I had to look at the circuit to figure out what is going on, basically the solar panel changes the cap til it hits a certain point which the motor engages and then went its low, charges again..i think.
Its not a bad idea. I have a bunch of old large caps kicking around that may make use of this in the future.
http://www.instructables.com/id/Energy-Harvesting-for-Solar-driven-Water-Pump/
http://www.instructables.com/files/orig/FJH/IO7L/HHS02OKG/FJHIO7LHHS02OKG.pdf