‘Living designs’ essential for further cost reduction, inquiry told

Royal Academy of Engineering chair in emerging technologies in intelligent and resilient ocean engineering Professor Susan Gourvenec said the conventional practice of routine, scheduled inspections of offshore windfarms “is impractical for the scale of offshore wind developments of the present and certainly for the future.” She also questioned whether the huge size of future windfarm developments makes continued use of conventional survey vessels and survey technology economic.

Professor Gourvenec specialises in geotechnical engineering and is convenor of the ISO working group responsible for international standards for offshore site Investigation, offshore foundations and geotechnical design considerations.

In a submission to a UK environmental audit committee inquiry into offshore wind technology, Professor Gourvenec said, “Living design, requiring innovation in sensing and modelling technologies, has an invaluable role to play in monitoring and maintenance, late-life management, informing on asset health for decommissioning, or post-decommissioning stability if left in situ.

“Offshore structures are currently monitored for a range of conditions to inform on operational performance, intervention, maintenance or repair, life-extension and, more recently, on the state of a structure or system following decommissioning.

“Challenges exist regarding the extent to which this data can be synthesised to form a clear picture of a structure’s system health, to enable either a human or autonomous system to act on the information.”

Professor Gourvenec said opportunities for improved information over the lifecycle through technological advances could include machine learning and genetic algorithms to convert large volumes of data collected into knowledge, for example correlating whole-life monitoring data with the predicted response of an asset to better understand remaining useful life through digital twinning or living design approaches.

Other opportunities include ‘edge computing’ methods to overcome the challenges of transmitting large volumes of data from an offshore asset to a control or data centre, and minimum-data informed machine learning methods coupled with physics-based methods to inform on asset integrity at any location.

The professor said smart sensing systems which ‘self-certify’ system health could address the burden and risk of monitoring ocean structures and enable optimisation of lifecycle performance.

Professor Gourvenec also called for change in the way that windfarm sites are surveyed. She said new approaches were needed for seabed survey and assessments of sites for bottom-fixed foundations, or moorings and anchors for floating wind turbines.

Professor Gourvenec said a European Union Research Roadmap specifically highlights foundations and anchor/mooring systems as a priority for reducing the cost of offshore wind, particularly for floating arrays, but solutions of this type are ‘absent’ from the UK’s Offshore Wind Sector Deal.

“Deriving engineering parameters of the seabed for design calculations for offshore foundations, anchors and moorings requires geotechnical site investigation. Offshore geotechnical testing tools that can be deployed with reduced vessel support are critical to reduce the cost of offshore renewables developments,” she said.

Professor Gourvenec said an economic challenge is arising due to the much greater area required for surveys of offshore windfarms as they grow in size and scale and number.

“A specialist geotechnical vessel could cost in the region of £100,000 (US$122,000) per day and a renewables site investigation will require tens or hundreds of locations to be investigated,” she told the inquiry.

She said opportunities for cost reduction of site investigations could include intelligent geotechnical site characterisation tools for remote or autonomous deployment or operation, to upscale capability without upscaling cost; and machine learning techniques to correlate continuous geophysical data with discrete geotechnical data, to optimise development of an engineering ground model of a development area.

“Harnessing the intelligence of sensing, robotics and autonomy, next-generation resiliently engineered systems will enable cheaper, smarter site characterisation, station-keeping solutions, monitoring and late-life and end-of-engineered-life management of offshore wind, which will accelerate the economic competitiveness necessary to scale up the UK market,” she concluded.

Using technology to cut the cost of floaters

Professor Gourvenec also provided input to the inquiry on opportunities to make anchoring and mooring solutions for floating wind more effective and less expensive.

“Smart mooring and anchor solutions for efficient and stable platforms in increasingly harsh environments are necessary to reduce capex and opex for floating wind,” she said.

She highlighted that foundations currently contribute up to 25% of overall capex for an offshore wind turbine and this will increase as developments move further from shore, to deeper water, as more challenging seabed conditions are experienced and as more complex foundations are required – as will be the case for floating facilities.

She said opportunities for cost reduction of moorings and anchors for floating wind through technological advances could include ductile mooring systems that absorb peak loading to reduce the size of anchors required.

“Confidence in smaller, novel mooring systems can be achieved through minimum-data informed machine learning models coupled with physics-based methods to assess response of the system through life,” she explained.

Professor Gourvenec said alternative anchors could be deployed with smaller vessels and over longer weather windows than currently possible with technology that was developed for oil and gas.

“Dynamically penetrating anchors can be deployed from smaller vessels and remote tracking devices could provide confidence of location and capacity, overcoming a challenge which currently prevents widespread uptake,” she said.

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