Small Wind Electric Systems

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

Introduction
Can I use wind energy to power my
home? Spiraling utility bills, the
need for uninterrupted service,
and concerns over environmental
impacts are generating increasing
interest in small wind energy
systems.
Small wind electric systems can
make a significant contribution to
our nation's energy needs. Although
wind turbines large enough to pro-
vide a significant portion of the elec-
tricity needed by the average U.S.
home generally require one acre of




                                                                                                                                  Bergey Windpower/PIX01476
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.
                                          Homeowners, ranchers, and small businesses can use wind-
But will a small wind electric system     generated electricity to reduce their utility bills. This grid-
work for you?                             connected system installed for a home in Norman, Oklahoma,
                                          reduces the homeowner's utility bill by $100 per month.
• Is there enough wind where you
  live?
• Do they allow tall towers in your         Contents
  neighborhood or rural area?               Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
• Do you have enough space?                 First, How Can I Make My Home More Energy Efficient? . . . .2
                                            Is Wind Energy Practical for Me? . . . . . . . . . . . . . . . . . . . . . .3
• How much electricity do you need
  or want to produce?                       Is There Enough Wind on My Site? . . . . . . . . . . . . . . . . . . . . .4
                                            What Size Wind Turbine Do I Need? . . . . . . . . . . . . . . . . . . . .5
• Do you want to connect to the
                                            What are the Basic Parts of a Small Wind Electric System? . .6
  utility grid or be grid independent?
                                            What Do Wind Systems Cost? . . . . . . . . . . . . . . . . . . . . . . . .9
• Can you afford a wind energy              Where Can I Find Installation and Maintenance Support? . . .10
  system?
                                            How Much Energy Will My System Generate? . . . . . . . . . . .11
• What does it take to install and          How Do I Choose the Best Site for My Wind Turbine? . . . . .15
  maintain a system?                        Can I Connect My System to the Utility Grid? . . . . . . . . . . . .15
These are just a few of the questions       Can I Go "Off-Grid"? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
you need to answer before you can           Glossary of Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
determine if a wind energy system           For More Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
will work for you. The purpose of this
2   Small Wind Electric Systems                                                                                                                                                         Small Wind Electric Systems                                    3

                guide is to provide you with the basic                   Home Energy Use
                                                                                                                          replacing 25% of your lights, you      • your property is in a remote
                information you need to answer those                Based on national averages                            can save about 50% of your lighting      location that does not have easy
                questions and to address the many                                                                         energy bill.                             access to utility lines
                factors you need to consider to suc-                                                                    • When shopping for appliances,          • you are comfortable with long-term
                                                                          Water
                cessfully install a small wind energy                    heating                                          look for the ENERGY STAR® label.         investments.
                system and get maximum production.                        14%
                                                                                                                          ENERGY STAR® appliances have
                                                                                          Heating and                                                            Zoning Issues
                Why Should I Choose Wind?                        Lighting,                  cooling
                                                                                                                          been identified by the U.S.
                                                                 cooking,                    44%                          Environmental Protection Agency        Before you invest in a wind energy
                Wind energy systems are one of the              and other                                                                                        system, you should research potential
                most cost-effective home-based                                                                            and U.S. Department of Energy as
                                                                appliances                                                                                       obstacles. Some jurisdictions, for
                renewable energy systems.                          33%                                                    being the most energy-efficient
                                                                                                                                                                 example, restrict the height of the




                                                                                                            02979309m
                Depending on your wind resource, a                                                                        products in their classes.
                                                                                                                                                                 structures permitted in residentially
                small wind energy system can lower                                                                      • For more information on how to         zoned areas, although variances are
                your electricity bill by 50% to 90%,                                                                      make your home energy efficient,       often obtainable. Most zoning ordi-
                                                                                       Refrigerator 9%
                help you avoid the high costs of hav-                                                                     see Energy Savers, under For More      nances have a height limit of 35 feet.
                ing utility power lines extended to        The largest portion of a utility bill for a typical            Information.                           You can find out about the zoning
                remote locations, prevent power            house is for heating and cooling.
                                                                                                                                                                 restrictions in your area by calling the
                interruptions, and it is nonpolluting.                                                                  Is Wind Energy Practical
                                                                                                                                                                 local building inspector, board of
                Over its life, a small residential wind    reduce the size of the home-based                            for Me?                                  supervisors, or planning board. They
                turbine can offset approximately           renewable energy system you need.                            A small wind energy system can pro-      can tell you if you will need to obtain
                1.2 tons of air pollutants and 200 tons    To achieve maximum energy effi-                              vide you with a practical and econom-    a building permit and provide you
                of greenhouse gases (carbon dioxide        ciency, you should take a whole-                             ical source of electricity if:           with a list of requirements.
                and other gases that cause climate         building approach. View your home
                                                                                                                        • your property has a good wind          In addition to zoning issues, your
                change).                                   as an energy system with interrelated
                                                                                                                          resource                               neighbors might object to a wind
                                                           parts, all of which work synergisti-
                How Do Wind Turbines Work?                                                                              • your home or business is located on    machine that blocks their view, or
                                                           cally to contribute to the efficiency of
                Wind is created by the unequal heat-       the system. From the insulation in                             at least one acre of land in a rural   they might be concerned about noise.
                ing of the Earth's surface by the sun.     your home's walls to the lightbulbs in                         area                                   Most zoning and aesthetic concerns
                Wind turbines convert the kinetic          its fixtures, there are many ways you                                                                 can be addressed by supplying objec-
                                                                                                                        • your local zoning codes or
                energy in wind into mechanical             can make your home more efficient.                                                                    tive data. For example, the ambient
                                                                                                                          covenants allow wind turbines
                power that runs a generator to pro-                                                                                                              noise level of most modern residential
                duce clean, nonpolluting electricity.      • Reduce your heating and cooling                            • your average electricity bills are     wind turbines is around 52 to 55 deci-
                Today's turbines are versatile modular       needs by up to 30% by investing                              $150 per month or more                 bels. This means that while the sound
                sources of electricity. Their blades are     just a few hundred dollars in
                aerodynamically designed to capture          proper insulation and                                                                                                                                                In Clover Valley,
                the maximum energy from the wind.            weatherization products.                                                                                                                                             Minnesota, this
                                                                                                                                                                                                                                  3-kW Whisper
                The wind turns the blades, which spin      • Save money and increase comfort                                                                                                                                      turbine on a
                a shaft connected to a generator that        by properly maintaining and                                                                                                                                          50-foot tower is
                                                                                                                                                                                                                                  connected to the
                makes electricity.                           upgrading your heating,
                                                                                                                                                                                                                                  utility grid to offset
                                                             ventilation, and air-conditioning                                                                                                                                    the farm's utility-
                First, How Can I Make My                     system.                                                                                                                                                              supplied electricity.
                Home More Energy                           • Install double-paned, gas-filled
                Efficient?                                   windows with low-emissivity (low-
                Before you choose a wind system for          e) coatings to reduce heat loss in




