
Can electric cars on the highway emulate plane-to-plane refueling? - jonbaer
https://spectrum.ieee.org/cars-that-think/energy/batteries-storage/will-electric-cars-on-the-highway-emulate-airtoair-refueling
======
jccc
Asking sincerely: Why should we not simply pull over to do this? Planes
obviously are a different situation, but cars can easily just stop.

While cool to imagine, it seems unnecessarily complicated and unsafe to do
this in motion on the road.

[Edit: The prof and his team are quite serious about it, so I assume there
must be a reason and I'm actually curious what it might be.]

~~~
willis936
It seems like a valuable proposition if we threw out the existing paradigms of
road transport.

If we throw out concepts such as ownership of vehicles and fuel and treat all
road vehicles as one system of controlled individual elements, you could
envision is a more efficient solution. Traffic jams would be lessened, trip
times would be shortened, total fuel usage would go down, etc. On road-fueling
would be one element in a world like this: road based freight delivery could
run without stopping by using vehicles expected to have short journies to
refuel the trucks along the way.

This is all to define a hypothetical new paradigm in road transport and to
quantify its potential consequences (good and bad). I had not thought about
on-road refueling before and I think there is good value in pointing it out.
We're not at the point where we're seriously charting a course to world like
this, but we need to know what the world looks like before we can start to do
that.

~~~
bdamm
Many things are valuable if we throw out the constraints of dealing with
existing reality. Even then I'm not sure it is valuable; roads suffer from
lack of maintenance already. If anything we should be looking at how to make
roads less expensive. Having autonomous vehicles disperse their weight to
reduce prevalence of potholes, for example.

~~~
willis936
Right, and that is one thing to weight for when choosing the behavior of the
system. While the article in question doesn't explicitly say this, I think
these seemingly impractical solutions add to the theoretical toolkit that we
can use to shape a road utopia, if society ever agrees on what that would look
like. If society does ever agree on a road utopia and then consider it
worthwhile to pursue, it will be valuable to have these ideas laid out.
Perhaps they are useless today, but they motivate this idea. If they weren't
proposed then the possibility of a future road utopia is entirely impossible.

------
ashtonkem
Why bother? With top line EV ranges reaching close to 400 miles, after that
amount of time _I_ need to get out of the car. If you want people to be able
travel huge distances cleanly without stopping, then what you’re actually
looking for is a train.

~~~
willis936
What about an autonomous semitruck that could run 24 hours a day except for
unloading/reloading cargo, refueling, and maintenance?

~~~
ashtonkem
Trains. The fact that long haul semi trucks are a thing is a failure of
infrastructure.

Edit: as some have pointed out, it’s more a failure of policy.

~~~
willis936
Trains are large and inflexible. Short of having a city-block resolution
freight train network at every population center, you'll need something
flexible for the last mile of delivery.

~~~
ashtonkem
You’re misunderstanding.

The only reason why you’d need on-road recharging for hypothetical autonomous
semi trucks is if they’re regularly traveling outside the range of their
batteries, which is probably in the 400-500mi range.

In a well designed infrastructure system, that shouldn’t happen often. Instead
the hops of hundreds of miles should be handled by trains, leaving semi trucks
for the last dozens of miles from train hub to area of need.

Some long haul trucking will happen, but it should be a slim minority of
cases.

~~~
dsfyu404ed
Adding an extra step (rail hub to short haul truck transition, potentially at
both ends of the trip) adds cost. This cost is (and will be for the
foreseeable future) less than having the less efficient semi-truck do the
entire trip at least for the kinds of loads that are currently carried by
semi-truck. JIT inventory systems also don't play nice with rail.

~~~
ashtonkem
Semi trucks are cheaper because they receive a $125B+ yearly subsidy in the
form of road maintenance. Semi trucks do 99% of the damage to our public
roads, but only pay 35% of the cost.

I suspect that rail would be much more price competitive if we took that
subsidy away.

You’re right about JIT, but we’re also seeing the downsides of JIT
infrastructure during this pandemic. I suspect that we’ll see a push for more
redundancy in our supply chain for reasons completely unrelated to trucks vs.
trains.

