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Wireless Electricity Set to Power Village

freedommatters writes "The UK Sunday Times has a story today about how "Scientists have successfully applied the technology used in microwave ovens to beam electricity without the need for unsightly pylons and overhead cables." A prototype has illuminated a handful of light bulbs and they expect to be able to power a remote village within three years."

40 of 373 comments (clear)

  1. Interesting, but... by UWC · · Score: 5, Funny

    I can feel my brain warming already.

    1. Re:Interesting, but... by Smidge204 · · Score: 3, Funny

      I heard they also managed to rid the village of their nasty pigeon problem and end a local famon. Congrats, gentlemen!

      P.S. I can't even register to read the article. Anyone got a mirror/cache? Nothing on Google yet...
      =Smidge=

    2. Re:Interesting, but... by UWC · · Score: 5, Interesting

      I've been modded Troll? Come on, people that work around microwave antennas do have higher incidences of cancers. The cooking properties of microwaves were discovered by accident.

      It's a genuine concern, and I was just addressing it rather light-heartedly. I've done science fair projects on EMF effects on plants, and I have observed differences in growth patterns; there is an observable effect on biological systems. The risks are real, and there should be more study before they start beaming out microwaves that can power homes.

    3. Re:Interesting, but... by internic · · Score: 3, Insightful

      Well, provided it is in the right part of the spectrum, the human body might have a relatively low absorbtion rate. Certainly, when we think microwaves, we think microwave oven, but that's only a small part of the microwave spectrum.

      The more important point, though is that this may actually cause far less ambient electromagnetic radiation than normal power lines. Ordinary power lines carrying AC current are basically like large antennae (though if properly designed, they are hopefully not very good antennae). They generate radio frequency signals that go off in every direction (actually primarily perpendicular to the lines), which you know if you try to listen to AM radio underneath them. Depending on how they do it, a microwave beam could actually be quite well columnated, so that virtually all energy is sent directly toward the reciever. Certainly, if they used a maser this would be the case, but they probably won't. Remember, too, that they have an interest it making it very well columnated, because that increases the efficienty of the mechanism.

      Since you should be able to columnate the beam pretty well, the main issue would seem to be stuff that might get in the way and scatter the beam: air (obviously), dust, flying animals (like cows from a catapult), and perhaps most importantly, water vapor. If you're worried about getting cooked, think about this: The human body is mostly water, as are most other animal bodies. In order to cook well, a microwave oven must be in the right range of the spectrum to heat water efficiently, which they do (efficient being a relative term). This beam must go through air that has water vapor in it and even rain. It must be designed so all that water is not a problem, meaning it probably must be designed so that it would not really "cook" an animal very well.

      So, really, this beam shouldn't cook things and anyway there should really be very little leakage if designed correctly. I mean, I wouldn't go and stand in it, but it's probably not so dangerous for the reason you bring up. On the other hand, I'm not sure it's really a good idea from an engineering standpoint, and there's the other question of what happens if it gets misalligned or if somehow something does get in the beam that deflects a significant amount of it (like something metal). Anybody ever play SimCity 2000? :) I'm not saying it's not dangerous, just that this EMF stuff is probably not the main problem.

      BTW, as far as I know there is no credible scientific evidence that electromagnetic radiation from power lines causes cancer (or other health effects). There were some studies that suggested it years ago, but last I heard they had all been refuted by newer, more extensive studies. I'm not aware of the scientific credentials of your "science fair experiments", nor am I a biologist, so I can't evaluate that evidence.

      --
      "You call it a new way of thinking; I call it regression to ignorance!" -- Operation Ivy
  2. Wireless Electricity by termos · · Score: 5, Funny

    In the beginning they called it lightning, now they call it Wireless Electricity!

    --
    Note to self: get smarter troll to guard door.
  3. Dangers? by Eight+01 · · Score: 4, Interesting

    I assume the microwave beam would have to be highly focused in order to work. What safegaurds are there to make sure nothing gets in the way of the beam?

    (the article is unavailable without a $55 subscription, maybe it is spelled out in the article?)

    1. Re:Dangers? by Loosewire · · Score: 5, Funny

      What safegaurds are there to make sure nothing gets in the way of the beam?

      I think theyre going to put wires around it which are held up by pylons...

