The most vital work must be the skin cooling system.

Aptera Community Aptera Discussions The most vital work must be the skin cooling system.

Aptera Community Aptera Discussions The most vital work must be the skin cooling system.

  • The most vital work must be the skin cooling system.

  • David Marlow

    Member
    November 19, 2021 at 12:55 am

    This is one of the most innovative things about the Aptera, it must work with the body and multiple other systems.

  • Riley ________________________________

    Member
    November 19, 2021 at 12:59 am

    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.

    • Curtis Cibinel

      Member
      November 19, 2021 at 1:23 am

      Great reason for lfp. With the general design even if that caps it out as 600 mile the life, thermal stability and happiness being charged to 100% is huge. Pragmatism on max range is fine when it’s ONLY twice what my gas car gets on a tank.

      • kerbe2705

        Member
        November 19, 2021 at 10:30 am

        One issue to consider is that Aptera is designed to use 2170-size cylindrical battery cells and no one seems to be making LFP cells in that size. Most LFP cells are made in the prismatic format: Even Tesla uses prismatic LFP cells in its M3 and MY packs.

        • Curtis Cibinel

          Member
          November 20, 2021 at 11:48 pm

          That is why it’s not trivial to switch to lfp – design transition so take at least a year – likely more. Won’t be overnight but that doesn’t mean it’s not a good idea.

          Cylindrical lfp cells suck. Since you don’t need as much cooling a very different pack design is needed to make the reduced energy density less at the pack level. In most vehicles this is prismatic packs but since the space for Aptera pack isn’t a big rectangle it’s a lot more complicated than the model 3s transition. We have no real public info on the specifics of the pack yet so it’s all speculation on how difficult it will be to engineer using of the shelf lfp options.

          Fyi: 2170 lfp cells are made (generally for other applications) but aren’t a good engineering choice. Tesla uses prismatic cells in the model 3 with lfp and 2170 in others variants for good reason. This change is basically a necessity with lfp. Byd blade (a great lfp option) might not be workable given the shape of the battery space.

          • John Malcom

            Member
            November 23, 2021 at 11:22 am

            Agree with the assessment of the LFP blade form factor for Aptera at present. Confirmed on my visit to BYD. However, with engineering time the blade form factor could be adapted to the size constraints of the Aptera with many aforementioned and future benefits. Remains to be seen if such an engineering tradeoff would be cost effective and accepted by the market place in the U.S. and Canada. Curtis can address the Canadian potential which should be included in any Aptera market assessment as a part of North American Market potential.

            If we have a Mexican engineering type on the forum it would be good to hear from them as well so the whole North American market can be assessed as it is a logical expansion for Aptera.

            I still strongly believe LFPs would be a better choice for shorter range EV to include the Aptera if the analysis identified above provides a positive result.

            Still proprietary, but BYD’s 16,000(!!, yes 16 thousand) R&D staff heavily supported by funding have some exciting things coming. They are striving to be the R&D organization for all China EV providers except of course Tesla. But, Tesla had reps at the R&D presentations too. Hedging their bets I am sure. Hope they stay true to the NDAs they signed.

  • Llewellyn Evans

    Member
    November 19, 2021 at 2:31 am

    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.

    • Paul Schultz

      Member
      November 20, 2021 at 9:53 am

      I am more concerned about how well it will manage battery and cockpit temps when the car is not in motion. Like on a hot day and getting stuck on a hot urban expressway in a traffic jam with the battery temp already at its upper limit of the accepted range. At least with a traditional radiator, you can have a fan kick on to maximize heat transfer. I am sure Aptera is all over this scenario but I haven’t seen a detailed response to this scenario. Is there one out there?

      Paul

    • Llewellyn Evans

      Member
      November 20, 2021 at 4:54 pm

      At rest it is a similar problem for all EVs. At rest they are only rejecting heat generated by AC and auxiliary systems.

      The Aptera may not have the ability to reject as much heat from AC relative to a forced air cooled EV …… but also does not need to reject as much AC heat because it is made from a thick insulating composite material. We are cooling an insulated box, not a metal box.

