What is the purpose of the chimney? Why does the chimney need to be so tall?
The purpose of the chimney structure is to prevent the warm buoyant air inside the chimney from mixing with the surrounding cooler ambient air outside the chimney via entrainment. Without the chimney, the warm rising air from the solar collector would quickly mix with the ambient air which would rapidly reduce its buoyancy. The maximum efficiency of a solar chimney is proportional to its height; the taller the chimney, the more work can be captured by the turbine.
