It's a good idea, and similar to one I had a couple of years ago. Will, mine was a good idea until I ran the numbers.

I was interested in the Solar Power Tower, which is a 1km tall tower with a (I'm not sure what, probably about 3km)-diameter greenhouse underneath. The solar heat from the greenhouse heats the air, which then rushes up the pipe to provide power through a turbine mounted inside the tower.

My thought was that if I did everything myself out of scrounged materials on a smaller scale, I wouldn't care that much if the efficiency wasn't very good. Well, it turns out that I just won't get enough velocity from the temperature difference (minus the friction loss) to make it worthwhile (my plans were for maybe a 20m tower on a 20m diameter greenhouse, or whatever would work). In addition, it would be too hot in the greenhouse for growing anything (they don't have this problem so much in the scaled-up version).

I don't remember the exact numbers, and I haven't run them for your idea (which needs a higher temperature differential because it wouldn't be vertical), but trust me that it won't be satisfactory.