A typical RFID chip has nearby a coil that is used to temporarily power up the chip using regular magnetic coupling using a (relatively) low frequency.
That same coil is then used as the antenna (at a much higher frequency) to transfer a little bit of data.
So yes, it's fundamentally different, the article describes energy transfer using radio frequency waves alone.
To expand on that, the difference is (in laymans terms) 'radio waves' versus 'magnetic fields'.
The difference being that in WiFi the magnetic field component is not relevant and in NFC technologies such as RFID it is the main component (the hint is whether the main active component is a coil or an antenna).
There is a close relationship between the two fields governed by Maxwells equations.
In fact they are the same - one is the derivative of the other. So the RFID scanner emits a radio wave; the RFID chip magnetically couples to it to provide a small charge; enough to run the RFID circuitry for a few milliseconds.
At the frequencies and distances at which WiFi normally operates the magnetic component is all but invisible, it's mostly a matter of electric fields.
At lower frequencies the electromagnetic field portion becomes dominant. This is one reason why the 'antenna' inside one of those old fashioned AM receivers is actually a coil with a ferrite core (and conveniently internal to the device), and an FM radio (the A/F have to do with the modulation, not specifically with the frequency but the bands are between 455 and 1600 KHz vs 88-108 MHz) typically uses a rod antenna.
Now you could make an FM radio with a coil for its antenna or an AM radio using a rod but neither would be very efficient.
So it's the small distance and low frequency of RFID technology that drive the choice for magnetic coupling, whereas the high frequency and longer distances of WiFi make the choice for antennas.
AM radio, with its low frequency and enormous power output allows magnetic pick-up at very large distances from the point of origin, this is also why it is not 'line-of-sight' but WiFi is line-of-sight (yes, you can bounce radio waves off objects (such as the moon or the Heavyside layer) but that's another subject entirely).
The higher the frequency of operation the more you'll be looking at properties resembling those of light (which is also a form of electromagnetic radiation).
Not really. Tesla's dream was to set up a resonant field around the globe with a few giant base-stations that one could tap into at will to draw power. For many reasons that was an absolutely un-workable proposal, the major ones being that nature put up a roadblock or two on the way to getting that to work on anything but the smallest scale.
For one there is this thing called a power-law which required the voltages to be significantly higher than those needed to make a system like this work in a laboratory, the other is the breakdown voltage of the atmosphere, which causes any voltage in excess of this to return to ground, frying whatever it finds in its way (think lightning).
It would have made for a hell of a display piece.
Of course this does not stop Tesla groupies from claiming the government suppressed the design.
On another note: regular radio frequency transmitters put out enough power that so called 'crystal radios' can be powered by the transmitter directly. So in a way 'the system works' but the amounts of power that you can draw from it are minute. Tesla claimed that you could run regular industrial machinery from his technology. There is a funny parallel between the Tesla story and uBeam, the dreams are remarkably similar. 'Wouldn't it be a good thing if wireless power with substantial power transfer existed?'
From the paper: "For instance at a distance of 2 feet the battery charging system has 100 µW available compared to 10 µW at 10 feet." The Popular Science and UW Today articles both completely avoid numbers. But the numbers are vital, and if you do a little fermi math, you'll discover that's not enough to compete with watch batteries.
(The first watch battery I found with numbers on it had 240mAh*3V=720mWh, so one such battery could in theory provide 10 µW for 7.2e4 hours or 8 years.)
That's not going to charge your notebook so fast, but that's plenty to power your thermostat, your tv remotes, your burglar alarm sensors, and some of the other lesser IoT bits floating around.
Whether this technology is a winner or not, being able to install a thermostat without having to hire an electrician, shut down power to the room, and knock a hole in your wall would be great. For new construction it's easy. To retrofit older buildings, or to install something in an apartment, the requirements for wall power kinda suck.
It's not enough to power a thermostat. µW is microwatts. WiFi radios need milliwatts. As jimrandomh mentioned, the levels of power here are the same as what a watch battery can provide for eight years. Watches don't even run off of a watch battery for eight years.
