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Charging Marine Vessels

Charging is relevant for vessels with an energy storage system (battery). The vessel recharges its batteries whilst in port, which allows the vessel to sail with zero-emission for a defined period. Charging systems are typically used in a closed infrastructure, for example a ferry or tug operating close to shore or on a defined route. These systems, unlike alternative marine power (AMP) are not standardised yet and often require fast charging or DC charging. When there is plenty of time available normal charging or AC charging can be used. The concepts are similar to electric cars but with a higher magnitude in marine vessels.

There are two types of charging systems:

Manual charging systems: Here an operator manually connects the shore charging station with the vessel. This is the easiest option but requires time to connect which reduces the charging time so is often used for vessels that do not have short turn arounds. Wärtsilä will deliver this solution to the world’s fastest full electric passenger ferry as part of the TrAM Project and will be the first time the CCS plug standard will be used which is common in the automotive industry use the well know CCS plugs the standard in the automotive industry.

Automated charging: Often time is of the essence when charging an electric or hybrid vessel, requiring as much of the docking time as possible for charging. An automated charging solution can increase this time dramatically by starting the charge as soon as the vessel comes into range of the wireless charging station, not requiring any manual intervention. Wärtsilä has and is delivering wireless charging solutions including charging towers used for the full electric Boreal ferries. 

Wireless charging

Wärtsilä has developed a wireless charging system for easy transfer of power from the shore to ship, replacing the traditional cable connection method. This technology is particularly suitable for fully electric vessels using batteries which spend little time at the dock, such as ferries for example. Using the Wireless Charger, power transfer can start the moment the vessel is docked rather than having to wait until cables are connected. This means that the same energy can be supplied to the vessel over a longer time, which reduces the total power rating of the shore connection system.

When combined with systems such as auto-docking and vacuum mooring then the process of docking and undocking becomes even more safe and efficient.

Wireless charging solution with tide compensation device

Charger concepts

The wireless charger has a sending coil arrangement on-shore mounted on a hydraulic arm with y and z axis movement. The sending coil is connected to a nearby power electronic where grid connection and alternatively shore based energy storage can be connected. The input voltage to the power electronics is 690V 50/60Hz.

On the ship side there is a similar coil arrangement where the receiving coil plate is mounted flush with the side of the vessel. The coil arrangement is connected to a rectifier for DC conversion.

The basic principle is following:

  • Current in inductive sending coil creates a controlled magnetic field
  • Magnetic field from sending coil creates a current in the receiving coil
  • High frequency current flowing in the inductive coil is converted to DC Power
  • Energy is stored in the ship batteries

This system can transfer more than 2 MW with a distance between the coils of about 4- 500 mm.

Capacity of the Wärtsilä wireless charger
One standard basic unit delivers 2.5MW. Landside and onboard connections are normally 690VAC, but that can be adapted with transformers and there is also the possibility for a common DC bus connection. At 690V, 2.5MW corresponds to 2500Arms three phase. The power rating of the charging system can easily be increased by using several units in parallel, or by specifying a larger unit with an increased active coil area.

Key Benefits

The Wärtsilä Wireless Charging System has the following benefits:

Lifecycle cost

  • Low wear
  • Low maintenance
  • Low lifecycle cost

Safety and availability

  • High safety
  • High availability
  • Excellent weather protection
  • No cable connections ship to shore
  • Encapsulated insulation, no creepage distances exposed to weather
  • No galvanic connection ship to shore
  • No consequences of relative movement ship vs shore
  • Immune to ice and snow
  • Prepared for de-icing


  • Prepared for autonomous operations

Grid cost / landside battery cost

  • Low power/energy ratio –may avoid weak grids upgrading – may avoid shoreside battery
  • Active rectifiers stabilize grids
  • High charging time/docking time ratio


  • Low profile landside


Wireless charging is best suited for applications where a high number of charging periods per day are necessary. This is especially true in harsh marine climates, since wireless charging systems experience no contact wear and have no exposed electrical contacts. Ferries definitely fall within this category, as do tugs and other coastal vessels, depending upon their actual operational profile. More advanced applications may also benefit from the advantages of having a total separation between the primary and secondary systems. With the introduction of more automated, and even autonomous vessels, inductive charging is designed and tested to offer a completely automated procedure where no human interaction is necessary.

Frequently asked questions


How much jetty infrastructure work is needed, and is a high energy power supply needed from the grid to the jetty?
What are the charging and heat losses, the cycles available, and the battery life?
What are the losses and system efficiency of the wireless charging system?
What are the options for locations onboard the vessel and on the jetty?
What is the expected operational life of the equipment, and the average annual maintenance costs for it?
Does proximity to eg. navigation, automation, electromagnetic systems or electromotive fields, medical devices, mobile phones etc. cause any kind of interference/danger to the devices or personnel?
Is the wireless charging system affected by extreme weather conditions or eg. possible ice build-up?

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More answers to common questions about wireless charging

Didn’t you find the answer you were looking for in the above FAQ section? Download this full document where we have gathered even more frequently asked questions and answers regarding Wärtsilä’s wireless charging system for easy transfer of power from shore to ship.

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