ive been thinking for a while, since we managed to transfers some data wireless ie. wifi, 3g, and things like that, and i do know that it uses radiowave. but the question here can we actually transfers power wirelessly? what i meant here is transferring the electricity wireless mean you have an adaptor that plugged into wall socket and the receiver is connected to device which received the power wirelessly. This is just some thought of mine. I dont know whether its possible or not. If you dont mind, please discuss.

This post has been edited by Shah_15: Mar 22 2010, 02:25 AM

There's a lot of research are done regarding this

I think some of them did success, I remember I watch it on discovery or something, it just that the cost of implementing it is more expensive than having cables.

http://en.wikipedia.org/wiki/Wireless_ener...o_and_microwave

The problem is efficiency. Conversion factor aside, a lot of power is lost when we send it over the air. We would need a huge power source to transmit over any meaningfully large distance. Transmitting data requires power on both receiver and transmitter side btw.

Saw a research some time back using laser to transmit power that can keep a specially designed lightweight hobbyist airplane continuously in the air, as long as the beam is not interrupted. The plane just flew in circles a couple of feet in the air.

Sure it is possible.

I think photoelectric will be the best to answer your question.
When electrons r emitted from the target metal.
The answer u r searching is there.

infrared is possible right?

nothing is impossible.

transmission of electricity by means of electromagnetic waves is possible. however, dont expect it to replace wires and high voltage cables anytime soon. the low efficiency and potential radiation danger means it would most likely be used short range to charge low voltage devices (cell phones, ipods, etc)

think i watched and read abt this loooong time ago.. yes, it's possible frm what i remembered.. but the drawbacks are : radiation and takes too long do even charge a small amt of energy to that device..

search nikola tesla's experiment

Energy need a medium to be transfered.in this case you may refer it to the air.so, the most suitable method to transfer the energy is by utilizing the optical or radio wavelength.it has been applied in many apps such as remote sensing. since there are some limitation like absorption and scatering in using optical wave, so radiowave is the best method. the problem might be arise now is 'how to carry electric by the radiowave'

Hi All,

interesting discussion.

however, a few basic things we need to know:

1) Electricity consists of:

a) Voltage - Potential difference between 2 points
b) Current - the flow of energy (electron flows at the opposite direction - current was discovered/established b4 electron)
c) Impedance - the resistance to the current flow in a medium

Comparing to water:

Water at the reservoir high above the hills has potential energy. Water flows downward to a lower area thru water pipes. The size of the water pipes determine the amount of water flowing thru it. Can we transfer water without pipes? Maybe in the future?

2) In order for electricity to flow, we need a medium or "conductor" (the "pipes"). Without the pipe, water will get splashed everywhere & some areas might be flooded & ppl drowned (hazard!). Same with electricity.

3) While conductor is used for transfer of current (i wont refer to electron on sub-atomic level), we need insulator to protect the surrounding from getting electrical shock and flash-over. Short-circuit is a fault that is not desired in electrical system. it is similar to water leakage in the pipes.

4) Air is an insulator. If current flows thru air, it's an "arc". Arcing occurs when very high current flows thru the conductor and it ionized the air and caused the dielectric (insulator) breakdown. it will find the closest path to ground/earth/another conducting path to complete the circuit. This is similar to lightning phenomenon.



In practice, we do not want "arcing" to occur because this is electrical hazard. Very high current is flowing thru and a lot of heat is generated.

While i cannot foresee the future (anything is possible), at the time being, electricity must be channeled thru a conductor and protected by insulators.

Electricity is different from data transfer.

Thanks.

1. Energy doesn't necessarily needs a medium to be transferred. E.g. light and radiowaves can travels through vacuum and vacuum-like condition in the space.

2. Like I mentioned earlier, the problem is efficiency. Say you use 1W to send out a radiowave, how much of that 1W is received by the intended receiver? 0.1W? 0.01W? or 0.001W?? Why is radiowave not a good idea? Because it is transmitted in broadcast method i.e. the energy will be spread out over a large area where most will be lost.

