Wind Farm Constraints and Site Suitability

Sites suitable for commercial scale wind energy development are increasingly difficult to come by. Technical constraints and the assumed criteria demanded by the local planning authority to permit a wind farm development serve to constrain areas. When assessing a land holding there are a number of key issues to consider.

1    Wind Speed

A site with wind speeds in excess of 6.1 m/s at 45m above ground level is generally seen as worth investigating in further detail in light of the financial returns possible from modern wind turbines.

2    Noise Impact and Shadow Flicker

Typically unacceptable noise and shadow impacts from a wind turbine will travel around 500m. As a result the majority of sites which are proposed as ‘developable’ will exhibit a large enough area for large scale turbines after taking into account a 650m-750m separation distance from dwellings.

3    Ecological Issues

Ecological studies are required to support a planning application in order to ascertain whether a development will impact upon any protected species. If protected species are in close proximity to a site they can present significant issues.

4    Statutory Designations

Statutory designations generally denote an area of environmental or historic importance. Those which can impact upon a wind farm development at the planning stage include Sites of Special Scientific Interest (SSSI’s), Natura 2000 sites, Scheduled National Monuments and designated Ancient Woodland.

5    Aviation Issues

Aviation constraints in relation to wind farm developments are linked to the impact of tall moving structures on both radar and established low level flight paths. They can present a navigation hazard, as well as showing up as interference on radar screens due to the turning blades reflecting radar energy.

6    Access

The most notable issue is the necessity to transport turbine rotor blades to the site as they cannot be delivered in sections. This leads to a requirement for loads of approximately 45m long and 7m wide to access any given site.

7    Telecommunications
       
Microwave links from mobile telephone masts can reflect off turbine blades causing interference. These links exist between masts across the national telecommunications network and as a result OFCOM need to be consulted in relation to all proposed wind farm developments to confirm what impacts there may be. These links have the ability to sterilise areas of a site, potentially rendering it undevelopable.

8    Public Rights of Way

Public rights of way can again act to limit the developable area available at a site as it is planning convention to site turbines at least ‘fall distance’ away. For commercial scale wind turbines this is ordinarily between 100m-140m depending on the size of the machines proposed.

9    Landscape

Wind turbines often have a significant impact upon the landscape as a result of their height. This impact can be mitigated by adjusting the height of the turbine towers and strategically locating the machines.

10    Grid Connection
       
The two key issues are proximity to transmission infrastructure, being an electricity substation within a realisable distance of the project, and local grid capacity. Capacity relates to the amount of additional electricity the local infrastructure is able to accommodate. Should the local wires and supporting infrastructure be close to capacity, cable and substation upgrades may be required to accommodate the additional electricity from the wind farm. This can result in significant additional costs and affect project viability.

11    Net Developable Area

In order to accommodate large scale wind turbines, a site must be suitably large so as to allow adequate spacing and prevent turbulence and wind shear between the machines. This distance is a factor of the rotor diameter of the specific turbines used.

Carter Jonas are adept at assessing sites for wind energy developments using the latest GIS tools. If you think your holding may be suitable and would like it assessed please contact a member of the Energy Team.

Nick Barber

Associate

Nick is an Energy Specialist based in the east of the country. He provides advice on renewable energy developments, with a particular emphasis on wind energy and solar schemes. His work includes c...

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Nick is an Energy Specialist based in the east of the country. He provides advice on renewable energy developments, with a particular emphasis on wind energy and solar schemes. His work includes conducting feasibility studies, undertaking site acquisitions, negotiating option and lease arrangements as well as undertaking financial analyses and valuations, acting for private, institutional and commercial clients within the energy sector. He also takes an active role in conducting CJ research projects, co-authoring the firms Energy Index. Away from work Nick is a keen skier and rugby player.

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