                                                                                                                                                                                                            World Power Technology/PIX07168
                your home, you should consider               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
                                                           • Replace your lights in high-use
                energy consumption will significantly
                                                             areas with fluorescents. By
                lower your utility bills and will
4   Small Wind Electric Systems                                                                                                                                                                                                    Small Wind Electric Systems                   5

                of the wind turbine can be picked out        wind speed information from a                                                                                                                                                                   Flagging, the
                of surrounding noise if a conscious          nearby airport. However, caution                                        Flagging                                                                                                                effect of strong
                                                                                                                                                                                              0                                      I                       winds on area
                effort is made to hear it, a residential-    should be used because local terrain                               Prevailing wind                                               No                                     Brushing
                                                                                                                                                                                                                                                             vegetation, can
                                                                                                                                                                                              deformity                              and slight
                sized wind turbine is no noisier than        influences and other factors may                                                                                                                                        flagging                help determine
                your average refrigerator.                   cause the wind speed recorded at an                                                                                                                                                             area wind speeds.
                                                             airport to be different from your par-
                Is There Enough Wind                         ticular location. Airport wind data are                                              II                                          III                                    IV
                on My Site?                                  generally measured at heights about                                                  Slight                                      Moderate                               Complete
                                                                                                                                                  flagging                                    flagging                               flagging
                Does the wind blow hard and consis-          20–33 ft (6–10 m) above ground.
                tently enough at my site to make a           Average wind speeds increase with
                small wind turbine system economi-           height and may be 15%–25% greater
                cally worthwhile? That is a key ques-        at a typical wind turbine hub-height
                                                             of 80 ft (24 m) than those measured at                                               V                                           VI                                     VII
                tion and not always easily answered.                                                                                              Partial                                     Complete                               Carpeting
                The wind resource can vary signifi-          airport anemometer heights. The                                                      throwing                                    throwing
                cantly over an area of just a few miles      National Climatic Data Center collects
                because of local terrain influences on       data from airports in the United States                                                                                                                                 02979310m
                the wind flow. Yet, there are steps you      and makes wind data summaries
                can take that will go a long way             available for purchase. Also, sum-                                                          Griggs-Putnam Index of Deformity
                towards answering the above ques-            maries of wind data from almost 1000                                 Index             I         II                 III            IV            V           VI           VII
                tion.                                        U.S. airports are included in the Wind                               Wind, mph       7-9        9-11       11-13                 13-16        15-18         16-21        22+
                                                             Energy Resource Atlas of the United                                  Speed, m/s      3-4        4-5              5-6              6-7           7-8          8-9          10
                As a first step, wind resource maps
                                                             States.
                like the one in this publication can be
                used to estimate the wind resource in        Another useful indirect measurement        by trees, buildings, and other obstruc-                                               What Size Wind Turbine
                your region. The highest average             of the wind resource is the observa-       tions. The most useful readings are
                                                             tion of an area’s vegetation. Trees,
                                                                                                                                                                                              Do I Need?
                wind speeds in the United States are                                                    those taken at hub-height, the eleva-
                generally found along seacoasts, on          especially conifers or evergreens, can                                                                                           The size of the wind turbine you need
                                                                                                        tion at the top of the tower where the                                                depends on your application. Small
                ridgelines, and on the Great Plains;         be permanently deformed by strong          wind turbine is going to be installed.
                however, many areas have wind                winds. This deformity, known as                                                                                                  turbines range in size from 20 watts to
                                                                                                        If there is a small wind turbine system                                               100 kilowatts. The smaller or "micro"
                resources strong enough to power a           "flagging," has been used to estimate      in your area, you may be able to
                small wind turbine economically. The         the average wind speed for an area.                                                                                              (20–500-watt) turbines are used for a
                                                                                                        obtain information on the annual out-                                                 variety of applications such as charg-
                wind resource estimates on this map          For more information on the use of "       put of the system and also wind speed
                generally apply to terrain features that     flagging" you may want to obtain A                                                                                               ing batteries for recreational vehicles
                                                                                                        data if available.                                                                    and sailboats.
                are well exposed to the wind, such as        Siting Handbook for Small Wind
                plains, hilltops, and ridge crests. Local    Energy Conversion Systems (see For
                terrain features may cause the wind          More Information).                                                                         Relative Size of Small Wind Turbines
                                                                                                                                                                                     40
                resource at a specific site to differ con-   Direct monitoring by a wind resource                           8
                siderably from these estimates. More         measurement system at a site pro-




                                                                                                                                                                    Swept area, m2
                                                                                                                                                                                     30
                detailed wind resource information,          vides the clearest picture of the avail-
                                                                                                                            7
                                                                                                                                                        7m
                including the Wind Energy Resource           able resource. A good overall guide on                                                                                  20
                                                                                                                            6
                Atlas of United States, published by the                                                                                                6m
                                                             this subject is the Wind Resource
                                                                                                        Rotor Diameter, m




                U.S. Department of Energy (DOE),             Assessment Handbook (see For More                              5                                                        10
                                                                                                                                                        5m
                can be found at the National Wind            Information). Wind measurement sys-                            4                                                         0
                Technology Center web site at                tems are available for costs as low as                                                     4m                                1          2       3       4         5      6                  7
                http://www.nrel.gov/wind/ and the                                                                                                                                                         Rotor Diameter, m
                                                             $600 to $1200. This expense may or                             3
                                                                                                                                                        3m
                DOE Windpowering America web site            may not be hard to justify depending
                at http://www.eren.doe.gov/wind-             on the exact nature of the proposed
                                                                                                                            2
                                                                                                                                                        2m




                                                                                                                                                                                                                                             02979303m
                poweringamerica/.                            small wind turbine system. The meas-                           1
                                                             urement equipment must be set high                                                         1m
                Another way to indirectly quantify
                                                                                                                            0
                the wind resource is to obtain average       enough to avoid turbulence created                                                                                                      Source: Paul Gipe, Wind Energy Basics
6       Small Wind Electric Systems                                                                                                                                                                                   Small Wind Electric Systems            7

    This 1 kW Whisper                                                                       production, making your house more                                                               the air turbulence that can exist close
    turbine provides
                                                                                                                                                 Basic Parts of a Small
                                                                                            energy efficient first will probably be              Wind Electric System                        to the ground. A general rule of
    direct AC power
    for the water pump                                                                      more cost effective because you may                                                              thumb is to install a wind turbine on a
                                                                                                                                             Rotor
    for stock tanks on                                                                      need a smaller wind turbine to meet                                                              tower with the bottom of the rotor
    a ranch in Wheeler,                                                                     your needs (see How Can I Make My                                             Tail
                                                                                                                                                Generator/                                   blades a least 30 feet (9 meters) above
    Texas.                                                                                                                                      alternator
                                                                                            Home More Energy Efficient?). Wind                                                               any obstacle that is within 300 feet (90
                                                                                            turbine manufacturers can help you                                                               meters) of the tower. Relatively small