      --
      Slashdot - The one stop shop for procrastination
    2. Re:Dangers? by silverhalide · · Score: 3, Insightful

      It has to be somewhat focused, but it can be focused over a very wide area using large dishes, on the order of 10s of meters. Remember, the power density will decrease at the square of the radius (area=pi*r^2). The end result is an energy level that's only slightly above that of what you get during the day by being outside, but when it gets concentrated by the dish on the receiving end, the power is all there. This was the same idea behind that orbital solar to microwave array -- the receiving dish would be a few hundred meters across so stuff that gets in the way of the beam won't be instantly cooked.

      Say you want to beam 10,000 watts of power somewhere. If you have a 1-foot radius dish, your power per square foot is ~3100 watts. Your typical microwave is somewhere in the order of 500-1000 watts per square foot. You'd get fried if you touch that beam. However, increase your dish size to 25 feet in radius. You're down to 5 watts per square foot. The OSHA safe level of exposure is about .2 watts/square foot, so it's still dangerous, but not to the point of instant death anymore.

      The idea is that converting microwave energy is more efficent than converting solar energy (I forget why, but theoretically solar panels can not be more than 30-50% efficent, no matter what), so this would be quite interesting if it worked out well.

  4. Re:Any Risks? by Bones3D_mac · · Score: 5, Funny

    And kids with four fingers on each hand instead of three. ;-P

    --


    8==8 Bones 8==8
  5. Solar energy by Anonymous Coward · · Score: 4, Funny

    Is a similar concept. Radiation from the sun converted into electricity.

  6. Read that carefully. by Anonymous Coward · · Score: 3, Informative

    He "believes that it is likely." That doesn't mean he had any empirical evidence whatsoever.

    Repeated controlled studies have shown that there is no connection between power lines and cancers except in the sense that neighborhoods near power lines tend to be of poorer people who have a higher incidence of cancer due to lifestyles (i.e., they smoke a lot).

    1. Re:Read that carefully. by Fishstick · · Score: 3, Interesting

      Heh, buddy of mine living out on some farmland with some HV powerlines running through it can attest to that.

      He built a 30'x30' pole barn out on his property to use as a workshop for his hobby (restoring 50's & 60's cars). He shopped around auctions and such for months to outfit his shop (shelves, tools, hoist, etc) and got hold of some nice big flourescent shop lights.

      When he switches off the lights at night the bulbs still glow. Usually they are pretty dim, but apparently atmospheric conditions affect this and some nights they glow fairly bright.

      --

      There is much cruelty in the universe, John.
      Yeah, we seem to have the tour map.

    2. Re:Read that carefully. by kavau · · Score: 3, Informative
      We are talking about microwave radiation here, not about power lines! The radiation emitted from power lines is in the 50-Hz range, while microwaves are in the GHz (1E9 Hz) range. Naturally, the higher the frequency, the more damage the radiation can do (this is elementary quantum mechanics: the energy of a photon is given by planck's constant times the frequency). Comparing microwaves to power lines therefore does not make sense at all.

      I recall reading, a while back, an article about a "microwave cannon" planned by the military. Supposedly it's effect is to raise the temperature of the enemy soldiers' brain tissue by a few degrees, which renders them unconcious. I could imagine that the energy needed to power a light bulb could have a similar effect on your brain, albeit weaker. But it might still make you feel uncoordinated and "feverish".

      On the other hand, I'd love to have a microwave power supply for my laptop :-)

  7. Can anyone explain the economics of .... by adzoox · · Score: 5, Interesting
    Can anyone explain the economics of the current line/poll implementation?

    Why aren't lines buried to be less obtrusive, better insulated, and non-problematic in ice storms?

    Recently, in February, South Carolina, my home state, had a very bad ice storm. It was called "the worst on record". Why was it called that? It wasn't really the worst. Duke Power, our service provider, has failed to maintain the lines in there above ground condition. Lots of trees had grown through power even over and around some lines. Then there was the typical stupid driver who ran into a number of poles all over the area.

    I was without power for 4 days. Luckily, I had an UPS unit from a server that has 40 hours and I use a laptop as my main computer. It powered everything in my place including a small heater for a while.

    To be on topic, eventhough the above is too: I don't think we should be pushing conventional power to 3rd world countries. With this implementation of "beaming power" - power still has to be generated at a plant with with most likely a non renewable resource. Why can't we give these same people advanced windmills and solar cells? (Then teach them maintenance) That makes so much more sense. I see the costs of even an experiment; very high. Also, I think Microwaves at a ground level would interfere with radio communications at the points below the transmission.