> In their proof-of-concept experiments, the team demonstrated that the PoWiFi system could wirelessly power a grayscale, low-power Omnivision VGA camera from 17 feet away, allowing it to store enough energy to capture an image every 35 minutes.
I made a back of the envelope calculations for a similar project ( see https://news.ycombinator.com/item?id=10323565 ) This other projet claim that they can harvest ~30µW, this is very little. For example, it can only blink a led a few times per minute, because a normal led use 30mW=30000µW. Read the complete comments for more details.
I am a serious layman when it comes to this type of stuff, but I swear I remember reading about similar wireless power years ago. I even remember seeing a video of a lightbulb being illuminated without being attached to anything. What makes it this year's game-changing tech? Is it the WiFi aspect?
Wireless transmission has been demonstrated by others before Tesla e.g. Heinrich Hertz. And I mean induction is arguably a form of wireless transmission which has been verified by Faraday in the 1830s. The problem is now as it was then that wireless transmission is governed by the inverse square law and therefore inefficient to the point of being unusable in most real world application.
Hm, I'm curious why this wasn't caught by the HN anti-duplicate. Previously when I've (obliviously) posted an already posted URL, I've been redirected to the comments of the pre-existing URL. The URLs are literally exactly the same.
I talked to two of my friends who wanted to do some research into this. They told me, that in the end, power over WiFi was too inefficient, so in practicality (since they were working with phones), the technology wouldn't actually charge phones up per se, but rather make them lose charge more slowly.
I just skimmed the paper, they achieved 10 microwatts at 10 feet. Yes, micro: this is about a million times less power than a modern smartphone or laptop charges at.
Is efficiency a game-stopper? I would assume the low wifi power levels are the main problem, but that can be solved by cranking up the power. And you can aim the source.
I'm sure you'd be willing to have some amount of inefficiency, considering how low the power requirements of an idle phone are.
Personally, I'd put up with a 50 watt device that only gets a watt to my phone. I'm pretty sure that's doable with a smart transmitter and small receiver.
> considering how low the power requirements of an idle phone are
Don't know about your, but my phone tends to draw ~2.4W when idle with screen on, and I'm pretty sure it stays over 1W even with screen off. That watt would, like 'gamesbrainiac said only make it lose charge more slowly.
And that's just one phone. My household has 4, not counting other mobile devices like tablets and Kindles. Putting a 2% efficient (!) power system to use seems like a crazy and absolutely scary idea. Just multiply that over the number of potential users (~2 billions).
Also, 98% of this energy will have to go somewhere. It probably means heat.
The extra heat and power use is offset by my replacing incandescent bulbs with alternatives, so that's fine with me.
But the only time my phone drains 1 watt with the screen off is when it's doing cellular data transfers with a terrible signal. It has an 8 watt-hour battery and it lasts more than 8 days when I toss it on a shelf to wait for calls.
So if my phone's sitting there using 1/25 of a watt, a 2% efficient maintenance charge only costs 2 watts. And we can do much better than 2%.
A 50 Watt device that gets 1 Watt to your phone is only 2% efficient. That 50 Watt continuous draw translates into 50 * 24 = 1200 Watt-hours daily, or 438 KWh per year. That's a lot of money to keep that one phone charged, multiplied by the number of phones in operation the power waste would be enormous. They recently banned incandescent lights here for being too inefficient, I wonder how a device like this would get a pass if all it does is replace a small piece of wire at enormous cost. And besides all that your phone draws quite a bit more than 1 Watt so it would function as a charge extender rather than a charger.
And that in turn does not take into account the real efficiencies involved, I would be highly surprised if a device like the one you described had even a 2% efficiency.
It wouldn't run 24/7. And the incandescent light ban was very specific, no reason to think devices like this would be instantly banned, and this theoretical worst-case device still no worse than an incandescent bulb.
See my other reply, I don't need anywhere near 1 watt average for my phone.
