Full electric vessels get all their power from batteries – for propulsion as well as auxiliaries. Battery power onboard and charging infrastructure onshore enable zero carbon operations. This makes electric, battery powered ships an interesting concept – after all, decarbonisation is high on the agenda of governments and regulatory bodies. Electric ships will become more common and the capabilities are increasing fast.
The efficiency of an electric propulsion system can be as much as 90% due to the low loss from the system and is being adopted by many vessel types.
Full electric vessels operate without an internal combustion engine. Batteries provide the power for the ship.
In contrast, a hybrid ship resembles a plug-in hybrid car in that it will charge its battery using shore power, and it also has a conventional engine onboard.
Because batteries are heavy, a fully electric drive is practical for vessels that sail shorter distances. For vessels that sail longer distances, a hybrid solution is more suitable.
Ferries, tugs, and inland waterway vessels can easily benefit from full electric propulsion. Already, some inland vessels such as ferries and pleasure boats sail using nothing but electricity. This is because they sail shorter distances and can therefore operate on smaller batteries, which weigh less and are faster to re-charge.
As a technology leader in vessel electrification, Wärtsilä is investing in and developing solutions to support this important and growing segment of marine vessels. Here are three vessel types that are likely to take advantage of the latest developments.
Ferries are part of the local infrastructure and day-to-day life of local communities. As a rule, they will dock at certain locations at regular intervals. Full electric propulsion is a valid solution for them for short distances.
Although the onboard electric propulsion system may be simple, the onshore charging infrastructure is not. A ferry may have a short turnaround time, meaning that it will have a limited time to re-charge its battery.
If the local grid is weak, there has to be an energy storage system onshore for buffering electricity – to allow faster charging at higher power levels.
Tugs are critical to the safe entry and docking of many vessels in ports. They have a clear operating pattern: transit to a vessel – light assist most of the time – heavy assist when needed – transit back to the docking area. They also have enough time at dock for charging the batteries.
This is an ideal operating profile for full electric operation. The tug spends only around 3-4 hours at sea at a time, and only needs short bursts of high power when in heavy assist mode.
Inland waterway vessels also have the advantage of regular docking, but their operating pattern is different from that of ferries or tugs. Instead of sailing a few hours at a time, inland waterway vessels run 24/7 until they reach their destination. The destinations vary according to their cargo and schedule.
Swappable energy storage systems (containerised battery packs) are an ideal solution for inland waterway vessels. The swappable battery containers are stored and re-charged in locations along the waterway. The vessel can swap its battery when needed, or at the same time that it stops to load or unload cargo.
Watch this video to learn more about a mobile battery container solution for inland waterway vessels.
Several boat builders are planning hybrid cruise ships. But for large cargo ships that sail the world’s oceans, electric drives are still a long way away. The batteries are still not efficient enough and are too heavy for ships that sail long distances on the high seas.
