Venlo Greenhouse Research Articles

Distribution Characteristics and Prediction of Temperature and Relative Humidity in a South China Greenhouse

South China has a climate characteristic of high temperature and high humidity, and the temperature and relative humidity inside a Venlo greenhouse are higher than those in the atmosphere. This paper studied the effect of ventilation conditions on the spatial and temporal distribution of temperature and relative humidity in a Venlo greenhouse. Two ventilation conditions, with and without a fan-pad system, were studied. A GA + BP neural network was applied to predict the temperature and relative humidity in fan-pad ventilation in the greenhouse. The results show that the temperature in the Venlo greenhouse ranged from 15.8 °C to 48.5 °C, and the relative humidity ranged from 24.9% to 100% during the tomato-planting cycle. The percentage of days when the temperature exceeded 35 °C was 67.3%, and the percentage of days when the average relative humidity exceeded 70% was 83.7%. The maximum temperature differences between the three heights under NV (Natural Ventilation) and FPV (Fan-pad Ventilation) conditions were 3.4 °C and 4.5 °C, respectively. The maximum relative humidity differences between the three heights under NV and FPV conditions were 8.4% and 21.7%, respectively. The maximum temperature difference in the longitudinal section under the FPV conditions was 3.2 °C, while the relative humidity was 11.4%. The cooling efficiency of the fan-pad system ranged from 16.6% to 70.2%. The non-uniform coefficients of the temperature under the FPV conditions were higher than those under the NV conditions, while the nonuniform coefficients of the relative humidity were the highest during the day. The R2, MAE, MAPE and RMSE of the temperature-testing model were 0.91, 0.94, 0.11, and 1.33, respectively, while those of relative humidity model were 0.93, 2.83, 0.10, and 3.86, respectively. The results provide a reference for the design and management of Venlo greenhouses in South China.

CFD Model Verification and Aerodynamic Analysis in Large-Scaled Venlo Greenhouse for Tomato Cultivation

To address the challenges of climate change and food security, the establishment of smart farm complexes is necessary. While there have been numerous studies on the productivity and environmental control of individual greenhouses, research on greenhouse complexes is considerably limited. Conducting environmental studies during the design phase of these complexes poses financial constraints and practical limitations in terms of on-site experiments. To identify potential issues that may arise when developing large-scale greenhouse complexes, it is possible to utilize modeling techniques using computational fluid dynamics (CFD) to assess environmental concerns and location issues before constructing the facilities. Consequently, simulating large-scale CFD models that incorporate multiple greenhouses and atmospheric conditions simultaneously presents significant numerical challenges. The objective of this study was to design and verify the 3D CFD model for a large-scale Venlo greenhouse, where acquiring field data before construction is not feasible for designing a greenhouse complex. The verification of the CFD models was conducted using the improved grid independence test (GIT) and wall Y+ approaches. The findings revealed that a grid resolution of 0.8 m and a first-layer height of 0.04 m were suitable for developing large-scale greenhouse models, resulting in a low Root Mean Square Error (RMSE) of 3.9% and a high coefficient of determination (R2) of 0.968. This process led to a significant reduction of 38% in the number of grid cells. Subsequently, the aerodynamic characteristics and regional ventilation efficiency were analyzed in a 3D greenhouse model for developing a new large-scale greenhouse complex.

Energy-Saving Control Algorithm of Venlo Greenhouse Skylight and Wet Curtain Fan Based on Reinforcement Learning with Soft Action Mask

Due to the complex coupling of greenhouse environments, a number of challenges have been encountered in the research of automatic control in Venlo greenhouses. Most algorithms are only concerned with accuracy, yet energy-saving control is of great importance for improving economic benefits. Reinforcement learning, as an unsupervised machine learning method with a framework similar to that of feedback control, is a powerful tool for autonomous decision making in complex environments. However, the loss of benefits and increased time cost in the exploration process make it difficult to apply it to practical scenarios. This work proposes an energy-saving control algorithm for Venlo greenhouse skylights and wet curtain fan based on Reinforcement Learning with Soft Action Mask (SAM), which establishes a trainable SAM network with artificial rules to achieve sub-optimal policy initiation, safe exploration, and efficient optimization. Experiments in a simulated Venlo greenhouse model show that the approach, which is a feasible solution encoding human knowledge to improve the reinforcement learning process, can start with a safe, sub-optimal level and effectively and efficiently achieve reductions in the energy consumption, providing a suitable environment for crops and preventing frequent operation of the facility during the control process.

