[permaculture] Yakhchal - Wikipedia 400 BCE Persian engineers mastered technique of storing ice in middle summer in desert.

Lawrence London lfljvenaura at gmail.com
Sat Mar 10 04:02:00 EST 2012


Yakhchal
http://en.wikipedia.org/wiki/Yakhchal

*Yakhchāl* (Persian <http://en.wikipedia.org/wiki/Persian_language>: یخچال‎
*ice pit*; *yakh* meaning *ice* and *chāl* meaning *pit*) is an ancient
type of evaporative cooler <http://en.wikipedia.org/wiki/Evaporative_cooler>.
The word also means *glacier* in Persian.

By 400 BCE, Persian <http://en.wikipedia.org/wiki/Persian_people> engineers
had already mastered the technique of storing ice in the middle of summer
in the desert.[1] <http://en.wikipedia.org/wiki/Yakhchal#cite_note-Rael-0>

Above ground, the structure had a domed shape, but had a subterranean
storage space; it was often used to store ice, but sometimes was used to
store food as well. The subterranean space coupled with the thick
heat-resistant construction material insulated the storage space year
round. These structures were mainly built and used in
Persia<http://en.wikipedia.org/wiki/Persia>.
Many remain standing that were built hundreds of years ago.
History

By 400 BCE, Persian engineers had mastered the technique of storing ice in
the middle of summer in the desert. The ice could be brought in during the
winters from nearby mountains, but more commonly they had a wall made along
an east-west direction close to the yakhchal. In winter, the
qanat<http://en.wikipedia.org/wiki/Qanat>water was channelled to the
north side of the wall. The shadow of the wall
made the water freeze more quickly so more ice was produced per winter day.
Ice was stored in a specially designed, passively cooled refrigerator. This
was a large underground space (up to 5,000 m3 (180,000 cu ft)) that had
thick walls (at least two meters at the base) made out of a special mortar
called sārooj, composed of sand, clay, egg whites, lime, goat hair, and ash
in specific proportions, and which was resistant to heat transfer. This
mixture was thought to be completely water impenetrable. The space often
had access to a Qanat, and often contained a system of
windcatchers<http://en.wikipedia.org/wiki/Windcatcher>or wind towers
that could easily bring temperatures inside the space down
to frigid levels in summer days. The ice was then used to chill treats for
royalty during hot summer days and to make
faloodeh<http://en.wikipedia.org/wiki/Faloodeh>,
the traditional Persian frozen dessert.
Features

The yakhchal in Kerman <http://en.wikipedia.org/wiki/Kerman> is located
about a mile from the center of the city. This cone-shaped building is
about sixty feet high. The massive insulation and the continuous cooling
waters that spiral down its side keep the ice stored there in winter frozen
throughout the summer. These ice houses used in desert towns from antiquity
have a trench at the bottom to catch what water does melt from the ice and
allow it to refreeze during the cold desert nights. The ice is broken up
and moved to caverns deep in the
ground.[*why?<http://en.wikipedia.org/wiki/Wikipedia:Please_clarify>
*] As more water runs into the trench, the process is repeated. Often seen
around the ice houses and many of the homes in the desert are towers called
badgirs <http://en.wikipedia.org/wiki/Badgir> or wind traps. Built of mud
or mud brick, these badgirs, mentioned by Marco
Polo<http://en.wikipedia.org/wiki/Marco_Polo>,
are square or round, but the operating principle is the same: to catch the
slightest breeze in the vents at the top and to funnel the cooling air down
through internal, vertically-placed wooded slats to the water or dwelling
below. Alternately, the badgir can function as a chimney, expelling warm
air to pull cool air out of a qanat (an underground stream).

In present-day Iran, the term yakhchal is also used to refer to modern
household (and commercial) refrigerators.


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