How Wireless EV Charging Works

[bernardgreen]

quoting from :-

https://eepower.com/tech-insights/ev-charging-on-the-move-how-the-wireless-technology-works/

This magnetic field transfers power to the vehicle wirelessly as it moves along the track. The system is designed so cars can move freely in both forward and backward directions without staying precisely on the wires or using costly magnetic materials. As a result, the electric vehicle can charge while driving, offering a flexible and efficient way to stay powered without the hassle of stopping at a traditional charging station.

 

[ericmark]

Seem to remember trialled by a guy called Nikola Tesla many years ago, but the losses were too high.

Throughout the 1890s, Tesla pursued his ideas for wireless lighting and worldwide wireless electric power distribution in his high-voltage, high-frequency power experiments in New York and Colorado Springs.

Tesla tried to put these ideas to practical use in his unfinished Wardenclyffe Tower project, an intercontinental wireless communication and power transmitter, but ran out of funding before he could complete it.

 

[DetlefSchmitz]

The algorithms resulted in a 90% increase in the power transfer efficiency for electric vehicles

But they don't say what the absolute efficiency is.

Seem to remember trialled by a guy called Nikola Tesla many years ago, but the losses were too high.

Yes but Tesla was trying to transmit the power using electromagnetic radiation. These people are using magnetic coupling (like iPhone chargers) which is likely to be much more efficient.
I am just not sure how efficient it will turn out to be though. With ideal coupling (phone sits on pad) a phone can get about 70% efficient. Car driving over a prepared surface will be less efficient. Maybe when renewable energy is responsible for generating all our power, we can afford to throw away half of it on inefficiencies?

 

[Harry Bloomfield]

I am just not sure how efficient it will turn out to be though. With ideal coupling (phone sits on pad) a phone can get about 70% efficient. Car driving over a prepared surface will be less efficient. Maybe when renewable energy is responsible for generating all our power, we can afford to throw away half of it on inefficiencies?

Will efficiency, not be a function of distance between coil and receiver? In a car, that can be several inches. There will also be large losses in transmission and energy wasted, due to eddy currents, created in metalwork close to the coils, as well as the vehicle body.

 

[plugwash]

Will efficiency, not be a function of distance between coil and receiver?

Yes, but size of the coil is also going to be a factor. I haven't studied this stuff in detail, but I suspect a larger gap can be compensated for by larger coils.

 

[morqthana]

So we'll make EVs even heavier.

Great idea.

 

[Harry Bloomfield]

If they go to the extreme of burying coils all along the roads, they may as well do away with batteries, and use linear motors.

 

[JohnW2]

Will efficiency, not be a function of distance between coil and receiver? In a car, that can be several inches. There will also be large losses in transmission and energy wasted, due to eddy currents, created in metalwork close to the coils, as well as the vehicle body.

I think one has to be careful about what one means by 'efficiency' in this context.

I think what most people are talking about is how well/fast the magnetic coupling transfers electricity from the source to the load. However, even if that transfer is pretty poor (which I imagine it definitely could be), if no power from the source is 'going anywhere else', the actual 'efficiency' (proportion of power/energy leaving the source which gets to the intended load) could well be very high, couldn't it?

 

[Why Not Indeed]

£50 says this idea never gets anywhere.

 

[DetlefSchmitz]

I think what most people are talking about is how well/fast the magnetic coupling transfers electricity from the source to the load.

Efficiency is power received divided by power supplied. How could you think it meant anything else? And what could well/fast mean?

 

[JohnW2]

Efficiency is power received divided by power supplied. How could you think it meant anything else?

Exactly - so if no power were going to, and being dissipated in, anything other than the intended load, then the efficiency would be 100%, wouldn't it?

And what could well/fast mean?

Good transfer of power/energy. Take a couple of small coils an appreciable distance apart, and you would be able to achieve a small amount of transfer of power between them (hence a small amount of transfer of energy over time), but not much. However, in the absence of any power 'going anywhere else', the small amount being received by the load would be reflected by an equally small amount leaving the source - so, again, a very high 'efficiency', but only very little 'transfer of power'.

 

[RandomGrinch]

Maybe when renewable energy is responsible for generating all our power, we can afford to throw away half of it on inefficiencies?

I'm afraid I haven't looked into the details of this yet, but my first thoughts turn to the 'Woodhead line" - some of the first examples in the UK of electric locomotives using regenerative breaking to power trains up the grade, on the other track.
Even with significant inefficiencies, on certain hills, there could be a benefit for electric/hybrid trucks?

 

[flameport]

https://eepower.com/tech-insights/ev-charging-on-the-move-how-the-wireless-technology-works/

Nothingburger article.
Some research effort no doubt paid for by someone else's money into charging autonomous warehouse carts while they are moving.

Cars are unrelated. Charging cars while they are moving is a solution looking for a problem. Neither needed or wanted.

 

[DetlefSchmitz]

Good transfer of power/energy. Take a couple of small coils an appreciable distance apart, and you would be able to achieve a small amount of transfer of power between them (hence a small amount of transfer of energy over time), but not much. However, in the absence of any power 'going anywhere else', the small amount being received by the load would be reflected by an equally small amount leaving the source - so, again, a very high 'efficiency', but only very little 'transfer of power'.

So you are inventing a system that is 100% efficient but transfers very little power? Not sure what the limitation would be, but it's your invention. Given that current systems with idea coupling are only 70% efficient, I'm not sure where you're coming from. Who, in the thread, are you accusing of assuming your definition?

 

[JohnW2]

So you are inventing a system that is 100% efficient but transfers very little power? Not sure what the limitation would be, but it's your invention.

I'm not 'inventing' anything - I'm merely stating facts, as I see/understand them.

Obviously nothing in the real world is "100% efficient". However, if one had something approaching a 'prefect' coil (near-zero resistance) connected to an AC source, then if there were nothing within the field of that coil into which anything could be 'induced' (again, probably impossible in real world), then, if it were connected to an AC source, then something approaching zero power would be supplied to that coil.

If another ('secondary') coil were to be brought into the field of the first one, and connected to a resistive load, then a little voltage would be induced in that coil, resulting in a little power being dissipated in the resistive load. If secondary coil also had a near=zero resistance, then the only power dissipated would be that dissipated in the resistive load, and the power supplied to the primary coil would also be equal to that dissipated in the resistive load. Hence "100% efficient" - something impossible in the real world.

Given that current systems with idea coupling are only 70% efficient, I'm not sure where you're coming from.

See above, and below.

Who, in the thread, are you accusing of assuming your definition?

It's not "my definition'. It's what I thought (perhaps wrongs) was being talked about Harry, yourself and perhaps the article to which bernard linked. In other words, I thought you were also talking about "how effective" inductive coupling was as a means of transferring energy from A to B (e.g. from a source to an EV).

Do you deny that it would be perfectly possible for a system to be, or be approaching, "100% efficiency" (per your {and the usual} definition of 'efficacy') whilst at the same time being totally inadequate as a means of transferring energy at a useful rate from from A to B ?