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Once a forested area, soil erosion is now a major problem in this Ethiopian region; and the wells are a long way from the villages.

In previous summers, milk products were stored in snow-filled "nevère" in Ticino, Switzerland.

Earth, water, air, and shade

Open the door and take a cool drink out of the refrigerator. An entirely automatic action for the one, and entirely unknown for the other. The cooling of food and drink without electricity is an old science and still a common one for billions of people today.

A winter day in middle Europe. It is snowing; other than very few exceptions, the thermometer has read between 2 and 8 degrees Celsius for weeks. The perfect temperature to keep food cool. One could make use of nature and simply turn off the refrigerator for a few weeks. Save on electricity and, on top of that, lower carbon dioxide emissions by storing milk and butter, meat and vegetables on the balcony. Or even better, in a dark, well-ventilated pantry, which was found in every home before the invention of the refrigerator.
Although every second house in the U. S. had a refrigerator in the 1930s, in most European countries, twenty years later only ten percent of the households had one. Today, there are circa 500 million and circa 60 million new ones are manufactured every year. The refrigerator has simplified our lives and decisively changed our eating habits. But the science of natural cooling has been virtually lost. The numerous inquiries on advice pages on the Internet provide evidence of that. How can I keep beer cool at a picnic? How can I store meat when camping? Questions that, at most, a boy scout would be able to answer these days: And undoubtedly, the nearly two billion people in the world who have to get by without electricity. They are not really concerned with a cool beer after work, but rather, the proper storage of foodstuffs. They pass on their knowledge from generation to generation, but they, too, are dependent on the building blocks necessary for natural cooling: earth, water, air, and shade.

Ice houses and air fountains
Since time eternal, these elements have been used for cooling foodstuffs and medications. Already in classical antiquity, in the Mediterranean area, ice was stored in so-called ice houses year round. As a rule, these were underground chambers built close to fresh water lakes. In the winter, the ice was brought into well-isolated cellars and it remained frozen there for several months. For another cooling principle that is used throughout the world, a hole is dug in the ground and covered with wet towels or straw. Clay pots are also suitable for natural cooling when one stores them in an airy, shaded place, and covers them with wet towels.
More elaborate, but also used for centuries is geothermal power for warming and cooling, via so-called air fountains, a special type of geothermal energy exchanger. In the cold seasons the outside air is not led directly into the building, but pre-warmed in the soil. In the summer, the system works the other way around: the air, cooled in the soil, provides comfortable, cool temperatures inside.

One of the most important building blocks for natural cooling is unfortunately not available everywhere today: the forest. Due to deforestation in many areas of the world, soil erosion is a major problem. The annual loss of forested area comprises, according to the FAO, in a country such as Ethiopia alone, more than 200,000 hectares. Villages without shade in southern Europe and Africa, ground water that sinks ever deeper. Where there are no trees, there is also less wind, not to mention a lack of natural shade. Whereby trees are perfect cooling systems, par excellence. They gather rainwater in their roots, which prevents the earth from drying out and eroding. Their canopy of leaves offer shade, and the wind, which wanders through their leaves, creates clouds that bring vitally important rain.
A tree cannot, however, arrange much alone. The countless reforestation programs in these countries are, indeed, important, but in terms of amount, only a drop in the ocean. Whereby, one single hectare of forest is enough to bind 60 to 1000 tons of soil (depending on the region and type of tree). And that would recover, for the most part, the basic elements for natural cooling—earth, water, air, and shade.

Source: sun-connect 5 | April 2011 (p. 4)