 |
Wind |
|---|
1. How much electricity can a wind turbine produce?
2. How efficient are wind turbines?
3. How much space does a wind turbine require?
4. How much does it cost to make electricity from the wind?
5. What are the job opportunities in the Wind Industry?
6. How long do wind turbines last?
7. Are wind turbines noisy?
8. Do wind turbines produce low frequency noise?
9. Do wind turbines frighten livestock?
10. How safe is wind energy?
11. Does wind farming affect tourism?
12. I've heard that wind energy doesn't really reduce pollution, because other, fossil-fired generating units have to be kept running on a standby basis in case the wind dies down. Is this true?
13. What about turbines throwing blades, or ice? Is wind energy dangerous to the public?
14. Why not develop wind farms on mountains that are already being used for ski resorts?
15. I've heard that stray voltage from wind power plants can be transmitted through the ground, disturbing or harming livestock. Is this true?
16. Will a wind project interfere with electromagnetic transmissions such as radio, television, or cell-phone signals?
17. Will a wind project interfere with radar?
1. How much electricity can a wind turbine produce?
The amount of electricity that a single turbine is able to produce depends on its size, the wind speed and the efficiency with which that specifically designed turbine is able to convert wind energy to electrical energy.
Currently the largest wind turbine(March 2010) in manufacture has a 6 MW capacity. Given a 31% load factor it has the potential to produce roughly 16,300 MWh in a year (6 MW*8760*0.31). On average, this is enough to supply the electrical needs of around 2,700 households for the year, (16,300/5.93) and would satisfy the total energy needs of 607 households annually. (16,300/26.84)
2. How efficient are wind turbines?
The theoretical maximum energy which a wind turbine can extract from the wind blowing across it is just under 60%, known as the Betz limit. As the wind turbine extracts energy from the air flow, the air is slowed down, which causes it to spread out. Albert Betz, a German physicist, determined in 1919 that a wind turbine can at most extract 59% of the energy that would otherwise flow through the turbine's cross section.
The Betz limit applies regardless of the design of the turbine. However is should be noted that the meaning of efficiency in technological terms is a redundant concept to apply to wind energy, where the fuel is free. A more pressing concern is the challenge to improve productivity by removing logistical, financial and institutional barriers in order to bring the price of wind energy down.
3. How much space does a wind turbine require?
There are different spacing requirements for different types fo turbines, so the amount of space required by a wind farm depends on the number and type of turbine being deployed. A typical wind farm of 4-5, V90 3MW turbines might extend over an area of 1 square kilometre, but only 1% of the land area would be used to house the turbines, electrical infrastructure and access roads; the remainder can be used for other purposes, such as farming or as natural habitat.
-
4. How much does it cost to make electricity from the wind?
Wind energy is one of the cheapest of the renewable energy technologies. It can easily compete with new clean coal fired power stations and cheaper than new nuclear power. If we were look at the variable unit cost of electricity production then we would interpret the cost as being zero, i.e. there are no fuel or input costs, the energy itself is free.
However in reality we interpret the actual cost per unit of electricity as represented by the long term spread per unit allocation of the very high initial capital costs, coupled with the day to day running of the wind farm e.g. administrative and maintenance costs.
-
5. What are the job opportunities in the Wind Industry?
There are many opportunities for employment with in the industry. In terms of staff on site, wind farms require qualified electrical and mechanical engineers to oversee the operation of the turbines and the internal electrical system, as well as computational analysts to assess the projected generation output systems in terms of the constant updating of notification of generation ability to the grid operator.
There are also the administrative job's created for the companies involved in the industry. The next number of years will see a sharp rise in employment opportunities. Up to 16,000 new jobs could be created with the explosion of wind industry investment in the process of delivering on Ireland's 40% electricity from renewables target by 2020.
6. How long do wind turbines last?
A wind turbine typically lasts around 20-25 years. During this time, as with a car, some parts may need replacing.
The very first of the mass-produced turbines celebrated its 20th birthday in May 2000. The Vestas 30kW machine has operated steadily throughout its lifetime, with none of the major components needing to be replaced.
7. Are wind turbines noisy?
Wind turbines are not noisy. The evolution of wind farm technology over the past decade has rendered mechanical noise from turbines almost undetectable with the main sound being the aerodynamic swoosh of the blades passing the tower. There are strict guidelines on wind turbines and noise emissions to ensure the protection of residential amenity. It is possible to stand underneath a turbine and hold a conversation without having to raise your voice. As wind speed rises, the noise of the wind masks the noise made by wind turbines.
For more information, read the facts about noise from wind turbines or why not visit a wind farm and experience it for yourself.
Click here to download The Assessment and Rating of Noise from Wind Farms, produced by ETSU for the DTI
8. Do wind turbines produce low frequency noise?
There is always low frequency noise present in any ambient quiet background and it can be produced by a variety of man-made sources, including machinery and transport and natural sources such as the sea, wind and thunder. It has been repeatedly shown by measurements of wind turbine noise undertaken in the UK, Denmark, Germany and the USA over the past decade, and accepted by experienced noise professionals, that the levels of low frequency noise and vibration radiated from modern, upwind configuration wind turbines are at a very low level, so low that they lie below the threshold of perception.
