Wireless Energy Transfer and RF Energy Harvesting

There's nothing new about transferring and manipulating power via electromagnetic induction. The Transformer was invented in 1885 by three Hungarian engineers, Ottó Bláthy, Miksa Déri and Károly Zipernowsky and Michael Faraday began his experiments with electromagnetism in the early 19th century. Thanks to AC induction and the fact that voltage and current are inversely proportional ( P=VI ) we're able to transmit voltages of 110 kV and above over long distances using relatively small conductors with minimal loss. Thankfully AC won in the war of currents. Edisons Direct Current grid would have meant running 24" diameter conductors with boosting stations about every hundred miles.

Those wireless pad phone chargers ? Transformers with the primary coil in the pad and the secondary coil in the phone. It's wireless, but the phone has to sit on the pad. By using frequencies in the range of 300MHz (0.3GHz) and 300GHz in the electromagnetic spectrum, Scientist have successfully been able to transfer moderate amounts of power at distances close to a hundred feet. It's still induction, with two coils but the coils are designed to operate at a resonate frequency ( inductive and capacitive reactances are equal in magnitude but cancel each other because they are 180 degrees out of phase ). This isn't the same as harvested ambient energy. The receiver coil is tuned to accept the RF frequency generated by the transmitter coil and the devices that are available today are limited to small amounts of power distribution.

Ambient RF energy harvesting would be receivers that were capable of harvesting any and all RF noise from your mobile phone to your smart tv to your router and then some. This essentially would be free energy. As long as RF flood our atmosphere and a transmitter that could automatically tune in to the prevalent frequency could through induction, capture and store that power.

https://www.arrow.com/en/research-and-events/articles/the-realities-of-rf-power-harvesting

I looked at an idea a few years ago, of using tuned induction circuits, as a way of powering road vehicles.
I thik they were able to power things over a 3 foot air gap.
In practice, If the interstate had the primary in the concrete, an electric vehicle could ride on top,
and tune in the power. metering their usage.
In this way once a vehicle got to the interstate, they could run until the bathroom became necessary.

longview said:

I looked at an idea a few years ago, of using tuned induction circuits, as a way of powering road vehicles.
I thik they were able to power things over a 3 foot air gap.
In practice, If the interstate had the primary in the concrete, an electric vehicle could ride on top,
and tune in the power. metering their usage.
In this way once a vehicle got to the interstate, they could run until the bathroom became necessary.

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That would take a massive power source to do that. Figure multiples of HP needed to move a vehicle @ .75 Kw/ hp

Transformers are rated in kVa, so Line voltage x amperage x 1.732 divided by a 1000 to get kVa

Line volt and sq root of 3 ( 1.732 ) stay constant but amperage increases with load which increases with every vehilcle added and youre talking about a xformer of epic proportions.

Now you can increase the frequency which allows for smaller conponents and greater efficiency, ( like one masaive flyback transformer ) but it would still take massive power source.

Fenton said:

That would take a massive power source to do that. Figure multiples of HP needed to move a vehicle @ .75 Kw/ hp

Transformers are rated in kVa, so Line voltage x amperage x 1.732 divided by a 1000 to get kVa

Line volt and sq root of 3 ( 1.732 ) stay constant but amperage increases with load which increases with every vehilcle added and youre talking about a xformer of epic proportions.

Now you can increase the frequency which allows for smaller conponents and greater efficiency, ( like one masaive flyback transformer ) but it would still take massive power source.

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You are right, the energy used by every vehicle on the interstate would be a large number, and the inconsistent output of alternate sources,
make them incompatible with such a load.
I think we had a discussion on a different forum a few years ago, it would take many nuclear plants, with that output being their primary function.

longview said:

You are right, the energy used by every vehicle on the interstate would be a large number, and the inconsistent output of alternate sources,
make them incompatible with such a load.
I think we had a discussion on a different forum a few years ago, it would take many nuclear plants, with that output being their primary function.

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One way to greatly improve efficiency and to reduce the size of a transformer and electrical components is to increase the fundamental frequency ( 60 hz ) with a oscillator circuit

DC switching power supplies which are in every flat screen TV, desktop PC, Bluray player etc, exploit this principle to produce clean high power DC with a transformer thats typically no larger than a 9v battery.

Aircraft power runs at 400 Hz instead of 60 Hz which alllows them to use smaller components which saves weight and space

Of-course when you increase utility frequency past 60Hz you run into other issuses including excessive inductive reactance and harmanonics which is why utiltiy companies decided to settle on a 60Hz frequency.

Also frequencies below 50Hz cause incandesent lights to flicker. We have the technology now to mitigate and offset some of the by products of power high frequency power distrubition.

I read somewhere once that power plants decided to send out AC at 60Hz because it made clock design easier

Clock manufacturers could then just use one 60hz synchronous motors with 3 x 60:1 reduction gears to get hours, minutes and seconds.

Fenton said:

One way to greatly improve efficiency and to reduce the size of a transformer and electrical components is to increase the fundamental frequency ( 60 hz ) with a oscillator circuit

DC switching power supplies which are in every flat screen TV, desktop PC, Bluray player etc, exploit this principle to produce clean high power DC with a transformer thats typically no larger than a 9v battery.