Closed-Loop Optimal Control of Greenhouse Cultivation Based on Two-Time-Scale Decomposition: A Simulation Study in Lhasa

Due to the heavy computation load of closed-loop simulations, optimal control of greenhouse climate is usually simulated in an open-loop form to produce control strategies and profit indicators. Open-loop simulations assume the model, measurements, and predictions to be perfect, resulting in too-idealistic indicators. The method of two-time-scale decomposition reduces the computation load, thus facilitating the online implementation of optimal control algorithms. However, the computation time of nonlinear dynamic programming is seldom considered in closed-loop simulations. This paper develops a two-time-scale decomposed closed-loop optimal control algorithm that involves the computation time. The obtained simulation results are closer to reality since it considers the time delay in the implementation. With this algorithm, optimal control of Venlo greenhouse lettuce cultivation is investigated in Lhasa. Results show that compared with open-loop simulations, the corrections in yield and profit indicators can be up to 2.38 kg m−2 and 11.01 CNY m−2, respectively, through closed-loop simulations without considering the computation time. When involving the time delay caused by the computation time, further corrections in yield and profit indicators can be up to 0.1 kg m−2 and 0.87 CNY m−2, respectively. These conservative indicators help investors make wiser decisions before cultivation. Moreover, control inputs and greenhouse climate states are within their bounds most of the time during closed-loop simulations. This verifies that the developed algorithm can be implemented in real time.

Exogenous application of glycine and nitrate on antioxidant and polyphenol metabolism in Brassica campestris spp. Chinensis

Pakchoi (Brassica campestris ssp. Chinensis) is a leafy vegetable which has been widely cultivated and consumed worldwide due to its low calorific value, a large supply of macro and micronutrients, beneficial phytochemicals and fibers. Amino acids have a vital role in plant nutrition; however, the effect of glycine and nitrate (Gly/NO3-N) on health-promoting phytochemicals, biomass, and antioxidant activities has gained a little attention. Thus, this study aimed to evaluate the impact of glycine and nitrate on health-promoting phytochemicals and yield/biomass of pakchoi. Glycine and nitrate were employed in different proportions (control, Gly/NO3-N = 3:1, Gly/NO3-N = 1:1, and Gly/NO3-N = 1:3 in the Venlo greenhouse, Shanghai Jiao Tong university, China. Results showed that compared to control, the treatment with Gly/NO3-N notably increased the secondary metabolites like polyphenols, flavonoids, glutathione (GSH), ascorbic acid (vitamin C), antioxidant potential (FRAP and DPPH value), and biomass in pakchoi plants. The contents of all antioxidants were high under the treatment of Gly/NO3-N（1:1). Interestingly, the contents of flavonoids were significantly enhanced (107.10%) by Gly/NO3-N = 1:1 than control plants. Furthermore, the content of Phe increased by 33.79%-86.32%, and also the activity of catabolic enzymes (CHI, CHS, C4H, and PAL) of the polyphenols pathway was found to be significantly enhanced while the activity of 4CL and DFR was restrained by the treatment of Gly/NO3-N, compared with control plants. In addition, the correlation analysis of polyphenols and flavonoids with Phe, PAL, C4H, CHS, and CHI showed a positive correlation, while a negative correlation was found in the case of 4CL and DFR. Taken together, the current findings suggest that the application of Gly/NO3-N enhanced polyphenols metabolism as well as increased the total polyphenolic content and antioxidant activity. Consequently, this combination of glycine and nitrate could be used to promote beneficial phytochemicals and yield/biomass of pakchoi.

Numerical investigation for effects of natural light and ventilation on 3D tomato body heat distribution in a Venlo greenhouse

Maintaining suitable temperature level around tomato in the greenhouse is essential for the high-quality production. However, in summer, the temperature level around the tomato is usually unclear except using a high-precision temperature imager. To solve this problem, thermal performance of 3D (three-dimensional) tomato model built based on SolidWorks was investigated by the computational fluid dynamics (CFD) simulations. To assess the effect of temperature distribution around the tomato, a simplified 3D tomato numerical model was firstly validated by a set of field measurement data. The light intensity and indoor ventilationwere regarded as the mainly environment factors in the Venlo greenhouse, thermal stratification around tomatoes at different time of day was further studied. The numerical results illustrated the different temperature distribution around tomato body under different radiation intensity. It was found that ventilation could obviously adjust the temperature gradient around the tomato, and alleviate high temperature effect particularly in summer. Suitable ventilation could create a suitable thermal environment for the tomato growth. This study clearly demonstrated 3D temperature distribution around tomatoes, which is beneficial to provide the reference for accurate detection of 3D tomato temperature and appropriate thermal environment design.