                                                                                                                                                                                 02979312m
                                                                                            size your system based on your elec-                                                             investments in increased tower height
                                                                                            tricity needs and the specifics of local                                                         can yield very high rates of return in
                                                                                            wind patterns.                                           Tower                                   power production. For instance, to
                                                                                            A typical home uses approximately                                                                raise a 10-kW generator from a 60-foot
                                                                                            9400 kilowatt-hours (kWh) of electric-                                                           tower height to a 100-foot tower
                                                                                            ity per year (about 780 kWh per                                                                  involves a 10% increase in overall sys-
                                                                                            month). Depending on the average            and/or batteries. Through the spin-                  tem cost, but it can produce 25% more
                                                                                                                                                                                             power.
                                                                   Elliott Bayly/PIX09681
                                                                                            wind speed in the area, a wind tur-         ning blades, the rotor captures the
                                                                                            bine rated in the range of 5 to 15 kilo-    kinetic energy of the wind and con-                  There are two basic types of towers:
                                                                                            watts (kW) would be required to             verts it into rotary motion to drive the             self-supporting (free standing) and
                                                                                            make a significant contribution to this     generator.                                           guyed. Most home wind power sys-
                                                                                            demand. A 1.5- kW wind turbine will                                                              tems used a guyed tower. Guyed tow-
                                                                                                                                        Wind Turbine
                          One- to 10-kW turbines can be used                                meet the needs of a home requiring                                                               ers, which are the least expensive, can
                          for applications such as pumping                                  300 kWh per month in a location with        Most turbines manufactured today are                 consist of lattice sections, pipe, or tub-
                          water. Wind energy has been used for                              a 14-mile-per-hour (6.26-meters-per-        horizontal axis upwind machines that                 ing depending on the design, and
                          centuries to pump water and grind                                 second) annual average wind speed.          have two or three blades, which are                  supporting wires. They are easier to
                          grain. Although mechanical wind-                                  The manufacturer can provide you            usually made of a composite material                 install than self-supporting towers.
                          mills still provide a sensible, low-cost                          with the expected annual energy out-        such as fiberglass.                                  However, because the guy radius
                          option for pumping water in low-                                  put of the turbine as a function of         The amount of power a turbine will                   must be one-half to three-quarters of
                          wind areas, farmers and ranchers are                              annual average wind speed. The man-         produce is determined primarily by                   the tower height, guyed towers
                          finding the wind-electric pumping                                 ufacturer will also provide informa-        the diameter of its rotor. The diameter              require enough space to accommodate
                          system to be a little more versatile and                          tion on the maximum wind speed at           of the rotor defines its "swept area," or            them. While tilt-down towers are
                          they can pump twice the volume for                                which the turbine is designed to oper-      the quantity of wind intercepted by                  more expensive they offer the con-
                          the same initial investment. In addi-                             ate safely. Most turbines have auto-        the turbine. The turbine's frame is the              sumer an easy way to perform main-
                          tion, mechanical windmills must be                                matic overspeed-governing systems           structure onto which the rotor, genera-              tenance. If the consumer decides to
                          placed directly above the well, which                             to keep the rotor from spinning out of      tor, and tail are attached. The tail                 maintain the turbine herself, a tilt-
                          may not take the best advantage of                                control in very high winds, such as         keeps the turbine facing into the                    down tower is far easier than a tower
                          available wind resources, wind-elec-                              furling, pitching the blades, or stalling   wind. A few turbines on the market                   that must be climbed to perform
                          tric pumping systems can be placed                                the blades. This information, along                                                              maintenance. Tilt-down towers can            Tilt-down towers
                                                                                                                                        today are designed and tested to                                                                  are much easier
                          where the wind resource is the best                               with your local wind speed and your         International Electrotechnical                       also be lowered to the ground during         to maintain than
                          and connected to the pump motor                                   energy budget, will help you decide         Commission (IEC) Standards. These                    hazardous weather such as hurri-             guyed or free-
                          with an electric cable.                                           which size turbine will best meet your      turbines may be listed by a recog-                                                                standing towers.

                          Turbines used for residential applica-                            electricity needs.                          nized testing agency, like                                                  Tilt-Down Tower
                          tions can range in size from 600 watts                                                                        Underwriter's Laboratories (UL).
                                                                                            What are the Basic Parts                                                                                                           Tilt-up tower
                          to 100 kW (100 kW for very large                                                                                                                                                                     in the normal
                                                                                            of a Small Wind Electric                    Tower                                                                                  operating
                          loads), depending on the amount of                                                                                                                                                                   position
                                                                                            System?                                     Because wind speeds increase with                          Tilt-up tower in the
                          electricity you want to generate. For                                                                                                                                    lowered position for
                                                                                            Home wind energy systems generally          height, the turbine is mounted on a
                          residential applications, you should                                                                                                                                     maintenance or
                                                                                            comprise a rotor, a generator mounted       tower. Generally speaking, the                             hurricanes
                          establish an energy budget to help
                                                                                            on a frame, a tail (usually), a tower,      higher the tower, the more power
                          define the size of turbine you will
                                                                                            wiring, and the "balance of system"         the wind system can produce. The
                          need. Because energy efficiency is
                                                                                            components: controllers, inverters,         tower also raises the turbine above
                          usually less expensive than energy                                                                                                                                                                                     02979311m
8     Small Wind Electric Systems                                                                                                                                                                                                                                   Small Wind Electric Systems                        9

                         canes. Aluminum towers are prone to       (inverter), and wiring. Some wind tur-                                                                                                                                What Do Wind Systems
                         cracking and should be avoided. Most      bine controllers, inverters, or other                                                                                                                                 Cost?
                         turbine manufacturers provide wind        electrical devices may be stamped by                                                                                                                                  A small turbine can cost anywhere
                         energy system packages that include       a recognized testing agency, like                                                                                                                                     from $6,000 to $22,000 installed,
                         towers.                                   Underwriters Laboratories.                                                                                                                                            depending on size, application, and
                         Mounting turbines on rooftops is not      Stand-Alone Systems                                                                                                                                                   service agreements with the manufac-
                         recommended. All wind turbines            Stand-alone systems (systems not con-                                                                                                                                 turer. (AWEA says a typical home
                         vibrate and transmit the vibration to     nected to the utility grid) require bat-                                                                                                                              wind system costs approximately
                         the structure on which they are           teries to store excess power generated                                                                                                                                $32,000; a comparable photovoltaic
                         mounted. This can lead to noise and       for use when the wind is calm. They                                                                                                                                   (PV) solar system would cost over
                         structural problems with the building,    also need a charge controller to keep                                                                                                                                 $60,000.)
                         and the rooftop can cause excessive       the batteries from overcharging.                                                                                                                                      A general rule of thumb for estimating
                         turbulence that can shorten the life of   Deep-cycle batteries, such as those                                                                                                                                   the cost of a residential turbine is
                         the turbine.                              used for golf carts, can discharge and                                                                                                                                $1,000 to $3,000 per kilowatt. As a




