A couple of problems with EV charging roads?

[Crash Gordon]

I've seen a couple of articles about roads with embedded inductive
charging for EVs. And there are a couple of issues that seem to me to
make these roads unfeasible. (I'm not even going to get into any of the
financial side)

My qualifications: I have a few decades experience in circuit design
and have had the word "Engineer" in my job title at several different
employers, but never went to college. So I have a lot of
"wisdom-through-experience" but there are a lot of holes in my basic
knowledge -- I tend to know a lot about the things I know, but nothing
at all about other closely related things. So I am quite willing to
accept that there's stuff going on here I simply don't understand. Feel
free to educate me. Moving along...


First: Inductive charging is basically building a transformer where the
primary is in one device (in this case, the road surface) and the
secondary is in a different device (here, an EV). Ordinarily when we
design transformers, we take great care to maximize the coupling between
the primary and secondary because loose coupling is responsible for much
of the loss in transferred power.

But in charging an EV there is necessarily going to be a considerable
air gap between the primary and the secondary. Although we can optimize
in other areas to account for this somewhat, it seems to me that there's
going to be a lot of energy lost here, mostly as heat radiated into the air.

Second: In order to transfer significant energy, there's going to have
to be some significant coupling of magnetic fields between the EV and
the road. Wouldn't this be a source of substantial drag? Effectively
the car would be driving "uphill" the whole time it's charging.


My thought is that if we're going to be shoveling huge amounts of
electricity into a road surface, we could use it more efficiently by
building a giant linear actuator with the EV as the moving part.


Opinions?

[john larkin]

Post by Crash Gordon
I've seen a couple of articles about roads with embedded inductive
charging for EVs. And there are a couple of issues that seem to me to
make these roads unfeasible. (I'm not even going to get into any of the
financial side)
My qualifications: I have a few decades experience in circuit design
and have had the word "Engineer" in my job title at several different
employers, but never went to college. So I have a lot of
"wisdom-through-experience" but there are a lot of holes in my basic
knowledge -- I tend to know a lot about the things I know, but nothing
at all about other closely related things. So I am quite willing to
accept that there's stuff going on here I simply don't understand. Feel
free to educate me. Moving along...
First: Inductive charging is basically building a transformer where the
primary is in one device (in this case, the road surface) and the
secondary is in a different device (here, an EV). Ordinarily when we
design transformers, we take great care to maximize the coupling between
the primary and secondary because loose coupling is responsible for much
of the loss in transferred power.
But in charging an EV there is necessarily going to be a considerable
air gap between the primary and the secondary. Although we can optimize
in other areas to account for this somewhat, it seems to me that there's
going to be a lot of energy lost here, mostly as heat radiated into the air.
Second: In order to transfer significant energy, there's going to have
to be some significant coupling of magnetic fields between the EV and
the road. Wouldn't this be a source of substantial drag? Effectively
the car would be driving "uphill" the whole time it's charging.

I'd expect that drag to be small. But if the car drops down a coil, to
be closer to the roadway, air drag will increase.

Post by Crash Gordon
My thought is that if we're going to be shoveling huge amounts of
electricity into a road surface, we could use it more efficiently by
building a giant linear actuator with the EV as the moving part.
Opinions?

It's a silly idea. The cost would be incredible. And we're eliminating
power plants and working towards rotating blackouts already. Imagine
adding a megawatt per mile of road.

Resonant coils can couple fairly well, even with an air gap. I think
some electric busses charge that way.

Efficiency will be low. Some of the transmitted energy will heat the
soil and rerod and car parts. And melt snow!

