A simple solar tracker powered by water weight

Sunny Slope

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I have two water wells on my property with 24 volt DC submersible pumps powered by photovoltaic panels. The pumps are hooked up PV direct; in other words there are no batteries in the circuit; the panels power the pumps directly. Both wells are very low producing, so to maximize output I need to maximize the hours of optimum sun angle on the panels.

In summer when the sun moves through its greatest arc, having the panels track the sun's movement throughout the day increases my wells' output by around 40%. Tracking is less important In winter when the sun's arc is smaller and my water requirements are lower. I also use pump controllers with linear current boosters, which dramatically increase pump speed during low light conditions by trading off excess voltage for current to get the pumps at least running slowly rather than stalling. Since solar systems are so expensive, it really makes sense to maximize system performance with tracking if possible.

I came up with this simple low tech method of tracking that has worked reliably for many years. My system uses the weight of water in a 5 gal. bucket to rotate the PV panel four times a day. The PV panel mounts with two pivot bolts to a triangular frame so it can rotate through 90 degrees. Springs pull the panel toward the east, while the bucket pulls a rope to rotate the panel toward the west. A battery powered irrigation timer is set to add water to the bucket four times per day. Each time it does, the bucket pulls harder against the panel, rotating it to a new position. (A water line between each well and tanks uphill passes by the PV panels, so I already had pressurized water available.) At the end of the day a separate timer drains the bucket, and the springs rotate the panel back facing east again for the next morning. The PV frame mounts to a tower with adjustable struts so I can manually adjust the north/south tilt flatter in summer and angled more southerly in winter.

Calibrating the timer and springs was simple. I just went out at around 10:30 a.m., manually turned on the fill timer, and noted how long it needed to run to rotate the panel the right amount. I repeated this at 12:30 p.m., 1:30, and 3:30 and programmed the timer accordingly. I used three springs that engage successively to apply more resistance as the panel rotates. The springs and bucket connect to the panel with ropes, guided by small pulleys. Half of an old bicycle rim attached to the panel works like a big pulley so the ropes pull on the panel at a constant radius. The panels track consistently, even on windy days.

Photos can be seen here, and more discussion here.
 
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Patty

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That is so cool. So simplistic and yet elegant.
Where do you live? And would you consider doing some consulting work to help me set up solar for my spring? I am not totally electrically challenged, but this is too much of a learning curve I think.
 

BarredBuff

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That is so cool. So simplistic and yet elegant.
Where do you live? And would you consider doing some consulting work to help me set up solar for my spring? I am not totally electrically challenged, but this is too much of a learning curve I think.
Hey Patty! Welcome to SufficientSelf!
 
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