Digital twin will make vessel ops safer and more efficient

A leading vessel owner and a group of equipment manufacturers and technology providers are using a digital twin to reduce vessel downtime, enabling their clients to enhance productivity and reduce costs.

A contract for a ship such as a service operation vessel (SOV) usually specifies a level of performance in a specific sea state. For connections to offshore wind turbines, that is typically a significant wave height (Hs) of 3 m, but as MO4 founder Mark Paalvast explains, offshore operations are so complex and subject to so many variables, and vessels and equipment so diverse, that it may not always be possible for an owner to meet contractual requirements.

There are times he says, when although Hs 3 m is specified, it may not be possible to transfer technicians from a vessel to a turbine. Equally, at other times, it would be possible to safely undertake a transfer in Hs 3.4 m. The question is, how is the master of a vessel, the ship’s dynamic positioning (DP) operator and the gangway operator to know exactly what is and is not possible, however experienced they might be?

That is where a digital twin of a vessel developed by MO4, which specialises in ship motion forecasting, comes in. In an earlier phase of their work together, the partners in the Offshore Operational Advisory System (OOAS) project developed a digital twin that formed the basis of a decision support system based on predicted ship motions and workability derived from wave characteristics. The project was a success, but as Mr Paalvast explained, it demonstrated the need for more complex sea state characterisation and the inclusion of nonlinear responses of a vessel, such as those from its DP system, anti-roll tank and gangway.

In the next phase of the project, from Q4 2020 to 2022, in addition to MO4, the partners in OOAS, who include vessel owner Acta Marine; Maritime Research Institute Netherlands; Next Ocean, developer of an innovative wave prediction system; gangway manufacturer SMST; and Radac, which supplies wave and tide monitoring systems; plan to collect real-world data and use it to refine the digital twin, and significantly enhance its ability to support decision-making.

“A service operation vessel isn’t a straightforward ship to model,” says Mr Paalvast. “There are many different parameters to take into account and a lot of variables, but if sufficiently enhanced, a digital twin could help with operational planning, identifying weather windows and landing zones and determining optimal headings for vessels.

“The real-world data collected during the project will enable us to significantly enhance our algorithms. We will install a lot of sensors on Acta Marine’s SOV Acta Auriga and monitor waves, wind and currents, the ship’s propulsors and the operation of the gangway, and their effect on one another.”

The digital twin will take into account the hydrodynamic characteristics of the vessel and its anti-roll tank and will be coupled to a forecasting system from Next Ocean that uses wave measurements to predict operability 2-3 minutes ahead of actual operations.

The project partners believe the enhanced digital twin will make operations even safer and improve vessel uptime significantly. For a typical vessel, they say, it could result in 10 additional working days per year.

“The more refined the algorithm is, the higher the level of decision support capability it can provide,” Mr Paalvast concludes. “Studies indicate that a decision support system could reduce vessel downtime by 20-25%, depending on circumstances. That translates into greater yield from a windfarm, without the need to install any expensive hardware on the vessel.”