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Wind Turbines
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Wind Turbine FAQ

1. How exactly does a wind turbine convert wind into electricity?
In simple terms, the wind turbine produces electricity by using the kinetic or moving energy of wind to create motion. The force of the wind causes the turbine blades to rotate and this in turn rotates a drive shaft. This is made possible by the special aerodynamic design of the blades which results in the speed of the wind leaving the turbine being less than the speed of the wind approaching it creating a spinning effect. This rotating motion of the drive shaft fed through a gearbox delivers the motion required for a generation unit to produce electricity by using the motion to create a magnetic field and generate an electrical current.


2. 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 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.


3. How much of the time do wind turbines produce electricity?
A modern wind turbine produces electricity 70-85% of the time, but it generates different outputs dependent on wind speed. Over the course of a year, it will generate about 31% of the theoretical maximum output. This is known as its load or capacity factor. The load factor of conventional power stations is on average 50%.


4. What are wind turbines made from?
The larger commercial turbine towers are made of steel, generally painted light grey. The turbine blades are usually made of a matrix of glass-fibre reinforced polyester or wood-epoxy or a similar composite fabrication technique. They are generally painted light grey because this is the colour which is most inconspicuous under most lighting conditions. The finish is matt, to reduce the potential for excessive light reflection. A "nacelle" or enclosure is where the generator and gearbox are housed.


5. How big are wind turbines?
Wind turbines come in many different sizes, depending on the amount of energy that it is required to produce. The larger the turbine, then (generally) the greater the amount of electricity produced. For most modern commercial turbines the tubular steel towers range from about 100 to 300 feet (30 to 90 metres) in height. In terms of rotor diameter, large modern wind turbines have rotor diameters ranging up to 100 meters while smaller machines (around 30 meters) are typical in developing countries.


6. How strong does the wind have to blow for the wind turbines to work?
Wind turbines typically start operating at wind speeds around Beaufort Force 3 (which is around 3-5 metres per second (m/s), or 8-12 miles per hour (mph). Turbines reach maximum power output at Beaufort 5 (around 11-14 m/s or 25-30 mph). At very high wind speeds, i.e. Beaufort Storm Force 10 winds, (around 24 m/s or 55 mph) or greater the wind turbines shut down to prevent excessive wear and tear. Since winds of this strength occur only for a handful of hours per year, very little energy is lost in high wind periods.
Enerpower can assist you by measuring your wind speed


7. How fast do the blades turn?
Large scale wind turbines blades typically rotate at somewhere between 10-25 revolutions per minute. In the past, most wind turbines rotated at a constant speed, however, most modern turbines now operate at variable speed, for greater efficiency.


8. 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. In May 2000, the very first of the mass-produced turbines celebrated its 20th birthday. The Vestas 30 kW machine has operated steadily throughout its lifetime, with none of the major components needing to be replaced.


9. 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.


10. How much space does a wind turbine require?
There are different spacing requirements for different types of 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.


11. Could Wind Energy provide 100% of Ireland's energy needs in the future?
While it would be technically possible to install enough wind turbines to meet the future annual total electricity demand of Ireland, given the current technological limitations this would be highly unlikely. The problem is that while wind energy created might meet total demand over the year, Ireland is a relatively small meteorological area and there are going to be times where electricity generation is extremely low due to very load wind speeds across the country and similarly periods where generation exceeds demand. The only way in which one might solve this problem would be to have the national grid fully integrated with a much larger electrical grid such as the UK or Europe, where we could import electricity in times of shortage and, and export energy in times of surplus. Even then, the connections required to safely import periodically the majority of the country's electrical demand would make the scenario highly unlikely. The most likely long term sustainable solution to Ireland electrical would be the contribution provided by other renewable energies such as wave, tidal and bio-mass in addition to wind energy


12. 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.


13. What happens when the wind stops blowing?
When the wind stops blowing, electricity continues to be provided by other forms of generation, such as gas or coal-fired power plants. This is made possible by sophisticated generation planning and the interconnection of power plants through the national grid. In order to ensure security of supply the system has to be able to cope if one of these goes out of action. The all-island grid study has shown that it is possible to deliver at least 42% of Ireland's energy from renewable sources.


14. How safe is wind energy?
In terms of electricity generation, wind energy is one of the safest technologies around and has zero fuel risk compared to other higher risk operations such as nuclear power plants. While the construction and maintenance of wind turbines, involves a higher level of risk similar to that of any other power generation facility, it is a matter of record that no passive member of the public has ever been directly 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.


