Modern air conditioners are horribly inefficient. A possible solution that occured to me was to do the cooling in large plants, that can be very efficient, and ship the cold to people. The obvious way to do this is a compressed gas. LN2 seemed a good choice, because it only results in nitrogen, so it could easily be vented to atmosphere. Further, LN2 can be bought cheaper by the gallon than milk. I figured the distribution system would be that you would have a volume of liquid nitrogen delivered every 3 months or so, and you would store it in a cryogenic container. Then, you would just use it to chill incomming air. I fail to see how it could not be more efficient than the current system, but what concerned me was the question of how much liquid nitrogen would be needed. Would it be like a cubic yard per month, or 200 cubic yards a month? I don't have the thermodynamics skills to calculate that. So, I was wondering if this was a feasible idea.