Solar power is energy derived directly or indirectly from the sun.

It may sound funny, but except for geothermal or nuclear energy almost all power is indirectly derived from the sun. (Wind Power after all is nothing but the airflow from one region to another caused by pressure differences, which are in turn caused by heating airmasses, the heating is done by the sun).

To uncomplicate matters a bit on this site we'll refer to "solar power" to indicate direct photovoltaic conversion, or direct conversion into mechanical energy or concentrated heat. In other words, solar power takes sunlight and converts it into useable energy immediately.

We're not concerned with say biomass conversion when we talk about solar power (by that definition the whole oil industry would qualify as solar powered).