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Barriers to gravity based solutions

Published:  06 April, 2016

Focus and investment into fabrication infrastructure is needed to unlock the potential of gravity base structures for the offshore wind sector reveals a new study. ODEE reports.

The barriers that exist to large-scale commercialisation and adoption of gravity based structures (GBS) as Wind Turbine Generator (WTG) foundations for deeper water sites in the offshore wind sector, have been highlighted by the Carbon Trust in a new study, supported by the Scottish Government.

GBSs have been successfully demonstrated and deployed in shallow water wind farm projects. However, as wind farm developers have ventured further offshore into deeper waters, the industry has failed to adopt GSBs as a potential solution for large-scale commercial projects.

The Carbon Trust study states that this inertia in the industry has been caused by lack of confidence in the fabrication and installation of GBSs for commercial projects. This is in part, due to insufficient levels of investment in the right fabrication infrastructure to make large-scale roll out viable, and a lack of coordinated and targeted activities to address and overcome major challenges.

Unlike steel based foundations, which uses an existing supply chain, GBSs require specialised concrete fabrication sites, ideally located close to deployment sites. The Carbon Trust highlights that there has been a lack of will from the supply chain to invest in large scale production sites as, to-date, the market signals have been insufficient.

Marc Costa-Ros, Senior manager of Offshore Wind, at the Carbon Trust commented: “Gravity base structures offer the offshore wind sector a cost effective foundation solution of offshore wind farms in deeper waters. They also have the potential to be less affected by external load forces due to the more rigid nature of concrete over steel. To encourage development at the scale required to meet the level of industry demand, new specialised fabrication sites must be built. We have now reached a ‘chicken and egg’ situation and open dialogue and collaboration between designers, developers and other industry stakeholders will be critical to realising the full potential that GSBs offer to the sector.”

Alan Bromage, chairman, The Concrete Centre Interest Group for Offshore Wind added: “The Carbon Trust study accurately captures the benefits provided by concrete gravity bases, and reports some of the perceptions that are current barriers to the increased usage of this cost-effective solution. This report has the potential to be a catalyst for further collaboration, which is welcomed by the UK supply chain and solution providers represented by The Concrete Centre interest group.”

The study highlights that the slow uptake of GBS for deeper water offshore wind farms will continue unless industry confidence can be increased, and investment into building suitable fabrication infrastructure can be minimised. Furthermore, more work needs to be undertaken to demonstrate the feasibility of GBS for deep water sites, with large turbines. Proving that serial fabrication and installation can be a reality, will also increase industry confidence that GBSs can be produced at a commercial scale.

The study concludes with specific recommendations for designers, developers and governments on how to increase market share for GBS. This will deliver a cost-effective option for WTG foundations in areas such as the North Sea where the cost competitiveness of monopiles and jacket foundations are being pushed to their limits.

To read the study in full please visit: www.carbontrust.com/gravitybasefoundationstudy

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