Battery-powered CTV is intermediate step to fully carbon-free operation
CWind has secured a long-term charter contract agreement with Ørsted for a unique crew transfer vessel with hybrid diesel/electric propulsion. The vessel will service the Borssele 1 and 2 offshore windfarms. The agreement between Ørsted and CWind covers an initial three-year firm charter with options available for a further two years.
The hybrid crew transfer vessel (CTV) will have a surface effect ship (SES) hullform and will operate from the Dutch port of Vlissingen. An SES, sometimes known as a sidewall hovercraft, 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. The concept behind the vessel was first highlighted by OWJ in August 2019.
CWind says developing the hybrid SES for use as a crew transfer vessel was “in response to an industry-wide push to develop and deploy innovative technology that reduces CO2 emissions while cost effectively servicing windfarms located further offshore.”
The hybrid SES achieves this through a combination of electric and diesel propulsion which, when combined with the SES hullform and heave compensation technology, is able to operate in sea states of up to 2.0m Hs, while reducing fuel burn and CO2 emissions compared with conventional designs.
The vessel will deliver sprint speed from its 1,300-kW diesel engines, which can be battery-boosted up to 1,500 kW. Significant fuel savings are achieved by reducing the hours the vessel spends with its engines operating inefficiently at low power, using battery drive in modes of operation including standby in windfarms and low speed or harbour operations. This leads to engine operating hours being reduced by 50% during windfarm battery standby. A hybrid arrangement with battery assistance also enhances the vessels’ bollard pull and push.
“The Hybrid SES is able to deliver crew faster to windfarms with improved comfort, resulting in increased operation days offshore for our client’s operations and maintenance and construction activities,” the vessel owner says.
CWind managing director, group business operations Ian Bryan says, “Our development of the vessel has been driven by listening to the market and our customers who want a greener, safer and more efficient CTV to support their commercial and green objectives.”
The hybrid SES was developed in partnership with ESNA, a ship design company based in Kristiansand, Norway. ESNA specialises in surface effect vessel development to deliver commercially competitive vessels with significant carbon reductions by design. ESNA founder Trygve Espeland says, “This design will accommodate further developments in hybrid propulsion and battery technology, ensuring it has the capability to be developed into a totally carbon-free solution in the future.”
As previously highlighted by OWJ, the CWind/ESNA team explored hybrid diesel/electric and hybrid diesel/hydrogen options for the new CTV. The team concluded that electric propulsion works best over shorter distances but, despite technological innovation that has reduced battery weight, it was not enough to counteract the need for a large, heavy battery for greater distances. However, the company believes better battery technology could mean a fully electric CTV comes to market before too long.
CWind also considered hydrogen as fuel, but at this point it believes the technology is not sufficiently developed, although a vessel such as the one chartered by Ørsted could be retrofitted with fuel cells using hydrogen when the technology has matured.
The vessel will be built by Wight Shipyard Company in the UK and is expected to enter into operation in 2020.