Abstract
![Cows and wind turbines.](https://webarchive.library.unt.edu/eot2008/20090117143017im_/http://attra.ncat.org/images/smallwind/cows06331.jpg)
Farms and ranches, such as this one in southwest Minnesota,
can use wind-generated electricity to reduce utility bills.
Photo courtesy of NREL |
Wind-generated electricity is attracting the interest of farmers, ranchers, and other landowners across
the country. People find wind energy attractive for a variety of reasons, including its potential economic
benefits and its lower impact on the environment when compared to coal and other electric power
generation fuels. Wind-generated electricity can help farmers and ranchers reduce their energy costs,
an important consideration in these days of continually increasing utility rates.
This publication will introduce you to small-scale wind energy to help you decide if wind energy is an
economical option for your farm or ranch.
Funding for the
development of this publication was provided by the USDA Risk
Management Agency. |
Table of Contents
Introduction
Wind energy systems use the wind
to generate electricity with a wind
turbine. More and more people
are considering wind energy as
they look for affordable and reliable
sources of electricity. Small
wind electric systems can make
an important contribution to our
nation's energy needs. In 2005,
the United States installed more new wind
energy capacity than any other country in
the world. The new capacity, totaling 2,431
megawatts (MW), was worth more than
$3 billion in generating equipment, and it
brought the total national wind energy capacity
to 9,149 MW. That's enough electricity to
power 2.3 million average American households.
In 2006, an additional 2,454 MW
was installed, bringing the nation's total
installed capacity to 11,603 MW.
Many rural areas have sufficient wind
speeds to make wind an attractive alternative,
and farms and ranches can often install
a small-scale wind energy system without
impacting their ability to plant crops and
graze livestock. Most farms and ranches
have enough open land (generally an acre or more) to provide a significant portion of
their electricity from wind power.
Why Should I Choose Wind?
Wind energy can be a cost-effective small-scale
renewable energy system. Depending
on your wind resource and the electric
consumption on your farm, a small wind
energy system can lower electricity bills,
help avoid the high costs of extending utility
power lines to remote locations, prevent
power interruptions, and provide a non-polluting
source of electricity.
How Do Wind Turbines Work?
Wind is created by the unequal heating of
the Earth's surface by the sun. Wind turbines
convert the kinetic energy in wind into mechanical power that runs a generator
to produce clean electricity. Today's turbines
are versatile sources of electricity.
Their blades are aerodynamically designed
to capture the maximum energy from the
wind. The wind turns the blades, which
spin a shaft connected to a generator that
makes electricity.
Back to top
Is Wind Energy Practical for Me?
A small wind energy system can provide
you with a practical and economical source
of electricity if:
- your property has a good wind resource
- you have at least one acre of land in a rural area
- your local zoning codes or covenants allow wind turbines
- you have high electric costs
- your property is in a remote location that does not have easy access to utility lines
- you are comfortable with long-term investments
![Plowed field and wind turbines](https://webarchive.library.unt.edu/eot2008/20090117143017im_/http://attra.ncat.org/images/smallwind/windfield.jpg)
Wind turbines operate in harmony with farming and ranching.
Photo courtesy of NREL |
It's important to examine your reasons for
wanting to purchase a wind energy system. If
your reasons are purely economic, you could
end up disappointed, since wind energy
systems can have long payback periods. If you are also interested in benefits such as
environmental protection, independence,
or energy security, you may find the cost
and payback period to be perfectly acceptable.
Make sure you fully understand the
results you can expect, as well as potential
obstacles, such as zoning laws, generation
capacity, maintenance requirements, and
warranty coverage.
First Things First:
Make Your Farm Buildings as
Energy-Efficient as Possible
Before choosing a wind system for your farm
or ranch, you should reduce your energy consumption
as much as possible. This topic
is discussed in greater detail in the ATTRA
publication Efficient Agricultural Buildings:
An Overview. Energy conservation is almost
always more cost-effective than renewable
energy systems, and could reduce the size of
your wind energy system. From wall insulation
to light bulbs, there are many ways to
make your farm buildings more efficient.
- Reduce your heating and cooling needs by up to 30% by investing just a few hundred dollars in proper insulation and weatherization products.
- Save money and increase comfort by properly maintaining and upgrading your heating, ventilation, and air-conditioning systems.
