WeatherSolve Structures - Ultra Span Productive Environments for all Weathers

Wind Shelter

 

WeatherSolve's Wind Shelter Systems:

 

 

Why have a windbreak ?

 

Wind causes erosion, transports dust, spray, and other pollution. Wind also restricts plant growth, damages plants and buildings, and reduces efficiency of heating systems.

 

Windbreaks are used in agriculture for two distinct types of reasons. The first is the obvious macro-effect of reducing the power of the wind which in turn reduces the mechanical fruit or tree damage. Note that this type of damage is caused by windpower. Windpower = windspeed x windspeed.

So, when windspeed is 1/4,  windpower is  1/4 x 1/4 = 1/16
Windpower is what you feel when you try and stand up in a strong wind. Clearly, even a small reduction in windspeed is enough to cause a dramatic reduction in windpower.

Windpower is also responsible for erosion and for transport of spray and dust.

 

The second type of benefit is the improvement in the micro-climate within the grid. This is the actual growing environment. It includes things such as temperature, evapotranspiration and humidity. Wind is another micro-effect that is often over-looked. When a plant is moved photosynthesis shuts down and the plant stops growing. The length of time depends on the plant and the violence of the movement. With grapes for example, a gust of wind of a few miles per hour is enough to stop growth for several minutes after the gust has passed. The effect of these micro-climate type effects is summarized in the graph below.

 

General Information on Wind Shelter

WHAT DOES A WINDBREAK DO?

A windbreak slows the wind in one place by deflecting it to another. The best windbreaks produce a zone behind the windbreak which will have wind of about a quarter of the speed. For a 50ft high windbreak this zone will extend about 250ft downwind. From 250ft to 500ft the windspeed will increase up to about half that of the incoming wind. Beyond that windspeeds increase quickly.

[NOTE the terms windbreak, windfence, wind shelter, shelter fence, and wind screen are used interchangeably here. Purists might see a windbreak as a row (or several rows close together) of trees, yet a fabric or artificial shelter achieves the same thing, so it is easiest to use windbreak as the general term.]

THE WIND

The wind is like a river, with the earth equivalent to the bottom of the river. Water flows and tumbles over the river bottom. The faster the flow, the more tumbling (turbulence).

If we were to throw a large rock into the river, we would create a sheltered spot immediately behind the rock. This is a windbreak in its most basic form. The problem is that just past the rock, the water that had been deflected over and around the rock would come crashing down and in.

 

 

WINDBREAKS

Windbreaks control the amount of "crashing down and in" by letting a little wind flow through. The wind flowing through holds the faster (deflected) wind away for a few hundred feet. This lets the winds merge together again more gently with less turbulence.

The effects are shown in the drawing which shows a side view of a well-designed windbreak and the windspeeds around it.