When I see a report from MIT of a 1 foot receiving coil running at 20% efficiency at 7 feet, I don't see what's unreasonable about a phone receiver beating 2%. I said at the start I wasn't talking about using undirected transmission.
If you crack up the power enought, you get an open microwave oven. (A tipical WiFi router has ~2W and a tipical microwave oven has ~800W, so there is a 400x difference.)
Is it really "game-changing?" You can only use it for low power devices which could also be powered by a small lithium battery for a year. So preventing me from having to change a battery once a year is now game changing?
And not only that, some devices are very hard to reach once they are integrated and their mailfunctioning due to failed batteries would be a show-stopper if the expected lifetime of the device is a multiple of the expected battery life.
I guess we could beam power to them, using a strongly directional signal. Boosting Wi-Fi power to charge devices seems like absolutely mind-boggling waste.
Phased array antenna and some feedback system, so that I can track the device?
Anyway, you obviously have something particular in mind; could you give an example of a device, for which an omnidirectional wireless solution would make sense, factoring in inefficiencies?
The only similar-sounding problem I'm familiar with are long-lived devices mounted underwater or otherwise mounted inside a structure. I've seen wireless power via inductive coupling being used to power such devices, because both the device and battery pack can be sealed off from the environment during manufacturing, and replacing the latter doesn't require any disassembly.
Let's see: where is my 'x' (tools, keys, shoes, glasses etc), data acquisition (temp in any room in the house for instance), various scada applications that now require a large amount of wiring (alarm systems for instance) and so on. It'd be quite the wave of new technology. Imagine, nothing would ever be 'lost' again once you knew it was yours before.
The possibilities for use and abuse are just about endless.
Uh, ok. I see my imagination isn't good today; now that I see them, those examples are pretty obvious. Though I admit I was thinking about devices that eat much more power.
As for "where is my 'x'", I'm actually surprised this isn't a solved problem yet, but I attribute it to the fact that we're still in the early IoT era, when every company wants to lock us in into their bullshit ecosystem of beacons and beacon apps. Though maybe it's changing, now that (again) China is popping out cheap BLE tags.
Disregarding the usual HN snark for media terms ("game-changing") and the usual criticism ("been done before", "won't be effective"), this is actually really cool. If we look at all the innovations in the past year, this is a pretty dang neat one.
They mention Tesla in the opening line of their paper. In short, the biggest innovation they came up with was solving the mismatch of Wifi operation and optimal power transmission. Read the paper; it's quite good stuff.
It is interesting and could be a game changer for the 'internet-of-things'. WiFi is everywhere and just to be able to run a device a couple of seconds per day without having wires attached to it could enable a huge number of applications.
This got me excited about the idea. Like many others my first thought was that it can't be nearly efficient enough to charge my phone, but I hadn't even considered all the little low power sensors I could place around the house that I wouldn't bother with if they all needed to be wired into mains power. Think window break and door lock sensors, etc.
A fun tech I had in my hands once that I haven't seen being use anywhere is turning kinetic energy into power. I've played with a light switch that can generate enough energy from you just pressing them, that they can boot up an internal uC, a radio, and then send a signal. The device had a typical home-automation range of several meters. I've been told that there are versions mounted into window handles, etc.
First tech needs to focus on small distance wireless power. I need to be able to easily and reliably charge my phone wirelessly. Plugging in wires is just straight up old fashioned. Qi is really getting mainstream now but having to position the phone perfectly is not that great. I know of A4WP with NXP as one of the main companies developing tech that can charge everything over the pad, no matter the placement. It also includes stacking. If we can build out this to also be integrated in laptops, lamps and other "put down" devices, I can believe this can evolve into something larger doing it over a bigger distance.
The one thing I can think of is to massively reduce the power consumption of phones. That would go a long way towards making various wireless charging methods (including solar, by the way) much more feasible. Todays phones are very power hungry.
That's because (smart)phones are portable general-purpose computers. I see two ways of reducing power use.
1) Go back to small, low-power screens and physical keypads for data input.
