No camshaft engine as air pump for compressed air hybrid.

http://m.youtube.com/#/watch?feature=g-high-u&v=Bch5B23_pu0

What are the drawbacks compared to a battery hybrid? I'm struggling to think of any.

First one that comes to mind is the consequences if an air tank pressurized enough to hold significant amounts of energy gets damaged in a crash.

Compressed air can be as dangerous as compressed gas. Except, no fire.

Also there's the heating/cooling effects of compression and decompression and the fact that you can't store much (even compared to today's low-end EVs).

Edit: After watching the video it could be a worthwhile as a stop-start technology but it would be hard for it to compete with an electric hybrid. I found the actual pneumatic valve tech far more interesting. If would allow for fully variable duration (lift seems to be fixed), possibly allowing for a valve-throttled engine, and would give any engine cylinder deactivation capability. Plus it frees up almost all the energy needed to drive a traditional valvetrain.

iceracer wrote: Compressed air can be as dangerous as compressed gas. Except, no fire.

Isn't fire the primary danger in an accident with compressed gas? There are a lot of cars running on LPG and they don't seem to explosively decompress very often.