Guide to Using Small Wind Turbines for Home Energy

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


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

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

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

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

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

Location—A cabin in South Park, Colorado
Capacity—600 watt
Turbine manufacturer—Southwest WindPower
Photo credit—E. McKenna, NREL/PIX04712

Small Wind Electric Systems 1

A U.S. Consumer’s Guide

Introduction
Can I use wind energy to power my
home? This question is being asked
across the country as more people
look for affordable and reliable sourc-
es of electricity.
Small wind electric systems can make
a significant contribution to our
nation’s energy needs. Although wind
turbines large enough to provide a
significant portion of the electricity
needed by the average U.S. home gen-
erally require one acre of property or
more, approximately 21 million U.S.
homes are built on one-acre and larger

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

2 Small Wind Electric Systems

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

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


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

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


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

decide which size turbine will best
meet your electricity needs.


What are the Basic Parts
of a Small Wind Electric
System?
��
Home wind energy systems gener-
ally comprise a rotor, a generator or ��
alternator mounted on a frame, a tail ��

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


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

A Bergey XL.10,
10-kW wind
turbine is part of
a grid-connected
wind/photovoltaic
hybrid system that
reduces the utility
power used by this
home in Vermont.
Trudy Forsyth, NREL/PIX09122 and PIX09123

The balance of
system (upper right)
includes from left
to right, a Trace
inverter for the
PV system, a
breaker box, and a
Powersync inverter
for the wind system.


Small wind turbines generate direct A Southwest
current (DC) electricity. In very small Windpower Air
303, 300-watt
systems, DC appliances operate turbine is the sole
directly off the batteries. If you want to source of electricity
use standard appliances that use con- for this remote
home in northern
ventional household alternating cur- Arizona.
rent (AC), you must install an inverter
to convert DC electricity from the
batteries to AC. Although the inverter
slightly lowers the overall efficiency
of the system, it allows the home to
be wired for AC, a definite plus with
lenders, electrical code officials, and
future homebuyers.

Southwest Windpower/PIX09156
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.
increases. Although small turbines
Grid-Connected Systems cost less in initial outlay, they are
In grid-connected systems, the only proportionally more expensive. The
additional equipment required is a cost of an installed residential wind
power conditioning unit (inverter) energy system with an 80-foot tower,
that makes the turbine output electri- batteries, and inverter typically
cally compatible with the utility grid. ranges from $15,000 to $50,000 for
Usually, batteries are not needed. a 3- to 10-kW wind turbine.
Although wind energy systems
What Do Wind Systems involve a significant initial invest-
Cost? ment, they can be competitive with
Installation costs vary greatly depend- conventional energy sources when
ing on local zoning, permitting, and you account for a lifetime of reduced
utility interconnection costs. A small or avoided utility costs. The length
turbine can cost anywhere from $3,000 of the payback period—the time
to $50,000 installed, depending on before the savings resulting from your
size, application, and service agree- system equal the cost of the system
ments with the manufacturer. (The itself—depends on the system you
American Wind Energy Association choose, the wind resource on your
[AWEA] says a typical home wind site, electricity costs in your area, and
system costs approximately $32,000 how you use your wind system. For
(10 kW); a comparable photovoltaic example, if you live in California and
[PV] solar system would cost over have received the 50% buydown of
$80,000.) your small wind system, have net
A general rule of thumb for estimat- metering, and an average annual
ing the cost of a residential turbine is wind speed of 15 miles per hour
$1,000 to $5,000 per kilowatt. Wind (mph) (6.7 meters per second [m/
energy becomes more cost effective s]), your simple payback would be
as the size of the turbine’s rotor approximately 6 years.


references of past customers with
installations similar to the one you are
considering. Ask the system owners
about performance, reliability, and
maintenance and repair requirements,
and whether the system is meeting
their expectations. Also, find out how
long the warranty lasts and what it
includes.