                                                                                                                                                                                                          Southwest Windpower/PIX09156
                         Balance of System                         recharge 80% of their capacity hun-                                                                                                                                   rule, wind energy becomes more cost
                         The parts that you need in addition to    dreds of times, which makes them a                                                                                                                                    effective as the wind turbines increase
                         the turbine and the tower, or the bal-    good option for remote renewable                                                                                                                                      in diameter. Although small turbines
                         ance of system parts, will depend on      energy systems. Automotive batteries                                                                                                                                  cost less in initial outlay, they are pro-
                         your application. Most manufacturers      are shallow-cycle batteries and should                                                                                                                                portionally more expensive. The cost
                         can provide you with a system pack-       not be used in renewable energy sys-                                                   A Southwest WindPower Air 303 is the sole
                                                                                                                                                                                                                                         of a residential wind energy system
                         age that includes all the parts you       tems because of their short life in                                                    source of electricity for this remote home in                                  that comes with an 80-foot tower, bat-
                         need for your application. For exam-      deep-cycling operations.                                                               northern Arizona.                                                              teries, and inverter, typically ranges
                         ple, the parts required for water         In very small systems, direct current                                                                                                                                 from $20,000 to $40,000 for a 3 to
                                                                                                                                                          however, you must install an inverter                                          7.5 kW wind turbine.
                         pumping will be much different than       (DC) appliances operate directly off
                                                                                                                                                          to convert DC electricity to AC.
                         what you need for a residential appli-    the batteries. If you want to use stan-
                                                                                                                                                          Although the inverter slightly low-
                         cation. The balance of system required    dard appliances that use conventional
                                                                                                                                                          ers the overall efficiency of the sys-
                         will also depend on whether the sys-      household alternating current (AC),
                                                                                                                                                          tem, it allows the home to be wired
                         tem is grid-connected, stand-alone or
                                                                                                                                                          for AC, a definite plus with lenders,
                         part of a hybrid system. For a residen-
                                                                                                                                                          electrical code officials, and future
                         tial application, the balance of system
                                                                                                                                                          homebuyers.
                         parts may include a controller, storage
                         batteries, a power conditioning unit                                                                                             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.

A Bergey Excel                                                                                                                                            Grid-Connected Systems
10 kW wind turbine                                                                                                                                        In grid-connected systems, the only
is part of a gird-




                                                                                                                                                                                                                                                                                         Warren Gretz, NREL/PIX09615
connected hybrid                                                                                                                                          additional equipment required is a
                                                                                                              Trudy Forsyth, NREL/PIX09122 and PIX09123




system that reduces                                                                                                                                       power conditioning unit (inverter)
the utility power                                                                                                                                         that makes the turbine output elec-
used by this home
in Vermont. The
                                                                                                                                                          trically compatible with the utility
balance of system                                                                                                                                         grid. Usually, batteries are not
for the turbine                                                                                                                                           needed.
includes, from left                                                                                                                                                                                                                      Small wind turbines like this 10 kW Bergey
to right, an inverter,                                                                                                                                                                                                                   Excel provide electricity for home, farm, and
breaker box, and                                                                                                                                                                                                                         ranch applications.
powersync inverter.
10   Small Wind Electric Systems                                                                                                                                                            Small Wind Electric Systems                              11

                 Although wind energy systems                 and maintenance and repair require-        checked and tightened if necessary.
                                                                                                                                                                                 Wind Speeds Increase with Height
                 involve a significant initial invest-        ments, and whether the system is           The machines should be checked for




                                                                                                                                                                                                                                         02979308m
                 ment, they can be competitive with           meeting their expectations. Also, find     corrosion and the guy wires for                        150
                 conventional energy sources when             out how long the warranty lasts and        proper tension. In addition, you
                 you account for a lifetime of reduced        what it includes.                          should check for and replace any
                 or altogether avoided utility costs.                                                    worn leading edge tape on the blades,
                 The length of the payback period—the         Where Can I Find                           if appropriate. After 10 years, the                    120

                 time before the savings resulting from       Installation and                           blades or bearings may need to be
                 your system equal the cost of the sys-       Maintenance Support?                       replaced, but with proper installation




                                                                                                                                                   Tower height, ft
                 tem itself—depends on the system             The manufacturer/dealer should be          and maintenance, the machine should                          90
                 you choose, the wind resource on             able to help you install your machine.     last up to 20 years or longer.
                 your site, electricity costs in your area,   However, this is not rocket science.       If you do not have the expertise to
                 and how you use your wind system.            Many people elect to install the           maintain the machine or are afraid of                        60
                 For example, if you live in California       machines themselves. Before attempt-       heights, your installer may provide a
                 and have received the 50% buydown            ing to install your wind turbine, ask      service and maintenance program.
                 of your small wind system, have net          yourself the following questions:
                 metering and an average annual wind                                                     How Much Energy Will My                                      30
                                                              • Can I pour a proper cement
                 of 6.7 m/s, your simple payback                                                         System Generate?
                                                                foundation?
                 would be approximately 6 years.
                                                                                                         Most U.S. manufacturers rate their
                                                              • Do I have access to a lift or a way of
                 Things to Consider When                                                                 turbines by the amount of power they                          0
                                                                erecting the tower safely?                                                                                                        0           41        75   100   124
                 Purchasing a Wind Turbine                                                               can safely produce at a particular
                                                                                                                                                                                                      Increase in wind power, %
                 Once you decide you can legally              • Do I know the difference between         wind speed, usually chosen between
                 install a wind energy system without           AC and DC wiring?                        24 mph (10.5 m/s) and 36 mph (16
                 alienating your neighbors, you can           • Do I know enough about electricity       m/s). The formula for calculating the     shown in the Wind Speed Increase
                 begin pricing systems and compo-               to safely wire my machine?               power from a wind turbine is:             with Height graph.
                 nents. Comparatively shop for a wind         • Do I know how to safely handle                 Power = Cp 1/2 ρ A V3               The rotor swept area, A, is important
                 system as you would any major pur-             and install batteries?                                                             because the rotor is the part of the
                                                                                                         Where:
                 chase. Obtain and review the product                                                                                              turbine that captures the wind energy.
                 literature from several manufacturers.       If your answer to any of the above         Cp = Power coefficient, ranging           So, the larger the rotor, the more
                 As mentioned earlier, lists of manu-         questions is no, you should probably            from 0.2–0.4, dimensionless          energy it can capture. The air density,
                 facturers are available from the             choose to have your system installed            (theoretical max = 0.59)             ρ, changes slightly with air tempera-
                 American Wind Energy Association             by a system integrator or installer.                                                 ture and with elevation. The ratings
                                                                                                         ρ    = Air density, lb/ft3
                 (AWEA, see reference list), but not all      Contact the manufacturer for help or                                                 for wind turbines are based on
                 small turbine manufacturers are mem-         call your state energy office and local    A    = Rotor swept area, or π D2/4
                 bers of AWEA. Check the Yellow               utility for a list of local system                (D is the rotor diameter in ft,
                 Pages for wind energy system dealers         installers. You can also check the yel-           π = 3.1416)                                                       Air Density Change with Elevation
                                                                                                                                                                      10,000
                 in your area.                                low pages for wind energy system           V    = Wind speed, mph                                        9,000
                                                              service providers. A credible installer
                 Once you have narrowed the field,            will provide many services, permits,       This formula illustrates factors that                         8,000
                 research a few companies to be sure          etc. Find out if the installer is a        are important to the performance of a                         7,000




                                                                                                                                                    Elevation, ft
                 they are recognized wind energy busi-        licensed electrician. Ask for references   wind turbine. Notice that the wind                            6,000
                 nesses and that parts and service will       and check them out. And be sure to         speed, V, has an exponent of 3 applied                        5,000
                 be available when you need them.             check with the Better Business             to it. This means that even a small                           4,000
                 Call the Better Business Bureau to           Bureau.                                    increase in wind speed results in a                           3,000
                 check on the company's integrity and                                                    large increase in power. That is why a




