PV Cruiser

[NWBeerkat]

I'm a newbie here. I found this website while trying to work out this problem.

I'm considering building a 20-24 foot electric drive boat for cruising at 4 knots with a top speed of at least 10 knots. For stabilities sake it would need a beam of 5 feet or more. I was thinking the general shape of a Cigarette boat with an aluminum hull (may consider fiberglass or kevlar).

If i could cover 80% of the top with photovoltaic panels would it be possible to reach a sustainable input/output? Bear in mind some of the panels would be build into a canopy, so there would be some wind drag. The latitude of Missouri is aproximately 35 degrees and I would only need to reach these limitations in July or August. There would be some night running so navigation light would be needed about 4 hours per day.

With these goals what size battery bank would I need to consider? I might find an opportunity for shore power now and then.

Any thoughts?

[magwas]

beware that I am not qualified to answer this question, so there might be error in the answer.
First I would do wome approximation on the power generated by the cells.
According to wikipedia, a 0.01 m2 12% efficiency cell would produce 1.2W in continental US in spring or autumn equinox if aimed directly to sun in a clear day. I would divide it at least with four to account for the surface being horizontal and not entirely clear day.
I would think a catamaran would be best both in terms of drag and stability.
A rough cat drawing just for approximations is attached. It have a 29 m2 deck, let's calculate with 20 m2: 1.2/0.01*20/4= 600W

Unfortunately I cannot get freeship to give an estimate of hull resistance at 4 and 10 knots.

[gonzo]

The main problem is that if the panels are flat on deck, they are not aimed to the sun. On a boat 6% efficiency would be more likely. Then with clouds it would be even less. Magwas makes a good point about a catamaran. Other options are overhanging panels, but they are impractical for docking, etc. Also, if you are considering night running, the panels should prodice excess power to charge batteries. Your design parameters would need about 15HP or so. That is about 11KW. At 12V that is 917 A. I don't think it is feasable

[NWBeerkat]

I appreciate the input. This project may be a year or two off. Today I was considering a cat design. However I also considered running the main controls electric with a small outboard as a backup. I really just want to make 5 mph most of the daylight hours with some drifting about 1/3 to 1/2 the time. In considering this project it seems this might be a good consideration for sailing if it weren't for the shadows. It may never come to fruition other than a modification to my bass tracker. If I could attach a electric somewhere on the outboard then the steering would be setup, just a little extra drag.

[CDK]

A top speed of 10 knots is not feasible for a 24 ft boat, you need almost twice that length.

Wikipedia gives data for a solar cell. For panels with frames and glass, calculate with 100 W/sq.m. , angle towards the sun between 0 and 15 degrees. Your 12 sq.m. will provide 1.2 kW between 10 am and 3 pm on cloudless days in midsummer, enough for a small Minn Kota outboard plus some charging current for your battery so you can get home when the clouds start spoiling your fun.