Where Can I Find
Installation and
Maintenance Support?
The manufacturer/dealer should be
able to help you install your machine.
Many people elect to install the
machines themselves. Before attempt-
ing to install your wind turbine, ask
Warren Gretz, NREL/PIX09615

yourself the following questions:
• Can I pour a proper cement
foundation?
• Do I have access to a lift or a way of
erecting the tower safely?
Small wind
turbines like this Things to Consider When • Do I know the difference between
10-kW Bergey Purchasing a Wind Turbine AC and DC wiring?
XL.10 provide
electricity for Once you determine you can install • Do I know enough about electricity
home, farm, and a wind energy system in compliance
ranch applications.
to safely wire my turbine?
with local land use requirements, you
can begin pricing systems and compo- • Do I know how to safely handle
nents. Comparatively shop for a wind and install batteries?
system as you would any major pur- If you answered no to any of the
chase. Obtain and review the product above questions, you should probably
literature from several manufacturers. choose to have your system installed
As mentioned earlier, lists of manu- by a system integrator or installer.
facturers are available from AWEA, Contact the manufacturer for help
(see For More Information), but not or call your state energy office and
all small turbine manufacturers are local utility for a list of local system
members of AWEA. Check the yellow installers. You can also check the yel-
pages for wind energy system dealers low pages for wind energy system
in your area. service providers. A credible installer
Once you have narrowed the field, will provide many services such as
research a few companies to be sure permitting. Find out if the installer is a
they are recognized wind energy licensed electrician. Ask for references
businesses and that parts and service and check them out. You may also
will be available when you need them. want to check with the Better Business
You may wish to contact the Better Bureau.
Business Bureau to check on Although small wind turbines are
the company’s integrity and ask for very sturdy machines, they do require


some annual maintenance. Bolts wind speed results in a large increase
and electrical connections should be in power. That is why a taller tower
checked and tightened if necessary. will increase the productivity of any
The machines should be checked for wind turbine by giving it access to
corrosion and the guy wires for higher wind speeds as shown in the
proper tension. In addition, you Wind Speeds Increase with Height
should check for and replace any graph. The formula for calculating
worn leading edge tape on the blades, the power from a wind turbine is:
if appropriate. After 10 years, the Power = k Cp 1/2 ρ A V3
blades or bearings may need to be
replaced, but with proper installation Where:
and maintenance, the machine should P = Power output, kilowatts
last up to 20 years or longer. Cp = Maximum power coefficient,
If you do not have the expertise to ranging from 0.25 to 0.45,
maintain the machine, your installer dimension less (theoretical
maximum = 0.59)
may provide a service and mainte-
nance program. ρ = Air density, lb/ft3
A = Rotor swept area, ft2 or
How Much Energy Will My π D2/4 (D is the rotor
System Generate? diameter in ft, π = 3.1416)
Most U.S. manufacturers rate their V = Wind speed, mph
turbines by the amount of power they k = 0.000133 A constant to yield
can safely produce at a particular power in kilowatts. (Multiplying
wind speed, usually chosen between the above kilowatt answer by
24 mph (10.5 m/s) and 36 mph (16 m/ 1.340 converts it to horse-
s). The following formula power [i.e., 1 kW = 1.340
illustrates factors that are important horsepower]).
to the performance of a wind turbine. The rotor swept area, A, is important
Notice that the wind speed, V, has an because the rotor is the part of the
exponent of 3 applied to it. This turbine that captures the wind energy.
means that even a small increase in

Relative Size of Small Wind Turbines
40
8

30
Swept area, m2

7
7m
6 20
6m
Rotor Diameter, m

5 10
5m
4 0
4m 1 2 3 4 5 6 7
Rotor Diameter, m
3
3m
2
2m
02979303m

1
1m
0
Source: Paul Gipe, Wind Energy Basics


Air Density Change with Elevation height of the tower that you plan to
10,000 use, and the frequency distribution of
9,000 the wind–an estimate of the number
8,000 of hours that the wind will blow at
7,000 each speed during an average year.
Elevation, ft

6,000 They should also adjust this calcula-
5,000 tion for the elevation of your site.
4,000 Contact a wind turbine manufacturer
3,000 or dealer for assistance with this
2,000 calculation.