[Bill Sloman]

Post by john larkin

Post by Crash Gordon
I've seen a couple of articles about roads with embedded inductive
charging for EVs. And there are a couple of issues that seem to me to
make these roads unfeasible. (I'm not even going to get into any of the
financial side)
My qualifications: I have a few decades experience in circuit design
and have had the word "Engineer" in my job title at several different
employers, but never went to college. So I have a lot of
"wisdom-through-experience" but there are a lot of holes in my basic
knowledge -- I tend to know a lot about the things I know, but nothing
at all about other closely related things. So I am quite willing to
accept that there's stuff going on here I simply don't understand. Feel
free to educate me. Moving along...
First: Inductive charging is basically building a transformer where the
primary is in one device (in this case, the road surface) and the
secondary is in a different device (here, an EV). Ordinarily when we
design transformers, we take great care to maximize the coupling between
the primary and secondary because loose coupling is responsible for much
of the loss in transferred power.
But in charging an EV there is necessarily going to be a considerable
air gap between the primary and the secondary. Although we can optimize
in other areas to account for this somewhat, it seems to me that there's
going to be a lot of energy lost here, mostly as heat radiated into the air.
Second: In order to transfer significant energy, there's going to have
to be some significant coupling of magnetic fields between the EV and
the road. Wouldn't this be a source of substantial drag? Effectively
the car would be driving "uphill" the whole time it's charging.

I'd expect that drag to be small. But if the car drops down a coil, to
be closer to the roadway, air drag will increase.

Post by Crash Gordon
My thought is that if we're going to be shoveling huge amounts of
electricity into a road surface, we could use it more efficiently by
building a giant linear actuator with the EV as the moving part.
Opinions?

It's a silly idea. The cost would be incredible. And we're eliminating
power plants and working towards rotating blackouts already. Imagine
adding a megawatt per mile of road.
Resonant coils can couple fairly well, even with an air gap. I think
some electric busses charge that way.
Efficiency will be low. Some of the transmitted energy will heat the
soil and rerod and car parts. And melt snow!

John Larkin seems to be just as ignorant as Crash Gordon.

Varying magnetic fields only transmit energy when they induce current in
the soil, snow and reinforcing rods (which aren't a feature of most road
construction). Car parts might be a problem, but a car isn't designed to
be a Faraday cage, and probably won't present the sort of current loop
which could pick up much energy from the charging field.

Electric buses recharge by parking on top of the coupling loop. We
haven't had any stories about cars parking or waiting briefly on the
same spots and getting hot - the charging hardware presumably has a bus
sensor and turns off when there isn't a bus there to charge.

In-road chargers will presumably be just as smart.

[bitrex]

Post by john larkin

Post by Crash Gordon
I've seen a couple of articles about roads with embedded inductive
charging for EVs. And there are a couple of issues that seem to me to
make these roads unfeasible. (I'm not even going to get into any of the
financial side)
My qualifications: I have a few decades experience in circuit design
and have had the word "Engineer" in my job title at several different
employers, but never went to college. So I have a lot of
"wisdom-through-experience" but there are a lot of holes in my basic
knowledge -- I tend to know a lot about the things I know, but nothing
at all about other closely related things. So I am quite willing to
accept that there's stuff going on here I simply don't understand. Feel
free to educate me. Moving along...
First: Inductive charging is basically building a transformer where the
primary is in one device (in this case, the road surface) and the
secondary is in a different device (here, an EV). Ordinarily when we
design transformers, we take great care to maximize the coupling between
the primary and secondary because loose coupling is responsible for much
of the loss in transferred power.
But in charging an EV there is necessarily going to be a considerable
air gap between the primary and the secondary. Although we can optimize
in other areas to account for this somewhat, it seems to me that there's
going to be a lot of energy lost here, mostly as heat radiated into the air.
Second: In order to transfer significant energy, there's going to have
to be some significant coupling of magnetic fields between the EV and
the road. Wouldn't this be a source of substantial drag? Effectively
the car would be driving "uphill" the whole time it's charging.

I'd expect that drag to be small. But if the car drops down a coil, to
be closer to the roadway, air drag will increase.

Post by Crash Gordon
My thought is that if we're going to be shoveling huge amounts of
electricity into a road surface, we could use it more efficiently by
building a giant linear actuator with the EV as the moving part.
Opinions?

It's a silly idea. The cost would be incredible. And we're eliminating
power plants and working towards rotating blackouts already. Imagine
adding a megawatt per mile of road.
Resonant coils can couple fairly well, even with an air gap. I think
some electric busses charge that way.
Efficiency will be low. Some of the transmitted energy will heat the
soil and rerod and car parts. And melt snow!

