Single-span Greenhouse Research Articles

Effects of Aluminum-Metalized Film on Improving Growth and Heat Insulation in Single-span Greenhouse for Semi-forcing Culture of Cherry Tomato

Effects of Aluminum-Metalized Film on Improving Growth and Heat Insulation in Single-span Greenhouse for Semi-forcing Culture of Cherry Tomato

Dynamic neural network modeling of thermal environments of two adjacent single-span greenhouses with different thermal curtain positions

In order to produce marketable yield, scientific methodologies must be used to forecast the greenhouse microclimate, which is affected by the surrounding macroclimate and crop management techniques. The MATLAB tool NARX was used in this study to predict the strawberry yield, indoor air temperature, relative humidity, and vapor pressure deficit using input parameters such as indoor air temperature, relative humidity, solar radiation, indoor roof temperature, and indoor relative humidity. The data were normalized to improve the accuracy of the model, which was developed using the Levenberg–Marquardt backpropagation algorithm. The accuracy of the models was determined using various evaluation metrics, such as the coefficient of determination, mean square error, root mean square error, mean absolute deviation, and Nash–Sutcliffe efficiency coefficient. The results showed that the models had a high level of accuracy, with no significant difference between the experimental and predicted values. The VPD model was found to be the most important as it influences crop metabolic activities and its accuracy can be used as an indoor climate control parameter.

Effect of horizontal and radial airflow fans on the microclimate of single-span greenhouses and their yield

The present study evaluated and compared the distribution patterns of microclimatic parameters within greenhouses to provide insights into optimizing growing conditions and maximizing crop productivity. Experiments were conducted from January to March 2023 at Sangju Smart Farm Innovation Valley, Sangju-si, South Korea, in two adjacent greenhouses covered with two polyolefin layers and a thermal screen layer. The distinctive design of the radial airflow fan connecting to the external environment and ability to uniformly blend air, demonstrated superior performance than the horizontal air flow fan. The adoption of radial airflow fans could greatly influence commercial production by enhancing the distribution of microclimate variables, resulting in improved greenhouse efficiency and ultimately leading to increased crop yields.

Thermal Environment Analysis of Selected Polyethene Cladded Single-Span Greenhouse Shapes Models Towards Cooling Needs

Greenhouse energy management is one of the most significant factors of consideration in greenhouse agriculture. Besides implementing energy supply systems to the facility, energy-saving measures must also be taken into consideration. To address the issue of energy demand by greenhouses in a tropical environment, three greenhouse models were developed to simulate their thermal environments utilizing the Transient Systems Simulation Program (TRNSYS 18) as a building energy simulation (BES) platform. The proposed models were used to examine the impact of greenhouse design parameters; roof shape, orientation, covering (polyethene), and ventilation, on their temperature, relative humidity (RH), vapour pressure deficit (VPD), and cooling load. It was found that the most suitable roof design and orientation was the split-gable roof design with the ventilation switched on and 0o (E-W) orientation that had the lowest mean temperature of 24.12 oC and the least cooling demand of 454.59W. While the tunnel greenhouse had the highest cooling load of 21.30 kW. The split-gable greenhouse had. Also, the RH and VPD in the split-gable greenhouse with ventilation were within the acceptable ranges of 50-75% and 0.8 and 1.1 kPa, respectively, for successful greenhouse crop production. The developed models can aid greenhouse farmers in knowing the cost-benefit of a greenhouse before venturing into greenhouse agriculture in the tropical regions.

Effects of Concrete Block Flooring on Greenhouse Microclimate and Floor Surface Heat Balance

Greenhouse floor management is essential for effectively utilizing solar energy in horticultural production. Covering soil floors with concrete is one method of greenhouse floor management. This paper assesses the effects of this method on greenhouse microclimate and floor surface heat balance by comparing two adjacent single-span greenhouses, namely, an “interlocking concrete block floor” greenhouse (ICFG) and an “uncovered soil floor” greenhouse (SFG). During days with high solar radiation in 2019 winter, the maximum air temperature was 10.0°C lower, and the average vapor pressure was 0.5 kPa lower in the ICFG than in the SFG. On clear nights, the average air temperature was 1.6°C higher in the ICFG than in the SFG. The concrete floor had a higher albedo than the soil floor. This contributed to the lower daytime temperatures in the ICFG. The lower heat absorption by the concrete during the day was more than compensated for by a larger total transmission of heat from the ground to the greenhouse air at night due to the greater thermal conductivity of concrete. These results indicate that replacing soil floors with concrete floors could help farmers avoid temperature extremes and high daytime humidity without requiring external energy derived from fossil fuels or other sources.

