Radio signals are mostly used for information transfer purposes, but the energy they contain is mostly left unused, bouncing off the various obstacles until all of it is transformed into lost heat. Nihon Dengyo Kosaku, a Japanese company, has come up with a device that harvests radio signals and uses their power.
Their “rectenna,” (rectifying antenna) and even showcased at the Tokyo Big Sight exhibition. The rectenna catches WiFi and digital terrestrial broadcast signals, and has two antennas, one for each band. The WiFi has is 12 millimeters thick and the digital terrestrial one is 30 mm thick, both looking like a plain soft-white pad.
The rectenna isn’t something you can say it charges a Leaf or even an MP3 player. Its 0.6 microwatts at 1.2 mV are barely enough to light up an LED. However, if you’re very close to a transmission tower, such as the Tokyo Tower at 5.5 km, the device can harvest up to 6 mW of electricity.
If you think about it, you may actually find some good sources of radio signals in your home or even your office. The electromagnetic pollution is already an old reality, and if you have enough of these devices around your home, you may actually lower your electricity bills by a few bucks (but really, you should have many of them).