Small wind’s disadvantages are few and often grossly exaggerated or only perceived problems. They include wind’s variability, bird mortality, aesthetics, property values and unwanted sound. Some people are concerned about wind being more site specific than solar electricity. There’s even concern about ice falling from turbines after ice storms and interference with radio and televisions signals.
Variability and Reliability of the Wind
Perhaps the most significant “problem” with small wind is that the wind does not blow 100 percent of the time in most locations. Wind is a variable resource, to be sure. It’s not available 24 hours a day like coal or oil. In fact, a wind turbine may operate for four days in a row, producing a significant amount of electricity, then sit idle for two days — or a week.
Wind resources vary seasonally, too. In most locations, winds are typically strongest in the fall, winter and early spring, but decline during the summer. Wind even varies during the course of a day. Winds may blow in the morning, die down for a few hours, then pick up later in the afternoon and blow throughout the night.
Even though wind is a variable resource, it is not unreliable. Just like solar energy, you can count on a certain amount of wind at a given location during the year. With smart planning and careful design, you can design a wind system to meet your electrical needs.
Wind’s variable nature can be managed to our benefit by installing batteries to store surplus electricity in off-grid systems. The stored electricity can power a home or office when the winds fail to blow.
Surplus electricity can also be stored on the electrical grid in many systems. Thus, when a wind-electric system is producing more power than a home or business is using, the excess is fed onto the grid. In times of shortfall, electricity is drawn from the grid.
Wind’s variable nature can also be offset by coupling small wind systems with other renewable energy sources, for example, solar-electric systems. Such systems are referred to as hybrid systems. Solar-electric systems (or photovoltaic [PV] systems) generate electricity when sunlight strikes solar cells in solar modules. Hybrid systems can be sized to provide a steady year-round supply of electricity. Residential wind-generated electricity can also be supplemented by small gas or diesel
generators.
Bird Mortality
One perceived problem with wind power is bird mortality. Unfortunately, this issue has been blown way out of proportion. Although a bird may occasionally perish in the spinning blades of a residential wind machine, this is an extremely rare occurrence.
Ian is aware of only one instance of a bird kill, when a hawk flew into a small wind turbine.“Because of their relatively smaller blades and short tower heights, home-sized wind machines are considered too small and too dispersed to present a threat to birds,” notes Mick Sagrillo in his article, “Wind Turbines and Birds,” published by Focus on Energy, Wisconsin’s renewable energy program.
The only documented bird mortality of any significance occurs at large commercial-scale wind turbines — but even then, the number of deaths is relatively small. Commercial wind turbines kill an estimated 50,000 birds per year.
While this may sound like a lot, this number pales in comparison to other lethal forces, among them domestic cats, automobiles, windows in buildings, and communication towers. All in all, cats are probably the most lethal “force” that birds encounter. Scientists estimate that our beloved cats kill about 270 million birds a year nationwide — though the number is very likely much higher.
Aesthetics
Although many people view small wind turbines as things of great beauty, others contend that they detract from natural beauty. Ironically, those who find wind turbines to be unsightly often ignore the great many forms of visual blight in the landscape, among them cell phone towers, water towers, electric transmission lines, radio towers and billboards. To be fair, there are differences between a wind tower and common sources of visual pollution.
For one, a wind turbine’s spinning blades call attention to these machines. Another is that we’ve grown used to the ubiquitous electric lines and radio towers. As a result, people often fail to see them anymore.
Given the opportunity to oppose a structure in their “viewshed” (for example, at a public hearing that may be required for permission to install a residential wind system) neighbors will often speak up in opposition. If you need to apply for permission to install a turbine on a tall tower, you may encounter this problem. We’ll talk about ways to address this in the last chapter.
Proximity to Homes and Property Values
Critics raise legitimate concerns when it comes to the placement of wind machines near their property. Although most of the issues over proximity have been raised by individuals and groups that oppose large commercial wind farms, residential systems can also cause a stir among neighbors. Some may be concerned about aesthetics. Others may worry about safety.
To avoid problems, we recommend installing machines in locations out of sight and hearing of neighbors. Safety concerns are typically related to tower collapse an extremely rare event that is always the result of bad design and improper installation. Even though homeowner’s insurance should cover damage to individuals and property, it is best to place a wind turbine and tower well away from your neighbors’ property lines.
Unwanted Sound
Opponents of wind energy and apprehensive neighbors sometimes voice concerns about unwanted sound, a.k.a. noise, from residential wind machines. Small wind turbines do produce sound, and as the wind speed increases, sound output increases. Sound is produced primarily by the spinning blades and alternators.
