One I was thinking of yesterday – a vented ridge cap on the top of a house’s roof will let hot air in your attic flow upward and out the top, drawing in cooler air along the eaves. So was wondering if home AC systems could use this airflow to draw air over the exterior coil and reduce the energy needed to run a fan. But a bad side effect would be adding extra heat to you your attic.
So the next thought was, just build either a series of “chimney” tubes, or even just join the tubes together to form a large thin chimney which could cover an entire wall of a house, and would let the hot air entering it from the bottom out of the AC coil to flow upward and pull more air through the system, thus again eliminating or reducing the need for a fan. This could also act as a sunshield for one side of a house, and the funny thing is sunlight would even enhance the effect (heating the chimney causes extra airflow).
So i did a quick search and confirmed my suspicion that this is old news..Patent 4706471 for a “Solar Chimney” uses solar energy to heat a chimney and produce airflow to aid in cooling an AC system, though this particular one seems to be focused on geothermal. (See http://www.google.com/patents?id=NsAwAAAAEBAJ&dq=4706471 ). This is after a 15 second search, so Im sure there is lots of other related tech out there. I may add more here as I find time to look into it.