A Tiny Box That Charges AA Batteries From Electromagnetic Fields

Gadget-charging juice is in the air all around us. Dennis Siegel’s small white boxes harvest it.

A piece in the current issue of Mother Jones makes a compelling case that lead, the element, can be traced as the cause of a surge in violent crimes in the ’80s and early ’90s. Exposure to leaded gasoline and lead-based paints, the theory goes, quietly tweaked the brains of an entire generation, causing lower IQs, hyperactivity, and behavioral issues that later manifested themselves as crime. It’s inconclusive whether lead is indeed the U.S.’s “real criminal element,” as the story says, but it does get one thinking about the potential effects of the other myriad invisible forces all around us, like Wi-Fi or cellular signals.


Dennis Siegel, a digital media student at the University of the Arts in Bremen, Germany, has harnessed one such force for his most recent project, for a decidedly less worrisome aim. His Electromagnetic Harvesters are small devices that wirelessly leech off electromagnetic fields to charge AA batteries.

The operation is straightforward. Holding one of the small white boxes up to any electromagnetic field–ubiquitous, invisible things produced by antennas, thunderstorms, and just about anything plugged into an electrical socket–slowly starts transferring a charge to a AA battery. It seems like magic, though Siegel points out that many other devices, from induction-charging toothbrushes to antenna-powered crystal radios, work on the same principle.

Still, designing the harvesters was “really time-consuming and expensive” for the non-engineer. “It was quite hard to find out the correct lengths and coil windings,” he says, “especially to make the whole system suitable for a larger field of frequencies.”

But Siegel did come up with a working prototype, which he says can leech power from “radio waves, Bluetooth, WLAN, cell-phone frequencies, digital television … not to forget the general mains.” It even picks up the static electricity generated by giving his dog’s head a quick rub, as seen in the video clip.

The potential for such devices seems immense, and the designer did succeed in “creating an awareness of electromagnetic spaces and their unheeded energy,” one of his aims for the project. Still, there is a long way to go before that energy adds up to something meaningful. Siegel’s harvesters charge at a rate of about one AA battery every 24 hours.

See more work on the designer’s site.