3. Radiowave is a form of energy. Converting this back into electricity is simple and done everyday by RF receivers. There's no such thing as carry electric on radiowave.


You have it right about electricity but got it wrong about power transfer.
1. Power transfer doesn't means we need to use electrical current. Using electricity for wireless power transfer would in fact be very stupid because we already know electricity doesn't conduct well at all over the air.

2. Electricity is a form of energy, similar to sound and radiowaves. Whether we used it to transfer data or power, that's totally dependent on the application. E.g. the 240v power cord connected to the TV, that's purely for power transfer only. Or the way we capture sunlight on solar panels to charge up a battery, in which case power is being transferred using light waves over the air.

3. Also, there's nothing that says we cannot extract power from wireless data. In fact, that's exactly what touch'n'go transceiver and many other access card does. Power transfer of this type is only over very short range and for very low power application only.

false.

what is the medium of transfer for light which can travel fine in a vacuum

A very interesting discussion. MIT has/had been conducting research about this i reckon.

I LOLed at the "Power transfer doesn't means we need to use electrical current".

I guess there is nothing more i can say until u read about P=IV

I rest my case. hva nice day.

Nikolai Tesla started transfer 'power' wirelessly around hundred years ago. Only later people put data, protocal and different frequency in these 'wireless power' then became 3G, wifi etc...... So it is the other way around.

This post has been edited by locke: Mar 28 2010, 12:59 AM

Maybe you guy a bit slowpoke liau. Read here -->

http://forum.lowyat.net/index.php?showtopic=1150990&hl=

I thought about this also the last time. It will be brilliant if this concept would come to reality. Imagine charging our phones without cables.

Actually "wireless power" up a device is already been using for many many yrs. And this thing is around us and some of us using it daily. Just we don't realise it.

The touch n go card and the passport chip that been scan is using wireless power to powerup the chip memory and record your data. Nothing special inside. Just the coil and some chip.

If it's small amount of power, it's alredy been implemented. If you're talking about transferring megawatts of power wirelessly, then i it has not reach a efficientcy where it is viable.

http://dvice.com/archives/2010/03/rca-supplies-po.php

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Added on March 29, 2010, 12:51 pmbut check out the comments section... very interesthing read, more so interesting than the article.
So do you think this device will decrease the performance of the wifi AP?

This post has been edited by beatlesalbum: Mar 29 2010, 12:51 PM

Wifi signal has probably less than a watt output power. Once it reaches your antenna the amount of power your device can absorb is probably less than 1mW. I don't see how 1mW can charge a battery.

It said 6 hours for full charge.. lets do some calculation shall we?

I guess it using the wave vibration to generate back the current. Any vibration or movement from the wave can generate current to large enough for charging.

Tell me, is there current flowing through air between the up and down steps of a coil transformer?

Simple picture to 'assist' you



This post has been edited by befitozi: Mar 29 2010, 06:57 PM

obviously not.

1mW continuous power can charge a battery albeit over a long time. Boost charger circuits and capacitors are the key to utilizing low voltage/low current power sources. E.g. garden solar powered light usually have a rechargeable battery for storing the power absorbed during the day, and then releasing it during night time. It only powers a small led though.
This won't work for high power equipment e.g. laptop. Nobody is going to buy it if it takes 10 hours to charge up before we can start using it, and only to use it for 5 hours max.


That's one good example of power transfer.
Definition of Power is rate at which work is performed or energy is converted.
Electrical power has a source, then some wires and an electrical load at the end.
Similarly I can have a coal fired steam generator, some insulated pipes to carry the steam and a mechanical load at the end.


