Re: A couple of problems with EV charging roads?

On Tue, 4 Jun 2024 01:35:13 -0400, bitrex <user@example.net> wrote:

On 6/2/2024 1:51 PM, john larkin wrote:

On Sun, 2 Jun 2024 12:32:25 -0500, Crash Gordon <uucp@crashelex.com>
wrote:
 

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.
 

>
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.

>
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?

>
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.

>
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.