- Install double-paned, gas-filled windows with low-emissivity (low-e) coatings to reduce heat loss in cold climates and spectrally selective coatings to reduce heat gain in warm climates.
- Replace your lights in high-use areas with fluorescents. Replacing 25% of your lights can save about 50% of your lighting energy bill.
- When shopping for products such as lighting, windows, and heating and cooling systems, look for the ENERGY STAR® label. ENERGY STAR® products have been identified by the U.S. Environmental Protection Agency and U.S. Department of Energy as being the most energy-efficient products in their classes.
|
Is There Enough Wind at
My Site?
Does the wind blow hard and consistently
enough at your site to make a small wind
turbine system economically worthwhile?
That is a key question and not always easily
answered. The wind resource can vary
significantly over an area of just a few miles
because of local terrain influences on the
wind flow. Yet, there are steps you can take
that can help answer this question.
As a first step, a wind resource map can
help you estimate the wind resource in
your region. State wind resource maps,
such as those found on the Wind Powering
America website will help you understand
the resources in your specific region.
Note that maps for some states show wind
speed estimates at 50 meters above the
ground and depict the resource that could
be used for utility-scale wind development.
DOE's future plans include providing
wind speed estimates at 30 meters,
which are useful for identifying small
wind turbine opportunities.
![NREL Wind Map](https://webarchive.library.unt.edu/eot2008/20090117143017im_/http://attra.ncat.org/images/smallwind/nrel_wind_map.jpg)
Source: U.S. Department of Energy
You can find additional wind resource maps, showing region-specific data, in
NREL's Wind Energy Resource Atlas
of the United States, available online. For
western regions, consult windpowermaps.org and The Renewable Energy Atlas of
the West. For California only, consult California
Wind Resource Maps. Note that wind
maps provide only broad estimates—the
wind speed for any particular site is often
a prediction based on terrain, rather
than an actual measurement. The actual
wind resource at a specific site may differ
considerably from these estimates. For
site-specific wind resource data, consult
a turbine dealer or install an anemometer
(a device that measures wind speed) on
your property.
In general, the highest average wind
speeds in the United States are found along seacoasts, on ridgelines, and in the
Great Plains; however, many areas have
wind resources strong enough to power
a small wind turbine economically. The
wind resource estimates on the map above
generally apply to terrain features that are
well-exposed to the wind, such as plains,
hilltops, and ridge crests.
Another way to estimate the wind resource
is to get average wind speed information
from a nearby airport. Use caution, however,
because local terrain and other factors
may cause the wind speed recorded at an
airport to be different from your particular
location. Also, airport wind speeds are
generally measured at heights of only about
20-33 feet (6–10 meters) above ground.
Average wind speeds increase with height
and may be 15–25% greater at a typical
small wind turbine hub-height of 80
feet (24 meters) than those measured at
airport anemometer heights. The National
Climatic Data Center collects data from
airports in the United States and makes
wind data summaries available for purchase.
Summaries of wind data from
almost 1,000 U.S. airports also are
included in Wind Energy Resource Atlas
of the United States, available online.
Another useful, indirect way to measure
the wind resource is by observing vegetation.
Trees, especially conifers or evergreens,
can be permanently deformed by
strong winds. This deformity, known as“flagging,” has been used to estimate the
average wind speed for an area. For more
information on flagging, you may want to
obtain A Siting Handbook for Small Wind
Energy Conversion Systems, by H. Wegley,
J. Ramsdell, M. Orgill & R. Drake,
Report No. PNL-2521, available from National Technical Information Service, (703) 605-6585.
![flagging chart](https://webarchive.library.unt.edu/eot2008/20090117143017im_/http://attra.ncat.org/images/smallwind/flagging.jpg)
Flagging, the effect of strong winds on area vegetation, can help determine area
wind speeds.
Source: Windustry.
Direct monitoring by a wind resource
measurement system at a site provides the
clearest picture of the available resource.
A good overall guide on this subject is
the Wind Resource Assessment Handbook,
(PDF / 2.1M) available online. Wind measurement
systems are available for as little
as $600 to $1,200. This expense may
or may not be justified, depending on the
exact nature of your proposed small wind
system. The measuring equipment must
be set high enough to avoid turbulence
created by trees, buildings, and other
obstructions. The most useful readings are those taken at hub-height. If there is a
small wind turbine system in your area, you
may be able to obtain information on the
annual output of the system or wind speeds
at its location.