Growth Environmental Factors and Fruit Enlargement of Seedless Watermelon according to Directions of Single-Span Greenhouse

Growth Environmental Factors and Fruit Enlargement of Seedless Watermelon according to Directions of Single-Span Greenhouse

Rooftop Greenhouse: (2) Analysis of Thermal Energy Loads of a Building-Integrated Rooftop Greenhouse (BiRTG) for Urban Agriculture

Building-integrated rooftop greenhouses (BiRTGs) are innovative vertical farms consisting of a greenhouse on the roof of a building. BiRTGs can provide environmental benefits by recycling energy, carbon dioxide, and water between the greenhouse and the building. Moreover, BiRTGs can reduce cooling and heating loads by reducing the exposure of the building surface to heat gains/losses through the roof. However, the benefits of BiRTGs have not yet been completely elucidated from an energy perspective. This study aimed to analyse the energy-saving efficiency of BiRTGs using building energy simulations (BES) and computational fluid dynamics (CFD) techniques. BES is a calculation method for analysing the heating and cooling loads of buildings; however, it was difficult to consider time-dependent changes in the ventilation characteristics in the BES model. CFD can be used to calculate more detailed ventilation characteristics of an experimental facility. Thus, CFD and the BES were combined to obtain more accurate BES-based data. The BES-computed annual energy load for a single-span greenhouse in which tomatoes were grown was 490,128 MJ, whereas the annual energy load for growing tomatoes in a BiRTG resulted in a 5.2% reduction, on average (464,673 MJ). The energy-saving effects were positive from October to April because the BiRTG helped transmit heat energy transmitted from the building to the greenhouse. Regarding the total energy load in the BiRTG after alternating the air temperature management (ATM), the heating energy load was reduced in the winter. ATM was expected to apply from November to March, with average energy savings of 11.8%.

Effect of Different Height of Side Vents on Microclimate in a Single-Span Greenhouse during Natural Ventilation

Effect of Different Height of Side Vents on Microclimate in a Single-Span Greenhouse during Natural Ventilation

Estimation of Photosynthesis Loss Due to Greenhouse Superstructures and Shade Nets: A Case Study with Paprika and Tomato Canopies

In horticultural greenhouses, the photosynthetic photon flux density (I) is inevitably lower than that outside because of interference from greenhouse superstructures (e.g., reflection and absorption of radiation by greenhouse coverings and superstructures). In addition, during hot seasons in many regions, I can be lowered by shade nets installed to reduce excessive radiation. These reductions in I can cause a decrease in the canopy photosynthetic rate (Ac), potentially leading to crop yield losses. This study investigated to what extent Ac is reduced inside a modern greenhouse and under a shade net in comparison with that outside. A simple Ac model (i.e., canopy-scale photosynthesis-light curves) was parameterized based on the measurements of Ac and I for paprika and tomato canopies using the open-chamber method. In addition, based on the measurements of I, linear regression models were derived that related outside I (Iout) with I inside arch-roofed, single-span greenhouses [enveloped with a diffuse ethylene tetrafluoroethylene (ETFE) film; Iin] and I under shade nets (composed of aluminum and polyester strips; Ish). An Ac simulation using these models indicated that on a typical sunny summer day in Japan, Ac inside the greenhouses and under the shade nets (Ac,in and Ac,sh, respectively) corresponded to 91% and 52% of Ac outside (Ac,out) for the paprika canopy (for the tomato canopy, Ac,in and Ac,sh corresponded to 90% and 48% of Ac,out, respectively). The simulated Ac loss was more serious on a cloudy day because of the linear Ac-I response under low I conditions (Ac,in/Ac,out and Ac,sh/Ac,out were 69% and 13%, respectively, for the paprika canopy). The loss of Ac,sh may be alleviated by limiting the shading period to only midday hours.

Evaluating the Effect of Cover Materials on Greenhouse Microclimates and Thermal Performance

This study compared and analyzed changes in the microclimate and thermal environment inside single-span greenhouses covered with a single layer of plastic film, polycarbonate (PC), and glass. The results of the experiment show that the PC-covered greenhouse was the most favorable for managing the nighttime heating effect during the cold season. However, the glass-covered greenhouse was found to be the most favorable for managing the cooling effect during the hot season. Although the plastic-covered greenhouse was inexpensive and easy to install, the air temperature inside varied significantly, and it was difficult to control its indoor environment. The thermal load leveling values showed that the PC-covered greenhouse had the lowest variation, confirming its superiority in terms of environmental control and energy savings. In terms of the overall heat transfer, heat was generally transferred from the interior to the exterior of the greenhouses. In the plastic-covered greenhouse, however, heat was transferred in the opposite direction at night due to the influence of radiant cooling. The occurrence of the minimum and maximum heat transfer values had a tendency similar to that of the occurrence of the minimum and maximum air temperatures inside the greenhouses.

