Government Energy Policy

National Policy Statements

On 18th July 2011 the House of Commons debated and approved the six National Policy Statements for Energy (NPS), as reported on the DECC (Department for Energy and Climate Change) website, National Policy Statements for energy infrastructure. The third statement covers renewable energy infrastructure [EN-3], and here we look at extracts of this statements that relate to onshore wind.

This National Policy Statement (NPS) for Renewable Energy Infrastructure is used for decision-making by the "Infrastructure Planning Commission" (IPS). In the statement, section 2.7 covers onshore wind. By way of introduction:

Onshore wind farms are the most established large-scale source of renewable energy in the UK. Onshore wind farms will continue to play an important role in meeting renewable energy targets.

Onshore wind farm proposals are currently likely to involve turbines from between two megawatts (MW) of generating capacity and up to three and a half MW individually, but as technology develops, this could increase. The total number of turbines comprising a wind farm of 50 MW capacity or greater covered by this NPS is therefore likely to be fourteen or more. This scale of development will inevitably have some visual and/or noise impacts, particularly if sited in rural areas.

The statement considers these areas for onshore wind production:

  • Site selection factors
  • Technical considerations for the IPC
  • IPC Impact Assessment
  • Impacts: Biodiversity and geological conservation
  • Impacts: Historic environment
  • Impacts: Landscape and visual
  • Impacts: Noise and vibration
  • Impacts: Shadow flicker
  • Impacts: Traffic and transport

Site Selection

These are Predicted wind speed, Proximity of site to dwellings, Capacity of a site, Electricity grid connection, and Access.

Wind speed increases with height above ground level and the amount of electricity generated increases disproportionately with increases in the wind speed. This in turn affects the carbon emission savings and the commercial viability of the site.

Applicants will often have installed temporary anemometry masts or similar on the site for 12 months or more to ascertain precise onsite wind speeds prior to submitting the wind farm application.

Appropriate distances should be maintained between wind turbines and sensitive receptors to protect amenity. The two main impact issues that determine the acceptable separation distances are visual amenity and noise.

The turbines must be placed at a sufficient distance from one another within the site. A spacing of six rotor diameters is normally required in the direction of the prevailing wind direction.

The connection of the proposed onshore wind farm into the relevant electricity network will be an important consideration for applicants of onshore wind farms. The connection voltage and the distance from the wind farm to the existing network can have a significant effect on the commercial feasibility of a development proposal.

Given that potential onshore wind farm sites are largely in rural areas, access for the delivery of turbine components during construction can be a significant consideration for wind farm siting.

Technical Considerations

These are access tracks, project lifetimes, project flexibility, micrositing, and repowering.

Applications should include the full extent of the access tracks necessary and an assessment of their effects.

Onshore wind turbines typically have a design life of 25 years, although this can vary, and can be decommissioned relatively easily and cheaply.

Many different makes and models of onshore wind turbines are available. Each of these will have differing hub heights, tip heights, design and generating capacity. Wind farm operators may not know precisely which turbine will be procured for the site until some time after any consent has been granted

Applicants are likely to need flexibility in a project consent to allow for any necessary micrositing of elements of the proposed wind farm after its consent and during its construction. A tolerance of between 30m and 50m of elements of the required infrastructure is typical.

The owner of the wind farm may seek to “repower” the site with new turbines. Given the likely change in technology over the intervening time period, any repowering of sites may involve a different number of wind turbines (usually fewer) of a different scale and nature (usually larger).

Impacts – Biodiversity and geological conservation

It may be appropriate for the assessment to include collision risk modelling for certain species of birds or to estimate the mortality rate for certain species of bat.

The assessment should include any effects on biodiversity resulting from the disturbance of important habitats such as peat.

Impacts – Historic environment

Visualisations may be required to demonstrate the effects of a proposed onshore wind farm on the setting of heritage assets.

Impacts – Landscape and visual

The arrangement of wind turbines should be carefully designed within a site to minimise effects on the landscape and visual amenity.

It is unlikely that either the number or scale of wind turbines can be changed without significantly affecting the electricity generating output of the wind farm.

Impacts – Noise and vibration

Operational wind turbines will generate increases in noise levels (whether from machinery, for example aerodynamic noise from turbines, or from associated sources, such as traffic) although the relative noise impact diminishes with distance.

The method of assessing the impact of noise from a wind farm on nearby residents is described in the report, ‘The Assessment and Rating of Noise from Wind Farms’ (ETSU-R-97). The report recommends noise limits that seek to protect the amenity of wind farm neighbours.

There is no evidence that ground transmitted low frequency noise from wind turbines occurs at a sufficient level to be harmful to human health.

Impacts – Shadow flicker

Shadow flicker is the effect caused when an operating turbine is located between the sun and a receptor, such as a dwelling or place of work.

Research and computer modelling on flicker effects has demonstrated that there is unlikely to be a significant impact at distances greater than ten rotor diameters from a turbine.

Where wind turbines have been proposed within 10 rotor diameters of an existing occupied building, a shadow flicker assessment should be carried out by the applicant. The maximum potential number of hours that shadow flicker could occur at each affected occupied building should be calculated, using industry good practice.

Modern wind turbines can be controlled such that the operation of individual wind turbines at the periods when shadow flicker has the potential to occur at a specific property or group of properties can be inhibited.

As far as technologically possible, rotating blades should not be reflective (other than in terms of countering effects on radar).

Impacts – Traffic and transport

Many onshore wind farms will be sited in areas served by a minor road network. Modern wind turbines are large structures and some components, notably the rotor blades, can currently only be transported to sites as complete structures. The construction of a wind farm will therefore require sufficient access for long and wide load items.

The applicant should have assessed the various potential routes to the site for delivery of materials and components.

The applicant should assess whether the access roads are suitable for the transportation of components which will include whether they are sufficiently wide for the rotor blades, or bridges sufficiently strong for the heavier components to be transported to the site.

Once wind farms are in operation, traffic movements to and from the site are generally very light. The need to replace machine components will generate heavier commercial vehicle movements, but these are likely to be infrequent.

Consents for Onshore Wind Farms

A Commons Library briefing paper published on 24 August 2011 explores the situation (past and present) of wind turbine planning consent. It is SN04370, labelled as a Planning and Renewable energy, authored by Christopher Barclay, and can be found at the Parliament.uk website: Consents for Wind Farms - Onshore - Commons Library Standard Note . The full PDF version is at www.parliament.uk/briefing-papers/SN04370.pdf.

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