The solar chimney of the present invention comprises an elongated chamber having an inlet end and an outlet end, the chamber defining a path for fluid, such as air, from the inlet to the outlet. Air updrafts in the chamber drive an internal turbine which is connected to an electric generator, or to some other machine. The chamber has the general configuration of an hourglass; the diameter of the chamber becomes progressively smaller with distance from the inlet end, until the diameter reaches a minimum value, then becomes progressively larger, as one proceeds towards the outlet end. Disposed within the chamber are one or more heat exchangers for heating air in the chamber by solar and/or wind energy.