SOLAR TUG BOAT

Actually, just a solar deck for a stock Vac-U-Tug Jr.

Since the stock motor draws only 0.45 amp, and with the receiver and electronic speed control installed including servo use averages only 0.75 amps draw, a solar power supply seemed like a good idea. 

Stock tug cruising with the solar panel. Sits a little heavy in the stern. I didn't remove ballast to compensate for the additional rear weight of the panel. From the wake, you can see it is moving along pretty well.

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This home-made panel has a rigid base of 1/8" PVC with 14 multi-crystalline cells wired in series and taped in place. The panel is 5-1/4" x 12-1/4". The panel is covered with .040" clear polycarbonate. Each cell is approximately 2-7/16" wide by 1-5/8" high. 
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Wired in series directly to the leads to connect to the ESC (Electronic Speed Control) as a substitute for the battery. Very low-tech application. 14 cells x .5 volts each = 7.0 volts. Any single solar cell produces approximately 1/2 volt. The voltage is constant. The amperage depends on the size of the cell. Bigger cell = more current.  This wire plugs into the ESC providing all power to the model. No separate battery pack is needed. A small block of foam supports the end of the panel to the stern of the boat. 
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Solar cells are like paper-thin sheets of glass. They are fragile. They can be cut by scoring with the tip of a carbide or diamond engraving tool. Score, then break, like cutting glass. Work on a hard flat surface to support the cell while scoring & breaking. These were originally 2-7/16" x 2-1/4" cells that I cut in half. I used muti-crystalline cells because they were less expensive than mono- crystalline cells. They are more fragile as well.  The supplier sold this flat tinned tabbing wire to connect the cells. This is the cross-connection at the end of the two rows of cells. 
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Late morning sun shows 7.9 volts open-circuit. Shorted circuit shows 0.61 amps available. This panel runs the boat best when the sun is overhead.  Tilt the panel a few degrees to point directly at the sun and you get 0.70 amps. I will get more amperage if I remove the cover or used a space-age non-reflective cover to reduce reflected energy, allowing more solar energy to reach the cells. 
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I was a little nervous with this application as the panel hangs off of the rear of the tug. A hard impact with another boat could damage it. I have considered raising it up and moving it forward like a canopy. 
 

TM