I thought I had a perpetual motion idea, but then decided to read up on the subject and realized that I don't. But, still, I have an interesting idea. If we can put lights in our lawn that gather energy from the sun during the day, what if you put a lot of them in a room full of mirrors and shined a flashlight at them for a few hours? After that, couldn't the resulting light keep the solar panels charged, thereby permanently illuminating the room? I was never good at all this science stuff, so there could be issues of heat and the efficiency of the panels or the lights -- not to mention the practicality or utility, but I wondered if it had practical benefits.
I mean, take the modern hybrid cars. Friction caused by braking creates the power used by the electric motor that assists the gasoline engine. Would have to think at some point the efficiency of solar panels will be to the point that putting them around giant light sources (like stadium lighting or casino signs) could result in recouping some of the electricity required to power them. (Or if really efficient panels in good quantity mixed with really energy efficient lighting, maybe all of the power required?)