Rain is normally a solar energy cell's worst nightmare, but a team of Chinese scientists could make it a tremendous ally. They've developed a solar cell with an atom-thick graphene layer that harvests energy from raindrops, making it useful even on the gloomiest days. Water actually sticks to the graphene, creating a sort of natural capacitor -- the sharp difference in energy between the graphene's electrons and the water's ions produces electricity.
The catch is that the current technology isn't all that efficient. It only converts about 6.5 percent of the energy it gets, which pales in comparison to the 22 percent you see among the world's better solar panels. If the creators can improve the performance of this graphene-coated cell, though, they could have a dream solution on their hands -- you wouldn't have to live in a consistently sunny part of the world to reduce your dependency on conventional power.