Back to top
Zoning Issues
Before you invest in a wind energy system,
you should research potential obstacles.
Some jurisdictions, for example, restrict the
height of the structures permitted in residentially
zoned areas, although variances
might be allowed. Most zoning ordinances
have a height limit of 35 feet. You can find
out about the zoning restrictions in your
area by calling the local building inspector,
board of supervisors, or planning board. As
a minimum, contact the county commission
to ask what, if any, county requirements
exist. They can tell you if you will need to
obtain a building permit and provide you
with a list of requirements. In addition to
zoning issues, your neighbors might object
to a wind machine that blocks their view,
or they might be concerned about noise.
Most zoning and aesthetic concerns can be
addressed by supplying objective data.
For more information about permitting,
see AWEA's Small Wind Toolbox: Getting a
Building Permit.
Back to top
What Size Wind Turbine
Do I Need?
![Wind turbine and tank.](https://webarchive.library.unt.edu/eot2008/20090117143017im_/http://attra.ncat.org/images/smallwind/texas07169.jpg)
This 1-kW wind turbine from
World Power Technology,
Inc. is used for pumping
water for 120 head of
cattle at a ranch in Texas.
Source: World Power
Technology |
The size of the wind turbine you need
depends on your application. Most turbines
are rated according to peak wattage. Small
turbines are rated from 100 watts to 100
kilowatts (one kilowatt equals 1,000 watts).
One- to 10-kW turbines can be used in
applications such as pumping water.
A wind turbine manufacturer can provide
you with the expected annual energy output
of the turbine as a function of annual average
wind speed. The manufacturer will also
provide information on the maximum wind
speed for safe operation. 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 decide what size of
turbine will best meet your electric needs.
What are the Basic Parts of a
Small Wind Electric System?
Home-scale wind energy systems are generally
comprised of a rotor, a generator or
alternator mounted on a frame, a tail, a
tower, wiring, and the “balance of system” components: controllers, inverters, and/or batteries. Through the spinning blades,
the rotor captures the kinetic energy of the
wind and converts it into rotary motion to
drive the generator.
To find wind equipment suppliers and
installers in your area, as well as sources
of technical support, see ATTRA's Farm
Energy Search Tool.
Wind Turbine
![Wind turbine.](https://webarchive.library.unt.edu/eot2008/20090117143017im_/http://attra.ncat.org/images/smallwind/bergeyXL.1.jpg)
Bergey XL-1 horizontal-axis upwind machine.
Source: Bergey Windpower |
Most turbines manufactured today are horizontal-axis, upwind machines (the rotor
faces the wind) with two or three blades,
which are usually made of a composite
material such as fiberglass. These machines
are designed so that turbines rotate around
a horizontal axis, and the rotor is placed on
the windward side of the support tower.
The amount of power a turbine will produce
is determined primarily by the diameter of
its rotor. The diameter of the rotor defines
its “swept area,” or the quantity of wind
intercepted by the turbine. The turbine's
frame is the structure onto which the rotor,
generator, and tail are attached. The tail
keeps the turbine facing into the wind.
Tower
Because wind speeds increase with height,
the turbine is mounted on a tower. In general,
the higher the tower, the more energy
the wind system can produce. The tower
also raises the turbine above the air turbulence
caused by obstructions such as
hills, buildings, and trees. As a general
rule of thumb, the bottom of the rotor
blades should be 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 energy
production. For instance, raising a 10-kW
generator from a 60-foot tower height to
a 100-foot tower increases system cost
by about 10%, but can increase energy
production by 29%.
Mounting turbines on rooftops is not recommended.
All wind turbines vibrate and
transmit the vibration to the structure on
which they are mounted. This can lead
to noise and structural problems with the
building, and the roofline can cause excessive
turbulence that will shorten the life of
the turbine.
Types of Towers
There are three basic types of towers suitable for farm-sized turbines:
Monopole
This type of tower is generally the least expensive. The tower is a tilt-up style tower and is
generally installed using a gin-pole and winch. Monopoles generally have four guy wires
for support. Maintenance on the turbine is performed by tilting the tower down. The
height of this type of tower is limited by the weight of the machine and generally 10-kW
machines are the largest that can be placed on such towers. Tilt-up towers require space
for guy wires and for tipping up and down of the tower.
