Water from the sky... and we are not talking about rain

I saw this article ‘Sky water' plant a boon for people of Sidlaghatta (The Hindu, 22 Mar 2010) about "a new technology that is reportedly making waves in the U.S. and European countries". Put simply, it is a big condenser that converts the water vapour in the air (aka humidity) into clean liquid water, extremely useful for rural populations with no access to safe water.

Actually, don't you think this is similar to the Dragonfly from our local brand, Hyflux, introduced a few years back? Granted, the Dragonfly is designed for a small family/office (up to 24L per day according to specs) while this sky water plant can crank out 1000L per day, about suitable for a small village. Nevertheless, the operating principles are the same.

Cost wise... sky water costs 10 paise per litre (~ SGD3 per cubic metre (m3), 1 rupee = 100 paise). Our domestic tap water costs SGD1.52 per m3 (including tariff) while newater sold to industry costs SGD1 per m3. (Desalination costs about twice that of the newater process so the price probably follows suit. Based on a ST article in 2004, desalinated water costs SGD0.78/ m3.) No, sky water is not cheap by our standards but when water stands between life and death, any price is cheap.

Incidentally, I do have some concerns about this technology, especially when applied on a large scale, say for a town or (heaven forbid) a city. When you start to draw this large amount of moisture from the atmosphere, what are the effects on the water cycle? Will we have less precipitation which leads to less water for our reservoirs, hence ending up with a zero sum game? Will less moisture in the air lead to larger fluctuations in temperature between day and night since water vapour acts as a buffer in air temperature changes? What will our neighbours say - that we are stealing water from the air which is supposed to pass over them? And I am sure there are many other unintended consequences beyond my imagination.

Figure: Water cycle (from http://cd7.e2bn.net/e2bn/leas/c99/schools/cd7/website/images/bp-watercycle2.jpg)

Though the above scenarios sound far fetched at the moment, they do somewhat mirror the process of drawing groundwater in many countries. An excessive withdrawal will lead to all sorts of problems e.g. sinking land, salt water intrusion, dried up surface soil prone to combustion.