Greening offshore Crew Transfer Vessels (CTVs)

When the client is paying for fuel, there would seem to be little incentive to reduce fuel consumption, but this is not the case for workboat operators in the offshore wind sector. The 4C Offshore Insight Report: Greening the service vessel fleet shows that increasing pressure on competitiveness along with determination to deliver a quality service means a significant number of operators have introduced ways to reduce their operations’ environmental impact.

Some operators have invested in real-time vessel performance monitoring. Systems such as Reygar's BareFLEET provides quantifiable data to optimise performance. Not only is the mechanical performance logged, but vessel motion and comfort, and impact on turbine foundations are just some of the other metrics being made available to vessel operators and their clients. While automated monitoring is not a requirement for contracts in the offshore wind industry, it is viewed favourably by clients as it provides an independent evaluation of performance for contract negotiations. This is important to offshore wind project developers and OEMs, including Ørsted, Siemens, and Vestas, all of whom have corporate agendas to improve the environmental performance of their own operations. It is not only about the environment. Every pound or euro saved on fuel is an addition to the profit margin. With 25- to 30-year lifespans, the savings could be considerable.





Optimising current performance is the first stage. Excitingly, workboat operators in the offshore wind industry are leading on innovative vessel design. Investment in new hulls which improve seakeeping without sacrificing fuel consumption is ongoing: Mainprize Offshore, Windcat Workboats, World Marine Offshore, and Northern Offshore Services are just a few companies that have already delivered new vessels meeting these criteria in the last few years.
And it doesn't stop there. This year will see six vessels with hybrid options entering the market. CWind has gone one step further. Its new vessel, to be launched in June, will be a Surface Effect Ship (SES) with hybrid power. SES vessels are not new but are relatively new to offshore wind, currently there are only three SES vessels in the global fleet.






Fully electric vessels are still confined to other sectors such as ferries and port tenders, but one operator, Leo Hambro of Tidal Transit, has carried out a feasibility study. It supports the viability of converting an existing CTV to battery power with an electric vessel, delivering like for like performance compared to diesel. While electric may not suit every wind farm location, there are plenty of existing nearshore sites and some new sites currently under construction, which could be candidates.


The future could bring increased use of alternative fuels. The falling price of electricity from offshore wind is potentially opening up opportunities in hydrogen production, making it more readily available for use in shipping. Windcat Workboats is currently finalising the design of Hydrocat 1, which will use hydrogen in its fuel mix and will be first CTV in the market to use hydrogen as a fuel. The vessel already has a charter in place with Vattenfall, working on Hollandse Kust Zuid Holland I and II in 2022. Hydrogen could also be used to generate electrical power via a fuel cell, as can ammonia. Both fuels are potential alternatives to carbon-based fuels.


So, is it worth it?

The shipping industry reportedly accounts for around 3% of annual global green-house emissions. While this may be a small amount and the contribution from crew transfer and service operations vessels even less significant, the steps being taken by offshore wind service vessel operators are important. They are providing case studies and research opportunities whilst working in a highly competitive, commercial, and physically demanding environment. While reducing fuel consumption often starts with a need to cut costs, there is an undeniable desire among operators to lead the way in greening the service vessel fleet.


Also published by:
Workboat Association

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