I have two water wells on my property with 24 volt DC submersible pumps powered by photovoltaic (solar) panels. The pumps are hooked up PV direct; in other words there are no batteries in the circuit, the panels power the pumps directly. Since the pumps only run when there is sun on the panels, to maximize well output I need to maximize the hours of sun exposure. Having the panels rotate throughout the day to track the sun's movement does that. Since my wells are low gallons per hour, being able to pump for more hours per day can increase production by 40% in the summer. Commercial PV panel tracking systems are available but quite expensive, so I came up with a simple low tech method that has worked perfectly over the years. PV direct water pumping really benefits from tracking, especially in the summer when you typically need more water and the sun moves across the sky in a bigger arc. But any small solar panel installation would benefit from the same system. I also use pump controllers with linear current boosters, which dramatically increase pump speed during low light conditions.
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. 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 programed 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. I imagine another method would be to use a linear actuator or gate opener powered by a sprinkler timer (the type that turns sprinkler valves on and off). In my case since I am pumping water I had water supplies near each well. Since solar systems are so expensive, it really makes sense to maximize system performance with tracking.
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