Great emphasis on the lo-tech easily maintained and repaired solution. Unlike this popularized concept: http://starwars.wikia.com/wiki/GX-8_water_vaporator

There have been other products, including some on the market for using solar power to run refrigeration systems to condense water from air. The two factors of efficiency--amount of water produced--vs. price and simplicity of maintenance mean there could be several niches for water harvesters depending on the economy and investment climate of the community in question.
I hope this method is as promising as he feels it is. It is worth bearing in mind that when a new and improved solar cell is developed, it should not only be judged on whether it will be economical for solar cell farms attached to the grid but also on whether it can provide more power at less cost to off-grid systems and devices like these.

It would also be usful to pair this with a subsurface moisture barrier beneath the irrigation since deserts often lose more water downwards that through evaporation.

I can see this working in hot humid conditions assuming the ground temperature doesn\'t rise too high but what about hot dry conditions?

It would only work until the surrounding soil heated up, and the vapour ceased to condense.
Places like the New York and London underground railways were originally cool, but they have become hot and sweltering as the years pass, as energy is pumped in from bodies and trains.
http://www.thisislondon.co.uk/news/article-19451133-tube-is-hotter-than-miami.do
I imagine the efficiency of the Airdrop would quickly fall with use.

What an excellent idea! This reminds me of the water harvesters in Star Wars that the young Luke Skywalker had to tend for his family.

This has been done already a long time ago by uncle Owen and Aunt Beru in a galaxy far far way.

How much copper or aluminum will be needed per acre for the heat exchangers?

Am I the only one that sees that removing water from the air increases the area of the rain shadow.

lets just hope he changes from copper...because thats one expensive solution with coppers prices. theres a reason why wires are stolen from railway lines....