Hi Dmitri. Thermal storage is obviously a great way of being able to store large amounts of energy within a small space or mass (I've been thinking about this for some time - it's how some solar-thermal plants continue to make electricity at night). However, the main problem is recovering that energy into a useful form. Even with a Stirling engine, you'd maybe be looking at about 60% maximum efficiency out of it, so 40% of the energy you use to "charge up" the car is lost as heat from the exhaust when trying to convert it back into mechanical (and then perhaps some more if you then convert that to electrical).
On the other hand, you can get 95% back out of a LiIon battery what you put in, so it is a much more efficient solution. The energy density is less, but for the same amount of energy put in you can go almost twice as far.
Another alternative that most people seem to be overlooking is using metal fuel. Essentially you buy a slot in pack (small) containing a reactive native metal, that is allowed to oxidise in the air to make electricity directly. Polyplus appear to have developed a "Lithium Aircell" along these lines, which my back of envelope calculations suggest could propel a car for about 2,000 miles between "refills". Quite why everyone seems to be talking about Hydrogen, when grossly more practical energy storage elements (that are solid, zero emission and easily transported) are available just one or two steps down the periodic table is beyond me.