The faster a turbine spins, the more sound it produces. You can reduce unwanted sound by selecting a quieter, low-rpm wind turbine rather than a louder, high-rpm wind turbine. If you are concerned about sound, make this a high priority as you shop for a turbine and let your neighbors know you are sensitive to this issue.
Wind turbines have governing mechanisms, systems that slow down the machines when winds get too strong to protect them from damage. Different governing systems result in different sound levels.
When researching your options, we recommend that you listen to the turbines you’re considering buying in a variety of wind conditions, including those that require governing.
To reduce sound at ground level, be sure to mount your turbine on a tall tower. Suitable tower heights, which we’ll discuss later, are usually 80 to 120 feet. A residential wind turbine mounted high on a tower catches the smoother and stronger — and hence most productive — winds. This strategy also helps reduce sound levels on the ground because sound dissipates quickly over distance.
Residential (and commercial) wind machines are also much quieter than many people suspect because the sounds they make are partially drowned out by ambient sounds on windy days. Rustling leaves and wind blowing past one’s ears often drown out much of the sound produced by a residential wind turbine.
Sound is measured in two ways — by loudness and frequency. Loudness is mea- sured in decibels (dB). Frequency is the pitch. A low note sounded on a guitar has a low frequency or pitch. A high note has a high frequency.
The average background noise in a house is about 50 dB. Nearby trees on a breezy day measure about 55 to 60 dB. Most of today’s residential wind turbines perform very near ambient levels over most of their operating range.
Even though the intensity of sound produced by a wind generator may be the same as ambient sound, the frequency may differ. As a result, wind turbine sounds may be distinguishable from ambient noises, even though they are not louder.
You’ll hear a swooshing sound. In other words, while the sound of a wind turbine can be picked out of surrounding noise if a conscious effort is made to hear it, home-sized wind turbines are not the noisy contraptions that some people make them out to be.
Site Specific
Yet another criticism of small wind is that it is more site specific — or restricted —
than solar energy.
To understand what this means, we begin by pointing out that there are good so-
lar areas and good wind areas. In a good solar region, most people with a good
southern exposure can access the same amount of sun. In a windy area, however,
hills and valleys or stands of trees can dramatically reduce the amount of wind that
blows across a piece of property. Therefore, even if you live in an area with suffi-
cient winds, you may be unable to tap into the wind’s energy because of topog-
raphy or nearby forests or stands of tall trees. That’s what critics mean when they
say that wind energy is more site specific than solar.
That said, we should point out that solar resources also vary. If you live in a for-
est in a sunny location, for example, you’ll have a lot less solar energy than a near-
by neighbor whose home is in a field. In addition, homeowners can access the
wind at less-than-optimum sites by installing turbines on tall towers. Tall towers
help you overcome topographical and other barriers.
Ice Throw
Like trees and power lines, wind turbines can ice up under certain conditions. Ice falling off the blades is known as ice throw, and is a concern that may arise during zoning hearings on residential wind turbines.
While ice builds up on blades and wind turbine towers during ice storms, it is typically deposited in very thin sheets. When the blades are warmed by sunlight, the ice tends to break up into small pieces, not huge dangerous chunks, and drop to the ground.
Ice buildup on the blades of a wind turbine dramatically reduces the speed at which a turbine can spin. It’s a little like trying to drive a car with four flat tires. As a result, ice is not thrown from a turbine, it falls around the base of the tower — just as it does from trees and power lines.
Any prudent person would stay away from the tower base when ice is shed from the blades, as they would from trees or power lines covered with ice warming in the sun. Ice-laden trees are also considerably more dangerous, as branches can and often do break and fall to the ground, damaging power lines, cars and houses. Entire trees can topple as a result of ice buildup.
On the rare occasion that ice builds up on a wind turbine, experienced wind turbine operators shut down their machines until the Sun or warmer temperatures melt the ice since they cannot generate electricity spinning at such low revolutions per minute anyway.
Interference with Telecommunications
Some opponents of wind energy raise the issue of interference with telecommunications signals. This is simply not a problem. Turbines for homes and small businesses have small blades that do not interfere with such signals.
Moreover, the blades of modern wind turbines are made out of materials that are “transparent” to telecommunications signals. As a result, small wind turbines are often installed to power remote telecommunications sites. Telecommunication equipment wouldn’t be installed in such locations if there were a problem with interference.
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