~~~
slavik81
Assuming we're resurfacing our roads once every 5 years, if we banned trucks
it would take 100x longer to accumulate the same amount of damage, so we'd be
able to resurface only once every 500 years?

I would expect there to be a significant amount of damage done just by the
elements, independent of usage.

~~~
ashtonkem
There’s also the fact that roads are built up to trucking standards. Without
trucks the roads would be thinner, reducing cost and pollution (concrete is a
major source of CO2).

~~~
throwaway0a5e
Roads are mostly made from asphalt and mother nature would still destroy them
in well under 100yr in most places.

~~~
ashtonkem
Highways are much more relevant when we’re talking about trucking, and
highways are largely concrete.

~~~
throwaway0a5e
This is utterly false and in a trivially verifiable way in this age of street
view.

Raised highways sometimes have concrete decks because the strength can be
attractive but the overwhelming majority of highways are asphalt. At or below
grade highways are almost always asphalt. Tunnels are often concrete but those
are a vanishingly small minority of miles.

~~~
wahern
AFAIU, the original Interstate Highway System was all concrete. These days
states usually resurface heavily trafficked segments with asphalt (of various
varieties) atop the old concrete. Apparently, at least as of 2006 60% of the
system was still concrete pavement:
[https://pubs.usgs.gov/fs/2006/3127/2006-3127.pdf](https://pubs.usgs.gov/fs/2006/3127/2006-3127.pdf)
Which is not surprising as IME long segments of the IHS are often still
concrete pavement, especially in the South and West; it's only in urban areas
where asphalt surfacing seems ubiquitous.

I'm not sure how new segments are built today, but they may very well still
use concrete underlayment, or at least something more substantial than loose
aggregate. Road tech these days is way more complicated than just concrete v.
asphalt. I would _guess_ that for remote segments, and given the load
requirements, it may still be cost effective to keep using concrete surfacing.

------
ppod
Maybe special powerful cars that are constantly charged could drag others
along a fixed line in a kind of "train".

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patall
Can anyone explain what happened to battery swapping. A few years ago there
was this Tesla show where they swapped three cars in the time it took to
refuel a normal ICE automotive. But after that nothing happened.

I know it is difficult to handle when you do not own the battery but I would
guess 90% of private long distance trips are return trips, so you could swap
batteries at your trusted former gas station every 200 miles and then on the
way back home do the same and get your old battery back at your last stop and
keep that pack for all your short day to day trips. But somehow, this idea
seems to be 100% abandoned.

Edit: Follow up conspiracy: Could it actually be because the battery is the
one component of an EV that degrades the fastest and thus cars would last much
longer (and no manufacturer would want that) if you could just swap the main
battery every 100.000 miles or so?

~~~
NickM
It was abandoned because fast charging stations keep improving, and are much
simpler and cheaper to operate than battery swap stations. It's already at the
point where you can take a 400-500 mile road trip in a Model 3 with maybe a
single twenty minute charging stop, which is just not that much extra time,
and most people like to take a short break every few hours anyway.

I suspect Tesla knew this would probably happen, but IIRC there was a rule for
a while with the California ZEV credit program where manufacturers qualified
for extra credits if a vehicle could be "refueled" in under five minutes.
Tesla set up a single swapping station to prove it could be done and therefore
qualify for the extra credits, but it was always kind of inconvenient and
expensive and very few people actually used it.

~~~
ianai
I’d still like to be able to tow a battery behind me for extended trips.

I don’t know how running the AC impacts range, I would like to know. Places
with extreme weather and major population centers can make an otherwise short
drive really taxing on resources through ac use or just being stuck in place
for extended periods of time. Like how peak LV traffic can turn a 15 min drive
into a 50 minute drive in 120f+ heat.

Tow-able batteries would make wide use cases like apartments more viable too.

Edit-typo

~~~
frosted-flakes
That seems like a fantastic idea. This way, the car's internal battery can be
smaller and lighter for day-to-day use (and therefore more efficient), and
whenever longer range is needed you can just rent a fully-charged tow-a-
battery, which you can swap out like propane tanks, or recharge yourself at
home. These tow-a-batteries would work with any electric car with standard
secure hook-ups.

