Solar energy is generally thought of as a renewable source of energy. This is because the energy the Earth receives from the Sun is perpetual on a human time scale. Solar energy can be thought of as an constant flux of energy, with an unlimited duration, thus making it renewable.
In comparison, fossil fuels are non-renewable because there is a finite stock of them available. So in simplistic terms, we will eventually run out of fossil fuels because they are a stock, but we will never run out solar energy because it is a flux.
However the manufacturing of technology to harness solar energy is not necessarily renewable, but that is another story. [snax_content]