One of the most interesting discussion points in OWJ’s walk-to-work webinar was whether industry limits on operating conditions can be bettered by using data
In Riviera Maritime Media’s ‘Walk-To-Work: rising to the challenge,’ webinar, panellists were uniform in their views about a number of subjects, but one thing stood out: that data can drive the development of more efficient, safer access to and from offshore wind turbines.
The webinar was the first in Riviera Maritime Media’s Offshore Wind Webinar Week, part of an ongoing series of webinars.
Bibby Marine Services chief executive Stephen Bolton, Ampelmann business development manager Caspar Blum and Safeway BV chief executive Wijnand van Aalst agreed that, as the walk-to-work market for offshore wind grows and goes global, the more the industry collects and uses data, the more efficient it will become and the safer connections will be.
Data will help the walk-to-work market become more efficient and cost-effective, drive down costs and enhance windfarm operations and maintenance. In turn, that will help to further reduce the levelised cost of energy of offshore wind.
Mr Bolton highlighted Bibby Marine Services’ use of a digital twin of its vessels that enables the company to predict access on specific projects in specific conditions. He explained this allows the company to have a conversation with clients about the percentage of operating time a vessel – and an access system – will be able to provide access to a turbine.
Mr Bolton said collecting data on a regular basis, analysing it and providing feedback enables key personnel such as a vessel’s master and dynamic positioning officer to further enhance their skills.
In the longer term, said Mr Bolton, data could help the industry enhance operating practices and enable technicians to be safely be transferred to turbines in higher sea states than current practice allows.
As highlighted previously by OWJ, contracts for walk-to-work vessels in the offshore wind industry are usually defined in terms of access at a significant wave height (Hs), within which transfers must be capable of being undertaken. But Mr Bolton believes focusing purely on Hs could place unnecessary limits on the ability of a vessel to undertake transfers and that well-designed ships with suitable access systems can do better than industry norms suggest.
In his presentation, Mr Bolton described the company’s use of data in more detail. A digital twin could be used as a simulator to assess the probability that a gangway can connect in site specific conditions, he explained. “If that probability is above a certain threshold, it is possible to conclude that a transfer can be made,” he said, allowing a shift from Hs limits on transfers to ‘percentage access.’
The company also uses data from operations to support design data, including a data set of more than 2,000 transfers from one location in the central North Sea. This data was plotted to show a linear correlation between gangway stroke capacity and Hs achieved. “Extrapolation supports our assertion that transfers in greater than 3 m Hs are achievable,” Mr Bolton said.
“However,” he said, “as also seen from the data, we are often restricted to 2.5 m Hs. The industry needs to ask itself, what is the value to the market of connecting above 2.5 m Hs? If transfers could be conducted when the significant wave heights exceed Hs 2.5, this would surely be of value to the industry,” he said.
If transfers can be undertaken safely about 2.5 m Hs, it could shorten project construction time, resulting in increased generation and could help to reduce the levelised cost of electricity from offshore wind. “Yet we have the restriction and worse in tenders, and no value is placed on this potential additional capability,” said Mr Bolton.
But, he said, there is also an operator challenge to be borne in mind because analysis and access prediction in high sea states does not consider the human factor. An Hs of 3 m can mean waves of 5 m plus: might this lead to the crew not wishing to connect, he asked. And if that is the case, how do we measure this effect?
As Mr Bolton previously indicated, in addition to demonstrating safe transfers are possible in higher sea states than the 2.5 m Hs usually specified by the industry, Bibby Marine Services’ analysis suggested there may also be times when Hs is lower than 2.5 m when the crew of the vessel might still be over-cautious about connecting, or when the vessel is not set as efficiently as it might be.
Sub-optimal practice, including using sub-optimal headings for the vessel, could have an impact on fuel consumption and emissions, Mr Bolton said.
Effective walk-to-work operations is not just about maximum wave height, he explained. “We need to make sure the vessel is optimally set up when transfers are easy, not just when it is challenging.” Equally, there might be times, he said, when Hs was higher when connections could have been made but were not attempted.
