I want to power an electric 20-foot launch by solar panel only, no battery banks.How much solar panel wattage do I need to make about 8 knots?Thanks.
The general rule is that, if you are going to power directly from a solar panel, the output of the panel should be 10 times the draw of the appliance. A motor that will drive a boat of that size will draw over 125 amps at 12v. So you will need 1250 amps of output . a solar panel that is about 49 X 44 will output 9 amps of usable power at 12v. So, You will need at least 140 panels they cost around $700 each in quantity. Each panel is about 14 sq ft so you will need about 1960 sq ft of panels at a cost of nearly $10000. A 20 ft boat with a beam of 8 ft might have a 160 sq ft of canopy available Sooooo You will have quite an overhang on your solar array .
About the size of a foot ball field
I bet you could reach that speed with a 36-volt, 101lbs thrust motor, peak amp draw around 38 amps, so you're lookin at about 1400 watts. If you wanted to try a 24-volt motor at 70 lbs thrust, you would only need about 1000 watts.
