Heated exoskeleton?

[cybrtrk_maybe]

Another thing to consider is that, just a little ice on the leading edge of an airfoil (wing), can change the aerodynamics enough to bring an airplane down. I would also think that it would interfere with the efficiency of the CT while driving to have any snow/ice protruding from its surfaces.

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[Bigfoot DeLorean]

Another thing to consider is that, just a little ice on the leading edge of an airfoil (wing), can change the aerodynamics enough to bring an airplane down. I would also think that it would interfere with the efficiency of the CT while driving to have any snow/ice protruding from its surfaces.

I thought the issue was weight with an airplane...never thought about aerodynamics. Makes sense. But for a land vehicle, I doubt it would make a material difference in performance - going off of my 35 years of driving in Chicago winters with many vehicles that had ice frozen to the hood.

 

[Bigfoot DeLorean]

It takes a ton of energy to melt a ton of ice in a day. A ton is 12,000 BTU/H which is 12000/3412 = 3.517 kW. Thus it would take 84 kWh of battery to melt a ton of ice.

it doesn’t have to melt all the ice (which would be far from a ton), just melt the connection between the ice and the steel. The ice would slide off. My Range rover has a heated windshield, and every car I’ve owned in the past 15 years has had heated mirrors. Given that the frunk lid isn’t that big and the intermittent need, I can’t see energy being an issue considering people are talking about using the CT to power their house, power tools, charge an atv, etc.

The windshield will defrost. Where it would be useful to me (and anyone else who may park outside in snow) is the front hood, roof, doors and vault cover. The roof might be covered by heat transfer from basic hvac, although it wouldn’t be difficult to put heating elements into/on the glass itself (might even be required). If there’s heat in the vault, that MIGHT take care of that part, which is the largest horizontal surface, except in really frigid temps. But given the complexity of the vault door, I’d don’t think I’d add a heating element to it unless it was as durable as the vault door itself.

The side doors would benefit greatly, as a freezing rain on stainless could coat handles and prevent truck access. Even if only in key areas (see what I did there?).

Stainless conducts heat, adding a cold weather defrost option would be something I’d definitely scrape up extra shekels for.

 

[cybrtrk_maybe]

I thought the issue was weight with an airplane...never thought about aerodynamics. Makes sense. But for a land vehicle, I doubt it would make a material difference in performance - going off of my 35 years of driving in Chicago winters with many vehicles that had ice frozen to the hood.

It would be easy enough to verify. Have someone with an EV drive a course of about 100 miles. Add a bunch of suction cups to the exterior to simulate a non-smooth surface. Drive the same route and compare the energy used.

 

[ajdelange]

it doesn’t have to melt all the ice (which would be far from a ton),

It has to melt all the ice it has to melt. At 84 kWh per ton. Scale that to however much ice you think it has to melt.

I thought the issue was weight with an airplane...never thought about aerodynamics.

It's the drag. I recall a very unpleasant night over the Appalachins. So bad the controller wanted to know why my groundspeed was slow. On that paticular occasion it was sublimation that eventually got rid of it (deicing on a small plane is too expensive just as it would be on these trucks). And I guess sublimation will be how we shed it on our trucks too.

And in a BEV that drag will definitely show up on your power meter. Even a wet road surface does. Extra heat taken from the battery to melt it off will only show up as more Wh/mi consumed.

 

[rr6013]

I live in the northwestern PA with my truck is always parked outside and this thought has never crossed my mind. What function would that serve? Just curious.

(Now I see some benefit for a heater for the door (and/or handle), but the whole body?)

In the high desert, mountains and Midwest there is icing. In UT they have a word for it " black ice" which is an atmospheric humidty that freezes. In Santa Fe freeze rain falls during the night so by morning all door gaskets are frozen even the door handles need thawing. Midwesterners are familiar with sleet and freezing rain that turns to ice. By far the nastiest is the Santa Fe to unthaw. Black ice the most dangerous driving but easily breaks when opening doors. Midwest freezes are just PITA.

So door handle and gasket heat strips would do the job.

 

[Geo]

You guys got me thinking about the opposite problem.

The removal of heat from the exoskeleton.

Melbourne weather is fairly moderate, but it can get to 45 degrees Celsius (113 f) and the heatwaves of 4 or 5 consecutive days of 35 + deg Celsius (95 f) are happening more often. Also now the temp’s in the nights are staying above 22 deg (72 f) so not much reprieve.

Forget frying an egg on the sidewalk,
Your’re going to be able to Teppanyaki BBQ on the Cybertruck bonnet !

As a massive heat sink, seriously won’t the Cybertruck become dangerously hot to the touch if nothing else ?

Can Tesla tap the heat to transfer it and power the battery a little ?

 

[ajdelange]

Well its going to get hot, no doubt about that. Not so hot as a mild steel skin painted black or dark blue but hot for sure. But that heat load is going to be small compared to the heat load through all that glass (check the video here of Musk and Leno in the CT). Also note that as soon as you get moving the skin temperature will be reduced to the OAT which, even though that be 45 °C, is cooler than the skin temp when the truck is parked in the sun.

