two limit switches, a timer, a motor.
start at position 1 (early morning). set the motor speet to reach the other limit switch according to the speed the sun travels across the sky with respect toyour location. panel reaches other limit switch (end of day)... waits 4 hours, then travels back to limit switch position 1 (take your time, you have all night).
a second motor could set angle which is different in the seasons as well.
wi-fi connect this PLC to the weather channel internet data stream so your controller knows what season it is in and what the length of sunlight time will be each day.