      • Paul Schultz

        Member
        November 21, 2021 at 6:57 am

        Many, if not all, other EVs have a radiator and fan that can still dissipate heat with enough efficiency while at rest. On a standstill expressway with all that radiate heat coming from the pavement the underside of the Aptera where the skin cooling system is located may have a tough time dissipating battery heat at a standstill. No flow of air unlike when at speed. The batteries may not be at high use during a standstill but were in high use up until the standstill. They will still need temperature regulation once the Aptera comes to a complete stop. Even my Chevy Volt operates its cooling pump and fan immediately after I park on a hot day. And, it turns the system on/off as needed when parked in the sun. What will Aptera do without airflow? Is their system efficient enough to dissipate heat simply by circulating the coolant via a pump when the car is parked or at a standstill? These are questions I know they have had to address but I would like to get detailed answers. There is a difference between aircraft skin cooling systems and the one Aptera is designing. One big difference is the aircraft is moving at a higher speed continuously.

        Paul

  • kerbe2705

    Member
    November 19, 2021 at 10:32 am

    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.

  • David Marlow

    Member
    November 20, 2021 at 1:57 am

    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.

  • David Marlow

    Member
    November 21, 2021 at 4:31 am

    To deal with outside temps over 100 degrees sitting in the hot sun the skin cooling system will need the ability to sweat. Maybe a mist spray that would also help the solar perform better or just a water drip down the sides to the belly pan. The shape of the Aptera should accommodate this very well.

    Are there any other thoughts on this?

    • Elzo Stubbe

      Member
      November 21, 2021 at 4:55 am

      pumped two fase cooling?

    • Alain Chuzel

      Member
      November 24, 2021 at 6:20 am

      Approximate worst case, the solar cells likely on Aptera will lose 15% of rated(*) power. They have one of the lowest, if not THE lowest, “Max Power Temperature Coefficients” of single junction crystalline silicon solar cells. What does this mean? To me it means having any solar cell “active cooling systems” on board the Aptera is likely a waste.

      (*) rated power is at a solar cell temperature of 25 C.

  • David Marlow

    Member
    November 22, 2021 at 11:08 pm

    Besides keeping the solar cells cool and improving there efficiency in the summer and the water then running down the sides to the belly pan and evaporating helping to keep the batteries cool. The system could be used to de ice the solar panels in the winter as you would not want to scrape ice off them as it would damage any nonreflective coating on them.

  • Robert Klasson

    Member
    November 23, 2021 at 12:37 am

    Even though water has a high heat of vaporization (630 Wh/kg), cooling the solar panels would require a lot of water. Assuming a 30% efficiency, in full production, it would require 2.6 kg of water per hour to dissipate the heat generated by the sun hitting the solar panels (not counting black body radiation from the panels, which would help some).

  • David Marlow

    Member
    November 23, 2021 at 10:16 am

    I don’t think it would need to remove all of the heat from the solar panels, just enough to keep the output reasonable and the water running to the belly pan vaporizing enough to keep the batteries from over heating when parked in the sun on a 120 degree day. With out this the batteries would not last long.

  • John Malcom

    Member
    November 23, 2021 at 11:35 am

    All you know the Aptera engineers are aware of all o f the issues and of course with their design. As stated before, Aptera is engineering the car to fully function moving or stationary in ambient temperatures up to 125 degrees Fahrenheit. They will test the vehicle to ensure it functions reliably at the engineered temperature ranges.

    We non engineering types not familiar with thermodynamics, materials science, and without the software tools employed in the engineering process need not worry about vehicle performance at high temperatures because we will have access to all of the testing results.

    That does not mean we can not enjoy our armchair engineering in our postings, but does mean we shouldn’t raise the specter of “The sky is falling” at any point prior to seeing the testing data.

    Of course, a more practical approach would be to pick up your Aptera in SD, immediately drive it over the boarder to Mexico and then out into a Mexican desert. If you are not satisfied, take it back with less than 1000 miles and 30 days and get your money back. Or if you want to stay in the U.S., drive it East into Death Valley where they have had record high temperatures this year.

  • David Marlow

    Member
    December 30, 2021 at 2:47 am

    It looks like the skin cooling system should mark the beginning of the gamma units, as this will have to be refined before delta with the custom Elaphe motors.

    Hopefully the next beta unit will go to Elaphe to let them customize the motors for Aptera.

    • kerbe2705

      Member
      January 2, 2022 at 9:32 pm

      The beta units already have the customized Elaphe motors – what was customized was the way in which the power cables and cooling hoses connect to the motor.

      The reason for sending an Aptera to Slovenia was to “tune” the motor controllers and customize the software, not to customize the motors.

  • Guy SKEER

    Member
    December 30, 2021 at 4:24 am

    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?)

