Avonmouth Wind Turbines Project

Current situation

Planning approval was granted in 2009 to build two wind turbines in Avonmouth. Permission has been gained for turbines with capacity of up to 3 MW each. A solution to mitigate any potential impacts of the turbines on the radar at Filton Airport was identified, prior to the announcement of the closure of the airport at the end of 2012. Tenders have now been sought for the supply, installation, operation and maintenance of the two wind turbines on behalf of Bristol City Council.

Overview

This proposal is about producing green electricity and reducing the city's carbon footprint. Green electricity is produced from renewable, non-polluting sources of energy, like wind, wave and solar power. This achieves a reduction in greenhouse gas emissions, the main gas being carbon dioxide (CO2).

Why wind?

Large wind turbines achieve the best possible CO2 savings per pound spent. Of all the carbon reduction technologies, large-scale wind power is the most highly developed, sophisticated technology and is the most cost-effective.

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, (at present demand for renewable electricity far outstrips supply);
• 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 energy will they produce?

Considering turbines in the 2 - 3 MW range, Garrad Hassan estimates that the annual energy production of the scheme will be between 9.6 GW/annum and 12.6 GW/annum. This annual production equates to meeting the electricity needs of between 2,237 and 3,355 ‘average’ households. A typical turbine generates 5.3 million units of electricity each year, sufficient to meet the average annual electricity needs of 1,000 homes and prevent the emission of 2,000 tonnes of the greenhouse gas carbon dioxide - equivalent to taking 667 cars off the road, (Ref. Renewable UK).

Consultation

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 application.

The Local Government Improvement and Development site has a case study on our wind turbine project.  The LG Improvement and Development site supports improvement and innovation in local government, working to develop and share good practice.

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, up to 3MW capacity, 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.

Google interactive map - use zoom to explore

View Larger Map

Size and dimensions of turbines

The type and size of the two wind turbines will be chosen to fully harness the wind and consider their environmental impact. They will be of a similar size to the three turbines already in operation at the Bristol Port Company in Avonmouth Docks. These have a hub height of 78 metres and tip height of 120 metres.

Explanation of terms

The hub is the vertical support that holds the rotor blades. Planning permission was gained for a maximum tip height of 131 metres, (i.e. hub height plus height of one rotor).
The environmental assessment was based around the above maximum dimension. The actual turbines will be subject to the formal tender.

Ecotricity video showing the installation of the turbines at Avonmouth Docks

Ecotricity operate three turbines on Bristol Port Company land at Avonmouth Docks.

Environmental impact

Habitat designations

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 lies next to the Severn Estuary, which is an internationally important site for various species and habitats, and particularly for its bird interest. The estuary 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).

Environmental Impact Assessment (EIA)

Consultants undertook a comprehensive Environmental Impact Assessment (EIA) to assess 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 ecology and bird studies were also undertaken and the results of these informed the Environmental Statement (ES). 

Frequently asked questions

RenewableUK has a more comprehensive list of Frequently Asked Questions on wind energy.

Noise

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:

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.

Shadow Flicker

What is shadow flicker?

Under certain combinations of geographical position and time of day, the sun may pass behind the rotors of a wind turbine and cast a shadow over neighbouring properties. When the blades rotate, the shadow flicks on and off. It only occurs inside buildings where the flicker appears through a narrow window opening. A single window in a single building is likely to be affected for a few minutes at certain times of the day during short periods of the year.

What is the likelihood of this occurring?

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.

Shadow flicker in practice

• Time when turbines are not running = 20%
• Days when the sun is not shining brightly = 50%
• Days when the turbine disc is turned at right angles to a dwelling and thus does not cause shadow flicker = 25%
• Overall the likely incidence of shadow flicker is assumed to be about 30% of the maximum potential.

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' time, i.e. as 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 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.

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. For more information see the Renewable UK's factsheet on Wind Energy and the UK's 10% Target.

Just as there are frequently asked questions about wind turbine technology, there are some common misconceptions. Renewable UK have put together their top myths about wind power.