Wind Energy | Frequently Asked Questions

Wind energy is ever present and produced in varying power due to the movement of air between an unevenly heated atmosphere and the irregular surface of the earth. The power of wind lets it exert force, create movement, and transfer energy to elements within the environment.

We use the wind when sailing , wind surfing , flying kites and gliders. But it was not until about 30 years ago wind power began to be used for commercial production of electricity. The principle of today's wind turbines, however, are the same as in the windmills and watermills already used thousands of years ago.

A wind turbine produces electricity by using the kinetic or moving energy of wind to create motion. When there is a satisfactory level of power in the wind it can exert a force, causing a the rotor to spin which when coupled to a generator converts the rotation into electricity.

A wind turbine operates on a simple principle: The wind turns the blades, spins a 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.

The electricity produced is collected through underground cables that connect each turbine to a substation, where the power is transferred to the local power distribution network to be used by local homes and businesses, or enters the national power network where it is rerouted to areas of high electricity demand, such as: urban centres.

The amount of electricity that an individual wind turbine is able to generate depends on its size, the wind speed and the efficiency rating of the turbine make, and model. Onshore wind turbines currently used in commercial electricity generation can produce somewhere between 0.5 MW, and 3.45 MW powering roughly 350 to over 2,200 households per year.

Within Ireland and the United Kingdom, there are currently 1,180 wind farms with a potential generation capacity of 11,508MW enough to power almost 7.5 million households across both markets.

Wind turbines produce electricity approximately 85% of the time. The other 15% of the time they are not turning for reasons, such as: very low wind speeds, very high wind speeds, and maintenance/repair work.

Wind turbines operate automatically, self-starting when the wind speed reaches an average about three to five m/s (about 10 mph), equal to that of a gentle breeze which otherwise would only be strong enough to rustle leaves and light twigs. The output increases linearly with the wind speed until the wind speed reaches 13 to 14 m/s (about 30 mph) equal to that of a strong breeze. At this point, the wind turbine will reach it’s maximum generating capacity.

If the average wind exceeds the maximum operational limit of 25m/s, equal to that of a storm, the wind turbine shuts down by the feathering of blades, in order to avoid excessive wear-and-tear. Upon the average wind speed dropping back below 25 m/s the wind turbine will restart.

After six to seven months, a wind turbine will have produced as much energy as it has gone into constructing it.

Wind turbines come in many different sizes, largely varying between producers and models and dependant upon the amount of energy that it is required to produce.

A wind turbines total height determined by the height of its tower and the length of its rotor blade, which is normally about half of the tower's height.

Currently, tower components designed for commercial use can be up to 120 metres in height, while rotor components can have a radius of up to 70 metres. Taking this into account a wind turbine has the potential to be 190 metres tall from foundation level to the tip of the highest rotor blade.

There are a number of indicators we use to identify a site which may be suitable for wind farm development:

  • Estimates of the wind speeds in the area predict that there is sufficient wind to generate a significant amount of energy;
  • There is space for turbines in terms of ensuring appropriate distances from the houses;
  • There is excellent vehicle access to the site;
  • There is a suitable connection to the grid network nearby, which could carry the electricity that would be generated by a wind farm to homes and businesses.

Wind farm construction consists of turbine foundations, site access roads and an electrical sub-station; the installation of wind turbines; and the connection of the wind farm site to the existing electricity grid via an overhead line or underground cable.

It is usually a very short process - between 12 and 18 months dependant upon the size of the wind farm development.

See in detail what went into the construction of our newest wind farm: Woodhouse.

Wind farms are expected to have an operational lifespan of 20-25 years, after which time the site will be reviewed and assessed to determine whether the wind farm may be repowered or otherwise decommissioned.

Decommissioning entails the dismantling the above ground equipment and then removing it from the site, and the restoration of the land and surrounding areas to their previous condition. Repowering entails the installation of new, more efficient wind turbines within the wind farm site.

A wind turbine produces two different types of noise. A mechanical noise from the internal components of a wind turbine, and an aerodynamic noise from the rotor blades passing through the air.

The noise emitted from wind turbines has been reduced significantly over the last 10 to 15 years. Modern design has drastically reduced the noise of mechanical components so that the most audible sound is that of the wind interacting with the rotor blades. Even in quiet rural areas, the sound of the blowing wind is often louder than the turbines.

It is the duty of ESB to demonstrate during the planning process noise levels of our turbines will not adversely affect local residents. The studies completed during this period will be used to design each new wind farm so noise levels at nearby residential homes do not exceed national planning guidelines. Currently in Ireland and the United Kingdom, guidelines in relation to wind turbine noise levels are set at: “35 and 45 decibels dependant on the time of day and the level of background noise”, in line with international best practices.

ESB additionally undertakes regular noise monitoring so as to ensure our operational wind farms remain compliant with the noise limits.

Modern wind turbines can generate noise across the frequency range of human hearing, and even some of which occur below the level of human hearing can detect (20Hz to 20,000Hz), such as: Low Frequency Noise (LFN) or Infrasound. Both terms refer to noises which occur in the range of 20 Hz down to 0.001 Hz; below what the human ear can comprehend.

These noises are generated naturally within the atmosphere which surrounds us, including: waterfalls, the crashing of waves against a coastline, or wind. However it can also be generated by a wide range of human-created sources, such as: industrial processes, motor vehicles, air conditioning or wind farms.

