What is wind energy?
In reality, wind energy is a converted form of solar energy. The
sun's radiation heats different parts of the earth at different
rates-most notably during the day and night, but also when
different surfaces (for example, water and land) absorb or
reflect at different rates. This in turn causes portions of the
atmosphere to warm differently. Hot air rises, reducing the
atmospheric pressure at the earth's surface, and cooler air is
drawn in to replace it. The result is wind.
Air has mass, and when
it is in motion, it contains the energy of that motion("kinetic
energy"). Some portion of that energy can converted into other
forms mechanical force or electricity that we can use to perform
work.
Wind energy systems provide a cushion
against electricity price increases. Wind energy systems reduce
U.S. dependence on fossil fuels, and they don't emit greenhouse
gases. If you are building a home in a remote location, a small
wind energy system can help you avoid the high costs of
extending utility power lines to your site.
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 altogether avoided utility costs. They length of the
payback period ¡X the time before the savings resulting from your
system equal the system cost ¡X depends on the system you choose,
the wind resource in your site, electric utility rates in you're
area, and how you use your wind system.
Small wind energy systems can be used in
connection with an electricity transmission and distribution
system (called grid-connected systems), or in stand-alone
applications that are not connected to the utility grid. 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 can be sold to the utility. With the
interconnections available today, switching takes place
automatically. Stand-alone wind energy systems can be
appropriate for homes, farms, or even entire communities (a
co-housing project, for example) that are far from the nearest
utility lines. Either type of system can be practical if the
following conditions exist.
Conditions for stand-alone
systems
- You live in an area with average annual
wind speeds of at least 4.0 meters per second (9 miles per
hour)
- A grid connection is not available or
can only be made through an expensive extension. The cost of
running a power line to a remote site to connect with the
utility grid can be prohibitive, ranging from $15,000 to more
than $50,000 per mile, depending on terrain.
- You have an interest in gaining energy
independence from the utility
- You would like to reduce the
environmental impact of electricity production
- You acknowledge the intermittent nature
of wind power and have a strategy for using intermittent
resources to meet your power needs
Conditions for grid-connected
systems
- You live in an area with average annual
wind speeds of at least 4.5 meters per second (10 miles per
hour).
- 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.
- Local building codes or covenants allow
you to legally erect a wind turbine on your property.
- You are comfortable with long-term
investments.
How do utility-scale wind power plants compare in cost to other
renewable energy sources?
Wind is the low-cost
emerging renewable energy resource.
How do residential
wind turbines work?
A wind turbine, which
is installed on top of a tall tower, collects kinetic energy
from the wind and converts it to electricity that is compatible
with a home's electrical system.
In a normal
residential application, a home is served simultaneously by the
wind turbine and a local utility. If the wind speeds are below
cut-in speed (7-10 mph) there will be no output from the turbine
and all of the needed power is purchased from the utility. As
wind speeds increase, turbine output increases and the amount of
power purchased from the utility is proportionately decreased.
When the turbine produces more power than the house needs, the
extra electricity is sold to the utility. All of this is done
automatically. There are no batteries in a modern residential
wind system.
Small wind systems for
remote applications operate somewhat differently.
Will a small wind
turbine save me money?
A wind turbine
typically lowers a household electricity bill by 50% to 90%. It
is not uncommon for wind turbine owners with total-electric
homes to have monthly utility bills of only $8 to $15 for nine
months of the year. In northern parts of the U.S. where less air
conditioning is used the bills can be very low year-round. The
amount of money a small wind turbine saves you in the long run
will depend upon its cost, the amount of electricity you use,
the average wind speed at your site, and other factors.
Since energy
conservation is usually less expensive than energy production,
making your house or farm more energy-efficient first will
likely reduce the amount of investment in a wind system to meet
your needs. Most wind system purchasers have done all the
reasonable efficiency measures first.
What size turbine do I need for my home?
