RESEARCH & DEVELOPMENT
CONCRETE GRAVITY FOUNDATIONS
Round 3 wind farm developments are largely in deeper waters and further offshore, with a mixture of seabed types. The different environment will require the deployment of alternative foundation solutions to those that the UK market has predominantly used to date and alternative designs will need to be considered.
The Concrete Centre, on behalf of the Interest Group for Gravity Foundations – Offshore Wind, has commissioned research projects to support the proprietary research of the group’s solution providers.
CARBON STUDY
Commissioned by The Concrete Centre and carried out by Arup and Vinci Construction, the study estimated the carbon footprint of the raw materials and other resources to be used in the construction of a concrete gravity foundation to support a 5MW turbine in 42m deep water.
THE STUDY ALSO INCLUDED CONSIDERATION OF… • Transportation of materials to a manufacturing/construction facility
• Resources used in the construction of the manufacturing facility
• Resources used in the manufacture of any bespoke vessels used for installation
• Resources used during installation of the foundations
• Resources used during maintenance of the foundations
• Resources used during deconstruction of the foundations
STUDY FINDINGS
The study found that the average carbon footprint for six different concrete gravity foundation (CGF) solutions was estimated to be 1,190 tonnes CO2e per 5MW unit (with a range of 708-1,597 tonnes CO2e per 5MW unit). This compared with an estimated carbon footprint for a steel jacket solution of 2,770 tonnes of CO2e per 5MW unit.
The key driver for the difference in the carbon footprints was the quantum and type of steel within the different solutions. The concrete foundations incorporate significantly less steel than the steel jacket solution. Moreover, reinforcement steel is used in the concrete solutions, which
in Europe is produced almost entirely from recycled materials, whilst this study assumed that steel plate would be used for a steel jacket. Further details have been published in CONCRETE magazine, and a pdf of the article can be downloaded from the micro page using the link at the end of this article.
ENVIRONMENTAL IMPACT ASSESSMENT
Commissioned by The Concrete Centre and carried out by Marine Space, the study reviews the marine environmental considerations for concrete gravity foundations (CGF), including comparison to foundation alternatives. The study explores the environmental effects and pathways associated with the various phases of the lifecycle of CGFs in the marine environment including…
• Ground preparation (if required)
• Emplacement on the seabed • Scour protection (if required) • Decommissioning
REVIEW FINDINGS
The review found that CGFs have an environmental footprint at the seabed similar to other deeper water foundation solutions. The advantage of CGFs over alternatives is the lack of significant noise emissions generated during their installation and emplacement. With increased requirements for consideration of noise in legislative controls, underwater noise will be a primary consideration for deepwater solutions for Round 3 developments.
CGFs solutions require no piling or hammering for installation, allowing mitigation of one of the major environmental impacts associated with offshore windfarm construction. This is both beneficial to the environment and mitigates a significant planning/programme risk.
The Concrete Centre
www.concretecentre.com/wind Click to view more info
www.windenergynetwork.co.uk
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