Vision of the future? H2-powered vessel.

[Adelie]

Not necessarily a bigger boat, but definitely a different boat.

Power I presume, or would you consider a sailboat?

[Adelie]

Originally Posted by leecallen

I am looking at 39-40 foot power cats from FP, Lagoon, and Leopard. I think they share hull designs with their sailing yachts. In which case I am already getting those benefits.

My wife and I took sailing lessons a couple of years ago. The most important thing we learned is, she doesn't want to sail. She's not into the 'work', so it would be all me. Also we will probably spend a lot of time in the ICW where there is little wind.


That's what I am afraid of. I hope this discussion will clarify that.

Batteries, even the best Li-ion don't have the energy density for significant range at significant speed. Beyond that, where does the energy come from to charge the batteries?

The sun is the souce of most energy on this planet, but it falls fairly weakly. Insolation is about 1370W/sq-m. Solar panels are about 20% efficient these days. So a square meter of panels will yield about 275W under optimum conditions. Optimum conditions means no clouds or other shadows and the panel is tracking the sun. Most people don't set up their panels to track the sun, especially not on a boat, tracking mechanism is weak compared to fixing them in place. Usual arrangement is to lay them flat. If you are in or near the tropics the rule of thumb is that average daily production in W-hr is 4x nameplate capacity in Watts. So the for the above 275W panel, you can expect about 1,100 W-hr to put into your batteries most days. If it's cloudy you'll probably get 80-90% of that. Overcast, 1/2-2/3. Overcast and raining, about 1/4-1/3 of that. If you go into higher latitudes during the summer then daily output will be better, although the sun will never get as high, it will be in the sky a lot longer.

Once it's in the battery, you will get a bit less back out, for Lead acid batteries, about 87% will come back out, about 960W-hr. For LFP batteries the Round Trip Efficiency is 87-90% so slightly better, lets call it 950-1000W-hr.

That's just gilding the lily though, the big issue is putting enough solar panels on a boat. Unless you use a multihull and literally cover the top, you aren't going to go very far and even then it won't be very fast.

On a boat, at some point you have to double the power used to go 1kt faster. On the Cal 34 I want you need to double to power to go from 4kt (2kW) to 5kt (4kW). 6kt (6.7kW), 6.9kt (10kW). In waterborne craft, power required goes up really fast as speed increases.

PlanetSolar was a purpose built catamaran which went around the world on solar power alone. It was 15' long by 85' wide and cruised at 5kt.
https://www.planetsolar.swiss/en/world-premiere/boat/

There is a catamaran being produced by a company in Singapore that claims to be offshore capable. I wouldn't but I would go coastal in it. Most of the boat is roofed over and covered with panels. Boat can cruise at 4kt indefinitely. If you were willing to add wings off the sides, front and back for more solar panels and were willing to sacrifice the fitout and furnishings in the guest cabins the weight you saved could go into more batteries then I could see the boat making 5kt indefinitely in decent weather, or making a 6-7kt dash for 10-12hr by laying over the day before to top up the batteries. That would be enough to get from Miami to the Bahamas. The boat could do the Great loop.
https://www.azura-marine.com/aquanima-40

[StuM]

Originally Posted by Adelie

The sun is the souce of most energy on this planet, but it falls fairly weakly. Insolation is about 1370W/sq-m. Solar panels are about 20% efficient these days. So a square meter of panels will yield about 275W under optimum conditions.

It's about 1370 W/m² t the top of the atmosphere (TOA).
It's only about 1000W/M² at sea level when the sun is directly overhead with a clear sky.


So you 275W is very ambitious. More like 200W
(Oh, and it's Wh, not W-hr )


> It was 15' long by 85' wide and cruised at 5kt.
I think you meant 115' long by 85' wide

[Adelie]

Stu’s right about both insolation and PlanetSolar’s dimensions.