Guyed lattice
Guyed lattice towers are generally more expensive than monopole designs but can support
larger turbines at higher heights. Towers are generally installed using gin-pole and
winch. Guyed lattice towers also come with the advantage of either being able to tip the
tower down or relatively easy climb-ability for regular maintenance (climbing, if done
with appropriate safety precautions, gear and training,
is much safer than tilting a tower up and down every
time maintenance is required). Guyed lattice towers
require much space for tipping up and down of tower
and guy wires. Again, check with turbine manufactures
to see what tower options they recommend with various
turbine models.
Lattice
Lattice towers, in most cases, are required for machines
larger than 20 kW in size. The installation of these towers
is generally more complicated than that of a guyed lattice
tower because a crane is needed to lift the tower and
turbine into place. Maintenance is performed by climbing
the tower. If major work is required on a machine a crane
may be required to remove the turbine from the tower.
Check with manufacturers to determine what tower
options they recommend with different turbine models.
Source: Windustry.org. |
Balance of System
The parts that you need in addition to the
turbine and the tower, or the balance of system
parts, will depend on your application.
Most manufacturers can provide you with a
system package that includes all the parts
you need for your application. For example,
the parts required for a water pumping system
will be much different than what you
need for a residential application. The balance
of system required will also depend
on whether the system is grid-connected
(connected to the utility grid), stand-alone
(independent of the utility grid), or part of
a hybrid system (a power system that uses
more than one source of energy—wind and photovoltaics, for example). For a residential
grid-connected application, the balance
of system parts may include a controller,
storage batteries, a power conditioning unit
(inverter), and wiring.
Stand-Alone Systems
Stand-alone systems (systems not connected
to the utility grid) often require
batteries to store excess power for use
when the wind is calm. They also need
a charge controller to keep the batteries
from overcharging. Deep-cycle batteries,
such as those used for golf carts, can
discharge and recharge 80% of their capacity
hundreds of times, which makes them
a good option for remote renewable energy
systems. Automotive batteries are shallow-cycle
batteries and should not be used in
renewable energy systems because of their
short life in deep-cycling operations.
Small wind turbines generate direct current
(DC) electricity. In very small systems, DC
appliances operate directly off the batteries.
If you want to use standard appliances
that use conventional household alternating
current (AC), you must install an inverter
to convert DC electricity from the batteries
to AC. Although the inverter slightly lowers
the overall efficiency of the system, it allows the home to be wired for AC, a definite plus
with lenders, electrical code officials, and
future homebuyers.
For safety, batteries should be isolated from
living areas and electronics because they
contain corrosive and explosive substances.
Lead-acid batteries also require protection
from temperature extremes. Batteries
should be enclosed in a box, which should
be vented to the outside.
Can I Install a Wind Energy
System Myself?
“Most dealers offer either complete turnkey
(ready-to-operate) installations or the
option to purchase direct from the factory
and install the system yourself. The
first option offers more customer support
from the company. Self-installation offers
significant savings and a hands-on understanding
of the turbine. Prospective owners
can discuss the options available with
manufacturers to decide which method
best suits their budget and technical skills.”
– American Wind Energy Association |
Back to top
What Do Wind Systems Cost?
According to the American Wind Energy
Association (AWEA), small wind energy
systems cost from $6,000 to $8,000 for
every kilowatt of generating capacity,
depending on size. Smaller wind systems
are more costly per kilowatt of installed
capacity. Wind energy becomes more
cost-effective as the size of the turbine
increases. Although small turbines cost
less in initial outlay, they are proportionally
more expensive.
A 10-kW system, for example, can cost
$47,000 to $60,000 installed. Rebates,
tax credits, and other incentives can reduce
these costs. Well-sited small wind turbines
can usually pay for themselves within 15
years, about half their serviceable lifetimes,
if the right incentives are applied,
says AWEA.
Although wind energy systems involve a
significant initial investment, they can be competitive with conventional energy
sources when you account for a lifetime of
reduced or avoided utility costs. The length
of the payback period—the time before the
savings resulting from your system equal
the cost of the system itself—depends on
the system you choose, the wind resource
on your site, electric costs in your area, and
how you use your wind system.
