United Kingdom

United Kingdom

On Reflection: Designing within the environmental envelope

UNITED KINGDOM: The viability of the offshore wind sector and the meeting of 2020 renewables targets both depend on having a healthy pool of consented projects. But a poor understanding of the impact of offshore turbine design on wildlife makes consent a complex issue.

(pic: the Natural History Museum/Alamy)
(pic: the Natural History Museum/Alamy)

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A healthy pool of consented offshore wind projects is vital to give confidence to the sector, but as the UK prepares for a rise in consenting applications, a report from industry body RenewableUK warns that the UK government's austerity measures may be too steep for consenting bodies to overcome.

There is good reason for concern. The Climate Change Committee has warned ministers that failure to deploy large-scale offshore wind projects over the medium term will not only hamper the sector's cost-reduction aspirations, but also compromise government pledges on energy security and EU renewables targets.

One of the key barriers to consent — bird mortality from turbine collision — is growing in significance as project applications increase in size. Birds like gannets and kittiwakes are EU-protected species with complex population dynamics. Uncertainty in the understanding of the implications of wind-turbine arrays for these species, for example, demands a cautious approach — but this threatens to undermine the progress of projects.

A recent example was the Docking Shoal project, where theoretical thresholds for Sandwich Tern harvest rates compromised the "maximum planned capacity" for the Greater Wash strategic area. Consent was refused even though the collision risk model was overly cautious and evaluated against further precautions, with a wide Rochdale Envelope submitted to allow for larger turbines.

The Rochdale Envelope is a UK-specific 'worst-case scenario' approach to the environmental impact of a project. Because an offshore wind farm design is complex and lengthy, the Rochdale Envelope allows a broad definition of the project, within a number of agreed parameters, to be used in a consent application. The assessment is made on the greatest potential environmental impact, with more detail on impacts provided as the specifics of the project design and equipment becomes available.

In France, offshore schemes are more precisely defined and contractors agreed before construction permits awarded. The advantage of the UK Rochdale Envelope is that it offers flexibility for future-proofing projects — say, if the turbine size increases — and helps promote supply chain competition

Rochdale problems

The disadvantage of the Rochdale Envelope approach, however, is that a viable project can stall or losing consent based on the precautionary thresholds alone. Unless developers can find a way to clarify the impact on the environment, regulators have little choice but to default to precautionary principles.

Before entering planning, developers should continue design evolution,mitigating environmental impacts, while keeping their Rochdale Envelopes as realistic as possible. Options to de-risk consent at an early stage could include modifying foundation concepts and hub heights to design out bird-collision risks. This requires a multidisciplinary approach that may provide a win-win scenario, with modifications reducing impacts on EU-protected species, while improving energy yield to ensure such changes keep projects commercially viable.

By considering the environmental impact before planning the project design, developers can reduce the complexity of their Rochdale Envelope, cut engineering design costs by narrowing foundation options, improve order book certainty for contractors, and assure regulators that decisions on potentially cumulative impacts on EU protected species will be manageable.

Ultimately, without approval, there is no project, no profit and no sustainable future for offshore wind.

Dr Steve Freeman is director of environment at TÜV SÜD PMSS, with experience in environmental management, policy and planning in coastal and marine waters globally

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