Small Wind Turbines
Harnessing the power of the wind has begun to recapture the imagination of America. Returning to
a technology that was prevalent during colonial times has become an intriguing idea to many people
including many residents of Montgomery County. The county, with its mix of rural, suburban, and urban
areas, provides many opportunities for residents to incorporate wind power into their homes. Wind
energy is an emerging technological approach to energy production that can have positive economic
and environmental impacts for those committed to the cause of renewable energy.
The Technology
Today’s wind turbines are a far cry from the large, wooden turbines of colonial times. Modern technology
has allowed wind turbines to become smaller, lighter, more durable, and much more efficient. Small wind
Vertical axis wind turbine in a residential setting.
turbines are defined as having an energy generation capacity
of 100 kilowatts per hour (kWhrs) and less. The standard
commercial ratings for a wind turbine are determined using the
peak production values possible for that size turbine. Actual
energy production will fluctuate due to the unpredictable nature
of wind. A typical household uses roughly 950 kWhrs a month,
so the energy production of a small wind turbine can create a
substantial amount of cost savings.
Wind turbines come in a wide range of styles and sizes. They
typically have a horizontal axis or a vertical axis. The horizontalaxis wind turbine is most commonly used today. It is characterized
by the propeller shape of the turbine and usually uses three
blades. The vertical-axis design, like the eggbeater-style Darrieus
model, named after its French inventor, is less common. Studies
show at this point the technology is less efficient, less reliable, and
more expensive than the horizontal variety. The Darrieus model
is more visually appealing to some people, and new technologies
may make this a more economically viable option in the future.
Other wind turbine technologies, which do not exactly fit into the
two main types, have begun to emerge. These technologies will
continue to evolve, becoming more efficient and affordable as
demand increases. Municipalities and their residents should try
and keep current on the latest wind turbine technologies.
Benefits and Considerations
Reduced carbon emissions. One residential-scale turbine can
displace the carbon emissions from 1.5 cars.
Clean energy. There are no emissions, water use, or hazardous
waste associated with wind turbine use. Though, as with almost
any manufactured product, the production and installation
of wind turbines leaves a carbon footprint that should be
considered.
Save money. A 5-15 kWh turbine can reduce a residence’s annual
electricity bill by 50 percent.
Installation costs. A small turbine can cost anywhere from $6,000
to $22,000 installed, depending upon size, application, and service
agreements with the manufacturer.
Property value. While only a few studies may exist, they generally
show an increased property value for those owning a wind turbine
and no decrease in neighbors’ property values.
Top photo: View from the base of a horizontal wind turbine.
Middle photo: Vertical-axis wind turbine.
Bottom photo: Rooftop wind turbines at the University of Arizona.
Emergency back-up power if necessary. Wind turbines
can generate power for a building when the electrical grid
experiences failure.
Courtesy of AEWA
Wind Speeds Increase with Height
150
Tower height, ft
120
90
Net Metering Benefits. It is crucial to understand the importance
of net metering. Net metering is a way to calculate the energy
consumed and produced on a site containing its own alternative
energy generator, such as a wind turbine. Using net metering,
the excess electricity produced by the wind turbine will spin the
electricity meter backwards, effectively banking the electricity
until it is needed by the customer. This allows the owner of
the wind turbine to be compensated for any excess electricity
produced. Net metering is required of utilities in Pennsylvania
and is an important motivator for the implementation of
alternative energy systems.
60
Maintenance. Wind turbines have very few moving parts.
This simplicity creates a higher degree of reliability than other
energy production systems that are more complex. Most
manufacturers suggest that wind turbines undergo maintenance
by a professional every few years and it is estimated that a small
wind turbine can have a lifespan of 20 years or more.
30
0
41
75
100 124
Increase in wind power, %
Wind Turbulence Effects
10-kilowatt
400-watt
Courtesy of AEWA
0
Prevailing Winds
30’
Region of High
Turbulence Flow
35’-50’
Tower
80’-120’
Tower
Wind Turbine Noise Comparison
Decibels
Jet Airplane
Pneumatic drill
Industrial Noise
Inside car
Home
Bedroom
Falling leaves
Stereo music
Office
Wind turbine
Whisper
Courtesy of AEWA
500 feet
Regulatory Considerations
Height. The higher the turbine the better. When wind is
disturbed by surrounding structures or natural obstacles the
wind turbine loses speed and a degree of its power-generation
potential. The higher a wind turbine can arise above any possible
obstacles, the more efficiently the turbine will produce power.
Studies show that the turbine should be at least 30 feet above the
nearest obstruction within 300 feet. This will allow the turbine
to capture the strongest winds. Safety and visual considerations
must be taken into account when regulating the height.
Setbacks. Setbacks on a property are an important consideration
due to the height of wind turbines. The setback requirements can
be based on turbine height or by requiring a minimum lot size.
Noise. Small-scale wind turbines are much quieter than
commonly thought, but to ensure the turbine is not a noise
nuisance, many regulations set a decibel limit at property
lines. It is important to take the setting (rural versus urban)
and acceptable nighttime decibel levels into account when
considering decibel regulations.
Aesthetics. Visual impact is one of the most difficult challenges
for residential wind turbines. Appearance is difficult to regulate,
but some language is available to handle the issue. This language
could include ground-level screening and buffering requirements
as well as regulation of wind turbines in the line-of-sight of scenic
or cultural resource areas.
Safety. There are a series of regulations that can be adopted
to ensure an adequate level of safety. These include building
and electrical code requirements along with possible fencing
and other climbing deterrents.
Bird and bat mortality. An issue frequently associated with
wind turbines is the rate of bird and bat kills due to collisions
with the turbine. This subject is being explored by scientists.
The most recent information points to wind turbines being no
more dangerous to birds and bats than other tall structures,
though animal deaths may occur. To be safe, wind turbines
should be setback from Important Bird Areas and from
identified wetlands.
For more information, please contact the Montgomery County
Planning Commission at 610.278.3722 or visit our site online at
www.planning.montcopa.org to see the complete renewable
energy series and other resources.
Printed on recycled paper
Printed in 2011
Montgomery County Planning Commission
Montgomery County Court House
PO Box 311, Norristown, Pennsylvania 19404
website: www.planning.montcopa.org