  • Guy SKEER

    Member
    December 30, 2021 at 4:51 am

    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)?

  • Guy SKEER

    Member
    December 30, 2021 at 4:59 am

    (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?

  • John Shenton

    Member
    January 2, 2022 at 8:47 pm

    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.

    • kerbe2705

      Member
      January 2, 2022 at 9:38 pm

      Are EV owners needing to have their battery packs replaced in your area? I know the first gen Leaf battery was problematic, but they haven’t had those problems for the ensuing eleven years. Battery chemistries are much more stable than they used to be.

      The only reason to replace EV batteries seems to be if they are severely damaged or if they have manufacturing defects. Otherwise, EV batteries are lasting for hundreds of thousands of miles with relatively minor capacity degradation.

      • John Shenton

        Member
        January 3, 2022 at 4:24 pm

        Tesla uses the AC to regulate the battery temp. My point is this is critical to long life. At present the average age of cars in the us is twelve years. Mine is seventeen. So a well tested temp management system and ease of replacement/upgrade (batteries will improve) is a must for long tern ownership.

        • Kimberly Wilson

          Member
          March 31, 2022 at 7:19 pm

          I owned a Nissan Leaf with a brand new “Lizard” replacement battery. During one year in Orlando, putting 7K miles on the car, the fully charged battery potential dropped 10%. I traded it for a Bolt EV with enables a fan (and perhaps the AC) when plugged in and ambient rises above approx 90F. But I have faith Aptera engineering is well aware of these sorts of things.

  • John Malcom

    Member
    January 3, 2022 at 5:18 pm

    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.

    • Llewellyn Evans

      Member
      March 31, 2022 at 7:55 pm

      In God we trust. All others must bring data.

  • David Marlow

    Member
    April 1, 2022 at 7:57 am

    It was news to me from the Beta test drive video, that the Alpha’s had skin cooling but not a working solar charging system. Also that all the prototypes so far only had a small battery pack (maybe 5 to 10 Kw?).

  • Jeffrey May

    Member
    April 19, 2022 at 5:49 am

    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.

    • This reply was modified 2 months, 2 weeks ago by  Jeffrey May.
    • This reply was modified 2 months, 2 weeks ago by  Jeffrey May.

    • Oz (It’s Oz, just Oz)

      Member
      April 19, 2022 at 6:42 am

      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?

    • kerbe2705

      Member
      April 19, 2022 at 8:17 am

      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.

    • Jonah Jorgenson

      Member
      April 19, 2022 at 9:30 am

      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.

    • Kimberly Wilson

      Member
      April 19, 2022 at 8:00 pm

      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.

  • A. Grant Nordby

    Member
    April 21, 2022 at 3:54 pm

    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.

    • Gary Greenway

      Member
      April 21, 2022 at 5:20 pm

      That heated roadway will create a rising column of air and cooler air from the side of the road will rush in to fill the low pressure zone above the road. There will be a lot of mixing and the ambient at the height of the belly pan will be much cooler. There will be enough airflow across the radiator panel to carry away heat. The big question is how hot do you need to make the belly pan coolant to extract enough heat from the system.

  • GLENN ZAJIC

    Member
    April 21, 2022 at 8:55 pm

    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.

    • Jon_J

      Member
      April 21, 2022 at 9:15 pm

      I thought I saw someone mention in these forums that if there was simply too much heat to transfer during recharging that the recharge rate would slow down accordingly. This seems like a perfectly reasonable solution for an extreme edge case. Yes, perhaps an inconvenience, but not a safety issue. With such a potential solution, I don’t have any outward concern about the inadequacy of the belly pan cooling system. Don’t want to deal with such an inconvenience? Then just avoid recharging under such circumstances, or dump a Big Gulp of water on the hot pavement under your Aptera before plugging it in to recharge.

      • larry kaiser

        Member
        April 22, 2022 at 7:26 pm

        Maybe that was me. I thought that a simple fix for battery heat problems when charging would be to make the rate of charge dependent on the vehicle’s ability to get rid of the heat generated. Level 2 charging was going to be limited to 3.3 KW or half what was available. In a large part of the country there are many days where the ambient temp combined with the wind means that the Aptera could charge at a much higher rate than the fastest Level 2 charger. The last I heard they were testing both 3.3 and 6.6 chargers. I certainly hope they decide to use the faster charger even if it costs a little more.

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