Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    We will mail you new results for this query: keywords==Dehumidification
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Climatisation of a closed greenhouse in the Middle East
Campen, J.B. ; Zwart, H.F. De; Hammadi, M. Al; Shrouf, A. Al; Dawoud, M. - \ 2018
Acta Horticulturae 1227 (2018). - ISSN 0567-7572 - p. 53 - 59.
Condensation - Cooling - Dehumidification - Energy use

Cooling is an essential part of greenhouse climate control in warm climates. There are three types of cooling technique: natural ventilation, evaporative cooling and mechanical cooling. Natural ventilation can only be applied when the outside temperature does not exceed 35°C and the average daily temperature is not higher than 22°C. Above these temperatures, production will be negatively affected. Evaporative cooling can be applied when the dew-point temperature of the outside air is less than these limits. These methods of cooling work effectively in arid regions, though the water consumption is high. The third method of cooling demands a cold surface to remove the latent and sensible heat from the greenhouse. This method has been applied in the current research. This method allows optimal control of the greenhouse climate in terms of temperature and humidity, but also in terms of carbon dioxide concentration. The amount of cooling capacity required depends on the amount of solar radiation being absorbed in the greenhouse and the convective heat transfer from outside, provided the outside temperature is higher than the greenhouse air temperature. The experiment showed that roughly 50% of the solar radiation has to be cooled from the greenhouse in order to maintain its temperature. Sixty per cent of the heat being absorbed in the greenhouse is transformed into latent heat through the transpiration of the crop. The system was able to maintain the preset temperature and humidity for the greenhouse air.

The ventilationjet system as a step towards controlled ventilation and adapted properties of insulation screens in greenhouses
Weel, P.A. Van - \ 2017
In: International Symposium on New Technologies and Management for Greenhouses - GreenSys2015 International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611665 - p. 167 - 174.
Dehumidification - Energy saving - Transpiration control - Ventilationjet
Moisture control in a greenhouse based on the creation of screen gaps has many disadvantages. This study describes a new approach where screen gaps are avoided by installing a Ventilationjet system. A speed controlled fan creates an airflow through a small opening in the fully closed screens. A second fan under the screen mixes the cold, dry air with greenhouse air. This system is controlled based on the difference in absolute humidity of the air under and above the screen. This difference, multiplied by the volume of air that is exchanged equals the amount of transpiration produced by the plants. This system was tested in multiple crops including gerbera and roses. This resulted in a 16-23% lower gas consumption in a situation where the screen system was not changed. The reduction was a result of more controlled ventilation and the reduction of horizontal and vertical temperature differences within the greenhouse. Based on these positive results, the development of new screen systems that can be combined with the Ventilationjet system has started. A first test with a cucumber crop resulted in a 63% reduction of energy consumption compared to a standard greenhouse with a single energy screen.
The development of the EXE-kas
Bronchart, F. ; Demeyer, P. ; Linden, P. van der; Paepe, M. De; Vis, R. De; Wittemans, L. ; Weel, P.A. Van; Cheret, E. ; Malschaert, P. ; Tassens, S. - \ 2017
In: International Symposium on New Technologies and Management for Greenhouses - GreenSys2015 International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611665 - p. 453 - 460.
Dehumidification - Greenhouse - Primary energy saving - Screens - Vapour heat pump
Different primary energy saving techniques for greenhouses have been tested in the past. Those systems were designed by using the first law. However, no attention was paid to the exergy destruction in the processes (second law). This exergy destruction is related to the driving potential of the processes and the mass/energy transfer quantity, and it determines the efficiency of the system. In this paper, different energy saving techniques for greenhouses are studied based on exergy analyses at the process level. Many of the studied techniques could be labelled as "less promising". Based on this assessment, our research team select an efficient dehumidification device (vapour heat pump) and EB (Energy Balancing)-screens as most promising. A greenhouse equipped with those techniques is named "EXE-kas" (Exergy Efficient greenhouse). The prospected dehumidification efficiency of an optimal designed vapour heat pump is around 10. The use of the EB-screens results in a near neutral energy balance of the greenhouse without heating.
Potential of different energy saving strategies in heated greenhouse
Gilli, Celine ; Kempkes, F. ; Munoz, P. ; Montero, J.I. ; Giuffrida, F. ; Baptista, F.J. ; Stepowska, Agnieszka ; Stanghellini, C. - \ 2017
Acta Horticulturae 1164 (2017). - ISSN 0567-7572 - p. 467 - 474.
Dehumidification - Energy efficiency - Screen - Temperature integration - Tomato
In heated greenhouses, large amounts of energy are used to optimize climate conditions (temperature, humidity). In conventional tomatoes production, the estimated annual energy consumption is 320 kWh m-2 in France, with large differences across regions, 400 kWh m-2 in Brittany and 240 kWh m-2 in the South (ADEME, 2007). In Switzerland, it varies between 245 and 500 kWh m-2 according to the regions. With increasing energy prices and environmental concerns, growers have to find solutions to reduce their energy use and to improve the energy efficiency. Several axes could be used to achieve this goals, one of them is climate management. Within the working group "Energy saving and neutral production" of the Cost Action FA 1105 "BioGreenhouse", a review on the potential for energy saving in heated greenhouse thanks to climate management was done. Basically, there are two ways to reduce energy consumption: related to temperature control and to humidity control. The energy saving potential of lowered day and night temperature set points, temperature integration (TI) and screen management will be presented in relation to the effects on production. In Switzerland, three trials from 2006 to 2008 in tomato crops showed that an energy saving potential of 15 to 30% could be achieved with TI compared to the standard temperature treatment. An energy saving between 23 and 30% with screens management based on external temperature and light intensity compared to a management according to the sunrise was obtained. To reduce energy consumption related to humidity control, dehumidification with heat recovery was studied. A traditional dehumidification (ventilation and heating) was compared with dehumidification with a heat pump in tomatoes crop. In 2013, 15% energy saving was achieved with the dehumidifier and in 2014 reached 25%. No difference in plant growth, yield and fruit quality was measured.
Plant factories; crop transpiration and energy balance
Graamans, Luuk ; Dobbelsteen, Andy van den; Meinen, Esther ; Stanghellini, Cecilia - \ 2017
Agricultural Systems 153 (2017). - ISSN 0308-521X - p. 138 - 147.
Artificial lighting - Dehumidification - Lettuce - Penman-Monteith - Urban agriculture - Vertical farm
Population growth and rapid urbanisation may result in a shortage of food supplies for cities in the foreseeable future. Research on closed plant production systems, such as plant factories, has attempted to offer perspectives for robust (urban) agricultural systems. Insight into the explicit role of plant processes in the total energy balance of these production systems is required to determine their potential. We describe a crop transpiration model that is able to determine the relation between sensible and latent heat exchange, as well as the corresponding vapour flux for the production of lettuce in closed systems. Subsequently, this model is validated for the effect of photosynthetic photon flux, cultivation area cover and air humidity on lettuce transpiration, using literature research and experiments. Results demonstrate that the transpiration rate was accurately simulated for the aforementioned effects. Thereafter we quantify and discuss the energy productivity of a standardised plant factory and illustrate the importance of transpiration as a design parameter for climatisation. Our model can provide a greater insight into the energetic expenditure and performance of closed systems. Consequently, it can provide a starting point for determining the viability and optimisation of plant factories.
Contribution of innovative technologies to new developments in horticulture
Pekkeriet, Erik ; Henten, E.J. Van; Campen, J.B. - \ 2015
In: Acta Horticulturae International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462610965 - p. 45 - 54.
Automation - Dehumidification - Energy solutions - Greenhouse - Greenhouse cover materials - Mechanization - Robotics - Sensors

