Idea: heat and cool the seats and dashboard directly. I estimate 50 watts thermal per passenger,(max). Average passenger cooling watts probably closer to 35 watts thermal, even on 120F Phoenix days.
Cool the dashboard to a thermostatically regulated temp of 95F.
I would suggest a water chiller such as used for chilling down fish tanks, but obviously adapted for DC input power and compactly packaged.
Cloth steering wheel so I don't have to grab a scorching hot piece of leather in the Phoenix hell heat.
On heating side: 50 watt resistive heaters per seat. Resistive heating element in the steering wheel. Resistive heating element (or electronics waste heat pumped?) for the dashboard & window defogger vents.
I am convinced that Aptera has both the engineering talent and tools (simulation etc.) to analyze some number of alternatives and select the most efficient (Remember that is their underlying goal) for all Aptera system within available near term potential solutions for inclusion in a prototype ready for qualification and testing for production late this year or early next year. I do not believe that we, as lay observers have the tools to sufficiently analyze solutions for the production version. These could ideas can be the basis for determining the next upgraded version once Aptera is successful and has a strong capitalization
Some efficiency sexiness might be gained by using the collected condensation off the cold coil to act as an evaporative coolant before the cold coil.
Peltier is super inefficient. Heat trace is also very inefficient. I really hope they don't use this. A standard compressor AC system is the way to go, relative to the rest of the car it's also not very expensive. Cooling through seats is more efficient. Your body pumps around blood and cooling on your ass and back will cause the rest of you to cool down. Trying to cool down the whole cabin means cooling down a much larger thermal mass, and fighting higher conduction losses to the air outside the car. Just to geek out a bit, a layer of aerogel on the back of the chair is a light weight way to increase the efficiency as its an amazing insulator. Cooling on hands and feet has its own scientific literature and is very effective, the body uses these as radiators. The challenge is not insulting the venous structures with too great a thermal gradient as this causes too much vasoconstriction diminishing the effect.
I agree the steering wheel should be made from/coated in a material that isn't very thermally conductive. Scolding steering wheel is the worst. I also think the cabin should be automatically ventilated above a threshold of cabinet ambient temp when the vehicle isn't occupied. It will prolong the life of electronics, cabin materials, in addition to improving comfort.
Tesla has elaborate heating and cooling plumbing, considering EVs need to operate in all sorts of ambient temperatures, things need cooling, and batteries have an optimal temperature for performance.
Edit: Seat cooling/heating would need to be fan forced. Pure conduction through foam and pleather would take forever. Perforations and a fan are def required.
https://www.aptera.us/forum/main/comment/605d3c251a71170015d1b9a0
My EV's seat heaters only total about 0.11kW. That's the same as headlights only, not even including tail lights.
When it's around freezing out, even cabin heat only takes about 1kW (after using 6kW for about 5 minutes to warm it up). Every little bit helps, but by comparison, there's much greater loss just from the battery's capacity temporarily dropping when cold.
The flip-side is that even though heat decreases longevity, it improves battery efficiency so much that I measure NO range loss when it's hot enough that just blasting the fan isn't enough, & I need A/C (moderate setting of 78F).
I think I heard that they will use peltier technology for heating and cooling the air flow ventilating through the seats. Peltier tech is not very efficient but still better than heating or cooling the entire cabin.
Probably a couple hundred watts per seat should be expected when turned to "high"
Heating and cooling your seat is not enough. Due to radiation heat from the sun hitting your body, you need convection (fan) cooling for your body that sees the sun. I believe the same is valid for heating, convection is needed.