So it seems we've discovered 2 aspects to TS question,
1. Just grab power wirelessly from whatever there is out there. E.g. using wifi signals, or one can even harness power from those many power transmission lines that now and then go nears a residential area. Or solar/wind/etc power.
2. The generation and transmission aspect. E.g. if a salesman were to try and sell a generic consumer wireless laptop charger, I would weigh for e.g. how fast can it charge up, how much my electrical bill would be and the effect on my health.

hi, nice pic.

Seriously, u really think a transformer transform the voltages thru "AIR" ??

LOL

What's the iron core for?

Wires with rubber insulators can conduct to the core? Go back to school and learn SPM physics please.

Transformers works with electromagnetic induction. I guess there is no point we discuss this topic with you as you definitely have no idea about Faraday's and Lenz's laws, what more Maxwell's Field equations.

---

Added on April 1, 2010, 7:33 pmBack to topic.

I always found this topic to be extremely fascinating.

Anyone thought about transmission through higher dimensional space? Some theories suggest that EM waves are side effects of other phenomena happening in higher dimensions. Maybe if we induce that said effect at the source and have it propagate through such space and reproduce itself at the destination.

Though the physics of this could be solved, what about the engineering of it. Food for thought.

This post has been edited by befitozi: Apr 1 2010, 07:33 PM

To answer the question about the iron core, it is simple to concentrate the electromagnetic flux within the core for more efficient reception of the second coil.

Wow! Good.

So since u know that magnetic flux in the core induces the voltage on the secondary coil, then, y u ask "is there current flowing through air between the up and down steps of a coil transformer"?


A few things to clarify:

Air doesn't play a role in making this a "wireless" transfer of "power".

The iron core is important to "concentrate" the magnetic flux because air is simply inefficient. And the iron core is also made of thin layers of laminated sheet steel to eliminate eddy current (a form of transformer losses because it generates heat - 100% efficient transformer is only theoretical).

So, after all, there is current flowing in the iron core. Power loss is P = I^2 x R

Secondly, it's not called "up & down steps" of a coil transformer. It's called the primary or secondary winding of transformer. In electrical engineering, since there r "step up" & "step down" transformer, the "primary" & "secondary" don't make a good reference (ambiguous). Therefore, it's called the "LV side" & the "HV side".

Thirdly, rubber is not used as insulation for the copper wires. In the industry, PAPER ("Kraft paper") is used for large transformers (say 15MVA 132/33kV) and it is oil-impregnated when immersed in insulating oil (for cooling & insulation purposes). For very small transformer PVC-insulated cables are used. Never rubber.

I guess SPM didnt teach u all that rite?

Thanks.

p/s: Thanks Xerone.

That question and example arose because you insists power transmission requires the use of current. Which is totally wrong.

Eddy currents causes LOSS in power. Are you saying the power loss is the one that is being transmitted? Hahaha.
This example is perfect to show how wrong you are in stating power transmission requires current. Do you even read what you type?


Mind you the low permeability of air is the barrier so it definitely plays a role.

The iron core as Xerone pointed out is to increase it's transfer efficiency but is not a must. We can have a primary winding that coils over a secondary winding with nothing but air in between and it'll still work. The transformer example simply illustrate there's no wired connection between the primary and secondary windings, thus proving power can indeed be transferred "wirelessly".

Again power transmission doesn't necessarily needs electrical current. I've provided an example where power transfer can be done without using nor involving electricity at all in my previous post. So what's wrong with my statement?

Hi,

OK, air has low permeability.

However, quoting wat u said about "air DEFINITELY plays a role". Can u explain how does air play a role in "power transfer" in the transformer? With the characteristic of having low permeability?

For example:

I want to cross over to the other side of the river bank, but there is a huge river separating me and the other side of the river bank.

So... i use a bridge.

But, how does the river play a role for me to cross the bridge?

The river itself is a "barrier" in the first place. Just like air, it is not playing a role because it is a problem that requires a solution.

It is due to the fact that air is a "barrier" that the iron core is used in the first place.

