Out of sight, but definitely not out of mind: inspecting the underwater parts of offshore wind farms

Published September 2017

Illustration: Persephone Coelho

Offshore wind turbines are beautiful things – glistening, pieces of superb industrial design, awesome in their scale and productivity, but, dip beneath the surface of the water and you find a mass of hardworking, mundane but essential infrastructure – foundations, piles, J-tubes, cables, and the seabed they interact with – struggling to survive in a harsh environment.

Foundation structures, for example, are subject to intense dynamic loading, surrounded by what is essentially acidic, oxygenated, organic soup. Add in exposure to waves, currents and seabed scour, and poor subsea visibility, and the picture for O&M looks quite challenging. Trying to prevent corrosion is an ongoing struggle, and there is the added frisson of cracks potentially growing in primary non-redundant structures.

All this highlights the importance of being able to regularly inspect the subsea assets of an offshore wind farm reliably and cost-effectively. The UK has had a world-leading offshore Oil & Gas (O&G) industry for several decades, and has successfully designed, built and operated subsea structures in harsh environments. Sophisticated bespoke equipment including ROVs, saturated diving systems and a range of sensors has been developed for remote monitoring and maintenance, and it might appear therefore that there should be no need for new bespoke technology to service the offshore wind market – it should be a simple question of technology transfer.

In practice, however, the offshore wind industry grew out of shallow water, nearshore/coastal marine civil engineering practice, not the O&G industry, and the structural designs that emerged are somewhat different from O&G structures, have different technical drivers, and their maintenance has a very different cost base. This has led to some unique industry-specific challenges, for which new cost-effective bespoke techniques and equipment are needed.

Everoze’s Technology Team has recently been working with the Carbon Trust’s Offshore Wind Accelerator (OWA) programme to investigate the bottlenecks and challenges associated with subsea inspection. An extensive industry stakeholder consultation exercise identified the current state of the art of offshore wind subsea inspection technology and practice, and identified two main challenge areas: grout integrity inspection and weld flaw detection, for both monopile and jacket structures.

This work has led to a new global Subsea Inspection Competition issued by the OWA to identify and support innovative concepts which could be developed or adapted to address the most significant challenges for sub-sea inspection of offshore wind farms.  The competition closes on 13th October 2017 and is open to any global technology developers who can meet the challenges identified in the competition brief. For more information and terms and conditions please follow this link: https://www.carbontrust.com/about-us/tenders/offshore-wind-accelerator-competition-sub-sea-inspection-methods

The winning concepts will have access to mentoring support from nine leading offshore wind farm owners, the opportunity to demonstrate their technology at an operational offshore wind farm in Europe, and further publicity support.Everoze Partner Zoe Barnes