Stainless Steel in Hot Sun

JBee

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The car heating up while parked is the sole reason for having a solar panel roof on the Prius.
That solar panel ran the interior fan to keep the temperature the same as the outside but not allow it to heat up more. That meant you'd save some gas once you got in to drive away, because it didn't have to run the AC flat out to get car temperature down.

Do Teslas have a option to run just the ventilation fan to do that? I'd assume that will use a bit less power, and would only be a software update away to get it to work?
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ajdelange

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We have Vent which "cracks" the windows but I don't think the fan comes on. Also note that you can't remotely close the windows once you have opened them presumably for safety reasons. If this feature also opens the outside air inlet, which I assume it does, this should help keep the car at closer to the outside air temperature rather than allowing the 10 - 30°F rise that a bright sun can induce.

TslaAppScrn.PNG

OTOH my long suffering Mrs had to wait outside for me in the blazing sun for 3 hrs but at least she was comfortable as she had the A/C on the whole time. The 3 hrs used about 6% of the battery so that it is plain that even for a wait of that duration you can use the A/C.
 

JBee

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@Adjelange
I'm surprised they just don't turn on the car ventilation instead of opening a window. They can vary the temperature by varing fan speed then. Wouldn't be hard to add it in software, would definitely save some energy, plus protects the interior a bit from degradation.
 

ajdelange

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You can't draw in relatively cool outside air unless the hot air in the car has a way to get out. Just opening the windows a bit lets the light, hot air escape and cooler air comes in to replace it. No electricity is required. OTOH just blowing the hot air around the cabin without letting cool air in accomplishes nothing.
 

JBee

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Most cars have a rear vent built in. Doesn't take much once the fan is on.
 

ajdelange

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There has to be some kind of air inlet or Tesla's scheme wouldn't work. If the natural draw moves enough air why bother with a fan?
 

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Glass will pass IR, but some is reflected back, yes. But you will get a greenhouse effect by not letting two gasses mix; that has to do with reflective angle (hence high clouds creating more heating than low clouds).

The thicker the glass, the less that's passed through, and different types of glass pass different amounts, of course. Heat-resistant quartz glass is IR transparent, and used in heating applications, for instance.

And most glass - especially glass used in housings - has IR reflective coatings.

You need somewhere over a half inch of glass to actually block IR without special coatings.

-Crissa

(Yes, I know this from testing scrap glass in solar ovens and reading Calfire prevention guides. Apparently most houses lost in wildfires are because the interiors burst into flame through outdated windows.)
 

CyberGus

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I have a sign that I place on my DeLorean's windshield at shows that states " Please look, don't touch". It is more than a reminder to use common courtesy or to avoid fingerprints...
Every DMC owner that puts their car on display includes a "please don't touch" sign, and ends up with 1000 fingerprints anyway. I often find people that sit on my car, or open the door and jump in!

To combat this problem, I know an owner that instead uses a "PLEASE TOUCH!" sign. Passers-by will argue over who must touch it first, and then run away in terror under the assumption that it's a trap.
 

ajdelange

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Well yes but the infa-red can't come through. Glass won't pass it. That's what the picture shows.
Whenever I make a statement like this I always wind up wondering how much of the IR it really blocks. Anyone can go look up on the internet and find out that a 3mm sheet of typical window glass is essentially opaque to wavelengths longer than 3u but what about a piece of actual Tesla glass? Can we do a simple experiment to find out how much IR a piece of it will block? The answer is yes. First off the side windows are 4.7 mm thick.

So what I did is plug in a heater and turn it on full blast. Nuts in todays weather I know but anything in the name of science! It got up to T2 = 135 °C (408 K) and stabilized. This temperature was measured sitting in the car with the thermometer (actually I used the same camera) pointed at the heater and the window down. Next step was to measure the temperature of the heater through the window. It was T1 = 27 °C (300 K) and finally the temperature of the glass adjacent to but not on the image of the heater. That reading was T0 = 25 °C (298 K). The radiant power from the heater which passes through the glass adds to the radiant power from the glass at ambient temperature to produce the T2 reading of 300 K. Thermometers designed for this temperature range look at 8 - 14 microns. At these wavelengths the Planck law shows that the power received by the thermometer is proportional to the 4th power of the temperature. Thus Po + Px = k*To^4 + k*Tx^4 = k*T1^4 = P1. Here k is the proportionality between temperature and power and Tx is the equivalent temperature of the heater as attenuated by the glass. It's clear from this that Tx = (T1^4 - To^4) ^0.25 = 120.9K. The ratio of the 4th power of this to the 4th power of T2 is then the ratio of the incident power to the power that makes it through the glass. That ratio is (120.9/408)^4 = 0.0076. Thus our measurement, crude as it is, confirms that the Tesla window glass is opaque to IR. We knew this already,of course, but it's always nice to have experimental backup.
 
