Green House Co. Ltd, in Japan has developed an LED emergency lantern called GH-LED10WBW that runs on salt water!. The lantern weighs 680gram (23.98-oz). The lamp does not require any batteries rechargeable or otherwise to function. Just fill the lamp’s reservoir with salty water and voila!
All it requires is 16 grams (0.56 oz) of salt dissolved with 350 cc (11.83 oz) of water in a measuring bag and then poured into the lantern. The salt acts like an electrolyte in a simple wet battery, that uses a magnesium rod as an anode and a carbon rod as a cathode. During electrolysis, the magnesium ions travel to the carbon rod to generate electricity. The magnesium rod will have to be replaced with a new one, after 120 hours of usage, as it slowly gets destroyed by electrolysis.
The lantern produces 1.5 volts of DC power that can run its ten-LED white light, giving out 55 lumens of light. The lantern has a USB port to charge your devices at 4.5 volts. The LED lantern runs for eight hours before the saltwater needs replacing.
The LED lamp is intended for emergencies and recreation and will go on sale in Japan in mid-September 2012.