Self Cooled Water Storage Tanks

You need something that is porous to allow some water to evaporate. a course sand concrete mix or masonry tank may give the appropriate results.

a normal tank could also be surrounded by stone ore cokes (burned coal) contained by wire mesh. with a Small stream of water being dispensed over it.

I has been done at 46 degrees C in arid parts. It will be less effective in humid areas.

In the arid parts the people complains that it is xx degrees in the shade.

my reply was then "why do you stay in the shade"

I agree with Hendrik... but in case of going for the 2nd alternative, the normal tank must be of a heat conducting material such as steel and the like. If the material used is again a insulator...cooling effect will not be much

Rgds

Chockalingam, India

Hendrik thank you for your suggestion, but I am looking for some kind of material that is a barrier to sun heat, without the need of additional materials added to the water tank or putting refrigeration unit etc. Like there are "solar shade" screens to put on the windows. It allow the air to flow through but around 80% of the sun's UV rays are blocked out. This solution wouldn't cool the water, but it would stop the sun from boiling it. I have tried this, but actually I am in search of some kind of water tank whose material is as such that it doesnot allow sun heat to penetrate.

The evaporation is caused by a loss of internal heat energy of the water which results in a drop in temperature. Thus you need to ensure there is plenty of dry air to circulate around the vessel - but also to keep the vessel in the shade (to stop it heating up by radiation from the Sun's rays in the first place).

Unglazed earthenware pots are well known for the ability to keep water cool in the desert (there is plenty of dry air) but only if you have a supply of water.

As mentioned elsewhere, this technique is not so good in humid conditions. This is because the water will not readily evaporate from the surface of the vessel.

You could achieve a similar effect by using a watertight vessel arranged to have a thin film of water flowing over the outside surface. You could end up with a forced draught evaporative cooling tower.

Good insulation will slow down heat transfer, though it won't stop it completely. There may be scope to try evaporative cooling, depending on local wet-bulb temperatures. To achieve and maintain a temperature that is below the local wet-bulb temperature requires refrigeration equipment.

You might want to try using magic!

have a look at common everyday chest freezers. i've left ice for weeks in them in the sun with a loose lid. the ice evaporated befiore it melted! took several weeeks for 2 bags of ice!

I suggest you use the same foam insulation. 4" or 100mm all round would be sufficient.

In addition to which,

http://www.freepatentsonline.com/5811180.html

a paint that resists infra red penetration.

Mark

Khan, If you find a Self Cooled Water Storage Tanks e-mail me with details.

Thanks,Gerard.

The simplest and most cost effective thing you can do is simply build a roof over the tank and use white roofing material and use the same material to build walls around the tank unless you are willing to purchase a wood tank for this water storage and the wooden tank will allow for easy painting with food grade paint on the outside.

Another option which also lends itself to this is to purchase a prefabricated tank and cover system that is panelised with a liner from the folks at Modutank www.modutank.com they ship all over the world and the tanks are easy to assemble and are easy to insulate or you can purchase insualtion from modutank for the specific tank you desire. no skilled labor is required to install and erect the tanks either.

A rather large Thermos Bottle should do the trick. It resists temperature change of all sorts and if you had one with a vacuum inside it would be quite efficient.

Old windmills used to have above ground open top wooden tanks. Even in west Texas the water was quite cool on the hottest of days due to evaporation. Course they got a little dusty when a dust storm blew in.

Folks in the dessert put their water in skins or a type of canvas bag. That works too.

jh

I have been inside a steel water tank inland from San Diego, 110 degrees outside and the water was cool inside. I believe this was due to a combination of things including: a good heat reflecting paint outside, some shade on the sun side of the tank, the tank was located in a small canyon like area where the cooler air would come down the canyon and sweep around the tank while the warmer air rose, and most importantly, the water was constantly circulated. I believe the circulation allowed the heat to dissipate more rapidly through the roof vents. Therefore, specific location of the tank is very important, as well as the features of the tank itself.

Firstly where are you located, then how big a tank, the bigger the volume the better.

Next make it so it is covered, apply silver paint so as to reflect the suns energy.

A cylindrical shape is the best for surface area to volume, having a double skin with insulation in between will further help. Keep it full, watch out for mosquito lava and legionnaires disease. Use refrigrated water to fill it?

The water in any tank can be kept cool by preventing the heat and sun to get to it

Our old houses in warm parts is always nice and cool inside because:

The Walls are 500mm or more. (heat cannot penetrate easily)

Floor to ceiling ±5 m (warm air rises and further away from radiation)

The walls must have ventilations bricks top and below.

the roof has air inlet outside - below with outlet on highest point. (continues air flow)

Thick wooden ceiling.

The solution may be impossible or costly.

A workable solution might be to construct a round thatched roof over and around the tank. with vent points below and a vent outlet on top. This should help and will also be esthetically pleasing.

Why not uses the heat to cool the water?

Long ago we all had fridges powered by a little flame.

heat = expansion = increase in pressure.

pressure release through orifice = cooling.

As silly as it sounds the simple old fashioned corrugated iron water tank has done this job well for generations. A little shade helps. The tank seems to radiate enough heat at night that the water in the bottom remains cool.