Charging

Vessel battery charging

Vessel charger solutions are designed for ships that have an energy storage system including a marine battery. A marine charging system works in much the same way as a charging system for electric road vehicles. Unlike alternative marine power (AMP) systems, vessel charging systems are not yet standardised and often require fast charging or DC charging, although normal charging or AC vessel charging is also possible.

There are two types of charging systems:

Manual marine charging systems

With a manual vessel charger the operator manually connects their vessel to the shore power charging station. This type of vessel charging is typically used for vessels that do not have short turnaround times. Wärtsilä is delivering a manual marine vessel charging solution for a fast, zero-emission passenger ferry as part of the TrAM Project. This will be the first marine charging system to use the CCS plug standard that is common in the automotive industry.

Automated marine charging systems

Automated vessel charging maximises the time available for charging an electric or hybrid vessel by starting the vessel charging process as soon as the ship is in range of the wireless charger. Wärtsilä has delivered wireless marine charging systems including charging towers for two zero-emission ferries operate by the Norwegian company Boreal Sjö.

Wireless charging

The Wärtsilä wireless vessel charging system replaces the traditional cable connection method. This type of marine battery charging system is particularly well suited to fully electric vessels that spend little time in port, such as ferries. Vessel charging can start the moment the ship docks, meaning that the same amount of energy can be supplied to the vessel over a longer time, reducing the total power rating requirement of the shore power charging station.

When combined with systems such as auto docking and vacuum mooring, docking and undocking becomes faster, safer and more 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

Advanced

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

Appearance

Low profile landside

Applications

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.