Hybrid CPP Propulsion Systems

Sustainable Propulsion optimised for the running condition, boost energy efficiency and reduce emissions.

A hybrid system enables ships with variable power requirements to run at high propeller efficiency.

Hybrid Propulsion

Hybrid Propulsion is simply the use of two (or more) different power sources to run the propellers.

Traditionally the majority of commercial vessels are equipped with either diesel engines or electric motors for running of the propellers. By combining these two power sources in one system we get a hybrid propulsion system. Additional energy carriers could be battery packs, gas engines, permanent magnet motors, or others.

The system configurations may vary from simple single screw systems to complex configurations with a large number of operational modes available. A hybrid propulsion system enables engines and propellers to run optimally over a wide power range.

The hybrid propulsion systems benefit of the best from two systems; the combination of electric propulsion and diesel drive.

A hybrid propulsion system based on one diesel engine and one frequency controlled electric motor is a simple and efficient solution. Combining a battery pack to the configuration will further increase the system flexibility and the ability to optimise the energy consumption during operation.

How to build a Hybrid CP-Propulsion System?

By using a Brunvoll gearbox with multiple PTO/PTI options, or a twin-in singel-out gearbox there are multiple possibilities to build the optimum system satisfying the right power requirement for the specific vessel.

All Brunvoll Hybrid Propulsion Systems are tailor made for the operation profile of the specific vessel, with any power source whether it is diesel, electric, battery or gas.

Why is Hybrid Propulsion efficient?

A Hybrid Propulsion system allows for the highest energy efficiency provided the right power sources are selected to serve the range of operational conditions from lying idle in port to the need for full power in heavy operations at sea.

Brunvoll Hybrid Propulsion System
A Brunvoll Hybrid Propulsion system consisting of two CP-Propellers driven by a "father and son" main engine combination at each of the twin-in single-out gearboxes, in addition to one combined generator/electric motor at each gearbox for PTO/PTI functionality. Such a system allows for numerous operation modes and efficient operation.

Environmental and operational profit

By adding batteries to the hybrid propulsion system the configuration can be designed for further profit from reduced fuel consumption, reduced running hours at the main engine and thereby reduced maintenance, higher redundancy, need for less power in the gen.sets, smoother operation of the gen.sets or main engine by using the batteries for peak shaving.

Diesel-mechanical (DM) mode
- with diesel engine for propulsion and Power Take Out (PTO)

  • In DM mode the diesel enging is running the propeller and the PTO.
  • The PTO is running the generator which feeds electric power into the vessel’s grid to either to assist the existing generator sets or the remaining energy can be stored into batteries for later use.
  • The PTO can also be used for running a hydraulic pump.
a) Diesel-mechanical operation - the diesel engine is running the propeller
b) Diesel-mechanical operation - the disel engine is running the propeller and the PTO for energy to the switchboard for other consumers.

Diesel-electric (DE) mode
- with the electric motor running for propulsion in Power Take In (PTI)-mode

  • In DE mode the onboard generator set is powering the electric motor in a PTI-mode. This mode is ideal for slow steaming with a generator running at optimum speed.
  • Fuel consumption is kept at a minimum and the running hours on the main engines are reduced significantly.
  • The PMS/EMS system can use excess power from generators to store energy in the batteries if the grid load is below optimum generator load.
  • In case of requirement for peak shaving (when the vessel needs more power for a short time), power from batteries can be used instead of starting the next aux generator.
  • Making sure use of the aux generator(s) are at all time optimized. The EMS system will adjust number of running generator to the grids power load.
c) Diesel-Electric - the electric motor is running for propulsion in PTI-mode. This mode will also function as a Power Take Home mode (PTH)

Boost mode
- with combined power from diesel engine and electric motor in PTI-mode

  • Boost mode is designed according to the operating profile of the actual vessel. The configuration allows for flexibility in selecting a smaller diesel engine which supported with the required additional power from the electric motor achieve the required maximum propulsion power.
  • When maximum propulsion power is only incidentically required this setup saves fuel consumption, engine room space and CAPEX as a result of the smaller diesel engine.
  • In boost mode the diesel engine and the electric motor powered by either the generator sets or from the battery package are running the propeller in maximum designed speed. This mode is ideal for high speed steaming with the diesel engine running at optimum speed boosted by the electric motor.
  • The EMS/PMS systems will control the boost power source by adjusting to the actual power demand, and optimize utilization of available power from stored battery power and running generators.
d) Boost mode from generator sets - combined power from diesel engine and electric motor is running the propeller
e) Boost mode from battery pack - combined power from diesel engine and elelctric motor is running the propeller

Electric battery mode
- with electric motor for propulsion in PTI mode powered by the battery package

  • In Electric battery mode the battery package is powering the electric motor. This mode is meant for low speed operations in short time with frequent manoeuvring in e.g. harbour areas, or for long time silent cruising while sightseeing, or in emission controlled/restricted areas.
  • Electric battery mode is also useful when vessel is alongside in harbor.
  • The effect and range is depending on the designed power in the battery package, which can be easily expanded by adding standard modules. Modules are stackable, self-extinguishing, with integrated cooling and battery management.
  • Battery status is continuously monitored by the EMS system. When battery reach a low level SOC (state of charge) a generator will start and charge the battery to full again under optimum load to restore batteries SOC.
f) Electric battery mode - electric motor for propulsion in PTI-mode powered by the battery package

