I have been doing a lot of research on the Internet lately about various desalination processes which are being used today and this led me to begin studying about mountain weather and the orographic effect (or orographic lifting).
From studying mountain weather, the thought occurred to me about whether a lot of fresh water could be produced by creating an artificially-produced orographic effect by pumping warm, humid coastal air through a pipeline that would lead to the top of a coastal mountain.
I then used MS Paint to make a conceptual drawing on how this could be done:
Since the temperature of the metal pipe will decrease as it ascends up the coastal mountain, contact with this colder metal should cause the water vapor within the pumped air to condense on the inner wall of the pipeline and forming water droplets. These water droplets should then be pulled down by gravity and should fall into a pipe leading to a water storage tank.
In the case that one air pumping plant cannot produce enough air pressure to push the air all the way up a mountain, then perhaps another air pumping plant could be stationed near the top of the mountain to assist with transporting the air upwards through the pipeline.
These air pumping plants would probably need to have a large volume industrial centrifugal blower fan like the ones built by Elektror Airsystems pictured here:
I am neither a climatologist nor a scientist so I really don't how much fresh water could be produced this way. I am looking for someone in Earth Science.SE to give me just a ballpark figure of how much water may be produced by this process.
Say that this pipeline is 2.5 meters in diameter, the top of the mountain is 2500 meters high, the air temperature at the top of the mountain is 280 Kelvin, the coastal air temperature is 302 Kelvin, and the coastal air humidity is at 70%.
How much fresh water could be produced by pumping warm humid air through a pipeline up to the top of a mountain?