WIND POWER AS AN ALTERNATIVE ENERGY SOURCE

Wind power is the conversion of wind energy into more useful forms, usually electricity using wind turbines. In 2005, it accounted for 23% of electricity use in Denmark, 6% in Germany and approximately 8% in Spain. Globally, wind power generation more than quadrupled between 1999 and 2005.

Most modern wind power is generated in the form of electricity by converting the rotation of turbine blades into electrical current by means of an electrical generator. Wind power is used in large scale wind farms for national electrical grids as well as in small individual turbines for providing electricity to rural residences or grid-isolated locations. Wind energy is ample, renewable, widely distributed, clean, and mitigates the greenhouse effect if used to replace fossil-fuel-derived electricity.

Cost and growth of wind power

The cost of wind-generated electric power has dropped substantially. Since 2004, according to some sources, the price in the United States is now lower than the cost of fuel-generated electric power, even without taking externalities into account.

In 2005, wind energy cost one-fifth as much as it did in the late 1990s, and that downward trend is expected to continue as larger multi-megawatt turbines are mass-produced. A British Wind Energy Association report gives an average generation cost of onshore wind power of around 3.2 pence per kilowatt hour. Wind power is growing quickly, at about 38% in 2003, up from 25% growth in 2002. In the United States, as of 2003, wind power was the fastest growing form of electricity generation on a percentage basis.

Advantages of wind power

Wind power is a renewable resource, which means using it will not deplete the earth’s supply of fossil fuels. While burning coal creates pollution and nuclear power leaves radioactive waste, wind power will only affect the environment potentially through where the wind farms are located.

Wind power is also is a clean energy source, and operation does not produce carbon dioxide, sulfur dioxide, mercury, particulates, or any other type of air pollution, as do conventional fossil fuel power sources.

There is a huge amount of wind power available. Wind’s long-term theoretical potential is much greater than current world energy consumption. The key is economically harvesting this abundant energy source. While there is initially a high cost to establishing wind farms, their fuel costs are close to zero and maintenance costs are relatively low.

Issues surrounding wind power

Irregularity of energy supply

Because so much power is generated by higher windspeed, much of the average power available to a windmill comes in short bursts, so additional power output cannot be supplied in response to load demand. Wind power is therefore used best to supplement other forms of energy supply unless efficient ways to store excess energy are developed.

Siting of wind farms

The location of wind farms is crucial for a near constant flow of non-turbulent wind throughout the year. Each turbine needs to be spaced away from others, so wind farms often need large areas and may be considered an eye sore. Onshore turbine installations in hilly or mountainous regions tend to be on ridgelines generally three kilometers or more inland from the nearest shoreline so they are often highly visible. Wind farm siting can sometimes be highly controversial, particularly as the hilltop, often coastal sites preferred are often picturesque and environmentally sensitive (for instance, having substantial bird life). Local residents in a number of potential sites have strongly opposed the installation of wind farms, and political support has resulted in the blocking of construction of some installations.

Near-Shore turbine installations are generally considered to be within a zone that is on land three kilometers of a shoreline and on water within ten kilometers of land. Wind speeds in these zones share wind speed characteristics of both onshore wind and offshore wind depending on the prevailing wind direction. Common issues that are shared within near-shore wind development zones are aviary (including bird migration and nesting), aquatic habitat, transportation (including shipping and boating) and visual aesthetics amongst several others.

Offshore wind development zones are generally considered to be ten kilometers or more from land. Offshore wind turbines cause less aesthetic controversy since they often cannot be seen from the shore. However, offshore turbines are in many cases less accessible and offshore conditions in oceans or seas can be harsh, abrasive, and corrosive, thereby increasing the costs of operation and maintenance compared to onshore turbines.

Scalability of wind farms

A key issue debated about wind power is its ability to scale to meet a substantial portion of the world’s energy demand. A key issue in the application of wind energy to replace substantial amounts of other electrical production is intermittency. At present, it is unclear whether wind energy will eventually be sufficient to replace other forms of electricity production, but this does not mean wind energy cannot be a significant source of clean electrical production on a scale comparable to or greater than other technologies, such as hydropower.