2) Heavily optimize the stack. You could put less power-hungry parts in a smartphone, but then it wouldn't boot up. Even top phones have trouble keeping up with software bloat, being somewhat-usable when you buy them, and barely-usable after a year or two. And let's not talk about the cheap phones, which have barely enough power to run the OS.
I know. I tend to whine about it on HN every now and then :). But this time I meant it from an engineering point of view. Smartphones don't run on ASICs but on general-purpose microcontrollers, they have a general-purpose OS capable of running arbitrary code. And they run staggering amounts of it.
They can't "steal" your electricity. The output from the Wi-Fi is constant, and range limited. If they are getting any power from your signal, its power that you'd be casting off outside your house anyways. Net change in power would be 0.
Well they can "steal" a tiny amount. Wi-Fi signals reflect all over, and by having a large antenna (even beyond your house/room), it absorbs some signals which might reflect/scatter back. Negligible in practice.
Technically, if you have the WiFi password you can have a modern luxury router beam form more signal to you than otherwise. Although my router has multiple 5GHz radios and one 2.4GHz, so it will just move me over to another radio if only one person is leeching. More clients does probably keep more radios on, using more power as well, since otherwise the router can probably sleep more hardware more often. Sort of like a Bluetooth device being discoverable keeps the radio on more, then making it connectable makes it keep the radio on more, etc..
I see you're joking, but I believe it's theoretically possible to extract more power from a pseudorandom stream if you can predict it (that is, if you have a key to decrypt) under certain conditions. It's related to Maxwell's demon: if the signal were exciting a large rod, a flat low energy spectrum would roughly correspond to small thermal fluctuations of the rod, which are bounded by some Carnot-like efficiency. If you can perfectly predict the fluctuations though, you can set up a system of oscillating rods coupled additively to it to absorb it's power such that their sum approximates the Fourier spectrum of the rod. This allows you to extract work from the rod as if it were a sinusoidal signal, which does not have to obey the Carnot limit.
In practice this effect should be small though (for the case of Wi-Fi power).
Well thanks for the compliment. But note that thermodynamics is a delicate subject, that was too simple an argument to be exact. I'm still planning to figure out the details of this kind of problem myself. From my light reading it seems the theories for this subject were fully developed only recently actually, namely non-equilibrium thermodynamics and information-theoretic thermodynamics.
What I mentioned is a natural extension of information-theoretic arguments to computational hardness assumptions; they're the same assumptions that allow safe encryption methods in spite of them being 'broken' in an information-theoretic sense (which doesn't consider computer limitations). Without those limitations only variants of the one-time pad are secure and public key crypto (which relies on integer factorization hardness) is impossible.
It's pretty interesting to me that while we simultaneously demand that companies build everything with power efficiency in mind and embrace environmental consciousness, we take all this power and use it in increasingly inefficient ways.
Seriously, wireless power has existed for over a century, we don't use it because 99% of the power you throw out goes to waste.
In the end, I'm happy with a "five steps forward, one step back" situation where we spend a bit to fight big inefficiencies and then allow some smaller ones for convenience's sake.
Right now it's one step forward, five steps back. Or, with this idea, a hundred steps back. We don't have spare power. Let's talk about it again after we get the planet off coal.
It doesn’t sound like they are talking about boosting the power output from access points, so I guess this is, WLOG, the same question as asking “what are the health implications of wi-fi?” I don’t mean to imply that the answer is ‘none,’ but this new development doesn’t seem to change any of the relevant primary factors (i.e., how much energy the human body absorbs from wi-fi transmitting antennas).
EDIT: Sort of nevermind? I re-read and see that they are telling the access points to send more data, but not to send them above or beyond the antennas’ already-intended power output. So I guess the analogous question is, “what are the health implications of using your wi-fi a lot?"
I wonder if someone experimented in boosting the signal x1000 and see if it creates side-effects in organic matter (of varying conductivity, for example skin, brain neurons etc.)
