Harnessing the energy of children at play

It's a common observation among mature adults that when they watch children playing they muse "I wish I had that much energy." Some extremely imaginative individuals have figured out how to harvest that energy for practical use. Playpumps International hooks a playground-type merry-go-round to a water pump, so that when children push it around, they pump groundwater up to where it can be stored and used. This virtually eliminates the risk of surface-water-related infectious diseases in the community.

The fence, clothespin, and advertisement in the post above this one are labelled "clever," but it's for inventions like this one that I created the category. I strongly recommend viewing the brief video at the company's website. It's the cleverest idea I've seen all year.