                                                                                                                                                                                                                                                     02979302m
                                                                                                                                                                       2,000
                 ask for references of past customers         Although small wind turbines are           taller tower will increase the produc-                        1,000
                 with installations similar to the one        tough little machines, they do require     tivity of any wind turbine by giving it                           0
                 you are considering. Ask the system          some annual maintenance. Bolts and         access to higher wind speeds as                                    70      75       80          85        90        95      100

                 owners about performance, reliability,       electrical connections should be                                                                                     Density change compared to sea level, %
12   Small Wind Electric Systems   Small Wind Electric Systems   13
14   Small Wind Electric Systems                                                                                                                                              Small Wind Electric Systems            15

                 standard conditions of 59° F (15° C) at   way to determine whether a particu-                                                                                                     The farther you
                 sea level. A density correction should    lar wind turbine and tower will pro-                                                                                                    place your wind
                                                                                                                                                                                                   turbine from
                 be made for higher elevations as          duce enough electricity to meet your                Obstruction of the Wind by a Buildin
                                                                                                                                                                                                   obstacles such
                 shown in the Air Density Change with      needs.                                                                                                                                  as buildings or
                 Elevation graph. A correction for tem-    A wind turbine manufacturer can help                                                                                                    trees, the less
                 perature is typically not needed for                                                                                                                                              turbulence you
                                                           you estimate the energy production                                                                                                      will encounter.
                 predicting the long-term performance      you can expect. They will use a calcu-        Prevailing wind
                 of a wind turbine.                        lation based on the particular wind                                            Region




                                                                                                                                                                                       02979307m
                                                                                                                                         of highly
                 While the calculation of wind power       turbine power curve, the average                                              disturbed
                                                                                                                                                          2H
                 illustrates important features about      annual wind speed at your site, the                                  H           flow
                 wind turbines, the best measure of        height of the tower that you plan to
                 wind turbine performance is annual        use, and the frequency distribution of              2H                                           20 H
                 energy output. The difference             the wind–an estimate of the number
                 between power and energy is that          of hours that the wind will blow at
                 power (kilowatts [kW]) is the rate at     each speed during an average year.        To get a preliminary estimate of the             needs to be sited upwind of buildings
                 which electricity is consumed, while      They should also adjust this calcula-     performance of a particular wind tur-            and trees, and it needs to be 30 feet
                 energy (kilowatt-hours [kWh]) is the      tion for the elevation of your site.      bine, use the formula below.                     above anything within 300 feet. You
                 quantity consumed. An estimate of         Contact a wind turbine manufacturer                AEO = 0.01328 D2 V3                     also need enough room to raise and
                 the annual energy output from your        or dealer for assistance with this cal-                                                    lower the tower for maintenance, and
                                                                                                     Where:                                           if your tower is guyed, you must
                 wind turbine, kWh/year, is the best       culation.
                                                                                                     AEO = Annual energy output,                      allow room for the guy wires.
                                                                                                           kWh/year                                   Whether the system is stand-alone or
                                                                                                     D    = Rotor diameter, feet                      grid-connected, you will also need to
                                                                                                                                                      take the length of the wire run into
                                                                                                     V    = Annual average wind speed,
                                                                                                                                                      consideration. A substantial amount
                                                                                                            mph
                                                                                                                                                      of electricity can be lost as a result of
                                                                                                     How Do I Choose the Best                         the wire resistance—the longer the
                                                                                                     Site for My Wind Turbine?                        wire run, the more electricity is lost.
                                                                                                                                                      Using more or larger wire will also
                                                                                                     You can have varied wind resources
                                                                                                                                                      increase your installation cost. Your
                                                                                                     within the same property. In addition
                                                                                                                                                      wire runs losses are greater when you
                                                                                                     to measuring or finding out about the
                                                                                                                                                      have direct current (DC) instead of
                                                                                                     annual wind speeds, you need to
                                                                                                                                                      alternating current (AC) so if you
                                                Spreed sheet info                                    know about the prevailing directions
                                                                                                                                                      have a long wire run it is advisable to
                                                                                                     of the wind at your site. If you live in
                                                                                                                                                      invert DC to AC.
                                                                                                     complex terrain, take care in selecting
                                                                                                     the installation site. If you site your          Can I Connect My System
                                                                                                     wind turbine on the top of or on the             to the Utility Grid?
                                                                                                     windy side of a hill, for example, you
                                                                                                                                                      Small wind energy systems can be
                                                                                                     will have more access to prevailing
                                                                                                                                                      used in connection with an electricity
                                                                                                     winds than in a gully or on the lee-
                                                                                                                                                      distribution system and are called
                                                                                                     ward (sheltered) side of a hill on the
                                                                                                                                                      grid-connected systems. A grid-con-
                                                                                                     same property. In addition to geologic
                                                                                                                                                      nected wind turbine can reduce your
                                                                                                     formations, you need to consider
                                                                                                                                                      consumption of utility-supplied elec-
                                                                                                     existing obstacles such as trees,
                                                                                                                                                      tricity for lighting, appliances, and
                                                                                                     houses, and sheds, and you need to
                                                                                                                                                      electric heat. If the turbine cannot
                                                                                                     plan for future obstructions such as
                                                                                                                                                      deliver the amount of energy you
                                                                                                     new buildings or trees that have not
                                                                                                                                                      need, the utility makes up the differ-
                                                                                                     reached their full height. Your turbine
                                                                                                                                                      ence. When the wind system produces
16       Small Wind Electric Systems                                                                                                                                                   Small Wind Electric Systems   17

     A grid-connected                                                                                              metering rules allow for annual NEG,        any electricity to its power lines dur-
                                                      Grid-connected Systems
     wind turbine can                                                                                              the NEG credit can be carried for up        ing an outage. Otherwise line workers
     reduce your
                                                                                                                   to a year.                                  and the public, thinking that the line
     consumption of                                                                 Meter
     utility-supplied                                                                                              Most of North America gets more             is "dead," might not take normal pre-
     electricity.
                                                                                                                   wind in the winter than in the sum-         cautions and might be hurt or even
                                                                             AC                                                                                killed by the power from your tur-
                                                                                                                   mer. For people using wind energy to
                                                                  Inverter
                                                                                                                   displace a large load in the summer         bine. Another concern among utilities
                                                                                             Load                  like air-conditioning or irrigation         is that the power from your facility
                                             Wind
                                            turbine                                                                water pumping, having an annual             synchronize properly with the utility