A significant part of the debate about the potential for wind energy to substitute for other electric production sources is the level of penetration. With the exception of Denmark, no countries or electrical systems produce more than 10% from wind energy, and most are below 2%. While the feasibility of integrating much higher levels (beyond 25%) is debated, significantly more wind energy could be produced worldwide before these issues become significant. In Denmark, wind power now accounts for close to 20% of electricity consumption and a recent poll of Danes show that 90% want more wind power installed.

Possibilities for the future of wind power

Wind turbines might be flown in high speed winds at altitude, although no such systems currently exist in the marketplace. An Ontario company, Magenn Power, Inc., is attempting to commercialize tethered aerial turbines suspended with helium.

The Italian project called “Kitegen” uses a prototype vertical-axis wind turbine. It is an innovative plan (still in the construction phase) that consists of one wind farm with a vertical spin axis, and employs kites to exploit high-altitude winds.

The Kite Wind Generator (KWG) or KiteGen is claimed to eliminate all the static and dynamic problems that prevent the increase of the power (in terms of dimensions) obtainable from the traditional horizontal-axis wind turbine generators. According to its developers, a one gigawatt installation will be 1/40 the cost of the corresponding nuclear powerplant.

Theoretical potential and feasibility of wind power

Wind’s long-term theoretical potential is much greater than current world energy consumption. The most comprehensive study to date found the potential of wind power on land and near-shore to be 72 TW (~54,000 Mtoe), or over five times the world’s current energy use and 40 times the current electricity use.

The potential takes into account only locations with Class 3 (mean annual wind speeds = 6.9 m/s at 80 m) or better wind regimes, which includes the locations suitable for low-cost (0.03–0.04 $/kWh) wind power generation and is in that sense conservative. It assumes 6 turbines per square km for 77-m diameter, 1,5 MW turbines on roughly 13% of the total global land area (though that land would also be available for other compatible uses such as farming). This potential assumes a capacity factor of 48% and does not take into account the practicality of reaching the windy sites, of transmission (including ‘choke’ points), of competing land uses, of wheeling power over large distances, or of switching to wind power.

To determine the more realistic technical potential it is essential how large a fraction of this land could be made available to wind power. In the 2001 IPCC report, it is assumed that a use of 4% – 10% of that land area would be practical. Even so, the potential comfortably exceeds current world electricity demand.

Although the theoretical potential is vast, the amount of production that could be economically viable depends on a number of exogenous and endogenous factors, including the cost of other sources of electricity and the future cost of wind energy farms.

Offshore resources experience mean wind speeds ~90% greater than that of land, so offshore resources could contribute about seven times more energy than land. This number could also increase with higher altitude or airborne wind turbines. To meet energy demands worldwide in the future in a sustainable way, a much larger number of turbines than have been currently installed will be required.

Land use and siting of wind farms

Wind turbines should ideally be placed about ten times their diameter apart in the direction of prevailing winds and five times their diameter apart in the perpendicular direction for minimal losses due to wind park effects. As a result, wind turbines require roughly 0.1 square kilometers of unobstructed land per megawatt of nameplate capacity. A wind farm that produces the energy equivalent of a conventional 2 GW power plant might have turbines spread out over an area of approximately 200 square kilometers.

Areas under onshore and near-shore windfarms can be used for farming, and are protected from further development. Although there have been installations of wind turbines in urban areas (such as Toronto’s exhibition place), these are generally not used. Buildings may interfere with wind, and the value of land is likely too high if it would interfere with other uses to make urban installations viable. Installations near major cities on unused land, particularly offshore for cities near large bodies of water, may be of more interest. Despite these issues, Toronto’s demonstration project demonstrates that there are no major issues that would prevent such installations where practical, although non-urban locations are expected to predominate.

Offshore locations, such as that being developed on a large underwater plateau in eastern Lake Ontario by Trillium Power use no land per and avoid known shipping channels. However, that is generally not the norm for most offshore locations. Some offshore locations are uniquely located close to ample transmission and high load centers however that is not the norm for most offshore locations. Most offshore locations are at considerable distances from load entrees and may face transmission and line loss challenges.

