Wind turbine creates water from thin air
http://edition.cnn.com/2012/04/29/world/eole-water-turbine/index.html?hpt=hp_bn7
Not living in an area where water scarcity is an issue I can say that this never really served as an idea for me. However, I have thought about the use of compressed air generated from wind turbines and dealing with the inevitable water that is stored in even the driest of dry air (at least at sea level, at the tops of tall mountains the air can get quite dry), so in many respects I have given this concept a lot of thought, but with the water as a waste product rather than as the target.
Since the amount of moisture any gas can contain is related to the pressure of the gas, anyone who has worked with a compressor knows that you need to bleed the accumulated water from the system on a pretty regular basis or eventually the entire compressor tank fills up and becomes useless. Generally, though, that water is a mess of rust and oil from the compressor and I have never looked at it and thought about having a drink, but I can see optimizing a system to produce potable water fairly easily. I think that for remote ocean islands it actually makes a huge amount of practical sense and is likely an order of magnitude cheaper and easier than desalinating. Since the air surrounding ocean islands is likely to be nearly saturated with water to begin with, I see some fairly rudimentary designs being capable of producing quite a bit of water and I think it might even be possible to design such a system in a way that much of the materials can be produced locally.
As for arid regions like deserts, the air still contains moisture, just less. Often the dew point is at or below freezing (one of the reasons why there are such wild temperature swings in those regions as night time temps tend to dip until the dew point) which means in an arid region some sort of cyclic system would need to be developed (meaning build up frost/ice for a while, then allow to melt, rinse and repeat). The approach described in the article appears to be a bit too complex for my liking as it requires generating electricity and then using that electricity to cool a surface to produce the condensation. I would use compressed air in any system I would design. First, the compressed air has a higher dew point, so it is easier to extract water from it, second, using the neat physics of the vortex tube you can produce cooled air, which, btw, can be used to extract even further water from the compressed air. One of the problems with using a generator is that generators tend to ‘burn up’ if operated outside of their design parameters (meaning too slow or too fast) and to maintain optimal RPM, complicated (thus expensive and high maintenance) techniques are necessary to ensure proper range. Also, there is a critical lower bound that the generator fails (and an upper bound, but that is often dealt with by simply de-coupling the generator from the turbine blades). By going with a pure compressor-based system the complexity and expense of the generator and speed control systems are eliminated and thus a much cheaper and more robust system should be feasible.
As a business I don’t see this being worth huge sums. As a humanitarian effort I see it as something that could be quite feasible and with a very high rate of return. While the water squeezed from air isn’t guaranteed to be pure (after all, there are tons of air-born toxins), I can envision some fairly simple means of excluding almost all particulates, which would probably go a long way to removing almost all toxic sources. A quick look at the web site mentioned in the article (http://www.eolewater.com/) makes me think that they are not going to appeal to the poorer regions of the world. Without exploring their patents it is hard to know if they have some lock on the idea or not (I know that there has been extensive efforts to dry compressed air over the centuries, so I would be a bit surprised if they have anything fundamental). I do see that there could be quite a few ‘well heeled’ customers that might consider a more expensive system, particularly if they are considering other desalination approaches, but I see the biggest bang for society’s buck in the poorer areas of the world where alternatives to produce potable water are based on wells which are likely quite expensive to produce in comparison. I am halfway interested in pursuing something like this, but somehow suspect that once I click on ‘publish’ on this blog entry I will probably forget about it, except possibly to entertain my wife for a few minutes during our weekly too and fro Shenandoah.
Oh well, it entertained my mind for a few minutes…