Analysis and Monitoring of Environmental Parameters in a Single-span Greenhouse during Strawberry Cultivation

Analysis and Monitoring of Environmental Parameters in a Single-span Greenhouse during Strawberry Cultivation

Effect of the Pipe Joint on Structural Performance of a Single-span Greenhouse: A Full-scale Experimental and Numerical Study

본 연구에서는 원예특작시설 내재해형 규격서에 등록되어 있는 폭이 넓은 단동온실(10-단동-5형)을 대상으로 기초의 경계조건과 서까래 강관의 이음 유무에 대해 실물 크기 실험을 실시하고 그 결과를 수치해석 결과와 비교하여 이음부가 있을 때 구조성능 차이에 대해 알아보았다. 각 측정 위치별 변위를 실험에서 측정한 값과 수치해석으로 예측한 값을 비교한 결과에서는 기초의 조건 및 서까래 강관 이음 유무에 상관없이 모두 상당한 차이를 보였고, 힌지 조건 보다 고정 조건이 상대적으로 차이가 컸다. 그리고 모든 절점을 강접합으로 가정하고 구조해석한 결과를 구조실험과 비교한 결과에서는 힌지조건이 고정조건 보다 잘 일치하였지만 해석값이 실험값 보다 크게 나타났다. 수치해석은 모든 절점을 강접합으로 가정했기 때문에 실제 성능과 달랐다. 따라서 현재 모든 절점을 강접합으로 가정하고 온실을 설계를 하면 과소설계될 우려가 있어 앞으로 신뢰성 높은 온실 설계를 위해서는 서까래와 도리가 교차하는 교차부 성능 특성을 고려한 구조해석 기술 개발이 이루어져야 할 것으로 판단된다.

Structural design and experimental tests on a model of tensegrity greenhouse prototype

The aim of this paper is the analysis, proposal and application of a structural tensegrity configuration for greenhouses supporting structures suitable for lightweight covering, based on principles of design coherence, material savings and building durability. By means of the FEM software, Sofistik®, a tensegral greenhouse prototype was modelled and designed in accordance with EN 13031-1:2019. In order to calibrate the results of the FEM analysis, experimental load tests and displacement measurements made with a tensegrity reduced scale model on a tensegrity reduced scale model, created at the Department laboratory of the University of Bari, were compared with the results of the calculation analysis. The displacements of the prototype selected nodes were detected by Target tracking Technology in two load configurations and a control transducer was positioned on the central structural node. The comparison among the displacements of the detected nodes with those resulting from the FEM software calculations, for two different load configurations, show average percentage errors of 7.1% and 12.55%. The results of the T test for the different load configuration point out that the two series of values experimentally detected and calculated by the software are not significantly different. Finally, results in terms of the structural steel weight and maximum stress of the tensegral structure were compared with those of commercial structures, both with vaulted roof and duopitched roof, of single span greenhouses having the same covered ground area of the greenhouse prototype. The proposed tensegrity greenhouse prototype showed a 9.6% and 35.2% reduction of the structural steel weight compared to the vaulted roof and to the duo-pitched roof greenhouse respectively.

Numerical Analysis of the Effect of Ground Dampness on Heat Transfer between Greenhouse and Ground

This paper deals with the problem of the influence of ground dampness on heat exchange between greenhouse and ground. The effect of humidity on the distribution of ground temperature fields was analyzed. The analysis was performed based on the analytical numerical method in the WUFI®plus software. The computational tool was used after a validation process. Research and simulations were conducted on the example of a real single-span greenhouse located in Southern Poland. The results of indoor and outdoor air temperature measurements were used to determine the boundary conditions, while the measured ground temperatures were used to compare with the results of theoretical calculations. Three variants were used for calculation analysis, assuming different levels of ground dampness. Analysis of the test results showed that during the summer period, dry ground provides 8% more thermal energy to the interior of the greenhouse than the damp ground, and provides 30% more thermal energy than wet ground. In the transition period (autumn/spring), the ground temperature fields are arranged parallel to the floor level, while the heat flux is directed from the ground to the interior of the greenhouse, regardless of the ground dampness level. During this period, the ground temperature ranges from 4.0 °C to 13.0 °C. Beneficial effect of dry ground, which contributes to maintaining an almost constant temperature under the greenhouse floor, was found in winter.