Homes use
approximately 10,000 kilowatt-hours (kWh) of electricity per
year (about 830 kWh per month). Depending upon the average wind
speed in the area, a wind turbine rated in the range of 5 to 15
kilowatts would be required to make a significant contribution
to meet this demand.
Who should consider buying a wind turbine?
A residential wind
turbine can be a relatively large device and is not suitable for
urban or small-lot suburban homes. Except for very small wind
turbines (i.e., with rotors one meter or less in diameter) on
very small towers, a property size of one acre or more is
desirable.
The economics of a
wind system are very sensitive to the average wind speed in the
area, and to a lesser extent, the cost of purchasing
electricity. As a general rule of thumb, if economics are a
concern, a turbine owner should have at least a 10-mph average
wind speed and be paying at least 10 cents/kWh for electricity.
Residential wind
turbines have been installed in at least 47 of the 50 states,
but the majority of the units have been installed in the
Northeast and the Midwest.
Will it help the environment if I install a wind turbine at my
home?
Yes. Wind turbines
produce no pollution and by using wind power you will be
offsetting pollution that would have been generated by your
utility company. Over its life, a small residential wind turbine
can offset approximately 1.2 tons of air pollutants and 200 tons
of global warming pollutants (carbon dioxide and other gases
which cause global warming).
Do wind turbines make noise or interfere with TV reception?
Small wind turbines do
make some noise, but not enough to be found objectionable by
most people. A typical residential wind system makes less noise
than the average washing machine. Small wind turbines do not
interfere with TV reception.
Will a small wind turbine damage neighboring property values?
With thousands of
small wind turbines installed today in the U.S., there is no
evidence to support this claim, and several surveys or other
information sources that indicate otherwise.
Will I have to change any of the wiring in my house?
No. A wind turbine can
easily be installed at virtually any existing home without the
need to change any wiring or appliances. In most cases, the
utility will install a second utility meter to measure how much
surplus electricity it is receiving from the turbine owner.
How reliable are wind turbines? Will I have to perform much
maintenance?
Most small turbines
have very few moving parts and do not require any regular
maintenance. They are designed for a long life (up to 20 years)
and operate completely automatically.
How do wind turbines perform as an investment?
The wind system will
usually recoup its investment through utility savings within six
to 15 years and after that the electricity it produces will be
virtually free. Over the long term, a wind turbine is a good
investment because a well-sited wind system increases property
value, similar to any other home improvement. Many people buy
wind systems in preparation for their retirement because they
don't want to be subject to unpredictable increases in utility
rates.
How many turbines are needed to power a household or farm?
For a home or farm,
one turbine is normally installed. The turbine's size is chosen
to meet the energy requirements given the available wind
resource. Turbines with power ratings from 1 kW to 25 kW are
typically used.
For village
electrification applications, both single and multiple turbine
installations are common, and turbines up to 100 kW in capacity
may be used.
How do small turbine costs compare to the costs of other
alternatives?
Small wind turbines
(ranging in size from 250 watts to 50 kW) are often the least
expensive source of power for remote sites that are not
connected to the utility system.
A study by the
Congressional Office of Technology Assessment found wind to be
cheaper for meeting remote loads (loads not connected to a
utility system) than diesel generators, photovoltaics, or
utility transmission line extensions. (Micro-hydro also was
found to be less expensive in many locations.)
Hybrid systems --
wind/photovoltaic, wind/diesel, and other combinations -- can
often provide the most efficient and cost-effective option for
rural electrification. Photovoltaic (PV) solar cells, which
convert sunlight directly into electricity -- are often used to
supplement wind power since PV tends to operate best in low wind
months. Diesel generators or batteries can be used for backup
power and to maintain power production during low wind seasons.
One study of an Arctic
community with annual average wind speeds of 15 mph compared the
cost of a 500-kW diesel system to that of a 200-kW diesel
generator and four mid-sized wind turbines. It found that the
wind/diesel combination cost considerably more to install
($378,000 versus $125,000), but would deliver fuel savings of
$90,000 per year, paying for itself in less than three years.*
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