A barge in England does move very slowly 90% of the time. They also have lots of room for solar. There are several u tubers chronicling their journey down this road and they seem to be doing well. There is even a start up advertising that they are building new boats trying to make a go of it.
From: "James Lambden james@electroprop.com [electricboats]" <electricboats@yahoogroups.com>
Subject: Re: [Electric Boats] Re: Quite the potential project.. but is it feasible?
Electric propulsion has many advantages for sailboats. Firstly, the electric motor is the auxiliary. It is meant to get the boat in and out of the harbor. As a motor sailor, an electric sailboat has better range than a diesel when equipped with an appropriate battery pack. There's hundreds of other reasons why electric propulsion makes more sense on a small sailboat than a diesel does.
But as the primary for a motor boat, it doesn't make so much sense. Done properly with all the safety equipment, a hybrid is much more expensive than a traditional diesel engine. This is because you now have 4 systems replacing one system. The diesel engine (one system) is replaced by a diesel engine, a generator head, a battery pack and a propulsion motor.
In a motor boat setup where high continuous power is required, it doesn't make any sense. Under battery power, the batteries would last 20 minutes to an hour at most and the generators would have to run all the time.
There is no advantage to electric unless the motor boat is running at very low speeds most of the time.
A properly setup diesel will be more efficient than a hybrid. This is because mechanical energy goes straight to the propeller. ( in a hybrid, mechanical energy is transferred to electric then back again to mechanical and those losses can be as much as 40% )
A diesel will likely be more reliable too, as there is only one system and not 4 systems.
Diesels can benefit from higher gear ratios and higher propeller pitch as well. Diesels have not been optimized and this is where you would be best to focus your energies. Propeller placement remains a mystery to most designers when really it is very simple….either give the propeller adequate hull clearance or put a Kurt Nozzle around it for a 25% increase in propulsion efficiency.
Motor boats could benefit from having a large primary diesel for all the high output power, and a smaller electric for maneuvering and slow speed operation - basically a parallel hybrid.
Motor boats are just that…..MOTOR BOATS…. and require a motor.
Going down this road and finding out that electric propulsion does not work is both very expensive for the experimenter, but also hard on our fledgling electric propulsion industry, as any failure will undoubtedly draw more press than any success.
I would love to see every boat convert to electric but only if it is practical and proper for the application. In this case, a barge, I don't think this is one of those applications.
James Lambden
The Electric Propeller Company
625C East Haley Street,
Santa Barbara, CA
93103
805 455 8444
james@electroprop.com
www.electroprop.com 
