. The air density changes slightly with air temperature and with elevation. windpoweringamerica/docs/wind_payback.xls. The ratings for wind turbines are based on The tool asks you to provide information standard conditions of 59° F (15° C) at sea about how you’re going to fi nance the sys- level. A density correction should be made tem, the characteristics of your site, and the for higher elevations as shown in the graph properties of the system you’re considering. above. A correction for temperature is typi- It then provides you with a simple payback cally not needed for predicting the long- estimate in years. term performance of a wind turbine. The best mea sure of wind turbine perfor- Grid-Connected Systems mance is annual energy output. The dif- Small wind energ y systems can be ference between power and energy is that connected to the electric distribution sys- power (kilowatts [kW]) is the rate at which tem and are then called grid-connected electric energy is consumed, while energy systems. Grid-connected systems require (kilowatt-hours [kWh]) is the quantity con- a power conditioning unit (inverter), which sumed. An estimate of the annual energy makes the turbine output electrically output from your wind turbine, kWh/year, compatible with the utility grid. Usually, is the best way to determine whether a par- batteries are not needed. A grid-con- ticular wind turbine and tower will produce nected wind turbine can reduce your con- enough electric energy to meet your needs. sumption of utility-supplied electricity for A wind turbine manufacturer or dealer lighting, appliances, and electric heat. If can help you estimate the energy produc- the turbine cannot deliver the amount of tion you can expect. They will use a cal- energy you need, the utility makes up the culation based on the particular wind tur- difference. When the wind system pro- bine power curve, the average annual wind duces more electricity than the household speed at your site, the height of the tower requires, the excess is sent or sold to the that you plan to use, the elevation, and (if utility. Grid-connected systems can be practical if the following conditions exist: available) the frequency distribution of the wind–an estimate of the number of hours • You live in an area with average that the wind will blow at each speed dur- annual wind speed of at least 10 ing an average year. Contact a wind turbine mph (4.5 m/s).Page 8 ATTRA Small-Scale Wind Energy on the Farm
  9. 9. A grid-connected wind turbinecan reduce your consumptionof utility-supplied electricity.Source: U.S. Department of Energy. • Utility-supplied electricity is expen- or PURPA) require utilities to connect sive in your area (about 10 to 15 with and purchase power from small wind cents per kilowatt-hour). energy systems. However, you must contact • The utility’s requirements for con- your utility before connecting to its distribu- necting your system to its grid are tion lines to address any power quality and not prohibitively expensive. safety concerns. Be aware that some utili- ties are more welcoming to interconnection • There are good incentives for the sale of excess electricity or for the than others. It is important that, early on purchase of wind turbines. in your planning process, you contact your utility to learn about its interconnection policies and expected costs. The AmericanCan I Sell My Excess Wind Energy Association is another goodElectricity to the Utility? source for information on utility intercon-Federal regulations (specifically, the Pub- nection requirements.lic Utility Regulatory Policies Act of 1978, Financial Incentives Financial incentives can make wind energy more affordable for farmers and ranchers. You can fi nd out what incentives exist at both state and federal levels at the Database of State Incentives for Renewable Energy (DSIRE) at Wind energy can be an attractive alterna- tive for farms and ranches across the coun- try, offering numerous benefits, including reduced energy costs, reduced environ- mental impact, and increased energy inde- pendence. However, as with all renewable energy systems, there also are challenges to these systems. Conduct a careful analy- sis of your energy needs and wind resourceSmall wind turbines can provide supplemental powerfor farms and ranches, such as this farm in western potential, as well as system economics, ben-Kansas. Excess power is fed back into the utility grid. efits, and potential obstacles, to see if windSource: Warren Gretz, NREL. is a good choice for your farm or ATTRA Page 9
  10. 10. ReferencesAdvantages and Disadvantages of Wind Energy, U.S. Union of Concerned ScientistsDepartment of Energy, Wind & Hydropower Technolo- www.ucsusa.orggies Program. U.S. Department of Energy Wind and Hydropower Technologies ProgramConsumer’s Guide to Renewable Energy in Arkansas, Energy Office, October Windustry www.windustry.orgThe Consumer’s Guide to Small Wind and Solar Photo-voltaic Generation, NorthWestern Energy, 2007. Publications/LinksThe Economics of Small Wind, American Wind Energy Burton, Tony, David Sharpe, Nick Jenkins, and ErvinAssociation. Bossanyi. Wind Energy Handbook, November 2001fs_economics.aspSmall Wind Electric Systems: A U.S. Consumer’s Guide, Farming the Wind: Wind Power and Agriculture, UnionNational Renewable Energy Laboratory, (NREL). of Concerned Scientists. 2005. renewable_energy_basics/farming-the-wind-wind-power-windpoweringamerica/pdfs/small_wind/small_wind_ and-agriculture.htmlguide.pdf Gipe, Paul. Wind Energy Basics: A Guide to SmallWind Energy: Harnessing the Wind to Generate Elec- and Micro Wind Systems, April 1999.tricity, Environmental and Energy Study Institute, May Gipe, Paul. Wind Power, Revised Edition: Renewable2006. Energy for Home, Farm, and Business. April 2004.Fact_Sheets/Wind_Energy.pdf Paul, Greg, New and Improved Wind Power, MotherMontana Wind Power: A Consumer’s Guide to Harness-ing the Wind, NorthWestern Energy, December 2004. Earth News, June/July 2007. com/Alternative-Energy/2007-06-01/Improved-Wind-pub.pdf Power.aspxWind Powering America program brochure, www.eere. A Primer on Small Turbines, Bergey Windpower Sullivan, Dan. Farming the Wind: The nuts and bolts of blade design, site selection and tower technology,Resources The New Farm, Wind Energy Association Wind Energy FAQs for Consumers, U.S. Department ofFarm Energy Search Tool Energy Wind and Hydropower Technologies Program. Renewable Energy Laboratory Wind Energy Payback Period Workbook, WindNational Wind Coordinating Collaborative Powering America. windpoweringamerica/docs/wind_payback.xlsPage 10 ATTRA Small-Scale Wind Energy on the Farm
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  12. 12. Small-Scale Wind Energy on the Farm By Cathy Svejkovsky NCAT Energy Specialist © 2007 NCAT This publication is available on the Web at: or IP311 Slot 310 Version 082307Page 12 ATTRA