Passive: good design of buildings can significantly reduce the amount of artificial (active) AC required even in very warm climates by properly positioned windows to bring in solar radiant heat, the use of the stack effect to create ventilation, and systems to create evaporative cooling effects.

Absorption Chilling: Instead of relying on electricity to compress the refrigerant back from gaseous to liquid state, absorption chillers heat the refrigerant liquid. The heat input can very easily come from direct solar radiant energy. This type of chiller is old technology, invented in 1858 by Ferdinand Carré. An efficient working model of this type of chiller was designed by Albert Einstein and  Leó Szilárd in 1926. It is also attractive in terms of maintenance since it requires no moving parts unlike a mechanical compressor which can break down over time. Companies like Solem Consulting™ and Sopogy MicroCSP™ are employing these systems today and they could be cost competitive to compressor refrigerant type of chillers in the coming years.