Think it'll ever be released?

http://finance.yahoo.com/family-home/article/106040/Air-Cars:-A-New-Wind-for-America's-Roads

Shocking that it even made the news...

 

What kind of energy does it take to compress massive amounts of air, though?

 

Good question...

 

Very little energy is required to compress air, because it can be done using mechanical advantage.
Compressing air is also cumulative. Because the valve does not let molecules back out, you waste no energy keeping them in.

 

The only air compressors I've ever seen have been electric, so will the battery power it?

 

You would still use an electric air compressor, and how you generate that electricity would determine a lot as far as environmental impact. In any case, the energy requirement is much less than internal combustion.

There are some models that also have an onboard compressor that uses a fuel of your choosing when you run out of air. It doesn't power the engine directly, but instead recharges the compressed air, which takes very little energy.

I'm not sure of all the caveats, but like all technologies there are bound to be some. Advocates will focus on the advantages, while critics will focus on the problems.

Promising though!