Carbon Trust bird study should make developers’ lives easier

Seabirds change their flight path to avoid collisions with offshore wind turbines. That sounds like good sense from our feathered friends but, for the developers of these projects, it is a big deal.

This month, the Offshore Renewables Joint Industry Programme published its 248-page Bird Collision Avoidance Study, which analyses seabird behaviour and collision risk at offshore wind farms. The study was commissioned by 11 offshore wind farm developers including Swedish utility Vattenfall; managed by UK organisation Carbon Trust; and backed by the UK government.

The study analysed seabird activity for two years at Vattenfall’s 300MW Thanet wind farm in UK waters. Its analysis was carried out by human observers and a system that automatically records seabirds’ movements. This resulted in a massive data collection, including over 600,000 videos.

Of these, around 12,000 videos contained evidence of bird activity – but only six collisions with turbines were observed. This is less than half of what the researchers expected and is the result of seabirds change their flight path to avoid being hit.

Talking to A Word About Wind, Carbon Trust director Jan Matthiesen said that this is relevant for investors because it shows, for the first time, evidence of the behaviour of birds approaching offshore wind farms: “We have actually seen that seabirds are consciously avoiding the turbines, as they now have a much better understanding of the movements of the turbines. This has never been seen in this way before.”

The study shows that seabirds have adapted to the presence of wind turbines in the sea. He said: “When you cross the road, you know that you have to avoid the cars, because you have learned as a child that they represent a danger. Birds have been learning in the same way how to behave in presence of turbine blades.”

The study’s findings are particularly relevant for offshore wind developers, as the risk to seabirds has heavily affected the progress of schemes. The most famous example is the four-year legal battle led by wildlife charity RSPB against four offshore wind projects totalling 2.3GW in Scottish waters. Its case, that Scottish ministers had not properly considered the impact of this quartet on seabirds, was dismissed by the Supreme Court last November.

Matthiesen says the study would help developers in two ways.

First, he said evidence of seabirds’ avoidance behaviour would reduce consenting risk. The consenting process of offshore wind farms requires identification, prediction and evaluation of the environmental effects of the proposed projects; and the risk of birds colliding with blades is one of the most significant environmental impacts. This evidence of the birds’ behaviour could speed up the permitting process, providing a more realistic and reliable evaluation of birds’ collision risk.

Second, Matthiesen argued that the extensive dataset of observations of seabird behaviour collected by the study would enable developers to update their collision risk models.

Collision risk models currently used by offshore wind developers are often based on data from onshore wind farms, for example. This is not ideal because it is based on different turbine designs in a different landscape where birds may behave differently.

They also predict the number of collisions based on linear flight patterns, assuming that birds take no avoiding action. The data collected by the study can now be used to update these models, to show a more accurate collision risk. This is crucial at a time when the next generation of wind turbines are developed.

However, the study has some limitations: it currently relies on data collected at one site only, largely during daylight and good weather conditions, so may not capture all the variability in relation to weather, visibility and regional differences. Matthiesen said there is scope to extend the research and make it more comprehensive.

Even so, studies like this make a valuable contribution to growth of the offshore wind sector, as they help developers and investors to ease fears that wind turbines harm wildlife. And that’s a goal that most in the sector and those outside it can agree on.