    --
    Yell & scream & rant & rave... it's no use... you need a shaaaave ~ Bugs Bunny
  8. Interesting, but dangerous? by tuxlove · · Score: 5, Interesting

    Tesla was pushing "broadcast power". It was doomed to failure because of the problems inherent in charging the atmosphere. What they are proposing here is quite different. Haven't read the article, but I'm slightly familiar with the concept here. You simply convert electricity into microwave radiation and transmit it in a tight beam to a receiving station. No problem, old hat. Doing it on this scale might be a challenge, though. On the other end you have a receiver that converts that radiation back to usable electricity. Quite a different problem. I suspect that's what they're pioneering here. I think it has actually been done before, but not in any practical way. Powering a few lightbulbs isn't exactly practical either, but it would be if you could power a small town, or even just several buildings.

    But keep out of the way of the beam!! I have to wonder about the environmental damage of birds/insects flying through it and getting cooked.

    I remember reading about a proposal to send power to the earth this way. By having a massive solar cell array in space transmitting microwaves to a giant receiver on earth, you could gather lots of energy. The thought of this thing getting off track and aiming at, say, NYC seems a little too scary, though.

    1. Re:Interesting, but dangerous? by Maudib · · Score: 4, Funny

      I remember reading about a proposal to send power to the earth this way. By having a massive solar cell array in space transmitting microwaves to a giant receiver on earth, you could gather lots of energy.

      Yeah, the "Proposal" was called Sim City 3000 as I recall. I also recall the "proposal" included random attacks by godzilla.

    2. Re:Interesting, but dangerous? by deglr6328 · · Score: 4, Interesting

      score 4 insightful? I don't know who's more clueless, the poster or the moderators. I swear the quickest way to spot a conspiracy theorist moron on slashdot is to look for a post saying essentially that 'no it wasn't unfeasible schemes due to the laws of physics, it was the power companies and the MAN who kept him down!!' or some such.
      Please get a clue. The reason it was impossible is becasue of the inverse square law of radiating electromagnetic radiation. In other words if you double your distance from the power generating station you will only recieve 1/4th the power (for non directed beams, which Tesla's station was) using the same power gathering area(antenna size). You would have to generate unbelieveably intense EM fields at the transmission station just to light a light bulb a mile away! It would be so wasteful a means of power transmission that a mere few percent at most of the generated electricity would ever be used by the customer.
      By the way your other non-sequitor comment about the "Tunduska" (sic. Tunguska) event belies your ignorance as well, everyone knows by now that it almost certainly was either a comet or asteroid.

      --
      - "Hear that?! The percolations are imminent! Cease your ingress!"
  9. Rectenna?! by psyconaut · · Score: 4, Funny

    "Microwaves for the electricity are targeted via antennas and reflectors at a ?rectenna? (from the words rectifier and antenna), "

    I'm glad they defined a rectenna for me...I thought it was an antenna you stuck up your ass! ;-)

    -psy

  10. More details on this site by 2sleep2type · · Score: 4, Informative

    This is a more detailed publication pdf file

  11. Tesla Reference in... by gaudior · · Score: 4, Funny

    Five, Four, Three, Two, One....

  12. Mirror of Story by Anonymous Coward · · Score: 5, Informative

    Electricity can be beamed through the air without a pylon in sight
    Roger Dobson

    SCIENTISTS have successfully applied the technology used in microwave ovens to beam electricity without the need for unsightly pylons and overhead cables.
    The power is fired through the air in the form of microwaves and collected in special antennas that reconvert the microwaves into electricity.

    A prototype of the wireless power technology has shown the system works and a full-scale version is now being built to make a remote village on the French-governed island of Réunion in the Indian Ocean the world's first microwave-powered community.

    According to a report to be published this week, the system is a cheaper way than either solar energy or local generators of supplying remote areas not connected to a grid.

    "(Electricity) network distribution is effective at the centre but the costs increase quickly when you get to the edge," said Dr Guy Pignolet of CNES, the French space agency, which has conducted the trials.

    "Extending it to remote areas is very costly, but with microwave technology you do not have those costs. You also do not have pylons, which you may not want in sensitive areas."

