Frost Fan

A structure designed to protect orchards and vineyards from frosts. A frost fan consists of a Tower, Blade an Engine, an Engine Auto-Controller and a fuel tank. We use ‘frost fan’ in general conversation to describe the whole unit.

A frost fan’s job is to send warm air from the inversion layer (aka ‘thermal ceiling’) down to the canopy to prevent frost from taking hold and damaging crops. In order to start and stop, a frost fan needs to know the wind speed as well as the temperature.

This data comes from two sources. Wind speed comes from an Anemometer located at the top of the tower. Information is then fed directly to the engine auto-controller. Temperature is gathered from a Temperature Probe located in the coldest-known location within the canopy (determined based on a site evaluation and meteorological data). This information is transmitted from the Canopy Radio to the Tower Radio it is paired with, and then to the engine auto-controller.

There is also an auxiliary temperature probe located at the top of the tower. Its job is to monitor the temperature up there, and feed information to the engine auto-controller. At night, the air temperature at the top of the tower is typically warmer than the canopy. This is important because the difference between the two temperatures determines how efficiently the fan is operating. The larger the gap, the more efficiently the fan will perform.

A frost fan can operate in three different modes: auto, manual and monitor. These modes are controlled by the Engine Auto-Controller and determine how and when a frost fan is activated.