Optimization of light, energy and water use efficiencies in an improved Venlo greenhouse

Optimization of light, energy and water use efficiencies in an improved Venlo greenhouse

Energy Consumption Prediction of a Greenhouse and Optimization of Daily Average Temperature

Greenhouses are high energy-consuming and anti-seasonal production facilities. In some cases, energy consumption in greenhouses accounts for 50% of the cost of greenhouse production. The high energy consumption has become a major factor hindering the development of greenhouses. In order to improve the energy efficiency of the greenhouse, it is important to predict its energy consumption. In this study, the energy consumption mathematical model of a Venlo greenhouse is established based on the principle of energy conservation. Three optimization algorithms are used to identify the parameters which are difficult to determine in the energy consumption model. In order to examine the accuracy of the model, some verifications are made. The goal of achieving high yield, high quality and high efficiency production is a problem in the study of greenhouse environment control. Combining the prediction model of greenhouse energy consumption with the relatively accurate weather forecast data for the next week, the energy consumption of greenhouse under different weather conditions is predicted. Taking the minimum energy consumption as the objective function, the indoor daily average temperatures of 7 days are optimized to provide the theoretical reference for the decision-making of heating in the greenhouse. The results show that the optimized average daily temperatures save 9% of the energy cost during a cold wave.

Thermal analysis of greenhouses installed under semi arid climate

The greenhouse design as well as the cover material properties in particular may strongly impact the greenhouse energy. To study the effect of these parameters, three typical unheated greenhouses equipped with rows of canopy were considered. Experiments were launched to establish the boundary conditions and validate the model. Two parametric studies were carried out: for the nocturnal period when the energy performance of each type of greenhouse was investigated, and for the diurnal period, when the sun path was simulated taking into account the type of the cover, its spectral optical and thermal properties. Results indicate that for the nocturnal period, the ambient air temperature in the tunnel and vertical wall greenhouse was relatively homogenous and warmer compared with the temperature distribution in the Venlo greenhouse. The plastic greenhouse, especially the tunnel one had better performances concerning the homogenization of the climate and the thermal energy storage. Concerning the diurnal period, and for both plastic greenhouses equipped with fully opened side vents, the air located between the rows of canopy and ground surfaces remained very slow, not exceeding 0.2 ms-1; for the Venlo glasshouse, the recirculation loop situated above the crop improved the air mixing and induced a good homogenization. Results indicate that the cover material with highest absorptivity, deteriorated the natural ventilation, increasing the air temperature by convection, and reduced the available Photosynthetically Active Radiation.

Greenhouse concept with high insulating cover by combination of glass and film: design and first experimental results

Dutch greenhouse horticulture puts a lot of effort in reduction of energy demand. Using (multiple) thermal screens, mainly during night, is the most common way to reduce heat losses in practice. In winter, even during daytime, transparent screens are closed, which saves energy, but results in significant reduction of light at plant level. For additional saving a substantial increment of greenhouse insulation is needed. Double covering materials can reach very high insulation levels, resulting in energy savings of 50% compared to the use of single glass with screens. Drawback of insulating glass panels are high investment and problems with snow accumulation in Northern latitudes. A new greenhouse concept with a new type of covering material has recently been developed. The insulating cover consists of a combination of a high transparent glass panel in combination with a high transparent and durable plastic film (F-Clean). The insulation properties are flexible. By blowing warm air through the split, possible snow accumulation is expected to be avoided. The new greenhouse concept has a new roofing structure including a different type of ventilation for a Venlo greenhouse. In a feasibility study, different combinations of different types of glass with different types of F-Clean have been investigated at Wageningen UR LightLab. Different model calculations have been carried out to study the effects on greenhouse climate and energy consumption. The results of a feasibility study with the search for the best combination of glass and plastic film in terms of transmissivity and light diffusing properties as well as the calculated energy savings of the total greenhouse concept are presented. In summer 2014, this concept was built on a scale of 500 m2 at the research station of Wageningen UR Greenhouse Horticulture in Bleiswijk. The first results of a tomato experiment, using new crop growing strategies are presented.

