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‘Uniform climate with active dehumidification'

Some businesses still work with a minimum tube of 40 degrees, or a screen gap for humidity of 5% or more, Ton Habraken, Greenhouse Climate Expert at Svensson, concludes. “Not necessary, and definitely not when combined with our ClimaFlow System, which works much more effectively and more affordably. Also be careful with dehumidification boxes that are placed inside the growing area; these run the risk of over-stimulating the plants and ultimately, using much more energy than necessary.”

A ‘growing tube’ of 40 or 45 degrees really should be a thing of the past by now, but the reality is that Habraken still regularly comes across them. Although with the current energy prices, it is becoming less and less common. “To generate air movement among the crop, growers are now often using a minimum tube of 30 degrees, which will easily consume as much as 25 W/m2/hour. A minimum tube of 40 degrees would quickly double that consumption, say 40-50 W/m2/hour. That is a significant energy input, when you really don’t need that energy in that moment to maintain the temperature level in the greenhouse. It is intended solely to generate air movement through the crop, which you could achieve just as well with
a vertical ventilator that will only consume 1 W/m2/hour.”

Air movement…

On June 1st, 2022, Svensson acquired Hinova and all new sales are being made under the name ClimaFlow. The ClimaFlow System offers an effective and efficient way for improving the greenhouse climate, in particular when combined with a double energy screen. “Really it is about two independent systems: the bottom ClimaFlow Fan provides good air movement throughout the crop - a gentle ‘breeze’ that helps improve the microclimate by removing the produced moisture and keeping the crop active. Then there is the VentilationJet, a white inflow unit through the screen pack, which allows you to suck in dryer air from above the screen if you want to reduce the humidity level of the greenhouse air. But the first step is really the most important: properly manage the air movement throughout your crop. In terms of energy input, it is much more efficient than a growing tube”.

More than ever, growers are investing in hybrid or full LED lighting and/or a double energy screen, with or without air dehumidification equipment. “These can be a great combination, although it doesn’t always require such expensive equipment. Firstly, make sure you have air movement in and through the crop, which is more important than having active air dehumidification. Especially due to dehumidifying in the wrong way, or dehumidifying too early with this equipment, you can end up using more energy than necessary. Because you have the equipment, there is a tendency to use it more often and at earlier stages. You run the risk of overdoing it, causing you to over-activate the plant, which will cost a lot more energy than what is necessary.” Those who move to hybrid or full LED lighting, find themselves dealing with a different climate, causing less radiation heat to reach the plants. “This makes convection transference of heat from properly managed air movement that much more important. In static air, you don’t get any of that and so you must ensure that you have got your air movement properly managed in order to keep the plant active and guide its growth.” 

Growing with a greater focus on humidity

Another advantage of the ClimaFlow System is that it essentially makes screen gapping obsolete. The system has been tried, tested and proven in countless fruit vegetable crops such as tomatoes, cucumbers, eggplants and bell peppers, but also with strawberries, kalanchoe and gerbera…
Habraken: “The relatively simple system has already been successfully applied to many different crops. By now, it really is a proven technique for keeping the greenhouse climate even and keeping the crop active. This also allows you to grow with a greater focus on humidity, without it causing issues in the crop. The system is also relatively easy to install and apply in existing greenhouses

Stop screen gapping

A minimum tube can still serve a purpose, but do not make it unnecessarily high, Habraken says: “A delta T of 12 degrees in relation to the desired greenhouse temperature suffices. If you want your greenhouse temperature at 16 degrees, then a tube of 28 degrees suffices to generate air movement.” His final piece of advice: stop opening gaps in the climate screen. “Gapping causes an uneven greenhouse climate. Therefore, you should try to dispose of as much humidity as possible through the screen, by focusing on the difference in Absolute Humidity (AH) between the growing space and the area above the screen, and by venting in two directions above the completely closed screen. With help from a measuring box above the screen, with temperature and RH measurement, you also gain insight into what is happening above the screen in terms of temperature and AH. That can be very helpful for disposing of excess humidity. But also for opening your screen the right way in the morning, so that you don’t cause rapid temperature drops. Also, don’t forget to properly check over your measuring boxes during crop rotation. Clean out the socks, replace the water time and ensure
that the measurements are calibrated. Maintenance of sensors is an often-neglected task - give this the proper level of attention, especially now.”

The Svensson Climate House advice team offers full support from start to end, from installation to implementation of the ClimaFlow System. This is done based on data analyses of the climate computer, so that the system can immediately ensure an optimal climate

For more information, please contact a Svensson Climate Expert or download our ClimaFlow brochure in the button below.

Published in Kas Magazine - 12 - 2022

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