Elizabeth, It would be very interesting to find out more about how that energy harvester device actually functions. In fact, ti would be intensely interesting. Of course, many electrical systems do radiate an elecrtcal field, and it does surround us in most areas served by the power grid. That is the reason that shielding of low level signals is needed. Proof is very simple if you have a higher-impedance input digiatl voltmeter. Just ground the common lead and connect the other lead to a few feet of wire, to serve as an antenna, and set the range switch to a low AC scale. You will probably read a few volts of AC. But if you grab the two input connections with your hands the reading will fall quite a bit, because the source impedance is very high. The fact is that a high impedance source is not able to deliver much power to a low impedance load.
So that is why I seriuosly question the ability of any collection device with the small area that we see in that photo to collect even enough power to light even a very efficient LED. Somethong just does not seem quite right. So I am challenging the assertion that this device is able to do what it is claimed to do, far more than I am challenging the legality of it capturing energyu from the power lines. As engineers we are responsible to challenge things like perpetual motion systems, and this one sounds similar.
William K., I apprecite your comment, and of course remember well the lively discussion of "that German kid's energy harvester." I think it is important to include this invention in coverage of this space because it shows what can be done and what inventions people are coming up with. I guess it remains to be seen if this device will be used or what trouble people using it can run into if they do indeed "steal" energy. Perhaps as you suggest the energy recoverable is not useful, and then there are no concerns about thievery in this situation.
It's interesting to see all the discussion around these energy harvesters and I of course agree it's an exciting space that's ripe for even more innovation. It seems there is still a lot of controversy around the device that harvests energy from "air," which isn't really air but electromagnetic waves coming from other sources of energy that others may or may not be paying for. If you remember, there was a lot of similar commentary when I wrote a story focusing on that topic: http://www.designnews.com/author.asp?section_id=1386&doc_id=260486
Big2thumbs maybe you are correct because i mentioned that i have read some where i wasnt sure about it . According to me it milliAmps, however when you come to know the exact fugure please let me know as well .
@miner and @JackB - you are right that getting energy from utility lines by magnetic induction is stealing. But most energy harvesting applications come from sources that are free (road vibration, noise, ambient light). Yes, we do need to know how many watts we need for our harvesting application but for many needs, we don't need much. Think of a tracking collar that wildlife biologists attach to animals and the investment in the collar, the valuable data on its herd, the investment in temporarily trapping or rescuing the animal. It's a sad day when the battery dies. Now, keep in mind that many of these collars use 1 or 2 micro-Amps in hybernation mode, then periodically wake up to sense and transmit data. While in hybernation mode it is useful to capture microwatts of energy to charge a super-capacitor and perhaps a battery for that brief burst of data transmission.
Another example is sensors to tell an irrigation system what specific parts of a field need water rather than just spraying water all over the field.
Not all energy harvesting is about big energy savings. Many times we just need to apply it to the Internet of Things when conventional energy sources are far away.
Regardless of the generated voltage ,I mean the current delevring output it may came in this smale value.
And its great notice to say that MOSFET will amplify the current But is that mrans that will be include a micro transformer for faithfull amplefication i have no idea about the complete system, your clearance is highly appreciated .
JackB got it right--it is stealing energy! I'm really disappointed that all but one of the posts related to this article seem to think this is a great idea. And, when assessing the usefulness of the harvested energy, we need to be talking about how many watts can be harvested. The number of amps available doesn't mean anything.
Excellent slide-show Elizabeth. Fascinating to see how engineers are thinking beyond commonplace methodology. Even though engineering principals are used in developing these marvelous alternatives, the creative process is difficult to teach. I really think that necessity is the mother of inventions and these researchers are definitely on the proper track. Again, very good post.
Hi, Radwan, Your question was mine also as I recently attended an online Design News / Digi-Key class on energy harvesting by Paul Nickelsberg. Your question is really in two parts: First, can micro amperes be useful? Second, how does one overcome the diode forward voltage drop when trying to rectify the millivolt yields of these devices.
First, microamps are useful as many semiconductors draw only a microamp while in sleep mode and only need to wake up for brief times to sense and transmit data. Lots of energy can be stored during the sleep mode.
Second, tiny voltages can be increased by magnetic induction inside harvester chips. The increased voltages can be used by amazingly sensitive MOSFETs to generate oscillations and further step up the voltages.
Paul Nickelsberg refererred to devices such as the LTC3108-1 and the LTC3588-1. Check out the datasheets and application notices. Truly amazing.
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