                                                                                                       02979301m
                                                                                                                   NEG credit allows them to produce           grid, and that it match the utility’s
                                                                                                                   NEG in the winter and be credited in        own power in terms of voltage, fre-
                                                                                                                   the summer.                                 quency, and power quality.
                                                                                                                                                               A few years ago, some state govern-
                                                                                                                   Safety Requirements
                        more electricity than the household            ments. The following information                                                        ments started developing new stan-
                                                                                                                   Whether or not your wind turbine is         dardized interconnection
                        requires, the excess is sent or sold to        about utility grid connection require-      connected to the utility grid, the
                        the utility.                                   ments was taken from AWEA's Web                                                         requirements for small renewable
                                                                                                                   installation and operation of the wind      energy generating facilities (including
                        Grid-connected systems can be practi-          site. For more detailed information,        turbine is probably subject to the elec-
                                                                       visit http://www.awea.org/ or con-                                                      wind turbines). In most cases the new
                        cal if the following conditions exist:                                                     trical codes that your local govern-        requirements have been based on con-
                                                                       tact AWEA (see For More                     ment (city or county) or in some
                        • You live in an area with average             Information).                                                                           sensus-based standards and testing
                          annual wind speed of at least 10                                                         instances your state government has         procedures developed by independ-
                          miles per hour (4.5 meter per                Net Metering                                in place. The government’s principal        ent third-party authorities, such as the
                          second).                                     The concept of net metering programs        concern is with the safety of the facil-    Institute of Electrical and Electronic
                                                                       is to allow the electric meters of cus-     ity, so these code requirements             Engineers and Underwriters
                        • Utility-supplied electricity is                                                          emphasize proper wiring and installa-
                                                                       tomers with generating facilities to                                                    Laboratories.
                          expensive in your area (about 10 to                                                      tion, and the use of components that
                          15 cents per kilowatt-hour).                 turn backwards when their generators
                                                                                                                   have been certified for fire and electri-   Interconnection Requirements
                                                                       are producing more energy than the
                        • The utility's requirements for               customers’ demand. Net metering             cal safety by approved testing labora-      Most utilities and other electricity
                          connecting your system to its grid           allows customers to use their genera-       tories, such as Underwriters                providers require you to enter into a
                          are not prohibitively expensive.             tion to offset their consumption over       Laboratories. Most local electrical         formal agreement with them before
                                                                       the entire billing period, not just         codes requirements are based on the         you interconnect your wind turbine
                        • There are good incentives for the
                                                                       instantaneously. This offset would          National Electrical Code (NEC),             with the utility grid. In states that
                          sale of excess electricity or for the
                                                                       enable customers with generating            which is published by the National          have retail competition for electricity
                          purchase of wind turbines.
                                                                       facilities to receive retail prices for     Fire Protection Association. As of          service (e.g., your utility operates the
                        Federal regulations (specifically, the                                                     1999, the latest version of the NEC did     local wires, but you have a choice of
                                                                       more of the electricity they generate.
                        Public Utility Regulatory Policies Act                                                     not have any sections specific to the       electricity provider) you may have to
                        of 1978, or PURPA) require utilities to        Net metering varies by state and by         installation of wind energy facilities,     sign a separate agreement with each
                        connect with and purchase power                utility company, depending on               consequently wind energy installa-          company. Usually these agreements
                        from small (less than 80 MW) wind              whether net metering was legislated         tions are governed by the generic pro-      are written by the utility or the elec-
                        energy systems. However, you should            or directed by the Public Utility           visions of the NEC.                         tricity provider. In the case of private
                        contact your utility before connecting         Commission. Net metering programs                                                       (investor-owned) utilities, the terms
                                                                       all specify a way to handle the net         If your wind turbine is connected to
                        to their distribution lines to address                                                                                                 and conditions in these agreements
                                                                       excess generation (NEG) in terms of         the local utility grid so that any of the
                        any power quality and safety con-                                                                                                      must be reviewed and approved by
                                                                       payment for electricity and/or length       power produced by your wind tur-
                        cerns. Your utility can provide you                                                                                                    state regulatory authorities.
                                                                       of time allowed for NEG credit. If the      bine is delivered to the grid, then your
                        with a list of requirements for con-
                                                                       net metering requirements define            utility also has legitimate concerns        Insurance
                        necting your system to the grid. The
                                                                       NEG on a monthly basis, the con-            about safety and power quality that         Some utilities require small wind tur-
                        American Wind Energy Association is
                                                                       sumer can only get credit for their         need to be addressed. The utility’s         bine owners to maintain liability
                        another good source for information
                                                                       excess that month. But if the net           principal concern is that your wind         insurance in amounts of $1 million or
                        on utility interconnection require-
                                                                                                                   turbine automatically stops delivering      more. Utilities argue these require-
18     Small Wind Electric Systems                                                                                                                                                                                       Small Wind Electric Systems              19

                         ments are necessary to protect them                                   excessive, you may want to protest                                          Hybrid Power Systems                                               A hybrid system
                         from liability for facilities they do not                             these requirements to regulatory                        Combine multiple sources to deliver non-intermittent electric power                    that combines a
                                                                                                                                                                                                                                              wind system with
                         own and have no control over. Others                                  authorities (in the case of private                                                                                                            a solar and/or
                         argue that the insurance requirements                                 investor-owned utilities) or to the util-                                                                                                      diesel generator
                         are excessive and unduly burden-                                      ity’s governing board (in the case of                                                                                                          can provide
                                                                                                                                                                                                                                              reliable off-grid
                         some, making wind energy uneco-                                       publicly-owned utilities).                                                    PV modules                                                       power around the
                         nomic. In the 21 years since utilities                                                                                                                                                                               clock.
                                                                                               Indemnification
                         have been required to allow small
                         wind systems to interconnect with the                                 An indemnity is an agreement                                                                                     Generator
                         grid there has never been a liability                                 between two parties where one agrees
                         claim, let alone a monetary award,                                    to secure the other against loss or
                         relating to electrical safety.                                        damage arising from some act or                                                                            AC or          Load
                                                                                               some assumed responsibility. In the                                                    Regulation and       DC
                         In six states (California, Maryland,                                  context of customer-owned generat-                                                      conversion