Since these batteries would be rather expensive, I imagine that you would have
to pay a refundable deposit to the tow-a-battery network (Shell, Esso, etc.)
that covers the full cost of the tow-a-battery in order to rent one.

The biggest down-side is that a rear-end crash could be rather dangerous. I
don't see a way around that without making the tow-a-battery a vehicle in
itself.

~~~
leetcrew
by the time you've added enough protection (ie, extra mass and drag) to the
towed battery, it seems like you would be pretty deep into diminishing
returns. a large amount of the extra energy would be spent on moving the
trailer itself.

~~~
ianai
Not really. Yes batteries add lots of weight. But electric motors have lots of
torque and are known to climb hills easily. Like how Tesla’s forthcoming truck
can tow up to 14000 pounds. I’m not doing the calculus, but I suspect the
power characteristics of electric motors more than make up for a towable
battery.

Edit-here’s an article about a company doing this

[https://electrek.co/2020/02/19/french-startup-proposes-
batte...](https://electrek.co/2020/02/19/french-startup-proposes-battery-
trailers-as-ad-hoc-ev-range-extenders/)

~~~
leetcrew
energy, not power. I'm sure the motors have enough torque to tow the battery,
what I'm doubting is how efficiently that extra battery capacity gets
converted to range.

as an aside, the cybertruck is (probably) pretty bad at towing. see this video
for an interesting argument:
[https://www.youtube.com/watch?v=S4W-P5aCWJs](https://www.youtube.com/watch?v=S4W-P5aCWJs)

~~~
renewiltord
Very slow video. Wish it were transcripted.

------
nullsmack
Why not just have overhead lines that you can attach to when you need a
charge? Do it like the street cars. Or have something like a railroad you can
drive up onto and then it charges you while you're traveling over it.

------
munsters
This seems like it would only work if you're able to stay bumper to bumper
with the charging car for 30+ minutes. You'd have to be traveling a very long
distance along the same route (and, the charging car's destination MUST be
before it runs out of power after transferring its power). What are the odds
of that happening, on a reliable basis? At that scenario, it seems more
sensible to install overhead wires (or underground) along freeways for long
distance travel.

------
zackkatz
This reminds me of old Popular Science magazines promising a future of
unrealized technology.

I do not think this is the future. But it’s something I’d like to see in a
sci-fi movie.

------
viburnum
Replacing highways with trains for most trips is more sustainable.

------
spiritplumber
I think it's called a train...

------
bob33212
The only good options are:

1\. Make much more rapid charging possible on the cars much closer to the
interstate. 2\. Add a electrified metal rail to the road so that the cars can
charge like a subway car.

------
letitbeirie
Emulating plane-to-plane refueling entails all sorts of system dynamics
problems because of the untrained human driver in the mix.

Wouldn't it be a lot easier (and likely cheaper in the long run) to emulate
overhead line-to-train power transfer?

Seems like "transfer of electricity into an (ideally) land-bound vehicle from
its infrastructure" would be a more closely related problem than "transfer of
fluid from one airborne aircraft to another."

------
Someone
I think [http://eptender.com/en/battery-
tender-2-2](http://eptender.com/en/battery-tender-2-2) (renting a battery in a
small trailer to extend a car’s range, potentially dropping it off at a
different place from the one you picked it up) has more chance of succeeding
In the market.

------
toss1
I've been thinking for years that fully-automated platooning / drafting should
be a good option for self-driving cars. Run it via an app, cars make
themselves available for drafting, others nearby sign up, they all line up and
save energy. Could be a nice feature for Tesla, or a competitor, to augment
the value of being in their network.

Obviously, this would rely on both self-driving and car-to-car communications
to ensure simultaneous braking, acceleration, etc. to avoid accordion effect
and chain-reaction collisions.

