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Skin cooling system info
If I wanted to customize the look of my Aptera with a vinyl wrap, of course avoiding the solar panels ????, would that impact the vehicles skin cooling system?
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66 Replies
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Skin cooling system info
Joseph Cook updated 2 months ago 36 Members · 66 Replies
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Founder Steve explained in a recent video that the belly of the Aptera serves as the radiator – cooling channels do not run throughout the body. If you look closely at the belly rendering you’ll see that there’s a panel distinct from the rest of the body – note the connector-holes.
I believe it was CTO Nathan who said that the belly material has not yet been selected – that it might be aluminum.
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Doing a little digging, I found some data that suggests that laminar flow, which is amazing for aerodynamics, is not great for heat dissipation. When laminar flow is achieved, a boundary layer is created and that boundary layer is insulative.
This means that using the exterior panels as radiators might not be the most efficient means of dissipating or gaining heat. This is a huge deal for southern climates with high humidity.
Can we get a little more information related to the climate system?
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I think the Aptera engineers are pretty astute at doing research and experimentation to determine the best solution for engineering the Aptera for a range of environmental conditions. They have a mix of engineering skills including automotive and aerospace and collaborate in a multidisciplinary fashion. Of course, the proof of any engineering solution is in operational testing. I believe they will do thorough testing and remediation if necessary so that my Aptera will function well in the Florida heat an humidity.
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Your concern about the heat transfer skin effect is valid. I asked them 7 months ago during one open meeting and they responded they have addressed this in their design. I would hope so living in AZ where the temps hit 120F. But at least it is a dry heat.????
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What happens to the Aptera in the cold and rain or when driving through puddles etc? Because the underbody is effectively heated, are we going to see Apteras covered in rising clouds of water vapour as the in-body cooling pipes evaporate it. Obviously, when driving along this would stream out behind. Has anyone considered this, because it might not look too good, especially at traffic lights or other stationary moments?
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The cooling system for aptera will never get more than several degrees above ambient so you will not have a situation like that happen. It’s a common misconception that electric cars cooling systems are as extreme as internal combustion cars but the delicate electronics and batteries would fail if Temps were to exceed 120°f.
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Ambient in the AZ and Mexico may well be around 125F. We have enthusiasts in those areas that are worried about battery cooling as well as others in warm humid climates. Aptera engineering is aware of this concern and will engineer and test accordingly.
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Let me be clear, this is not a response from Aptera engineering but from someone with related experience
I don’t know about the tech for the Aptera approach to the battery cooling issue. They have an innovative, and I am sure proprietary cooling system. I know we will have more information about the specifics as development and testing moves along.
I have this experience working in EV development. It is generalized so as not to reveal manufacturer proprietary information. I am sure it may differ from other sources of this information, but will be in the range +/- some.
EV battery cooling systems are used for three primary things. Of course to make sure the batteries operate in the best range for performance and longevity, and to make sure temperature is evenly distributed across cells.
Temp range for the batteries should be kept between 60 – 95F and the temperature differential between cells between 37 – 39F.
Of course, the type of cell chemistry and geometry of the cells is a factor in battery temperature maintenance as well as the battery control electronics. I trust Aptera to do excellent engineering on batteries and the cooling systems as they have safety as a first principle and will do exhaustive testing to insure optimum operation and safety.
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Phew, long thread. This is my most pressing question about the Aptera as it not only affects battery life and performance but personal comfort as well. It would suffice for me if Aptera would publish some test results.
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Sirs and Madams, I think they should wait until production starts before they openly show tech and solutions.
Remember how a crooked FORD engineer stole delayed wipers from an inventor.
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Anyone have any ideas as to what the target battery temperatures should be maintained at, and how this is achieved when the car is parked on a hot day? In the sun the interior can get over 110F, and who knows how hot the battery compartment will get. In the first Aptera design iteration I read the car will use the batteries to run an interior fan. The fans won’t heat up the batteries but how about the ambient temps? I always try to park in the shade, but the Aptera likes the sunny spots. If driving down a hot highway does not heat up the batteries, what other operating conditions are a concern and how have Aptera designers tested the current design? What are the active battery management operations that make the Aptera less likely to suffer the fate of the Nissan Leaf?