15. Do wind turbines frighten livestock?
The evidence suggests that sheep, cows and horses are not disturbed by wind turbines. Wind farming is popular with farmers, because their land can continue to be used for growing crops or grazing livestock.


16. 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 in the planning regulations on wind turbines 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.

17. Do you need planning permission for a wind turbine?
Yes, all large scale wind turbines will have to go through the planning process. With regard to both domestic and industrial micro generation however, planning exemptions have been published by the Department of the Environment have recently come into effect. These exemptions cover micro generation units with a maximum height of 10 meters for domestic turbines and units with a maximum height of 20 meters for businesses. The local county council is the authority to which you need to apply to for planning permission. Your application should include both a site layout map, a site location map, drawings of the planned turbines include their height and rotor diameter, together with evidence of a site notice and notification in the required national and/or local papers.
Enerpower are experienced at wind turbine planning applications


Faithlegg Co. Waterford. Tel/Fax: 051 364054 E-Mail: info@powerpl an.ie Web Site: www.powerpl an.i e
VAT No. IE 6419788K Reg. No. 399788
Frequently Asked Questions
How exactly does a wind turbine convert wind into electricity?
In simple terms, the wind turbine produces electricity by using the kinetic or moving energy of wind to create motion. The
force of the wind causes the turbine blades to rotate and this in turn rotates a drive shaft. This is made possible by the
special aerodynamic design of the blades which results in the speed of the wind leaving the turbine being less than the
speed of the wind approaching it creating a spinning effect. This rotating motion of the drive shaft fed through a gearbox
delivers the motion required for a generation unit to produce el ectricity by using the motion to create a magnetic fi eld and
generate an elect rical current.
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 specifi cally designed turbine is able to convert wind energy to electrical energy.
Currently the largest wind turbine 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 el ectrical 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)
How much of the time do wind turbines produce electricity?
A modern wind turbine produces electricity 70-85% of the time, but it generates different outputs dependent on wind speed.
Over the course of a year, it will generate about 31% of the theoretical maximum output. This is known as its load or
capacity factor. The load factor of conventional power stations is on average 50%.
What are wind turbines made of?
The larger commercial turbine towers are made of steel, generally painted light grey. The turbine blades are usually made
of a matrix of glass-fiber reinforced polyester or wood-epoxy or a similar composite fabri cation technique. They are
generally painted light grey because this is the colour which is most inconspicuous under most lighting conditions. The
finish is matt, to reduce the potential for excessive light refl ection. A "nacelle" or enclosure is where the generator and
gearbox are housed.
How big are wind turbines?
Wind turbines come in many di fferent sizes, depending on the amount of energy that it is required to produce. The larger
the turbine, then (generally) the greater the amount of el ectricity produced. For most modern commerci al turbines the
tubular steel towers range from about 100 to 300 feet (30 to 90 metres) in height. In terms of rotor diameter, large modern
wind turbines have rotor diamet ers ranging up to 100 meters while smaller machines (around 30 meters) are typical in
developing countries.
Faithlegg Co. Waterford. Tel/Fax: 051 364054 E-Mail: info@powerpl an.ie Web Site: www.powerpl an.i e
VAT No. IE 6419788K Reg. No. 399788
How strong does the wind have to blow for the wind turbines to work?
Wind turbines typically start operating at wind speeds around Beaufort Force 3 (which is around 3-5 metres per second
(m/s), or 8-12 miles per hour (mph)). Turbines reach maximum power output at Beaufort 5 (around 11-14 m/s or 25-30
mph). At very high wind speeds, i.e. Beaufort Storm Force 10 winds, (around 24 m/s or 55 mph) or great er the wind
turbines shut down to prevent excessive wear and t ear. Since winds of this strength occur only for a handful of hours per
year, very little energy is lost in high wind periods.
How fast do the blades turn?
Large scale wind turbines blades typically rotate at somewhere between 10-25 revolutions per minute. In the past, most
wind turbines rot ated at a const ant speed, however, most modern turbines now operat e at variable speed, for greater
effici ency.
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. In May
2000, the very first of the mass-produced turbines celebrated its 20th birthday. The Vestas 30 kW machine has operated
steadily throughout its lifetime, with none of the major components needing to be replaced.
How efficient are wind turbines?
The theoretical maximum energy which a wind turbine can ext ract 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.
How much space does a wind turbine require?
There are di fferent spacing requirements for di fferent types of 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 kilometer, 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.
Faithlegg Co. Waterford. Tel/Fax: 051 364054 E-Mail: info@powerpl an.ie Web Site: www.powerpl an.i e