Accelerating ripening of greenhouse tomatoes in autumn at the end of harvest with ethylene application

Accelerating maturation of greenhouse tomatoes at the end of the growing season permits to save energy and to reduce the quantity of unripe tomatoes. Indeed, at the end of the cropping season, several kg m-2 of tomatoes do not reach a degree of maturity permitting them to be sold. In Switzerland, it was possible to accelerate the ripening of tomatoes by applying ethephon, a product which releases ethylene. Since August 2014, this product is no longer authorized, in Switzerland. An alternative is the application of ethylene, a naturally occurring hormone, directly in the greenhouse. In collaboration with the company Carbagas, Agroscope tested the effect of ethylene application on tomato ripening. The trials were conducted in 2012 and 2013 in two identical compartments of a Venlo greenhouse. In one compartment, ethylene was injected at a concentration of 10 ppm during nine or ten nights. The other compartment served as control. In 2012, tomatoes 'Levanzo', 'Komeett' and 'Endeavour' were planted and in 2013 'Endeavour'. In average over the two years, the application of ethylene enabled to harvest 1.5 truss m-2 or 0.75 kg m-2 (1.5% of the total yield) more compared to the control compartment. The quality of tomatoes at harvest (acidity, firmness and total soluble substances) was only slightly influenced by the addition of ethylene. Economically, such an application seems profitable. Registration for the application of ethylene in greenhouse is in progress in Switzerland.

Early diagnosis and monitoring of nitrogen nutrition stress in tomato leaves using electrical impedance spectroscopy

Abstract: Nitrogen (N) is a life element for crop growth. In tomato growth and development, N stress often occurs and degrades crop yield and quality. Superfluous N can noticeably increase the nitrate content, which can be degraded into strong carcinogenic substance- nitrite. An accurate and timely monitoring and diagnosis of nutrition during crop growth is premise to realize a precise nutrient management. Crop N monitoring methods have been developed to improve N fertilizer management, and most of them are based on leaf or canopy optical property measurements. Although many optical/spectral plant N sensors have already commercialized for production use, low accuracy for phosphorus (P) and potassium (K) detection and diagnosis remains an important drawback of these methods. To explore the potential of N diagnosis by electrical impedance and perform study for nutrition status of plant NPK meanwhile by the electrical impedance, it is necessary that evaluate the N nutrition level by leaf impedance spectroscopy. Electrical impedance was applied to determine the physiological and nutritional status of plant tissues, but few studies related to plant N contents have been reported. The objective of this study was to evaluate the N nutrition level by leaf impedance spectroscopy and realize the early diagnosis and monitoring of N nutrition stress in tomato. Five sets of tomato plant samples with different N contents were cultivated in a Venlo greenhouse. N content of leaves was determined, and electrical impedance data were recorded in a frequency range of 1 Hz to 1 MHz. The obtained impedance data were analyzed using an equivalent circuit model for cellular tissues. The variation of equivalent parameters along with N content was analyzed, and the sensitive impedance spectroscopy characteristics of N nutrition level were extracted. Furthermore, the effect of moisture content on impedance measurement was discussed and the prediction model for N content was developed. Results showed that electrical impedance can be conveniently applied to early diagnosis and monitoring for tomato N nutrition stress. Keywords: electrical impedance spectroscopy, nitrogen stress, tomato (Solanum lycopersicum) leaves, nitrogen nutrition, diagnosis, monitoring, nondestructive detection DOI: 10.3965/j.ijabe.20171003.3188 Citation: Li M Q, Li J Y, Wei X H, Zhu W J. Early diagnosis and monitoring of nitrogen nutrition stress in tomato leaves using electrical impedance spectroscopy. Int J Agric & Biol Eng, 2017; 10(3): 194–205.

Effect of the greenhouse design on the thermal behavior and microclimate distribution in greenhouses installed under semi‐arid climate

AbstractGreenhouse design and cover material properties may strongly impact greenhouse energy. To study the effect of these parameters, three typical unheated agricultural buildings equipped with rows of canopy were considered, and two‐dimensional simulations were conducted using the discrete ordinate model for simulating radiative transfers. Experiments were conducted to establish the boundary conditions and to validate the model. Two parametric studies were carried out: one for the nocturnal period when the energy performance of each type of greenhouse was investigated, and one for the diurnal period, when the sun path was simulated taking into account the type of the cover, its spectral optical and thermal properties. Results indicate that for the diurnal period, and for both plastic greenhouses equipped with fully opened side vents, the air located between the rows of canopy and ground surfaces remained very slow, not exceeding 0.2 m/s; for the Venlo glasshouse, the recirculation loop situated above the crop improved the air mixing and induced a good homogenization. Results also indicate that the cover material with the highest absorptivity, deteriorated the natural ventilation, increasing the air temperature by convection, enhancing local air temperature favoring the development of a secondary recirculation, and reduced the available photosynthetically active radiation. Concerning the nocturnal period, the ambient air temperature in the tunnel and in the vertical wall of the greenhouse was relatively homogenous and warmer than the temperature in the Venlo greenhouse. During the nocturnal period, the plastic greenhouse (in particular the one with the tunnel) performed better in regard to the homogenization of the climate and thermal energy storage.

