[walrus01]

Your math is far off. If you put 60kW (STC rating) of PV panels as quantity 100 of 600W premium panels on top, in Uruguay, it'll produce somewhere between 6800 to 8100 kWh per month if the panels are perfectly exposed to sun from sunrise to sunset.

If we say it's 7500kWh a month that's something like 250 kWh of production per day, which is a tiny drop in the bucket compared to the amount of energy needed to charge the ferry.