Air Car better than battery car?
There is another technology you have missed in your assesment of alternative fuels/energy transmission. Compressed air can be used as an energy storage medium in place of batteries. This has many advantages.
Carbon fibre air tanks are much cheaper than batteries.
Air tanks can be re-filled millions of times without loss of performance. This also means the tank exchange stations idea is more feasable than battery exchange. (would you exchange your £30,000 battery rig for an older one with less performance just because it's charged) (infact, we already have an infastructure for safely exchanging empty for full compressed gas tanks [butane/propane])
No rare metals or chemicals needed in production (the dependancy on lithium producing countries is a very big problem in the electric car dream)
Pretty safe. Spillage not toxic, not flamable. Although compressed gas can cause an explosion due to the rate of expansion upon rupturing a tank, we have many decades experiance handling it safely. There are many designs to allow a bottle to rupture safely inside a holder without any casing being ejected (even at 15,000psi)
Green energy production systems like wind and wave power can be setup to compress air directly instead of generating electricity to then run a compressor. This is actually cheaper than building electricity producing wind turbines and rellies less on copper etc.
The engine is farely simple and can be scaled to all aplications we currently use ICE for. You can even have one on each wheel. Re-generative breaking is a doddle. Even car cooling can be run by taking the cooling effect of the expanding air.
There are some issues that need to be worked on, but if a developer threw some money at the idea it's nothing that can't be solved easily. EG
No heating, electrics for lights etc - this could be solved with an air genorator or by using electric brake energy reclaim into batteries instead of air. Or you can even use the cold from the expansion to work a heat engine to make electricity.
The demo cars I have seen on te interweb are not very powerful - add more tanks, higher pressure, more cylinders in engine
Fast charging causes heat - Exchange stations and overnight charge remove this problem, slow charge much more efficient. Or fast charge heat could be used to heat buildings.
Just thought I best keep you informed of all the options!
The PFY