EN - How to use a pyrgeometer?

Question

I want to close the curtain to prevent long wave heat emission.
How to use a pyrgeometer?

Answer

If you are wondering what a pyrgeometer is and how it works? Read this article first: How does a pyrgeometer work?

The pyrgeometer can be used to close the screen (earlier, already at a higher solar radiation level) at the end of a day. The screen will protect the crop against too much long wave heat emission. There are several approaches to get this done.

It can be achieved by using the ViP influence at the energy screen setting list: pyrgeometer: measurement – W/m².

In order to close the energy screen at an earlier stage, this influence is used on the ViP setting: ‘energy curtain: ViP radiation close’. Check the example below:

At a high emission rate, over 100 W/m² the screen will get closed if the solar radiation gets below 100 W/m² instead of 100 W/m²(provided that the outside temperature is low enough).

When the curtain is closed earlier in the afternoon, make sure you pay attention to the greenhouse temperature. Closing an energy screen at an earlier stage might cause a substantial high greenhouse temperature. We recommend to let the screen only partly close, by setting a crack of 20%. As soon as the greenhouse temperature decreases, the size of the crack also decreases.

In the second place you can make use of a custom alarm. Rename this setting list in 'Nett radiation measurement'.

The outcome (3) is based on the influences radiation (1) and emission (2) that have been selected. Check picture below.

When the nett radiation arrives at zero, the emission is as big as the radiation, the screen should close. By means of this influence, the screen already closes at higher outside temperatures. In this example below 11 instead of 5 degrees Celsius.
Please check the level of the radiation closing condition as the actually measured radiation should be less for the screen to close. Increase its value with at least 50 W/m².

The advantage of the second approach is the calculated value of the radiation and emission. This value is also vacant for graphics.

Threre is a third method as well, making use of uni-switches. Contact your technical partner to find out the best way to get this done.