    The technology works by converting direct current (DC) electricity into microwave power at the transmitting end in the same way that switching on a microwave oven converts electricity into waves using a device called a magnetron. Residents are unlikely to be baked as the frequencies in the two applications are entirely different.

    Microwaves for the electricity are targeted via antennas and reflectors at a "rectenna" (from the words rectifier and antenna), which absorbs the microwave energy from the beam and converts it back into DC power with diodes.

    In Grand-Bassin on Réunion, which lies at the bottom of a 3,000ft canyon with no road access, electricity is currently provided by solar panels placed on the roofs of the houses. But increasing the amount of electricity solely by using the panels is difficult because of the amount of surface area needed. It is also expensive.

    The researchers have successfully produced a field prototype to illuminate a handful of light bulbs. A second prototype is being finalised and will be in operation in about 10 months, while the whole project to supply the village with power is scheduled to be completed within three years.

    Additional reporting: Nick Speed

    1. Re:Mirror of Story by GigsVT · · Score: 3, Informative

      They've probably demonstrated this from within the near field of the transmitter, something that isn't difficult.

      I have a feeling we won't hear any more about this "technology" (which is 50 years old). It's probably a borderline scam artist fishing for VC money.

      --
      I've had enough abrasive sigs. Kittens are cute and fuzzy.
  13. Not totally related but amusing by worst_name_ever · · Score: 4, Funny
    We once had a customer at the electronics design place I work for ask for a product with a size that was physically too small to contain the battery that they wanted to use. When informed of this, they asked, "well, couldn't you put the battery somewhere else and send power through Bluetooth?" Needless to say, we all laughed.

    But really, now that I think of it, I should have told them that it would have worked if they'd implemented RFC 3251 over 802.11! ;)

    --

    In Soviet Rush, today's Tom Sawyer gets high on you.
  14. Re:Tumor-Tastic by T-Kir · · Score: 3, Funny

    Well there is plenty of radiation going around from mobile phone masts, which are either being built next to schools or hidden in the price towers of petrol stations. There was a local news report about a village where they've had a mobile phone mast for the past 10 years and the amount of cancer cases has gone up significantly... one woman who has had major problems takes the news team through her house with a radiation detector and the thing buzzes away even more when she goes upstairs! I can't find a link on the web but here is a start

    Back to the mobile power, it always makes me think of SimCity 2000 with the Microwave powerplants and the warning of a misdirected beam hitting your city instead of the plant.

    --
    Are you local? There's nothing for you here!
  15. Re:Tesla's Legacy by Anonymous Coward · · Score: 3, Interesting

    Anyone know how useful these patents are?

    645,576 Sept. 2, 1897 System of Transmission of Electrical Energy
    649,621 Sept. 2, 1897 Apparatus for Transmission of Electrical Energy
    685,957 Apparatus for the Utilization of Radiant Energy
    685,958 Method of Utilizing of Radiant Energy
    1,119,732 Jan. 18, 1902 Apparatus for Transmitting Electrical Energy

  16. Documentation, as requested by nurb432 · · Score: 3, Informative

    "The life and times of Nikola Tesla" ISBN 1-55972-329-7

    Read that, it has all the information you need, and documented sources.

    I have also seen examples of his coils in real life creating the effect of 'wireless power transfer'. Its simple high frequency air-core transformer theory really.. its not complex in our age.. it was totally amazing in his..

    Figures you would post under anonymous, cant hide behind facts.

    --
    ---- Booth was a patriot ----
  17. Radio by ArchieBunker · · Score: 3, Interesting

    Tesla won the patent for radio because his plans included both a transmitter and receiver, while Marconi only had a transmitter. Transmit all you want but its worthless without a way to capture the transmissions.

    --
    Only the State obtains its revenue by coercion. - Murray Rothbard
  18. Re:Tesla's Legacy by Tomato3 · · Score: 4, Interesting

    "The scientific man does not aim at an immediate result. He does not expect that his advanced ideas will be readily taken up. His work is like that of the planter - for the future. His duty is to lay the foundation for those who are to come, and point the way."
    -Nikola Tesla

    --
    Beware of he who would deny you access to information, for in his heart he dreams himself your master. -Commissioner Lal
  19. For those who didn't read the article... by Hanzie · · Score: 3, Informative

    login with slashdot/slashdot

    Then post.

