Saturday, April 27, 2013

Rain and Snow from Cloud Seeding

Cloud seeding is done to increase precipitation in areas where extreme drought or long-term scarcity conditions exist.
Typical inorganic seeding nuclei
Cloud Seeding
Source - en.wikipedia.org
Most seeding procedures use inorganic particles or artificially produced organic particles.
AgI Molecule
Source- axcessbio.com 
Silver Iodide (AgI) is a commonly used inorganic condensation nuclei.
Dry Ice (solid Carbon dioxide) is another inorganic nuclei commonly used.
Artificial Precipitation Process
Precipitation Process
Source - en.wikipedia.org
For rain to fall upon demand i.e. for artificial cloud seeding to work, the air needs to contain super-cooled water. Super-cooled water is liquid water colder than zero degrees Celsius.
Silver Iodide has a crystalline structure very similar to that of ice and it is assumed that existence of this structure induces freezing temperatures that convert water vapor into super-cooled liquid water.
Dry ice achieves the super-cooling effect by its expansion that in turn super-cools water vapor.
Rainmaking using silver iodide or solid carbon dioxide both require existence of liquid droplets in super-cooled air.
These initially miniscule liquid droplets serve as the base for liquid and ice droplets to grow to a size large enough that they end up falling to the ground.
Cloud Seeding Goal
Lots and lots of rain is the goal of cloud seeding. Humanity cannot, however, capture much, if any, of this rain and, typically must wait for hydrological processes that add this artificially produced rainwater to existing reservoirs of liquid water that are water is being drawn water from.
Obviously, cloud seeding is an option for supplying multiple acre-feet of water rather than the few liters each individual requires.  

Saturday, April 6, 2013

Cotton Fabric That Absorbs Water From Air?

We know that moisture in the air is 2% in liquid form and 98% in vapor form. This ratio improves a bit - by another 1% or so - in favor of liquid water when a mist or fog rolls around.
For some reason, humanity has continued to focus on capturing the liquid water in air while there is no research on capturing the water that exists as vapor.
Now word comes of a new polymer that does just that.
What's a polymer?
A Polymer (multiple copies of the same unit
Source - ec.europa.eu
Covalent Bond
Source - en.wikipedia.org
A polymer is a compound whose structure is characterized by copies of the same units connected by covalent chemical bonds. A polymer, thus, is a collection of a number of copies of the same unit. 
The covalent bond is the sharing of two electrons between a carbon and a hydrogen atom that each contribute one electron to the coupling.
The New Polymer PNIPAAm
PNIAAm cotton fabric
Left (closed structure at high temperatures)
Right (open structure at low temperatures)
Source - Endoven University
Researchers at Netherland's Endoven University of Technology and at Hong Kong Polytechnic University have together created a new polymer they call PNIPAAm.
When this polymer is applied to cotton fabric, like a cotton shirt, the resulting combination is much more absorbent of liquid water from the air, than is the cotton alone.
The combination can absorb as much as 340% of the cotton weight of water. Cotton alone absorbs about 18% of its weight of water.
Key area of continuing research is the temperature at which the combination starts absorbing and releasing water and building actual clothing to check how the results from the test-beds pan out.