Originally Posted by Cottontop
The one factor omitted from your otherwise good assessment is the ability to refuel along the way with solar. We might see a doubling of solar panel efficiency in the next few years (an Aussie lab is already testing cells that have "layers" that absorb different frequencies and have reached 40%). We might get to four or five hours a day of 7 knot
cruising, and that's all lots of people do.
If you cover a 40' cat with the best solar panels
available commercially now (about 20% efficent) that works out to be about 40kwh a day of production. If you double it that gives you about 80kwh a day. A 40' cat operating at 7kn is going to need something like 20kw/hr. So your estimate that if we can somehow double the collection efficiency of pv panels
you could motor
for 4 hours is pretty spot on.
But it still isn't very practical.
First even assuming you get to 40% efficent panels
I wouldn't accept a 28nm range. It just isn't far enough.
Second that works out to a little better than 1nm/hour on average. Even in dead light air a heavily loaded cruising cat should be faster than that. So it will still be far faster to sacrafice panel space for sails
Third, the battery technology doesn't exist to store much of that generated power when you aren't moving. So you can't even fill the tanks
while at anchor
. Maybe you can store a few hours worth of run time with the best batteries theoretically possible, but it won't get much better.
Right now the most promising solution I see on the horizon to get rid of diesels would be the ability to crack ocean water
into hydrogen and oxygen. Compress the gas for storage, then use a fuel cell
to power the boat while underway. But I am not sure what round trip efficentcy would be, or how far out this technology really is.
For the forseable future this all works out to diesel power. Either diesel powered prime movers, or diesel powered generators.