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.
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.
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.
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 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).
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.
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?
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)
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.
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.
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.
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.
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?
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?"
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.
> 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.
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.
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?'
[+] [-] jimrandomh|10 years ago|reply
(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.)
[+] [-] imglorp|10 years ago|reply
[+] [-] NikolaeVarius|10 years ago|reply
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.
[+] [-] Dylan16807|10 years ago|reply
[+] [-] gamesbrainiac|10 years ago|reply
[+] [-] Dylan16807|10 years ago|reply
[+] [-] rgarrett88|10 years ago|reply
[+] [-] Eduard|10 years ago|reply
[+] [-] darkmighty|10 years ago|reply
In practice this effect should be small though (for the case of Wi-Fi power).
[+] [-] ProZsolt|10 years ago|reply
[+] [-] livingparadox|10 years ago|reply
[+] [-] olympus|10 years ago|reply
[+] [-] dmd|10 years ago|reply
[+] [-] warfangle|10 years ago|reply
[+] [-] sannee|10 years ago|reply
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)
[+] [-] michaelcampbell|10 years ago|reply
[+] [-] ohaal|10 years ago|reply
[+] [-] rubidium|10 years ago|reply
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.
[+] [-] jacquesm|10 years ago|reply
[+] [-] evook|10 years ago|reply
[+] [-] transfire|10 years ago|reply
[+] [-] daveed|10 years ago|reply
[+] [-] vincentkriek|10 years ago|reply
[+] [-] jacquesm|10 years ago|reply
[+] [-] Arnt|10 years ago|reply
[+] [-] an4rchy|10 years ago|reply
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.
[+] [-] TeMPOraL|10 years ago|reply
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.
[+] [-] Eclyps|10 years ago|reply
[+] [-] frgewut|10 years ago|reply
[+] [-] mtw|10 years ago|reply
[+] [-] egwynn|10 years ago|reply
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?"
[+] [-] TrevorJ|10 years ago|reply
[+] [-] jacquesm|10 years ago|reply
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.
[+] [-] Johnythree|10 years ago|reply
For 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.
[+] [-] anilgulecha|10 years ago|reply
[+] [-] gus_massa|10 years ago|reply
> 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.
[+] [-] thefastlane|10 years ago|reply
after all, one can get cancer (and die from it) from something as 'harmless' as sunlight.
[+] [-] gsteinb88|10 years ago|reply
I dont know whether that meets the standard of convincing you, but it is fantastically well established science.
[+] [-] ultim8k|10 years ago|reply
[+] [-] jacquesm|10 years ago|reply
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?'
[+] [-] Johnythree|10 years ago|reply
Maxwell laid out the maths and Hertz demonstrated the principles many years before Tesla.
[+] [-] dang|10 years ago|reply