A numerical simulation of the photovoltaic greenhouse microclimate

Accurately predicting the distributed microclimate inside greenhouse equipped with photovoltaic panels would be a prerequisite to developing a sustainable energy-saving greenhouse. Predicting the microclimate can contribute to enhanced performance in these kinds of greenhouses by improving the radiation transmission efficiency inside.In this context, solar radiation distribution, thermal air, water vapor and the dynamics fields were simulated using the Computational Fluid Dynamic (CFD) model in two different prototypes of greenhouses (Asymmetric and Venlo) equipped with photovoltaic panels on their roof. Crop cover characteristics and the interactions between crops and airflow were taken into account. Two arrangements of photovoltaic panels array were tested straight-line and checkerboard.A detailed description of the thermal, dynamic and radiation fields inside the greenhouses was obtained and the analysis of data collected during this study show that (i) solar radiation is more evenly distributed in the Venlo greenhouse than in the Asymmetric greenhouse. On average, the mean solar radiation transmission in the Asymmetric greenhouse is 41.6% whereas that of the Venlo greenhouse is 46%. (ii) Compared to the straight-line arrangement, the checkerboard photovoltaic panel setup improved the balance of the spatial distribution of sunlight received in the greenhouse.

ENVIRONMENTAL IMPACT ASSESSMENT OF DUTCH TOMATO CROP PRODUCTION IN A VENLO GLASSHOUSE

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Greenhouse 2010 and Soilless Cultivation ENVIRONMENTAL IMPACT ASSESSMENT OF DUTCH TOMATO CROP PRODUCTION IN A VENLO GLASSHOUSE

Minderung der CO2-Emissionen durch effizienten Energieeinsatz im Unterglasgartenbau

Depending on the technology used, the operational system and the crop being grown, around 500000 kWh heating energy per year is required for a 1000 m2 ground area greenhouse. Reducing heat losses from such buildings is very important for increasing energy efficiency through less energy costs and carbon dioxide emissions. The installation of an energy shield is very efficient in this respect, offering energy savings of approx. 25 %. Further energy savings can be achieved with two-layer greenhouse walls and roof. Combining technical and management measures heating energy requirement for a 1000 m2 greenhouse can be reduced by up to 60 %. This could mean an around 124 t reduction in annual carbon dioxide emissions from a Venlo greenhouse with oil-fired heating. In that some of these energy saving actions also save operating costs, negative carbon dioxide reduction costs are achieved in most variants.

Temperature Distribution in a Naturally Ventilated Venlo Greenhouse with Six Spans and High Eaves

Temperature Distribution in a Naturally Ventilated Venlo Greenhouse with Six Spans and High Eaves

LIGHT INTERCEPTION OF LIGHTING SYSTEMS, VENLO AND WIDE SPAN TYPE GREENHOUSES

TNO has developed a computer program to calculate the light interception of the greenhouse structure using an improved half-perimeter method, taking into account reflections and shadowing. This program is used to compare the light interception of Venlo and Wide span type greenhouse. Furthermore the influence of artificial lighting on the total light interception is considered. The objective is to minimize the light interception of the greenhouse structure (with and without lighting equipment). The computer program is widely used by greenhouse construction companies and suppliers to improve the light interception of their greenhouses. The theory is also implemented in the Dutch Greenlabel programme, to stimulate energy efficient greenhouses. The program is used to compare several common types of the Venlo greenhouse type. The following parameters are varied: bay width, glass panel width, vent size, gutter type and light intensity level of the lighting system. The total range of light interception is about 7 % (difference between maximum and minimum light interception of the greenhouse including lighting system). The range of the lighting system is 3% Concluded is that a 4 meter bay width together with 1,67 meter glass panels is the most favorable Venlo greenhouse type. Integration of the lighting system with the structure can improve the light interception with 0,7%.

RECEDING HORIZON OPTIMAL CONTROL OF A SOLAR GREENHOUSE

A solar greenhouse has been designed that maximizes solar energy use and minimizes fossil energy consumption. It is based on a conventional Venlo greenhouse extended with a heat pump, a heat exchanger, an aquifer and ventilation with heat recovery. The goal is to minimize fossil energy consumption, while maximizing crop dry weight, keeping temperature and humidity within certain limits and satisfying a temperature integral. To achieve this the aim is to implement a receding horizon optimal controller. This type of controller computes optimal closed loop controls based on a cost function and a greenhouse and crop model. In this paper simulations of a simplified version of this closed loop optimal control system are presented. It is found that the boiler use is reduced, thereby reducing fossil energy use. Gas use is decreased by 77% compared to a conventional greenhouse with optimal control.