4C is now TGS

We are excited to announce a significant milestone in 4C Offshore's journey. Our integration into the TGS family marks the beginning of a new era in offshore wind market intelligence.

Learn what this means for you!

Could offshore wind developers cut O&M costs using a ‘midi’ sized SOV?

By: Sue Allen 08/03/2024 Sue Allen, Senior Market Analyst at TGS | 4C Offshore

General Logistics Vessels

Image 1
In a sector where bigger is usually perceived as better, could a smaller vessel, which would have lower build and operational costs, be an alternation vessel support solution when budgets are under pressure and profit margins tight? Chartwell Marine has developed a 'midi' size SOV to offer a choice for offshore wind farm operators.

Background

Larger capacity turbines further offshore, along with more efficient installation and operation has led to falling cost of electricity from offshore wind. In line with this, the size and capability of vessels used in the sector has had to increase to meet the changes demanded by clients. This is particularly true for the service ships used to transfer and support offshore maintenance personnel.

The early offshore wind projects were located near to shore and ports, so could be supported by technicians being transport to sites daily. The demand for these services led to the development and growth in specialist Crew Transfer Vessels (CTVs), essential for safe and efficient transfers. Then, as the near shore locations were built out, the time spent travelling needed an alternative solution. In 2015, the new solution arrived in the sector – the Service Operations Vessel (SOV).

At present, there are 29 SOVs and 14 CSOVs (Commissioning SOVs) in operation across the world with 53 more in the pipeline. These specialist vessels feature a Walk to Work (W2W) system, capacity for around 60 – 90 technicians in high standard accommodation, and excellent seakeeping for the safety and well-being of personnel onboard. In general, SOVs target long-term O&M contracts, often working on two-week rotations. CSOVs are used to support turbine commissioning work, as well as other construction activities such as cable pull ins and substation commissioning.

C/SOVs are becoming increasingly critical to efficient operations. Today’s 10 MW capacity turbines and tomorrows 20 MW turbines mean significantly higher loss of revenue during break down and maintenance periods. Therefore, operators need vessels that can cope with a range of sea states to ensure high levels of offshore accessibility.

Unfortunately, large vessels come at a cost, not only in terms of build, also in operational costs.

A new SOV solution?

Ships architect firm Chartwell Marine is well known in offshore wind, especially as a leading designer of CTVs with around 30 vessels in the water or under construction. Its designs include the innovative Seacat Columbia where Chartwell worked with BAR Technologies to bring ocean yacht racing efficiencies to offshore wind. Aware of the market demands, Chartwell’s naval architect Andy Page spotted a potential gap in the vessels supplied to the market. A space lying between a large CTV of ~35m and an SOV starting at ~70m.

Image 2

Andy started working on CTV designs in 2010, when the vessels were typically 16-18m loa, and now in 2024, 24-28m is commonplace, and even up to 39m. The downside to vessels of this size, is that they need to perform at high speed and have a large fuel capacity, and this significantly increases fuel consumption. While these vessels are in demand in the sector, developers and vessel operators are looking to reduce fuel use and emissions. This led Andy to consider whether a midi sized SOV could provide solution. In a sector where bigger is usually perceived as better, a smaller vessel would have lower build and operational costs, making it an ideal solution when budgets are under pressure and profit margins tight. But it is only a solution if the vessel can perform to the required standard.

Design process

Andy set about finding alternative option – a smaller vessel with the stability and performance of a larger one. Engaging with other stakeholders including North Star, Clarksons, Seaspeed Marine and Voith, as well as project developers, the Chartwell team took a ground up approach, initially considering around 30 monohull forms, before arriving at a solution that incorporates a low waterplane shape that broadens above waterline, effectively minimising and dampening roll motion. This form was taken through to the development of a 1:28 scale model for tank testing. To prove the Midi-SOV's suitability, extensive simulation and model testing was conducted in collaboration with Seaspeed Marine Consulting. During the testing, the model was free to move in the tank and performed well on transit and transfer trials, confirming the viability of the hull form.

Development of the concept is on-going and well advanced and set to be ready for build this year. The vessel will be able to accommodate 36 passengers plus 20 crew, with space for the storage of components as well as welfare options such as gym and other onboard facilities.

Integral to the design are the transfer solutions. The vessel would have a W2W system as well as a daughter craft. The W2W will not only be able to reach similar heights achieved by bigger vessels the Midi SOV will have an additional benefit. Many older offshore projects have lower landing platforms making the use of W2W difficult for standard SOVs. The midi version would be able to support operations in these locations, offering further options for OWF operators.

To ensure the vessel will be able to meet future emissions requirements, the design can be configured for alternative fuels such as e-Methanol, or electrification.

Going to market

Image 3
The smaller sized SOV concept is not entirely new with one vessel in this range already operational in Belgium - Groene Wind at 61.7m loa. In addition, there are two more SOVs of similar size currently in build - 56.9m Windkeeper 1 & 2. However, all three vessels are SWATH designs which are known for excellent seakeeping but tend to be more expensive to build and are considered more difficult to operate.

Chartwell is well established in the CTV space, although is not well known for larger vessel design. A serendipitous meeting during the naming ceremony of North Star’s SOV Grampian Tyne, between Andy and Thomas Obsnik from VARD, a leading designer and shipbuilder, led to the two vessel designers collaborating on taking the project to market. VARD is well establish in the C/SOV market having designed almost 30 SOVs to date, including vessels for North Star, Purus Wind, and Edda Wind. So far, the midi SOV design has been well received by project developers who have expressed an interest in the design capability.

Ready for construction

The smaller size has other gains in terms of construction. More shipyards would be in the position to bid for the work that would not be able to accommodate a standard SOV. This is particularly advantageous for the US market, potentially allowing construction on the east coast. The vessel is designed to be Jones Act Compliant, Americanised, and subsequently ready for production in US Shipyards. As build prices are significantly higher in the States, the reduced size would result in a significant cost saving.

Is this the perfect solution for the future?

Andy Page, Director, Chartwell Marine, said: "Never before has there been such a pressing need to develop offshore wind vessels that are reactive to evolving operational and financial conditions. Far from being a disaster, we see the failure of the UK’s Round 5 offshore wind CfD auctions as an opportunity for the maritime industry to respond to the fact that developer costs are skyrocketing.

“The Midi-SOV offers a cost-efficient alternative to full-sized SOVs, contributing to the industry's overall sustainability. We’re putting a strong emphasis on having these vessels manufactured locally, with US-built vessels Americanised for the US market and Europe-built vessels for European operations. Chartwell is leading the charge in CTVs; VARD are a pioneer in the SOV space — so the Midi-SOV is the best of both worlds. It is another tool in the toolbox for project operators.”

Runar Vågnes, Senior Vice President Sales VARD, said: “With the introduction of the Midi-SOV, Chartwell Marine and VARD are leading the way in opening a new segment in the offshore wind industry enabling sustainable business at sea, bringing forth a vessel that combines innovation, efficiency, and sustainability. Our partnership signifies a commitment to providing operators with state-of-the-art solutions that slot into new and specialised roles that are emerging in markets across the globe.”

To discover unique insights about vessel supply and demand, project development and much more, click here.

Premium

4C Offshore Premium, our most popular subscription, gives you full access to use the 4C Offshore WebApp which includes exclusive offshore wind, transmission and vessel reports, news and downloads.

Request a 30 minute Demo

Could offshore wind developers cut O&M costs using a ‘midi’ sized SOV?

Back to News

Trending News!