When ships moved from muscle- and wind power to burning coal and other fossil fuels for their propulsion, they also became significantly faster and larger. Today’s cargo ships and ferries have become the backbone of modern civilization, along with a range of boat types. Even though tugs and smaller pleasure vessels are a far cry from a multi-thousand ton cargo or cruise ship, one would be hard-pressed to convert these boats back to a pure muscle or wind-based version. In short, we won’t be going back to the Age of Sail, but at the same time the fossil fuel-burning engines in these boats and ship come with their own range of issues.
Even if factors like pollution and carbon emissions are not something which keep you up at night, fuel costs just might, with these and efficiency regulations increasing year over year. Taking a page from alternative propulsions with cars and trucks, the maritime industry has been considering a range of replacements for diesel and steam engines. Here battery-electric propulsion is somewhat of an odd duck, as it does not carry its own fuel and instead requires on-shore recharging stations. Yet if battery-electric vehicles (BEVs) can be made to work on land with accompanying low ‘refueling’ costs, why not ships and boats?
A recent study by Lawrence Berkeley National Laboratory (LBNL) researchers Hee Seung Moon et al. as published in Nature Energy claims that a significant part of US maritime traffic can be electrified this way. Yet as a theoretical model, how close does it hit to the harsh realities imposed by this physical world which we live in?
Different Scales
An important aspect with any battery-powered craft is matching the battery capacity with the expected range. For BEVs like cars, the goal is to put as much battery capacity into the vehicle as possible, constrained mostly by factors such as the cost per kWh and how much physical volume is available in the vehicle for batteries without intruding on the driver and passengers. This is how we ended up with a range of BEVs that can cover a sizeable chunk of daily usage cases, as well as specific cases like buses where the daily range requirement is planned in advance and thus very easy to optimize for. Even so, a number of road-bound vehicles are hard to electrify with just batteries, such as cross-country trucks due to the sheer weight of the batteries required in most scenarios. Unlike a fuel tank, these batteries also do not lose weight as they become more empty.
In the case of boats, these smaller vessels tend to have pretty limited range. For example: tugs put in a lot of work, but either remain bound to a specific harbor or slowly follow a set watercourse like a river with a gaggle of barges in tow. Here you can have recharging infrastructure set up and charging points ready to go with relatively little difficulty in the harbor or at mooring spots along the route. More challenging are vessels with more erratic routes, not to mention ships with routes that are so long that no reasonable amount of batteries could power it without recharging or swapping batteries. The main case in point here is container ships.
In a 2022 study by Jessica Kersey et al. in Nature Energy it was found that for routes of less than 1,500 km electrification would be economical, assuming a battery price of $100 per kWh. At that point the main question remains how many batteries you can fit into the ship without negatively impacting the cargo load that it can carry. A container ship can travel around 540 km per day at its average cruising speed, with a shipping route like Los Angeles to Yokohama of 7,792 km (4,207.6 nautical miles) taking over two weeks:
Putting enough batteries on cargo ships to allow them to travel these routes without recharging in between is too much to ask. This is why the focus with battery-electric propulsion for ships and boats is on these shorter routes, where the total volume of batteries combined with electric motor(s) does not significantly exceed the volume (and weight) previously taken up by the diesel engine(s) and fuel tanks. As modelled by Kersey et al., for a small neo-Panamax container ship this would be the case if the route is kept below 3,000 km. Yet if the route is extended to something like 20,000 km the batteries would take up 32% of the containership’s carrying capacity.
Using batteries with higher energy density could help here, but as seen with today’s favorite battery chemistries using the higher density Li-ion comes with fewer charge cycles and worse stability, while LiFePO4 with its common use in especially BEVs and grid-storage and solar-storage batteries has much better longevity and safety record, at the cost of more weight per kWh.
Removable Batteries
Currently a number of battery-electric boats and ships are in service, with ferries being one of the first to be outfitted with such propulsion, case in point being the Norwegian Bastø Electric ferry. This 600 passenger and 200 car ferry uses its 4.3 MWh battery as well as a diesel generator to travel the 10 kilometer route between Moss and Horten. While docked the batteries are charged up when a charging point is available. This makes it not a pure battery-electric boat, but rather a hybrid.
More interesting are the two battery-electric containerships owned by China’s COSCO Shipping which recently began carrying shipping containers along the approximately 500 km route between Nanjing and Shanghai’s Yangshan Port. The Lu Shui (Green Water) 1 and 2 vessels are 700 TEU container ships that can travel at 10.4 knots over the Yangtze river. Perhaps most interesting about them is that they don’t have a battery bank integrated into their hulls, but rather take swappable batteries, with a standard capacity of 57.6 MWh, but with optional connection points for additional battery packs.
In the aforementioned LBNL study by Hee Seung Moon et al. the assumption was made that existing vessels would be retrofitted with batteries and electric motors, which would place a range of restrictions relative to newly designed and built vessels like COSCO’s newly commissioned ones. Being able to swap out battery packs along with shipping containers allows freshly charged packs to be ready when the containership docks and avoids the hassles of quick charging after each trip and replacing batteries after their approximately decade-long useful lifespan, for LiFePO4.
Practical Within Limits
It’s clear that for shorter routes the use of battery-electric propulsion can make sense. Depending on the local grid this can also be less polluting than burning low-sulfur diesel fuel, and conceivably be cheaper, though it all has to be worked out on a case-by-case basis. In the case of COSCO the reasoning appears to have been that these custom container ships are perfect for such a shorter route, with cost savings to be expected over the use of direct-driven diesel or diesel-electric propulsion. Ultimately the success of battery-electric propulsion will come down to simple economics, especially in the cut-throat shipping business.
