If a "cyber" styled vehicle is marketed towards the small city driving segment (where efficiency at highway speeds, and thus Cd, is less relevant) it might be fine if the Cd is over 0.3. This won't be too popular in NA but could be a valuable segment in Europe and Asia, especially if it is much cheaper because of it. Plenty of people bought Nissan Leafs and BMW i3's even in the US, so this is a viable segment to go after.
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All engineering topics (out of main)
- Thread starter Artful Dodger
- Start date
The increase in drag needs to be traded off against the reduction in production costs and longevity of car (which makes the car more valuable).
The long taper was needed for a pickup bed. I also think that this V1 is very unlikely to be the endpoint of design. Tesla has shown the ability to make rapid progress is design + manufacturing when they apply in certain directions.
I’m assuming that they will be able to make more complex bends over time. Plus they could reduce drag (and increase manufacturing complexity) by having composite aero panels in certain locations.
The long taper was needed for a pickup bed. I also think that this V1 is very unlikely to be the endpoint of design. Tesla has shown the ability to make rapid progress is design + manufacturing when they apply in certain directions.
I’m assuming that they will be able to make more complex bends over time. Plus they could reduce drag (and increase manufacturing complexity) by having composite aero panels in certain locations.
Agree, but I think the 3rd Gen arrives in about half that time (3-4 yrs). Tesla has already published the patents for that generation. They will implement die-cast stainless steel metal-foam unibodies to replace the 'crude-but-fast' origami-style folded SS sheet hulls seen on Cybertruck.
Metal foam SS has just 1/6th the weight but all the strength of sheet SS, while retaining the advantage of not requiring separate Stamping/Body/Paint processes for production. In fact, these body Gigafactories can be placed closer to raw materials now, since they will be more automated and simpler to produce. Maybe we'll need 'Giga-Foundries'?
Gen 4 is interesting. In about a decade, Li-Ion bty tech may advance so much that Tesla can place bty electrolyte in the voids in the metal-foam matrix of the body, which structure is already electrically conductive, making the body become the energy storage and distribution medium.
Logically (by extension), Gen 5 goes on to embed solar cells on the outer / exterior surface of the SS die-cast body, so that only the anode is an additional material, while the solar cell's cathode is shared with the bty/body that already exists. Just park it in the Sun, and it charges itself. Need a fast charge? Lasers, tuned to the solar cells band gap. Advantage? Charging while in motion (though I will not talk about Tesla Aviation here).
People constantly overestimate what Tesla can do in the short term (1-2 yrs), while underestimating what they can do in the long term (5-10 yrs). This is a 50 yr plan. Jus' sayin'.
This is the music I grew up with. I remember these lyrics, written back in 1974, when SkyLab was a thing:
We're flyin' spaceships 'round the stars,
getting faster by the hour
Pretty soon we'll be on Mars,
build another ivory tower
Through all the praise that you borrow,
there's still hunger and sorrow
And then after it's all said and done
Though we've come a long, long way,
this old world's not much better than it was
getting faster by the hour
Pretty soon we'll be on Mars,
build another ivory tower
Through all the praise that you borrow,
there's still hunger and sorrow
And then after it's all said and done
Though we've come a long, long way,
this old world's not much better than it was
Let's keep working to make it better.
Cheers!
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JRP3
Hyperactive Member
I don't ever see a future where putting high voltage in the exterior skin of a vehicle makes any kind of sense.
Agree, but I think the 3rd Gen arrives in about half that time (3-4 yrs). Tesla has already published the patents for that generation. They will implement die-cast stainless steel metal-foam unibodies to replace the 'crude-but-fast' origami-style folded SS sheet hulls seen on Cybertruck.
Metal foam SS has just 1/6th the weight but all the strength of sheet SS, while retaining the advantage of not requiring separate Stamping/Body/Paint processes for production. In fact, these body Gigafactories can be placed closer to raw materials now, since they will be more automated and simpler to produce. Maybe we'll need 'Giga-Foundries'?
Gen 4 is interesting. In about a decade, Li-Ion bty tech may advance so much that Tesla can place bty electrolyte in the voids in the metal-foam matrix of the body, which structure is already electrically conductive, making the body become the energy storage and distribution medium.
Logically (by extension), Gen 5 goes on to embed solar cells on the outer / exterior surface of the SS die-cast body, so that only the anode is an additional material, while the solar cell's cathode is shared with the bty/body that already exists. Just park it in the Sun, and it charges itself. Need a fast charge? Lasers, tuned to the solar cells band gap. Advantage? Charging while in motion (though I will not talk about Tesla Aviation here).
