5 ms·

Sure, as long as it's right in the focus of the beam. If that means putting it in one particular spot, is there any benefit over inductive chargers? That method

by szczys 11y ago

Sure, as long as it's right in the focus of the beam. If that means putting it in one particular spot, is there any benefit over inductive chargers? That method would be faster and more efficient.

knodi123 11y ago
Hehe, well, ubeam says it literally has mechanical aiming mechanisms that locate power recipients and focus directly at them. So, practical and maintenance limitations aside, they have definitely answered that criticism.
- GeorgeOu 11y ago
  If you read the FAQ on eevblog, 100 KHz frequency ultrasound will lose 90% of its energy at 2 meter range or just over 6 feet. That energy goes to heating the air that the sound travels through. Then you have to contend with any orientation offset. If the receiver is off by 90 degrees or more, there is zero energy received. If your hand blocks half the surface area, that's another 50% power loss. If you boost the power above 140 dB safety limit, you can burn your hands or cause other problems. At 140 dB at 2 meters, the theoretical best case with 100% efficiency transmitter and receiver will deliver 0.85 watts. You obviously lose even more than that. http://www.eevblog.com/forum/projects/the-ubeam-faq/ http://www.eevblog.com/forum/projects/the-ubeam-faq/
ChrisGammell 11y ago
Also, not to be the old guy...cables don't bug me THAT much. I'll take USB C and charge with 100W instead, thank you very much!
- darkmighty 11y ago
  I'm with you. Investors/companies have to get into their heads that power transmission will never be as easy as data transmission. There's no power Wi-Fi, only some crude expensive approximations over mediocre distances with mediocre power levels. We could instead focus on improving cables (and confined power in general) -- have them available everywhere, retractable, higher power. There's hardly any physical limit to confined power transmission; if you look at trends into the future you might expect device power consumption to actually rise a little, only furthering the divide. Cables are just so more elegant. Part of the problem not discussed here is the 'Absorption conflict': for efficient power transmission you need materials that are able to absorb very well the given form of power; but at the same time you want nothing to interact in the path of the unconfined flux. This can only be dealt with up to a point, since our everyday objects' configuration and atomic composition are not so different from the composition of a receiver. This applies to all technologies: even for resonant EM power transfer you are relying on a specific conductor geometry; thankfully there's no strong conductor in our bodies, but you will have to deal with metal parts everywhere. Wireless information gets around this kind of limitation because power ceases to important for the capacity of a channel [1] past a threshold (roughly when the signal PSD equals the noise PSD), while the determining factor is bandwidth. So you just use a few Ghz+ radiation and you have enormous bandwidth available; once that becomes insufficient we can move to Thz+ light; and so on without much environmental concerns (just medium concerns -- atmosphere gets opaque), since power levels will be kept constant or lower. [1] https://en.wikipedia.org/wiki/Channel_capacity#Example_application https://en.wikipedia.org/wiki/Channel_capacity#Example_appli...
  - Retric 11y ago
    I can think of a single highly popular counter example which used 100% wireless power over several miles. https://en.m.wikipedia.org/wiki/Crystal_radio https://en.m.wikipedia.org/wiki/Crystal_radio RFID are often a short range example of the same idea. So, it's less that wireless power is useless As it is modern devices needing lots of power.
    - darkmighty 11y ago
      Crystal radio is an interesting concept -- but note I didn't claim it was impossible, just highly inefficient and with mediocre power/range (I couldn't find sources, but apparently it's typically 40uW with a ~1m? antenna). Remember that's for a (usually) 50kW station -- that's 1e-9 efficiency, or 0.0000001%. Realistically I'd expect you to be able scale this to 10k's receivers to up to about 0.001%. It's not realistic to increase this power significantly due to health/electronics concerns for persons living close to the source and massive consumption -- bringing the power near a single station to 4W would consume 5GW, about 1% of total US power consumption! Interesting to imagine a system with sightly higher frequencies (20Mhz?) dedicated to power transmission. It'd essentially be a hugely wasteful system (and expensive with high powered antennas everywhere to mitigate invsq law) which however might be able to power ultra low power sensors and gadgets. Some clever phase distribution (pseudorandom modulation should do it) system would allow location with ~15m accuracy too (even working indoors, although building refraction and reflections might be a little troublesome).
      - deleted 11y ago
        [deleted]

by szczys 11y ago

Sure, as long as it's right in the focus of the beam. If that means putting it in one particular spot, is there any benefit over inductive chargers? That method would be faster and more efficient.

knodi123 11y ago

Hehe, well, ubeam says it literally has mechanical aiming mechanisms that locate power recipients and focus directly at them. So, practical and maintenance limitations aside, they have definitely answered that criticism.