Read BWEA's full report on Low Frequency Noise and Wind Turbines.
9. Do wind turbines frighten livestock?
Wind farming is popular with farmers, because their land can continue to be used for growing crops or grazing livestock. Sheep, cows and horses are not disturbed by wind turbines.
The first wind farm built in the UK, Delabole, has a stud farm and riding school, and the farmer, Peter Edwards, often rides around the wind farm on his horse.
10. How safe is wind energy?
Wind energy is one of the safest energy technologies. It is a matter of record that no member of the public has ever been injured during the normal operation of a wind turbine, with over 25 years operating experience and with more than 70,000 machines installed around the world.
11. Does wind farming affect tourism?
There is no evidence to suggest this. The UK's first commercial wind farm at Delabole received 350,000 visitors in its first ten years of operation. A MORI poll in Scotland showed that 80% of tourists would be interested in visiting a wind farm. Furthermore, wind farm developers are often asked to provide a visitor centre, viewing platforms and rights of way to their sites. Find out more in an overview of tourism and wind energy.
No. It is true that other generating plants have to be available to the power system's operator to supply electricity when the wind is not blowing. However, the wind does not just start and stop. Typically, wind speeds increase gradually and taper off gradually, and the system operator has time to move other plants on and off line (start and stop them from generating) as needed--the fluctuations in wind plant output change more slowly than do the changes in customer demand that a utility must adjust to throughout the day. Studies indicate that for a 100-megawatt wind plant, only about 2 megawatts of conventional capacity is needed to compensate for changes in wind plant output.
Also, whenever the wind is blowing, it displaces the most expensive conventional power plant that is generating. Typically, this tends to be the oldest and dirtiest gas plants on a utility system, but in some parts of the country (notably the mid-Atlantic states such as Maryland, West Virginia, or Virginia), wind power may displace coal.
The U.S. Department of Energy puts it quite simply in its fact sheet Wind Energy Myths: "When wind is added to a utility system, no new backup is required to maintain system reliability." See http://www.nrel.gov/docs/fy05osti/37657.pdf
13. What about turbines throwing blades, or ice? Is wind energy dangerous to the public?
It has been estimated by a number of reliable sources that 50,000 Americans a year die from air pollution, of which about one-third is produced by power plants. By contrast, in 20 years of operation, the wind industry (which emits no pollutants) has recorded only one death of a member of the public--a German skydiver who parachuted off-course into an operating wind plant. Blade throws were common in the industry's early years, but are unheard of-today because of better turbine design and engineering. Ice throw, while it can occur, is of little danger because setbacks typically required to minimize noise (see above) are sufficient to protect against danger to the public, and because ice buildup slows a turbine's rotation and will be sensed by a turbine's control system, causing the turbine to shut down. One European group that has investigated the ice throw question recommends a setback of 1.5 times the sum of a turbine's hub height and its rotor diameter.
14. Why not develop wind farms on mountains that are already being used for ski resorts?
Because of the potential danger from ice throw. As the above answer indicates, ice throw does not present a danger except for the area close to turbines (that is, within a few hundred meters). At ski areas, however, turbines would typically have to be sited very close to operating lifts and trailheads, making ice throw a safety concern.
15. I've heard that stray voltage from wind power plants can be transmitted through the ground, disturbing or harming livestock. Is this true?
No. There is nothing different or unusual about managing the electricity flow from an operating wind plant. Standard electric wiring practices are adequate to prevent stray voltage from occurring.
16. Will a wind project interfere with electromagnetic transmissions such as radio, television, or cell-phone signals?
First, this is not a problem for modern small (residential) wind turbines. The materials used to make such machines are non-metallic (composites, plastic, wood) and small turbines are too small to create electromagnetic interference (EMI) by "chopping up" a signal.
Large wind turbines, such as those typically installed at wind farms, can interfere with radio or TV signals if a turbine is in the "line of sight" between a receiver and the signal source, but this problem can usually be easily dealt with improving the receiver's antenna or installing relays to transmit the signal around the wind farm. Use of satellite or cable television is also an option.
17. Will a wind project interfere with radar?
Yes. Radar is basically designed to filter out stationary objects and display moving ones, and moving wind turbine blades create radar echoes. It is possible to modify a radar installation to eliminate this problem, according to a consulting firm that has studied it for the British government-see http://www.bwea.com/aviation/ams_report.html. According to the study: "This study concludes that radars can be modified to ensure that air safety is maintained in the presence of wind turbine farms. Individual circumstances will dictate the degree and cost of modification required, some installations may require no change at all whilst others may require significant modification."
If a wind project is proposed near an airport or military airfield, this issue will likely require further technical investigation. The interference is generally limited to objects (airplanes) that are physically shadowed by the turbines (that is, very low-flying aircraft), so the further the turbines are from an airfield and the lower their altitude, the less interference should occur.
Resources:
American Wind Energy Association: http://www.awea.org
Australian Wind Energy Association: http://www.cleanenergycouncil.org.au/cec/home.html
British Wind Energy Association: http://www.bwea.com
Canadian Wind Energy Association: http://www.canwea.ca/
Irish Wind Energy Association: http://www.iwea.com
