The next time you go camping, instead of bringing batteries to keep your lantern running, you might only need to bring a salt shaker or a really sad book. Japanese company Green House has developed an LED light that runs on just salt water.
Using a dedicated water bag, campers would only have to mix up a saline solution of salt and H2O to keep the lamp glowing for up to eight hours at a time. The salty mixture serves as an electrolyte between a set of magnesium and carbon rods that function as negative and positive electrodes inside the lantern to produce electricity. It's not all virtually free energy though; the magnesium rod is only good for about 120 hours of electricity production, but replacements will be sold separately when the lantern goes on sale sometime this month. [Green House via Tech-On!]