Over 120 years ago, the venerable, and brilliant Nikola Tesla claimed that it was possible to transmit power around the world using a system of towers and balloons and was backed financially by a few of the early venture capitalist types to make it happen.
Over 120 years ago, the venerable, and brilliant Nikola Tesla claimed that it was possible to transmit power around the world using a system of towers and balloons and was backed financially by a few of the early venture capitalist types to make it happen. At the risk of antagonizing some of his followers – Tesla was perhaps more of a showman than a scientist with this observation. As this particular venture failed miserably.
Although, Tesla’s eventually successful concept of using alternating current against that of the all American hero, Edison, with direct current, wasn’t immediately embraced resulting in some distress to Tesla.
Power Transmitted through the Air is Growing Rapidly
Wirelessly powered devices are rapidly growing in importance - ranging from mobile phones, kitchen appliances and inevitably medical devices such as heart pumps. Soon to be a $15bn market within the next decade.
Inductive Coupling is the first Technique
Induction is used for the most successful versions. An alternating current passing through a coiled wire creates an oscillating magnetic field which induces an alternating current in a nearby coil. The closer the two coils the better. A slight increase in distance apart results in a catastrophic collapse in efficiency. This technique is widely used – ranging from toothbrush chargers and soon-to-be hovering drones. Tuned coils operating at the same resonant frequency can improve the energy transfer efficiency.
Standards, Standards, and Standards
There are three main standards bodies that have emerged….all vigorously competing with each other: Wireless Power Consortium (Qi) with 200 firms operating at 5 watts – big in smart phones. Power Matters Alliance (PMA) – big in the fast food market such as McDonalds. And Rezence (Alliance for Wireless Power or A4WP) now merged with PMA – but still promoting two separate standards (ouch!). Rezence is supported by the massive Intel so this may be the turning point in the competition for the best standard.
Useful for Electric Cars or not?
There is widespread support for one standard to use wireless power for electric cars at 20kW and 85kHz driven by the Society of Automotive Engineers. However Tesla Motors (one of the dominant players) is unenthusiastic about this believing that they are hopelessly inefficient compared to wired methods of charging.
What about Safety?
There are enormous concerns about this radiation from wireless power. I tend to agree. Having high levels of radio frequency energy bouncing around can’t be healthy and this aspect needs to be carefully considered otherwise we will have a jump in strange cancers and damage to our bodies.
How Efficient is all this?
Transformers work well as there is a nice chunk of iron that helps to transfer the power from the one coil to the next. When you boost the frequency you can certainly eliminate the iron core and use an air core. However, as soon as you move the coils apart with an air core – the efficiency drops dramatically. This is pure physics. So there is a big problem with power loss in all these schemes which rely on a significant air gap.
However as we all know – inefficiencies and problems with the laws of Physics aren’t a deterrent to the entrepreneurs out there pushing their barrow. So I am sure this will be a very big business in due course.
Thanks to an interesting article in the Economist entitled: Electronics has already cut the data cord. Can it now cut the power cord as well ?
The famous architect, William McDonough in 2006 made a great quote about wireless power: Don't get me wrong: I love nuclear energy! It's just that I prefer fusion to fission. And it just so happens that there's an enormous fusion reactor safely banked a few million miles from us. It delivers more than we could ever use in just about 8 minutes. And it's wireless!
Yours in engineering learning,
Mackay’s Musings – 23rd June’15 #570
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