Ryan K, a member of the Maui Makers hackerspace, has developed a laser powered by one of the strangest renewable power sources ever: tropical fruit! To be more specific, the power source is the Hawaiian Lilikoi fruit (more commonly known as passion fruit). By using the fruit in conjunction with anodized bolts (source of zinc), thin copper pipe, wire, switches, LEDs and a capacitor, he was able to create a battery that literally grows on trees!
What is interesting about the Lilikoi vine is that it produces a massive amount of fruit in Hawaii, which is often viewed as a nuisance for any home-owners who own a tree. When the fruit drop, it has to be cleaned up, otherwise it rots and attract insects. Designer Ryan noticed that the fruit had a strong acidic taste and thought it would work well as a battery.
Attaching his newly constructed fruit battery to a small green laser, Ryan was able to emit a small pulse. An optional volt meter was used to show the current charge available on the 6800uf capacitor, while an on/off switch with LED indicator light was used to activate the laser. Of course, this drained the power pretty quickly.
Still for a fruit-powered laser capable of reaching at least 3v (max charge is approx 3.8v), it is quite an achievement! Could we soon see a day when we power our gadgets with rotten produce?