In the top of the 7.2 ha greenhouse of Het Wilgenbos, a movable, highly transparent screen has been hanging for a few years now. For Bross, the rising gas prices were a major reason for a second screen installation.
In its first year with a double screen, the second screen already provided a saving of 3.5 m³ gas/m². "We haven't made the most of it yet. When after a number of years we have more experience with the screens, I think we can save more. During a harsh winter the savings will be somewhat higher.
The Luxous 1347 FR screen (better known as XLS 10 Revolux) installed at Het Wilgenbos, is frequently used by bell pepper growers and accounts for a 47% energy saving. Take into account the number of screening hours, on an annual basis this will provide an energy saving of 25 to 30%. With two screens on top of each other energy savings will be 63%. On an annual basis that will provide additional savings of 4 to 6 m³ gas/m².
Optimal growth conditions
Another important reason was the ability to control growth conditions. Energy savings and climate control have played an important part right from the start. Many bell pepper growers use extra forcing techniques, such as anti-condensation sheeting. For the early cultivation of Bross this isn't an option. The crop is already evaporating quite a bit at the beginning of January, thus the foil should be removed quickly. A double screen is a better alternative. The Luxous 1347 FR screen not only provides for an energy saving, but also for optimal growth conditions. This is due to good permeability of the screen for light and moisture.
Paul Arkesteijn of Svensson
Other bell pepper growers are increasingly using a double screen as well. "The use of two moveable screens is a trend in horticulture," says Arkesteijn. "In the cultivation of bell pepper, all lights are green for a double screen. The crop loves a high humidity right from the start, this can be created with a double screen. But it is also possible to reduce the humidity. By airing above the screens, the built-up fluid will be disposed of in a natural way.”
To maintain a higher level of humidity in the beginning of the cultivation, many growers use anti-condensation foil. "However, the disadvantage is that it is hard to assess when the foil should be removed. With two movable screens this problem does not exist, and you always have optimal control over the growing conditions," says Arkesteijn. For growers who are screening against the sun, Svensson advises the screen Luxous 1547 D FR. This screen slightly diffuses the falling skylight. In the end the grower will earn back his investments of the second screen within a few years.
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