Damen Proposes Vessel-to-Vessel Charging for Offshore Wind Farm CTVs

vessel-to-vessel charging
Concept call for the smaller CTV to recharge vessel-to-vessel to the larger service operations vessel (Damen)

Published Jun 13, 2024 7:43 PM by The Maritime Executive


One of the limitations of introducing fully electric Crew Transfer Vessels is the lack of charging options for the vessels while on-site at wind farms. While several technologies are being developed for charging buoys or connections to a wind turbine or substation, Damen Shipyards Group points out that the technologies, specifically turbine-mounted chargers, are not yet widely available.

With wind farms moving further offshore, charging will be required to use battery-powered transfer vessels or Commissioning Service Operations Vessels. Damen Shipyards Group developed a design for vessel-to-vessel charging which they believe offers operators a new option to incorporate electric vessels and reduce emissions at their wind farms.

Installing a large battery system on board a CTV Damen highlights is a challenge, given the weight and space restrictions. Installing the system to the much larger, less space-sensitive CSOV Damen says gives the smaller vessel access to the energy it requires without compromising on capabilities.

“Offshore charging is an essential feature for a fully electric CTV operation. Typically, this would be dependent on charging infrastructure being present at an offshore wind farm,” Mark Couwenberg Product Manager for Service Operations Vessels at Damen explains. “Our unique position as builders of both CTVs and CSOVs led us to the idea of placing the charging scope within our assets. This can be done with both a conventional, diesel-powered CSOV, or with a fully electric version.”

Following personnel disembarkation, the CTV would connect to the charger on the larger vessel using a highly automated process. It is expected that charging could take place in 2 to 3 hours, depending on the operational profile.

The charging system that Damen has applied to its concept is developed by UK-based MJR, a specialist in offshore charging systems. The CTV would connect via a bell mouth that catches the charger that is lowered from a reel on the aft deck of the CSOV.

They point to advantages of the vessel-to-vessel approach, including easier access to the stern of the CSOV versus the charging connection which is typically higher on the monopole of the wind turbine. The CSOV would also be able to reposition based on wave conditions, enabling the CTV to charge in a more sheltered location.


Damen designed an electric Fast Crew Supplier


Damen introduced the charging concept as it also unveiled designs for a larger, fully electric Fast Crew Supplier for crew transfers. It uses the Axe Bow hull shape with a rounded tunnel which they say reduces wet deck slamming and provides minimal resistance in the water. They increased the length of the vessel which provides space for a larger deckhouse and more deck capacity. 

The design features a full electrical Volvo IPS system, enabling the CTV to sail exclusively on battery power. The vessel will be able to sail at high speeds to offshore wind farms up to 25 nautical miles from shore. On arrival, it will recharge at a charging system integrated into a turbine, substation, or SOV before returning to shore.

Purus has already ordered three diesel-electric versions from Damen. The company also reports that while methanol engine technology has not yet reached maturity for these vessels, it has developed designs for a methanol propulsion version. When the engines are ready, Damen notes its hybrid design is prepared for a fast conversion.