At night, a glass-walled lab halfway up a hill in Japan glows with light from 800 LEDs. The electricity comes from a system built around 1,500 wooden boxes of soil and compost.
The lab, called Ku-An, is a test site for a system developed by product designer Satoshi Nakagawa. He calls it "micropower collection" because each unit supplies only a tiny current. The system uses a principle found in an early battery. Two different metals, such as zinc and copper, are placed in damp material. When the metals are connected through a circuit, chemical reactions create a small current.
Combining many small units makes it possible to draw more power. At a second lab nearby, Lu-An, about 2,000 cylinders hold soil and compost. Nakagawa's company puts the system's maximum output at 100 watts. One possible use is powering sensors that check crops for damage from pests in fields far from the power grid. Nakagawa has also used the technology in art. He set flexible rods in the ground so their tips would glow like fireflies on tall grass.
Masayuki Nakao, an engineering professor emeritus at the University of Tokyo, said the system provides far less power than ordinary batteries. He still sees value in the installations and says the lights can move people. Nakagawa's focus is on finding devices that can make use of the small amounts of power the system can supply.