Sounds like a good way....
...to get 'po' WiFi.
The Internet of Things world could power a lot of things with WiFi signals, if only access points broadcast all the time instead of when they've got something to say. There's a bucket of research into scavenging ambient signals to power junk stuff things, and WiFi is a popular energy source, but it's intermittent. As the …
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what's the energy efficiency of this set-up?
It was noted in the article that power over WiFi is inherently inefficient. This study is a proof of concept, at best. Perhaps the next steps ought to be to find more efficient ways of implementing it and defining situations in which using it makes more sense than the alternatives (if these actually exist). I would think that it would be better to power devices from battery and charge the battery as power can be harvested from WiFi (or from other sources) rather than to power directly from WiFi.
"Perhaps the next steps ought to be to find more efficient ways of implementing it and defining situations in which using it makes more sense... "
Here are both ways:
1) Pop your iot shit into a big foil balloon and poke your router's aerial in too.
2) Fabricate a big fractal mesh aerial for your iot shit and wrap it around your router.
As everyone else is pointing out: It's an exceptionally shit suggestion.
Sounds like an effective way to burn out some post-warranty networking tat though. I wonder which firm sponsored the study...
Or just pop your IoT shit into either of the above containers, take it to the nearest electrical recycling point and dump it there and be done with it?
Either that or along with this go out and buy a nice hefty club to fend off all your pissed-off neighbours whose wifi no longer works as it's suddenly flooded by all your noise.
OK, let's get one thing straight from the start: This will always be an inefficient way to power a device. You are sending out a signal in all directions, wasting most of the power, and receiving a fraction of it somewhere.
However, when the router is transmitting for other purposes (e.g. what it was designed for, providing a WiFi signal)), this power would be lost anyway. Therefore it is an improvement to capture and use it. The problem comes when it is being powered outside it's normal use.
Now, in a normal domestic setting, the transmitter probably remains off for the vast majority of the time. So this scheme would likely be very inefficient. However, think of busier places, like office blocks, retail premises, transport hubs, distribution centres. All of these tend to have WiFi, and they will be running a hell of a lot more than your average domestic set up. The overall efficiency of it as a power distribution system will increase a hell of a lot. I don't have numbers, but I suspect that in a 24/7 operation with WiFi "constantly" in use and many small sensors dotted around, it could exceed 100% (i.e. most of the power is captured from wasted power in WiFi signals transmitted anyway).
"but the places you mention will mostly never fall below the traffic treshold mentioned in the article."
But what about the odd occasion when they do? Would they want the sensors to stop working just because, say, the fire alarm goes off in the warehouse or the airport has had to be cleared out because of a bomb scare? It may sound trivial in comparison to a bomb scare, but that tiny extra use of power over a short term stops there being a gap in the data.
I agree, in the vast majority of cases this is a waste of time and energy. But in a few niche cases, a simple modification to existing tech could prove incredibly useful, as well as efficient.
This is High School Science day stuff to impress parents. It's not Boffin stuff or real engineering. A small solar panel like on cheap garden lights will get more waste energy, and sensible micro gadgets can run for about 5 years on 2 x Alkaline AA cells. Some NiMH with the low self discharge of primary Lithium coins or Alkaline would be better research. The Eneloop type are not good enough.
Just because something might just be possible does not make it a good idea.
Studies show that with the right diet cows can be persuaded to fart even more methane. Experts suspect that with perhaps as few as 50 to 100 super farter cows in the car boot along with enough food for the journey cars could be adapted to avoid using fossil fuel. The admit that the size and consequent weight increases may adversely affect the car's handling but with a bit of further development and wider roads, they expect the problems to be overcome.
Or even more friendly, the Poo Powered Bus (and no, it is actually real, albeit not quite as "directly" powered as the pictures on it suggest).