It seems like a somewhat unnecessary technology, for the same reason we
don't have in-transit refueling tankers for cars. There are already EVs
with close to 400 mile ranges and 800 doesn't seem infeasible with
near-future technology.

Lots of expense to try to re-invent what sounds like "the electric
train." Trains hauled by electric locomotives are hard to beat for cost
per mile.

Some African countries seem to be leap-frogging over 20th century
infrastructure concepts entirely - work using videoconferencing when
possible, use WiMax and satellite for internet instead of maintaining
cable and fiber optic, do last-mile shipping via drone delivery, and
generate power on-site with micro grids rather than run high tension lines.

I never understood the right-wing refrain that "everybody wants to come
here" (the US) when it's pretty clear to me that what the majority of
people around the world generally prefer to do is stay home where they
were raised with the people and culture they're familiar with, if at all
feasible. Infrastructure is expensive, commuting can be depressing, and
most people don't like to travel very much in the first place unless
they're on vacation.

[john larkin]

Post by bitrex

Post by john larkin

Post by Crash Gordon
I've seen a couple of articles about roads with embedded inductive
charging for EVs. And there are a couple of issues that seem to me to
make these roads unfeasible. (I'm not even going to get into any of the
financial side)
My qualifications: I have a few decades experience in circuit design
and have had the word "Engineer" in my job title at several different
employers, but never went to college. So I have a lot of
"wisdom-through-experience" but there are a lot of holes in my basic
knowledge -- I tend to know a lot about the things I know, but nothing
at all about other closely related things. So I am quite willing to
accept that there's stuff going on here I simply don't understand. Feel
free to educate me. Moving along...
First: Inductive charging is basically building a transformer where the
primary is in one device (in this case, the road surface) and the
secondary is in a different device (here, an EV). Ordinarily when we
design transformers, we take great care to maximize the coupling between
the primary and secondary because loose coupling is responsible for much
of the loss in transferred power.
But in charging an EV there is necessarily going to be a considerable
air gap between the primary and the secondary. Although we can optimize
in other areas to account for this somewhat, it seems to me that there's
going to be a lot of energy lost here, mostly as heat radiated into the air.
Second: In order to transfer significant energy, there's going to have
to be some significant coupling of magnetic fields between the EV and
the road. Wouldn't this be a source of substantial drag? Effectively
the car would be driving "uphill" the whole time it's charging.

I'd expect that drag to be small. But if the car drops down a coil, to
be closer to the roadway, air drag will increase.

Post by Crash Gordon
My thought is that if we're going to be shoveling huge amounts of
electricity into a road surface, we could use it more efficiently by
building a giant linear actuator with the EV as the moving part.
Opinions?

It's a silly idea. The cost would be incredible. And we're eliminating
power plants and working towards rotating blackouts already. Imagine
adding a megawatt per mile of road.
Resonant coils can couple fairly well, even with an air gap. I think
some electric busses charge that way.
Efficiency will be low. Some of the transmitted energy will heat the
soil and rerod and car parts. And melt snow!

It seems like a somewhat unnecessary technology, for the same reason we
don't have in-transit refueling tankers for cars. There are already EVs
with close to 400 mile ranges and 800 doesn't seem infeasible with
near-future technology.

One problem with EVs is finding an available (and working) charging
slot and waiting for your car to charge. The (impractical) electrified
roadway would fix that.

More KWHs means longer charging times. I can gas up my car in less
time than it takes to squeegee the glass. And I never have to wait for
an available pump.

Post by bitrex
Lots of expense to try to re-invent what sounds like "the electric
train." Trains hauled by electric locomotives are hard to beat for cost
per mile.

Diesel-electrics?

Post by bitrex
Some African countries seem to be leap-frogging over 20th century
infrastructure concepts entirely - work using videoconferencing when
possible, use WiMax and satellite for internet instead of maintaining
cable and fiber optic, do last-mile shipping via drone delivery, and
generate power on-site with micro grids rather than run high tension lines.

Maybe that's why they are so healthy and have such low unemployment
rates and such huge GDPs. Some African citizens even have electricity
and running water.

