Monday, July 9, 2007

Evaporative Coolers, and making your own cool air

Last year there was a popular posting about making your own air conditioner. The idea was to run pipes through a bowl of cold water (perhaps with ice), and weave the pipes inside a normal house fan. Turn on the fan and it blows across the pipes exchanging heat and cold, cooling the air, and voila your house is cool. I started to try the idea myself, wasn't able to get it to work, and I even tried a different version with hanging a cloth in a bowl of water.

A similar idea is the swamp cooler, or evaporative cooler. This is something which does work, in certain climates, and is quite popular in desert areas. It's the same idea, evaporation of water cools air and you can harness that to cool a house.

I live in Silicon Valley, and have bought a low end evaporative cooler, and found that it works fairly well.

I want to go over the principles and resources available on the Internet.

Evaporative cooler (Wikipedia): Gives a good overview of the several types of evaporative coolers. They clearly say the system works best in dry climates, and only so-so in moderately dry climates.

Evaporative Coolers: Whole-house cooling in arid regions at a low first cost Has another in-depth survey of this cooling technique. An advantage they mention is the ability to cool without using refrigerants such as chlorofluorcarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), that can harm the ozone layer. They have another page on two stage evaporative coolers. In the first stage of a two-stage cooler, warm air is pre-cooled indirectly without adding humidity ... In the direct stage, the precooled air passes through a water-soaked pad and picks up humidity as it cools. Because the air supply to the second stage evaporator is pre-cooled, less humidity is added to the air

The Energy Efficiency and Renewable Energy Consumers Guide has another good overview of evaporative cooling. As does the Phoenix city government.

Home Energy Magazine has a more technical article, that includes a U.S. map showing the likely areas where evaporative cooling would be best. And there's another at


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