Studies show that with the right d̶i̶e̶t̶ grant funding source c̶o̶w̶s̶ scientists can be persuaded to fart even more m̶e̶t̶h̶a̶n̶e̶ hot air. Experts suspect that with perhaps as few as 50 to 100 super farter ̶c̶o̶w̶s̶ scientists ̶i̶n̶ ̶t̶h̶e̶ ̶c̶a̶r̶ ̶b̶o̶o̶t̶ being funded, along with enough f̶o̶o̶d̶ ̶f̶o̶r̶ ̶t̶h̶e̶ ̶j̶o̶u̶r̶n̶e̶y̶ bribes for the standards committee ̶c̶a̶r̶s̶ ̶c̶o̶u̶l̶d̶ ̶b̶e̶ ̶a̶d̶a̶p̶t̶e̶d̶ ̶t̶o̶ ̶a̶v̶o̶i̶d̶ ̶u̶s̶i̶n̶g̶ ̶f̶o̶s̶s̶i̶l̶ ̶f̶u̶e̶l̶ any old bollocks could get accepted as a standard. They admit that the ̶s̶i̶z̶e̶ ̶a̶n̶d̶ ̶c̶o̶n̶s̶e̶q̶u̶e̶n̶t̶ ̶w̶e̶i̶g̶h̶t̶ ̶i̶n̶c̶r̶e̶a̶s̶e̶s̶ stupidity of the idea may adversely affect the c̶a̶r̶'̶s̶ ̶h̶a̶n̶d̶l̶i̶n̶g̶ performance of your future devices but ̶w̶i̶t̶h̶ ̶a̶ ̶b̶i̶t̶ ̶o̶f̶ ̶f̶u̶r̶t̶h̶e̶r̶ ̶d̶e̶v̶e̶l̶o̶p̶m̶e̶n̶t̶ ̶a̶n̶d̶ ̶w̶i̶d̶e̶r̶ ̶r̶o̶a̶d̶s̶,̶ ̶t̶h̶e̶y̶ ̶e̶x̶p̶e̶c̶t̶ ̶t̶h̶e̶ ̶p̶r̶o̶b̶l̶e̶m̶s̶ ̶t̶o̶ ̶b̶e̶ ̶o̶v̶e̶r̶c̶o̶m̶e̶ they don't really give a shit.
Well you did show a picture of a nice Tesla coil.
Back in the early-mid 80s some techies in Texas Instruments supposedly stuck a Tesla coil circuit onto a chip. The thing turned out to be a broad band RF receiver and could rather nicely suck small amounts of usable power out of ambient EM noise. Which is probably why since then I've never been able to find anything more about it (hunting for my tinfoil hat to protect the conspiracy theories).
It was published in Science weekly in the above time period. Hopefully not an April 1 issue.
No, really. We're heading straight for an energy crises and they want to find a way to pump yet more energy than we already are to power - in the least possible efficient way - stuff that is patently useless and possibly privacy-invading.
I do hope these jokers are getting a good salary out of the moron paying for this "research".
There's an apocryphal tale of one enterprising individual living near Brookmans Park Radio Transmitter who had wrapped transformer wire around their loft to tap the signal. So successfully that this was discovered as a result of the radio-dead shadow it was casting.
I expect there's similar tales surrounding every other transmitters but I do know BBC TV used to get them to lower its power when it interfered with outside broadcasts in the area.
The researchers reckon they've powered temperature and camera sensors at 20 feet and 17 feet respectively. Coin-cell batteries can be charged at greater distances.
I believe you can actually buy power cables in 20-foot lengths (maybe even more if you go to a specialist shop). As the WiFi router is presumably connected to a power source of its own, it might just be possible, with the right technology, to share the power between both devices. Further research is needed.
You might be able to harvest even more power from the RFI that the average Compact Fluorescent bulb emits. For those naysayers who point out that outdoors or during the day those noise sources may not be available, I hear there is a rather large H->He fusion reactor broadcasting energy available in those circumstances.
Only half in jest. I recently replaced a ceiling lamp fixture and saw that it was rated 60W max incandescent, 18W max CFL. I assume that has to do with either cooling or nasty non-visible emissions from the lowest bidder "ballast".
back in the 1970's the Royal Navy's airbase at Yeovilton was home to the NATO joint electronic warfare squadron - basically a bunch of tracked 20' containers stuffed full of electronic gear. At the time there were a lot of strange stories in the local press about radio being heard from local fridges and cookers - and in some cases from the stand of naval comms antennae at nearby Somerton (part of the Portishead Radio system). Apparently these would pick up and broadcast quite loudly BBC Radio given the correct weather conditions