Beecham Research’ snaps #37
Once upon a time, when radio technology was new, wireless communication seemed almost magical.
Today we take it for granted but this is not so for wireless electricity, a technology dating to the same period — Nicola Tesla was awarded a patent in 1905.
Wireless electricity is making a new commercial appearance and may seem nearly as magical to some of us as radio may have seemed to our grandparents and great grandparents.
M2M satellite terminals and 2G modules are very often designed for long field life and extremely low power consumption. When no other power source is available, they rely on batteries and no one wants to replace batteries on remote assets sooner than necessary. Emerging wireless electricity technologies may prove useful in this situation.
Wireless Charging and Induction
Several wireless electricity technologies are based on electromagnetic induction, the discovery of which is credited to Michael Faraday in 1831. The short version: Voltage is created when a conductor moves through a magnetic field. This is the basis for generators, transformers, electric motors, and solenoids.
Inductive coupling is featured in the short-range wireless electricity charging pads already on the market. A powered coil within the pad creates a magnetic field, which induces current to flow through a small secondary coil built into portable devices; this current recharges a device’s battery or batteries.
The Wireless Power Consortium, currently at 83 members including Leggett & Platt, Johnson Controls, Samsung, Philips, TI, Tyco Electric, Orange, Verizon Wireless, and founding member Fulton Innovation, among others, is developing open standards for wireless chargers. Its Qi 1.0 standard, focused on interoperability between devices and chargers, was announced in September, 2010; the first certified devices were announced at the same time. In 2011 the consortium announced the commencement of work extending Qi from an up to 5 Watt low power specification to a medium power specification delivering up to 120 Watts.
Missing from the consortium: Qualcomm, Powermat, and Duracell. Qualcomm announced alliances with Powermat and Duracell in January, 2011. Qualcomm envisions a dual-mode ASIC backward compatible with both Powermat’s system and its own Wipower system; Qualcomm and Duracell will promote Wipower as a standard.
Charging pads are already found in public service vehicles and fleets, not just as stand-alone products, and are sure to show up just about everywhere before long, but these aren’t likely to be very helpful when it comes to recharging remote battery powered devices.
Radio Frequency Harvesting
Another wireless electricity technology, radio frequency harvesting, has a history in RFID and biomedical implant applications but has yet to reach its full potential. RF harvesting can use ambient radio waves — Nokia announced, in 2009, research towards creating a form of this technology that would harvest ambient radio waves of many frequencies, theoretically enabling a cellphone to be perpetually charged.
With this technology electricity is transduced into RF signals, transmitted, then received by power harvesters, which transduce the signals back into low voltage direct current. RF harvesting can work at ranges of up to 85 feet. Regulation in the U.S. and Canada restricts the amount of power that can be transmitted to 4 Watts EIRP. Received power is determined by distance and antenna performance; available energy after conversion is in the low milliwatt and microwatt range but this is sufficient for low power applications.
One company to watch is Powercast, headquartered in Pittsburgh. Powercast’s products are currently used to power wireless sensors and sensor networks in a range of industries and include asset tracking applications. This technology may become much more prominent in M2M applications. Per Powercast’s website: “Devices that typically operate on batteries for months or years can benefit from Powercast’s patented, high-efficiency RF energy harvesting technology. The cost of wiring or battery replacement can be eliminated in low-power devices through wireless, remote trickle-charging, or devices can be made completely battery-free.”
Magnetically Coupled Resonance
Magnetically Coupled Resonance (MCR) is a somewhat more exotic wireless electricity technology. The analogy often used to explain it is the familiar glass shattered at a distance by an opera singer’s voice, wherein the soundwaves produced by the singer are captured by the glass and transduced into mechanical vibrations; when the note sung matches the resonant frequency of the glass, the glass absorbs energy and shatters.
With MCR, energy is transferred between two magnetic resonators — they resonate much as the singer’s soundwaves and the glass. MCR was invented at MIT, where it was demonstrated in 2007 by using it to illuminate a 60 watt light bulb from a power source over 2 meters away. WiTricity Corp., in Watertown, Massachusetts, was founded to commercialize the technology. MCR can be used to recharge batteries and power small devices, like inductive coupling and RF harvesting, but can also be used in applications using more powerful devices.
Anyone from the early part of the 20th Century would be mystified were they to be transported to the present and notice people seeming to converse with little boxes, just about everywhere.
A kindly person might attempt to explain the nature of cellphones to them, then possibly continue with an explanation of M2M and the Internet of Things. This would be a lot to absorb, but if they were to then bring up the subject of wireless electricity, the visitor might just nod and say: “Tesla.”
