My father just put in a large grid tied solar panel array and it has inspired me to harness some of the sun for my self. I looked at adding a grid tie solar array to my house but my energy consumption is so much lower than his house that my pay off period would be a long time. I would rather continue to work towards an off grid solar system. I decided to move my attention to a solar powered party boat. Everyone I talk to in the marine world say it can not be done with out a solar array the size of the entire boat and a battery bank that would sink the boat. I disagree. Lets look at this as just an off grid set up for say a cabin in the woods. I will have a dc motor that at half throttle, the normal cruising speed it will be operated at, draws 8.4 amps at 12 volts. It will be operated 5 hours a day on Saturday and Sunday mostly (2 days a week). A stereo will draw 2.5 amps at 12 volts for 5 hours as well. So the system will draw 10.9 amps for 5 hours meaning I will need 54.9 ah on board each day. Suppose I get confused and try to go out on a bad weekend where there is no sun. I will need 109 ah and a really stiff drink. I know we do not discharge a battery below 50% to save its life. So I would need a deep cycle battery with approximately a 220 ah rating. These can be had for about $500 and only weigh 100 lbs and it is one battery. Expensive but manageable. Then I would need to replace 54.9 amps in a day. I live in the great northeast so lets say 6 hours of sunlight. It will only be used only in the summer so it will have peak sun time for our area which is about 6 hours. A 10 amp charger should replenish the depleted battery in one day. 1 140 watt panel connected to a 10 amp charger for off grid cabins can be had for about $400. This all seems to work out with my math. One solar panel, one large but not sink a boat battery, $900, and a stiff drink and I will be cruising on the water with power from the sun! Please let me know where all my mistakes are as I'm sure there are many.

You will need to allow for a DC blender, and what about a drink cooler?

Can't be much of a boat that will move using a motor drawing just 100 Watts...perhaps an itty bitty jon-boat.

With a stiff drink in one hand and control of ANY boat with the other hand, expect an invitation to participate in some afloat field sobriety tasks, at least in my jurisdiction. They are different from roadside field sobriety tasks, which throws some "professional" alcoholics for a loop.

I spend 200-300 hours each summer, mostly weekends, as a marine patrol officer for my home county. Getting impaired operators off the water and into our local Greybar Inn for the night is a big part of what we do. The typical criminal defense lawyer knows diddly-squat about marine law, so court cases are generally a breeze, particularly if the judge owns a boat. I enjoy the occasional deposition or subpoena, even though they eat into my HVAC workweek...sharpens my negotiation skills!

Tinker with solar PV boats to your heart's content, but leave the stiff drinks on the beach.

That's because things can go very bad very quickly when you are cruising at 5/8 of a knot.

Thank you for your service and keep the water ways safe. I do feel as though enjoying a drink while on my boat on my private lake is pretty safe. specially when were talking about a party boat controlled by a trolling motor at half throttle. I could do much more damage with a kayak and a 12 pack.

A handy way to determine output from a PV system is to use PVWatts Version 2.0, a free program available at http://www.nrel.gov/rredc/pvwatts/grid.html. For a boat application, the panels would probably need to be mounted horizontally which is not a bad orientation for the summer, and orientation is an input in PVWatts. However, PVWatts assumes grid-tie type efficiencies of 77%, while battery systems are assumed to operate around 50% efficiency, so you should downrate PVWatts output by a factor of 0.65. Since you are using a lot of the power when it is being generated, the average efficiencies should be somewhat higher.

You are correct in assuming about 50% maximum discharge from the battery. The 101 Watts for the motor only corresponds to 0.14 HP, but sounds like you have already have expeience with that amount of power being able to move your boat. Sounds like a good experiment for a modest off-grid system.

That you are on your own private lake reduces risk.

Believe it or not, we have had BUI cases involving canoes, and, once, an inflatable kayak and a 12-pack. The issue is the danger the drunk poses to himself and others wandering a busy waterway so impaired. My own policy in such cases is to get the fool to dry land and find him a ride home, but others deal with it differently.

Stay safe.

It would seem to me that a party boat with a trolling motor at half throttle is going almost no where. I slight breeze and you will be going backwards. That would be the first step, does a .14 hp trolling motor actually propel the boat?

When our gas motor died, we used a 44 lb thrust trolling motor on our 24' 'toon. Did not go fast but I have gone over 5 miles on a charge.The nice thing was it was quiet. No smelly fumes either.

Patrick T

When I took a bad fall roofing a house I could no longer paddle my canoe. 4 surgeries later I could paddle for just a few minutes before the burning pain set in. I then had a thought. A 100% solar powered canoe. After I Googled it all I saw was a few canoes with a solar panel tied on the front section of the canoe. Not eneough watts/amps and half the canoes space was gone.

OK long story made short here is what I came up with after a few builds and some improvements Reply if you like it :-)
https://sites.google.com/site/serenitysolarcanoe/home