18m Crew Transfer Vessel Hybrid Electrification
A concept study converting a diesel workboat to a battery-diesel hybrid. The question was not “can it be electrified” — almost anything can — but whether the vessel’s real duty cycle made a hybrid drivetrain worth the weight, cost and complexity. The engineering answers that with numbers, not optimism.
Does the Duty Cycle
Justify a Hybrid?
The operator was considering a hybrid conversion for an 18m crew transfer vessel, driven by fuel cost, emissions pressure and increasing client expectations around lower-carbon offshore operations. The missing piece was a quantified picture of whether the vessel’s actual operating profile suited hybridisation.
A vessel that spends most of its day at steady transit power is a poor hybrid candidate; one with long idle, standby, harbour and manoeuvring periods is a much stronger one. Isca’s first job was to characterise the duty cycle honestly, then size the battery and hybrid architecture against that real operating profile.
Modelling the vessel’s typical day showed approximately 62% of operating time at low load, the band where a battery-diesel hybrid system can displace diesel most effectively. That figure became the basis for the energy model, battery sizing and commercial case.
Sized to the Load.
Battery sizing is a balance: too small and the hybrid system rarely helps; too large and the vessel carries dead weight and unnecessary cost. These figures define where that balance landed for this concept and show how duty cycle, power demand and added mass were treated together.
- Daily energy demand
- 420 kWh
- Usable battery capacity
- 180 kWh
- Peak electrical load
- 240 kW
- Genset rating retained
- 250 kW
- Added system mass
- 2,200 kg
- Indicative fuel reduction
- 28%
What the Study Produced.
Duty Cycle Analysis
A characterisation of how the vessel actually operates, broken down by transit, standby, manoeuvring, harbour and low-load operation.
Energy Demand Model
A model of daily and peak energy demand, used as the basis for battery sizing, generator operation and expected fuel displacement.
Battery Sizing Report
Recommended usable battery capacity with the engineering reasoning, including the trade-off against mass, installation volume and cost.
Hybrid Architecture
A single-line concept for the battery-diesel architecture, including generator role, charging path, propulsion interface and operating modes.
Charging Strategy
How and when the battery is recharged against the vessel’s operating pattern, including shore connection, generator charging and operational constraints.
Concept GA Impact
Arrangement implications of fitting the battery system, including space claim, mass, access, ventilation and stability flags for the next stage.
Profile to Concept.
Characterise the Duty
The operating profile was broken into duty bands before any equipment was sized, making the suitability case evidence-led from the start.
Energy Demand
Daily and peak energy demand were modelled to establish the load case that every battery and generator sizing decision rests on.
Battery & Architecture
Battery capacity and the diesel-electric operating architecture were sized against the modelled load and practical operating constraints.
Arrangement Impact
The concept was checked against space, mass, access, ventilation and stability implications so the next stage starts informed.
The Engineering
Reasoning Behind It.
Marine + Electrical in One Team
Hybrid conversion sits where naval architecture meets power systems. Isca considers the battery sizing, installation mass, power architecture and vessel impact together, not in separate silos.
We Lead With the Duty Cycle
The honest first question is whether a hybrid system suits the vessel at all. Starting there protects the client from a conversion that looks good on paper and underperforms in service.
Weight Is Engineering, Not an Afterthought
Batteries are heavy. We carry the added mass through to its arrangement and stability consequences in the same study, not as a surprise later.
A Concept That Can Be Built On
The output is structured so the next stage, whether feasibility refinement or detailed design, starts from sound numbers rather than reopening the basic suitability question.
Adjacent Studies.
Considering a Hybrid?
Before committing to a conversion, the question worth answering is whether your vessel’s duty cycle justifies it. That is where we start.
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