VAT No. IE 6419788K Reg. No. 399788
Could Wind Energy provide 100% of Ireland's energy needs in the future?
While it would be technically possible to install enough wind turbines to meet the future annual total electricity demand of
Ireland, given the current technological limitations this would be highly unlikely. The problem is that while wind energy
created might meet total demand over the year, Ireland is a relatively small meteorological area and there are going to be
times where electri city generation is extremely low due to very load wind speeds across the country and similarly periods
where generation exceeds demand.
The only way in which one might solve this problem would be to have the national grid fully integrated with a much larger
electrical grid such as the UK or Europe, where we could import electricity in times of shortage and, and export energy in
times of surplus. Even then, the connections required to safely import periodically the majority of the count ry's electrical
demand would make the scenario highly unlikely. The most likely long term sustainable solution to Ireland electrical would
be the contribution provided by other renewabl e energi es such as wave, tidal and bio-mass in addition to wind energy
If possible, how many wind turbines would that require?
To answer this question we construct an estimate given the latest available information, combined with a number of
assumptions. The 2008 Eirgrid Generation Adequacy Report, returns a median demand forecast for the year 2008 of 29,891
GWh, given this demand we shall construct the figures on the basis of a 3 MW turbine (the largest commerci ally available
onshore turbine), with a 31% load factor.
Given this demand and these assumptions, as few as around 3,500 wind turbines could produce as much energy as Ireland
uses in a year. However, given that electricity normally has to be used as soon as it is generated, in low wind periods, there
would be a need for alternative generation. In order to deliver the cheapest electri city to the consumer, these alternative
generation plants should be flexible power stations, rather than the large, inflexible and expensive base load plant which
has recently been built in Ireland.
At other periods (e.g. a summer night when demand is low), there may be excess wind generation. However, this excess
energy could be stored at pumped electricity storage facilities such as Turlough Hill, exported (e.g. on the new
interconnector planned) or demand could be encouraged to move around to avail of this “ free” energy (as encouraged by
the new SEM pool market structures).
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 fi red
power stations and cheaper than new nucl ear power. If we were look at the variabl e unit cost of el ectricity 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 el ectricity 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.
Faithlegg Co. Waterford. Tel/Fax: 051 364054 E-Mail: info@powerpl an.ie Web Site: www.powerpl an.i e
VAT No. IE 6419788K Reg. No. 399788
What happens when the wind stops blowing?
When the wind stops blowing, electricity continues to be provided by other forms of generation, such as gas or coal-fi red
power plants. This is made possible by sophisticated generation planning and the interconnection of power plants through
the national grid. In order to ensure security of supply the system has to be able to cope i f one of these goes out of action.
The all-island grid study has shown that it is possible to deliver at least 42% of Ireland's energy from renewable sources.
How safe is wind energy?
In terms of el ectricity generation, wind energy is one of the safest technologies around and has zero fuel risk compared to
other higher risk operations such as nuclear power plants. While the construction and maintenance of wind turbines,
involves a higher level of risk similar to that of any other power generation facility, it is a matter of record that no passive
member of the public has ever been directly injured during the normal operation of a wind turbine, with over 25 years
operating experi ence and with more than 70,000 machines installed around the world.
Do wind turbines frighten livestock?
The evidence suggests that sheep, cows and horses are not disturbed by wind turbines. Wind farming is popular with
farmers, because their land can continue to be used for growing crops or grazing livestock.
Are wind turbines noisy?
Wind turbines are not noisy. The evolution of wind farm technology over the past decade has rendered mechani cal noise
from turbines almost undetectable with the main sound being the aerodynamic swoosh of the blades passing the tower.
There are strict guidelines in the planning regulations on wind turbines 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. Why not visit a wind farm and
experience it for yoursel f?
Do you need planning permission for a wind farm?
Yes, all large s cale wind farms will have to go through the planning process. With regard to both domestic and industrial
micro generation however, planning exemptions have been published by the Department of the Environment have recently
come into effect. These exemptions cover micro generation units with a maximum height of 10 meters for domestic
turbines and units with a maximum height of 20 met ers for businesses. The local county council is the authority to which
you need to apply to for planning permission. Your application should include both a site layout map, a site location map,
drawings of the pl anned turbines include their height and rotor diameter, together with evidence of a site notice and
notification in the required national and/or local papers.