Back to the power & current issue:

(Maybe if we call it TRANSFER of ENERGY, it will be better. It's easier to agree energy can be transfered and converted in many ways, as long as "Conservation of Energy" is observed.)

Now, when there is power, there is a function of current & voltage involved. No matter it is power loss or power transfered or power consumed, power is computed as a function of voltage, current and impedance (Ohm's Law).

The "phenomenon" in the iron core is electromagnetic induction, per se.

What the magnetic flux does is to induce emf in the other side of the windings, causing current to flow when the circuit is connected to a load and thus, power is consumed.

Then, may i ask, how do u compute the amount of power transferred by the magnetic flux?

Bear in mind that what goes on in the iron core, although this is an undesired power loss, is I^2 x R, where I is the eddy current. Although this is power loss, it is also a part of the equation:

Total Input Power = Total Output Power (power consumed at the load) + Total Power Loss (iron & copper).

(Conservation of Energy. Checked.)

Nevermind.

Basically, I get wat u mean. U want to induce lots of magnetic flux (devoid of "current"), then propagate it thru air (wirelessly) and thus cause the receiving end to have electricity (like the transformer).

So, we can somehow use a device to transfer 240Vac supply from 13A socket outlet across the living room to a laptop on the table thru thin air... hmm... ya, i like it too!

But u have said it very well, air has low permeability. So do u still expect power to be transferred via EM wave thru thin air?

Anyway, i do not deny that there may be a possibility someday to make it feasible.

So, what is the next best thing available? Thru current in a conductor, can?

Thanks

This post has been edited by enmavel: Apr 2 2010, 04:01 PM

1. I'm saying air plays a role in wireless transmission. And the reason is low permeability.

2. It's calculated by Faraday's Law. In a complete Maxwell field equation form it is : [curl.E = - d/dt B ] where E is electric field and B is the magnetic field.

3. Of course we can. Except that you will receive only 1nW out of 100W of what you want to transfer

4. Definitely. Maybe you should relook your perspective of what 'air' is. Air is simply space with very very few particles, where as a liquid would have more and solid even more. Of course current can flow through air just extremely inefficient as you said in your first post. Arcing occurs, it is dangerous and massively inefficient. that's why i propose the idea of using higher dimensional space. The concepts of it aren't very new, and certainly isn't fiction either.

5. That's the whole point of this discussion isn't it? .We are trying to find a way to avoid using a solid conductor for obvious physical reasons. On top of that, we are also dismissing the fact that transfer through current is needed. Which you seem to claim that is the best way to do so. Clearly not, else Nikola Tesla would have ruled the world with his inventions.

This post has been edited by befitozi: Apr 2 2010, 04:19 PM

Hi,

Thinking in this direction, if the exterior of a house is being wound with a large coil and subjected to induced electromagnetic field, and all the electrical equipment in the house has built-in "secondary" windings, that can in turn, induce emf and VOILA! ... "wireless" power transfer!

But conducting objects will be heated up too... like the pot on the induction cooker.

Therefore in practice, induced EM field is what ppl is trying to avoid. if 2 conductors r placed side by side, with only 1 carrying current, the 2nd conductor will also have induced current flowing due to the induced magnetic field. (that's y 3-phase power cables are arranged in trefoil formation)

Then other appliances will also need very good insulation, because EM is also a source of "noise", especially in AV equipment....

i do not know if human body is OK with such exposure too...

Is this wat we want to do "wirelessly"?

For the sake of discussion, some suggestions in the following analogy, for the fun of it:

let's say i have a large water reservoir on top of a hill. i want to supply water to the village downhill but i do not want to use water pipes.

Maybe i can do it "pipeless" by allowing the water to evaporate and become clouds. The clouds will then drift to the village and become rain. Villagers can then collect the rain water for their daily use.

Or,

Maybe i can freeze the water into sizable ice cubes/balls etc. then roll it down hill for the villagers to collect and thaw into water to use.

Or,

Transport the water bucket by bucket to the village by trucks.

