Not to mention, that solar energy isn't just disappearing. It's used by natural systems already. You extract energy from a system, it will have effects. We may not know what those effects are until we do it, but the idea that solar panels provide free energy that was just being wasted is silly.
A lot of solar energy is disappearing though, it is being radiated into space from rocks and so on.
Only a small portion is actually used.
Obviously we can't be so closed minded to put them were the energy is otherwise needed by a forest or to use so many that it redistributes energy too strongly but it is easy to do reasonably provided we don't get greedy.
This is all energy that was going to hit the earth anyway, and it will be re-emitted into space quite soon after it is captured. The flux from the earth wont change from using solar in this fashion. Problems arise if we capture solar energy in space and take it here, or we store a massive amount to use all at once. Mind you both of those don't seem to be well understood... but for instance if we got all of our power from solar panels on the moon we would be adding one hell of a lot of heat to the earth's system.