02979302m
1,000 To get a preliminary estimate of the
0
70 75 80 85 90 95 100
performance of a particular wind tur-
Density change compared to sea level, % bine, use the formula below.
AEO = 0.01328 D2 V3
So, the larger the rotor, the more Where:
energy it can capture. The air density, AEO = Annual energy output,
ρ, changes slightly with air tempera- kWh/year
ture and with elevation. The ratings
D = Rotor diameter, feet
for wind turbines are based on
standard conditions of 59° F (15° C) V = Annual average wind speed,
at sea level. A density correction mph
should be made for higher elevations The Wind Energy Payback Period
as shown in the Air Density Change Workbook found at www.nrel.gov/
with Elevation graph. A correction for wind/docs/spread_sheet_Final.xls is
temperature is typically not needed a spreadsheet tool that can help you
for predicting the long-term perfor- analyze the economics of a small wind
electric system and decide whether
mance of a wind turbine.
wind energy will work for you. The
Although the calculation of wind spreadsheet can be opened using
power illustrates important features Microsoft Excel 95 software. It asks
about wind turbines, the best mea- you to provide information about how
sure of wind turbine performance is you’re going to finance the system,
annual energy output. The difference the characteristics of your site, and
the properties of the system you’re
between power and energy is that
considering. It then provides you with
power (kilowatts [kW]) is the rate at a simple payback estimation in years.
which electricity is consumed, while If it takes too long to regain your capi-
energy (kilowatt-hours [kWh]) is the tal investment—the number of years
quantity consumed. An estimate of comes too close or is greater than the
the annual energy output from your life of the system—wind energy will
wind turbine, kWh/year, is the best not be practical for you.
way to determine whether a particular
wind turbine and tower will produce
enough electricity to meet your needs.
A wind turbine manufacturer can help
you estimate the energy production
you can expect. They will use a cal-
culation based on the particular wind
turbine power curve, the average
annual wind speed at your site, the


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

Wind Technology Center Web site at ��
www.nrel.gov/wind/ and the DOE
Wind Powering America Web site at
www.windpoweringamerica.gov. ��
Another way to indirectly quantify
the wind resource is to obtain average
wind speed information from a
��
nearby airport. However, caution
should be used because local terrain
influences and other factors may
cause the wind speed recorded at �
� ��
an airport to be different from your ��

12 Small Wind Electric Systems Small Wind Electric Systems 13


Flagging, the effect
of strong winds on ��
area vegetation, ��
can help determine ��
��
area wind speeds. ��

��
��
��

� ��
��
��

��

� ��
��
��
��

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


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

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


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


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

you may have to sign a separate
agreement with each company.
Usually these agreements are writ-
ten by the utility or the electricity


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

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

Bergey XL.10 wind turbine
100-foot free-standing lattice tower
Inverter


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


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

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

water, and space heat. Solar collectors on
the roof provide pre-heating for the hot
water.


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


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


Government Agencies Videos
U.S. Department of Energy’s Energy An Introduction to Residential Wind
Efficiency and Renewable Energy Systems with Mick Sagrillo
Information Portal A 63-minute video answering ques-
www.eere.energy.gov tions most often asked by homeown-
National Climatic Data Center ers as they consider purchasing and
Federal Building, 151 Patton Avenue installing wind power systems
Asheville, North Carolina, 28801-5001 American Wind Energy Association
Phone: (828) 271-4800 Phone: (202) 383-2500
www.ncdc.noaa.gov www.awea.org

