German student builds electromagnetic harvester to recharge a battery | Hacker News Reader

German student builds electromagnetic harvester to recharge a battery

phys.org

49 pointshoag32 comments

You would think that phys.org would know their physics. He's adding an inductive load to wherever the energy is coming from. In some cases that will simply replace other loads, but in many cases it will add to the load, increasing energy wastage.

Phys.org: the Forbes.com of physics (questionable content quality, link-bait title, and so many ads, even in the body of the text -- reading from ipad right now)

That explains why he's standing next to a substation and who is paying for the power.

Indeed, anyone who took high-school physics should know this. This exact idea was disussed in our class, I still recall it some 30 yeara later....

I fail to see how harvesting existing electromagnetic fields would increase the load, unless we consider the potential loss of range?

In near field zone (low frequences, mains and DC-DC converters) the device acts like a secondary coil of a transformer, so it drains power from some other device.

In far field zone (high frequences, bluetooth, wifi) it captures part of already emmited wave, so it doesn't place additional load on emitter directly. But since device blocks wave propagation through itself if placed between transmitter and receiver it will degrade reception. And that in turn can result in automatic increase of transmitter power (in case of GSM phones at least). Which will increase transmitter consumption.

Think of it as a tremendously-inefficiently-magnetically-coupled transformer. The power line or wifi antenna is the "primary winding" and the antenna in this box is the "secondary winding" and the air in between them is doing an awful job of being the iron plates a normal transformer winds those wires around to direct and concentrate the magnetic fields. Power drawn out of the secondary coil results in power draw in te primary coil (multiplied by the inefficiency of the transformer). The reason this appears to work is that no-ones measuring the increased power draw from the source - since the device is only drawing microamps or possibly single digit milliamps at a volt or two, no power company is going to notice a few milliwatts of extra load.

On the other hand, if you stacked 20 or 30 of these around your ~100mW wifi basestation, where do you suppose the power extracted comes from (and, as you suggest,what do you suppose would happen to your wifi range? I also suspect loading up the transmitting antenna like that will change enough about the way the transmitter/antenna system works, and degrade the transmitter output in even more serious ways than just the raw power extracted might indicate - I'l guess the frequency and resonance assumptions made by the transmitter designer would all be wrong.)

I don't know why the parent was downvoted, it's an honest question that's encouraged lots of high-quality responses. Here's mine:

Faraday's law of induction: A changing electric field through a coil induces a current in that coil. Induction is how transformers work. Hopefully you believe that attaching things to a transformer's output can put a load on its input.

Since this device and transformers both use induction, if it can happen in a transformer, it can happen with this technology.

Every bit of metal acts like an antenna. You could think of it as the receiver creating it's own signal that counteracts the transmitter. (Powered, of course, by the transmitter itself.)

Not unlike a hand-crank generator. Turning it without a load connected is easier than with a load. Without a load, no current flows through the generating coil. With a load, current flows and generates a counteracting magnetic field that resists the turning force.

Come on, this is silly, the article makes it seem like it's creating energy from thin air, while of course it's adding a load to the EM field, which results in an increased energy drain from the source. Obviously no one is going to notice if you recharge an AA battery using this system, but it's not any different than just plugging a charger straight into your (or your neighbour's) power socket.

You clicked the page, ads were shown, mission accomplished!

What's interesting about this article is that after reading it you might get the idea that the student created this device to recharge batteries and produce electricity.

However when you read the announcement[1] of the university itself you learn that he was awarded the price in digital media because:

> "Dennis Siegel thematisiert die sich überall befindenden elektromagnetischen Felder[...]" > TRANS: Dennis Siegel thematizes the everywhere occuring electromagnetic fields)

and further

> "Die Jury hat an dieser Arbeit den feinen Humor der Arbeit, den gedanklichen Kurzschluss, die Fähigkeit zum konzeptuellen Brückenschlag, die sensible einfache Gestaltung sowie die Zukunftsorientierung des Projektes hervorgehoben und überzeugt"

> TRANS: The jury has emphasized and was convinced by the fine humor of the project, the mental short circuit [it's not clear what this refers to in the announcement], the ability to create conceptual bridges, the sensible simple design and future-orientation.)

After reading this announcement one might actually come to the conclusion that this an art project and that the fact that a student created a device that charges batteries using electromagnetic fields by itself is rather boring and irrelevant. The fact that any high school student should have the necessary theoretical knowledge to built such a device could also be a give away.

[1]: http://www.hfk-bremen.de/t/auszeichnungen/n/hochschule-f%C3%...

Physorg? Ugh.

Didn't even bother click, came here to read comments instead.

Can HN please ban Physorg like everyone else?

