How much horse power aka Megawatts does a ship that size need to operate? Not only the engines need the power but also all the electrical and electronic used by the crew and passengers. What plans do they have when the ship hits a Lollapalooza of a storm and they can’t get out of the was in time?
I can't imagine enough surface area on the ship to account for enough solar coming in to much, even if they're in at a latitude that averages 6 peak solar hours per day.
The QE2 (retired from service) has total generation capacity of 95 MW.
The more modern Queen Mary 2 has a total on-board generation capacity of around 120 MW (megawatts).
It takes around ten acres of land space to generate one megawatt of electricity on land. An acre is 43560 square feet.
The best currently-available photovoltaic cells generate about 20 watts per square foot under optimal conditions. That’s 50000 square feet per megawatt, if you could get 100% area coverage. Of course, you don’t often have “optimal conditions” anywhere, including at sea. Figure you have to quadruple that figure to be realistic as an average. That’s more than four acres of 100% PV cell area per megawatt. Now multiply that by about 75 to get a realistic figure for a large cruise ship. We’re talking close to 400 acres; a square mile is 640 acres.
That’s all assuming 100% coverage, which you won’t get. Land-based PV generation is lucky to get one third of that. So you’ve got to at least double that 400 acre estimate to account for the space between solar panels.
Now compare that area to the area of the deck of a cruise ship.