Featured image & thumbnail: Containership MSC Texas. (Source: Wikimedia Commons)
“BATTERY-ELECTRIC SHIPS: COMING SOON TO A HARBOR NEAR YOU?”
Nope, because there isn’t a harbor near me!
B^)
Well that just means you need a dredge. These have always been electric – a significant and slightly mysterious part of the Electrical Safety Regulations is primarily about dredges.
https://www.nzherald.co.nz/business/markets/commodities/historic-gold-dredge-up-for-sale/JH4LT2H64A2ZQEPBMBFMHWRCPE/?c_id=3&objectid=11578080
500km isn’t much for shipping. A good start though. Maybe it’s coming to my harbor, but it won’t be traveling far from it for a while
Electric shipping was quit common, especially along canals, in two main forms:
– Electric trolley wires above or along the canal, on which electric-powered ships (mainly tugs towing the actual cargo-carrying ships) would sail. Sometimes they would be propellor-powered, sometimes pulled themselves along a chain at the bottom of the canal. Working examples are the https://en.m.wikipedia.org/wiki/Riqueval_Tunnel and the https://en.m.wikipedia.org/wiki/Straussee_Ferry (I sailed on a ship through the first one, it is a really amazing experience)
– Electric tractors (road or rail bound) along the towpath, would get their power from a trollwy wire and would tow ships. Arpund the 1930’s the entire Northern French and Belgian canal system had these alomg the banks, but these have fallen out of flavour. The only working example that I know are the Panama Canal locks.
More info: https://solar.lowtechmagazine.com/2009/12/trolley-canal-boats
This isn’t green, it’s coal ships with extra steps. And every step is very very dirty. From the rare earth ores mined with environment destroying processes performed by slave labor, to the coal power plants supplying the actual electricity. Onboard nuclear power is the obvious solution and an already solved engineering problem. The only thing to figure out is how to get governments to allow it.
I don’t think a nuclear cargo ship is a good idea, even though functionally it would be good – all that radioactive material on a slow easy target vessel is just asking for the pirates to get in on the action, maybe sell the fuel for use in a dirty bomb etc. Nuclear power that is much much easier to protect and regulate has enough trouble getting built without making that sort of nonsense possible.
Also to single out the rare earth ores is massively disingenuous – the iron ores that make up 99% of the ships mass are plenty destructive, the slag piles (etc) of old mines can remain a problem for decades without cleanup and then you have to turn it into steel, and that needs lots of carbon from somewhere, so yet more coal (probably). As is assuming this is just coal power with extra steps, which in many parts of the world it wouldn’t be as coal is either entirely dead as a power source or phasing out and even in places that are heavily coal dependent like China they also have been investing in large solar array etc, which might only account for a small fraction of the electric consumption each year, but would mean your ‘coal powered’ electric boat is only partially coal powered.
I learned to stop worrying and love the bomb, and even I think that nuclear cargo ships are a very bad idea!
I’m also for nuclear cargo ships. Though I think it’d have to be managed by navy nuclear engineers and keep a small troop presence on board as guards.
Electric-battery ships do not inherently require the use of slave labor for the battery components or the use of fossil fuel energy to recharge them.
In other words, you can solve those problems without saying “no” to battery-electric ships.
Electric vehicles powered by oil-fired electricity emit about half the CO2 well-to-wheel compared to petrol cars. It’s even better with coal, and of.coirse electricity can be 100% renewable, while combustion fuels at this moment realistically are 90-100% fossil energy.
Yes, but that is just a consequence of economics.
These ships run on “bunker fuel” which is essentially a waste product of petroleum refining. That is why it is so polluting, but also why it is cheap.
Stopping the use of this fuel would be a great thing, but also cause problems, because we have to get rid of it. Maybe pump it back into dry oil wells? Can we even do that without “losing” a lot into the environment?
Everything is interconnected.
You can’t simply “solve” a problem like this.
There are thousands of moving parts, and each one needs to be accounted for to make real progress.
It’s weird how people assume that electric power must always come from coal. The US only gets 16% of its electrical generation from coal, and that number is only going to get smaller.
China still burns a lot of coal, but they also have 12 nuke plants under construction right now.
Hopefully their electrics will be better than the ship that took out a bridge.
You heard it may have been retaliation by the Russians for USA involvement in Ukraine?
That would explain why the USA gov’t is paying to replace the bridge instead of the ship’s insurer.
Battery electric ships are not viable for shipping. An ocean going ship with a range of 500km isn’t even considered safe.
Well yeah, it would leave you stranded in the ocean
Fortinately, not all ships are ocean going. In The Netherlands there is an electric container ship (“Alphenaar”) that does a 124-km round trip daily, between a beer brewery and a distribution center. It has 3 shipping containers for battery, that can quickly be changed out by existing container infrastructure and charged on shore.
Navies have used battery powered submarines for a very long time.
Actually they have used hybrid subs .
The case is not in your point. :(
Sails seem to be a more ecologically friendly option. Literal wind power is better when it comes to ships and keep the batteries in reserve for maneuvering in shallow waters.
This always feels like a cop-out.
If there are going to be emission regulations, the MUST be applied all the way up the stack.
“Look at our green ships. We have no emissions. Nevermind those coal power plants. We just HAPPENED to charge our fleet of ships here because it was close.”