Photo credit: ITDG/Mohammed Mazjoub
| Evaporative Cooling Systems |
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Photo credit: ITDG/Mohammed Mazjoub |
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Evaporative Cooling Systems Food preservation in the developing world can be difficult due to limited resources. Electrical or gas refrigeration is generally unfeasible, and solar refrigeration systems are too expensive. Evaporative cooling systems can be an economically, socially, and environmentally suitable solution for the problem of food preservation. The evaporative cooling systems featured on this site use water and locally available materials for their operation and construction. They require no energy inputs; however they do require certain environmental conditions. These evaporative cooling systems use evaporation of water from the surface of the device as the mechanism of cooling. As water evaporates a lot of energy is used in order for water to reach 100 degrees Celsius and then vaporize. One calorie per gram is needed to heat water one degree and 539 calories are needed for the water to change from a liquid to gas state (hyperphysics.phy-astr.gsu.edu). For evaporative cooling systems the required energy to evaporate water comes from heat loss from the surrounding environment. Some of this heat loss occurs inside the device itself. Conditions under which evaporative cooling works: Evaporative cooling is a natural phenomenon which occurs more rapidly in hot dry climates. Pot in Pot devices are used in arid regions of Africa such as the Sahel. The Coolgardie Safe was developed in the hot climate of Western Australia. More complex and energy intensive devices such as swamp coolers are currently being used in semi arid regions of the United States. Swamp coolers also use the evaporation of water as a mechanism of cooling. Below is a useful chart that shows the environmental conditions under which swamp coolers function best posted on the California Energy Commission's Evaporative Cooling web site. This chart can also help one decide which environments will be suitable for evaporative cooling devices of any sort.
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