Aat Dijkshoorn, project leader of The New Cultivation at Kas als Energiebron (Greenhouse as Energy Source), highlights some of the possibilities.
The five priorities involved in The New Cultivation are:
Even climate, dehumidification, appearance, insulation and crop activation. In this first article in a series of five, we discuss the even climate.
Improving the greenhouse climate is important to be able to optimize cultivation. In a more even climate, cultivation can be achieved at higher RH with lower energy consumption. This reduces the risk of condensation in the crops.
Measuring the climate correctly is at the root of the approach. With wireless sensors, greenhouse conditions can be analyzed for a longer period of time. For a good analysis, it’s advisable to work with an experienced expert to analyze the data. In general, there are a number of causes that are responsible for uneven climate:
- Screen vents. In many situations, growers vent in order to get rid of excess heat or moisture. However, these vents cause thermal movements, resulting in isolated temperature drops near the side and hot spots in the middle of the greenhouse. So avoiding vents in the screen is the first step in realizing an even climate. For example, by venting above the closed screen.
- Adjustments in the heater. Because of better insulation and lower tube temperature, heating capacity with a closed screen is often inadequate. The most ideal situation is to adapt the system with a steerable wall heating. But adding tubes in cold places or the insulation of tubes in warm places can also lead to significant improvement.
- Attending to various defects: broken windows, torn screens or wet spots are often the cause of uneven climate. Wet patches cause extra evaporation and higher humidity in isolated spots. Even differences in the structure of the soil can play a role. Covering or insulating the soil (not in soil-bound crops) can provide relief.
- Wind influence. No greenhouse and no screen is 100% sealed. Draft through openings may lead to pressure differences. These differences in turn lead to thermal drafts responsible for temperature variations. Sealing the screen or experimenting with ventilation might reduce these.
Only after all known causes are addressed, can uneven climate be further improved with additional techniques. Those techniques include recirculation fans or equipment to draw in dry air from outside or from above the screen.
More information:
www.energiek2020.nu
adijkshoorn@ltoglaskracht.nl