World's first car-carrying electric ferry to see use in Norway
Presently, the Norwegian villages of Lavik and Oppedal are linked by a ferry that burns about a million liters (264,172 US gallons) of diesel a year, emitting 570 tonnes (628 tons) of carbon dioxide and 15 tonnes (16.5 tons) of nitrogen oxides. That’s about to change, however, as it’s slated to be replaced by what is claimed to be the world’s first all-electric car-carrying ferry. Developed by Siemens and Norwegian shipyard Fjellstrand, the vessel can recharge its batteries in just ten minutes.
The 80-meter (262.5-foot) catamaran can carry 120 cars and 360 passengers across the fjord between the villages. It is powered by two 10-tonne (11-ton) electric motors, each one driving a separate propeller. Those motors have a combined maximum output of 800 kilowatts, although for the ferry’s usual cruising speed of 10 knots, an output of 400 kW should suffice.
By contrast, the diesel ferry currently in use on that route puts out 1,500 kW. Part of the reason that the electric ferry needs less oomph lies in its streamlined twin-hull design, and the fact that it weighs about half as much as an equivalent-sized conventional vessel. Those weight-savings are largely due to the use of aluminum in its hull construction, as opposed to the more traditional steel.
As noted earlier, it will be able to recharge its batteries in only ten minutes, when docked at either of the villages – it’s not clear if that figure is for recharging from an almost empty state, or simply topping up. In any case, the electrical grids of both communities won’t be able to handle such a demand all at once. Therefore, the ferry will draw upon batteries installed at each port, which will themselves be recharged slowly from the local grid.
Shipping company Norled, which initiated the electric ferry project, entered the vessel in a contest put on by Norway's Ministry of Transport. As the winner of the competition, the company has been granted a license to operate the ferry on the route from 2015 to 2025.
It has been suggested that all other Norwegian crossings of less than 30 minutes in length could also be served by electric ferries.
Please keep comments to less than 150 words. No abusive material or spam will be published.
However why do they need 10 tonne motors for 400kW.
Possibly they should have stated the torque of the motors, as it is actually more relevant.
The 1500kW diesel motor is most likely turning at a higher rate than the stated electric motors, which are likely mated to directly to the propeller without a gearbox. The propeller may only be turning at 100-400 rpm, while a deisel engine may be rotating at 1500 RPM or greater.
As Power = Torque*Angular velocity (radians per second)
It is common for electric motors replacing internal combustion engines to be lower in power rating, as they develop a lot more torque at lower revs. Also add a more streamlined Hull, and the power reduction is not surprising....
I had a look on the map, and the distance of this ferry service (it is a regular ferry service) is only 5km. They could fairly easily avoid having to carry a large battery bank on board by using a reel in- reel out power cable carrying mains power from the shore to the boat... (If there is a mid section where the cable can be anchored to the seabed, they would only need stowage space for 3km of cable at the most.... This system is used in shuttle cars in underground mining operations... maybe this is thinking too far outside the box... Also, it is possible that the installation of the cable would exceed the cost of a batterypack with no guarantee that its life would be any greater....
One positive thing about having a trailing cable is that once it leaves the vessel, it will descend to the bottom fairly quickly as it will have a reasonably low tension on it as it is not a pull-cable.
Of course there may need to be a battery on board as well in case the power supply from shore fails.... (or the cable is cot for some reason...)
Sorry for thinking out loud.
Granted it is unlikely that both electric grids will go down at the same time but how long will the ferry be able to keep functioning if they do? Can it stay in service if just one side looses power? How long can it stay under power if a storm make docking impossible?
Storms are not fully predictable. The Captain would believe that he would be able to make the trip safely but the storm gets worse faster than he anticipated. It has happened before and the captain was praised for his seamanship for taking the ferry out to sea and keeping her afloat for days. A tornado could destroy the docking facility as well.
Lots of tiny batteries.