Uses
The way PV are used is generally divided in to the following catagories

Simple PV Systems
Simple systems are used for devices which do not need to be operating all the time. Eg. A water pump.

Battery PV Systems
A battery system's are generally used for unatennded devices which need to be running all the time or during the night. Eg. a park light.

Generator PV Systems
Generator systems are used when the PV's cannot provide all the electricity required to run the Device. Eg an airconditioner.