In 2012 tomato grower Dick van Noord started production in a new greenhouse. It was designed, built and equipped according to the principles of The Next Generation Growing. The advantages weren’t immediately apparent. Close examination of the crop using thermal imaging yielded results.
Dick van Noord (left) talks with Hugo Plaisier: “I would like to convert my old greenhouse for Next Generation Growing and save energy there as well. But circumstances make that currently impossible.”
In the Dutch province of Zeeland, Dick van Noord grows cocktail tomatoes on the vine, of variety Brisco, in two greenhouses. The first greenhouse is 3.7 ha. The second is 4.7 ha and was built in 2012. It was equipped according to the principles of the Next Generation Growing. The grower uses two transparent screens, polycarbonate panelling and has dehumidification units in the wall. The greenhouse is 7 meter high.
He decided on Next Generation Growing, with a particular view to saving energy. “Regardless of the latest prices, energy is a very large share of the cost price. If you can reduce the share of the energy costs that will always be beneficial in the long term.”
An extra button
The way of growing in the new greenhouse was a learning process, says the grower. “You do have an extra button to press, namely for dehumidification. In the old greenhouse I opened the screen to remove any excess moisture. Here in the new greenhouse when there’s an excess of moisture the dehumidification unit has to work harder.”
And dealing with light also requires a different way of thinking. “If there is too little light, for example on a very cloudy or rainy day, I used to have to leave the screen open in the old greenhouse. In the new greenhouse I can choose. I can even keep the screen closed on a dark day. Then I might lose light but I gain it back with the energy savings.”
The benefits of the Next Generation Growing in the new greenhouse weren’t immediately apparent. The horizontal heat distribution was good but vertically there was quite a large variation. There was a draught at the base of the crop; here the air felt much colder than higher up in the crop. “Something was not right,” says Van Noord. “I started to do some inquiring. Simply by trying different things I wanted to find a solution.”
The tomato grower set the temperature of the incoming air slightly higher than the temperature required in the greenhouse. That helped somewhat: the tomatoes were fine but the tops of the plants didn’t grow well. And the fruit still ripened slower than normally would be the case. The draught at the bottom of the crop hadn’t gone away.
Heat distribution revealed
Eventually Van Noord asked Arjan Vijverberg, tomato production advisor of DLV Plant, about it. Vijverberg decided to search for the cause using a thermal imaging camera. This measures the heat distribution in the greenhouse and the crop based on infrared radiation and it can also detect any leaks in the insulation.
The camera’s images showed the unevenness of the vertical temperature distribution in the crop. The leaves at the top were warmer than the stems and fruit lower down. The stems were colder than the leaves in the upper layer of air and warmer than the fruits. The fruits were the coldest.
Sharply in focus
Van Noord then managed to achieve the desired climate by blowing out warmer air through the hoses at the bottom, with a temperature 1.5ºC higher, and by using the growth rails more. This ensured that all plant parts received the desired and necessary heat, even the tops of the crop.
The thermal imaging camera illustrated this very clearly, says Arjan Vijverberg, who advised the grower about the Next Generation Growing in the new greenhouse. “A plant constantly adjusts to its environment. The infrared images produced by the camera show much better what happens than measurements with sensors. The images clearly show the difference in temperature. It was easy to see that the fruits remained colder. This caused the slow ripening.” DLV Plant uses its camera mostly for its own research. Vijverberg: “Sometimes we take it with us to customers so that we can visualise the heat distribution and can detect any leaks.”
Paying back the investment
Van Noord is satisfied with the solution they’ve found. “If you decide to go for Next Generation Growing you have to aim for a reduction in gas consumption of nine cubic metres per metre per year. Of course, you’ll want to retrieve the investment that’s required.”
Essential in his new greenhouse is the double movable Luxous 1347 FR screen. It is completely transparent and according to the grower and Hugo Plaisier, of the supplier Svensson, it is very compact and easy to fold into a package. Then it intercepts very little light. “Having two screens creates more possibilities to play with the light and climate than a single screen. The screen is not diffuse so I get a lot of light early in the morning and evening when the sun is at a low position,” says the grower. “Light transmission is maximal and that of course is very interesting,” adds Plaisier.
Simple conversion to NGG
The tomato grower would like to see a relatively simple way of converting his old greenhouse and making it suitable for Next Generation Growing. “The banks aren’t providing any credit lines at the moment as there is still a lot of uncertainty in the market. However, we still have to continue to innovate. Therefore I look forward to the possibility of being able to convert my old greenhouse for a competitive price for Next Generation Growing. The energy savings would make that attractive.”