If sails are so good (and they are) then build sailing ships again. Conventional design ships.

Trouble is, you need experienced sailors to handle them and we worked to get rid of them a while ago.

Of course it won’t be emissions-free. Vast quantities of fossil fuels will be required for mining the iron ore and smelting the steel for the vessel’s hull. Even more for making its steel & composite sails.

While I have not seen figures for ships, about half the total lifetime energy use of the cars this ship will carry happens during the original manufacturing — and much of that has to be fossil fuel.

As usual with the Renewable Energy Scam, notice that capital costs of the drive system are greatly increased. The shipowner has to buy a conventional diesel engine as well as those expensive sails — and will have to run diesel generators to provide the electric or hydraulic power needed to rotate & control those sails. When the cost of capital returns to normal levels (Euro negative interest rates are unsustainable), this kind of ship will only be able to sail slowly to the breakers yard.