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Transmitting Power Through Soil – Fact or Fancy?

transmitting power through soil
Electrical excitation of the local earth for resonant, wireless energy transfer

A recent article in the Calgary Herald described transmitting power through soil. Apparently, researchers at the University of Alberta have managed to send low-voltage electricity safely through the earth. 

The article gets a bit carried away about the possibilities. “In the longer term, there’s potential for building houses without wiring. You can put a conducting paint on the road and then drive your electric car without any batteries.” Of course, I found the subject fascinating and thought I would read the academic paper which describes the work being done.

Although I am publishing this piece on April 1st, this research is no joke. Scientists believe their experiments will scale to higher power and longer distances. They describe the potential (my pun intended) for revolutionary and disruptive technology impact on society. If you have a scientific bent, you might enjoy reading the paper even if you can’t follow all the math.

But baby steps, so far. The researchers fed 20 volts at low frequency AC through electrodes. A coil was attached to ground 20 meters away. Enough power got through the soil to turn on an LED. The picture above describes the system, which works by exciting currents in the coils at either 25 or 260 Hz. This seems to work only at very low frequencies. Much higher than 300 Hz and the power just gets dissipated as heat or electromagnetic fields.

And that got me thinking, are we creating another source of radio frequency interference?

Transmitting Power Through Soil may be a new source of radio interference

In my research, the closest analogy I could find to this new technique is called Single Wire Earth Return power distribution. This is a method of distributing power through a single cable, rather than the typical two or more cables on a power pole. SWER has been used in developing countries and thinly populated rural areas in Africa and Australia. It seems like the capital and operating costs of SWER are 70% and 50% cheaper, respectively.

As a method of rural electrification, the inductive fields created by SWER can interfere with telephone wires. If these utilities are not spaced far apart, the power system will wreck the phone system due to inductive coupling. When the single wire earth return systems provide higher voltages (20 kV in Australia) substantial radio interference can occur.

So, in the future, your neighbor may try to power his garden lighting by sending power through the soil. Since the system described in the paper is very low power, you might not notice. But if systems like these try to scale without consideration of RFI/EMI, we might just be unintentionally raising the radio noise floor even further.

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