GeorgeOu 11y ago
If you read the FAQ on eevblog, 100 KHz frequency ultrasound will lose 90% of its energy at 2 meter range or just over 6 feet. That energy goes to heating the air that the sound travels through. Then you have to contend with any orientation offset. If the receiver is off by 90 degrees or more, there is zero energy received. If your hand blocks half the surface area, that's another 50% power loss. If you boost the power above 140 dB safety limit, you can burn your hands or cause other problems. At 140 dB at 2 meters, the theoretical best case with 100% efficiency transmitter and receiver will deliver 0.85 watts. You obviously lose even more than that. http://www.eevblog.com/forum/projects/the-ubeam-faq/ http://www.eevblog.com/forum/projects/the-ubeam-faq/

ChrisGammell 11y ago

Also, not to be the old guy...cables don't bug me THAT much. I'll take USB C and charge with 100W instead, thank you very much!

darkmighty 11y ago
I'm with you. Investors/companies have to get into their heads that power transmission will never be as easy as data transmission. There's no power Wi-Fi, only some crude expensive approximations over mediocre distances with mediocre power levels. We could instead focus on improving cables (and confined power in general) -- have them available everywhere, retractable, higher power. There's hardly any physical limit to confined power transmission; if you look at trends into the future you might expect device power consumption to actually rise a little, only furthering the divide. Cables are just so more elegant. Part of the problem not discussed here is the 'Absorption conflict': for efficient power transmission you need materials that are able to absorb very well the given form of power; but at the same time you want nothing to interact in the path of the unconfined flux. This can only be dealt with up to a point, since our everyday objects' configuration and atomic composition are not so different from the composition of a receiver. This applies to all technologies: even for resonant EM power transfer you are relying on a specific conductor geometry; thankfully there's no strong conductor in our bodies, but you will have to deal with metal parts everywhere. Wireless information gets around this kind of limitation because power ceases to important for the capacity of a channel [1] past a threshold (roughly when the signal PSD equals the noise PSD), while the determining factor is bandwidth. So you just use a few Ghz+ radiation and you have enormous bandwidth available; once that becomes insufficient we can move to Thz+ light; and so on without much environmental concerns (just medium concerns -- atmosphere gets opaque), since power levels will be kept constant or lower. [1] https://en.wikipedia.org/wiki/Channel_capacity#Example_application https://en.wikipedia.org/wiki/Channel_capacity#Example_appli...
- Retric 11y ago
  I can think of a single highly popular counter example which used 100% wireless power over several miles. https://en.m.wikipedia.org/wiki/Crystal_radio https://en.m.wikipedia.org/wiki/Crystal_radio RFID are often a short range example of the same idea. So, it's less that wireless power is useless As it is modern devices needing lots of power.
  - darkmighty 11y ago
    Crystal radio is an interesting concept -- but note I didn't claim it was impossible, just highly inefficient and with mediocre power/range (I couldn't find sources, but apparently it's typically 40uW with a ~1m? antenna). Remember that's for a (usually) 50kW station -- that's 1e-9 efficiency, or 0.0000001%. Realistically I'd expect you to be able scale this to 10k's receivers to up to about 0.001%. It's not realistic to increase this power significantly due to health/electronics concerns for persons living close to the source and massive consumption -- bringing the power near a single station to 4W would consume 5GW, about 1% of total US power consumption! Interesting to imagine a system with sightly higher frequencies (20Mhz?) dedicated to power transmission. It'd essentially be a hugely wasteful system (and expensive with high powered antennas everywhere to mitigate invsq law) which however might be able to power ultra low power sensors and gadgets. Some clever phase distribution (pseudorandom modulation should do it) system would allow location with ~15m accuracy too (even working indoors, although building refraction and reflections might be a little troublesome).
    - deleted 11y ago
      [deleted]