This paper reviews new developments in high-tech greenhouse horticulture. It will focus on sensors, energy solutions, covering materials, production technology and robotics. Driving forces for new technologies are identified and Dutch greenhouse crop production is used as an example. Sensors are introduced in horticulture using the latest techniques from medical and industrial research. A 3D volumetric intersection technique is used to sort tomato seedlings at a speed of 40.000 pieces per hour and measures the full 3D geometric features, which is clearly an impossible challenge when done manually. Other 3D techniques like stereo vision, time of flight and laser triangulation are introduced in greenhouse horticulture to control robots, measure the geometric quality features as flower diameter and bulb orientation or to separate target features from its agricultural surroundings (e.g., Anthurium, chicory, lily bulbs). But also the interest to measure internal quality features as ripeness, food compounds, internal defects and the ability of photosynthesis capacity can be measured by spectral cameras, fluorescence techniques and X-ray. First applications in research and production are being introduced (e.g., rose, Alstroemeria, tulip, tomato or cucumber). To apply integrated management on pests and diseases in the greenhouse, sensors are needed to determine pests and diseases and its magnitude automatically at an early stage (e.g., long horn beetle, botrytis, sticky plates). More future sensor applications are expected in this field. New developments in energy solutions in greenhouses will lead to more profitable options in crop production. Energy saving in horticulture has been the subject of research for more than 20 years in a special program "greenhouse as energy source" financed by the Dutch ministry of agriculture and growers. The result is that Horticultural industry in The Netherlands consumes now 50% less energy compared to 1990 due to all energy saving measures. Various technologies developed are now common practice in greenhouses like the application of thermal screens and temperature integration. More recent developments in humidity control have been adopted further decreasing energy consumption and thereby even increasing production quality and quantity. Alternative energy sources like geothermal heat are being used by some growers allowing fossil-fuel free vegetable production. More futuristic concepts where electricity and heat are produced in combination with greenhouse production are still in the experimental phase. When all new developments lead to products with excellent quality in the right amount, price and ready just in time, products need to be harvested with a predictable capacity and reliability. Progress is made on robotic harvesting of fruits, flowers and vegetables. First robots that are tested in practice on a 24/7 base (cutrose, strawberry, kiwi) have shown to be very close to market introduction. Progress is made and big efforts by several consortia are put in actual developments to harvest tomato leaves, cucumbers and sweet peppers. Self-learning algorithms, open source robotic software and generic mechatronic solutions are available and adaptive to new tasks and products and will enable fast future robot solutions after first successful introductions.

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