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I would like a bit of a review of my ideas and would appreciate it if anyone points out a serious fault with them - see ideas below:

Transporting moist air by means of natural convection in a pipe: Run a huge black pipe, that will get hot in the sun, from the sea to a few hundred metres above the area needing rain. Moist air from the sea will rise in the pipe by means of natural convection and cause convectional rain. This idea could bring rain to many areas. It would be similar to a solar updraft tower, which can deliver huge volumes of air per second to the atmosphere. Heat the seawater by concentrated solar power (or other means) near the inlet of the pipe to increase relative humidity. This system will be cheaper than solar updraft towers. Some calculations: For a 20 m diameter vertical pipe that is 500 m high with air temperature of 25 deg C outside and 30 deg C inside, a flow of about 3340 cubic metres per second can be expected. Eventually you will have a few cubic kilometres of moist air in the region if wind is weak. To do your own calculations search for "stack effect draft."
One could have a few such pipes into a region to spread humid air. One or two cubic kilometres of moist air per day can be delivered like this. Pipes could be heated more by reflecting sunlight onto them with mirrors. Rocks that the pipe rests on could be heated by solar energy so that the pipe stays warm at night and can keep on delivering moist air. It is quite likely that at night the air from just above the sea will be warmer than land air, which will cause it to rise in the pipe. Moist air is less dense than drier air, which will help it to rise in the pipe.
But here is another idea. In desert regions with hot air one can significantly change the density of the air by increasing relative humidity, because hot air holds so much water vapour and water vapour is less dense than air. At a temperature of 40 deg C with RH of 30% and P=101.325 kPa, air has a density of about 1.118 kg/cubic metre. If you raise the RH of this air to 90% it has a density of about 1.099 kg/cubic metre. This is the same as air with an RH of 30% and T=45 deg C. By increasing the RH of the air with RH = 30% to one with RH = 90% (all at T=40 deg C) you have about the same effect on density as raising the temperature of the air by 5 deg C ( from 40 to 45 deg C). In hot deserts It seems you do not have to heat the air to cause natural convection - you can just increase RH and the air will rise by natural convection in the pipe. The RH can be increased by heating seawater at the inlet of the pipe. At T=40 deg C with RH=90%, there are about 46 grams of water vapour in every cubic metre of air transported in the pipe.

What happens when the air comes out the pipe? Well, say the air with RH=90% and T=40 deg C comes out in air with temperature of 35 deg. Clouds will form with bases at about 245 metres above the outlet of the pipe (very low clouds). The clouds could display huge vertical ascent from their bases because of high RH, high dew point and so on (tall clouds with low bases and towering high tops will result). If a rain cycle results maximum, temperatures will be reduced by evaporation and minimum temperatures will increase because of increasing effective sky temperatures. 
This depends on strength of sunlight, temperature of water coming into the greenhouse, heat losses and so on, but it seems that to form 1 cubic metre of 90% RH air at 40 deg C starting with 30% RH air at 25 deg C, every second, will take very roughly 200 square metres of surface irradiated by the sun. A massive greenhouse with water in could suffice to provide all the humid air needed. Similar greenhouses have been proposed for solar updraft towers. A greenhouse 1 km by 1 km could provide 5000 cubic metres of RH=90% with T=40 deg C air every second.

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  • 3 years later...

I posted the following on Swayseeker "heat air at ground and air will rise " thread; I think I should have posted my reply here......

 I think Swayseeker has a plausible idea. The good example might be the Salton Sea and the peak of the Oronocino? Mountain just east of the sea. Swayseekers tunnel might be a plastic covered greenhouse funnel/tunnel/chimney  that runs(10 miles ?) from the Sea surface to the peak (3500 ft?). With local heating of the sea, moisture laden air begins to rise and move through  the chimney delta that may cover several acres immediately above the surface of the sea and into the chimney stack at say 10:am and continues until near 5:pm on a summers day. The plastic framed stack winds along the ground up the mountain ridgebacks and at some point (elevation 2000' ?)the temperature of the plastic walls of the chimney stack fall below the dew point(added now:dew point of the air/water vapor in the chimney/tower) and water vapor condenses on the walls and runs back down hill to some collection point. The latent heat released keeps the chimney draft working to pull in more moisture laden air at the sea level. The pathway of the chimney will have to be maintain uphill always to keep the draft from stalling out. That covered pathway, with a cool and moist environment, could make an interesting hiking path. Didn't Swayseeker talk about this in another thread?

California needs every drop of fresh water. Wouldn't that tiny stream of water be useful now in this horrific drought.

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  • 3 weeks later...

President Biden's infrastructure plan doesn't have any ideas about the need for water infrastructure for the western states. Research grants for ideas like Sawyseekers would be something to add to the legislation. Another idea is a national network of aqueducts to connect wet and dry areas. Consider an aqueduct right down the middle of interstate I10 from Northwest Florida to Phoenix Arizona. The federal government already has the property rights of way. Florida, Alabama, Mississippi, Louisiana would like to sell their excess water to Arizona. West Texas, and New Mexico would like to buy some of that water as well. With Phoenix getting all of its' water from the aqueduct, Colorado River water could go to other users; mostly California. The aqueduct could be open ditch with a lesser capacity in enclosed piping; sparkling clear water from Florida springs in the pipe for home use in Phoenix. Agriculture quality water from the hundreds of rivers and streams of the Gulf Coast flows in the open ditch. The water in the ditch can also serve as a energy storage mechanism; when electrical demand is low, the wind and solar energy produced in this region is used to pump aqueduct water up to storage reservoirs. The stored water is then released for electrical generation during the heavy demand daytime hours. So the cost of aqueduct pumping is minimized.  

If the nation can build multiple east-west transportation interstate hi ways, why could we not build at least one big water aqueduct from east to west?

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