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Works on site started in April 2013, with erection of turbines in late Summer 2013.
Planning permission was granted in 2009 to build two wind turbines on a former Shell Tank site in Avonmouth. Cabinet approval for the procurement of a wind farm developer to design, build, operate and maintain the turbines on behalf of the council was given in March 2010.
Prior to the announcement of the closure of Filton Airport, the council were working on a technical solution to mitigate any impacts of the turbines on Filton’s radar.
Following a period of negotiation, contracts were awarded on behalf of the council for the turbine supply and installation, operation and maintenance, and the civil and electrical works for a two turbine wind farm.
Reasons for the project
This project is about producing green electricity and reducing the city's carbon footprint. Large-scale wind power is the most highly developed, sophisticated technology and is the most cost-effective, achieving the best possible carbon dioxide savings per pound spent.
What are the benefits?
The wind turbine development will demonstrate:
- good use of council owned land;
- a flagship development by the council, setting a good example;
- a meaningful contribution to the city council's targets for installed capacity;
- active promotion of a sustainable energy future for Bristol and its communities;
- a good project for Avonmouth generating green energy in an industrialised setting.
How much electricity will they produce?
The Renewable UK website gives calculations for wind energy: A typical onshore turbine in the UK, rated at 2 MW, produces 5.256 million units of electricity each year, equal to 5,256 MWh. This is enough to meet the average annual electricity needs of 1,000 homes and prevent the emission of 2,000 tonnes of carbon dioxide per year.
Using the Renewable UK calculation, two wind turbines, rated at 2.5 MW each, are estimated to produce 13,140 MWh. Garrad Hassan have predicted that the two N100 turbines will produce 14,400 MWh of electricity per annum.
Size and dimensions of turbines
The type and size of the two wind turbines was chosen to fully harness the wind at the Avonmouth site and are 2.5 MW rated turbines.
The hub is the vertical support that holds the rotor blades and is 80 metres. The maximum tip height is 130 metres, (i.e. hub height plus height of one rotor).
A pre-planning public consultation attracted over 250 responses to the survey. Thank you to all of you who gave your views, and for those who attended the public events. Your views were valuable in helping us to prepare the planning application for this project. The analysis of these is detailed in the Statement of Community Involvement (pdf, 1.8 MB), which formed part of the planning submission.
The Local Government Improvement and Development site, working to develop and share good practice, has a case study on our wind turbine project.
The site and why we chose it
Specialist wind power consultants were given the task of selecting the best site from land in the area of the city with the most potential for wind power. The chosen site is a disused Shell oil tank site off Severn Road in Avonmouth. It was chosen for the following reasons:
- potential for two large-scale wind turbines;
- has very good wind exposure;
- brownfield site - a previously built-on site;
- is over 500m (0.3 miles) from the nearest home;
- existing road access;
- allows easy connection to the national grid;
- already owned by the council.
Ecotricity video showing the installation of their turbines at Avonmouth Docks
Here you can see indicative views of how the Avonmouth landscape could look with the two turbines with a tip height of 131 metres. The computer generated images show how the wind turbines would look from the locations specified.
Indicative view 1 - Severn Beach, A403 over M49
Indicative view 2 - Road bridge over M49, near Hallen Village
Indicative view 3 - A403 bridge over rail link
Avonmouth is the area within the Bristol City Council boundary which is the most exposed to wind and therefore has the most potential for wind power. The site of the proposed turbines, which was previously used for oil storage, is not subject to any nature conservation designation. The site is adjacent to the Severn Estuary, which is an internationally important site for various species and habitats, and is designated as a Special Protection Area (SPA), a proposed Special Area of Conservation (pSAC), a Ramsar site and a Site of Special Scientific Interest (SSSI).
Consultants undertook a comprehensive Environmental Impact Assessment (EIA) to assess any potential impacts of the proposed development. The EIA considered the potential for impacts on: ecology, telecommunications, archaeology, hydrology, surface water and flood risk, ground conditions, air traffic and marine navigation, noise and vibration, landscape and visual impact, air quality, traffic, transport and Public Rights of Way. Extensive ecological and bird studies were also undertaken and the results of these informed the Environmental Statement (ES), which formed part of the planning submission.
From the former British Wind Energy Association website, now Renewable UK.
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. The table below shows the noise generated by wind turbines compared with other everyday activities:
|Source / Activity||Indicative Noise Level, dB(A)|
|Threshold of pain||140|
|Jet aircraft at 250m||105|
|Pneumatic drill at 7m||95|
|Truck at 30mph at 100m||65|
|Busy general office||60|
|Car at 40mph at 100m||55|
|Wind Farm at 350m||35 - 45|
|Rural night time background||20 - 40|
|Threshold of hearing||0|
Reproduced from PPS22 Companion Guide.
Factors that reduce the noise level are: if the property is up-wind of the wind turbine; the ground is soft and non-reflective; and there are barriers or screening between the turbine and the property.
What is shadow flicker?
Only properties within 130 degrees either side of north, relative to the turbines can be affected at these latitudes in the UK. Turbines do not cast long shadows on their southern side. Shadows are cast in bright cloudless conditions. The further the observer is from the turbine the less pronounced the effect will be. This is because there are fewer times when the sun is low enough to cast a long shadow. When the sun is low it is more likely to be obscured by either cloud on the horizon or intervening buildings and vegetation. Also the centre of the rotor's shadow passes more quickly over the land reducing the duration of the effect. At distance, the blades do not cover the sun but only partly mask it, substantially weakening the shadow.
Overall the likely incidence of shadow flicker is assumed to be about 30% of the maximum potential, due to factors such as turbines not running, sun not shining brightly and times when the turbine disc is turned at right angles to a dwelling and thus not causing shadow flicker.
How long does it take for a turbine to 'pay back' the energy used to manufacture it?
The comparison of energy used in manufacture with the energy produced by a power station is known as the 'energy balance'. It can be expressed in terms of energy 'pay back' - the time needed to generate the equivalent amount of energy used in manufacturing the wind turbine or power station.
The average wind farm in the UK will pay back the energy used in its manufacture within six to eight months. This compares favourably with coal or nuclear power stations, which take about six months.
How much space do wind turbines require?
A typical wind farm of 20 turbines might extend over an area of one 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.
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.
How much does it cost to make electricity from the wind?
Wind energy is one of the cheapest of the renewable energy technologies. It is competitive with new clean coal fired power stations and cheaper than new nuclear power. The cost of wind energy varies according to many factors. An average for a new onshore wind farm in a good location is 3-4 pence per unit, competitive with new coal (2.5-4.5p) and cheaper than new nuclear (4-7p). Electricity from smaller wind farms can be more expensive.