In November 2013 the first trial period started in tomato greenhouse Fresh Valley in Maasbree, as a part of High Tech Greenhouse 2020. The goal: saving energy in existing greenhouses. In the greenhouse an innovative technique is being used that combines two types of climate screens with vertical ventilation and dehumidification. The initial results are known; from January to May 2014 20% of energy is saved compared to the reference greenhouse.
The new development that is being tested in Fresh Valley is the Ventilation Jet. This system exists of two fans one above the other that transport the dry, cold air from the top of the greenhouse through a hole in the climate screens into the space where the tomato plants are located. The inlet fan is located above the screen, the divide fan hangs underneath and distributes the fresh air horizontally and vertically through the greenhouse area to prevent too much cold locally. In the cultivation area the cold mixes with the warmer air. Because cold air is drier than moist air, it ‘displaces’ the moisture from the greenhouse. Dehumidification of the greenhouse is required to reduce the risk of fungi such as Botrytis. Thanks to the vertical ventilation also the heat from the assimilation lamps moves towards the tomatoes, so additional heating is hardly necessary.
More return at high greenhouse "We are talking about tomato cultivation with ongoing exposure to light," says consultant Ton Habraken. "Which is bound to strict environmental regulations. At night no light is allowed to be visible outside, therefore we use a climate screen that prevents any light emission. The Obscura ensures total blackout. But during the day you don’t want any loss of light, so it was important to install a second screen. The Luxous is a transparent, insulating fabric with a maximum natural light transmission. "In the test greenhouse both screens are installed on the same wire bed. According to Marcel Raaphorst, researcher at Wageningen UR Greenhouse Horticulture, that’s quite exceptional: "It is being done in Fresh Valley, because this test location is relatively low. At a higher greenhouse the screens will be installed on two wires beds. The expectation is that the return will be even higher.” The benefits of the Ventilation Jet are the low investment costs, low energy consumption and applicability in existing greenhouses.
Good for the environment and your wallet The first results are known; from January to May 2014 with the Ventilation Jet system 20% of energy is saved compared to the reference greenhouse. Most energy was saved during the night, while the assimilation lights were on and the screen closed. The highest benefit was achieved in the cold months, in February 33% of energy savings. Within a few weeks, a new tomato cultivation period starts. The trial period, in which Svensson participates, runs until March 2015.
The research program High Tech Greenhouse 2020, co-funded by the Interreg IV program of the European Fund for Regional Development, was launched at the end of 2012. It concerns a collaboration of eighteen companies and knowledge institutions to test new innovations with the aim to save water, energy and fertilizers. The Ventilation Jet is a joint development of the project partners Hint Installation, Vostermans Ventilation, Svensson, WUR Greenhouse Horticulture and Hoogendoorn Growth Management.