Impact on wildlife of wind farms

Onshore and near-shore studies show that the number of birds killed by wind turbines is negligible compared to the number that die as a result of other human activities such as traffic, hunting, power lines and high-rise buildings and especially the environmental impacts of using non-clean power sources. For example, in the UK, where there are several hundred turbines, about one bird is killed per turbine per year; 10 million per year are killed by cars alone. In the United States, onshore and near-shore turbines kill 70,000 birds per year, compared to 57 million killed by cars and 97.5 million killed by collisions with plate glass. Another study suggests that migrating birds adapt to obstacles; those birds which don’t modify their route and continue to fly through a wind farm are capable of avoiding the large offshore windmills, at least in the low-wind non-twilight conditions studied. In the UK, the Royal Society for the Protection of Birds (RSPB) concluded that “The available evidence suggests that appropriately positioned wind farms do not pose a significant hazard for birds.” It notes that climate change poses a much more significant threat to wildlife, and therefore supports wind farms and other forms of renewable energy.

Some onshore and near-shore windmills kill birds, especially birds of prey. More recent siting generally takes into account known bird flight patterns, but some paths of bird migration, particularly for birds that fly by night, are unknown although a 2006 Danish Offshore Wind study showed that radio tagged migrating birds traveled around offshore wind farms. A Danish survey in 2005 (Biology Letters 2005:336) showed that less than 1% of migrating birds passing an oshore wind farm in Rønde, Denmark, got close to collision, though the site was studied only during low-wind non-twilight conditions. A survey at Altamont Pass, California, conducted by a California Energy Commission in 2004 showed that onshore turbines killed between 1,766 and 4,721 birds annually (881 to 1,300 of which were birds of prey). Radar studies of proposed onshore and near-shore sites in the eastern U.S. have shown that migrating songbirds fly well within the reach of large modern turbine blades. In Australia, a proposed onshore/near-shore wind farm was canceled before production because of the possibility that a single endangered bird of prey was nesting in the area.

An onshore/near-shore wind farm in Norway’s Smøla islands is reported to have destroyed a colony of sea eagles, according to the British Royal Society for the Protection of Birds. The society said turbine blades killed nine of the birds in a 10 month period, including all three of the chicks that fledged that year. Norway is regarded as the most important place for white-tailed eagles.

The numbers of bats killed by existing onshore and near-shore facilities has troubled even industry personnel. A study in 2004 estimated that over 2200 bats were killed by 63 onshore turbines in just six weeks at two sites in the eastern U.S. This study suggests some onshore and near-shore sites may be particularly hazardous to local bat populations and more research is urgently needed. Migratory bat species appear to be particularly at risk, especially during key movement periods (spring and more importantly in fall). Lasiurines such as the hoary bat (Lasiurus cinereus), red bat (Lasiurus borealis), and the semi-migratory silver-haired bats (Lasionycteris noctivagans) appear to be most vulnerable at North American sites. Almost nothing is known about current populations of these species and the impact on bat numbers as a result of mortality at windpower locations. Offshore wind sites 10 km or more from shore do not interact with bat populations.

Asthetics of wildlife of wind farms

Recorded experience that onshore and near-shore wind turbines are noisy and visually intrusive creates resistance to the establishment of land-based wind farms in many places. Moving the turbines far offshore (10 km or more) mitigates the problem, but offshore wind farms may be more expensive and transmission to on-shore locations may present challenges in many but not all cases.

Some residents near onshore and near-shore windmills complain of “shadow flicker,” which is the alternating pattern of sun and shade caused by a rotating windmill casting a shadow over residences. Efforts are made when siting onshore and near-shore turbines to avoid this problem. Large onshore and near-shore wind towers require aircraft warning lights, which create light pollution at night, which bothers humans and can disrupt the local ecosystem. Complaints about these lights have caused the FAA to consider allowing a less than 1:1 ratio of lights per turbine in certain areas.

Improvements in blade design and gearing have quietened modern turbines to the point where a normal conversation can be held underneath one. Newer wind farms have more widely spaced turbines due to the greater power of the individual wind turbines, and so look less cluttered. The aesthetics of onshore and near-shore wind turbines have been compared favorably to those of pylons from conventional power stations. Offshore sites have on average a considerably higher energy yield than onshore sites, and generally cannot be seen from the shore even on the clearest of days.

Click here to go to the home page www.climatechange.110mb.com

This information is licensed under the GNU Free Documentation. It is derivative of articles on Climate Change, Global Warming and related environmental issues at http://en.wikipedia.org