Charge-sharing as in this article could be a nice addition too. Also seems
most plausible to automatically pay for shared charge in credits of some sort,
or cash through the app. My biggest question is whether the shared charge
would be sufficiently useful in comparison to the cost/maintenance of the
extra moving parts. Seems like induction power&charging in sections of road
could be more effective.

------
pjkundert
One of the next obvious steps for self-driving vehicles is “flocking” or
drafting; this is an almost trivial problem once two or more vehicles are
autonomously locked within a few inches of each other.

~~~
jstanley
If you have a car only a few inches behind you and you spot a problem and need
to emergency brake, you can't actually start braking until the car behind has
started braking, otherwise the car behind will crash into the back of you.

If you have 3 cars in a row, and the first car spots a problem, it can't start
braking until after the 2nd car has started, but the 2nd car can't start
braking until after the 3rd car has started.

It gets linearly more dangerous as more cars are added.

Not saying it can't be done, but the problem is more subtle than just working
out how to stop the cars from crashing into each other at speed: they also
need to be able to brake in emergencies without crashing into each other.

Possibly the way to do it would be to mechanically couple the cars like a
train, so that it is safe for the one in front to start braking earlier than
the one behind, albeit with reduced performance.

~~~
cheerlessbog
The idea is predicated on autonomous control and presumably the vehicles
communicate in real time...they all brake together at the delta V of the least
capable member.

~~~
jstanley
The "real time" control loop between the sensor on one car and the brakes on
the same car is much tighter than that between the sensor on this car and the
brakes on another car and then feedback from the other car that braking has
started.

I don't actually know how long it takes between the computer deciding to brake
and the car actually starting to slow down, but I expect you can't just throw
out a message saying "I'm braking immediately" and start braking without any
kind of confirmation that the message was received, and expect it to be OK.

But maybe you _can_ afford to wait for a confirmation? The speed of light is
pretty fast, and you're not transmitting that many bytes.

Especially if you consider that a human could easily take 200 milliseconds to
react to something even if it's _really_ paying attention. You could request a
braking confirmation from the other side of the Atlantic and still come out
ahead!

~~~
adav
There could be some leeway to initiative braking on following cars quicker
with control loop similar to existing emergency brake assist systems [1].
These currently apply the brakes quicker and more powerfully than a driver’s
foot when the car thinks it’s in an emergency situation. The same signal could
be sent to following cars by the time the driver sufficiently engages the
pedal.

[1]
[https://en.wikipedia.org/wiki/Emergency_brake_assist](https://en.wikipedia.org/wiki/Emergency_brake_assist)

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jsjohnst
I see no problems at all with being magnetically coupled via an extended probe
to another car transferring high voltage and/or current while driving at
highway speeds, none what so ever...

------
nicoburns
Wouldn't it make more sense to build the charging into the road?

~~~
umvi
We could make the road out of interlocking hexagonal solar panels

~~~
cheerlessbog
This was done as you probably know [1] but it's not clear that the road
surface is a good place for solar panels. They get dirty and damaged. It's
certainly orthogonal to charging vehicles on the road, given we know how to
transmit power already.

[1]
[https://www.google.com/amp/s/www.theverge.com/platform/amp/2...](https://www.google.com/amp/s/www.theverge.com/platform/amp/2016/12/22/14055756/solar-
panel-road-electricity-france-normandy)

~~~
cheerlessbog
Indeed [2]

BTW when searching on Google it is quite obnoxious that it doesn't navigate to
the actual URL but instead prefixes it with Google..

[2]
[https://www.google.com/amp/s/www.businessinsider.com/first-s...](https://www.google.com/amp/s/www.businessinsider.com/first-
solar-road-france-failure-photos-2019-8%3famp)

------
simonblack
Why do that?

Incorporate a charging loop into the road.

Better still, throw away those heavy and toxic batteries and just collect the
car's power directly from the road.

~~~
PhantomGremlin
What's the efficiency on something like that?

What's the cost of tearing up every single highway in existence to add a
charging loop?

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mmaunder
I’m assuming very high power transmission in short period of time. Thus
moderate amps and very high voltage or you’ll need thick cables.

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lmilcin
Seriously doubt fast charging a battery of running car from battery of another
running car.