Aircraft power runs at 400 Hz instead of 60 Hz which alllows them to use smaller components which saves weight and space

Of-course when you increase utility frequency past 60Hz you run into other issuses including excessive inductive reactance and harmanonics which is why utiltiy companies decided to settle on a 60Hz frequency.

Also frequencies below 50Hz cause incandesent lights to flicker. We have the technology now to mitigate and offset some of the by products of power high frequency power distrubition.

I read somewhere once that power plants decided to send out AC at 60Hz because it made clock design easier

Clock manufacturers could then just use one 60hz synchronous motors with 3 x 60:1 reduction gears to get hours, minutes and seconds.

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I heard the 60 Hz came from the speed where diesel engines optimize 3600 rpm.
I think the easy (and likely) approach will be to store irregular alternate energy as hydrocarbon fuels.
They have a long shelve life, and are compatible with all the existing distribution infrastructure and vehicle requirements.
I think the most recent data says the process is 70% efficient, but electrical power generated when there is no demand is 100% lost.

longview said:

I heard the 60 Hz came from the speed where diesel engines optimize 3600 rpm.
I think the easy (and likely) approach will be to store irregular alternate energy as hydrocarbon fuels.
They have a long shelve life, and are compatible with all the existing distribution infrastructure and vehicle requirements.
I think the most recent data says the process is 70% efficient, but electrical power generated when there is no demand is 100% lost.

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Yea I thought the clock explanation was interesting but not very credible. As far as diesel generators go European power runs at 50Hz and Tesla's first AC power plant was hydro electric.

The load characteristics of the average home have changed immensly since then. All the non linear loads and the high speed switching thats going on in just about every electronic device we use cause harmonics ( integer multiples of the fundamental frequency ) to be superimposed onto the utility's 60hz frequency and this feedback back can cause power quality issues and lead to a dangerous situation where the neutral wire carries a alternating current.

Manuafacturers install harmonic mitigating devices including power factor correction and hi and lo pass filters on their DC power supplies but it still doesn't cancel out these parasitic loads completley.

Have access to a decent 100Mhz oscilloscope ? If you check your power you'll see distortions of the utility sine wave that corepond to a lower power factor. Lower power factor equates to lower efficency and even premature failure of electrical devices

Fenton said:

Yea I thought the clock explanation was interesting but not very credible. As far as diesel generators go European power runs at 50Hz and Tesla's first AC power plant was hydro electric.

The load characteristics of the average home have changed immensly since then. All the non linear loads and the high speed switching thats going on in just about every electronic device we use cause harmonics ( integer multiples of the fundamental frequency ) to be superimposed onto the utility's 60hz frequency and this feedback back can cause power quality issues and lead to a dangerous situation where the neutral wire carries a alternating current.

Manuafacturers install harmonic mitigating devices including power factor correction and hi and lo pass filters on their DC power supplies but it still doesn't cancel out these parasitic loads completley.

Have access to a decent 100Mhz oscilloscope ? If you check your power you'll see distortions of the utility sine wave that corepond to a lower power factor. Lower power factor equates to lower efficency and even premature failure of electrical devices

Click to expand...

I am familiar with the problem, wire loops and ferrite beads, the harmonic signals seem to still show up.
Where I have seen it most was in laser power supplies.

longview said:

I am familiar with the problem, wire loops and ferrite beads, the harmonic signals seem to still show up.
Where I have seen it most was in laser power supplies.

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Yea Ive been into electronics since I was a kid where I started off with hobby building DC linear power supplies, signal generators, shift registers etc and used to do industrial power quality analysis, troubleshooting and mitigation for a while.

Once I was on site installing a variable speed drive and a inverter rated motor. The plant head electrician was with me ( guy was a insuffable ass, no idea what his problem was ) and when it came time to power up the drive so I could program it I had him reset the breaker.

Well it tripped his whole panel and he came unglued. I knew his panel was jury rigged and expected as much. It was a unbalanced load and the nuetral carried all the excess current straight to ground.

He told me I better not reset power or else and I told him to fix his half assed servive or hire someone that could do it right. Things escalated from there and I was escorted out of the plant.

Lol....oh well

Fenton said:

Yea Ive been into electronics since I was a kid where I started off with hobby building DC linear power supplies, signal generators, shift registers etc and used to do industrial power quality analysis, troubleshooting and mitigation for a while.

Once I was on site installing a variable speed drive and a inverter rated motor. The plant head electrician was with me ( guy was a insuffable ass, no idea what his problem was ) and when it came time to power up the drive so I could program it I had him reset the breaker.

Well it tripped his whole panel and he came unglued. I knew his panel was jury rigged and expected as much. It was a unbalanced load and the nuetral carried all the excess current straight to ground.

He told me I better not reset power or else and I told him to fix his half assed servive or hire someone that could do it right. Things escalated from there and I was escorted out of the plant.

Lol....oh well

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I have tried (not always successful) to avoid real electrical power issues, but have run into feedback issues in electronics.
In the early days of fiber optics, we would build our own laser diode transmitters,
It turns out you just cannot switch on and off a laser diode at 40 Mega hertz, the ground gets very noisy.
In that case we used a dummy load, so the current stayed the same, we just shifted which load it fed (real or dummy).