Starter characteristics

Direct On-Line starter

Starting current:

5-10x Nominal motor current (IN)


Low price and high starting torque


High in-rush current


The Direct On-Line (DOL) starter consists of a contactor and a protection device such as a circuit breaker. The contactor is energized when the start button is pressed, and the full line voltage is connected to the motor. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge

Star-Delta starter

Starting current:

2-3x Nominal motor current (IN)


In-rush current reduced with approx. 60% compared with DOL


Reduced starting torque


The star-delta starter method applies reduced voltage to the motor, thus reducing current, during startup. This method requires that both ends of motor winding terminals are available. When connected in star each winding has less voltage (1 / √3 ~ 60%), and thus will have reduced starting current and torque. When full speed is reached the motor is connected in delta, having full torque available. Propeller pitch can be increased, and load applied when motor is connected in delta. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge


Starting current:

2-3x Nominal motor current (IN)


In-rush current reduced with approx. 60% compared with DOL


Reduced starting torque


Auto-Transformer also applies reduced voltage in steps to the motor during startup. The transformer voltage ratio can be designed to the application, typically having a 50-70% motor voltage during startup. The motor consumes less current at a lower starting voltage. For example, with a 50% tap on the Auto-Transformer, the motor draws half its rated current, or about 25% of what it would draw with a DOL starter. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge

Electronic soft starter

Starting current:

2-2,5x Nominal motor current (IN)


In-rush current reduced 


Reduced starting torque.
Based on electronics


An electronic soft starter is a starting device that controls the way electricity is provided to the motor by using active switching devices such as thyristors. The device works in both in-line and in-delta configuration modes in three-phase motors. 

This starting method is ramping up the motor voltage in the starting sequence resulting in a reduced start-up current, allowing for a smooth and surge-free increase in motor torque. The voltage dips, stress, and wear and tear on the mechanical parts are all reduced as a result. Due to the thyristors there will be harmonic distortion of the current, and the influence on system voltage will depend on starting current and system impedance. Motor is started with propeller in zero pitch position (IZP).

Click the images to enlarge

Frequency converter starter

Starting current:

0,5x Nominal motor current (IN)


In-rush current reduced.
Full speed and torque control


THD generated, filters required.
Based on electronics


This is an electronic-controlled approach for starting asynchronous motors smoothly. It controls the frequency and current for the motor with electronics inverter circuits, avoiding large startup current. The thruster system's mechanical parts will be protected from high load because of the smooth start-up, and the this will also reduce the load on generators during startup compared to line-starter options. Depending on required performance torque and current may be below nominal values during startup. This is the high-end solution for the starting the thrusters, giving benefits such as smooth start, better energy economy, reduced wear and tear and process optimization.  Other benefits include motor speed stability during load changes and a longer motor life overall. Motor is started with propeller in zero pitch position (IZP).

Frequency converter starters may have different interface towards the main switchboard where 6-pulse rectifier is the most common, but both 12/24 pulse and Active Frontend (AFE) are used.6-pulse starters are the most common type, widely used due to the compact design and availability.The disadvantage with the 6-pulse starter is the increased THD during startup, particularly in smaller power system with large thrusters this might be an issue. 

To mitigate the THD a 12 or 24 pulse transformer and rectifier may be chosen, typically used for larger thrusters in larger ships. 
Frequency converter starters with active front end guarantees sinusoidal current and does not require a transformer. The AFE rectifier and LCL filter is more spacious than the 6-pulse rectifier and is suitable for high end solutions and ships with relatively small power system compared to thruster power.

Click the images to enlarge

Selecting the right system

– Essential parameters influencing on energy efficiency

Optimum energy efficiency

Energy efficiency depends on a range of parameters from hull resistance, desired speed, power setup with fuel type, engine type and corresponding fuel diagram, configuration of the propulsion lines and systems, hydrodynamic conditions and operation profile, to name some of them.

Hybrid propulsion systems varies from simple systems with a few operation modes to the more sophisticated and complex systems with numerous running modes for a wide range of operations.

Consider the vessels operation profile

Any vessel with varying working conditions require flexible solutions in order to execute all tasks in the most efficient way.

Analyse the yearly operation profile of the vessel by how many days in the different conditions.

Evaluate the requirement for energy sources for the different tasks and design your system according to the ship’s actual service profile.

Hydrodynamic conditions

Brunvoll propellers are all designed to fit the specific vessel. Brunvoll bases its hydrodynamic expertise in propeller design on calculation methods of the latest hydrodynamic theories and tank test results.

Why reduce zero pitch loss?

In a CP-propulsion system reducing zero pitch loss is essential, which means to use minimum of energy just to rotate the propellers without giving thrust to the vessel.

No items found.

Technical Information

Interested in further information about this product?
Download the product sheet available to see more


Selected Brunvoll references

See all references
Related content

Read more

Related Products

See all products


Please contact us for any further information you may require about this solution

See all contacts
Vidar Liaskar

Vidar Liaskar

VP Sales, Brunvoll Volda AS

+47 952 57 129
Arnfinn Brautaset

Arnfinn Brautaset

Sales Manager, Brunvoll Volda AS

+47 915 77 678
Per Endre Woldsund

Per Endre Woldsund

Sales Manager, Brunvoll Volda AS

+47 905 72 814

Curious about this product?

Request for information about our solutions, products and services

Send request