I think wat we need to consider are:

a) safety
b efficiency
c) feasibility

thanks

1. Radio waves are EM too. As long as it is below UV frequency it should be fine

2. Similar to the idea i said about higher dimensions. Using a different medium not in direct contact with our physical world

3. Similar to laser/photonic transmission. Very promising field imo.

This post has been edited by befitozi: Apr 2 2010, 05:01 PM

I am not sure but, if we do want to use the same transformer principles to excite the secondary coil installed in some electronic device without the need for a medium, shouldn't the change in EM field be at a sufficiently high frequency? Would keeping it at radio wave frequencies work?

I don't think we should look into magnetism as a solution. I used it merely as an example to show that current is not necessary to transmit power.

But another field where magnetism should be explored extensively is magnetic levitation. but that's a whole new topic all together

The definition of power is rate of energy conversion (E/t), or rate of work done(W/t). wiki: Power (Physics)
P = VI is for Electrical Power, that ain't wrong.
But there's also Mechanical power: P = ( F * d ) / t, where F is force and d is displacement. Force can be simply cause by steam or wind pushing a turbine, and displacement can simply be a bucket filled with water being lifted from a well.
Says who current and voltage must be involved in power?
There's also human power, horse power, solar power, wind power, etc... With so many types of energy in this world, how can ALL energy conversion i.e. power involved current and voltage?


So you neither rebut nor accept my statement this time.
Look if you read back my first 2 posts in this topic, I've already said efficiency is the main problem with wireless power transfer. The only reason we went around a big bush is because you disagree electrical current is not necessary for power transfer.
I'm not questioning your electrical knowledge, but you said my statement is wrong so the onus is on you to provide proof to back yourself up. We've already provide 2 examples where current is not involved in at least one of the power transfer path.
In fact, this whole side-tracked discussions appears to stem from your insistence that power must involved electricity.


That's exactly how passive RF sensors (access card like touch'n'go cards). Certain radio frequencies transmit relatively better over the air e.g. 27Mhz, 455Mhz, 900Mhz. These passive access card draws power from RF carriers waves generated by the transceiver. Range is very short but it's another example of no wires power transfer.

Assuming a 100% efficiency conversion,(which is not possible btw if you didn't realise it),

P= VI

You need to have approximately 4.5V to charge a Li-On battery.
So the amount of current you can charge is

0.001 = 4.5I
I = 0.2mA

In real world I expect say 40% efficiency that would mean around 0.1mA

Assuming a 1000mAh battery, it would take approximately 10000 hours or 416 days to charge a battery.
However since a battery itself has it's own self discharge and your self discharge is higher than your charging current.
1mW will never be enough to charge a battery.

But transferring information and transferring useful power are slightly different things right? Information can be digital signals (transferred using EM waves) and only require very small amount of energy. I'm only a mechanical engineer but I'm guessing the receiving end of the Touch n Go thing has some sort of amplifier to boots input signal from the card. Low frequencies should suffice for this application.

But for powering devices, wouldn't we need a higher frequency for greater current?

Hi,

Thanks 4 the definition.

Now we are talking about "electricity" rite? So, i'm talking in the context of electrical power. If u take wat i said about power involving current out of the context....

Tun Abdullah Badawi "transferred power" to DS Najib - NO CURRENT INVOLVED ("wireless" too )

OK, U WIN


Solar "Power" or Solar "Energy"?

Can we decide a term to be used amicably here? Well, I have said in my reply to Senior Member befitozi:




OK, let's look at SOLAR ENERGY:



So, we can see the nuclear fusion gives out energy.

This energy is transferred to earth, and the "light" that we receive during daytime is from photons.

(The cycle starts with the thermal collision of two protons (1H + 1H) to form a deuteron (2H), with the simultaneous creation of a positron (e+) and a neutrino (v). The positron very quickly encounters a free electron (e-) in the sun and both particles annihilate, their mass energy appearing as two gamma-ray photons) Nuclear Fusion

It is this energy that we "harvest" at the photovoltaic cells:

This energy causes the photovoltaic to emit electrons and this electron causes current flow, which in a complete circuit connected to load, gives us power.