    This isn't a case of general broadcast, it's point to point.

    They also claim that, since it's different frequencies, that they "won't bake the residents." Though I'm not sure about it, I'd think anybody who actually is in the middle of such a project and says such a thing probably know's what they're talking about. (Though obviously spectacular exceptions exist.)

    In any case, if they start baking residents, passersby or wildlife, I assume lawsuits will fly. I also assume that somebody has consulted tech-aware lawyers already regarding this issue.

    --
    ********* sig: If you don't like the law, get filthy stinking rich, and buy a better one.
  20. All radiation silliness aside.... by OwnerOfWhinyCat · · Score: 4, Insightful

    Infrastructure is an evolutionary process. It's the fact that we have cheaply available power that sets up the conditions by which we produce cool power hungry gadgets. It's the fact that it can be delivered in large amperages to densely packed locations that makes it so everyone in your apartment building can watch a separate big-screen T.V. at the same time.

    Thus, it is completely unfair to knock this technology because it will never be a match for a burly copper cable.

    Imagine what it's like to live in a remote village that has no power available. First off, this almost always means no phones, land-line or cell. It also usually means that the families that are better off run their generators during certain hours of the day, producing noise and fumes, and enough power to get some work done, but they don't run them day and night. Four hours a day at a few hundred watts of power and no phones would significantly change most of our lives.

    The most important thing microwave power could provide would be to enable a low power cell-site to give continuous operation at low cost. Unobstructed, 10 five watt channels would provide good communication for a few thousand people if used frugally (the way everybody did when roaming was $2 per minute). The people in the town could set up cellular fixed station adapters and wire their homes with copper and have a cheap phone in every room. With rechargeable batteries that charging up during the generator "power hours" they could have hours worth of night of phone calls to everyone else in the village, and more importantly to people outside the village with which they might want to do business. Even people without generator access could buy a pocket phone with two batteries and leave one at the neighbor's house charging while the other stayed in their pocket to give them emergency contact capability.

    In regularly overcast areas (I live in one) the day often has enough light to see by, but not enough to read by. Just one 30 halogen bulb produces better reading light than any oil lamp I've ever used. Without light to read by, or TV of course, nights around here could get pretty boring, and homework pretty hard to do.

    Since this is "a remote village" that means it's likely there are some uninhabited outskirts between it and the nearest big city. So between your microwave distribution points there wouldn't have to be any people at all. They could also aim the beam such that overspill wasn't directed toward the town.

    I don't like the idea of radiation burns any more than the next person, but if done correctly there would be little danger. This could be a tremendous asset to people living off the grid, and to tower-climbing children wanting to roast hot dogs. :)

  21. Hum by f97tosc · · Score: 4, Insightful

    In order for this to work, they would have to make the beam extremely focused from transmitted to receiver.

    If they don't do this, not only do they get the heatlh issues you point out, but the system simply won't work in practice.

    All energy that is not captured by the receiver is lost.

    Tor

    1. Re:Hum by tunabomber · · Score: 4, Interesting

      In order for this to work, they would have to make the beam extremely focused from transmitted to receiver.

      The article isn't very specific, but I would guess that they would have either used a parabolic reflector or a maser to do this.
      A parabolic reflector could focus the microwaves into a beam, much like that of a flashlight, but some energy would be lost to diffraction. A maser is similar to a laser, only it emits a coherant beam of microwaves that would travel from transmitter to receiver with minimum energy loss.

      --

      pi = 3.141592653589793helpimtrappedinauniversefactory71 ...
  22. Could you cite your source? by MarkusQ · · Score: 5, Interesting

    Come on, people that work around microwave antennas do have higher incidences of cancers.

    I am aware of cancer clusters around some high voltage power lines that was traced to chemical compounds (used in the insulators, IIRC), but no responsible studies that link microwave antennas to cancer. (I use the qualification "responsible" because I have seen "studies" by the cell-phones-are-killing-us wackos that make the claim, but their methods were so flawed it was funny.)

    -- MarkusQ

  23. What does that mean? by coupland · · Score: 5, Insightful

    What the hell is "the technology used in microwave ovens?!?" Buttons? Electricity? Light bulbs? Microwaves?? Do journalists even read their own inane statements? Hey, I just harnessed the technology used in keyboards to send an e-mail, it's revolutionary...

