Windcatcher

[1] Windcatchers come in various designs, depending on whether local prevailing winds are unidirectional, bidirectional, or multidirectional, on how they change with altitude, on the daily temperature cycle, on humidity, and on how much dust needs to be removed.

[3][2][12] The "place of invention" of windcatchers is thus intensely disputed; Egypt, Iran, and the United Arab Emirates all claim it.

[12][13] Windcatchers vary dramatically in shape, including height, cross-sectional area, and internal sub-divisions and filters.

Windcatchers have also been used experimentally to cool outdoor areas in cities, with mixed results;[2] traditional methods include narrow, walled spaces, parks and winding streets, which act as cold-air reservoirs, and takhtabush-like arrangements (see sections on night flushing and convection, below).[14]: Ch.

[2] In areas with more variable wind directions, there may also be radial internal walls, which divide the windtower into vertical sections.

[16] If the wind is dusty or polluted, or there are insect-borne illnesses such as malaria and dengue fever, then air filtering may be necessary.

[2] Some dust can be dumped at the bottom of the windcatcher as the air slows (see diagram below), and more can be filtered out by suitable plantings or insect mesh.

[15] The short, wide right-triangle-prism malqaf are usually bidirectional, set in symmetrical pairs, and are often used with a salsabil (evaporative cooling unit)[2] and a shuksheika (roof lantern vent).

[16] Wide malqafs are more often used in damper climates, where high-volume air flow is more important compared to evaporative cooling.

Even the thermal inertia of thick masonry walls will keep a building warmer at night and cooler during the day.

Windcatchers can thus cool by drawing air over night- or winter-cooled materials, which act as heat reservoirs.

If a windcatcher's open side faces the prevailing wind, it can "catch" it, and bring it down into the heart of the building.

The air flows through the house, and leaves from the other side, creating a through-draft; the rate of airflow itself can provide a cooling effect.

[2] The shape of the traditional shuksheika roof also creates suction as wind blows over it.[14]: Ch.

[16] Windcatchers can thus cool by drawing air over night- or winter-cooled materials, which act as heat reservoirs.

They may use windcatchers to circulate air into an underground or semi-underground chamber, evaporatively cooling the ice so that it melts only slowly and stays fairly dry (see lede image).

[16] Windcatchers are used for evaporative cooling in combination with a qanat, or underground canal (which also makes use of the subterranean heat reservoir described above).

The hot air brought down into the qanat tunnel is cooled by coming into contact with the water flow and the surrounding earth.

[citation needed] A salasabil is a type of fountain with a thin sheet of flowing water, shaped to maximize surface area and thus evaporative cooling.[16][14]: Ch.

It may also be generated using spray nozzles (which have a tendency to get blocked if the water is hard) or cold-water cooling coils (like hydronic underfloor heating in reverse).

[28][29][30] They are generally shaped as right triangular prisms with the vertical side left open and facing directly up or down wind (one of each per building).

Their use is now being re-examined, as air conditioning accounts for 60% of Egypt's peak electrical power demand (and thus the need for 60% of its generating capacity).

[16] Windcatchers are a common feature across many Middle Eastern countries, influenced by the spread of Islamic culture.

In Iran, a windcatcher is called a bâdgir, bâd "wind" + gir "catcher" (Persian: بادگیر).

Towns centered on desert oases tend to be packed very closely together with high walls and ceilings, maximizing shade at ground level.

[15] The evaporative cooling effect is strongest in the driest climates, such as on the Iranian plateau, leading to the ubiquitous use of windcatchers in drier areas such as Yazd, Kerman, Kashan, Sirjan, Nain, and Bam.

The construction of a windcatcher depends on the direction of airflow at that specific location: if the wind tends to blow from only one side, it is built with only one downwind opening.

Council House 2 in Melbourne, Australia, has 3-story-tall "shower towers", made of cloth kept wet by a showerhead trickling at the top of each one.

[19] The Saint-Étienne Métropole's Zénith is a multi-purpose hall built in Auvergne-Rhône-Alpes (inland southern France).

[34] A windcatcher has been used in the visitor center at Zion National Park, Utah,[35] where it functions without the addition of mechanical devices in order to regulate temperature.