Preempting the "why not hydrogen" comments:<p>Always a good time to refer to "The Hydrogen Ladder" (version 5.0 nowadays):<p><a href="https://www.linkedin.com/pulse/hydrogen-ladder-version-50-michael-liebreich" rel="nofollow">https://www.linkedin.com/pulse/hydrogen-ladder-version-50-mi...</a><p>In this case, the alternative of using hydrogen for the "Local Ferries" use case would be in class F (almost uncompetitive) and the recommended alternative is indeed electric powertrains.
Cool. The Copenhagen Harbour "Bus" (ferries) are electric and they are super pleasant to ride. No fumes, almost no noise, no spilled oils or fuels. <a href="https://en.wikipedia.org/wiki/Copenhagen_Harbour_Buses" rel="nofollow">https://en.wikipedia.org/wiki/Copenhagen_Harbour_Buses</a>
There's an electric ferry service between Iceland and Vestmannaeyjar - it's very nice. Quiet and doesn't smell of ship diesel.<p>The charging port and plug are quite something, too.
If it stays docked on one side at night hooked to the grid and offering grid stabilization services and charges on the other, could it be a net energy importer?<p>Asking for a friend... :)
There is an electric water metro service in Cochin, Kerala, India. It was built in partnership with the German government.<p><a href="https://en.m.wikipedia.org/wiki/Kochi_Water_Metro" rel="nofollow">https://en.m.wikipedia.org/wiki/Kochi_Water_Metro</a>
I wonder how well a flywheel would work in this type of application. Journeys are short, presumably the flywheel can charge up faster then a normal battery. Maybe it's just too dangerous to put on a boat with passengers.