[ars]

Cooling systems don't have to be complex - lookup peltier cooler.

But they are energy inefficient because the laws of thermodynamics requires it. (You can make them more efficient by not cooling as low - trading temperature for volume. In an A/C that would mean instead of a 40 degree drop, do a 20 degree drop, but with twice the air flow. The net result for the living space is the same, but the efficiency is much improved.)