Passively moving air I'm interested in channeling air into an underground condenser to generate water. Which of these approaches would be most appropriate, and is there a better approach I haven't considered? A: A wind-powered turbine, which mechanically drives a fan. I would most likely use a HAWT, with a gear to change the spin direction from horizontal to vertical. HAWTs seem to be the most efficient tested wind power system, although there are pure-vertical alternatives, which would eliminate some moving parts. However, the efficiency claims I've read refer to electricity-generation, where shaft work is the desired output, rather than air flow.
B: A funnel-type intake that faces into the wind, or is omni-directional. It would channel air downwards into the system without moving parts, other than its wind-orientation. This seems like it would avoid efficiency losses in A caused by converting moving air to shaft work, then back to moving air. However, the wind may be largely diverted around the intake, since it would act as a blockage.
C: Use a static airfoil, or other surface to direct air into the system, without acting as a blockage.
A: It's a good question, and I would be inclined toward B or C.
You are worried about blockage, but I view that as an issue of aerodynamics, like the difference between a lifting airfoil and a stalled airfoil.
If you are not asking the air to follow sharp turns, so the flow doesn't separate, you should be good to go.
If you do need to make the air follow sharp turns, you can put vanes in the tube, to direct the air around the bend. This is what's done in closed-loop wind tunnels.