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The composites used involve layers and foam. That is undisputed. This suggests the skin serves as a fairly good insulator. If you’ve got a cooling regime – I’m kind of reminded of the kind you plug into a 12-volt through the cigarette lighter except sized for the interior of the Aptera.
Oh, and when parked in the sun, the underside of the Aptera is still ‘in the shade.’
It is going to have active cooling on hot days not only of the battery and electronics which share the ‘interior’ of the shell composite. I’m guessing this entire interior is actively cooled.
We know that power will be available because every Aptera has solar panels. The cooling subsystem therefore is almost certainly powered by the sun when parked in the sun. That cooling would commence immediately and the draw on the solar going to replenish the battery also a covered priority.
Admitted, this would be a greater challenge on a traditional steel-bodied EV. While it is definitely cool it can do this; more importantly it is perfectly reasonable, given power input uniquely available on Aptera, that it can do this. If the battery is ‘full’ you have to do something with the solar power; you know, like keep the car cool.
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This is one of the most innovative things about the Aptera, it must work with the body and multiple other systems.
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This is one of my bigger concerns as i live in a California and have seen some 120 degree days. Having an insufficient cooling system could severely hamper charging and cell life.
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If the car uses 100Wh/mile and you are traveling at 60miles per hour, then I think you are using 6kW hours in that hour. If the round trip efficiency of the battery is 80%, then you would be wasting 10% during discharge or around 600W as you travel down the road at 60 miles per hour. If that 600W was dissipated over a couple of square meters of aluminium heat sink with 60M/H wind rushing over it, then It would be basically ambient temperature. I don’t see the problem …… except as Riley notes …. when the ambient temperature is extremely high, but then it is in the same situation as any other EV.
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Keep in mind that only the belly of the beast will play a part in the “skin cooling” system, which will most likely be an aluminum “chiller plate”: This is in keeping with Llewellyn’s “…couple of square meters…” comment.
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They have stated that it will be one radiating loop, unlike my Volt that is more complicated with three. I can think of some different ways the systems could share that one loop that would also let the Aptera recycle the heat generated by some parts to use it in other areas where it may be needed. This would reduce the need for electrical heating.
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For the Hot test, all they need to do is drive the Mule(s)/Testbeds North on I-15, and through the Mojave in July/August.
I had been thinking that I would Rig Up a “Desert Racer” Cooling Adjunct: Windshield Fluid Pump/Reservoir with Alcohol/Water, to spray Belly skin. (Wonder if the Wrap can Tolerate?)
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In Crane service, there is an operating Mode that poses one of the hardest to handle: “Plugging”. That is when the Operator is using Motive Power to keep the drive actively suspending the Load, without moving very much – Brakes are Open. Time at Zero Speed, and Load militate to drive Winding Temps through the roof!
A similar problem presents in Vehicle use: Using the Drive(s) to hold Position on an incline. I believe that this will have to be Cautioned against in Operating Manual, and may also mandate Temperature Limiting Strategies to protect the machine.
Question: Do We know that there is some regime of Ladder Logic in place for the Drive System(s)?
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(Sorry Folks, just FreeThinking on an EARRRLY Morning)
It is kinda neat, thinking about a Gently Warm APTERA underbelly beneath Me as I drive somewhere Way Up Here in the Glorious NorthBest of a Winter Morning.
But, Struggling across the Mojave in Late Summer, with ambient Temps North of 110 F, How Hot will the Keel Cooler be, and what effect on the Composite Fuselage and the Adhesives holding it together? How “Cool” the Cockpit? Is the system Contemplated to be a Pressurized System – Pressure Cap/Reservoir?
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In Phoenix this last summer was the hottest on record, setting marks for the most 95-degree days (172), 100-degree days (145), 105-degree days (102), 110-degree days (<b style=”font-family: inherit; font-size: inherit; letter-spacing: 0px;”>53) and 115-degree days (14) in a year. I’m concerned about battery life and ease of replacement.
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Of course we should be concerned about cooling (And heating) of the batteries, especially those of us that live in very hot or very cold areas. Aptera engineers are aware of the need to design and test against climatic extremes and are doing so.