Post by bitrex
I never understood the right-wing refrain that "everybody wants to come
here" (the US) when it's pretty clear to me that what the majority of
people around the world generally prefer to do is stay home where they
were raised with the people and culture they're familiar with, if at all
feasible. Infrastructure is expensive, commuting can be depressing, and
most people don't like to travel very much in the first place unless
they're on vacation.

Google says

Immigrants and their U.S.-born children number approximately 90.8
million people, or 27 percent of the total civilian
noninstitutionalized U.S. population in 2023. This is an increase of
approximately 14.7 million (or 20 percent) from 2010.


Some large fraction of my employees are foreign-born and seem to like
it here. You don't seem to like it here.

[Bill Sloman]

<snip>

Post by john larkin

Post by bitrex
Some African countries seem to be leap-frogging over 20th century
infrastructure concepts entirely - work using videoconferencing when
possible, use WiMax and satellite for internet instead of maintaining
cable and fiber optic, do last-mile shipping via drone delivery, and
generate power on-site with micro grids rather than run high tension lines.

Maybe that's why they are so healthy and have such low unemployment
rates and such huge GDPs. Some African citizens even have electricity
and running water.

Nobody is arguing that that they offer a better environment than the US
does now. The argument is that they don't have to get to US - or even
better - European standards of living by going through the same
intermediate stages as we did.

Post by john larkin

Post by bitrex
I never understood the right-wing refrain that "everybody wants to come
here" (the US) when it's pretty clear to me that what the majority of
people around the world generally prefer to do is stay home where they
were raised with the people and culture they're familiar with, if at all
feasible. Infrastructure is expensive, commuting can be depressing, and
most people don't like to travel very much in the first place unless
they're on vacation.

Google says
Immigrants and their U.S.-born children number approximately 90.8
million people, or 27 percent of the total civilian
noninstitutionalized U.S. population in 2023. This is an increase of
approximately 14.7 million (or 20 percent) from 2010.

The US does like hiring cheap workers from overseas. They haven't had to
feed or house them while they were growing up, or educate them.

Australia exploits immigrants in just the same way, but does better at
getting them paid them same wages as native-born citizens. Trade unions
can be good at that.

Post by john larkin
Some large fraction of my employees are foreign-born and seem to like
it here. You don't seem to like it here.

The US is a better place to live than quite a lot of countries. It now
doesn't compare well with Australian and the northern European countries
- it was more attractive when I was younger, but the median standard of
living has stagnated for the last thirty or forty years. The average
might have gone up, but so has inequality, so the median hasn't.

[bitrex]

Post by Bill Sloman

Post by john larkin
Immigrants and their U.S.-born children number approximately 90.8
million people, or 27 percent of the total civilian
noninstitutionalized U.S. population in 2023. This is an increase of
approximately 14.7 million (or 20 percent) from 2010.

The US does like hiring cheap workers from overseas. They haven't had to
feed or house them while they were growing up, or educate them.
Australia exploits immigrants in just the same way, but does better at
getting them paid them same wages as native-born citizens. Trade unions
can be good at that.

Post by john larkin
Some large fraction of my employees are foreign-born and seem to like
it here. You don't seem to like it here.

The US is a better place to live than quite a lot of countries. It now
doesn't compare well with Australian and the northern European countries
- it was more attractive when I was younger, but the median standard of
living has stagnated for the last thirty or forty years. The average
might have gone up, but so has inequality, so the median hasn't.

I've had the somewhat unusual experience of being both upper middle
class and poor in the US at different points in my life, yeah the US is
great if you're in the top 20% of incomes. There's almost always someone
available in any decent-sized metro area who'll provide best-in-class
goods and services, for a top-dollar price. As a New Englander that I
usually have the money to afford it at this point in my life doesn't
mean that I much enjoy paying it.

Being in the bottom 50% of incomes is less enticing; you tend to pay a
pretty high price for mediocre service at best, and at worst you'll
occasionally get treated pretty much like a degenerate just for trying
to get something done (as many people who've flown low-cost US airlines
or taken Amtrak or a bus can attest.)

Food is pretty expensive by world standards and there is little succor
in sight for people who rent their housing, as rental costs ruthlessly
increase. Neither political party seems deeply interested in this, they
finally answer to landlords.