Oh, cute: Paralleling two (essentially identical) panels + to - and - to +. I've been trying to figure out how to do something like this with minimal additional components and your arrangement just does it with NONE. B-)
- The generated voltage is the diode drop so even though each panel is forward biased by the other it is only forward biased by the amount of its own voltage drop, which doesn't drive it into conduction. No current flows in a given panel except through light-formed electron-hole pairs from its own illumination.
- The maximum current through each is its generated current and the available current for the load is the difference of the panels' currents.
- The open-circuit voltage is the voltage of the more-illuminated panel minus its resistive drop from its load current - which is the sum of the current from the less-illuminated panel and the load proper.
- "Shorting" a panel - by driving an equal current from its opposite number panel through it - doesn't hurt it, nor does applying a reverse voltage of no more than its own sum-of-drops.
- Panels can be large enough to collect enough power to run a serious gearmotor for a big load, without major expense. (Or you can use tiny panels and polarized relays to steal major power from the big panel when it's time to move.)
For better tracking I'd mount both panels facing "forward", side-by-side along their narrow edge, with a long baffle between them also pointing forward. With very small errors it would quickly shadow the "off" panel. (Make it a double-sided mirror and it will also "double" the "bright" panel, if the latter can stand 2x solar input when off-axis.)
Motor will start when output current is high enough to break any cogging and bearing standing friction, stop when voltage is low enough that bearing sliding friction and eddy losses overcome the available power (which might be AFTER the panel comes to center due to inertia). So the panel will track with a start-stop and lag angle. Gear it down far enough and the motor will run slowly all day and track at pretty close to a constant angle.
Since you only have to move "forward" for most of the day, rather than track back-and-forth, (though reverse voltage is good for braking to reduce inertial overshoot), you might separate the cells a bit and use a T or box-shaped baffle so one only one cell is "on" at a time. This will keep the "off" cell from stealing power and make more available for the motor, causing the lag angle to be lower and/or letting you get away with smaller sensor panels.
As others have mentioned, mirrors can direct "turn-around" light at the back-up panel from somewhat off-axis while baffles block it from the go-forward panel. (Or just add one or two extra "go-back" panels at other angles if you don't get a lot of scattered light.)
Sweet!
