Independently of the speed of the ships, the cost of the crews would probably kill the idea, except for goods with a very high margin, but there must a fuel price (including carbon tax) where this should become economically viable again.
The sails don't look like historic sails - they are often rotors that look like cylinders.
Maersk's Pelican, for example, is supposed to get 10% from its rotor sails.
Tangent: why do wind turbines look so conventional, with their propellers? There is a lot online about vertical axis wind turbines etc, but I've never seen one.
I guess they're still not feasible for some reason.
> research at Caltech has also shown that a carefully designed wind farm using VAWTs can have an output power ten times that of a HAWT wind farm of the same size
etc
The cups on the normal wind speed sensor have less drag into the wind.
It would be easy to imagine a VAWT where a computer knew the wind direction and feathered the blades on the back sweep etc?
Not sure if they still exist but east of SF on 580 (Altamonte pass?) I think there are still some.
COLREGs probably prevent unmanned ships, but regulations can evolve if you can convince that there is an actual safety improvement (the ships could be coupled with satellites and flying drones to increase visibility/radar/tracking awareness).
This is not even taking into consideration the power requirements of chilled containers.
I'm all for making ships more efficient using wind, every percent is a win but the shipping industry is never going back to it as the main propulsion method.
The electric side is really interesting, it is viable in some cases today. I've done some napkin math about outfitting a traditional sailing ship I volunteer on with batteries from Corvus mentioned in another comment and it's completely viable today. Unless going for huge system needing a complete overhaul of the inside layout we would still need a generator for range above about 5-6 hours but that could run on carbon neutral HVO diesel.
I imagine this could work pretty well, maybe even with headwind (?), owning to the different densities (and inertia) of water and air, as well as their relative velocities. Yet everyone I've told this to called me nuts, likening this to perpetual motion, etc.
I'd likely go with hydrogen storage for boats, especially if the system is reversible (though I've read it can be quite difficult to filter input water).
They are making trials with wind "turbines" using the magnus effect[1], they seem to save about 300 tons of fuel per year, but since the article doesn't include the ships yearly total amount it is hard to put it into a relation to anything. https://safety4sea.com/tests-from-rotor-sail-technology-on-v...
I think ships is one of the applications where hydrogren could be feasable. Batteries are hard when you have to have the range from China to Europe or NA without stops and the density of hydrogen could maybe solve that. Especially since compared to cars the distribution network is more easily centered around large harbours and routes which is already used to handling dangerous goods. Though the competition is going to be synthetic hydrocarbons and all they need are producers, the entire world is already devoted to transporting them.
[0] https://en.wikipedia.org/wiki/Wind_turbine [1] https://en.wikipedia.org/wiki/Magnus_effect
The challenge with a hybrid wind turbine-electric propulsion would be the energy efficiency losses from turbine generator through a power conversion (and probably storage) device and ultimately the propulsion motor. By the time you're finished, it probably would have been more practical to use some type of sail to harvest wind energy for propulsion directly with no losses. For a head wind, your wind turbine would be harvesting energy, but it would also be creating significant air drag which would be added to the total resistance of the vessel, so the sum total of propulsive power would be negative in a direct head wind scenario. Interstingly, the opposite is true for a tail wind - that is you'll be gaining thrust (like a sail) in addition to harvesting some of that energy. Again, though, because of the energy conversion losses, I think you'd probably get better propulsive efficiency if you just used a sail, which has no energy transmission losses.
I think the best case for wind turbines on ships is to use them for energy harvesting in port and in tail winds. I'm sure someone is doing this, but you need to balance the initial hardware investment and operational maintenance costs against the potential fuel savings in order to justify the installation.
There are a large quantity of energy harvesting/conserving technologies out there that are trying to take profit the IMO restrictions (which is a very good thing I think). The interesting thing is that global shipping is only a few percent (used to be 2%) of the worlds transportation carbon emissions, but it transports the most tonnage of any mode of transport. My point is that, while all of this focus on the shipping industry is necessary and very interesting to me personally, things like converting automobiles or airliner emission is much more of an environmental impact.
With a big enough fleet you could statistically deal with delays. Eg, in the same sense that airlines slightly overbook flights. The variability/risk in the port costs would cut into the fuel savings; hard to imagine that would be a show stopper. There must be a portion of the industry that is less time sensitive and would entertain working out the details to facilitate the slower speeds for slower costs approach.
Slower shipping may not be a problem, but unpredictability often is. Few businesses can handle completely unpredictable shipping timelines.