Nanosolar - low cost solar energy. Or not?

[jimbob]

The angular momentum can be overcome with gimbal mounts or paired flywheels. Energy storage density is better than batteries if you don't need containment. The main problems at this point are getting magnetic bearings to work reliably under the g-forces a car goes through, safety - which means either a lot of extra weight needed for containment or a lot of danger, and probably cost. Safety is a big issue. If the flywheel shreds, you have a huge release of energy in a very short time - basically a bomb.

Yes, and you have to have a large amount of angular inertia, so I can't imagine that cornering would be much fun. (Paired flywheels probably being a better idea than gimball mounts due to the additional mass).

Thinking a bit more about the various different schemes for energising a car. If you want to drive for several hours and only spend a short time refilling (similar to current petrol cars) then I think that chemical energy is the only option. To make the sums easy - suppose you want to be able to drive and only spend four minutes re-energising every two hours. If you transfer electrical power to the car, then you need 30-times the average power use of the car plus a bit for waste (you need just over one joule per joule transferred). If you transfer fuel, with several MJ/kg energy density, then you need far less to transfer from say a pump to the car, maybe several micro-Joules per Joule and well under one mili Joule per Joule.

This means that the power requirements for the "pump" are far more benign.