"The same effect typically achieved with pipe heating has been accomplished through air movement instead," notes Ary de Jong of HortiTech, as he updates a select group of stakeholders on a trial using Caeli's fan system in tomato cultivation.
Ary managed to have tomatoes on the plant in the demo greenhouse at Proof, Netherlands, after a difficult, dark period in early February. Remarkably, unlike many commercial growers, there were no signs of mold in the greenhouse by mid-April—despite operating at the edge of feasibility with high relative humidity and low heating temperatures."
In the trial cultivation, the experienced grower from HortiTech deliberately chose a challenging approach. Planting began on December 1st—one week earlier than commercial Dutch growers, who are already considered early. This demanding strategy was designed to thoroughly test the effectiveness of the horizontal fan system. While maximizing tomato yields is not the main objective, the crop is expected to match average production levels, but with significantly lower energy consumption.
View in the greenhouse.The vertical fans are off. In this greenhouse, 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—practical experience has already been gained on a larger scale in strawberry cultivation. While climate homogenization proved effective in that context, the setup was not ideal for thoroughly testing the system's full potential for dehumidification. The current trial at the Proof demo center aims to demonstrate the fan system's performance under more demanding conditions in a tall crop, while also giving market stakeholders a firsthand look at the technology and its practical application.
Unlike conventional vertical fans, this system is integrated into the greenhouse columns. It enables air to be drawn from above a closed screen without interfering with the screen installation. The system also features proportionally adjustable ventilation and flap settings, allowing flexible air intake from below and/or above the screen as needed.
The Caeli™ fans are designed to optimize greenhouse climate homogenization and dehumidification in line with energy-efficient cultivation practices, such as Het Nieuwe Telen (Next Generation Growing). Sensors continuously monitor temperature and humidity levels both above and below the screen. Every 10 minutes, an algorithm calculates the optimal position of the fan's adjustable vents and determines the required ventilation power for each unit. The Blockbax Cloud platform visualizes climate differences through graphs and heatmaps, and its integration with the climate computer ensures easy and efficient operation
Ary de Jong of HortiTech and Sven van Heijningen of Caeli/Alcomij
Uniform climate thanks to air movement
In the trial setup, ten fan units have been installed. These units can be daisy-chained for electrical power and communicate wirelessly. Equipped with sensors, Caeli's system gathers valuable data from multiple locations within the greenhouse. This enables the system to provide a much more accurate and comprehensive overview of the greenhouse climate compared to the traditional measuring box connected to a climate computer. The measuring box, often placed in a fixed location, is typically not positioned in the crop itself, limiting its ability to reflect the full climate variability.
Thanks to the strategic placement of the fan units, Caeli's system provides temperature and humidity data from the crop. Sven van Heijningen, R&D Manager at Alcomij, who oversees the innovative greenhouse climate solution, highlights a diagram that shows the cooler and warmer areas of the greenhouse in blue and red. Using these fan units, which are controlled by an algorithm, air movement can be initiated to create a more uniform climate throughout the greenhouse."
Caeli organized two sessions to come and see the trial. Here is the session from Tuesday morning, April 15th.
No mold problems
The trial at Proof has shown that air movement effectively enables the crop to evaporate even with high relative humidity. Currently, many growers still rely on pipe heating for this purpose. Over the course of the trial, the relative humidity in the demonstration cultivation was gradually increased from 85% to 93%. Ary used the pipe heating solely for preheating the greenhouse, not for generating air movement or dehumidification.
Recently, several growers have been following the trial closely. According to Ary, they were consistently surprised by how he managed to prevent mold issues while maintaining productivity. While the first truss struggled to develop during the dark period and the second truss failed, the third truss eventually appeared, despite initial doubts from visiting growers.
Even in mid-April, there are still no signs of mildew or Botrytis in the greenhouse, where three trusses have been harvested in the past ten days. The green waste was intentionally left on the ground to further challenge the system, though Ary acknowledges that staying mold-free is becoming increasingly difficult. Recently, ventilation was also introduced, while the Caeli units continued running in the greenhouse, which is controlled by a Priva climate computer. There is, however, a limit to how much dehumidification can be achieved through air movement alone.
By mid-April, the ongoing cultivation has achieved a 24% energy saving thanks to the Caeli system. Sven explains, 'We want to demonstrate what's possible here. Even if a commercial grower were to achieve just half of this energy saving with our system, it would still represent a significant gain."
The relatively small, lightweight fans last 70,000 operating hours.
For more information:
Caeli™
[email protected]
www.greenhouse-climate.nl
HortiTech
[email protected]
www.horti-tech.com