ENGIE has noticed that onion companies are becoming more enthusiastic about condensation drying. “More and more people indicate this technique is the future,” says Marcel Bennink of Engie Refrigeration. The wetness during last year’s autumn reinforces this even more.
“No longer being dependent on the outside air is a major advantage. Drying can occur 24 hours per day, and climate can be better controlled. Fluctuations no longer influence the product, conditions are just controlled better,” Marcel says. He says reducing gas use could result in an advantage that’s at least as significant. Marcel mentions condensation drying could result in possible savings of 80 per cent on operational costs. “Gas is quite expensive. Moreover, moisture is released during the propane gas burning process, and it costs more gas to transport this. Whether condensation drying is actually quicker than drying with heaters is completely dependent on capacity and the user’s starting point.”
Becoming more sustainable
Which companies could benefit the most from this technique? “Regarding investment, a condensation drying system is more expensive than replacing each individual gas heater, but due to the higher quality and lower energy costs, the period to earn back the investment can be less than three years. For companies who want to store the onions longer and need refrigeration to do this, the installation is an extension, and the investment is therefore less considerable. For other traders and packing stations, for example, where batches of onions come and go throughout the day, there can be a considerable return on energy costs. If the aim is purely to replace the gas heaters, I can imagine this installation is too big. Companies that want higher quality and absolutely want to be able to dry, I would definitely recommend this technique. People can really be distinctive with it.” According to Marcel, becoming more sustainable is a reason for choosing condensation drying increasingly often. Companies want to stop using gas, particularly in the north of the country. “Energy is now often generated by the companies themselves, by means of solar panels, and they therefore also want to use this energy themselves. That is something that’s becoming increasingly important, and it can also be seen in house-construction. It could just be that buyers and/or supermarkets start demanding this in future.”
What is characteristic for ENGIE’s installation? “The condensation drying installation is a cold and hot installation in one, which makes open air and gas heaters unnecessary. We use natural coolants and a central system. When the onions are placed in a cell, much capacity is needed to remove moisture, but this quickly decreases after just one or two days. The central system can spread capacity across the various cells. Because of that, the total capacity of the installation is lower than with a decentralised system, which requires the maximum capacity to be installed for each individual cell. Besides, it’s possible to use residual heat from one cell to warm, for example, another batch. Moreover, our technique doesn’t have an additional medium, so that heat loss is limited.”
Total control and energy saving
Roger Custers, owner of Custers Akkerbouw, wanted more control of the atmospheric humidity in both the drying and the storage process. The traditional method of drying and storing onions was very expensive. “Besides, a quality onion requires a stable environmental temperature, and heating the air doesn’t contribute to that. Due to fluctuating outdoor air conditions, the onion fits its skin less well, and quality drops.” The new warehouse has three storage cells, each capable of storing 1,000 tonnes of onions. The new condensation drying system is a heat pump installation that Roger uses to dry the onions after harvesting, to heat and to store cold.
“With the condensation drying system, I have the control I wanted. No matter the condition the onions are in after harvesting, a day after grubbing up the onions start drying, and after just a few days, the neck is dry. The drying process is two times faster than in the past, regardless of the weather outside. I can also continue drying the onions during the storage process when product temperature is low.
With the conventional system, I had to keep the cells at high temperatures unnecessarily to be able to dry the onions using outdoor air, which isn’t beneficial to shelf life. Thanks to the new installation I can continuously supply good-quality onions.” An added advantage is that using propane gas is now a thing of the past. The farmer now only uses energy he personally generated with solar panels. Residual heat from the installation is regained for use in the office and the machine shop. If the open air is of good quality, the condensation drying installation uses this to dry even faster.
More information:
Engie
Marcel Bennink