Condensation drying is a much applied and widespread principle of air treatment, and has, among other uses, commercial applications such as the construction dryer and the condensation dryer at home. Although much is still unknown, more and more onion companies are now seeing the added value of this technology.
With a condensation drying installation, product can be dried at all times, independently of the condition of the open air. “The drying process can be started immediately after storing, even in a wet autumn. This, independent of the open air, is the most important advantage of this technique,” says Robert Glerum of Glerum Koeltechniek. “Besides, condensation drying uses electrical energy. Gas is therefore no longer needed, and no external CO2 is added to the space. To say it bluntly, gas heaters heat the open air, and a large part of the added energy is then removed via outlet valves.” During the condensation drying, these valves are closed, so that less energy is lost during the drying process. According to Robert, it offers users additional advantages besides no longer needing a gas supplier. For example, the system can also be used to just cool or heat the cell, without a risk of fire.
In the process of condensation drying onions with closed valves, the technique works as follows: The relatively warm air from the onions is sucked out by the evaporator vents. When the air comes into contact with the cold evaporator-slats, the air cools down. This cooled air contains less moisture, and, as a result, condensation of the moisture in the air occurs on the evaporator-slats. This water is removed via the condensation water drain. The air leaving the evaporator therefore has a lower temperature and a higher atmospheric humidity. When this cooled air is once again reheated to its original temperature, the air has a lower atmospheric humidity than when it’s introduced by the evaporator. After all, the condensed moisture is removed from the air flow. When the dried air is reintroduced to the onions, the air, due to its lower atmospheric humidity, is better able to extract moisture from the onions. This process doesn’t depend on the temperature in the cells. Drying can therefore occur at 20 or 30 degrees Celsius, although drying can also occur at 10 degrees Celsius. To realise drying at 30 degrees, the system assumes a central outdoor source installed near the cooling centre. Because of this, the space can quickly achieve this temperature to combat neck rot.
Full circle
What is characteristic of the installation of Glerum Koeltechniek? “We use central systems, so that one central condensation drying installation can provide both cooling, drying and heating for multiple storage cells.” This has an important advantage, price-wise, compared to systems that use one condensation drying installation per cell. Furthermore, the system can be installed in existing sheds with no constructive adjustments to the building. Additionally, Glerum Koeltechniek can provide a complete package, including controlling the valves and the support ventilation. This is necessary as well, because the valves have to closely work in conjunction with the condensation drying installation: “The installation will always first compare the current outdoor conditions with the desired indoor conditions.” The functions of the installation combining cooling, heating and condensation drying therefore only become active when necessary, if the outdoor air is not suitable for this.
Last year, Glerum Koeltechniek placed a similar installation for the Geduho company in Oud-Beijerland, the Netherlands. “The goal was to install a combination for potato and onion storage, using this new drying principle based on a central installation. Cooling the potatoes and drying the onions at the same time using the same cooling and condensation drying installation operates incredibly well and saves energy. If you also generate your own power using solar panels, you’ll have come full circle,” the satisfied farmer tells us via twitter.
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Glerum Koeltechniek
Robert Glerum