Back to top
How Much Energy Will My
System Generate?
As mentioned above, most U.S. manufacturers
rate their turbines by the amount
of power they can safely produce at a particular
wind speed. Even a small increase
in wind speed results in a large increase
in power. That is why a taller tower will
increase the productivity of any wind turbine
by giving it access to higher wind
speeds, as shown in the graph below.
![wind increase graph](https://webarchive.library.unt.edu/eot2008/20090117143017im_/http://attra.ncat.org/images/smallwind/wind-speed-increase-graph.jpg)
The larger the rotor, the more energy it can
capture. The air density changes slightly
with air temperature and with elevation.
The ratings for wind turbines are based on
standard conditions of 59° F (15° C) at sea
level. A density correction should be made
for higher elevations as shown in the graph
below. A correction for temperature is typically
not needed for predicting the long-term
performance of a wind turbine.
![air-density chart](https://webarchive.library.unt.edu/eot2008/20090117143017im_/http://attra.ncat.org/images/smallwind/air-density.jpg)
The best measure of wind turbine performance
is annual energy output. The difference
between power and energy is that
power (kilowatts [kW]) is the rate at which
electric energy is consumed, while energy
(kilowatt-hours [kWh]) is the quantity consumed.
An estimate of the annual energy
output from your wind turbine, kWh/year,
is the best way to determine whether a particular
wind turbine and tower will produce
enough electric energy to meet your needs.
A wind turbine manufacturer or dealer
can help you estimate the energy production
you can expect. They will use a calculation
based on the particular wind turbine
power curve, the average annual wind
speed at your site, the height of the tower
that you plan to use, the elevation, and (if
available) the frequency distribution of the
wind—an estimate of the number of hours
that the wind will blow at each speed during
an average year. Contact a wind turbine manufacturer or dealer for assistance with
this calculation.
To get a preliminary estimate of the performance
of a particular wind turbine, use the
formula below.
AEO = 0.01328 D² V³
Where:
AEO = Annual energy output, kWh/year
D = Rotor diameter, feet
V = Annual average wind speed, mph
Wind Powering America's Wind Energy
Payback Period Workbook is a spreadsheet
tool that can help you analyze the economics
of a small wind electric system and
decide whether wind energy will work for
you. The spreadsheet can be found online (Microsoft Excel / 101K).
The tool asks you to provide information
about how you're going to finance the system,
the characteristics of your site, and the
properties of the system you're considering.
It then provides you with a simple payback
estimate in years.
Back to top
Grid-Connected Systems
Small wind energy systems can be
connected to the electric distribution system
and are then called grid-connected
systems. Grid-connected systems require
a power conditioning unit (inverter), which
makes the turbine output electrically
compatible with the utility grid. Usually,
batteries are not needed. A grid-connected
wind turbine can reduce your consumption
of utility-supplied electricity for
lighting, appliances, and electric heat. If
the turbine cannot deliver the amount of
energy you need, the utility makes up the
difference. When the wind system produces
more electricity than the household
requires, the excess is sent or sold to the
utility. Grid-connected systems can be
practical if the following conditions exist:
- You live in an area with average annual wind speed of at least 10 mph (4.5 m/s).
- Utility-supplied electricity is expensive in your area (about 10 to 15 cents per kilowatt-hour).
- The utility's requirements for connecting your system to its grid are not prohibitively expensive.
- There are good incentives for the sale of excess electricity or for the purchase of wind turbines.
![a grid connected system](https://webarchive.library.unt.edu/eot2008/20090117143017im_/http://attra.ncat.org/images/smallwind/gridconnected.jpg)
Source: U.S. Department of Energy
Back to top
Can I Sell My Excess
Electricity to the Utility?
![Turbine and barn.](https://webarchive.library.unt.edu/eot2008/20090117143017im_/http://attra.ncat.org/images/smallwind/kansas09618.jpg)
Small wind turbines can provide supplemental power
for farms and ranches, such as this farm in western
Kansas. Excess power is fed back into the utility grid.
Photo: Warren Gretz, NREL |
Federal regulations (specifically, the Public
Utility Regulatory Policies Act of 1978, or PURPA) require utilities to connect
with and purchase power from small wind
energy systems. However, you must contact
your utility before connecting to its distribution
lines to address any power quality and
safety concerns. Be aware that some utilities
are more welcoming to interconnection
than others. It is important that, early on
in your planning process, you contact your
utility to learn about its interconnection
policies and expected costs. The American
Wind Energy Association is another good
source for information on utility interconnection
requirements.
