"More air handler units ordered than ever"

More and more greenhouse growers are tackling high energy prices with new or additional screen cloths. To keep the indoor climate optimal in this situation, they are also investing in advanced dehumidification and ventilation techniques.

At Technokas, they notice this through a strong growing demand for systems for 'Het Nieuwe Telen' (The New Cultivation). In recent months, more vegetable growers than ever ordered the air handlers that Technokas can install in the façade or deck. These units can draw in outside and inside air to blow this (mixed) air into the greenhouse in a controlled way via a fan, heating block, and air distribution hoses, Technokas reports.

After Technokas previously installed the air handling units at Schenkeveld's sizeable tomato company, near Schiphol Airport, in its two newest greenhouses totaling 20 hectares, demand is now also coming in from other vegetable growers. These installations can achieve positive results in tomatoes, aubergines, and peppers.

The most recent projects have been carried out at Van Duijn De Jong Aubergines in Oosterland, on Schouwen-Duiveland, and at D.T. van Noord's tomato nursery in Sirjansland, almost a neighbor of Van Duijn De Jong. Pepper grower Overgaag has also ordered the system with AHUs for their new greenhouse to be built in Maasland. They can have this technology at their disposal next year.

"Growing becomes much easier"
At Van Duijn De Jong Aubergines in Oosterland, farm manager Gerard van Vossen is very enthusiastic and pleasantly surprised by the positive results. "By nature, I am quite hesitant about these kinds of new techniques and promises. We also went to see Schenkeveld, but even then, I had some reservations about the results we could achieve with it and the investment we had to make," agrees Van Vossen. "But the system has now been working since December when we started the new crop, and I am, perhaps a little against my nature, wildly enthusiastic."

"Growing really is getting so much easier. I have suddenly gained a lot of tools. I can work with tight lines. Controlling for moisture or temperature is fully automatic. I can activate the crop properly in the morning, even in dark weather. Because we have another greenhouse where we don't have this system yet, but where we do have a fixed and movable screen, we can make good comparisons. Growing has really become a top-class sport. With the air handling units and trunks, performing is a lot easier and with better results. Compared to the greenhouse without this system, we have saved about 20% of energy here. That's above expectations."

Improving performance further
Van Vossen expects it to get even easier in the coming year and to potentially improve performance. "In the beginning, you're hesitant to get everything out of it. I had to gain confidence in the system, but it really works well. I even dare to keep the screen closed all day on dark days. The only reason we had to heat more than was really necessary is because we do not yet have an alternative solution for the CO2." To install the system in the 27,500 m2 greenhouse, with a gutter height of 6.6 metres, Technokas installed the air handling units (AHUs) above the path in the deck.

The concrete path runs along the end wall. Van Duijn De Jong Aubergines plans to extend this greenhouse at the end wall in the future, after which this path will become a middle path. Eight AHUs are currently installed, with air intake through the deck.

These AHUs are already directly suitable for a future extension on the other side, but for now they are only equipped with fans, mixing valves, mixing chamber, and heating blocks on one side. These facilities can later also be incorporated on the other side. The air distribution hoses on the side now in use are about 125 meters long. So there is now one AHU for every three 8-meter rail, i.e., every 24 meters. This gives the AHU a coverage of 3,000 m², with a capacity of 15,500 m³/h, which equates to about 5 m³/hr/m².

AHUs in the end walls
Neighboring D.T. van Noord's greenhouse is over 3.5 hectares, with a gutter height of 5.5 metres. In another greenhouse, where Van Noord already dehumidifies, the tomato grower uses a different system with trunks under the crop. But for this large greenhouse in Sirjansland, Van Noord chose Technokas' system with air treatment units on two sides in the end walls and, therefore, hoses above the crop. Technokas installed a total of 13 AHUs, 6 on the short side and 7 on the long side.

All AHUs are equipped with internal and external dampers, a mixing chamber, a heating block, and a fan. The air distribution hoses are about 83 and 90 meters long each. With one air handling unit per four 8-meter rails, i.e., every 32 meters, the capacity here, too, comes to about 5 m³/h/m².

Relatively few adjustments
"To install these air handling units, we had to modify the façade slightly," explains Freek Batist of Technokas. "But the adjustments generally remain very limited. The installers adjusted the façade screen installations slightly, connected the heating blocks of our AHUs, and provided the electrical connections and computer controls. So we were able to deliver the installation in a short time in early 2023, after which Van Noord was able to start using the benefits immediately."

First installation for pepper cultivation
Another nursery that will start using the system next year is Kwekerij Overgaag. These pepper growers will realize a greenhouse expansion of over 4 hectares at their Maasland site. At this nursery, Technokas will start installing six AHUs above the middle aisle in September, with air intake through the deck. "These AHUs do immediately blow out to two sides, so in fact, they are 12 units, each equipped with inner and outer valves, a mixing chamber, a heating block, a fan, and air distribution hoses approximately 92 meters long."

"These units have a capacity or flow rate of 15,250 m³/h, equivalent to about 4.6 m³/hr/m². This is deliberately slightly lower than for tomatoes or aubergines," says Batist, "but that's because the 'drier' cultivation of sweet pepper has slightly different requirements. So Technokas will always, in consultation with the growers and their cultivation requirements, design, and engineer the AHUs entirely to size."

For ornamental and vegetable cultivation
In previous years, it was mainly growers of ornamental crops, such as orchids, roses, chrysanthemums, and a few other crops, for whom AHU systems were popular. "Those growers also still come to us for this technology. For example, this year, we installed 12 AHUs in the facade of an existing greenhouse in Naaldwijk for KP Holland to grow Curcuma. Kwekerij Apartus also has advanced plans to have 12 AHUs installed in the façade of their Cyclamen greenhouse in Poeldijk. But now vegetable growers are also discovering the advantages of dehumidifying, ventilating, and heating with AHUs in their search for new ways to save energy, and especially for tools to better control the indoor climate.

For example, Technokas will soon install two AHUs in the façade at Arjan Bassie's Nursery, which manages Syngenta's tomato test greenhouse in Maasland. Besides the entrepreneurs mentioned, other growers have submitted applications. Some will make a decision soon, and others will apply for subsidies first and make the decision as soon as they receive subsidies. "Especially with the current energy rates, installing AHUs is already very interesting for many growers even without a subsidy, precisely because, in addition to the savings, it provides a better uniform indoor climate," concludes Batist.

For more information:
Leehove 33
2678 MA De Lier
Tel.: +31 (0)174 24 05 45

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