Hybrid CTV

We currently have one Hybrid CTV Vessel and one in build.


HST Ella


HST Frances


HST Millie


The HST Hybrid Chartwell 24 is a pioneering crew transfer vessel (CTV) that refines the formula for offshore wind support.

Developed off the back of ten years of data and experience in offshore wind vessel design, alongside extensive dialogue and collaboration with wind farm owners and turbine manufacturers, the HST Hybrid Chartwell 24 responds directly to the needs of the end user. The vessel hits a “sweet spot” in size and capability that has been achieved by the most effective vessels currently operating in the offshore wind market.

The HST Hybrid Chartwell 24 is propelled by a Servogear Ecoflow Propulsor, controllable pitch propeller system. The CPP system takes power from either a high efficiency electric motor or a CAT C32 main engine. This means the HST Hybrid Chartwell 24 has the capability to operate silently, with zero emissions, as an electric boat at speed between 10 and 15 knots. Further, when operating as a diesel boat at transit speeds the boat is capable of operating efficiently and comfortably at speeds in excess of 25 knots.

Once at the offshore wind turbine or offshore substructure, the HST Hybrid Chartwell 24 is capable of delivering 19T bollard push. Coupled with the advanced hull form and superior bow height of the HST Hybrid Chartwell 24 this will allow the vessel to transfer comfortably in seas in excess of 1.75m HS.

Hybrid System Characteristics:

  • Silent (no engine noise) when operating electric only
  • Zero emission when operating electric only
  • 50% less main engine operation

Opperational Modes

DM Mode

  • Both main engines running and engaged.
  • Combinator curve no 1 in control system optimised for this mode.
  • Max available power for propulsion is 2 x main engines.
  • PM-motors available for charging installed batteries.

El Mode

  • Both main engines disengaged, and PM motors are used for propulsion.
  • Power from batteries. Combinator curve no 2 in control system optimised for this mode.
  • Limited running time depending on battery level state of charge.
  • Max. available power for propulsion is 2 x electric motors.

Hybrid mode

  • One main engine providing power to propeller, whilst it’s el-motor runs as a generator charging the onboard batteries.
  • The other propeller can be driven by the electric motor, supplied power from the onboard batteries.
  • Combinator curve no 3 for main engine driven propeller and combinator curve no 4 for electric motor driven propeller, optimised in this mode.
  • No running time limitation.
  • Maximum power available for propulsion is 2 x main engine and 2 x electric motors.