Computational fluid dynamics analysis of ventilation characteristics with various design parameters in single-span greenhouses

ABSTRACT With the advent of the fourth industrial revolution, smart farming technology is being introduced that can properly maintain the growing environment of crops remotely and automatically by grafting information and communication technology (ICT) to greenhouses. To maintain an appropriate growth environment for these crops, the effects of the greenhouse design parameters on these environments need to be evaluated. In this study, the thermal and flow characteristics in the single-span greenhouse were examined with commercial computational fluid dynamics (CFD) code. To validate the numerical method applied herein, the numerical results of the temperature distribution at several monitoring points were compared with the experimental results. The low-average error rate (0.87–1.90%) between them was measured and the numerical results of the temperature distribution exhibited good agreement with the experimental data. In addition, a parametric study was conducted to determine the effects of the various design parameters on the ventilation performance. These study findings will offer appropriate data for design guidelines for greenhouses.

Innovative Design of a Ventilated Modern Greenhouse Powered by PV/T Solar System

In this paper, a modern design is proposed for ventilating and conditioning of greenhouse integrated thermal solar system in summer season in (33.3°N, 44.4 °E) Baghdad, Iraq with respect to East-West orientation. The proposed system involves photovoltaic panels and counter flow double pass (with fins). The photovoltaic solar thermal system is fixed on the roof of single span greenhouse. Experimental work was carried out during summer season. The results show the ventilation process changes the air inside temperature of the greenhouse to make it equal to the temperature required by the plants. The calculated root mean square error is 2.04 and correlation factor is 0.993 for the inside air temperature and 4.98, 0.98 respectively for the ground temperature.

Wind Fragility of Steel and Carbon-Fiber Reinforced Plastic Single-Span Greenhouses

Wind Fragility of Steel and Carbon-Fiber Reinforced Plastic Single-Span Greenhouses

Analysis on Heat Loss of Single-span Greenhouse Using Small-scaled Wind Tunnel

Analysis on Heat Loss of Single-span Greenhouse Using Small-scaled Wind Tunnel

Spatial distribution of air temperature and relative humidity in the greenhouse as affected by external shading in arid climates

The effect of external roof shading on the spatial distribution of air temperature and relative humidity in a greenhouse (Tin and RHin) was evaluated under the arid climatic conditions of Riyadh City, Saudi Arabia. Two identical, evaporatively-cooled, single-span greenhouses were used in the experiment. One greenhouse was externally shaded (Gs) using a movable black plastic net (30% transmissivity), and the other greenhouse was kept without shading (Gc). Strawberry plants were cultivated in both greenhouses. The results showed that the spatial distribution of the Tin and RHin was significantly affected by the outside solar radiation and evaporative cooling operation. The regression analysis showed that when the outside solar radiation intensity increased from 200 to 800 W m–2, the Tin increased by 4.5°C in the Gc and 2°C in the Gs, while the RHin decreased by 15% in the Gc and 5% in the Gs, respectively. Compared with those in the Gc, more uniformity in the spatial distribution of the Tin and RHin was observed in the Gs. The difference between the maximum and minimum Tin of 6.4°C and the RHin of 10% was lower in the Gs than those in the Gc during the early morning. Around 2°C difference in the Tin was shown between the area closed to the exhausted fans and the area closed to the cooling pad with the external shading. In an evaporatively-cooled greenhouse in arid regions, the variation of the Tin and RHin in the vertical direction and along the sidewalls was much higher than that in the horizontal direction. The average variation of the Tin and RHin in the vertical direction was 5.2°C and 10% in the Gc and 5.5°C and 13% in the Gs, respectively. The external shading improved the spatial distribution of the Tin and RHin and improved the cooling efficiency of the evaporative cooling system by 12%, since the transmitted solar radiation and accumulated thermal energy in the greenhouse were significantly reduced.

Поликарбонатные теплицы с трансформируемой кровлей

Single-span arch and frame greenhouses with polycarbonate roof are considered. Cultivation facilities of this type are supplied by manufacturers for small forms of management. Polycarbonate roof has a number of advantages over plastic and glass fencing: it provides energy saving during the cold season, resists impact loads and does not require operating costs. However, during the summer, due to the greenhouse effect in the polycarbonate greenhouse, a significant temperature increase is possible, reducing the yield of agricultural products and deteriorating its quality. The maximum decrease in temperature in the structure is possible with natural air exchange through a tape ventilation opening created by lifting the ridge part of the roof. According to the results of the experiment, the aeration parameters necessary to reduce the internal temperature are established on the model of the greenhouse - the width of the tape opening and the height of the roof, expressed as a function of the span of the cultivation structure. The possibility of reducing the costs for the construction of a greenhouse in small form of ownership farms compared to the costs for the greenhouse of the factory supply are considered. The constructive scheme of a single-span frame greenhouse of construction production with a frame from rolling profiles with nodal connections on welding and enclosing designs from polycarbonate panels is offered. The dependences for determination of energy-efficient space-planning dimensions of the structure and steel consumption on the frame elements as a function of the parameters influencing it are derived. For the first three snow areas the pitch of frame frames corresponding to the minimum of steel consumption is justified.