Wireless Recharging

[baywax]

Here's an interesting development.

Could this be harmful to humans? How safe is electromagnetic induction?

New Technology Allows Wireless Recharging
By Sara Goudarzi, LiveScience Staff Writer
posted: 14 November 2006 06:21 pm ET
Buzz up!
0 Comments | 0 Recommend
In the future, we might recharge electronics the same way many people now surf the web: wirelessly.

Marin Soljacic, a researcher from the Massachusetts Institute of Technology, often forgets to recharge his cell phone. At times he is awakened by that last breath of electronic power that comes through as an unpleasant beep before the phone goes into sleep land itself.

“So, one night, at 3 a.m., it occurred to me: Wouldn't it be great if this thing charged itself?" Soljacic said.

The idea of wireless energy transfer is not a new one. Researchers have known that wires don’t always need to be in contact for electric power to get transferred.


http://www.livescience.com/technology/061114_wireless_recharge.html

[mgb_phys]

Very safe - the energy is only efficently transferred to a matched antennae and is very short range.
I once worked on a project to have self heating drinks where youplaced them in an inductor on the counter after buying them, it was perfectly safe to put your hand in the inductor with no chance of burnign yourself, unlike regular glass coffee jugs.

[baywax]

Very safe - the energy is only efficently transferred to a matched antennae and is very short range.
I once worked on a project to have self heating drinks where youplaced them in an inductor on the counter after buying them, it was perfectly safe to put your hand in the inductor with no chance of burnign yourself, unlike regular glass coffee jugs.

Cool mgb_phys!

Is this something that could expand to say... recharging an electric vehicle on the move?

[mgb_phys]

Not really ;-(
For practical efficency you ideally need the receiver to fit inside the coil. Or you need a transmitter coil bigger than the receiver and have them close together - ideally less than the coil diameter apart.

It's great for where you don't want an electrical contact, because you want something watertight sealed (electric toothbrush) or you don't want to bother with a connector (like the cell phone mat). But overall it is more efficent to use a plug if you can.

[baywax]

Not really ;-(
For practical efficency you ideally need the receiver to fit inside the coil. Or you need a transmitter coil bigger than the receiver and have them close together - ideally less than the coil diameter apart.

It's great for where you don't want an electrical contact, because you want something watertight sealed (electric toothbrush) or you don't want to bother with a connector (like the cell phone mat). But overall it is more efficent to use a plug if you can.

In a different article covering the same idea they mention using a laser as a directional influence to concentrate the em waves toward the device, thus, reducing scattered em energy and increasing efficiency. Is this sci fi or an actual probablility?

[baywax]

To answer my own question I'll reluctantly quote Wicipedia:

Laser


With a laser beam centered on its panel of photovoltaic cells, a lightweight model plane makes the first flight of an aircraft powered by a laser beam inside a building at NASA Marshall Space Flight Center.
In the case of light, power can be transmitted by converting electricity into a laser beam that is then fired at a solar cell receiver. This is generally known as "powerbeaming". Its drawbacks are:
Conversion to light, such as with a laser, is moderately inefficient (although quantum cascade lasers improve this)
Conversion back into electricity is moderately inefficient, with photovoltaic cells achieving 40%-50% efficiency.[25] (Note that conversion efficiency is rather higher with monochromatic light than with insolation of solar panels).
Atmospheric absorption causes losses.
As with microwave beaming, this method requires a direct line of sight with the target.
NASA has demonstrated flight of a lightweight model plane powered by a laser beam.

http://en.wikipedia.org/wiki/Wireless_energy_transfer