Ask Slashdot: Large-Scale DIY Outdoor Cooling of Cairo's Tahrir Square? 259
ClimateHacker writes "The struggle for freedom is still ongoing in Egypt and one of the many challenges that face the demonstrators in Tahrir Square is the sweltering heat. Skies are mostly clear and temperatures can reach up to 44 degrees Celsius (111 F) with hardly any shade. The risk of life-threatening heat stroke is quite real. I ask clever Slashdotters out there for novel DIY passive and active ambient cooling techniques. Perhaps some ideas could be a model for saving energy on cooling elsewhere."
Evaporative cooling towers are standard .... (Score:5, Informative)
Re:Evaporative cooling towers are standard .... (Score:5, Informative)
A tall tower open at the bottom to the square and at the top can be made to generate a significant up-draft of air, cooling the street-level. The top of the tower needs to heat up in sunlight to generate the up-draft. This system exists in a number of mosques and old, traditional buildings in Egypt to cool the street-level covered walkways. You need to have a tall building with a stair-well or similar open tower at the down-wind end of the square, and to cover the area leading up to the tower.
All shade and covers should be removed at night to maximise the cooling of the earth, and re-covered when earth has stopped cooling - this can actually be quite late, when the sun is low, and does not mean getting up in the early dawn.
Evaporative cooling, like the bush-air-conditioner, can be used if the local humidity is low. Wet the shading fabric and it will cool with evaporation. It becomes unpleasant as the local humidity rises, so use the minimum water to keep the fabric damp and no water if the fabric stays damp.
Re:Ridiculous troll (Score:5, Informative)
This is not a troll. Or if he is, he has is head unwittingly in the right place.
There have been protests again in Tahrir for about a week. They ramped up on Friday and haven't really abated since. They also regularly happen on Fridays. The Egyptian army have been hesitant to use force again after a few recent incidents which got entirely out of hand. Here's a link to a local English translation daily on the protests this past weekend: http://www.almasryalyoum.com/en/node/475123 [almasryalyoum.com].
It is not unreasonable for protesters in Cairo to be concerned about this sort of thing at all. The biggest protests happened in the middle of the winter when cold is a serious issue, particularly at night. Up until the beginning of July the weather has been quite mild, but just this week we have had two 40+C days. Yesterday was still stifling at 38C. Today is a breath of fresh air (sort of) at 32C, but it is always about 4-6 degrees hotter downtown, even with the river right there. It can be terribly dangerous. It's easy to get dehydrated or to develop heat/sun stroke rapidly without realizing it.
Re:Summary of snobbery (Score:4, Informative)
People generally hang towels soaked in ice water around their neck. We do this sailing down wind here in Texas (no shade, no apparent wind due to the speed and direction of the boat) in the summer. Your neck has two giant arteries in it and quite a bit of blood flow, not to mention the ice water soaks your shirt and gives enormous evaporative cooling. The icewater gives immediate relief and the evaporation keeps you cool for 45 min or more. AFAIK this is a pretty common practice in hot areas.