So, i dun call it solar power when it's not yet realized as "power"... while it's still in the transfer process as "energy".

Another story:

Money gives us "buying power" & i must earn money 2buy something.

U can say u dun need to involve "money transaction" to buy something (by barter trade )

Money, is like current, it flows from 1 party to another, giving the person having it "buying power"....

So, I plant durian in my orchard (sun).

Passers-by asked: 'What r u doing?"
Me: I'm planting "buying power"
Passers-by: ???

So, during durian season (nuclear fusion), i collected my durian & transport to pasar malam to sell.
Passers-by: Wat r u doing?
Me: I'm transferring my "buying power" to pasar malam
Passers-by: ???

So i sold my durian (photon) & i got money (current) & now i have "buying power"... I can buy 10 nasi lemak for my family

OK, sorry. Went to far off the track LOL



May i ask something...

Touch n' Go cards, u need to touch it rite? The "reader" reads the info in the microchips via RF.

Those SmartTAG, (active RFID) has battery & thus it transmit the signal back to the reader via RF.

Err.. RF... = power transfer?

Nevermind.

Guys, interesting discussion here. No hard feelings OK?

Err.. for simplicity sake, I'd assume the 1mW is net received power after transmission and conversion losses. And 1mW is also an arbitrary number for the sake of argument.
My argument that 1mW is sufficient to charge a battery is generally based on the design of solar powered night light.
Assuming the night light LED uses 3mA at 1.2V and needs to run for 8hours per night. That means simple total power drain is just below 29mW. Hence 3mW of continuous charging power for 12 hours per day during daytime will be sufficient for it's night time operation. It's a simple calculations but suggest plausibility. You can see why I think 1mW can charge a battery, just depends on what is the load and application.


First higher frequency doesn't means greater current. Simple example, our 3G network uses 2100Mhz, our 240v AC runs at 50Hz. I'm not an expert in this area though, so that's just the simple idea.

Next consider this. Let's say you are transmitting data using some sort of RF signal from one transmitter to another receiver. Now what's to stop me from say making another receiver that also reads the same RF signal, but only converts the electrical signal I received to powers say an LED?
Both electrical signal and electrical power are made of voltage and current. Whether it's a signal or power is our interpretation and application. Of course in order to create the signal, we modulate data into the signal waveform (commonly called carrier). And usually signal lines doesn't carries much power due to well, it's not designed to transfer power after all.

Yah I can see why you think 1mW can charge a battery because you don't look at the bigger picture and consider things like battery self discharge or switching regulator efficiency . Furthermore you're already assuming you can collect 3mW from a wifi signal. And 3mA at 1.2V, it's probably just a dot of light at night

Are you from EE background?

---

Added on April 4, 2010, 10:56 pmSimple, in a normal reciever there is an amplifier that amplifies the recieved signal. The recieve signal alone is probly in the uA range and is unusable without an amplifier before being fed into a mixer. And the amplifier itself uses power itself what more charging a battery.


This post has been edited by Drian: Apr 4 2010, 10:56 PM

No I mentioned 3mW can be use to charge a battery for very low power applications. I did not say it must comes from wifi. The question for me was merely, can 3mW or 1mW charge a battery?
I interpret 3mW or 1mW as available net power. You interpret is as before conversion losses. So it's a simple misunderstanding. That in no way means I do not understand regulator efficiency and battery self discharging.

And it's only a small pool of light yeah but I'm only pointing out a product available on the market, not arguing about the pros and cons of it. Also the example is meant to point out such low amount of power is only suitable for very low power application whereby stressing the key issue of wireless power transfer --> transmission losses, which in my mind has always been the bigger picture.

