For many vessel profiles, cutting emissions can’t come at the expense of range, scheduling, or maneuvering power. Battery-electric alone is not always viable for long-distance or high-demand operations. A marine hybrid propulsion system solves that gap by combining mechanical and electric power on the same shaft line, so operators can switch modes to match the real mission, not a fixed energy source.
The result is a propulsion setup that supports fuel savings and significant emission reductions while keeping operational flexibility intact.
A parallel hybrid marine propulsion system lets the propeller shaft be driven by a conventional main engine, an electric motor powered by onboard gensets or batteries, or both together when extra power is needed. Because each power source connects directly to the shaft line, propulsion is not limited by generator capacity in the way serial hybrids can be.
This architecture makes the marine hybrid system a strong fit for vessels that shift between long-distance cruising, slow steaming, and short zero-emission operations, depending on where and how they operate.
A reliable hybrid setup depends on coordinated power delivery, mode control, and safe transitions between operating states. The system includes:
Together, these elements create a marine PTO/PTI hybrid system that adjusts automatically to route demands, helping maintain efficient performance as loads vary.
Hybrid operation keeps the main engine working closer to its optimal load range instead of forcing inefficient peaks and low-load running. With electric support available for peak shaving and low-demand periods, operators reduce fuel use while maintaining schedule reliability.
Key advantages include:
Improved fuel economy through load optimisation and peak shaving
Silent, emission-free running in port or sensitive waters when batteries are included
Increased redundancy through dual power sources
Fewer hours on combustion engines, lowering maintenance demand
A hybrid setup reduces CO₂ and pollutant emissions (NOₓ, SOₓ, and particulates) by avoiding inefficient engine operation and enabling electric modes where appropriate. When running in electric mode, the system also reduces noise and vibration, including underwater radiated noise.
This supports low-emission operation without forcing a single operating strategy on every voyage.
Hybrid propulsion works best where operating demands change during a voyage and no single power source can cover every mode efficiently. It is used across ferries, offshore support vessels with high DP or maneuvering demand, yachts, tugs, cargo vessels, and ice-classed ships.
It is especially effective for:
For these profiles, a marine hybrid propulsion system provides the flexibility to reduce emissions and fuel use without sacrificing range or operational reliability.
A hybrid shaft line propulsion setup combines a mechanical main engine and an electric motor in parallel on the same shaft. Electric motor power, cooling, and installation layout are configured to match each vessel profile. Motors can be inline or geared, using permanent-magnet or induction technology, and drives and motors can be air-cooled or water-cooled.
Operating modes include engine-only, Power Take-In (PTI) electric-only, hybrid boost, Power Take-Off (PTO) generation (where the engine drives the motor as a generator), and emission-free battery-only operation when batteries are the sole energy source.
A hybrid project succeeds when the power split, operating modes, and energy supply are matched to real route demands. For ferries, tugs, offshore vessels, and cargo profiles evaluating a marine hybrid propulsion system, early system definition helps secure fuel savings, low emissions, and operational flexibility from day one.
Contact a propulsion and electrical integration expert to discuss the right hybrid configuration for your fleet.
A hybrid shaft line can be driven either by the main engine or by an electric motor in PTI mode, powered by onboard gensets or batteries. When extra thrust is needed, hybrid boost mode allows both power sources to drive the shaft together. In PTO mode, the main engine provides propulsion while the electric motor operates as a generator, producing power for onboard consumers and/or charging batteries. A hybrid power and energy management system recommends the most efficient operating mode, and automated mode transitions make switching seamless for the crew.
Core components include the main engine, electric motor, reduction gear with clutch arrangement, gensets or batteries, frequency converters and drives, and the hybrid bridge mode selector.
Parallel hybrid propulsion is designed for vessels that need more than one efficient operating mode. Because the shaft line can be driven by the main engine, the electric motor, or both together, operators can choose the best energy source for each phase of a voyage. This makes it easier to combine long-range capability with low-emission or zero-emission operation in selected areas when batteries are included.
With both power sources connected directly to the shaft line, propulsion is delivered without relying on a serial generator chain. This supports strong manoeuvring response, efficient load sharing, and smooth switching between modes as operating demands change.
For mixed or variable duty cycles, parallel hybrid operation provides a practical way to reduce emissions and fuel use while keeping range, schedule reliability, and vessel capability intact.
Hybrid systems are tailored around the vessel’s real duty cycle. Electric motor power can be configured either for maneuvering assist or for deeper hybrid capability. Energy supply can be genset-driven, battery-hybridised, or a combination.
Optional integrations include shore power charging when batteries are included, predictive maintenance tools for gensets and drives, enhanced noise/vibration packages, and integration with energy-saving propellers or nozzles. The system is also ready for future fuel engines (such as LNG, methanol, or hydrogen) and can support a gradual transition from conventional to greener operation.
Berg Propulsion Tunnel Thrusters are in service on vessels operating in demanding maritime environments worldwide. Our customer success stories demonstrate how reliable lateral thrust, robust design, and seamless system integration contribute to safe docking, efficient operations, and reduced lifecycle costs.
Frequently Asked Questions. Don’t find what you are looking for? Contact us directly.
A marine hybrid propulsion system combines a combustion engine and an electric motor on the same shaft line. The propeller can be driven by either source or both together, depending on operating needs.
In a parallel hybrid marine propulsion system, both power sources act directly on the shaft. That avoids generator bottlenecks and provides stronger flexibility across operating modes.
PTI means the electric motor drives the shaft using electrical power. PTO means the main engine drives the shaft and the motor acts as a generator to supply onboard power and/or charge batteries.
Hybrid solutions are suited to vessels with variable duty cycles, such as ferries, offshore support vessels, tugs, cargo vessels, and ice-class operations.
Yes, in selected modes when batteries are included, the vessel can operate emission-free for short periods such as port entry or sensitive waters.
We are looking forward to hearingfrom you and discussing how we can be of assistance in making sure that your fleet is fully covered.
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