Rooftoop Sprinkler

Virtually all commercial air conditioning systems operate via the principle of evaporative coolingforced airflow through a cooling tower evaporates water, which extracts the heat of vaporization from the chilled water pipes.  Freon-based refrigeration systems also use this process, but with refrigerant as the operating fluid.

Outside areas in arid climates sometimes have a mister that ejects a small burst of atomized water into the environsThe water quickly evaporates, cooling down the whole area.  Outside dining areas for restaurants or the back porch at home, even the deck around a swimming pool can avoid the heat with an inexpensive misting cooling system.

A common commercial application is a rooftop sprinkler for a large warehouse-type building.  A network of misting sprinkler heads spaced out on the roof emits a fine water spray on a signal from a sensor attached to the roof.  The water evaporates from the roof, extracting the heat of vaporization from the roof structure.  The inside temperature no longer reaches 150 F on a late summer afternoon but remains closer to ambient ~ 90 F.

I installed a rooftop sprinkler on my house in Vicksburg, Mississippi a few years ago.  Even though the weather was very humid, the system did in fact lower my cooling bills by close to half.  The greatest benefit was over a vaulted ceiling (no attic space above), preventing all that 150 F heat from radiating directly into the living area.