Pioneering carbon-cost optimisation in offshore wind foundations

Offshore wind allows the UK to harness its naturally strong winds. The ScotWind leasing process enabled developers to apply for seabed rights to plan and then build wind farms in Scottish waters. As much as 27.6GW of new generating capacity will be built over the next decade as a result, and 65% (18GW) of that is earmarked to be floating wind. With turbine ratings expected between 15-20MW, Scottish waters could see over 1,400 new turbine foundations from this lease alone.

Early decision-making for offshore wind is driven by multiple objectives, such as the levelised cost of electricity. Given the scale of buildout and considering the UK Government’s Net Zero Strategy, optimising for the embodied carbon different fabrication and transportation scenarios may support scenarios with a higher level of local content.

Kent has worked in partnership with the Institute for Energy Systems at The University of Edinburgh, and our former summer internship student, Clementine Thompson, through a master’s thesis on multi-objective optimisation for carbon emissions and the cost of offshore wind foundations.

The cost and embodied carbon from over 90 offshore wind foundation design scenarios were analysed in order to determine optimal design choices for future ScotWind sites. Support Vector Regression and nonlinear relationships were used to determine the mass of steel and grout required for jackets in water depths between 40-80m with ratings 12-20MW and for steel semi-submersibles from 10-20MW. The embodied carbon from the materials was calculated using data from ecoinvent, the Inventory of Carbon and Energy (ICE) and worldwide steel fabricators, and the costs were calculated using steel production costs from World Steel, labour costs and industry rates.

The shipping of the foundations from China, Dubai, Spain and the North of England to Scotland’s Port of Cromarty was also accounted for, using case studies such as the Seagreen and Kincardine wind foundations to determine the types of ship, the number of foundations onboard and the subsequent costs and carbon from the shipping. A theoretical scenario of local manufacture using green steel in Scotland was also considered, using projected costs and embodied carbon.

This enabled embodied carbon (gCO2eq/kWh) to be plotted against its relative cost (£2022/kW) for each scenario to assess the relative carbon-cost optimisation challenge.

Interested to learn more about this research project? Drop by our stand G40 at Renewable UK's Global Offshore Wind 2023 to connect with our Floating Offshore Wind Lead, Ed Unwin.

Discover how we implement multi-objective as Edward Unwin and Robin O’Connell discuss the process for Floating Substation Design: https://bit.ly/42l69Kt