It might be this:

http://en.wikipedia.org/wiki/Energy_tower_%28downdraft%29

Thanks for the link! Citation: "Currently, no known physical implementation of an energy tower exists."

The article refers to another similar concept: http://en.wikipedia.org/wiki/Solar_updraft_tower

"A research prototype operated in Spain in the 1980s."

These designs are quite silly. In fact the best location for a solar updraft tower is in between the forest floor and it's canopy. In fact, there are already billions of implementations of concept, taking advantage of the entropy differential between the strata of forest biospheres: trees.