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tmeyer3

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Whenever I make a statement like this I always wind up wondering how much of the IR it really blocks. Anyone can go look up on the internet and find out that a 3mm sheet of typical window glass is essentially opaque to wavelengths longer than 3u but what about a piece of actual Tesla glass? Can we do a simple experiment to find out how much IR a piece of it will block? The answer is yes. First off the side windows are 4.7 mm thick.

So what I did is plug in a heater and turn it on full blast. Nuts in todays weather I know but anything in the name of science! It got up to T2 = 135 °C (408 K) and stabilized. This temperature was measured sitting in the car with the thermometer (actually I used the same camera) pointed at the heater and the window down. Next step was to measure the temperature of the heater through the window. It was T1 = 27 °C (300 K) and finally the temperature of the glass adjacent to but not on the image of the heater. That reading was T0 = 25 °C (298 K). The radiant power from the heater which passes through the glass adds to the radiant power from the glass at ambient temperature to produce the T2 reading of 300 K. Thermometers designed for this temperature range look at 8 - 14 microns. At these wavelengths the Plank law shows that the power received by the thermometer is proportional to the 4th power of the temperature. Thus Po + Px = k*To^4 + k*Tx^4 = k*T1^4 = P1. Here k is the proportionality between temperature and power and Tx is the equivalent temperature of the heater as attenuated by the glass. It's clear from this that Tx = (T1^4 - To^4) ^0.25 = 120.9K. The ratio of the 4th power of this to the 4th power of T2 is then the ratio of the incident power to the power that makes it through the glass. That ratio is (120.9/408)*4 = 0.0076. Thus our measurement, crude as it is, confirms that the Tesla window glass is opaque to IR. We knew this already,of course, but it's always nice to have experimental backup.
hahaha overkilled it. Now do a study on how much energy is absorbed by being opaque and the thermal conductivity of the same material on the same wave lengths!





I'm kidding! :p

Happen to have a UV camera?
 

tmeyer3

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Tesla windshields already have this built-in. I had a Volvo that had the same thing and it makes a big difference. On the Volvo they called it an IR reflecting windscreen and sold it as part of a rather expensive "Summer Package". Tesla doesn't make much of a deal about it but it seems just as effective.
That's really good to know! I assumed my M3 didn't have it since it doesn't have that rainbow effect some of the older M3 and S have. But, of course, that's just an assumption fallacy on my part. This was an interesting read, assuming it's all correct: https://ecowut.com/tesla-windows-uv-protected/

Particularly some the "how to tell if you're UV protected" bits. Clever.
 

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That's really good to know! I assumed my M3 didn't have it since it doesn't have that rainbow effect some of the older M3 and S have. But, of course, that's just an assumption fallacy on my part. This was an interesting read, assuming it's all correct: https://ecowut.com/tesla-windows-uv-protected/

Particularly some the "how to tell if you're UV protected" bits. Clever.
We have two Model 3's, one has the orange-colored roof (when wet) and the other looks normal. But I can't tell a difference in heat rejection qualities between the two styles. When Tesla changed glass suppliers, the new suppliers used a different heat rejection coating but, according to Tesla, it had the same performance characteristics.
 

ajdelange

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No promises that this will tell you anything but as the "heat" entering the car is in the visible and NIR and you don't, onviously, want windows to block too much visible light the goal is to block the NIR. Even a couple of mm or ordinary glass blocks everything above about 4,000 nm. Many remote controls use NIR to control TV's, CD players etc. Take one of these, point it at the camera in your smart phone and press a button. If you can see flickering light from the control's diode then you phone's camera's IR filter is not perfect and it can be used as an NIR detector. Repeat this process with an assistant holding the phone on the opposite side of the glass from the camera. If you can see the diode pulsing through the glass (you can though normal glass) then it is not an effective NIR blocker. If you can't, it is.
 

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Every DMC owner that puts their car on display includes a "please don't touch" sign, and ends up with 1000 fingerprints anyway. I often find people that sit on my car, or open the door and jump in!

To combat this problem, I know an owner that instead uses a "PLEASE TOUCH!" sign. Passers-by will argue over who must touch it first, and then run away in terror under the assumption that it's a trap.
Just modify the sign and say you spray it with toilet water (not the perfume kind) and put a miniature plunger on the windshield at car shows.
Goes back to the old story of the school janitor cleaning the lipstick off the mirrors in the ladies rest room at the school, he just showed the kids how he cleaned the mirrors, he dips the window squeegee in the toilet and removes the lipstick, end of problem.
 
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