A closer look
Those ominous, gargantuan concrete silos spewing white clouds at power plants aren't shaped like hour-glasses just for aesthetics. The hyperbolic curve relies on natural thermodynamics. The wide bottom rapidly draws in freezing outside air, and as the hot steam rises, the cinched waist vigorously accelerates the airflow upward without requiring a single mechanical fan. It is just an exceptionally massive, completely passive concrete chimney designed to throw waste heat into the clouds.