I'm a firmware programmer, which in itself is a field that covers programming and a little on electronics. I'm not strong in analog electronics though so I'm curious about the amplifier you mentioned. Since the purpose here is merely to collect power and not the signal data, is there really a need for amplifier and mixer? I'm assuming the right antenna will convert the carrier waveform into similar electrical waveform. Since it's an oscillating waveform, then theoretically we can use the voltage doubler or boost circuitry concept to boost up to the right amount of voltage and current we want right?
And if amplifier requires power to function and is required in order to extract energy from RF signals, it would be a chicken and egg story and doesn't explains why passive RF tags work.

Erm. Didn't bother to read anything, but wireless power is indeed possible. Ultra long range, maybe not for now. But utilizing induction, it's quite possible.

And about current flowing. Maybe someone didn't go to school, but last i figured, when you have a wireless inductive field, the field itself induces a voltage and with a voltage you get a flowing current through the system. That's why you call it induction. The stators and the coils of a generator are inductively coupled, if there is no current flowing, how does we get power?

My background is Electrical Engineering, majoring in Power, current dissertation in power transfer and transformer stat measurement.

Topic: Transfers power wirelessly, Wifi, 3G. can electricity did that too? (Science)

The definition of power is RATE of Energy Transfer.

Power dun "exist" while energy is converted from 1 state to another. It is a measure of rate: how fast work is done.

If I push a box, I'm transferring energy to the box, overcoming friction and cause it to move (kinetic energy).

How fast i perform the work (rate), is a measure of the amount of power i have.

If i can push a box for 1 m in 1 sec and u do it in 2 sec, i'm more "powerful" than u. (example only )

I do not transfer POWER to the box.

Secondly, when u pay for electricity, u r paying for ENERGY = kWh transferred to your house. Not for "POWER" transferred to your house.

Since ur avatar looks like wikipedia , here u go: Electrical Energy

kthanxbai

Passive RF Tags works because it requires very little current and they are limited only to approsiamtely 30-50mW. That makes the effective distance approximately 2-3 feet from a 1 watt transmitter with a 0.03% efficiency.If you want to charge a battery 2-3 feet away at a 0.03% efficiency , it's pointless since it has to be so near the transmitter. If you're using in a wifi environment where things are like 20-30 feet away and from a lower power transmitter. You can forget about charging any battery from it. The signal strength decreases with the inverse square of the distance, so your power requirement increases exponentially as the distance grows.



Wow you're expecting voltage doubler to give you double the voltage and current for free?


This post has been edited by Drian: Apr 6 2010, 10:04 AM

So passive tags work and there's really no need for amplifier and mixer in order to just extract power from RF signals, glad we cleared that one.
And yes a 1W RF transmitter probably aren't practical for wireless power transfer except for very low power application and of very short distance.
So can we move along now?

I believe lightning strikes the best natural & ancient example of electricity travels wirelessly.

Lasers, microwaves, infrared etc can do that too if the output power is strong enough.

google witricity... n frm wut i see frm dis thread, all just squabbles

Say what? So, mechanical agitation can amplify electrical current?


There's no current flowing through the air, as many have pointed out. This is an inductively coupled circuit, but EMF flows in the steel core.

Higher dimensional space rarely means a superspace, in most physics calculations it's a subspace i.e. a compactified dimension. If we can reach into these compactified dimensions and meddle with stuff anytime we like, I don't think our universe's physical laws will be the way they are because then, our physical constants would have been very, very different to begin with.

Using higher dimensional space to do stuff is a dumb idea and besides, the maths doesn't permit it. If it has no direct contact with our physical world, it also means we can't touch it and transfer information through it.

We don't need a high frequency for a greater current, we just need a suitable frequency based on the transmission medium. Transmitting power wirelessly would require both devices to be in resonance at the same frequency, so that a resonant cavity can be set up. This resonant cavity's frequency must be optimized based on our requirements, whether we're transferring a little or a lot of electricity, and whether we're transmitting a short distance or a long distance. It's kind of like the carrier wave that's most suitable for the medium or the transmission parameters.