To get precise answers to heat exchange issues (Hot or cold) we will need to wait until testing is complete and there is actual data available to review. Speculation at this point is fruitless as we do not know what the engineers have designed nor do we know the testing plans for this engineering area.
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Did anyone see the recent video from Aptera Owners Club interviewing Aptera’s thermal systems lead engineer about the thermal management system?
https://m.youtube.com/watch?v=E8rfvRnwFJw
To say I was disappointed with the lack of detail would be a huge understatement. They basically just looked at / talked about a test stand for 6 minutes.
Also, regarding some of the above discussions in this thread… to suggest that there’s no need to worry about cooling issues simply because Aptera is aware of the challenges involved is naive IMO. Certainly Aptera engineers were *also* aware of the basic physics and cooling demands back in 2010 when Aptera failed out of the X-Prize competition due to overheating during the race. And, as has been pointed out multiple times in this thread already, cooling the vehicle while driving at speed is likely a *less* difficult cooling scenario vs a stationary vehicle fast charging on a hot day since you wouldn’t have continuous airflow over the belly.
Given that near-perfect aerodynamics are a foundational requirement for this vehicle and the fact that this has led Aptera to rule out conventional cooling approaches and venture down an unproven path with a limited heat rejection capacity, it’s not at all inconceivable that Aptera could design themselves into a proverbial corner that they can’t get out of, and end up with a highly compromised solutions that fails to perform adequately in real-world conditions.
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Jeffrey, you do realize of course, that not only is the vehicle propulsion completely different then the x-prize vehicle, but that the management team and engineers are not the same ones in place as at that time?
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Note, too, that the Xprize Aptera had a single, large, inboard electric motor that generated a great deal more heat than the current outboard in-wheel motors. That vehicle was also powered by early LFE batteries which – under duress (such as during a race) – can produce much more heat than current battery chemistries.
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Jeffrey, I see nothing in your post that would indicate you are an engineer with a heat transfer background. A post of this nature would make more of an impression if you could relate some engineering information to substantiate your observations. I am an Artemis Project engineer. I have no issue with the discussion. Pretty routine to have a test bench for testing this kind of a design. Saves costs, can vary conditions needed for a Design of Experiments (DOE) thorough set of test cases. I am surprised Aptera has one of these. Would not expect that level of sophistication in a vehicle start up to validate design, identify issues through exhaustive testing, and validate remediation in a quick turnaround.
You should be grateful that Aptera is using one of these. It is reducing the risk of on time delivery and insuring a well functioning vehicle when delivered.
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After seeing the test bed video, learning that Aptera will have a circulating glycol solution transferring heat from the battery pack to the aluminum belly pan for radiation to the environment gives me a great deal of confidence. Given appropriate battery chemistry the system will far exceed the thermal performance of a Nissan Leaf with fan-less air cooling and no cooling fluid whatsoever.
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It will be important to remember that the paving surface just below a standing Aptera could be 170 degrees F or more (especially if asphalt), not just the temperature of the ambient air some distance above. That surface will radiate toward the belly pan, and heated air will slowly plume past the belly.
This is the worst-case environment condition for which they must design.
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While I am not an engineer, I believe that the only serious heat concerns will be related to recharging and not driving the vehicle. When recharging there is much less heat transfer from the body, and the amount of power being absorbed is greater than that required when driving. I was glad to see this test bed as these conditions can be easily simulated and addressed early, as they should be. They might need to add reservoir capacity for extra coolant volume or some other circulation solution. I have every confidence that they will figure it out.
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So the Noir Black looks great, but will the dark color be a problem on hot sunny days? The only depiction of where the skin cooling is located that I could find looked like it was along the lower sides of the Aptera. Does anyone know if this will be a problem on hot sunny days when the surface of a black vehicle will get hot. It would be unfortunate if there wasn’t enough cooling capacity to keep the battery cool and provide enough cooling to the passenger compartment.
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This reply was modified 8 months, 3 weeks ago by
Wyatt Andrews.
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This reply was modified 5 months, 1 week ago by
Gabriel Kemeny.
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This reply was modified 8 months, 3 weeks ago by
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The cabin tops of all models will be the same color… solar panel color. Don’t worry about the cabin heating or cooling. They have a whole team of engineers and suppliers working on it.