The company used technology from BMO Offshore and Next Ocean to track gangway use, DP performance and weather conditions, including sea state and wind and found that information about wave period, not just wave height, was crucial to decisions about how to set up a vessel to undertake a transfer.
Sometimes, said Mr Bolton, energy associated with longer wave periods was not identified visually by the crew or conventional wave measuring devices. “Better information about wave period has changed the way decisions are taken on the bridge,” Mr Bolton explained.
“Predicting access using a digital twin has been validated and can be relied upon, but the human factor should not be overlooked,” Mr Bolton concluded. “Also, what we see with our eyes and even what we measure may not be the full picture. The industry still has a lot to learn about walk-to-work and about the way conditions affect operations.”
Mr Blum told delegates Ampelmann sees three key changes taking place in the offshore wind walk-to-work market. The first is the ever-growing size of turbines to which walk-to-work systems must provide access; the second is the need to make access systems ‘greener,’ with reduced power demand and the introduction of electrically powered systems. The third, he said, is the need to enhance efficiency by using purpose-built vessels, integrated walk-to-work systems and ‘data-driven operations.’
Mr van Aalst told delegates Safeway also sees data analytics as an important tool for cost reduction, both prior to a job and ‘on the job’. The company uses hardware in the loop and wave simulation techniques during production; while on the job, it uses remote access, a daily ‘digital handshake,’ KPIs and artificial intelligence to enhance operations and plan maintenance work.
How is the market evolving?
In addition to providing insights into Ampelmann’s use of data, Mr Blum also provided insights into opportunities and challenges for the walk-to-work sector.
Asked where geographically he expects demand for walk-to-work systems for offshore wind to be greatest, Mr Blum said that, in the next 2-3 years, Ampelmann expects demand to be greatest in Europe, where the largest number of offshore windfarms have been built and are under construction, but he expects demand to grow steadily in other countries where large-scale offshore wind projects are already underway – such as in Taiwan – or are about to get underway, such as in the US.
The walk-to-work market is evolving rapidly and demands customers place on offshore access gangways are changing. The first generation of offshore access systems were designed to transfer windfarm technicians and equipment they could carry, but a new generation of more capable access systems has emerged in the last couple of years, that can also be used to enable windfarm technicians to push trolleys of equipment across from a vessel to the landing platform on a transition piece.
Increasingly, offshore access systems are also being used as cranes, lifting items onto a landing platform. Mr Blum expects demand for this kind of capability to grow, and that next-generation access systems will need to be able to lift heavier loads and do so to a greater height.
“We also expect the growth in size of offshore wind turbines will see growth in the need to be able to transfer spare parts and installation tools,” he said. He said offshore access systems with enhanced capabilities may play a growing role in the inter-array cabling segment, as their lifting capability grows.
“During inter-array projects, a cable pull-in spread needs to be lifted from the vessel to the transition piece,” he explained. “The spread is often heavier than the lifting capacity of many motion-compensated gangways and lifting has to be broken down into a series of smaller lifts.
“Hence a gangway that can lift the whole spread in one lift can could save a lot of time. Most importantly, it would reduce the number of lifts required overall, which reduces risk as each lift is a potential hazard.”
Asked about power technology for the walk-to-work systems of the future, and the advantages of all-electric systems, Mr Blum said he expected the market will see greater use of electric or electro-hydraulic systems which can be powered by generators on a vessel, thus saving deck space. Electric power would also reduce fuel consumption and emissions, he noted.
Asked how the design of a walk-to-work system is challenged by the ever-growing size of offshore wind turbines – with a 14/15-MW offshore wind turbine launched recently by Siemens Gamesa and a 12-MW unit from GE Renewable Energy being tested – Mr Blum said larger turbines would require the development of gangways with a greater stroke. “Longer gangways will be needed,” he explained. “This can mean a trade-off with less lifting capability, to reduce gangway weight and cost.”
Asked whether power consumption is an important issue for vessel owners and how can it be reduced, Mr Blum said, “Most vessels can power our electric systems and, if not, we supply diesel hydraulic power units. If they do not have sufficient power, the power requirements of the gangway are known from the outset and a vessel can be equipped with generators.”