People constantly overestimate what Tesla can do in the short term (1-2 yrs), while underestimating what they can do in the long term (5-10 yrs). This is a 50 yr plan. Jus' sayin'.
This is the music I grew up with. I remember these lyrics, written back in 1974, when SkyLab was a thing:
We're flyin' spaceships 'round the stars,
getting faster by the hour
Pretty soon we'll be on Mars,
build another ivory tower
Through all the praise that you borrow,
there's still hunger and sorrow
And then after it's all said and done
Though we've come a long, long way,
this old world's not much better than it was
Let's keep working to make it better.
Cheers!
Exactly!
A tad bit more seriously. I think it is hard to estimate the rate of change of technological process generally. Especially when non linear.
I think Tesla is applying improving practical uses and better integrating multiple technologies at a much faster scale than any other automaker.
I think Tesla is applying improving practical uses and better integrating multiple technologies at a much faster scale than any other automaker.
bhtooefr
Active Member
You are thinking of reactive armour. Very nasty surprise for dismounted infantry. Cybertruck will obviously be easily outfitted with such. 3rd Party suppliers are likely already receving inquiries.
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Lol, what makes you think there would be HV in the exterior skin? Individual solar cells are commonly 0.6 volts, and arranged in series for the desired voltage. With current Li-Ion chemistry, they would need to provide ~4.5 volts to charge an individual cell. The high voltage is collected with wiring embedded deeply inside the vehicle's hull. No more dangerous than a current HV traction pack that is vulnerable in an accident. Individually fused strings of cells has been a thing for a long time.
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JRP3
Hyperactive Member
Except with an actual direct connection to the exterior of the vehicle. If the body is the energy storage medium as you posted it has to be able to deliver full voltage and current, and if it's shorted to the outside world that's what it will do.
solar cell string > zener diode > bty balance lead
My cheapo Canadian Tire solar controller had one 20 years ago. Jus't sayin'. Solutions exist or can be created. That's what engineers do.
JRP3
Hyperactive Member
I don’t know when or if we’ll see metal foam structures for cars. Composite structures are used in aviation and limited production cars that need to be lightweight though. Volume production is challenged by the long cure time so I’m not aware of any volume car that uses it for structure. Perhaps Tesla will come up with some innovations on that front.
Here’s a pretty good article focused on increasing use of carbon-fiber reinforced plastics in cars.
https://www.livescience.com/53995-carbon-fiber-may-finally-be-coming-to-cars-everywhere.html
Here’s a pretty good article focused on increasing use of carbon-fiber reinforced plastics in cars.
https://www.livescience.com/53995-carbon-fiber-may-finally-be-coming-to-cars-everywhere.html
Brando
Active Member
side note: Why would Model 3 be the smallest vehicle Tesla ever makes?
Because Model 3 is probably the smallest a useful RoboTaxi could be, right?
Because Model 3 is probably the smallest a useful RoboTaxi could be, right?
Fact Checking
Well-Known Member
Good - going full heat pump cycle should improve cold climate range significantly, even with the same battery pack. The resistiance heater really hurt winter range in some tests.
The problem is that heat pumps not only lose efficiency with increasing dT, but also lose output power. Great for marginal temperature differences, not so much for huge temperature differences (where they matter the most). I've never heard of a car heating system that's able to run without any resistive heater. There has to be a resistive element somewhere.
A guess (if this leak is correct): the inverter in the drive units is the resistive heating, when run in "hold position and just burn power" mode. Heat is pumped from this loop up to cabin-heating temperature.
Would need to be rapidly responsive; you can't make people wait for the full battery loop to heat up before giving them meaningful cabin heat. The battery heating loop would surely need to be shut off / flow limited. Still would likely be laggier than a PTC heater.
To reiterate, in severe weather, the impact of adding a heat pump is marginal; it's most impactful in low-dT conditions, e.g. "cool but not very cold" weather. E.g. Iceland much of the year.
Particularly when car-camping (e.g. when almost all of your energy consumption is from the heater)If this is the new system, it's a shame I won't get it; my Model 3 is likely already produced (or will be soon), while who knows how long it will take for this tech to migrate to the Model 3. Although even more than that, I'd rather be rid of the 12V, which is supposedly another MY change that was discussed previously (although not confirmed recently)
But oh well. All Teslas keep improving after you buy them, and that's the whole bloody point. They'll have something new awesome right after this. And something right after that.As a side note: the sheer number of people leaking things about MY lately, including pictures, sure makes it seem likely that something is afoot for later this quarter. I hope people's expectations on volumes aren't excessive, of course.
