| Wind Energy - Myth Busting |
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| The Biophile Team | |||
| Wednesday, 23 January 2008 | |||
  Humans have been harnessing the wind's energy for hundreds of years with windmills which have been used for pumping water or grinding grain. A wind turbine - the modern equivalent of the windmill - uses the wind's energy to generate electricity.How do wind turbines work? Wind turbines are mounted on towers about 30 metres above ground where they can take advantage of the faster and less turbulent wind to capture the most energy. They usually have two or three propeller-like blades, mounted on a shaft, which catch the wind's energy. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is known as lift. The force of the lift is much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity. Wind farms South Africa has an abundance of wind resources, and there are two key wind power projects in South Africa: at Klipheuwel and Darling, both in the Western Cape. The Western Cape's winds are considered perfect for wind energy - prevailing winds are from two directions, and usually blow during peak electricity consumption periods. Windy Myths There are many myths surrounding the implementation of wind energy as a viable source of electricity. Here are some of the more commons ones. MYTH - Wind Turbines are a Nuisance "Turbines are noisy" Fact: Wind turbines are quiet. An operating modern wind farm at a distance of 200 to 300 meters is no noisier than a kitchen refrigerator or a moderately quiet room. The sound turbines produce is similar to a light whooshing or swishing sound, and much more quiet than other types of modern-day equipment. Even in rural or low-density areas, where there is little additional sound to mask that of the wind turbines, the sound of the blowing wind is often louder. Modern wind turbines have been designed to drastically reduce the noise of mechanical components Exceptions to quiet operating turbines can occur in two instances - with older turbines from the 1980’s and in some types of hilly terrain. Modern wind turbines have been designed to drastically reduce the noise of mechanical components so the most audible noise is the sound of the wind interacting with the rotor blade. However, in some hilly terrain where residences are located in sheltered dips or hollows downwind from turbines, turbine sounds may carry further and be more audible. This effect can generally be anticipated and avoided in the development process through adequate setbacks from homes. "Nearby residences will be affected by shadow flicker" Fact: Shadow flicker is the term used to describe what happens when rotating turbine blades come between the viewer and the sun, causing a moving shadow. Shadow flicker is almost never a problem for residences near new wind farms, and in the few cases where it could be, it is easily avoided. For some who have homes close to wind turbines, shadow flicker can occur under certain circumstances and can be annoying when trying to read or watch television. However, the effect can be precisely calculated to determine whether a flickering shadow will fall on a given location near a wind farm, and how many hours in a year it will do so. Potential problems can be easily identified using these methods, and solutions range from the appropriate setback from the turbines to planting trees to disrupt the effect. Normally, shadow flicker should not be a problem in South Africa because at our latitudes the sun's angle is not very low in the sky. If any effect is experienced, it is generally short-lived, as in a few hours over a years. “Turbines interfere with television and other communications signals" Fact: Interference is rare and easily avoided. Large wind turbines installed at wind farms can interfere with radio or television signals if a turbine is in the "line of sight." Improving a receiver's antenna or installing relays to transmit the signal around the wind farm solves this problem; both solutions are common practice in modern wind energy development. "Turbines are ugly" Fact: Beauty is in the eye of the beholder. Some people feel wind turbines are majestic. Wind farm developers have computer-modelling tools that accurately depict virtual views from given spots in the surrounding area. Careful design of a wind project can alleviate many visual concerns. MYTH - Wind Turbines Do Not Benefit Local Communities "Wind Projects Harm Property Values" Fact: There is no evidence that the presence of a commercial wind farm within sight of a property systematically decreases that property's value. In fact, a nationwide study conducted in 2003 surveyed property near multiple wind farms and found that not only do wind farms not harm property values, in some cases the values increased. "Wind projects depress tourism" Fact: There is no evidence to indicate that wind turbines drive tourists away. In some areas, wind turbines even draw tourists. Surveys of tourists have found that the presence of wind turbines would not affect the decision of most visitors to return. Local governments frequently work with developers to install information stands and signs near wind farms, as well as pull-off areas, similar to "scenic overlooks", from nearby roads. Surveys of tourists have found that the presence of wind turbines would not affect the decision of most visitors to return. The thousands of turbines in Palm Springs, California, have had no negative impact on the tourism business; on the contrary, the local tourism centre organises bus tours to the wind farms. MYTH - Wind Turbines Harm Wildlife "Turbines kill many birds and bats" Fact: Wind energy development's overall impact on birds is extremely low compared with other human-related activities. No matter how extensively wind is developed in the future, bird deaths from wind energy are unlikely to ever be more than a small fraction of bird deaths caused by other human-related sources, such as cats and buildings. However, birds and bats occasionally collide with wind turbines, as they do with other tall structures such as buildings. Wind farm operators there have worked with wildlife officials and experts to reduce the impacts on birds Raptor kills (of eagles, hawks, and owls) are a problem at one large older wind farm in California, in Altamont Pass, built in the 1980’s. Wind farm operators there have worked with wildlife officials and experts to reduce the impacts on birds, and those efforts continue today. Prior to 2003, bat kills at wind farms studied were low. However, the frequency of bat deaths at a newly