For instance, to transmit over long distances, we'll have to use longer wavelengths. Nikola Tesla suggested the use of the Schumann cavity for resonant-coupled wireless power transmission.

Lightning is plasma. It has a conductive medium to flow through. Yeah, that's wireless if you rigidly define "wireless" as being the absence of metallic conductors. If such were the definition, then transmission through conductive plastics would be considered "wireless" as well.

Lasers, microwaves and others can't do it as easily for a few reasons. It depends on how much energy that ambient air can absorb in those wavelengths. Microwaves can pass through air rather easily, so it won't impart much energy into ambient air. Infrared radiation can heat ambient air, but it'll take a hell lot of energy for IR to get to the breakdown point of ambient air. Lasers get scattered and attenuated somewhat by ambient air, but it still doesn't dump a lot of energy into ambient air because air don't typically absorb visible light spectra anyway.

How about if we condition the air so lasers, infrared & microwave can travel their designated path without much loss of energy?

Also isn't UV considered "wireless power"? They can power up calculators & those headshaking cardisplays.

Well, true that we don't know much about it yet. As energies required to just probe those postulated dimensions are well beyond whats available on earth.


That's simply photo electric effect. It is certainly possible but with immense limitations as said by jswong. But research into photonics is pretty large nowadays so it is the most likely method.

But, that being said, a simple obstacle in the path would beat the system so not practical for large scale transmissions.

Whoa........prety far out right ? So many dimensions and places to go.....

Real power is awesome stuff. Just try sticking your fingers into the wall socket if you wanna find out.

Like most of you guys have said before efficiency is actually the key. Welll actually safety too. But at the end of the day, EM waves that can cause unknown effects on humans, light based transmission that can fry flying birds andcables that as long as nobody messes with them will be fine, I'll take cables anytime.

"Dimensions" is always misunderstood. A dimension is not a parallel universe, like how the science fiction cartoon and movies always speak of it as. A dimension is simply a direction through which space and time are measured. Length, width, height, these are dimensions. We don't say that we can travel into the width dimension and see a separate existence, do we?

No. What I am saying is about control. As a scientist they can work with as many dimensions as they want. But in reality, the task of really implementing it at this moment is too great. Power consumption is too great at this point for anything wireless. Regardless of dimensions, the energy must travel through matter. All beings are also made of matter and may also be present at that very dimension.

But again, my greatest doubt on this would be efficiency. Even currently to convert from AC to DC or vice versa the highest I have ever heard of at the level which we call power is no more than 95%. I doubt for the next 20 years we will have enough technology for energy to be transferred 100kms as efficiently as cables.

Just a quick reply to this, I noted that ppl have quoted from Wiki with links to Nikolai Tesla. And as I remember from Astro, he had many stumbles, not necessarily because his idea of wireless energy was not efficient enough, or not the best solution, but simply because he was unlucky, and didn't live long enough to fulfill his dreams.
(yes, at present it isn't good, but who knows how it would have developed if Nikolai had his way)

If it wasn't because of that guy, we'd all probably still be using Edison's DC for our computers.

i use to think Edison is a nice guy and a pure hearted scientist due to books i read as a kid that made him a hero of science, but them i found out about Tesla which never been given enough credit in history and Edison is a a****** businessman that would stop technological progress to preserve his business model on DC.

someone need to recreated the tesla wireless power experience if only for how awesome the tower look



This post has been edited by robertngo: Sep 13 2010, 04:59 PM

Heheh... agreed.

I think it left only the engineering matters. For high frequency wave (<nm wavelength), the photonic energy, E = hf. But offcz it would attenuated easy by dust, and somemore ionizng effects.

For radio frequency, I believed could make use of the resonant effect.

It is odd if we cant transfer power by EMwave if the definition of em wave is travelling of energy from one partical point to the other