maybe used compressed air to replace some battery mass, b/c compressed air tank lighter and cheaper (to run at least) than battery, plus the regenerative braking can be partially mechanically done for more efficient regenerative braking and less energy going in and out teh batter for longer battery life. maybe the compressed air can turn a generator which powers motors, or maybe it will be less emissions to run small diesel generator given it can have a much longer lifetime than current batteries. https://www.youtube.com/watch?v=ic6cRlyQ2rk https://www.riversimple.com/test-new/ https://www.riversimple.com/making-efficiency-profitable/ https://www.riversimple.com/technology-behind-rasa-hydrogen-car/
As you know, there are actual cars that run this way, but it is a terrible idea because of poor energy efficiency. When the air is compressed, it gets hot, and unless there is a way to capture that heat, which adds even more cost and complexity, that energy is lost to the environment. It doesn't come close to comparing to batteries in terms of energy efficiency. For long term storage on utility scale projects it may have a place, but not for cars.
Right. Here's a list, in descending order of Energy per Mass, From BatteryUniversity.com:
FuelEnergy by mass (Wh/kg)
Gasoline, diesel 12,000–13,000
Black coal, Methanol 6,000–7,000
Lithium-ion battery 100–250
Lead acid battery 40
Compressed air 34
Supercapacitor 5
There would also be water condensate separation and water freezing in cold climate issues to deal with.
https://www.aptera.us/forum/main/comment/600c972016ff89004ad12839
Compressed air has a very low energy volume density unfortunately. Although there are some useful use-cases to the idea, I think the battery electric works best in the Aptera.