Building an offshore wind farm

Offshore wind farm

3 May 2018 by Dr Carol Cotterill

As a geologist, you never know what nature is going to throw at you.

At the moment I am involved in ongoing work to help find the best site for offshore wind energy developments. We're mapping the seabed and beneath off the northeast coast of the UK.

The UK has an enormous capacity for renewable energy and the planned wind farm at Dogger Bank will be the biggest in the UK so far, generating cleaner power for up to four million homes.

The seabed is still a bit of a mystery though, which is why it's so important to find out as much as possible about what it looks like and what it's made of. The best weather for our data gathering trips out to the North Sea usually comes between April and September. But, even then, we still have "interesting" days when it's too rough to think much beyond staying in your bunk and not falling out.

The renewable developers are looking for dense marine sand, which is ideal for foundations for turbines and for burying cables, and that's what they thought they had at Dogger Bank. But our research has shown that that's not what's there. I had to break the news that the ground beneath the seabed there looks like someone has rucked it all up much like a rumpled bedsheet!

The old geological maps suggested that Dogger Bank was clay. I think many scientists had thought it was like a layer cake, with marine sands and then glacial sediment from the Ice Age, followed by more marine sands after the ground was flooded again. That is all there, but it's more complicated than that. As we analysed the new data, we looked for features in the buried landscapes that could be causing this complexity. We wanted to know why we weren't finding that neat layer cake we'd expected.

What is there is a buried glacial landscape and there are huge, long, curved ridges up to 50 metres high in big arcs spanning up to 200km. They were formed when the area was above sea level and covered with ice in the last Ice Age. Back then, Dogger Bank was part of a large land mass connecting what's now mainland Europe to Britain. We know that Dogger Bank was once above water because some of the core samples we collected there contained evidence of various flowers and pollens.

It's made of similar clays which have all been mashed together by ice sheets, creating a deformed landscape that looks as though it's been bulldozed. And all of them behaved differently when we tested them. You don't see features like this on such a big scale anywhere else around the UK. In other places, these glacial landscapes have been eroded by the sea when it came back and flooded the land. In some places it's been disturbed by buildings and roads.

For offshore wind farm developers, we've provided vital information because they can engineer "for anything" once they know what's down there. We will continue advising them on proposed sites for every turbine, modifying the geological model as we get more information.

For scientists, it's a fascinating insight into the past Ice Age and how it has affected the geology of the seabed today.

NERC science enables growth of UK renewables

  • NERC data and expertise are used by regulators, energy companies and investors to reduce the risks and costs of renewable energy developments.
  • Our science has been key to assessing the safety of wave energy turbines to seals and other marine mammals, the effects of wind turbine installations on coastal erosion and the feasibility of tidal barrages.
  • Since 2010, NERC's British Geological Survey and National Oceanography Centre have co-led high-quality mapping of the UK seafloor for use by industry, marine planners and conservation groups.
  • By combining information collected by a large number of organisations undertaking marine surveys, the Marine Envionmental Mapping Programme (MAREMAP) provides detailed and up-to-date maps that are available for all users of marine geoscience information.
  • The partnership informs responsible decision making about marine activities and delivers better value for money to support UK industries and help government to meet its environmental and development objectives. If organisations were to do this themselves, it would cost £700,000 per 1,000km2.