Studies have confirmed that LFN and Infrasound levels produced by wind farms are below accepted thresholds, and are less than that caused through naturally occurring means. (British Wind Energy Association/Renewables UK, 2005)

There is currently no scientific data to suggest that the levels of LFN or Infrasound emitted by wind turbines make humans sick. Research to date has concluded that there are no plausible links to adverse health from the noise levels emanating from wind turbines.

Shadow flicker is the name given to a phenomenon caused when the sun is behind the turbine blades as it rises or sets, casting a moving shadow over a small opening in a building such as a window, creating a flickering effect within the building. This can only affect properties within a few hundred metres of the turbines.

A shadow flicker assessment forms part of every planning application we submit informing us if any properties will be affected. Where it is expected to occur we install solar sensors on the top of the turbine, which will slow or shut down the turbine for a period of time, therefore mitigating the effect of the phenomenon from turbines. Employing this mitigation measure can ensure that no residents living near a wind farm experience shadow flicker.

The balance of scientific evidence and human experience to date clearly concludes that wind turbines are not harmful to human health – in fact, wind energy reduces harmful air emissions and creates no harmful waste products when compared with other sources of electricity.

Wind Turbine Syndrome ("WTS") an alleged condition used to link wind farms with the health issues of individuals living in their vicinity. WTS is not accepted by the medical community. Commenting on the study, the NHS said:

"This study provides no conclusive evidence that wind turbines have an effect on health or are causing the set of symptoms described here as: Wind Turbine Syndrome. The study design was weak, the study was small and there was no comparison group."

In general, wildlife and wind farms happily co-exist. The RSPB in the UK, Northern Ireland and Republic of Ireland equivalent agree that wind farms in appropriate locations will have minimal impact on wildlife. With this in mind we assess every wind farm location via detailed environmental studies, and consult with relevant statutory and environmental bodies to ensure any potential impacts on wildlife are fully mitigated.

For example, where a proposed wind farm location is found to be in the flight routes of birds, and bats. Adequate turbine buffer distances would be incorporated into planning ensuring turbine blades are not in close proximity to these flight routes.

RSPB has stated on record that: “Climate change poses the single greatest long-term threat to birds and other wildlife, and the RSPB recognises the essential role of renewable energy in addressing this problem. Wind power has a significant role to play in the UK’s fight against climate change and we will work with Government and developers to ensure this outcome”

Additionally, wind turbines do not have any noticeable impact on livestock. Animals such as cattle, horses and sheep habitually graze around the wind turbines undisturbed.

It is possible, though rare, for operating wind turbines to interfere with TV and mobile reception. This mainly occurs with old TV aerials or in areas with weak signals. Potential problems are normally identified pre-construction and will be rectified.

There has been no evidence of actual negative impacts on tourism. For example, if we look at Scotland a country with in excess of 5,300MW of installed capacity. A Scottish Government report in 2008 demonstrated that wind farm developments have a minimal impact on tourism.

Of the visitors surveyed in the study, over 90% said that wind farms would have no impact on their decision to return to Scotland. 68% said they felt positive that a well-sited wind farm does not ruin the landscape, with a further 12% neutral about the statement.

Visit Scotland (2012) illustrated: “the presence of wind farms had no influence on decision making of the vast majority of tourists” . Wind farms in fact have the potential to encourage tourism to their surrounding areas by bringing improved transport routes, and funding the creation and improvement of infrastructure and tourist facilities.

Several studies from the United Kingdom by The Centre for Economics and Business Research (CEBR), The Institute of Chartered Surveyors, The House of Commons Library and RenewableUK conclude wind farms have very little or no impact on property values.

The studies observed when a wind farm is announced or begins construction there can be a slight effect on house prices, however, the problem does not persist once the wind farm is constructed. Local house prices in areas where there are wind farms continued to perform as would have been expected in the absence of wind farms.

There are no capital grants payable for onshore wind farms. At present in Ireland and the United Kingdom, the Renewables Obligation (RO) places an obligation on suppliers of electricity to source an increasing proportion of their electricity from renewable sources.

As a result of this a Renewables Obligation Certificate (ROC) is produced per unit of electricity produced. There is then a payment made to the generator of the renewable electricity due solely to the fact the electricity has been generated in an environmentally friendly way. All income from the wind farm (via the Renewables Obligation or otherwise) is directly proportional to the amount of electricity generated so that where no electricity is generated there is no income.

Onshore Wind, and other forms of renewable power, are given financial support through the RO system. Governments put these systems in place to provide incentives for firms to invest in renewable technology.

The ROC is designed to incentivise the adoption of renewable generation into the electricity generation market. Onshore wind energy is one of the most cost effective renewable energy sources and on this basis the ROC value, and therefore the payment received by generators, is lower than for more expensive technologies such as wave, tidal, solar and offshore wind.

In Ireland and the United Kingdom the ROC associated with onshore wind is expected to decrease and cease over the coming years as the cost of onshore wind decreases. In the UK, the amount paid to wind energy generators through the ROC was already reduced in the last year.

To learn more, check out IWEA’s and Renewable UK's websites: www.iwea.ie, www.windenergy.ie, and www.renewableuk.com.

ESB Educational Programmes

At ESB, we strongly believe in informing and educating people about the future of energy. We run various educational programmes for schools and other interest groups within the communities surrounding our wind farms.

These programmes, run by our qualified engineers, range from wind farm tours to off-site presentations and workshops, covering all aspects of the wind industry.

If you would like to learn more about our wind farm educational programmes, email paul.lally@esb.ie