Back to top
Financial Incentives
Financial incentives can make wind energy
more affordable for farmers and ranchers.
You can find out what incentives exist at
both state and federal levels at the Database
of State Incentives for Renewable Energy
(DSIRE).
Wind energy can be an attractive alternative
for farms and ranches across the country,
offering numerous benefits, including
reduced energy costs, reduced environmental
impact, and increased energy independence.
However, as with all renewable
energy systems, there also are challenges
to these systems. Conduct a careful analysis
of your energy needs and wind resource
potential, as well as system economics, benefits, and potential obstacles, to see if wind
is a good choice for your farm or ranch.
Back to top
References
Advantages and Disadvantages of Wind Energy
U.S.
Department of Energy, Wind & Hydropower Technologies
Program. www1.eere.energy.gov/windandhydro/wind_ad.html
Consumer's Guide to Renewable Energy in Arkansas
Arkansas Energy Office, October 2005.
www.arkansasrenewableenergy.org/consumers_guide.pdf (PDF / 4.9M)
The Consumer's Guide to Small Wind and Solar Photovoltaic
Generation
NorthWestern Energy, 2007.
The Economics of Small Wind
American Wind Energy
Association. www.awea.org/smallwind/toolbox/TOOLS/fs_economics.asp
Small Wind Electric Systems: A U.S. Consumer's Guide
National Renewable Energy Laboratory, (NREL).
March 2005.
www.eere.energy.gov/windandhydro/windpoweringamerica/pdfs/
small_wind/small_wind_guide.pdf (PDF / 1.3M)
Wind Energy: Harnessing the Wind to Generate Electricity,
Environmental and Energy Study Institute, May
2006. www.eesi.org/publications/Fact%20Sheets/EC_Fact_Sheets/Wind_Energy.pdf (PDF / 126K)
Montana Wind Power: A Consumer's Guide to Harnessing
the Wind, NorthWestern Energy, December 2004.
www.montanagreenpower.com/pdf/montanawindpowerpub.pdf (PDF / 536K)
Wind Powering America program brochure
www.eere.energy.gov/windandhydro/windpoweringamerica/
pdfs/wpa/35873_21century.pdf (PDF / 813K)
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Resources
American Wind Energy Association
Farm Energy Search Tool
National Renewable Energy Laboratory
National Wind Coordinating Collaborative
Union of Concerned Scientists
U.S. Department of Energy
Wind and Hydropower Technologies Program
Windustry
Publications/Links
Burton, Tony, David Sharpe, Nick Jenkins, and Ervin
Bossanyi. Wind Energy Handbook, November 2001
Farming the Wind: Wind Power and Agriculture, Union
of Concerned Scientists. www.ucsusa.org/clean_energy/renewable_energy_basics/farming-the-wind-wind-power-and-
agriculture.html
Gipe, Paul. Wind Energy Basics: A Guide to Small
and Micro Wind Systems, April 1999.
Gipe, Paul. Wind Power, Revised Edition: Renewable
Energy for Home, Farm, and Business. April 2004.
Paul, Greg. New and Improved Wind Power, Mother
Earth News, June/July 2007. www.motherearthnews.com/Alternative-Energy/2007-06-01/Improved-Wind-Power.aspx
A Primer on Small Turbines, Bergey Windpower Co.
www.bergey.com/School/Primer.html
Sullivan, Dan. Farming the Wind: The nuts and bolts
of blade design, site selection and tower technology,
The New Farm, www.newfarm.org/features/0504/
wind2.shtml
Wind Energy FAQs for Consumers, U.S. Department of
Energy Wind and Hydropower Technologies Program. www1.eere.energy.gov/windandhydro/wind_consumer_faqs.html
Wind Energy Payback Period Workbook, Wind
Powering America. www.eere.energy.gov/windandhydro/ windpoweringamerica/docs/small_wind_ economic_model.xls (Microsoft Excel / 101K)
Small-Scale Wind Energy on the Farm
By Cathy Svejkovsky
NCAT Energy Specialist
Tracy Mumma, HTML Production
IP311
Slot 310
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