How could orchard fans help frost protection?

Frosts are cold weather conditions, of relatively short duration, during which organic material may be damaged by exposure to surrounding air temperatures lower than 0°C. At the same time, orchard fans have become the central element in most frost protection strategies. This article will introduce you to more information about the function of orchard fans when it comes to frost protection.

The Content list:

1/ How do orchard fans work

2/ Frost protection by utilizing orchard fans

How do orchard fans work?

In the lower atmosphere, temperature generally decreases with height; But under the condition of early spring pollen, the ground because of radiation cooling and cooling, the closer from the ground, the faster the air cooling, and the upper air is affected by the ground the weak, slow cooling, temperature increases with the rise of the height of the trend, this phenomenon is called "inversion phenomenon" under the condition of the germination of fruit trees fight cold ability is reduced, the buds in 0°C or so will be affected by mild cold injury, 39°C -29°C when severe cold injury ".

Orchard fans work by utilizing warmer/drier air from the 'inversion' layer to create air movement at the fruiting/flowering height in orchards on still cold nights—preventing damage to flowers, soft tissue, and fruit. Many growers have moved away from using water sprinkling in preference for frost fans.

Frost protection by utilizing orchard fans

Damaging frosts typically occur after a cold, cloudy day followed by a still night with clear skies. The earth quickly radiates any stored heat after sunset and an ‘inversion layer occurs with the air being coldest near the ground with a warmer layer of air above it. The degree of injury depends on the minimum temperature reached, the rate at which the temperature falls, and the amount of time below a critical temperature. However, it’s not all about avoiding catastrophic loss. The aim is also to protect against cold injury to increase a grower’s current yields and improve the quality of the fruit, whilst ensuring continuity of supply or shelf space.

Frost fans are a well-proven technology for mitigating the devastating losses that can occur from a significant frost event. Many growers use frost fans as a tool to combat cold injury by programming them to start automatically based on a preset temperature. Where once frost protection systems would have been used only when a serious frost was forecast, now frost fans will start automatically to prevent damage from cold events that may only last a few hours in the middle of the night or early morning.

They use the warmer air in the inversion layer to protect a crop from frost damage. Orchard fans get air from the inversion layer down into and mix with the freezing air at ground level. They have gained popularity lately because they can be used at any time and are energy efficient. Frost fans, on average, cover 10 to 13 acres per fan.

Frost fans are turned on before a frost occurs, usually 0.5 to 1.5°C above freezing. There is documented proof that turning on frost fans early and shutting them down late, results in considerably better crop protection performance. Substantial crop salvage has been achieved with a “slow-freeze-slow-thaw” even under severe frost conditions.

In severe conditions, the use of orchard heaters in conjunction with frost fans strengthens the useable inversion layer which the frost fan then mixes and distributes over the crop, thereby providing better protection.

The initial expense of protecting a large area with frost fans can be significant, but the cost of capital, maintenance, and operation is comparatively lower than other types of frost protection systems.