Also "already-intended power output". If this available, there is motivation for buyers to hack the device and boost significantly the signal -- whereas there's little motivation to hack existing wifi devices
Sunlight is ionizing radiation -- the ultraviolet light is capable of knocking electrons off their atoms, damaging nearby biological systems. 2.4 GHz radio waves cannot do this; absorption just causes local heating (in this case, truly infinitesmal amounts).
I dont know whether that meets the standard of convincing you, but it is fantastically well established science.
This is just about the most inefficient way possible to power an electronic device. The EM radiation radiates out in all direction, and thanks to our little friend the inverse square law, your device's antenna only receives a tiny, miniscule fraction of the original power input. This is going to more than offset installing a few fluorescent light bulbs.
Finally, something that might actually be available to consumers.
To everyone else that is talking about it not happening because of inefficiencies etc, wouldn't the fact that we are also working on ways to generate more renewable energy and working on improving efficiency factor into this equation?
If nothing, any extra improvement in energy efficiency can be considered the overhead needed for wireless power.
It might start of as a luxury more than a necessity.
> wouldn't the fact that we are also working on ways to generate more renewable energy and working on improving efficiency factor into this equation?
One of the most important questions of the early XXI century is whether we'll manage to switch the world from coal to green energy before we cook the planet and without starving big parts of the population for power. One of the talking points is the observation that renewables may not be efficient enough yet and we may not be able to pull it off without going into nuclear ASAP. We have barely enough energy, the third world is rising their living standards to the point they themselves will need a shit ton of power for things like fridges, washing machines and hot showers, and we're thinking of putting all our surplus into ridiculously inefficient things like wireless power?
I think if this idea gets into market now, I'll ask Copernicus to stop this planet and let me get off.
> It might start of as a luxury more than a necessity.
Yes. The kind of luxury like using up $30 000 worth of water in the middle of a drought in California, just because you can. Rightfully pissing everyone else off.
A random Lithium Thionyl Chloride battery (http://www.xenoenergy.com/eng/file/Xeno%20Catalog%20XL-050F_...) for about 2$ can deliver 35uW for 10 years in a ridiculously small package. This well outlasts the lifetime/usefulness of anything which could be potentially connected to it. And even if not, changing a battery every 10 years is not exactly a huge problem.
(Disclaimer: I have only skimmed the paper very quickly)
101 comments
[ 2.8 ms ] story [ 143 ms ] threadFor the power transfer, both generate an electromagnetic field, which is received by an antenna, then converted to DC by a Detector (eg a rectifier).
So the principle is the same, but the details of the technology differs, as does the frequency, type of antenna, etc.
There are many tutorials out there on the web if you care to do some research.
That same coil is then used as the antenna (at a much higher frequency) to transfer a little bit of data.
So yes, it's fundamentally different, the article describes energy transfer using radio frequency waves alone.
In order to harvest power from EM (RF) you need a nantenna, a micro rectifying antenna, aka [1].
[1] https://en.wikipedia.org/wiki/Rectenna
To expand on that, the difference is (in laymans terms) 'radio waves' versus 'magnetic fields'.
The difference being that in WiFi the magnetic field component is not relevant and in NFC technologies such as RFID it is the main component (the hint is whether the main active component is a coil or an antenna).
There is a close relationship between the two fields governed by Maxwells equations.
At lower frequencies the electromagnetic field portion becomes dominant. This is one reason why the 'antenna' inside one of those old fashioned AM receivers is actually a coil with a ferrite core (and conveniently internal to the device), and an FM radio (the A/F have to do with the modulation, not specifically with the frequency but the bands are between 455 and 1600 KHz vs 88-108 MHz) typically uses a rod antenna.
Now you could make an FM radio with a coil for its antenna or an AM radio using a rod but neither would be very efficient.
So it's the small distance and low frequency of RFID technology that drive the choice for magnetic coupling, whereas the high frequency and longer distances of WiFi make the choice for antennas.