                                                                                                                                                                                                                                  02979301m
                         Nevada, Oklahoma, Oregon, and                                         ing facilities, utilities often want cus-                        Wind
                         Washington), laws or regulatory                                       tomers to indemnify them for any                                turbine
                         authorities prohibit utilities from                                   potential liability arising from the
                         imposing any insurance requirements                                                                                                                           Battery bank
                                                                                               operation of the customer’s generat-
                         on small wind systems that qualify for                                ing facility. Although the basic princi-
                         "net metering." In at least three other                               ple is sound—utilities should not be        Customer Charges                                 there is less sunlight available.
                         states (Idaho, New York, Virginia) reg-                               held responsible for property damage                                                         Because the peak operating times for
                                                                                                                                           Customer charges can take a variety
                         ulatory authorities have allowed utili-                               or personal injury attributable to                                                           wind and PV occur at different times
                                                                                                                                           of forms, including interconnection
                         ties to impose insurance requirements,                                someone else—indemnity provisions                                                            of the day and year, hybrid systems
                                                                                                                                           charges, metering charges, and
                         but have reduced the required cover-                                  should not favor the utility but should                                                      are more likely to produce power
                                                                                                                                           standby charges, among others. You
 A grid-connected        age amounts to levels consistent with                                 be fair to both parties. Look for lan-                                                       when you need it. (For more informa-
                                                                                                                                           should not hesitate to question any
 wind turbine can        conventional residential or commer-                                   guage that says, "each party shall                                                           tion on solar electric or PV systems,
 reduce your                                                                                                                               charges that seem inappropriate to
                         cial insurance policies (e.g., $100,000                               indemnify the other . . ." rather than                                                       contact the Energy Efficiency and
 consumption of                                                                                                                            you. Federal law (Public Utility
 utility-supplied        to $300,000). If your utility requires                                "the customer shall indemnify the                                                            Renewable Energy Clearinghouse—
                                                                                                                                           Regulatory Policies Act of 1978, or
 electricity for         insurance amounts that seem                                           utility . . ."                                                                               see For More Information.)
 lighting, appliances,                                                                                                                     PURPA, Section 210) prohibits utili-
 and electric heat.                                                                                                                        ties from assessing discriminatory               For the times when neither the wind
                                                                                                                                           charges to customers who have their              nor the PV modules are producing,
                                                                                  Connecting to the Utility Grid—                          own generation facilities.                       most hybrid systems provide power
                                                                                  A Success Story
                                                                                                                                                                                            through batteries and/or an engine-
                                                                                  This 10-kW Bergey wind turbine, installed on a           Can I Go "Off-Grid"?                             generator powered by fossil fuels. If
                                                                                  farm located in Southwestern Kansas in 1978,             Hybrid Systems                                   the batteries run low, the engine-gen-
                                                                                  produces an average 1700–1800 kilowatt-hours                                                              erator can provide power and
                                                                                                                                           Off-grid hybrid wind energy systems
                                                                                  per month, reducing the user's monthly utility                                                            recharge the batteries. Adding a fos-
                                                                                                                                           can be appropriate for homes, farms
                                                                                  bills by approximately 50%. The turbine cost                                                              sil-fuel-powered generator makes the
                                                                                                                                           or even entire communities (a co-
                                                                                  about $20,000 when it was installed and, since                                                            system more complex, but modern
                                                                                                                                           housing project, for example) that are
                                                                                  then the cost for operation and maintenance has                                                           electronic controllers can operate
                                                                                                                                           far from the nearest utility lines.
                                                                                  been about $50 per year. The only unscheduled                                                             these systems automatically. Adding
                                                                                                                                           According to many renewable energy
                                                                                  maintenance activity over the years was repair to                                                         an engine-generator can also reduce
                                                                                                                                           experts, a "hybrid" system that com-
                                                                                  the turbine required as a result of damage caused                                                         the size of the other components
                                                                                                                                           bines wind and photovoltaic (PV)
                                                                                  by a lightning strike. Insurance covered all but                                                          needed for the system. Keep in mind
                                                                                                                                           technologies offers several advan-
                                                                                  $500 of the $9000 cost of damages. The basic sys-
                                                    Warren Gretz, NREL/PIX09634




                                                                                                                                           tages over either single system. In              that the storage capacity must be
                                                                                  tem parts include:                                                                                        large enough to supply electrical
                                                                                                                                           much of the United States, wind
                                                                                  Bergey XL.10 wind turbine                                speeds are low in the summer when                needs during non-charging periods.
                                                                                  100-foot free-standing lattice tower                     the sun shines brightest and longest.            Battery banks are typically sized to
                                                                                  Inverter                                                 The wind is strong in the winter when
20     Small Wind Electric Systems                                                                                                                                                                      Small Wind Electric Systems   21

                        supply the electric load for one to                                   running a power line to a remote        Glossary of Terms                          kWh—Kilowatt-hour, a measure of
                        three days.                                                           site to connect with the utility grid   Airfoil—The shape of the blade cross-      energy equal to the use of one kilo-
                        An off-grid hybrid system may be                                      can be prohibitive, ranging from        section, which for most modern hori-       watt in one hour.
                        practical for you if:                                                 $15,000 to more than $50,000 per        zontal axis wind turbines, is designed     MW—Megawatt, a measure of power
                                                                                              mile, depending on terrain.             to enhance the lift and improve tur-       (1,000,000 watts).
                        • You live in an area with average
                                                                                           • You would like to gain energy            bine performance.
                          annual wind speed of at least 9                                                                                                                        Nacelle—The body of a propeller-type
                          miles per hour (4.0 meters per                                     independence from the utility.           Anemometer—Device to measure the           wind turbine, contains the gearbox,
                          second).                                                         • You would like to reduce the             wind speed.                                generator, blade hub and other parts.
                        • A grid connection is not available                                 environmental impact of electricity      Average wind speed—The mean wind           O&M Costs—Operation and mainte-
                          or can only be made through an                                     production.                              speed over a specified period of time.     nance costs.
                          expensive extension. The cost of                                                                            Blades—The aerodynamic surface that        Power Coefficient The ratio of the
                                                                                                                                      catches the wind.                          power extracted by a wind turbine to
                                                                                                                                      Brake—Various systems used to stop         the power available in the wind
                                                                                                                                      the rotor from turning.                    stream.
                                                                                                                                      Converter—See Inverter.                    Power curve—Chart of a wind tur-
                                                                                                                                                                                 bine's power output across a range of
                                                                                                                                      Cut-in wind speed—Wind speed at            wind speeds.
                                                                                                                                      which a wind turbine begins to gener-
                          Living Off-Grid—A Success Story                                                                             ate electricity.                           PUC—Public Utility Commission,
                          This home, built near in Ward, Colorado (at an elevation of 9000 feet), has                                                                            state agency which regulates utilities.
                                                                                                                                      Cut-out wind speed—Wind speed at           In some areas known as Public Service
                          been off-grid since it was built in 1972. When the house was built, the near-
 Electricity for this                                                                                                                 which a wind turbine ceases to gener-      Commission (PSC).
                          est utility was over a mile away, and it would have cost between $60K–$70K
 off-grid home near                                                                                                                   ate electricity.
 Ward, Colorado,          (based on 1985 rates) to connect to the utility lines. The owners decided to                                                                           PURPA Public Utility Regulatory
 is provided by a         install a hybrid electric system powered by wind, solar, and a generator for a                              Density—Mass per unit of volume.           Policies Act (1978), 16 U.S.C. § 2601.18
 wind/PV/diesel           cost of about $19,700. The parts of the system include:                                                     Downwind—On the opposite side              CFR §292 refers to small generator.
 hybrid system.
                                                                           Bergey 1.5 kW wind turbine, 10-ft (3-m) diameter           from the direction for which the wind      Rated output capacity—The output
                                                                           rotor, 70-ft. (21-m) tower                                 is blowing.                                power of a wind machine operating at
                                                                           Solarex PV panels, 480 watts                               Furling—A passive protection for the       the rated wind speed.
                                                                                                                                      turbine where most typically the rotor     Rated wind speed—The lowest wind
                                                                           24 VDC battery bank, 375 Ah
                                                                                                                                      folds either up or around the tail vane.   speed at which the rated output
                                                                           Trace sine wave inverter, 120 VAC, 1 phase, 4 kW
                                                                                                                                      Green energy—Energy produced by            power of a wind turbine is produced.
                                                                           Onan propane-fueled generator, 6.5 kW rated (3 kW          non-polluting methods, such as wind,       Rotor—The rotating part of a wind
                                                                           derated for altitude)                                      solar, hydro, or geothermal energy.        turbine, including either the blades
                                                                           The Bergey wind turbine listed above is the fourth         Grid—Utility distribution system.          and blade assembly or the rotating
                                                                           used turbine to be purchased for this system as a          The network that connects electricity      portion of a generator.
                                                                           result of the extreme winds at this site.                  generators to electricity users.           Rotor diameter—The diameter of the
                                                                           Electric appliances in the home include television,        HAWT—Horizontal Axis Wind                  circle swept by the rotor.
                                                                           stereo, two computers, toaster, blender, vacuum            Turbine.                                   Rotor speed—Revolutions per minute
                                                                           cleaner, and hair dryer. The largest electric loads are
                                                                                                                                      Inverter—Device which converts             of the wind turbine rotor.
                                                                           created by a well pump and washing machine. The
                                                                                                                                      direct current (DC) to alternating         Start-up wind speed—Wind speed at
                                                                           generator runs about 20% of the time, particularly
                                                                                                                                      current (AC).                              which a wind turbine rotor will begin
                                                                           when the washing machine is in use. Propane
                                                Jim Green, NREL/PIX02796




