Has anyone thought about generating energy through keyboard strokes using the same method as energy from floor tiles? Under each key a small piece of metal could be built in and electricity could be gained from the deformation of the metal following a key stroke. Though this energy would be minuscule, a small contribution could be made if we pool all of the worlds keyboards. Imagine how many times a keyboard key gets pressed every day in the world. Let's do a Fermi calculation:
Roughly 2*10^9 people are connected to the internet today.
Let's assume that the average person performs 30000 strokes, but a lot of people don't use their computers daily, so we'll reduce that to half.
So this gives us (2*10^9) * 15000 = 3 * 10^13 keystrokes!