Does a second energy screen save energy in tomato growing?

The companies deal very differently with their climate settings and the control of the screens. It turns out that the use of a second, movable energy screen saves 3 to 4.5 m3/m2 per year, or 9-14%, on heating, depending on the number of screen hours that is being used. The number of screen hours of the second screen varied from 1,100 to 1,700, of which 100 to 1,000 completely closed.

The departments with a second screen have 15W/m2 less usage during the coldest day, making a gas capacity of 17m3/ha a possibility. The k-value for two closed screens is 26 to 38% lower than for one closed screen. An analysis has also been made of the difference in temperature above and below the screen tarpaulin. It turns out that the screen position has a significant impact on this difference.

Loss of light
Because the screens have only been used during low light intensity, they have only blocked 0.6 to 1.3% of the light. During December 5th 2016 to January 21st 2017 10% of the total amount of daylight was lost. The calculated loss of light does not include the light the screen installation blocks in opened position.

Only just not profitable
Besides the screen use it is mostly the other climate settings and the cultivation strategy that determine the energy use. Particularly the Moist Deficit in the night is decisive. Cultivating dry costs more energy. The conclusion is that the energy savings of the second screen is only just not enough to recuperate the investment (at similar production) and certainly not if it is assumed that the shadow effect of the installation leads to 2% loss of production. The flexible deployment of the second screen and a uniform and less dry greenhouse climate in the winter are more important arguments than energy saving for investing in a second screen.

Source: Kas als Energiebron