This article goes through the economics, and why iron-air batteries in particular would be the best choice.
A problem for ships with marine diesel engines is that engine efficiency drops precipitously at lower RPMs, resulting in diminishing returns for slow steaming. Electric motors don't share this issue, so they get the full benefits of slower travel. An electric ship will use ~1/8th of the power and ~1/4th of the energy to complete a trip if it halves its speed.
This article goes through the economics, and why iron-air batteries in particular would be the best choice.
This article goes through the economics, and why iron-air batteries in particular would be the best choice.