  24. Re:Tumor-Tastic by Idarubicin · · Score: 3, Insightful
    There was a local news report about a village where they've had a mobile phone mast for the past 10 years and the amount of cancer cases has gone up significantly...

    A 'village'...how many people is that? Two or three hundred? 'Significantly'--what is meant by that? Here's a hypothetical case. Question: If between 1980 and 1990 there are four cases of cancer, and between 1990 and 2000 there are eight cases in this little village, what does that tell us?

    Answer: Nothing. The newsmedia will be on their hind legs shouting that the cancer rate has doubled! The village statistician might tell you that the sample is too small--it's just as likely that there will only be two more cases between 2000 and 2010. The epidemiologist down the street will note that a lot of people have moved into the new retirement community, and that older people are more likely to develop cancers. The local toxicologist (it's a village full of professionals) could observe that a refinery closed upstream about twenty years ago, and is probably leaching mutagenic nasties into the creek. The town dietitian sees that McDonald's opened a new restaurant in the village about fifteen years ago, and wonders.

    So what's the solution? Blame the cell tower. Why? Because you can see it. It sticks up. It's obvious. It's easy. The drunk drops his keys in a dark alley. He immediately steps out of the alley and begins to carefully scrutinize the gound around a nearby street light. Why? Because they light is better over there.

    You've supplied us with an anecdotal report of an anecdotal report. Recent large-scale studies of EMFs show no link between moderate electric or magnetic fields (comparable to those associated with living near power lines or the use of cellular phones) and cancer. Gee.

    --
    ~Idarubicin
  25. No solid scientific evidence by spineboy · · Score: 5, Informative

    That old power line thing was disputed a while ago - mostly just a media fad. I was working at the NIH with one of the guys who first noticed the magnetic field effect on celles in culture.
    It has never been shown to cause any cancers.
    Radiat Res 2000 May;153(5 Pt 2):627-36 Related Articles,
    Leukemia and lymphoma incidence in rodents exposed to low-frequency magnetic fields.
    Boorman GA, Rafferty CN, Ward JM, Sills RC.

    The PCB coolants used in/around many of those power stations is another subject.

    Just to help hammer the nail home, there are many FDA approved devices that use magnetic or pulsed elctronic field devices to aid in bone healing. No reports of cancer yet in these either. Some increased cell growth yes, but cancer no.

    This kinda crap science is usually perpetuated by the media and lawyers hoping to make a few bucks (well, usually they want a few million).
    Bah!

    --
    ..........FULL STOP.
  26. Old tech and clueless comments by jayrtfm · · Score: 4, Insightful
    This is basically a terrestrial version of beamed power from Solar Power Satallites, a concept that's been studied since 1968.

    The microwave systems that SSI have studied are basically like a UHF tv station transmitter (sans Weird Al).

    Birds don't cook, people don't mutate, airplanes won't crash from this. Since this is a line of sight system, the range is probably less than 20 miles. Even so, it will make a terrific demo that proves the practicality of powering cities from SPS.

  27. I thought that was the point . . . by Idou · · Score: 3, Interesting

    We aren't certain about the effects of EMF exposure, so we are going to find some poor village without electricity and offer them electricity through microwaves. The expirement can pay for itself through the utility fees we charge the villagers.

    Boy, did I wake up cranky today . . .

    --
    Sdelat' Ameriku velikoy Snova!
  28. Re:Tumor-Tastic by TopShelf · · Score: 5, Funny

    But on the bright side, all you have to do is lift a hot dog on a stick up into the air, and you've got lunch in under 2 minutes!

    --
    Stop by my site where I write about ERP systems & more
  29. How efficient is a "rectenna" !? by fygment · · Score: 5, Insightful

    Besides wondering what marketing genius came up with that name, just what kind of efficiency can you get with this principle. The losses are at:

    a) conversion from AC to DC
    b) conversion for transmission
    c) losses due to Tx antenna efficiency
    d) losses during transmission incl. energy lost toasting birds and folk getting in the way of the Tx beam
    e) losses due to Rx antenna efficiency
    f) losses during rectification to DC
    g) losses during conversion to work (here light), more if you go to storage (battery) and back again.

    Those add up pretty darn quick. Plus power received varies as an inverse square law of the distance from the transmitting site. Not very efficient. Seems like strictly a niche application.

    --
    "Consensus" in science is _always_ a political construct.