Solar powered pontoon, question.

Hello, boat community. My name is Daniel. I have an idea to build a solar powered boat. Can some of you with a little bit more electrical knowledge help me out to get overall idea what I need.

ok, here it is. The motor I will be using is Torqeedo 4.0R. here are some specs:

Input power in watts 4,000W
Nominal voltage 48V

So if I want to run it at full power: How many solar panels I need?
Do I need batteries as a buffer between motor and panels? What kind of battery bank I need?

Thank you for help.

 

You can expect about 8W per ft/sq. For 4000W you need 500 ft/sq panel. That will only work at noon.

 

That's too low, you can get 100-200 W per m^2. 150 W / m^2 is around double gonzo's numbers above.

But you can expect only about 5 full hours of sunshine per day (effectively), and also you'd need 25 m^2 or so to supply 4000 W directly from the panels, so yes you will definitely need batteries.

 

Hi Daniel,
At full power your engine will draw approx 80 Amps from a 48 volts battery bank (4 batteries of 12 volts in series). If you choose 100 Ah types and discharge them to 50% you can run at full power for approx. 40 minutes on a cloudy day. A bit longer on a sunny day if you have a lot of solar panels, but you can not install enough panels to draw 80 Amps continuously because that would require 40 panels of 100 W each.

 

Some manufacturers claim about 13W ft/sq, about 60% more than what I said. However, that is for a static installation with compensation for the sun's declination. That means it is not installed flat but so that the angle of incidence of the light is 0. In a boat that will never happen, unless occasionally withing the tropics.

 

Thank you for the replies. Well, the pontoon I will have will house 32 250w panels. So by my calculations it is 32*250w=8000W. And lets assume that loss is around 25%, so I still make 6000 continuous power, isn't it enough to power the 4KW motor continuously?

 

Only at noon if the panel is tilted towards the sun. What is the size of the panels?

 

250w panel are 1.6m*1m or 64in*39in. I will have 32 of them.

 

My fixed solar installation has southeast oriented panels at 60 degrees angle and an Amps gauge calibrated in % of peak power.
100% I see only on exceptionally bright, windy days around noon, say between 11 and 1 o'clock. On hot summer days the needle touches 80% max. because the panels get hot, on normal sunny days it reaches 70%.
From 6 to 11 AM the gauge climbs from 0 to 70%, from 1 PM to 6 PM it drops to near 0 again, so the average over a 12 hour period is between 30 and 35%.

On a boat you may expect even worse figures unless you build an articulate system that tracks the sun in both direction and angle.

 

Batteries as a buffer will give even worse performance. The solar panels don't produce enough energy for the motor, so the extra weight won't help at all. If the batteries are pre-charged, then the panels can extend the use of the boat. The extra expense, lack of performance due to weight and windage, don't seem to make it efficient.

 

Have you considered wave power?

I tried posting a video of my prototype but this site freezes at 97%

 

If you can't upload to youtube upload it on http://vimeo.com/