ubeam

To be semi-fair, the "technology" page you linked to does explain that ma king it feasible is "excruciatingly difficult". They mention such challenge s as "impedance mismatch, air coupling, beamforming, acoustic losses, low p ower rectification" and so forth to actively steer multiple kilowatt-power beams up to 4 meters.

They also claim to have solved all of these problems while making it safe to be around.

I don't believe them either.

Mark L. Fergerson

Kilowatt? I don't think so. They aren't talking about charging cars, just phones and such. You likely saw the spec "316 W/m2 ? 3kW/m2". That's an energy density would would be 31.6 mW/cm^2 to 300 mW/cm^2. The idea is to keep the beam concentrated and not let it cover a square meter.

".

first you have to get from transmitter to air and air to receiver and then end up with at least something like 5W to charge a phone

even if they managed to get a few percent of a few percent you are not going to need a heater...

-Lasse

The web site proposes powering televisions and fans and lights.

Where do you get the few percent numbers? Isn't that one of the problems they've said they've solved?

Hehe they have said a lot of things. Let's see a working prototype, driving a filament bulb not a high-impedance voltmeter, whilst an employee of theirs is holding it near their face and not wearing hearing protection.

nd.

if

This does skip a relevant bit of information. James Arthur hangs out with R epublicans. His ideas of what government can do are based on a crowd who co uldn't put up a more attractive candidate for their presidential nomination than Donald Trump.

In Scandinavia and Germany, whose constitutions were written more recently than the one in use in the US, the governments collect a much larger propor tion of the GDP than the US does, and spend it effectively on creating a he althy, well-educated, well-trained and productive work force.

So James Arthur's scepticism about the effectiveness of government action is based largely on his experience of a rather poor example of government.

If pushed he'll tell you how bad the East German government was before the Wall came down, and try to persuade you that German Democratic Republic was socialist - as it claimed to be, but with no more justification than its c laim to be democratic.

Of course if you want real idiocy, you have to go to people like James Inho fe.

Am 15.05.2016 um 06:58 schrieb John Larkin:

Ask the Expert! ;-))

Jorgen

"Magnetic resonance" charging gets rediscovered every couple of years. As if tuning wire loops was some sort of revelation.

Any time you broadcast a bunch of power around a room, megnatically or acoustically or optically, a lot will be lost.

Maybe fuel cells refueled in-flight by drones. ;)

Cheers

Phil Hobbs

Hah, I haven't heard of micorwaves yet. We should have a start up, with microwave horns.

I don't understand the desire for wireless power, when wires work so well.

George H.

People don't like wires. They'd love to buy into the beginning of a world where the wires are gone. Engineers like the upside of wires, others dislike the clutter & tangle, and dream of being above all that.

NT

They've already considered using microwaves to beam power from satellites to the earth. A bit larger scale than to your cell phone, but I don't think they have any real issues with the technology other than the perceived risk of the sat loosing positional lock and frying people on the ground. Clearly the perceived risk is higher than the real risk, but the real risk is not zero.

I thought they proved that it wouldn't fry people, which means of course it never got funded. If they proved that it would easily fry people and could be an effective weapon, they would have been given enough money to build it right away.

IIRC the power density at the ground station was supposed to be less than that of sunlight (1kW/m2) which is why they said it was safe, but then why not just cover the same area of ground where the antenna was going, with PV? I guess back in the 70s PV was much more expensive than antennas and much less efficient than microwave rectifiers, and so in cloudy places it might make sense (if money and launch energy were neglected).

A more interesting thing (that I have seen videos of) is beaming power

Oh dear.

Well other than Rayleigh scattering and whatnot. Never might the sheer weight of the object in orbit.

Will that ultrasonic thing power up toasters and vacuum cleaners and hair dryers?

It's easy to design with a small transmit antenna, which cannot have enough gain to reach dangerous ground-level intensity (diffraction limited, you know).

OH, that's easy: the generators above the atmosphere see MORE SUNLIGHT than anything on the ground (and wider spectrum), and one can make a rectifying antenna (rectenna) with very high efficiency (easily three times the efficiency of the best photovoltaics) and at very low cost. Factor of two on solar illumination, 100 on square meters/dollar, five on DC conversion: there's three orders of magnitude benefit.

As the other wise man said, "If he's so smart, why ain't he rich?"

Cheers

Phil Hobbs