constructed wind farm in West Virginia in 2003 has caused concern. In response, AWEA and several of its member companies have entered into a three-year cooperative effort with Bat Conservation International, the National Renewable Energy Laboratory, and the U.S. Fish and Wildlife Service to research wind/bat interaction and test ways to reduce bat mortality. Despite the minimal impact wind development has on bird and bat populations, the industry takes potential impacts seriously. In addition to special initiatives such as those described above, avian studies are routinely conducted at wind sites before projects are proposed. Pre-construction wildlife surveys are now common practice throughout the industry. "Wind projects fragment wildlife habitat" Fact: Wind farms are most often built in areas close to transmission lines where habitat has already modified and fragmented, typically by farming and ranching. Moreover, wind energy has a light footprint, with only the turbine itself, along with some roads and power lines, impacting the land, while pre-existing land use continues around the turbines as before. Windy land can also often be found in undeveloped areas, however, so habitat fragmentation can be a concern, especially in unbroken stretches of prairie grasslands or forests. The industry calls for more research to better understand the extent of possible habitat or wildlife impacts in these areas, including the effects of not developing renewable energy sources and thereby aggravating global warming and pollution pressures on wildlife and their habitats. MYTH - Wind Turbines are Expensive and Unreliable "Back-up generation is needed for all wind turbines" Fact: Because of the grid's inherent design, there is no need to back up every megawatt of wind energy with a megawatt of fossil fuel or dispatchable power. The electric grid is designed to have more generation sources than are needed at any one time because no power plant is 100% reliable. It is a complicated system designed to absorb many impacts, from electric generation sources going off-line to industrial customers starting up energy-intensive equipment. The grid operator matches electricity generation to electricity use, and wind energy's variability is just one more variable in the mix. The reality is that wind energy is naturally variable, but not unreliable. Many so-called reliable sources of electricity suffer from unexpected outages, such as nuclear reactors and coal plants that shut down, often at short notice, for safety repairs or maintenance. Yet no one proposes to back up a coal or nuclear power plant with a similar amount of generation from another plant. The reality is that wind energy is naturally variable, but not unreliable. Wind farms are built in windy areas, and seasonal and daily wind generation patterns can be anticipated. Denmark, and grids in regional areas elsewhere in Europe operate with 10-15% or more of their power coming from wind, without increased reliability problems or need for additional back-up power plants. Faulty turbines, when they occur, are repaired while the other turbines continue to operate. And in contrast to conventional power plants, wind farms do not shut down altogether for maintenance and repairs - faulty turbines, when they occur, are repaired while the other turbines continue to operate. "Wind turbines operate only a small fraction of the time" Fact: Wind turbines generate electricity most (65-80%) of the time, although the output amount is variable. No power plant generates at 100% "nameplate capacity" 100% of the time. Nameplate capacity refers to the maximum generation potential of a power plant. A conventional power plant is occasionally closed for maintenance or repairs, or runs below full capacity to best match demand. Wind farms are built in areas where the wind blows most of the time, but because of variations in speed, a wind farm will generate power at full rated capacity about 10% of the time, and on average throughout the year the plant will generate 30% to 35% of its rated capacity. "Wind energy will never provide more than a little electricity" Fact: South Africa's wind energy potential is described as "fair" with promising wind speeds along the coastline, where the potential compares favourably with Europe. Research into the wind energy potential started (and unfortunately, basically ended) with Diab's publication of the “Wind Atlas of South Africa in 1995”. New wind data collection has been limited to assessments in specific areas (such as the Eastern Cape assessment carried out by the CSIR) or detailed feasibility studies carried out in specific locations such as Darling and Klipheuwel, Western Cape. There is therefore, a clear need to build on Diab's work and expand the information on the wind energy resource in South Africa.Wind turbines are efficient, and that is part of their beauty. "Wind turbines are inefficient" Fact: Wind turbines are efficient, and that is part of their beauty. One of the simplest ways to measure overall efficiency is to look at the "energy payback" of an energy technology, i.e. the amount of energy it takes to produce a given amount of energy. The energy payback time for wind is in fact similar to or better than that of conventional power plants. Wind turbines are also highly efficient in a larger sense: they generate electricity from a natural, renewable resource. A recent study by the University of Wisconsin-Madison calculated that the average energy payback of wind farms to be between 17 and 39 times as much energy as they consume (depending on the average wind speeds at the site), while nuclear power plants generate only about 16 times and coal plants 11 times as much energy as they consume. Wind turbines are also highly efficient in a larger sense: they generate electricity from a natural, renewable resource, without any hidden social or environmental costs - there is no need to mine for fuel or transport it, no polluting or climate-changing emissions created, and no need to store, treat, or dispose of wastes. "Wind energy is expensive" Fact: Wind energy is now competitive with power from new conventional power plants. The up-front, capital cost of wind energy is more expensive than that of some traditional power technologies such as natural gas. However, there is no cost of fuel, and in good locations the "levelized" cost (the cost of capital, the cost of fuel, and the cost of operations and maintenance over the lifetime of the plant) of wind energy can now be less than that of other energy sources.
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