6 ms·

It depends, when I live power is expensive, so yes efficiency or rather the lack thereof is a show-stopper.

Dylan16807 11y ago
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.
- TeMPOraL 11y ago
  > 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.
  - Dylan16807 11y ago
    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%.
- jacquesm 11y ago
  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.
  - Dylan16807 11y ago
    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.
- HeyLaughingBoy 11y ago
  It's nice in winter, I guess. In summer you just added a 49 watt heater to your room.
  - jacquesm 11y ago
    50 Watts, the phone is in same room.
  - Dylan16807 11y ago
    My room used a 100 watt light until last year, I can deal with it.
witty_username 11y ago
Expensive is relative. Power is still pretty cheap especially for the power requirements of a mobile phone. (I assume not more than 15 cents/kWh?).

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.

TeMPOraL 11y ago
> 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.
- Dylan16807 11y ago
  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%.
jacquesm 11y ago
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.
- Dylan16807 11y ago
  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.
HeyLaughingBoy 11y ago
It's nice in winter, I guess. In summer you just added a 49 watt heater to your room.
- jacquesm 11y ago
  50 Watts, the phone is in same room.
- Dylan16807 11y ago
  My room used a 100 watt light until last year, I can deal with it.

witty_username 11y ago

Expensive is relative. Power is still pretty cheap especially for the power requirements of a mobile phone. (I assume not more than 15 cents/kWh?).