Hybrid version of Chartwell 24 CTV makes its debut

Written by Nick Blenkey

HST Ella [Photo (c) Rob O’Neill]

U.K. headquartered HST Marine has taken delivery of the HST Ella, the first hybrid version of the successful Chartwell 24 offshore wind crew transfer vessel (CTV) design from Southampton, U.K. naval architect firm Chartwell Marine.

The Chartwell 24 CTV series includes a Jones Act version, the first of which, Atlantic Endeavor, was delivered to Quonset Point, R.I., based Atlantic Wind Transfers (AWT) earlier this year by Blount Boats, Warren, R.I.

The HST Ella, just delivered by Isle of Wight shipbuilder Diverse Marine, is an aluminum hulled catamaran with dimensions of 25.1 meters LOA by 8.63 meters beam.

Its innovative hybrid propulsion system has the following main components:

Main engines 2 x Caterpillar C32 Acert
Installed power 2,162 kW
Gearboxes 2 x Servogear HD295PTIL
Propellers 2 x Servogear 1,200mm diameter
E-motors 2 x Danfoss Editron 200 kW
Battery strings 4 x Corvus 46.4kWh

In a market first for a newbuild crew transfer vessel, the diesels uses hydrotreated vegetable oil (HVO30) as fuel.

“Modern crew transfer operations in offshore energy increasingly require proven vessels with a powerful presence on the water. At the same time, a future-proof fleet consists of vessels with strong green credentials as the goal of emissions reduction continues to move up the agenda,” says HST CEO Tom Nevin. “Rapidly maturing hybrid technology means that environmental consciousness can sit hand in hand with operational excellence, and in the HST Ella, we have a vessel that delivers both, following a consultative design process with Chartwell Marine, and a high-quality build at Diverse Marine.”

The HST Ella has a transit speed of 10 knots on electric propulsion and 30 knots on diesel, while during port operations, the vessel’s electric operation mode allows for quiet and zero emission low speed maneuverability.

Advanced CTVs such as the HST Ella are increasingly expected to perform a range of auxiliary duties alongside personnel transport. The vessel is able to carry 24 industrial personnel alongside a maximum payload of 15 tonnes, ensuring maximum versatility when supporting offshore wind operations.

Following its launch, the HST Ella is set to begin its maiden contract at the East Anglia 1 (EA1) wind farm.

“Whether designing a diesel-powered CTV with an innovative hydrofoil system propelled by waterjets, or, as in this case, a large hybrid-electric CTV using HVO fuel with controllable pitch propellers, we always look to ensure that the proven characteristics of the Chartwell 24 platform are built in,” said Andy Page, Managing Director, Chartwell Marine. “Designing for hybrid operations brings specific challenges, but our central philosophy is that we design with the vessel’s eventual operational profile front and center, and we have been proud to work with Diverse Marine and HST to incorporate lessons learnt from best practice CTV operation into this vessel.”