Speakman is better known for its luxury shower heads, but it was fitting that in the hot, dry atmosphere of Phoenix, that they demonstrate the latest in evaporative coolers. For those who haven't been following our search for the solar powered air conditioner, when water changes state from liquid to gas it absorbs a great deal of heat. People have been using this fact to build desert coolers for over a hundred years. But the traditional ones added a lot of moisture to the air, which makes it feel warmer because you don't sweat as efficiently.
To beat this problem, indirect cooling was developed, where the cooled, moist air used to cool dry air indirectly. We have shown Coolerado coolers that did this with an air-to-air heat exchanger.
Speakman cranks up the efficiency by using water as a transfer medium. The moist but cool air cools water, which is then pumped through a very standard looking heat exhanger like the one on any air conditioner, shown above. The unit is able to deliver 3.5 tons of cooling with only 456 watts of electricity, easily within reach of a solar panel.
The problem is the water; the unit sucks up almost 2.5 gallons per ton of cooling per hour, which could add up quickly in a place like Phoenix. It is just vapourized and lost into the atmosphere. Perhaps if it could run on collected gray water this might be a better solution, but there really is a tradeoff between electricity and water, and right now both are a problem.
UPDATE: Making electricity uses a lot of water too. See Evaporative Coolers Don't Guzzle Water After All
Russ Waters of Speakman explains how it works. More at Speakman
More on evaporative coolers:
Coolerado Coolers: Getting Close to Solar Powered Air Conditioning
The Rebirth of the Cool: 7 Innovations in Air Conditioning