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Capturing energy below HV powerlines EMF as an experiment - how feasible is it?

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LAN_403

nzoomed

Tue Jun 09 2020, 12:10PM

Registered Member #54503 Joined: Sun Feb 22 2015, 10:35PM
Location: New Zealand
Posts: 288

My friend has some HV powerlines running across his farm, I have been talking about experimenting with them to try and capture some electricity, albeit very low voltage that is potentially generated by its EMF field.

What way can you go about this?
Ive read that running a wire below them and then putting a bridge rectifier across one end of the wire and the other end to a ground rod will give you a measurable voltage, perhaps enough to light up an LED, or even charge a cellphone very slowly?

I believe you will get better results when there is more current running through the lines, on those days, particularly over winter, they make a real weird pinging sound on the insulators.

I have heard some stories of a farmer who had an electric fence running below some HV lines and he turned off the fence to work on it but still got a belt, which was attrubited to induction from the power lines much in the same way as a tesla coil. Is this likely?
I would have thought it would need to be a very long electric fence!

2Spoons

Wed Jun 17 2020, 05:04AM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

I've heard a story where a farmer has been able to run a small pump of the power pulled from a fence under an HV line. Until the power company came along and stopped it.
I'd suggest making a large 50Hz resonant loop (LC tank) and tapping power off that.

nzoomed

Fri Jun 19 2020, 06:09AM

Registered Member #54503 Joined: Sun Feb 22 2015, 10:35PM
Location: New Zealand
Posts: 288

2Spoons wrote ...

I've heard a story where a farmer has been able to run a small pump of the power pulled from a fence under an HV line. Until the power company came along and stopped it.
I'd suggest making a large 50Hz resonant loop (LC tank) and tapping power off that.

There seems to be many stories, most likely urban legends with lawsuits etc.
To capture any meaningful electricity you would need to run quite a long cable along the lines at close proximity to the lines I believe. You would need a fair bit of metal for the power company to notice any energy losses in the field, there is already a wire fence pretty much running alongside most of it as it is, have heard that steel water main pipes have been an issue in some cases.

Anyway, making a 50Hz, loop. Im not sure how you tune this to 50Hz, is it the same way as doing it with a tesla coil primary using a signal generator?
10 turns on my primary was resonating around 48-50Khz from memory.

klugesmith

Sat Jun 27 2020, 12:55AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

I think that to get a high-Q tank resonant at 50 or 60 Hz, the inductor needs to be physically large and heavy, with laminated steel core.
We want L/R time constant to be large compared to 1/2*pi*f.
For a given coil size, L/R is independent of the wire gauge.
But as we scale up the core and coil dimensions, without changing aspect ratios, L/R increases.
Super low frequency tanks can't be small, unless you have superconducting technology.

For reference, I was about to post a picture of an inductor for power supply pi filters.
10 henry, 300 mA, 56 ohm, I guess more than 5 kg. L/R = 179 ms.
Oops, no easy upload of pictures on 4hv. Here's an ephemeral link to ebay listing. Raphaelite brand from Sghenzen, China.

These might have air-gapped cores to improve the saturation current and energy storage parameter for a given mass.
In that case a gapless core would give better (larger) L/R time parameter.

Sulaiman

Sat Jun 27 2020, 03:05AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I doubt that you will capture much power by using the magnetic field as the current in the individual overhead wires sums to zero,
you will get some power as the nearest wire will contribute a little more than the farthest.

You can capture some power by capacitive coupling as the nearest wire 'shields' the wires above it.

Try holding a fluorescent lamp above your head beneath the wires, at night.
If you get some light then you could consider capturing power using the method that was originally mentioned;
running a wire beneath an overhead wire,
as it is a capacitive effect, an elevated horizontal sheet of aluminium cooking foil would collect more current
or chicken wire fencing etc.
the higher the collector and the more the area, the more power you can collect.
Insulate the collector from ground, measure the open circuit a.c. voltage caused by a capacitive divider effect between earth and the overhead wire, Voc
Measure the ac current to a ground rod, Isc
I guess that the maximum available power is (0.5xIsc) at (0.5xVoc)
so the optimum load resistance is Voc/Isc.
you can use a bridge rectifier for dc

the above is for educational purposes only as it IS illegal to steal electricity.

I've not tried myself so if you do try, please report your findings.

