Thursday, February 9, 2017

Clean water from seawater and Arctic clouds

People are worried about heating of Arctic regions. In winter the ice can reflect solar energy and cool Arctic regions, but in summer clouds can reflect solar energy in regions where ice has melted (however increased humidity can increase the greenhouse effect). 
One of my "inventions" that could increase the relative humidity (and therefore clouds) is being investigated by a university of technology in South Africa. It could be used for drought areas. 
One can dramatically increase relative humidity by adding water to the air.
Calculations for air at 25 deg C: At a 50% relative humidity in a column of air of base of 1 sq metre and height of 1000 m (1000 cubic metre column) there are 11.5 kg of water vapour. In the same column with an RH of 90% there are 20.7 litres of water vapour. If you can add 20.7-11.5 = 9.2 litres you can therefore increase the RH from 50% to 90%. You need 9.2/1.6 = 5.75 kWh to do this (theoretically, since 1 kWh can evaporate 1.6 litres of water). In a day 5.75 kWh of solar energy can fall on the 1 sq metre base of the column in some regions. With higher RH clouds can form more easily. 

See also my diagram for clean water from seawater. This apparatus could be used to increase humidity of the surroundings if it was used on every rooftop. Note that the idea is similar to the idea of a solar updraft tower with hot air rising, due to natural convection, through the system. Black mesh or gauze could be put into the greenhouse to give a large moist surface for hot air from the solar air heater to blow over. See gives some cloud physics and tells how to spread snow evenly using windbreaks. Snow increases albedo keeping an area cool.
I do not intend to patent my clean water from seawater device, because it is intended to help everybody and I hope people start building it for themselves.

 Here is how you can work out relative humidity problems for yourself: You can use the table at When relative humidity is 50% and temperature is 25 deg (see table) you find that there are 11.5 g/cubic metre of water vapour (this is the same as 11.5 kg per 1000 cubic metres). Likewise there are 20.7 kg of water vapour per 1000 cubic metres when RH is 90% (see my example above). says
"The effect of a thin snow cover is dramatic, particularly in the NIR. Just 5–10 mm of continuous snow cover raised the broadband albedo from 0.49 to 0.81, nearly as high as values measured for deep snow on the Antarctic Plateau, α = 0.83" and "Wind often cleared the snow from the ice. On one occasion a new snowfall of 2–3 cm raised the albedo from 0.42 to 0.88, and on another occasion a snowfall of 1–2 cm raised the albedo from 0.39 to 0.78."
So my idea is to have windbreaks in the Arctic that spread snow evenly and prevent it from blowing away.
My Calculations on Arctic ice/snow, using equations from Fundamentals of Thermal-Fluid Sciences by Cengel and Turner: 
1) Assume solar radiation (direct and diffuse) on snow or ice is 500 W/square metre. 
2) Assume emissivity of snow or ice is 0.97.
3) Assume absorptivity of snow or ice changes from 0.6 to 0.2 when snow falls (albedo increases when snow falls and absorptivity decreases).
4) Assume the effective sky temperature is -20 deg C
5) Assume temperature of ice or snow is -5 deg C.
Then for absorptivity of 0.6 (low albedo) the ice/snow has a heat gain of 242 watts per square metre. For an absorptivity of 0.2 (high albedo) the ice/snow absorbs only 42 watts per square metre. says, "Because the Arctic Ocean is mostly covered by ice and surrounded by land, precipitation is relatively rare. Snowfall tends to be low, except near the ice edge. Antarctica, however, is entirely surrounded by ocean, so moisture is more readily available. Antarctic sea ice tends to be covered by thicker snow, which may accumulate to the point that the weight of snow pushes the ice below sea level, causing the snow to become flooded by salty ocean waters."

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