Highly transparent Luxous screens are frequently used by pepper growers. Until now a single screen has been the most popular setting. However, rising gas prices have increased the number of growers installing two layers of screens. This is what grower Arno Bross did at Het Wilgenbos in Bleiswijk, the Netherlands. The results were instant - reduced energy consumption and an improved greenhouse climate.
Het Wilgenbos has been using Luxous screens in the 7.2 ha greenhouse for many years. Arno Bross decided to add one more layer of the same screen last year. The rising gas price was an important factor behind the decision, but he also wanted to better regulate the greenhouse climate.
Many pepper growers use an anti-condensation folio above young plants. For Bross this was not an option as the crop in the beginning of January was suffering from evaporation. Instead double screens is a better alternative. Naturally, they need to be used in combination with folio during the latter part of the cultivation process.
During the winter nights Bross closed both screens even when the weather was mild. The pepper plants were lit using 3.700 lux lamps turned on at 2 o’clock in the morning. Then one of the screens was opened to prevent the temperature inside the greenhouse from raising too high.
“The second screen was especially useful in the spring when night temperatures sometimes dropped. When it did, we closed the second screen to prevent the plants from getting too stressed, which may result from exposure to the cold”, explains Bross.
The first year with double Luxous screens Bross saved 3.5 m3 per m2 of gas. "When we learn more on how to maximize the use of or two screens, we will save even more. Especially in tough winters”, explains Bross. But energy savings is not the only benefit of double screens. It can also improve the greenhouse’s climate. “The second screen is a fine-tuning tool to get the optimal greenhouse climate and growing conditions”.
Luxous 1347 FR screen, the screen installed at Het Wilgenbos, is produced by Svensson. Frequently used in pepper cultivation, it saves up to 47% energy. On a yearly basis it means 25-30% savings, depending on screen hours. Using double screens can achieve savings of 63%, or additional annual savings of 4 to 6 m3 gas/m2.
Optimal growing environment
Luxous screens do more than just save energy. They also helps create an optimal growing climate. "This is thanks to Luxous’ excellent moisture permeability and light transmitting properties. On a cloudy day the screen boasts a light transmission of 80%, which makes it ideal for use both day and night”, according to Paul Arkesteijn at Svensson. With the two screens closed the light transmission is 64%.
"During cold and dark days it may be beneficial to keep both screens closed, and thus save a lot of energy. However, the grower needs to make the decision based on personal experiences," says Arkesteijn.
Thanks to the high light transmission, the two screens can be kept closed longer in the morning, and Arkesteijn believes it can be beneficial to wait until the greenhouse has warmed up before opening them. “The greenhouse will warm up even with the screens closed and you avoid the sudden temperature drop of opening the screens in the early morning”, explains Arkesteijn.
Double Luxous are popular amongst pepper growers. “The use of two screens, one on top of the other, is a trend in the greenhouse industry, and pepper growers have given double screens a big thumb up, says Arkesteijn. In the beginning of the cultivation process the crop needs high humidity levels. With double screens you can increase the humidity. You can also lower moisture levels by ventilating above the screens." Growers currently use anti-condensation folio to keep the humidity levels down at the beginning of the cultivation period. "The downside of using them is that it is hard to judge when to remove them. It’s easy to be too early or too late. With two screens you won’t have that problem and it’s easier to control the climate”, says Arkensteijn. Due to high energy savings, the return of investment for a second screen is a few years.