Using vertical fans to aid in energy

The transition from SON-T to LED lighting provides significant savings on energy costs for many horticultural companies, but also leads to new challenges. After all, the climate in the greenhouse changes under full LED, as is the case at Rose Nursery Marjoland. A Luxous 1147 FR energy screen, vertical fans from ClimaFlow and an extra growth tube at the top of the greenhouse are used to better manage the radiation, moisture balance and heat distribution.

Marjoland mainly grows Red Naomi and nine other cut rose cultivars (total 20 ha) in Waddinxveen and is considered one of the best rose growers in the Netherlands. The switch from SON-T to LED lighting started twelve years ago and is expected to be completed next year. "We are now fully in that transition process. Now that we have been working with full LED for a few years, we see that the product quality is increasing, compared to SON-T. Twelve years ago we started with LED as interlighting. In 2018 we started linearly on 1 ha, from 2020 we started investing heavily in LED. We have now replaced 75% of the SON-T lamps with dimmable LED. This switch to full LED means a different greenhouse climate. Hence our investments in insulation and dehumidification", says Daniel van den Nouweland, General Manager.

Insulate the greenhouse
Energy saving is one of Marjoland's major challenges, says the director. "It is now becoming increasingly clear that electric is becoming more interesting than gas. We will be able to use the CHP engine less and less in the coming ten years. It will still be interesting until 2035, but with fewer and fewer operating hours. That is why we are also looking at how we can gradually move to 100% full-LED. The first step is to insulate with screens, so that we can save even more energy. In addition, labor is a challenge for us, the biggest one I think." Marjoland-4, a 6.8 ha section, will switch to full LED before the end of this year. The energy screen has just been installed. Cultivation Manager, Erwin van Adrichem: "Until then, we only had a light emission and sun protection cloth. Because we want to miss as little light as possible, we chose the Luxous 1147 FR. The light transmission is very important to us."

Measure screen performance
According to Svensson Climate Consultant Bart Bakker, the Luxous 1147 FR is the brightest energy screen currently available. The 11 stands for 11% light loss, the 47 for the energy savings percentage. But are these figures actually correct? "About 65% of the light in the Netherlands is diffuse, especially in winter. I think that is why you should always look at a screen cloth under diffuse conditions, that is also the moment that you close the energy screen in the nursery. A light loss of 11% actually never occurs, because that is measured perpendicularly. The sun is never perpendicular to a screen in the Netherlands. If we measure according to NEN standard 2675:2018, the light loss is 18%, because we include the reflection in that and you lose that reflected light. With diffuse light, the light loss is 25%. That is the honest story. This is natural light, which is free. You want to get as much of it as possible. "I think that's why you should always choose the brightest screen."

Using outdoor light
Van Adrichem confirms the importance of natural light: "We have between 300 and 360 µmol/m2.s hanging here. We illuminate all year round to guarantee a constant quality, so also in the summer. Our LED luminaires contain red, blue, far-red and green to create white. I think we are on the right side with that, but a SON-T lamp looks more like the sun than an LED lamp. So we find that bit of outdoor light very important. If the sun shines for half an hour today, everything just opens, so to speak. At the back of Marjoland-3 (4.8 ha) we have had this screen for a year now. Not only for energy saving, but also for the climate."

Energy saving and climate
Humidity becomes more difficult under LED, the Cultivation Manager continues. For that reason, Marjoland has brought a tube up under full LED, for better heat distribution. The company was also one of the first to start using vertical ventilation. "With the radiant heat, you can more easily remove moisture. We actually didn't want that extra heat near our roots, but rather above under the trellis. We mainly purchased the ClimaFlow system for a more even climate. They are very long paths, 125 meters left and right, in a relatively low greenhouse with a gutter height of 4.5 meters. Then you quickly notice that you get climate differences. Thanks to the ClimaFlow system, we also dared to exchange a sun-resistant cloth for an energy cloth. I wouldn't dare do that without the possibility of dehumidifying or ventilating."

The ClimaFlow system makes gaps a thing of the past, because you can close them 100% more frequently, says Van den Nouweland. "A more even greenhouse climate is the most important advantage and indirectly, we also get the energy savings." Van Adrichem: "We no longer leave gaps when the outside temperature is below 16 degrees. In some periods we go to 19 degrees. You are now simply the boss of your climate."

Replacement of minimum tube
According to Dominique Blok, Account Manager of ClimaFlow, their fan has become the replacement for the minimum tube. "The energy you put in with a minimum tube is one-off. Then you have to ventilate, because you want that vertical air movement. We provide a nice active climate in the form of a light breeze that goes through the crop." According to Van den Nouweland, there is potential in vertical ventilation: "There is still some unfamiliarity around air movement, yes. We see positive developments in that, also in the area of ​​product. If we leave a gap, you have a difference of 5 to 6 degrees in certain angles. If the screen is closed, I think the difference is within 1 degree. With those VentilationJets you distribute the fresh, dry air nicely and evenly over the greenhouse." Cultivation Manager, Van Adrichem agrees: "The more equal your climate, the more you can grow."

New pull wire
Hanging the fans in the 4.5-meter-high greenhouse was a close call. Dave Boer, commercial director of installer Huisman: "The energy screen had to be placed underneath in terms of installation space, there was no other way. It was a challenge to make it fit. The fans had to be integrated into it. There were also crops in the department. No damage may occur to the crop and the people themselves must also be able to continue working. We use special assembly trolleys for this. We have also developed a new type of pull wire that can handle ten times more screen movements. With modern screens, much more movement is done. Being able to slit precisely is still important, but with these fans you have the luxury of having to do that much less often."