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.

     Alain Chuzel updated 2 weeks ago 11 Members · 19 Posts
  • 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.

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