While vessels dominate maintenance operations in offshore wind, helicopters will become more attractive options as windfarms move further offshore, says a leading analyst
While helicopters are ubiquitous and essential in the offshore oil and gas sector, they have not yet made the same in-roads for crew transfer operations in the offshore wind sector. Crew transfer vessels (CTVs) and service operations vessels (SOVs) dominate personnel transfer and maintenance operations, but could that change as windfarms migrate further offshore?
An analysis by a leading offshore rotorcraft consultancy Air & Sea Analytics points to a strong business case for using offshore helicopters in the offshore wind sector.
Air & Sea Analytics managing director Steve Robertson says historically, the sector has favoured vessels for crew transfer because offshore windfarms were near shore, usually less than 10 km away, visible from land. He says, “Vessels were ideally suited and the obvious solution for getting to the turbines. Logistics hubs for servicing turbines naturally became located at or near ports. There are now nearly 500 vessels marketed for the servicing of offshore windfarms.”
But with windfarm projects moving further from shore in the years ahead, the proposition changes. He says by 2030, nearly half (48%) of the installed base of turbines will be more than 30 km offshore. “The available data on windfarm operations tell a clear story: the helicopter is faster, safer for the passengers and less harmful to the environment than a crew transfer vessel while being less susceptible to interruption in service through bad weather,” says Mr Robertson.
While the difference in speed between rotorcraft and CTVs might be obvious, he says the safety and environmental concerns are less intuitive. He says based on industry data, “heli-hoists cause far fewer recordable injuries or lost-time incidents compared with crew transfer vessels.”
“As far as emissions are concerned, CTVs emit more CO2 per passenger mile than any comparable rotorcraft operation.”
He says, “Our analysis in the recent Offshore Wind Rotorcraft report shows that for both crew transfer operations (shore to helipad) and heli-hoisting (to the turbine nacelle) the helicopter had a clear advantage.”
While admitting the CTV sector has made strides in improving its carbon footprint with new designs and use of hybrid-battery and hydrogen-fuel technology, Mr Robertson says those “are few and far between.”
Air & Sea Analytics tracks 480 offshore wind service vessels via satellite AIS data, almost all of which are traditionally fuelled vessels. “Offshore wind rotorcraft are growing in number and at any one time as many as 30 are active in the market. We expect nearly 100 additional aircraft to be active in offshore wind by 2030,” says Mr Robertson.
Leading OEMs in the offshore wind rotorcraft market are Airbus and Leonardo, while leading lessors such as Milestone, Macquarie and LCI all either have active aircraft in the market or have had in the recent past.
He says, “Offshore windfarm operators have a choice to either embrace aircraft in offshore wind operations or to try and force change on the marine business to provide safer, cleaner operations.”
While larger SOVs and walk-to-work systems are key drivers in improving crew transfer safety, Mr Robertson notes CTVs are not able to operate beyond 1.5 m significant wave height. This is not the case for larger SOVs that provide both greater availability, typically remaining on station providing onboard accommodation and hotel facilities.
In the future, Mr Robertson sees the possibility of SOVs remaining offshore ‘on-station’ for extended periods of time through changeout of crew with rotorcraft via helipads. “This combination of vessels and rotorcraft may ultimately prove a popular solution for safe, reliable and easy transfer from airport to wind turbine,” says Mr Robertson.
Crew boat builders like CTVs
Meanwhile, traditional crew boat builders are filling their orderbooks with CTVs. Collaborating with ship designer BMT, Singapore-based Strategic Marine has developed the Strat Cat 27 (SC27) design, “combining form with function”, incorporating a reduced carbon footprint and hybrid drive options.
An evolution of the shipbuilder’s Strat Cat 26 design, the SC27 has an improved hull design that maximises the waterline length to improve operational efficiency across a large range of loading conditions, reducing emissions and fuel consumption. Flexibility is another key aspect of the vessel design, with owners able to choose from various engine makes, propulsion systems, deck cranes, active fender systems, and ride control systems.
The SC27 design is offered in two superstructure options to accommodate either 24 or 12 offshore technicians.
UK-based WEM Marine took delivery of a pair of StratCats in July from Strategic Marine and placed an order for two 26-m StratCats for delivery in April 2022.
Safety of personnel during transfer to the turbines is a primary concern. This is addressed in part by the CTVs’ AFS 2 active fendering systems that allow the vessels to ‘push up’ with greater confidence and with less risk of damage to the hull and offshore structures, while providing a stable and safe connection for the crew during varying sea conditions.
The variable distance centre section facilitates ‘safe climbing distance’ adjustment.
Strategic Marine business development manager for Europe Jim Fraser calls the fendering system “a game-changer” because it gives operators “a higher safety factor when pushing up on the turbines which translates into less time, cost and emissions per transfer and potentially a larger operating window.”
Singapore-based Penguin International sold its first two Windflex-27 CTVs, Valkyrie and Wotan, to Opus Marine for operation in the offshore wind market in Taiwan.
Designed by Incat Crowther, the CTVs are fitted with a resilient bow fendering system designed to maximise vessel wave-height transfer capability while minimising impact loads.
Each CTV is powered by four 662-kW Scania DI16 077M engines that drive Hamilton 521 waterjets, enabling speeds of up to 30 knots. Penguin is building similar CTVs for Farra Marine.
Grandweld ups its crew boat game
To compete with offshore helicopters in the offshore oil and gas market, designers and shipbuilders are upping their game, increasing the onboard creature comforts, ride, versatility and cargo-carrying capacity of a new generation of crew boats.
These trends are epitomised by new crew boats designs from Dubai-based Grandweld, which recently completed construction of a series of three 42-m GrandSuperior-class crew boats for Allianz Middle East Ship Management for charters with ADNOC.
Offered in multiple configurations, interior accommodation has ‘plug-and-play’ features for hospital rooms, security accommodation, offices and GrandMajlis, a luxurious lounge for VIPs. Grandweld says the vessels have long-range endurance, transfer up to 80 personnel and transport 60 tonnes of deck cargo.
Each of the series of crew boats for Allianz Middle East Ship Management are capable of transferring 100 passengers and 70 tonnes of deck cargo. Each vessel has three 1,081-kW engines to achieve speeds of 27 knots, and two 75-hp bow thrusters. Grandweld’s hydrodynamically foiled rudders make the crew boats highly manoeuvrable. The wheelhouse is very user-friendly with 360° visibility and ergonomic forward and aft consoles.
Earlier this year, Grandweld delivered crew boat Tamimi-6 to High Seas Marine. This is the first of a new GrandMax ‘wide body’ crewboat series. Grandweld offers this vessel in a three-engine variant called the GrandUltra, and four-engine configuration called GrandMax.
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