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Ask Slashdot: Large-Scale DIY Outdoor Cooling of Cairo's Tahrir Square?
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."
Making shade is the obvious solution. Anything from portable gazebos to improvised Berber tents to poles and shade-cloth. Shade is going to be more efficient than anything else at keeping people cooler.
If water can be spared, a fine mist of water in one part of the square would let people who have gotten too hot cool themselves down.
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Pheonix Az & several other cities use tall evaporative towers to cool plazas -- pump water to the top & let it cascade down over tera-cotta tiles. The evaporation drops the air temperature and the cooler air combined with the dropping water forces the cooler air out the bottom of the tower.
Water evaporating from clothes. Arrange for fire service to spray people with water from the trucks. This is quite common in outdoor festivals - the car moving very slowly through the crowd, and firemen pouring a mist of water over the crowd. This suffices for a hour or so, can be repeated as needed. Also, if anyone faints, or feels otherwise ill, they can be handed over to the fire truck to be taken out to a medical station..
Otherwise, if you can't get cars, just get a bottle of water for yourself and pour it over yourself from time to time.
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Wouldn't that add to the heat? The waste heat transported by Peltier elements needs to be moved somewhere else, otherwise you'll just get more heat stemming from the thermodynamic inefficiency of the process.
Sure, the hot air might rise upwards and the tents might gain some cooling from such a setup, but I think this needs testing in real life in order to determine whether the real effect will be that of cooling, or warming.
And be part of the solution, you lazy smelly hippies.
If you were blocking sigs, you wouldn't have to read this.
Let's see... something that reflects heat, and has other possible benefits against an abusive government... hmmmm...
Have you considered a tinfoil hat?
And that's why the original question strikes me as stinking of colonialistic snobbery. OTOH, if some genius here can somehow, with only second- to third-hand knowledge of what kind of resources are really available and what conditions are really like over there, come up with a solution which will make their life easier, I'm all for it.
I'm not holding my breath.
Spray a firehose upwards through something that will make a fine mist. Most will evaporate, sucking vast amounts of heat out of the air, which will flow downwards onto the crowd, along with the remaining chilled water. You want pressure rather than sheer volume.
Burlap/canvas tents can be cooled with a constant trickle over them in the same way.
Slightly less messy might be a series of hoses that carry chilled water from a tank out to modified hot-water-bottles strapped to people, and then away again, maybe even back to the tank to close the system. Rip a few fridges apart and put the cooling pipes in the tank. Run any waste water over the hotside pipes and then into the drains.
It's like CPU cooling, just on a larger scale: :-)
Jeremy Lee | Orinoco
A couple of years ago in Penang I took a tour of the botanical gardens. A short section of the tour took us through a stretch of native forest. The microclimate in the forest was much more comfortable than other areas. So break up the concrete and replace it with trees. I know this may not sound very feasible in the short term but it is the only way to beat the climate in the long term.
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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.
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.
If you don't know what you're doing, you can't make mistakes.
slighly off-topic: two major cities - tel aviv and bangalore - cut down large numbers of trees in order to make room for more people. the immediate result was a rise of 10 Centigrade in bangalore (from 45C to 55C). in tel aviv's case, not only did the temperatures rise but also migrating birds no longer have a stop-over point half way along their route between the two hemispheres.
not that planting some saplings in a public place is going to help in the immediate short-term, i appreciate...
The following is what I have done at Burning Man festivals in the past.
1 - space blanket.... Yes a space blanket. they reflect 98% of Infrared and visible light. it makes a HUGE difference in the desert heat.
2 - water soaked white neck wrap. The evaporation effect of that wet cloth around my neck makes a GIANT difference in low humidity.
3 - water soaked white turban. Again.. Evaporation is your friend.
4 - white umbrella..... seeing a trend here? if you are in bright sun the best thing you can do is reflect as much of it's energy away from you as possible.
5 - wet clothing.. Again white, again wet.... isn't physics neat!
The biggest problem is pesky deserts dont have a constant supply of water. Someone needs to complain to the planet engineers about this oversight.
What I have discovered is that most people that live in those regions already know how to keep cool. It's the idiot Americans that cant understand why people don't die instantly when they dont have AC in their cars or homes that cant figure out how to stay cool outside.
Actually that was unfair. It's pretty much any Idiot that is lacking in education and lives in a 1st world society no mater what the country.
And yes, I am an American... Most of us really are pretty stupid when it comes to common sense and life skills.
Do not look at laser with remaining good eye.
Slight correction. No-one is sucking the Dead Sea - the water is so salty that even desalination is impractical. The level is dropping due to diversion of the incoming Jordan River. The blame for the resulting drop is shared between Israel, Jordan and Syria - all three of them draw large quantities of water from the Jordan River, so there isn't much left by the time it reaches the Dead Sea.
It's a nasty political mess. The 1967 Six Day War was fought because of that river. At the time, Israel drew most of their water from the river (They still do) - but Syria was upstream, and started constructing a project to divert the river for themselves. This would have completly destroyed Israel's agricultural industry and rendered parts of the country completly uninhabitable without an investment of tens of billions of dollars. When diplomacy failed to convince Syria to halt their plan, Israel launched a series of air-strikes on the constuction sites.
You can blame whoever you want, but it all comes down to the need for fresh water in a part of the world where there just isn't enough of it to go around. When such a vital resource is in such scarcity, evey country will do anything they can to secure it for themselves regardless of the consequences for others. The alternative is drought and mass-starvation, and that is no alternative at all.
I'm in Taiwan right now. People here sometimes spread water all over the ground (though they do it in Japan a lot more). With enough people doing it, you can really cool the air in a local area just by watering the hot asphalt and letting it evaporate. Otherwise, people just stay in the shade. There are some misting tents, too. And, of course, big straw hats (though I don't think people in the middle east need help on dressing appropriately for hot weather, they seem to have had that covered for thousands of years).
And that's why the original question strikes me as stinking of colonialistic snobbery.
Just because someone asks for help and thinks there might be a novel answer an expert might think of, even if it's a question it would have been nice to have an answer to any time in the last ten thousand years, doesn't mean we should call him a snob for asking. Ignorance or shortsightedness is not necessarily snobbery. The pursuit of knowledge should not be punished. Nor should he be called a colonialist, for that matter--he didn't advocate taking over the place.
Me, I'd go with shade, big fans, and ice-cold beverages. But I don't know if there's too much sand for the fans.
-- IANAL, this isn't legal advice, and definitely isn't legal advice for you. Also, Squee!
As with all technological problems someone at Burning Man has already prototyped an elegant solution.
The goal is to keep people cool, not a place. Here's one cool option (pun intended).
People have been making "cool ties" for several years now. Basically a cloth tube with a little bit of water absorbing polymer inside (available at gardening centers in the US). They hold a lot of water and create a little evaporative cooler for your neck. Like soaking a towel, but more water with less dripping.
People make them and send them to soldiers in Iraq and Afghanistan. there are versions for necks, helmets, even vests.
Here are some detailed instructions: http://www.watersorb.com/polymer_cool_neck_bands.htm
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