Don't know how it goes in Victoria but in the Centre even though the nightime air temperatures are in the 20's the sky temperature is only a few Kelvins so you get tremendous radiative cooling (try jumping in the pool first thing in the AM even in January).

The big implication of solar load in the summertime in the desert is demand on the heat pump. Can it get rid of the battery, inverter and motor loads and still have enough capacity to cool the cabin? There are reported incidents in the US with the current models where the answer to that has been "No". You all may be back to specifying distances in "water bags" down there.

 

[Geo]

Well its going to get hot, no doubt about that. Not so hot as a mild steel skin painted black or dark blue but hot for sure. But that heat load is going to be small compared to the heat load through all that glass (check the video here of Musk and Leno in the CT). Also note that as soon as you get moving the skin temperature will be reduced to the OAT which, even though that be 45 °C, is cooler than the skin temp when the truck is parked in the sun.

Don't know how it goes in Victoria but in the Centre even though the nightime air temperatures are in the 20's the sky temperature is only a few Kelvins so you get tremendous radiative cooling (try jumping in the pool first thing in the AM even in January).

The big implication of solar load in the summertime in the desert is demand on the heat pump. Can it get rid of the battery, inverter and motor loads and still have enough capacity to cool the cabin? There are reported incidents in the US with the current models where the answer to that has been "No". You all may be back to specifying distances in "water bags" down there.

I did notice the glass in the video, and all that great light it baths the cabin in.
I was hoping it was Electro chromatic glass. Cos yes, the heat in the cabin is also going to be a big problem that needs addressing.

I hope your're right, but I can't help thinking that, that is a lot of mass in the exoskeleton to absorb heat with, so I doubt the Cybertruck will be less hot that a normal car panel painted black.

I hope Elon does more than a few laps around Death Valley to ensure the HVAC can cope, but Im not sure how they are going to address the passive head load on the exterior. I was hoping they could turn it into a positive and tap into it as a little power source.

P.S. Yes, I know relatively speaking its only a small increase in Kelvins, but we life forms here on the ground are very sensitive to just a 2% or so difference in Kelvins.
At 308 Kelvins or so, I don't want to be parking somewhere and grilling little kids as they walk past !

 

[Newton]

Stainless is really quite good at retaining heat. It will get very hot and stay hot for quite a while. More than bare sheet metal steel...Perhaps less max heat than a dark painted sheet steel, maybe not , I dont know the physics of it..but it will retain the heat longer. I wonder if that can be put to use.

 

[ajdelange]

What I meant was that out where there is no humidity the temperature of the sky is very low - a few Kelvins. Something that is around 300 K such as a warm car or the water in a swimming pool will radiate lots of heat to it and cool quickly.

 

[ajdelange]

Stainless is really quite good at retaining heat. It will get very hot and stay hot for quite a while. More than bare sheet metal steel...Perhaps less max heat than a dark painted sheet steel, maybe not , I dont know the physics of it..but it will retain the heat longer. I wonder if that can be put to use.

The rate of radiative heat loss or gain depends on the emissivity of the surface. Something that is silvery has very low emissivity and something that is black has high, Thus of two sheets of metal the one with the more silvery surface will reflect most heat directed at it. The absorption depends more on the color than the material.

But the rate of temperature change per unit of heat absorbed depends on the material. Mild steel and stainless steel have specific heats that are pretty close. 510.8 and 502.4 j/(kg-K) respectively (304 stainless) and thus both will absorb and retain heat for about the same time if the same thickness and painted the same color.

 

[Newton]

The rate of radiative heat loss or gain depends on the emissivity of the surface. Something that is silvery has very low emissivity and something that is black has high, Thus of two sheets of metal the one with the more silvery surface will reflect most heat directed at it. The absorption depends more on the color than the material.

But the rate of temperature change per unit of heat absorbed depends on the material. Mild steel and stainless steel have specific heats that are pretty close. 510.8 and 502.4 j/(kg-K) respectively (304 stainless) and thus both will absorb and retain heat for about the same time if the same thickness and painted the same color.

I was talkin to a Mechanical engineering student friend. He was saying becuase its so much thicker it should be able to get hotter. Is this true?

 

[DMC-81]

Bare stainless gets very hot in the summer sun. I have "Do Not Touch" signs that I display on my DeLorean at car shows. Everyone wants to touch the bare surface, and my sign is not necessarily to ward off fingerprints, but to try and prevent someone burning their hand.

 

[ajdelange]

I was talkin to a Mechanical engineering student friend. He was saying becuase its so much thicker it should be able to get hotter. Is this true?

Note that the units of specific heat are J/(kg-K). Thus a more massive piece of steel will hold more heat and, for a given emmissivity and temperture differential, cool and heat more slowly than a less massive one.