At first we thought this place reconditioned old propellers for use as engines on airplanes. Turns out, they are reconditioned to be used as frost protection in vineyards. The photo was taken in St. Helena, CA, wine country. They're mounted on tall supports, over the vineyards. When frost arrives, they're turned on, moving the air and preventing damage to the emerging grapes shoots in spring.
Propellers on parade
in California