more on Evaporative cooling - refrigerators?
Filed Under: cultural, energy, green Gadget, health on August 3, 2009
Following our earlier post on evaporative air conditioning (Hot? try evaporative cooling), here’s another clever use of evaporative cooling.
For centuries, people living in hot, arid climates have learned the value of cooling by using the sun’s drying abilities.
The science behind it is simple – whenever water evaporates, it draws latent heat away from the contact surface. An analogy that some of us may have experienced is when we have had some gasoline or other volatile fluid in contact with our skin. The liquid feels cool against our skin. What we feel is the evaporative effect of heat being drawn from the surface of our skin when the volatile liquid quickly evaporates.
The following article is from Off-Grid:
Low energy refrigeration
With summers getting steadily hotter, food storage is an issue. Pictured is Mohammed Bah Abba’s Pot-in-pot invention, which won a Rolex Award of $100,000 –a refrigerator than runs without electricity.
Here’s how it works. You take a smaller pot and put it inside a larger pot. Fill the space in between them with wet sand, and cover the top with a wet cloth. When the water evaporates, it pulls the heat out with it, making the inside cold. It’s a natural, cheap, easy-to-make refrigerator.
Evaporative fridges are a relatively well-tested, proven, low-tech approach to cooling. They can cool produce, food and beverages at about 15-20�C below ambient temperatures. They are most appropriate in hot, dry (not humid) climates where there are no other alternatives (and cannot be used for critical purposes such as vaccine storage).
Absorption Refrigerator: These operate on heat cycle, which is normally powered by a kerosene or gas (LPG) burner. A flame or heat element powers the heating cycle, which creates the cooling affect via a heat exchanger.
In gas fridges the flame is powered by LPG.
In kerosene/paraffin fridges the flame is powered by kerosene or paraffin. These fridges emit particulates (and/or gases).
Vaccine Refrigerators: the World Health Organisation (WHO) has approved a number of low voltage DC PV vaccine refrigerators for vaccine storage and medical uses. These can be powered by PV systems.
