Ryfylkefergen – a battery ferry for full day operation without charging

Our latest newbuild, “Ryfylkefergen” is a LMG 27-DEH design battery-hybrid plug-in double ended car and passenger ferry that is ordered at Westcon Shipyard by operator Norled to be delivered in 2022.

The vessel is designed for zero emission operation with batteries being charged by hydropower-generated electricity from the Norwegian grid, but unlike other battery ferries this one will only be charged at night. The ferry is 45 m long and 12 m wide with capacity for 97 passengers and 27 cars (alternatively 2 x 50-ton trailers). As for the MF “Hjellestad” (LMG 16-DEH design) the ferry is built in aluminum according Light Craft Class rules in order to reduce weight and by this also reduce propulsion energy consumption. The vessel design as a whole including hull lines, structures and systems are designed for minimum energy consumption – which is vital for obtaining a cost-efficient solution without larger batteries installed than strictly necessary.

The propulsion system consists of one azimuth thruster with L-drive in each end that are powered by vertically oriented and frequency-controlled PM type electric motors. The electric system is based on DC-grid technology and includes two fully redundant main switchboards that are fed from each their Li-Ion type air cooled battery pack in addition to each their standby diesel generator set running on 2nd generation biofuel. Shore charging is carried out when ferry is resting overnight through manual type plug system, where shore plug is arranged in cantilevered swing-out boom in end terminal.

All in all, we believe that the ferry can be operated with an energy consumption that is about half of a traditional diesel-powered ferry of same size. This is achieved by optimizing hull shape through CFD analysis, selecting efficient propulsion solution, minimizing aluminum hull weight by maximizing use of extruded panel profiles, and generally reducing hotel- and auxiliary loads to a minimum. Of energy efficient features used on board it can be mentioned heat pump and demand controlled HVAC system, frequency driven electric motors (main and auxiliary systems), LED lights, waterborne heating, hull-integrated keel cooling system (instead of sea chests), recessed sacrificial anodes, silicone based antifouling bottom paint system and more.

The overall requirement from Norled is a zero-emission vessel able to operate in pure battery mode for a whole day without charging, but also with full standby capability on biofuel for normal operation if shore charging should be unavailable. The owner also requires a vessel with very low energy consumption which will be obtained with the solutions as previously described. This is most important for keeping vessel costs as the battery package able to store energy for a full day’s operation is a dominant cost item.

It is also a requirement for the ferry to serve a large number of ports, including some with traditional car ferry linkspans and some ordinary quays. Up to 25 ports may be visited on a day. For this reason, the ferry is designed with interface for ferry linkspans in one end and combined ferry linkspans and RORO ramp in the other. A forklift truck will be carried with the ferry to load and unload pallet cargo. Additionally, a crane is arranged for loading and unloading of general cargo that also is expected as part of its service.

The ferry will have a crew of up to 5 persons and will operate in restricted waters within Norwegian flag’s trade area 2. It will operate in the Ryfylke archipelago including visits to the city of Stavanger, Norway – passing outside the windows of Norled’s main office. The vessel will be operating on a year-round basis in a 10-year contract with the local county.

Norled originally won the tender based on a conventional and existing ferry solution but also offered an option for a zero-emission alternative which the local county accepted due to the relatively moderate costs this newbuild solution could be offered for.