Patent ID: 8563845

Claim:
A method of determining a time to deliver an amount of energy to a load in a solar powered system having a solar panel, comprising differentiating artificial light from natural daylight by: (a) providing an energy storage device for receiving energy from said solar panel; (b) providing a processor; and (c) providing a circuit for sensing photovoltaic output of said solar panel and for signaling said output to said processor to differentiates the artificial light from the natural daylight by: (i) periodically measuring a value selected from the group comprising the short circuit current of said solar panel and the open circuit voltage of said solar panel; (ii) measuring a rate of change of said value; and (iii) determining the onset of day when both of the following conditions are met: 1. said value is above a predetermined threshold associated with daylight; and 2. said rate of change is larger than a rate of change for true dawn.