U.S. Department of Commerce Web Sites
National Technical Information Small Wind Systems
Service Includes answers to frequently asked
5285 Port Royal Road questions and information on U.S.
Springfield, Virginia 22161 manufacturers.
(800) 553-6847 www.awea.org/smallwind.html
www.ntis.gov Database of State Incentives for
Non-Government Organizations Renewable Energy
American Wind Energy Association www.dsireusa.org
1101 14th St., NW Green Power Network Net Metering
12th Floor Net metering programs are now avail-
Washington, D.C. 20005 able in more than 35 states.
Phone: (202) 383-2500 www.eere.energy.gov/greenpower/
www.awea.org markets
Solar Energy International Small Wind “Talk” on the Web
Short courses on renewable energy AWEA’s Home Energy Systems elec-
and sustainable development tronic mailing list is a forum for the
Phone: (970) 963-8855 discussion of small-scale energy sys-
www.solarenergy.org tems that include wind. To subscribe,
send a subscription request to awea-
Periodicals
wind-home-subscribe@egroups.com.
Apples and Oranges
Mick Sagrillo Wind Energy for Homeowners
A comprehensive comparison of This Web page covers items you
available small wind turbines avail- should consider before investing
able on the Home Power Magazine in a small wind energy system and
Web site: www.homepower.com provides basic information about the
systems.
Home Power Magazine www.nrel.gov/clean_energy/home_
The definitive bimonthly magazine wind.html
for the homemade power enthusiast.
Phone: (800)707-6586 Wind Resource Assessment
www.homepower.com Handbook
www.nrel.gov/docs/legosti/fy97/
22223.pdf


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


Notes

U.S. Department of Energy Regional Offices
www.eere.energy.gov/regions/
States in Region
Southeast Regional Office
75 Spring Street, S.W., Suite 200 Alabama, Arkansas, Florida, Georgia,
Atlanta, GA 30303 Kentucky, Mississippi, North Carolina,
(404) 562-0555 South Carolina, Tennessee, Puerto Rico,
www.eere.energy.gov/regions/southeast U.S. Virgin Islands
Northeast Regional Office
JFK Federal Building, Suite 675 Connecticut, Maine, Massachusetts,
Boston, MA 02203 New Hampshire, New York, Rhode Island,
(617) 565-9700 Vermont
www.eere.energy.gov/regions/northeast
Midwest Regional Office
One South Wacker Drive, Suite 2380 Illinois, Indiana, Iowa, Michigan,
Chicago, IL 60606-4616 Minnesota, Missouri, Ohio, Wisconsin
(312) 353-6749
www.eere.energy.gov/regions/midwest
Central Regional Office
1617 Cole Blvd. Colorado, Kansas, Louisiana, Montana,
Golden, CO 80401 Nebraska, New Mexico, North Dakota,
(303) 275-4826 Oklahoma, South Dakota, Texas, Utah,
www.eere.energy.gov/regions/central Wyoming
Mid-Atlantic Regional Office
1880 John F. Kennedy Boulevard, Suite 501 Delaware, Washington DC, Maryland,
Philadelphia, PA 19103 New Jersey, Pennsylvania, Virginia,
(215) 656-6950 West Virginia
www.eere.energy.gov/regions/mid-atlantic
Western Regional Office
800 Fifth Ave., Suite 3950 Alaska, Arizona, California, Hawaii, Idaho,
Seattle, WA 98104-3122 Nevada, Oregon, Washington, American
(206) 553-1132 Samoa, Guam, Palau, North Marianas
www.eere.energy.gov/regions/western

Wind Powering America
www.windpoweringamerica.gov

A Strong Energy Portfolio for a Strong America
Energy efficiency and clean, renewable energy will mean a stronger economy, a cleaner environment, and greater energy
independence for America. Working with a wide array of state, community, industry, and university partners, the U.S. Department
of Energy’s Office of Energy Efficiency and Renewable Energy invests in a diverse portfolio of energy technologies.

Produced for the U.S. Department of Energy by the For more information contact:
National Renewable Energy Laboratory, EERE Information Center
a DOE national laboratory 1-877-EERE-INF (1-877-337-3463)
www.eere.energy.gov
DOE/GO-102005-2095 • March 2005
Printed with a renewable-source ink on paper containing at least 50% wastepaper, including 20% postconsumer waste.

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