Will you go for solar (photovoltaic cells) on boat?

[marshmat]

The comparison I made to conventional methods was with regards to large-scale generation, such as for a land-based facility or large ship. I certainly wouldn't want a nuclear plant on my yacht!

Re: High-power-density lithium batteries. These do exist, and the ultra-rapid-charge variety are indeed being developed quite rapidly. They ARE scalable to high capacities if you combine enough series/parallel strings. There are two main difficulties though: safety and cost.
From a safety aspect, Li-polymer cells suck. They need constant monitoring for overvoltage, overcurrent, undervoltage, temperature, etc. on a cell level. For a 60 V pack, this means typically about 16 individual protection systems, each capable of responding to a problem by cutting off the battery in a fraction of a second. If this monitoring isn't done, the cells do NOT self-balance like lead- and nickel-based cells do, and so an undervoltage condition can actually short out one or more cells, releasing hydrogen fluoride gas into the compartment. These cells are not for the home builder; packs based on lithium cells MUST be professionally designed and built.
From a cost standpoint they're not great either. At up to $30,000 for a fully protected 5 kW pack like those of high-speed solar cars, lithium polymer is not a feasible option for the budget-conscious. Granted, though, such a pack weighs only 30 kg, less than half of what a nickel-based one would be and only a tiny fraction of the weight of a lead pack. And with three 3W fans venting such a pack, which measures only about 20x50x60 cm, it's possible to draw 80 A at 120 V without trouble.

So as far as solar on boats goes, my pick would probably be lead (for slower boats) or NiMH (for faster boats like a wavepiercer cat) cells, mounted low in the bilge in properly vented enclosures. The difficulty is that it's virtually impossible to licence NiMH technology over 12 kWh as the company that owns the patent is remarkably messed-up about suppressing the use of their own technology.