P.S. you could probably use a transformer to convert the high voltage high impedance to a more usable lower voltage at higher current,
e.g. something equivalent to an NST or OBIT or Ignition coil

if a fluorescent lamp is not convenient, a neon lamp/bulb may wotk as an indicator.

nzoomed

Tue Jun 30 2020, 10:33PM

Registered Member #54503 Joined: Sun Feb 22 2015, 10:35PM
Location: New Zealand
Posts: 288

Thanks, will give this a try when on his farm next.
I believe the lines have more current flowing some nights than others.
Since its winter now, I expect we should see more energy use. Quite often the lines make a "pinging" sound when there is high current flowing.

nzoomed

Sat Jul 04 2020, 11:32PM

Registered Member #54503 Joined: Sun Feb 22 2015, 10:35PM
Location: New Zealand
Posts: 288

Sulaiman wrote ...

I doubt that you will capture much power by using the magnetic field as the current in the individual overhead wires sums to zero,
you will get some power as the nearest wire will contribute a little more than the farthest.

You can capture some power by capacitive coupling as the nearest wire 'shields' the wires above it.

Try holding a fluorescent lamp above your head beneath the wires, at night.
If you get some light then you could consider capturing power using the method that was originally mentioned;
running a wire beneath an overhead wire,
as it is a capacitive effect, an elevated horizontal sheet of aluminium cooking foil would collect more current
or chicken wire fencing etc.
the higher the collector and the more the area, the more power you can collect.
Insulate the collector from ground, measure the open circuit a.c. voltage caused by a capacitive divider effect between earth and the overhead wire, Voc
Measure the ac current to a ground rod, Isc
I guess that the maximum available power is (0.5xIsc) at (0.5xVoc)
so the optimum load resistance is Voc/Isc.
you can use a bridge rectifier for dc

the above is for educational purposes only as it IS illegal to steal electricity.

I've not tried myself so if you do try, please report your findings.

P.S. you could probably use a transformer to convert the high voltage high impedance to a more usable lower voltage at higher current,
e.g. something equivalent to an NST or OBIT or Ignition coil

if a fluorescent lamp is not convenient, a neon lamp/bulb may wotk as an indicator.

I was up on the farm last night and held up a fluorescent tube and it did light up!
Even with little power running through the lines it was making it glow, I stood up on the top of the vehicle and it was even brighter.
We were there for a few mins and we heard the lines start to make some noise on the insulators and the tube started glowing brighter It kind of flashed a bit with pulses.
I took a video that I will upload to youtube.

So basically whats happening is that there is an air gap capacitance between the powerlines and the ground, me and the tube?
The tip of the tube was not bright, but the base of it near my hand was alot brighter.
Im assuming that the voltage difference between the top of the tube and the powerline is less than where my hand was holding the tube?
In other words, the ground potential would increase, with the higher you hold the tube?
It would take a fair few volts to excite the gas I would think? I didnt have a multimeter on me at the time, but will return to take a measurement by grounding one lead of the meter and the other to a pole held up in the same way as the tube. What sort of voltage would I expect to see?
Im guessing the line voltage is around 100KV. Am trying to look on the power grid map for their voltage, but can only see 200KV lines showing as the lowest and not these ones that are running through the property.

The tube does not light up at all unless its pretty much straight under the wire above. They are 3 phase, and the tube only lights up on the outer phases. Im assuming that either the centre phase is grounded, or that the field is cancelled out by the other 2 phases?

I was watching this video here

I dont know why they are using a spark gap, but it looks a similar method to what you describe.
I will definitely try this and report back.

nzoomed

Sat Jul 11 2020, 08:46AM

Registered Member #54503 Joined: Sun Feb 22 2015, 10:35PM
Location: New Zealand
Posts: 288

Another update.
I was up there today and we held up a 3 meter long piece of wire up about 2 metres in the air and hooked up one end to the multimeter and the other lead to ground and we got a reading of 60 volts!
We definitely will be back to run a much longer wire and see what results we get. Going by this we are averaging 20 volts per meter. For maximum efficiency if im using a car ignition coil, would it be better to get a matching voltage say 20KV if possible to match the secondary on a 20KV ignition coil?
If i run about 100M of wire we can expect 2000V at this rate if its 20V per metre. Could be more, but will wait and see I guess. Might need to find a better matched transformer for the experiment but will likely still give us enough power to experiment with.

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