There could be could add battery storage to be used during the journey. They could include wind turbines to add further power generation.
Also ships can go slower. In my limited knowledge of boats every extra knot takes significantly extra fuel. If we were bringing multiple power sources 'slow' cargo may be viable. And the has to be other ways to increase this function.
And there is always hybrid. Not all power has to be renewable sources. A solution could start with supplementing diesel driven thrust with some lower cost green power. Given diesel is 70% of shipping operating cost that seems a potential option.
I think the number one obstacle to this is it would be nowhere near viable from the costs perspective.
No one really wants to build cargo ships right now, shipping companies are barely staying afloat right now because there is a glut of cargo capacity.
This technology would need to be cheap enough that it would make sense to retrofit a ship with it... which would probably not be the case for a very long time.
I do think it's a very thought provoking idea however.
I'm under the impression that both are true. There is overcapacity in the shipping market, which drives down prices. Because prices are low, shippers are investing in ever larger (more efficient) vessels, in order to turn a profit. This in turn leads to more overcapacity, which leads to a drive for even larger and more efficient ships.
It's a type of 'tragedy of commons' situation, where every shipping company is making the right decisions from their individual perspective, but collectively they're driving themselves into the ground.
For me this explains the rise of slow-steaming. It makes a lot of sense in this market because it lowers the cost of shipping a container (less fuel), while simultaneously reducing the market capacity (# of containers / year).
Finally, very few shipping companies make money on the major lines (e.g. China to Europe), because it's pure price competition. They're much more likely to make money in places where they have a 'monopoly' on something: e.g. being the only ship that leaves in the next 3 days, or being the only shipper going to a specific location. For example inter-Africa shipping falls in this category.
An additional detail is also the expansion of the panama canal which allowed more and larger ships to travel through it cutting down the travel time for larger cargo ships eliminating a primary advantage of smaller vessels.
Norsepower provides modern sails: "a spinning cylinder that uses the Magnus effect to harness wind power to propel a ship."
"When the wind conditions are favourable, Norsepower Rotor Sails allow the main engines to be throttled back, saving fuel and reducing emissions while providing the power needed to maintain speed and voyage time. Rotor sails can be used with new vessels or they can be retrofitted to existing ships."
I love that you posted an 'in the wild' solution. So many people saying this is not possible. And then someone has found a creative way to offer one alternate. Such a good example of dont listen to the nay-sayers if you want to mentally explore something. There are almost always solutions and I'm sure there are more for this one.
No one said it wasn't possible. Clearly, it's possible since ships were wind powered for millenia. The problem is that with very low fuel costs, it's not feasible because the drawbacks outweigh the benefits.
Sure sails will be used for some limited applications. But Magnus effect cylinders won't be practical for the majority of cargo ships because they consume valuable deck space and interfere with loading operations. They would only make sense if hydrocarbon fuel becomes much more expensive.
Unfortunately the energy density of batteries is really bad (in the bigger picture) and, besides, we're supposed to be using weight for cargo. Tankers also burn very nasty fuels that can't be used for anything else - so in practice they're very efficient.
There have been cracks at putting "sails" of one form or another on ships but they've always been heavy, relatively ineffective and basically just not worth the hassle.
The speed of a ship is actually quite easy to work out. You find the time/value curve for the cargo and the cost/time for the ship and see where they cross - essentially. The long and short of it is that the lighter and more valuable your cargo is, the faster the ship goes. This is why container ships are much faster than oil tankers.
The human crew isn't much of a factor in cargo ship speed. Ship owners would be happy to leave their crews out at sea a week longer if it was profitable.
Drone ships won't be practical any time soon because of maintenance problems. Crews spend much of their time at sea performing preventative maintenance, painting, and fixing broken equipment. With a drone ship all of that work would have to be done at the pier which would be far more expensive than paying a crew.
They are already slow steaming on many routes. Ship owners aren't idiots; they have software to perform constrained optimization calculations to figure out the steaming speed which will maximize profit on each leg. This is based on fuel price, crew wages, asset depreciation, delivery contracts, etc.
I wonder if they could use an underwater wing design, similar to this (https://www.youtube.com/watch?v=u5SHn0SdXjw). You keep swapping the angle of the wing so it's always pushing forward whether the vessel is moving up or down, but it would be powered by the waves moving the ship. It might be possible to get a slow base load speed for 'free' with a large enough wings
There could be could add battery storage to be used during the journey. They could include wind turbines to add further power generation.
Also ships can go slower. In my limited knowledge of boats every extra knot takes significantly extra fuel. If we were bringing multiple power sources 'slow' cargo may be viable. And the has to be other ways to increase this function.
And there is always hybrid. Not all power has to be renewable sources. A solution could start with supplementing diesel driven thrust with some lower cost green power. Given diesel is 70% of shipping operating cost that seems a potential option.