Researchers develop “rectenna” to convert radio waves to electricity

[The Straight Story]

Researchers develop “rectenna” to convert radio waves to electricity


Researchers from Nihon Dengyo Kosaku Co., Ltd, (DENGYO) a Japanese communications infrastructure company, have developed a device they call the “rectenna” that can convert radio waves moving around in the air, to electricity. The name comes from combining the word “rectifier” (a device that is normally used to convert AC power to DC, but can also be used to detect radio signals) with “antenna”.

In the demonstration video, the researchers say that the rectenna can convert both WiFi and digital terrestrial broadcast signals, though the amount it converts depends of course on the amount of radio waves in the vicinity. The rectenna comes in two sizes, one for converting WiFi signals, the other for terrestrial. The WiFi version is small, just 12 mm thick, while the terrestrial version is 30 mm thick. Each looks like a plain soft-white pad.

Engineers demoing the two devices say electricity produced by the WiFi version is in the microwatts at a distance of just 10cm from the source, not a lot of course, but enough to power a small sensor or tag, they say. As for the terrestrial version, they were able to generate about 1.2mV and 0.06µW of power inside the exhibition hall, where the video was made, at the Tokyo Big Sight. The signals received were from a digital terrestrial broadcast sent from the Tokyo Tower which was about 5.5km away.

http://www.physorg.com/news/2011-08-rectenna-radio-electricity.html

[originalpckelly]

1. That's nice, but it's like claiming to have invented the wheel yesterday.

What do you think RFID chips are?
Those are not just creepy product identification things, but also the microchips in dogs.
Rectenna's have already been explored for many years.
All radios, just happen to be, wireless power systems.
That's how those AM radio hobby sets work, you know the ones that don't need any power. They just use the power they get from the radio station to power the radio.


Rectennas are the future of power.

[randr]

2. Wasn't Tesla working on transmittion of electricity?

[Cirque du So-What]

4. Why, yes, he was

Thomas Edison's monumental ego demanded to be assuaged, however, and Edison wanted to capitalize upon the construction of a brute-force infrastructure - one with which we're still saddled to this day.

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

[originalpckelly]

12. That's AC v. DC.

Oddly enough, high voltage DC is now the fad, because we now have transistors which can covert it up to extremely high voltages, which allow DC to work well over long distances. In the outback, they even have a system where it's just one wire, with the actual ground being used as a return.

[Cirque du So-What]

15. Yes, the article is AC vs. DC

I intentionally went on a tangent in order to slam Thomas Edison's monumental ego. I have an agenda, I admit.

[originalpckelly]

16. Oh, yeah, I completely see that.

He was a total dick. :P

[originalpckelly]

5. He was, but I believe it was only partly through wireless means.

He was using the ground as a return, IIRC.

Wireless power is pretty awesome in that it never needs the return to work. I mean, within the circuit in the thing receiving energy it does, but not to the actual power source.

Some day in the future planes will be powered wirelessly.

People are too stuck in the past to realize that the way we will get clean energy is to place solar power stations in orbit around Earth. Launch costs have been dropping dramatically since the private company SpaceX got into it all, and I believe that they will probably be the launch platform to get it done. What they need to do is to develop an airborne platform to launch rockets from high altitude like the Pegasus system, just not off an airplane, but perhaps some type of airship.

[ewagner]

3. true

devices for transmitting microwave frequency signals from point-to-point and then converting them back to electricity have been around for decades....the problems is efficiency. As I understand it they can't find a way around the "inverse square rule".

[originalpckelly]

7. The problem is less the efficiency and more the law that you speak of.;

Because they are not transmitting a coherent wave, like a laser, they always have to deal with it spreading out as they get further away from the transmitter.

The interesting thing most people don't know is that the transmission technology is almost as efficient as a normal power line, so long as you have a rectenna that accounts for the inverse square law. Basically, you have to have a bigger target (rectenna) as you get further away from the source, so you can capture the energy.

There are coherent wave technologies, like masers that actually preceded visible wavelength lasers, it's just that as I understand it, that particular type of transmission is like you said less efficient (by such a vast margin as to make it untenable.)

NASA is working on a coherent power transmission technology, like you'd need, for aircraft. They managed to get a shitty model airplane to work this way, by using something like a solar panel to covert the energy into electricity for the plane.

I think the real breakthrough the researchers are talking about is that it's in a different part of the spectrum.

[ewagner]

17. In the early 70's

there was a proposal for Solar Power Station Satellites that would generate electrical power in a geosynchronous orbit and transmit the energy back to earth via microwave signal where it would be reconverted to electrical power....lots of problems with that idea but it held out some promise..

In the 70's the efficiencies of RF transmitted power were substantially lower than conventional transmitted power. I did not know the technology had advanced.

[Tesha]

18. Inverse square law doesn't apply to wide-area focused beams.

If the microwave beam is several miles wide and only traveling
several hundred miles (from orbit to the ground), you can pretty
fairly ignore inverse square law.

The same concept is used terrestrially in point-to-point
microwave or laser links; the beam may be demagnified
at the transmission point and losses through inverse square
law are roughly reduced by the amount of demagnification.

Tesha

[RC]

6. P. T. Barnum, is that you?

30 to 40 years ago, I use to work for a broadcast company. At their AM transmitter,in the tuning shacks. was a speaker, and a small output transformer and a power rectifier. That was the monitor so we could hear the station.
No antenna. No tuning anything. No circuit board. Just the parts soldered together.

How is this any different?

[originalpckelly]

8. It's not RC, it's just in a different part of the spectrum.

It's not some revolutionary new breakthrough, just a minor one.

[WinkyDink]

9. Man, they need a better name.......

[hlthe2b]

10. My thoughts, exactly...

;)

[trusty elf]

11. But, but, but.....something analogous.....

[MilesColtrane]

14. How about the assolenoid?

:shrug:

[MilesColtrane]

13. NEWS FLASH: Your not going to be able to power your house by listening to the morning drive guys.

Thanks, guys in lab coats!