Peter wrote:
But it supports the concern that EVs are going to hit a brick wall. Well, they obviously will
Norway must be hitting the wall any day now because 80% of cars sold in May were electric.
Peter wrote:
I wanna see how they do this (the other methods are clearly unviable for cars) without frying the occupantsThis issue has been looked at by many people over at least the last 40 years. Basic physics dictates that if the air gap is say 20cm (typical for a car) then you will have a poor coupling factor. Then there are the health hazards for the occupants.
Exactly this kind of system was tried out in Visby 2021-22, which is the reason for the larger trial mentioned in @aart’s link. 1.6 km of the road between the airport (ESSV) and the town was equipped with a charging system used to charge one of the airport buses. The theoretical transfer capacity was 125 kW, although I’ve read one source saying that the actual capacity was 70 kW which is not bad either.
Apparently it worked without frying the pax. I guess either basic physics is wrong – or our understanding of it.
Is there any detail anywhere?
I can see one could do it, but not trivially or cheaply. One would need to set up a highly directional field, probably at quite a high frequency, and turn it on briefly as a vehicle crosses it.
And nobody has yet discovered a way to focus a magnetic field so it can be projected over a distance. So, another way would be microwave, which can be focused, but that has “significant” challenges in the user shielding department.
How much power did they need to draw from the grid to transfer 125kW into the vehicle battery?
Were the cars “real cars” with a ~20cm gap, allowing them to be driven on normal roads etc? The “maglev” stuff was well developed when I started at univ, 1975, but that uses totally custom gear, and small airgaps, and large coils.
I have been designing mains and other transformers since I was 10 (the basics are simple) and yeah you can get power across a large gap using just magnetics but the gap still needs to be a small fraction of the transmitter/receiver coil dimensions.
It won’t actually “fry” the pax; literally converting a human into a burger would need sitting in front of a megawatt-size radar antenna or some such, and even that might not work because it is pulsed. It might just heat up his brain too much. But this makes the 5G radiation concern quite funny.
The investment is massive because of the dimensions (roads are long). It has to be a joke, or a feasibility study for consuming R&D grants.
I fully expect Norway to go EV because of
Peter wrote:
without frying the occupants
You just won’t, the occupant won’t be exposed to significant magnetic field as they won’t be in the transformer core anyway, and is not really affected much by magnetic fields anyway (getting an MRI which involves significantly powerful magnets, tends to leave the patient still alive and un-fried afterwards).
The real concern is (1) tragically poor efficiency (2) EMC concerns. Making huge swathes of the RF spectrum unusable will make it a non-starter even if they handwave the horrible efficiency, to keep stuff small they will want to use high frequencies, and you can bet that the primary won’t be getting a pure sine wave (too expensive to do) so it’ll splatter over all sorts of important frequencies.
I agree, but how much of your life do you spend inside an MRI machine, versus inside a car? Can you imagine the public debate about safety? Even the 5G one remains unsettled; a meta study of the ~100 studies done found that only 2 of them met standard research criteria.
There is no way to send power over a 20cm gap, with tx/rx being of dimensions viable for a car, without a load of peripheral leakage.
Hence I call “BS” on this; something disingenuous was done to get the power across 
@Peter you might be interested in reading about Halbach arrays in relation to directing magnetic field and eliminating stray field without a solenoid. Not that it would alter the outcome of this issue – electric cars are clearly not going to ‘take over the world’ in the foreseeable future.
I just finished a 3000 km loop, outside on the roads of central Europe and saw almost no electric cars. The ones I noticed were almost all Teslas, but just a few. Instead endless lines of diesel cars and trucks blowing smoke in my face. I’m coughing just like always but my lungs will recover from that and similarly widespread secondhand cigarette smoke, just like always.
Over here there are so many Leafs on the road, you’d think it’s autumn…. (sorry, sorry, I’ll get my coat)
Haha
Here, the entry level for a 5k/term private school is a Tesla, or one of the usual “tanks”
you might be interested in reading about Halbach arrays in relation to directing magnetic field
I had heard of such a thing before. It is not surprising that this is possible, since one can do highly directed beams for standard E+M fields using phased arrays.
But the economics are nonsense. Can you imagine the cost of laying this stuff under roads, along the length of the road? Anyone can do a demo… Maglev works the opposite way: you concentrate the “kit” in the vehicle.
Airborne_Again wrote:
although I’ve read one source saying that the actual capacity was 70 kW which is not bad either. Apparently it worked without frying the pax.
So it indeed worked pretty well. But maybe a problem would be that people start driving sloooow just to make optimal use of it. Some even creating a traffic jam but those behind won’t be unhappy, or maybe less unhappy 
There is no doubt that it’s not energy efficient, but who cares once we have fusion Until that time, maybe take a step back and revert to the good old times of trams. Once over the ‘charging road’ a little sliding tentacle extends from below the car. Make the charging channel nicely narrow so people will keep their #%/^ lane! Taking cover now for the flak of the experts here!
An electrical contact makes the energy transfer trivial, but you still have a huge cost of digging up and electrifying 1000s of km of roads. It totally isn’t going to happen.
