Dennis Siegel

Dennis Siegel claims his curious contraption feeds itself like a leech on ambient electromagnetic fields.

Say your Guitar Hero Warriors of Rock axe dies in mid-shred. You could interrupt your blazing rendition of KISS' "Love Gun" and go to the store to buy batteries. But that requires movement, and batteries are expensive.

Plan B. Try looking around for the nearest computer, coffeemaker, or other electronic device. There's free electricity in the form of electromagnetic fields just buzzing around these things. Why not, you know, just reach out and take a bit of it?

That's what German designer Dennis Siegel claims to do. The student at Bremen's University of the Arts says he's built a kind of electronic leech that charges a battery from the ambient power of other electronics. He calls it the "Electromagnetic Harvester," and you can see all kinds of practical scenarios (including one really creepy one) for the curious contraption below.

I recently shot some questions to Siegel about why he built this thing and what, exactly, it does. Here's what he had to say:

How did you come up the idea for the Harvester?

We are surrounded by electromagnetic fields which are actually pure energy fields. Consequently there is some energy that can't be completely consumed. This redundant energy can be used for other purposes like powering devices. Accordingly, I wanted to build a device that is able to harvest this energy while creating an awareness of electromagnetic spaces and their unheeded energy.

The idea for the project was born in a course at the University of the Arts in Bremen/Germany that was dealing with theories about physical and non-physical spaces as well as programs. I also got inspired by Hertzian Tales by Dunne/Raby, a great book about electronics, aesthetics and design.

What is the range? 15 feet? 5 feet?

The range depends on the strength of the electromagnetic field. If you have a strong field it is possible to charge a small battery within one day. It could be more effective but I am just a designer not an engineer ;-).

How do you think it will be helpful to people who use it?

Well, you gain energy for "free." You're just making use of already existing but unconventional energy sources. There are already prototypes of devices that are using electromagnetic fields to power themselves, like RCA's Wi-Fi power harvester. (Ed: There is some discussion about whether RCA's device actually works.)

What devices will it suck power from? Anything with an electromagnetic field, or are there limitations?

Where current flows is an electromagnetic field. So you could harvest an overhead wire as well as a toaster or a broadcasting tower. The only limitations are the strength of the field and its frequency (up to 2,4GHz). You have to place the harvester close to the source of the electromagnetic field to gain the most energy.

Do you have training in electronics? Or did somebody help you build the Harvester?

I am working a lot with Arduino and other microcontrollers which are making it pretty easy to build effective integrated circuits with less effort. Of course, it was quite hard to find out the correct lengths and coil windings, especially to make the whole system suitable for a larger field of frequencies. My harvester is just a very rough device but it works and makes me proud!

Before going out and building your own Harvester, note that Siegel has planned a couple of prototypes. He says: "There are two types of harvester for different electromagnetic fields: a smaller harvester that is suitable for lower frequencies below 100Hz which you can find in the general mains (50/60Hz, 16,7Hz) and a bigger one that is suitable for lower and higher frequencies like radio broadcast (~100MHz), GSM (900/1800MHz) up to Bluetooth and WLAN (2,4GHz)."

Photos courtesy of Dennis Siegel.

About the Author

John Metcalfe
John Metcalfe

John Metcalfe is CityLab’s Bay Area bureau chief, based in Oakland. His coverage focuses on climate change and the science of cities.

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