                                                                           serves the other major loads in the home: range,           kW—Kilowatt, a measure of power for        to spin. See also cut-in wind speed
                                                                           refrigerator, hot water, and space heat. Solar collec-     electrical current (1000 watts).           Swept area—Area swept by the tur-
                                                                           tors on the roof provide pre-heating for the hot                                                      bine rotor, A = πR2, where R is the
                                                                           water.                                                                                                radius of the rotor.
22   Small Wind Electric Systems                                                                                                                                     Small Wind Electric Systems   23

                 Tip speed ratio—Speed at the tip of       Wind Energy Resource Atlas of the          Non-Government Organizations             Information on Home-Built Small
                 the rotor blade as it moves through       United States by D. Elliott et al.         American Wind Energy Association,        Wind Turbines—http://www.
                 the air divided by the wind velocity.     Available from the American Wind           122 C Street, N.W. 4th Floor,            picoturbine.com
                 This is typically a design requirement    Energy Association, 122 C. Street          Washington, D.C. 20001. (202)383-        Small Wind "Talk" on the Web—
                 for the turbine.                          N.W., Washington D.C. 20001.               2500. www.awea.org                       AWEA's Home Energy Systems elec-
                 Turbulence—Changes in wind speed          http://rredc.nrel.gov/wind/pubs/                                                    tronic mailing list is designed as a
                                                                                                      Solar Energy International—Short
                 and direction, frequently caused by       atlas                                                                               forum for the discussion of small-scale
                                                                                                      courses on renewable energy and sus-
                 obstacles.                                Wind Power for Home and Business by        tainable development, in Carbondale,     energy systems that include wind. To
                 Upwind—On the same side as the            Paul Gipe—A comprehensive guide to         Colorado. (970) 963-8855.                subscribe, send a subscription request
                 direction from which the wind is          modern small wind technology.              http://www.solarenergy.org.              awea-wind-home-subscribe@
                 blowing—windward.                         Available through AWEA. (202) 383-                                                  egroups.com.
                                                           2500. http://awea.org Chelsea Green        Periodicals
                 VAWT—Vertical Axis Wind Turbine.                                                                                              Wind Energy for Homeowners—This
                                                           Publishing Company, White River            "Apples and Oranges" by Mick
                                                                                                                                               Web site discusses things you should
                 Wind farm—A group of wind tur-            Junction, Vermont. 1999. ISBN -            Sagrillo—A comprehensive compari-
                                                                                                                                               consider before investing in a small
                 bines, often owned and maintained by      0-930031-64-4.                             son of available small wind turbines.
                                                                                                                                               wind energy system and provides
                 one company. Also known as a wind                                                    On Home Power Magazine Web site:
                                                           Wind Resource Assessment Handbook:                                                  basic information about the systems.
                 power plant.                                                                         http://www.homepower.com
                                                           Fundamentals for Conducting a                                                       http://www.eren.doe.gov/wind/
                 Yaw—The movement of the tower top         Successful Monitoring Program—This         Home Power Magazine—The defini-          homeowner.html
                 turbine that allows the turbine to stay   handbook presents industry-accepted        tive bimonthly magazine for the
                 into the wind.                            guidelines for planning and conduct-       homemade power enthusiast.
                                                           ing a wind resource measurement            (800)707-6586 or on the Web at:
                 For More Information                      program. These guidelines, which are       http://www.homepower.com
                 Books                                     detailed and highly technical, empha-
                                                                                                      Videos
                                                           size the tasks of selecting, installing,
                 A Siting Handbook for Small Wind                                                     An Introduction to Residential Wind
                                                           and operating wind measurement
                 Energy Conversion Systems. H. Wegley,                                                Systems with Mick Sagrillo—A 63-
                                                           equipment, as well as collecting and
                 J. Ramsdell, M. Orgill and R. Drake,                                                 minute video answering questions
                                                           analyzing the associated data.
                 Report No. PNL-2521 Rev.1, 1980;                                                     most often asked by homeowners
                                                           Prepared by AWS Scientific, Inc.,
                 available from National Technical                                                    as they consider purchasing and
                                                           3 Washington Square, Albany, NY
                 Information Service, 5285 Port Royal                                                 installing their own wind power
                                                           12205.
                 Rd., Springfield, VA 22151)                                                          systems. Order from AWEA (202) 383-
                 Energy Savers Tips on Saving Energy       Government Agencies                        2500, http://www.awea.org
                 and Money at Home—A consumer's            Energy Efficiency and Renewable
                                                                                                      Web Sites
                 guide for saving energy and reducing      Energy Clearinghouse, P.O. Box 3048,
                                                           Merrifield, Virginia 22116 800-DOE-        AWEA Small Wind Systems Web
                 utility bills. Available from U.S.
                                                           EREC (363-3732).                           site—Includes answers to frequently
                 Department of Energy's Energy
                                                                                                      asked questions and information on
                 Efficiency and Renewable Energy           National Climatic Data Center,             U.S. manufacturers. http://www.
                 Clearinghouse (EREC), P.O. Box 3048,      Federal Building, 151 Patton Avenue,       awea.org/smallwind.html
                 Merrifield, Virginia 22116. (800)         Asheville, North Carolina, 28801-5001.
                 363-3732. www.eren.doe.gov/               (828) 271-4800. Fax (828) 271-4876.        Database of State Incentives for
                 consumerinfo/energy_savers.               http://www.ncdc.noaa.gov                   Renewable Energy—On the Web at
                                                                                                      http://www.dcs.ncsu.edu/solar/
                 Wind Energy Basics by Paul Gipe—A         U.S. Department of Commerce,               dsire/dsire.html
                 comprehensive guide to modern small       National Technical Information
                 wind technology. Available through        Service, 5285 Port Royal Road,             Green Power Network Net Metering
                 AWEA. (202) 383-2500.                     Springfield, Virginia 22161. (800)         Web Site—Net metering programs are
                 http://awea.org and Chelsea Green         553-6847. http://www.ntis.gov/             now available in 30 states. Visit this
                 Publishing Company, White River           ordering.htm                               DOE Web site for information:
                 Junction, Vermont. 1999. ISBN                                                        http://www.eren.doe.gov/
                 1-890132-07-01.                                                                      greenpower/netmetering
24   Small Wind Electric Systems

				
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