A compound swamp cooler air conditioner could be built which would supply a cool dry air supply from a hot dry sunlit location. This could work well in a desert location where there is an abundance of sunshine and some water.
Many people who live in hot desert areas such as the American Southwest use evaporative coolers, commonly known as swamp coolers, to lower the temperature of their living space. In a very dry area with an air moisture level of 20% or less these coolers also help provide comfort by raising the moisture level to a more comfortable level between 50% and 90%. Below is a chart from Wonderquest.
What I am going to do is show you how you can make a compound evaporative cooler which will take the cooled air from the first stage of the results represented in the chart above and use that cooled air in a second stage to make the output air even cooler and dryer.
Air that is about 50% humidity and 75° F is considered quite comfortable by most people. The air coming out of an evaporative cooler is closer to 100% humidity so a person directly in the out flowing air on a 102° F day would feel a very pleasant near 100% humidity 75° F breeze. It isn’t quite that simple however because the building itself is subjected to hot sunshine on the sunlit side and reaches temperatures of 180° F and on the shady side will be subjected to hot 105° F air plus reflected hot-light from the surrounding hot terrain. So the interior of the building will rise to somewhere between 105 and 180. Hopefully there is insulation all around the walls and ceiling of the building and it won’t get nearly that hot but it will become uncomfortable. Below is a swamp cooler diagram from Opalcat
What is proposed is a slightly more complex swamp cooler made by compounding the cooling cycle. This is done by using the cooled air from the evaporatively cooled air to pre-cool the air and water coming into a second stage. There could be even more stages for even greater cooling of the final air produced. The whole system could still be operated on a single motor by running its rotating shaft thru the walls to each of the propellers, some of which have a reversed pitch. Also it would be operated on a single input source of water to wet the blankets, with a single water level control valve, by having an overflow from this first and most consumptive pan of water to the other cooler pans of water. The water to be pumped to each of the cooling pads could be drawn from the coolest pan of water, the one from the last stage of the cooling process. The water would be inserted into the system at the warm end but by being drawn for all of the pads from the cold end there would be some improvement in efficiency.
The blue walls between each section are made of a heat conductive material such as a thin sheet of copper or aluminum. The diagram looks a bit complicated but if you follow the path of the air you can see how it gets progressively cooled as it flows along the channels. The advantage of this cooling system is that it would consume a very small amount of electricity to operate compared to the traditional heat pump style air conditioner.
[Update 2010-11-19 I just discovered a commercial site in Colorado called Coolerado which is already manufacturing a similar cooling system. It appears to be only a single stage cooling system. What I attempted to diagram, in the post above, is a two stage cooling system which uses singly cooled air to cool a volume of air which is then run across a wet blanket to cool it even further. This colder air is heat-exchanged to dry air thus ending up with cool dry air flowing out the system.]