CWind won the Offshore Renewables Award sponsored by F3O Offshore services at the 2020 Offshore Support Journal Conference and Awards for its hybrid-powered surface effect ship (SES)
F3O managing director David Nielsen presented the award to Daniel Smart of CWind. Mr Smart said the vessel will be operational in August 2020 and said it offered “20-25% emissions reduction” over conventional propulsion.
To achieve this reduction, the crew transfer vessel (CTV) is equipped with the world’s first hybrid diesel/electric propulsion SES developed in partnership with ESNA, a ship design company based in Kristiansand, Norway.
Speaking to Offshore Wind Journal in August 2019, CWind senior project manager Ross McDonald said achieving faster long distance travel while reducing CO2 was central to the vessel’s development. He explained that the CWind/ESNA team explored hybrid diesel/electric and hybrid diesel/hydrogen options.
Despite technological innovations that have reduced battery weight, there remains a need for a large, heavy batteries to operate vessels over longer distances. Mr McDonald noted that better battery technology could mean that a fully electric CTV comes to market relatively soon, but the current state of battery technology means that diesel engines are required to supplement the electric battery pack on the vessel for use over shorter distances.
CWind also considered hydrogen as fuel, but believes the technology is not sufficiently developed, although the vessel could be retrofitted with fuel cells using hydrogen when the technology has matured.
A hybrid arrangement enables the innovative SES design to provide battery-assisted sprint speed and enhances its bollard pull. Using battery power when suitable – when idling, on standby in a windfarm or transiting at low speed in harbour – reduces fuel consumption and emissions and reduces engine hours. This has a knock-on effect on engine maintenance because they spend less time operating inefficiently at low power.
An SES has an air cushion like a hovercraft and twin hulls like a catamaran. When the air cushion is in use, only a small portion of the twin hulls remain in the water, reducing resistance, giving the vessel greater speed and reduced fuel consumption.
Propulsion will be supplied by two Scania diesel engines, each generating 809 kW, that drive two Rolls-Royce Kamewa S50-3/CA waterjets, via marine gearboxes. Rounding out the vessel’s propulsion equipment are two 130-kW electric generator motors, one 75-kW electric power bank, and one 200-kW centrifugal lift fan used for SES operation. The energy storage system will be supplied by Corvus Energy.
The vessel will have a service speed of 27 knots and maximum speed of 33 knots, which can be increased to 38 knots for a limited period using battery power. It will have an estimated fuel consumption of approximately 330 l/hr at full speed and 180 l/hr at service speed.
For strength and to reduce weight, the CTV’s deckhouse will be built of composite material and its hull from aluminium. The vessel will have an overall length of 22 m, beam of 8.9 m and draught of 0.5 m when in cushion operation and 1.6 m hull borne.
The vessel is under construction at Wight Shipyard Company in the UK, and Ørsted, a Danish offshore windfarm operator, has secured the vessel on long-term charter.
Under the three-year agreement, which contains an option to extend the charter by two more years, CWind’s hybrid SES CTV will operate out of the Dutch port of Vlissingen serving the offshore windfarms Borssele 1 and 2 in the North Sea, starting in mid-2020.