[DeepDuh]

What I gather from the article it's not the stored energy that's of some concern, but the 250 bar nominal pressure in the tanks - a rupture might lead to metal splinters flying around. However, they claim that the car's underfloor is enough shielding. I'd say let some independent safety tests figure that one out.

So far I think this is a very promising concept - I was always weary about electrical hybrids because of the use of rare earth metals and the environmental impact in some regions because of that. Putting some nitrogen tanks and mechanical/electronic bits in a car to achieve the same effect for city driving seems like a big winner - mass produced I'd think you could make those cars only minimally more expensive than normal gas powered ones. Electrical Hybrid car prices, meanwhile, don't seem to scale down much.

[gus_massa]

Here in Argentina ~1/5 of the cars use compressed natural gas (mostly methane) tanks at 200 bars, because it is cheaper than gasoline. I don't remember any horror story of a crash, and these cars are generally considered almost as safe as the usual cars. The main drawback is that the tank is very big and uses half of the back trunks.

More information: http://en.wikipedia.org/wiki/Compressed_natural_gas

[StavrosK]

We do the same in Greece, the tank is 50-60 liters (not sure if that volume is when the gas is at STP or compressed), though, and takes around the room of the spare. That's also where they put it.