Wireless Charging On The Water

By Bo Svensson

In what is thought to be the first commercial ferry operating with high power wireless battery charging capability has been successfully tested by Wärtsilä in Finland, the developer of the charging system.

The tests were carried out on the 279 ft. (85m) long MF Folgefonn in Norwegian waters during the end of August / early September, 2017. The ferry is owned by Norled, one of Norway’s largest ferry operators.

MF Folgefonn is a commercial ferry in normal operation and is for the moment operating in a plug-in hybrid configuration. It can be run in diesel electric mode, and in a fully electrical mode.

The double ended car ferry was converted in 2014 from a diesel electric ferry to a complete plug-in hybrid and plug-in electrical ferry. The technology demonstration has undergone successful testing during normal operation for over a year.

Wärtsilä’s contribution to the MF Folgefonn project was the concept development, including the inverter systems, the hybrid control, battery package and systems, power transfer and land-based energy storage system as well as the integration of the onboard systems.

The ferry is equipped with four, 500 kW diesel engine electrical generators complemented by a 1 MWh battery system, which is charged by a plug-in device from shore. The two electrically controlled propulsion motors are each rated 750 kW. And now Wärtsilä has successfully tested its automatic wireless induction charging system on the hybrid powered coastal ferry.

“During recent years, wireless charging has been introduced for cars, busses and trains. We have now made this possible for marine vessels,” said Ingve Sørfonn, senior technical officer, Electrical & Automation Services, Wärtsilä Marine Solutions. “The main benefits for customers are up to 20% more utilization of the available charging time, increased operational safety, and greater system reliability. There is an ongoing trend to equip coastal ferries with battery powered and hybrid propulsion, since they are particularly affected by environmental regulatory demands. Wireless charging will, therefore, create considerable value for operators of hybrid ferries.”

Wireless charging eliminates the cable connection between the vessel and shore, thereby securing and facilitating safe connections and disconnections. It also reduces maintenance since wear and tear to physical connection lines is eliminated. The integrated Wärtsilä system is based on inductive power transfer and is capable of transferring more than 1 MW of electrical energy.

Inductive charging (wireless charging) uses an electromagnetic field to transfer energy between two coils. A sending induction coil is used to create an alternating electromagnetic field, and a second induction coil takes the power from the electromagnetic field and converts it back into electric energy. To manage longer distances between sender and receiver coils the inductive charging system uses resonant inductive coupling.

The Wärtsilä system is designed to maintain efficient power transfer at distances of half a meter between the two charging plates. The sending charging plate is carried by the arm of a robot located at the quay, while the receiving charging plate is located in the quay side of the vessel. No other wireless charging system is as powerful, or capable of maintaining the transfer of energy at such a distance.

“For Wärtsilä, this wireless charging revolution focuses on coastal ferries, a segment of the transportation industry that is well-suited to the technology because of short stop-and-go schedules,” said Cato Esperø, sales director, Wärtsilä Norway.

The project has been partly funded by Innovation Norway, a Norwegian funding institution.

For more information: www.wartsila.com