It ain't gonna work, and perhaps an expert on the subject on optics or energy can explain that better than I can.
What the comic depicts is called a "Perpetual motion device". The entire object behind "Perpetual motion" is to make energy go on forever. Now I know the comic above is merely a joke, but the truth is that many scientists have tried to make such a device working, including Leonardo Da Vinci. So far all attempts failed, and the general consensus is also that the entire concept is an "epistemic impossibility".
Yet the idea is very cool, in this case funny.