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Fact Checking
Well-Known Member
(Markets will be closed in the U.S. today - so I guess this still qualifies for a weekend OT exception?)
ΔT indeed needs to be low, but it's compared against absolute temperatures measured in Kelvin.
I.e. if we take the theoretical maximum efficiency of a heat pump:
Where Tc and Th are the two sides. If we take -20°C external Icelandic air (253K) and want to pump it to +20°C cabin air temperature (293K), a 40K gap, then the theoretical maximum COP ratio of the heat pump is still 263/40, over 600% - much higher than good-weather practical COP of heat pumps which is typically around 300%.
I believe the reason most air based heat pumps have low efficiency in cold weather isn't just heat pump inefficiency at higher ΔT (which is undeniably a factor), but technological limitations such as icing on the heat-exchanger, which force frequent "defrost" cycles, or the poor cold weather performance of the coolant.
There are heat pumps that work very well in cold weather, for example a particularly clever variant is trans-critical CO₂ based heat pumps - unfortunately, last I checked them (a decade ago ...) they were patented by a German company who makes geothermal heat pumps. In geothermal applications it's particularly useful to have CO₂ as your heat pump medium: the ~100m deep bore holes are very long and hard to access, and with CO₂ the coolant gas simply leaves. This is much better than glycol based (double) coolant loops in traditional geothermal heat pump systems.
Incidentally the ID.3 apparently has a CO₂ based heat pump:
I believe Mercedes also has CO₂ based heat pumps too. Maybe CO₂ heat pumps are out of patent protection already?
To reiterate, in severe weather, the impact of adding a heat pump is marginal; it's most impactful in low-dT conditions, e.g. "cool but not very cold" weather. E.g. Iceland much of the year.
ΔT indeed needs to be low, but it's compared against absolute temperatures measured in Kelvin.
I.e. if we take the theoretical maximum efficiency of a heat pump:
Where Tc and Th are the two sides. If we take -20°C external Icelandic air (253K) and want to pump it to +20°C cabin air temperature (293K), a 40K gap, then the theoretical maximum COP ratio of the heat pump is still 263/40, over 600% - much higher than good-weather practical COP of heat pumps which is typically around 300%.
I believe the reason most air based heat pumps have low efficiency in cold weather isn't just heat pump inefficiency at higher ΔT (which is undeniably a factor), but technological limitations such as icing on the heat-exchanger, which force frequent "defrost" cycles, or the poor cold weather performance of the coolant.
There are heat pumps that work very well in cold weather, for example a particularly clever variant is trans-critical CO₂ based heat pumps - unfortunately, last I checked them (a decade ago ...) they were patented by a German company who makes geothermal heat pumps. In geothermal applications it's particularly useful to have CO₂ as your heat pump medium: the ~100m deep bore holes are very long and hard to access, and with CO₂ the coolant gas simply leaves. This is much better than glycol based (double) coolant loops in traditional geothermal heat pump systems.
Incidentally the ID.3 apparently has a CO₂ based heat pump:
VW will roll out CO2 MAC in new electric car series
"German car manufacturer Volkswagen will opt for CO2 mobile air-conditioning (MAC) systems in another series of cars by the end of 2019 – its electric car ‘ID’ series"
"German car manufacturer Volkswagen will opt for CO2 mobile air-conditioning (MAC) systems in another series of cars by the end of 2019 – its electric car ‘ID’ series"
I believe Mercedes also has CO₂ based heat pumps too. Maybe CO₂ heat pumps are out of patent protection already?
This is the problem; real-world heat pumps aren't just limited by the Carnot limit; they're far from the Carnot limit, and get further away the more dT grows. A typical real-world heat pump's CoP curve may look something like this:
But more important than the dropoff in CoP is the dropoff in power output. You have to do more work, and simultaneously, you do it less efficiently. This is all entirely independent of technological limitations such as icing on the heat exchanger.
It would be lovely if we could match the curve for a perfect Carnot cycle with a small heat pump for a car, but we can't, or even get that close to it.
The problem is worse when you try to use the same compressor to be both AC and heating. dT for cabin cooling is unlikely to be more than -15 - -20°C. But for cabin heating can be more than +40°C. So in heating mode it not only has to do more work, it does so much less efficiently. But the compressor doesn't get more powerful just because you're using it in heating mode. The question then becomes: how big, heavy, and expensive of a heat pump do you want to include to make up for this fact?
As noted though, if Tesla is combining it with resistive heating from the drive units, they can bypass these power output limitations.
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