Most school children at some time made a battery by sticking copper and zinc strips into a potato. It does not work very well but now Alex Goldberg of Hebrew University in Jerusalem and colleagues have found a simple way to get 10 times the voltage: just boil the potatoes first.
Lest this sound frivolous, it turns out that energy production from potatoes can be 50 times cheaper than common batteries and could actually be useful for low-power appliances in developing countries. This is one to try at home with the kids!