"Optimal dehumidification based on air movement with special fan"

The same effect has been achieved with air movement as you would normally use pipe heating for. Ary de Jong of HortiTech makes this observation as a select group of interested parties gets updated on a trial with Caeli's fan system in a tomato cultivation.

Ary succeeded in having tomatoes on the plant in the greenhouse at demo center Proof after a difficult dark period in early February, in the Netherlands. Also noteworthy: unlike growers in practice, there are no issues with mold in the greenhouse by mid-April. This is despite pushing the limits with high RH and low heating temperatures.

In the trial cultivation, the experienced grower from HortiTech did not make it easy for himself. Deliberately. The decision was made to plant on December 1st, 1 week earlier than the practical grower, who is already early for a Dutch situation. By choosing this challenging cultivation strategy, the effect of the horizontal fan system can be well tested in the research. Maximizing tomato yields is not the goal of the trial. However, the tomato cultivation must keep up with an average tomato cultivation, but with significant energy savings.

© Thijmen Tiersma | MMJDaily.com
View in the greenhouse from the corridor. The vertical fans are off. In this cultivation, only the Caeli fans in the greenhouse columns are running, one can be seen at the red arrow.

Fan in greenhouse column
Caeli's system is not entirely new. In practice, experience has already been gained on a larger scale in strawberry cultivation. There, the climate homogenization went well, but the cultivation situation was not ideal for also testing the maximum effect on dehumidification in practice. The goal of the trial at Proof is to demonstrate the operation of the fan system in a challenging, tall cultivation and to introduce market parties to how the technical innovation works and looks.

Unlike the more familiar vertical fans, this system is integrated into the greenhouse column. The system allows air to be drawn from above a closed screen cloth without compromising the screen installation. The system features a proportionally adjustable ventilation and flap position, allowing air to be drawn from below and/or above the screen.

The Caeli™ fans are used to homogenize and dehumidify the greenhouse climate according to the principles of a more energy saving cultivation (Het Nieuwe Telen, Next Generation Growing). Sensors measure the temperature and humidity above and below the screen, after which an algorithm calculates the desired flap position and ventilation capacity of the individual units every 10 minutes. The Blockbax Cloud platform makes climate differences quickly visible through graphs and heatmaps, and thanks to the connection to the climate computer, it is easy to operate.

Uniform climate thanks to air movement
In the trial setup, ten fan units have been placed. The systems can be daisy-chained for electrical power and communicate wirelessly. Because the fan units are equipped with sensors, Caeli's system collects valuable data in multiple places in the greenhouse. This allows the system to provide a much better average picture of the greenhouse climate than the measuring box that comes with a climate computer can now. The measuring box often hangs in one place, and often not really between the crop.

Due to the placement of the fan units, Caeli's system does provide that data on temperature and humidity from the crop. Sven van Heijningen, the R&D manager at Alcomij responsible for the innovative greenhouse climate solution, points to a diagram showing in blue and red where the colder and warmer parts of the greenhouse are located. With the fan units, which are controlled by an algorithm, it is possible to initiate air movement for a uniform climate.

© Thijmen Tiersma | MMJDaily.com
Caeli organized two sessions to come and see the trial. Here is the session from Tuesday morning, April 15th.

No mold problems
The experiences in the trial at Proof show that air movement ensures that the crop can evaporate even with a high RH. Now growers often still use pipe heating for this. In steps, the RH in the demonstration cultivation has been increased from 85 to 93%. Ary only used the pipe to preheat the greenhouse, not to create air movement or dehumidify.

The trial has also been followed by several growers recently. According to Ary, they were consistently surprised at how he managed to prevent mold problems and still remain productive. The first truss came on with difficulty during the dark period, the second truss failed, but with great effort, the third truss, despite doubts from visiting growers, eventually did appear.

Even in mid-April, we still see no signs of mildew or Botrytis in the greenhouse where three trusses have been harvested in the last ten days. The green waste was deliberately left on the ground to further challenge the system, although Ary acknowledges that it is becoming increasingly difficult to remain free of molds. Recently, there has also been ventilation, while the Caeli units continued to run in the greenhouse, which operates on a Priva climate computer. There is indeed a limit to how much you can dehumidify with just air movement.

In the ongoing cultivation, there is an energy saving of 24% by mid-April thanks to the Caeli system. Sven: "We want to show what is possible here. Even if a practical grower were to achieve only half of this energy saving with our system, it would still be a significant gain."

HortiTech
ary@horti-tech.com
www.horti-tech.com