AM radio, with its low frequency and enormous power output allows magnetic pick-up at very large distances from the point of origin, this is also why it is not 'line-of-sight' but WiFi is line-of-sight (yes, you can bounce radio waves off objects (such as the moon or the Heavyside layer) but that's another subject entirely).
The higher the frequency of operation the more you'll be looking at properties resembling those of light (which is also a form of electromagnetic radiation).
Maxwell laid out the maths and Hertz demonstrated the principles many years before Tesla.
They are both needed. They shouldn't be compared.
For one there is this thing called a power-law which required the voltages to be significantly higher than those needed to make a system like this work in a laboratory, the other is the breakdown voltage of the atmosphere, which causes any voltage in excess of this to return to ground, frying whatever it finds in its way (think lightning).
It would have made for a hell of a display piece.
Of course this does not stop Tesla groupies from claiming the government suppressed the design.
On another note: regular radio frequency transmitters put out enough power that so called 'crystal radios' can be powered by the transmitter directly. So in a way 'the system works' but the amounts of power that you can draw from it are minute. Tesla claimed that you could run regular industrial machinery from his technology. There is a funny parallel between the Tesla story and uBeam, the dreams are remarkably similar. 'Wouldn't it be a good thing if wireless power with substantial power transfer existed?'
(The first watch battery I found with numbers on it had 240mAh*3V=720mWh, so one such battery could in theory provide 10 µW for 7.2e4 hours or 8 years.)
> In their proof-of-concept experiments, the team demonstrated that the PoWiFi system could wirelessly power a grayscale, low-power Omnivision VGA camera from 17 feet away, allowing it to store enough energy to capture an image every 35 minutes.
I made a back of the envelope calculations for a similar project ( see https://news.ycombinator.com/item?id=10323565 ) This other projet claim that they can harvest ~30µW, this is very little. For example, it can only blink a led a few times per minute, because a normal led use 30mW=30000µW. Read the complete comments for more details.
0. http://www.technologyreview.com/news/413957/intels-wireless-...
Personally, I'd put up with a 50 watt device that only gets a watt to my phone. I'm pretty sure that's doable with a smart transmitter and small receiver.
Don't know about your, but my phone tends to draw ~2.4W when idle with screen on, and I'm pretty sure it stays over 1W even with screen off. That watt would, like 'gamesbrainiac said only make it lose charge more slowly.
And that's just one phone. My household has 4, not counting other mobile devices like tablets and Kindles. Putting a 2% efficient (!) power system to use seems like a crazy and absolutely scary idea. Just multiply that over the number of potential users (~2 billions).
Also, 98% of this energy will have to go somewhere. It probably means heat.
But the only time my phone drains 1 watt with the screen off is when it's doing cellular data transfers with a terrible signal. It has an 8 watt-hour battery and it lasts more than 8 days when I toss it on a shelf to wait for calls.
So if my phone's sitting there using 1/25 of a watt, a 2% efficient maintenance charge only costs 2 watts. And we can do much better than 2%.
And that in turn does not take into account the real efficiencies involved, I would be highly surprised if a device like the one you described had even a 2% efficiency.
See my other reply, I don't need anywhere near 1 watt average for my phone.
When I see a report from MIT of a 1 foot receiving coil running at 20% efficiency at 7 feet, I don't see what's unreasonable about a phone receiver beating 2%. I said at the start I wasn't talking about using undirected transmission.
Anyway, you obviously have something particular in mind; could you give an example of a device, for which an omnidirectional wireless solution would make sense, factoring in inefficiencies?
The only similar-sounding problem I'm familiar with are long-lived devices mounted underwater or otherwise mounted inside a structure. I've seen wireless power via inductive coupling being used to power such devices, because both the device and battery pack can be sealed off from the environment during manufacturing, and replacing the latter doesn't require any disassembly.
The possibilities for use and abuse are just about endless.
As for "where is my 'x'", I'm actually surprised this isn't a solved problem yet, but I attribute it to the fact that we're still in the early IoT era, when every company wants to lock us in into their bullshit ecosystem of beacons and beacon apps. Though maybe it's changing, now that (again) China is popping out cheap BLE tags.
