A teenager in rural Nepal has figured out a way to potentially cut the cost of solar panels by 75%: Human hair
instead of silicon. At first he was just thinking of his village, but now he's thinking a bit more global. After all, if the hair is good for a few months, that means that even in remote, developing areas people will have grown the replacement parts necessary by the time their solar panel stops working. Properly distributed, I have to say it sounds like this could actually be a pretty significant step forward.