It's also quite illegal to take power from mains lines even inductively. If this kind of thing catches on I imagine the manufacturer would have a lot of lawsuits on their hands.

>But that clearly isn't the point of his device. Instead, it highlights not only the fact that we live our lives in a constant state of bombardment of electromagnetism, but also that all of the energy from all of the collective devices in use in the world today, is currently going to waste.

I prefer the "fluorescent tubes under transmission tower lines" demonstrations. Here's one link (http://hacknmod.com/hack/field-of-fluorescent-tubes-powered-...) but there are others.

It's neat to be able to do. I'm pretty sure the energy harvested comes nowhere near the energy used to create the parts, or assemble the device.

If you want to make a really simple demonstration that "there's power in the air" you could try this experiment - light an LED from cell phone frequencies (http://www.creative-science.org.uk/mobile_LED.html). (Good Luck getting an OA91 diode, though.)

Didn't Tesla at one point envision giant coils that would basically give you "wireless electricity" through the use of changing magnetic fields?

This is cool but I'd be worried if it caught on in any sort of scale.

Yes.

http://en.wikipedia.org/wiki/Wardenclyffe_Tower

I think the resulting resistivity and wasted electricity would make it unfeasible for mass usage over distances even if it had been funded to completion.

I wish portable device OEMs would adopt inductive charging more though. No worrying about cables or broken ports.

If you lost a $5 cable or broke your $1 charging port, the OEM is economically motivated to get you to shell out a three-digit figure for a new phone.

Given this simple and obvious observation, the fact that phone manufacturers have mostly dropped proprietary charging interfaces in favor of USB seems like a minor miracle.

Yeah, very true. It's actually pretty easy to replace USB ports on many mobile devices. I read about users doing it all the time on Android forums and rather cheaply. Mostly depends on how easy the device is to open up and repair though.

The main problems with having a huge EM field to power the entire planet (or even just a city) are that: - every piece of conductor of the right length is basically an antenna for the frequency at which the EM field resonates, therefore will generate a voltage across its extremities that can generate wild sparks and cause electric shocks; - an EM field (and pretty much any other field) in the space is proportional to the inverse of the square of the distance from the source, which makes it for a pretty inefficient way of transmitting energy at long distances. The field could be not isotropic, for instance by "focusing" it in one direction, but that defeats the purpose of accessing the energy from everywhere.

The particulars of the electronics inside his device haven't been detailed (likely to prevent copycats)

More likely because this is hardly a new idea and people have been doing this for decades. I remember reading in an elementary school science book how some farmers used to run fences under power lines going through their fields to get some "free" energy out of the electrical grid. This did not go over well with the electricity utility.

as others have said, you're either absorbing a wave (and blocking someone's signal) or acting as an extra coil (and making the source do extra work).

It's perpetual motion nonsense to suggest mounting these on roofs to power buildings.. Apparently phys.org is as bad as new scientist!

This reminds me enormously of the simplest electronics project I ever put together: A Crystal Radio back in the '70s. If you're not familiar with them, they're not much more than a coil and a "cat's-whisker" (diode) and they are powered by the radio-waves themselves.

Since this increases the load on the source, isn't this more like stealing than harvesting?

This is AWESOME!

> He's won a 2nd place award in the HfK Bremen Hochschulpreis 2013 competition for Digitale Medien, for his efforts.

Who on Earth won first place?

The first price in this category went to someone who built a robot arm controlled by the emotional reactions of a sensitive plant[1][2].

[1]: http://www.hfk-bremen.de/t/auszeichnungen/n/hochschule-f%C3%...

[2]: http://en.wikipedia.org/wiki/Mimosa_pudica

The guy that did it with wires.

I'm not convinced that the device actually does what it is advertised to do. Considering that the student is associated with a "University of the Arts", the non-disclosure of the layout becomes even more suspicious, as is the implied claim of being able to harvest useful amounts of energy from Bluetooth transmitters.

It would be quite in line with German culture for somebody to have no qualms about lying for the purpose of calling public attention to some perceived environmental threat or health risk (think the Green party scaremongering against genetically modified crops using flourescent dyes) and then saying it was all art for a good cause if called out on it.

WTF? I read your second paragraph twice, wouldn't believe my eyes.

You claim that publicly lying is part of the German mentality?

Deleted comment

Thanks for your convincing illustration of the concept of prejudicial rubbish. I'm German myself.

Whether or not the view I expressed is rubbish, I believe the term "prejudicial" is applied incorrectly here. My opinion of the German environmentalist movement and the methods that are considered appropriate within it is certainly harsh and judgmental, but it was formed in a long process of disillusionment from an initially sympathetic position I had for them.

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