Please? Pretty Please?
Disregarding the usual HN snark for media terms ("game-changing") and the usual criticism ("been done before", "won't be effective"), this is actually really cool. If we look at all the innovations in the past year, this is a pretty dang neat one.
They mention Tesla in the opening line of their paper. In short, the biggest innovation they came up with was solving the mismatch of Wifi operation and optimal power transmission. Read the paper; it's quite good stuff.
A fun tech I had in my hands once that I haven't seen being use anywhere is turning kinetic energy into power. I've played with a light switch that can generate enough energy from you just pressing them, that they can boot up an internal uC, a radio, and then send a signal. The device had a typical home-automation range of several meters. I've been told that there are versions mounted into window handles, etc.
1) Go back to small, low-power screens and physical keypads for data input.
2) Heavily optimize the stack. You could put less power-hungry parts in a smartphone, but then it wouldn't boot up. Even top phones have trouble keeping up with software bloat, being somewhat-usable when you buy them, and barely-usable after a year or two. And let's not talk about the cheap phones, which have barely enough power to run the OS.
Here is one thread about that:
https://lwn.net/Articles/662147/
In practice this effect should be small though (for the case of Wi-Fi power).
What I mentioned is a natural extension of information-theoretic arguments to computational hardness assumptions; they're the same assumptions that allow safe encryption methods in spite of them being 'broken' in an information-theoretic sense (which doesn't consider computer limitations). Without those limitations only variants of the one-time pad are secure and public key crypto (which relies on integer factorization hardness) is impossible.
Some basic readings if you're interested:
https://en.wikipedia.org/wiki/Maxwell%27s_demon#Recent_progr...
https://en.wikipedia.org/wiki/Computational_hardness_assumpt...
I assumed you meant PoE, but just the first paragraph of that document was fkn hilarious. I needed the laugh.
Seriously, wireless power has existed for over a century, we don't use it because 99% of the power you throw out goes to waste.
EDIT: Sort of nevermind? I re-read and see that they are telling the access points to send more data, but not to send them above or beyond the antennas’ already-intended power output. So I guess the analogous question is, “what are the health implications of using your wi-fi a lot?"
Also "already-intended power output". If this available, there is motivation for buyers to hack the device and boost significantly the signal -- whereas there's little motivation to hack existing wifi devices
after all, one can get cancer (and die from it) from something as 'harmless' as sunlight.
I dont know whether that meets the standard of convincing you, but it is fantastically well established science.
To everyone else that is talking about it not happening because of inefficiencies etc, wouldn't the fact that we are also working on ways to generate more renewable energy and working on improving efficiency factor into this equation?
If nothing, any extra improvement in energy efficiency can be considered the overhead needed for wireless power.
It might start of as a luxury more than a necessity.
One of the most important questions of the early XXI century is whether we'll manage to switch the world from coal to green energy before we cook the planet and without starving big parts of the population for power. One of the talking points is the observation that renewables may not be efficient enough yet and we may not be able to pull it off without going into nuclear ASAP. We have barely enough energy, the third world is rising their living standards to the point they themselves will need a shit ton of power for things like fridges, washing machines and hot showers, and we're thinking of putting all our surplus into ridiculously inefficient things like wireless power?
I think if this idea gets into market now, I'll ask Copernicus to stop this planet and let me get off.
> It might start of as a luxury more than a necessity.
Yes. The kind of luxury like using up $30 000 worth of water in the middle of a drought in California, just because you can. Rightfully pissing everyone else off.
They claim 10uW at 3 meters.
A random Lithium Thionyl Chloride battery (http://www.xenoenergy.com/eng/file/Xeno%20Catalog%20XL-050F_...) for about 2$ can deliver 35uW for 10 years in a ridiculously small package. This well outlasts the lifetime/usefulness of anything which could be potentially connected to it. And even if not, changing a battery every 10 years is not exactly a huge problem.
(Disclaimer: I have only skimmed the paper very quickly)