True.  There are a great many diesel-electric drives out there (mining trucks).  I&#x27;m more concerned with the energy density.  The batteries needed to power a container ship crossing an ocean would be monumental.<p>Ships are very very fuel efficient, by far the most efficient means of moving goods over distance.  But they are also a large percentage of oil consumers (20% ?).  So even though they are very efficient, they need to be addressed and their emissions somehow reduced.