Actually the idea of using integrated energy (solar, wind, wave) systems (IES) for shipping has been around for quite some time. However, it makes no real sense to employ this design for cruise ships - an industry based entirely on shrinking discretionary incomes. The real payoff comes for specialized freighters that can deliver critical refrigerated and frozen perishables - which now are primarily supplied by air freight - no longer and not likely in the near future to ever be cost effective again .

What about helium filled derigibles ?