I think you're vastly overestimating the power output of solar cells.

Using 20% efficiency panels gives us 0.2KW/m^2/hr.

According to this Quora answer [1] a small container ship uses 15,000kW: for one 24 hour day that means it needs 360,000KWH in energy.

If we assume 10 hours a day of full sunlight then we need 180,000m^2 (equivalent to 18 hectares or 44.48 acres or 33.7 football fields) of solar panels.

This of course overly optimistic as it assumes no drag nor increase in power needed to haul these solar panels (and batteries for use overnight, etc.).

[1] https://www.quora.com/How-much-does-it-cost-to-fuel-a-cargo-...