Wireless Power
Like many before me, I’ve been fascinated with wireless power and the prospects of leading a battery free, charger free life. There have been many attempts but not many have been successful.
- Inductive Coupling. Uses magnetic coupling, but requires very short distances (think power mats, and toothbrush chargers)
- Infrared Laser. This is an interesting concept except that you have powerful laser beams floating around and requires line of sight between transmitter and receiver (hoping nothing or no one comes between the transmitter and receiver!)
- Rectifying Antennas. Or “rectennas” use an RF antenna to receive RF waves and signals, “rectifying” the AC signal to produce DC power.
One promising solution was determined some 10 years ago at an MIT Lab: Resonance Coupling — Non-radiative energy transfer — which now serves as the base technology for WiTricity. The range is limited and the most promising appications seem to be for wireless power mats for charging electric vehicles.
Another promising solution has come out recently which is COTA by Ossia — which uses transmission of power through 2.4Ghz radio waves. The design is quite clever in that the receiving antenna or device acts as a beacon sending out an RF “ping” multiple times per second. The power transmitter receives those ping signals across thousands of small antennas for different positions and angles. The antennas that “hears” the ping from the beacon will transmit a power signal back (along the same path) to ensure that it is delivered unobstructed. Since this happens hundreds of times/second — the power signal can be sure to be transmitted directly without interference. The concept is known as RF energy harvesting and was also popularized by Powercast for the last several years in low power industrial settings and applications. While tantalizing — it appears that this approach still offers only reasonable power at close distance and low power at medium range distances.
Another interesting possibility was raised by uBeam a few years ago. They promised an interesting technology based on the beamed transmission and conversion of ultrasonic wave signals into power. However it seems they have failed to live up to the promises after $40M of capital invested.
WiCharge uses infrared beaming technology. And while this require line of sight and has limited applications that way — it uses infrared technology and is harmeless to human or other disruption.
While rectennas were thought of for far-field power transmission originally from the 1960's — a recent development considers using rectennas for ambient RF energy harvesting for lower power devices like smartwatches.
Other interesting possibilities were raised by Apple with AirPower — but ultimately abandoned for the standard Qi inductive wireless standard. And most notably have been Energous (similar technology to Cota) — which raised substantial capital in the public markets — but has also not lived up to the large promise.
While there appear to be some interesting opportunities — there do not appear to be any imminent or readily available technologies that overcome the physics challenges of energy radiation dissipation or the safety issues of line of sight energy beam transmission.
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