Single-span Greenhouse Research Articles

Comparison of solar transmittance through a small single-span greenhouse covered by diffusive and clear films

Comparison of solar transmittance through a small single-span greenhouse covered by diffusive and clear films

Simulation of thermal performance of solar greenhouse in north-west of Iran: An experimental validation

Application of solar energy in greenhouse heating during the cold months could be of great importance. In this study, six shapes of greenhouses including: uneven span, even span, single span, vinery, quonset and arch type were compared from solar radiation availability point of view. A dynamic model was developed to predict all the internal greenhouse temperatures including inside air, soil surface and north wall temperatures for the selected greenhouse. In this model the radiation component of the heat transfer was used along with the other heat transfer modes. Experimental validation to obtain required parameters was conducted in single span greenhouse (in east-west orientation). The results showed that, as compared to other shapes, the single span shape greenhouse oriented in east-west orientation received about 8% more solar radiation during all the months in a year. It was also determined that using brick wall at north side of the greenhouse can reduce radiation energy loss in this type of greenhouse. The average value of the cover transmittance was estimated to be 0.76 during the period of the experiment. A good agreement was obtained comparing measured and predicted values.

단동온실의 태양복사에 의한 열유동 특성 해석

단동온실의 태양복사에 의한 열유동 특성 해석

Effects of the spacing of roof ventilation devices on the environment and the yield of oriental melons in single-span plastic greenhouses

The purpose of this study is to provide the standard for the proper installation of roof ventilation devices in single-span plastic greenhouses. The amount of ventilation was 19,140 m3 h-1 in the greenhouse with fans installed at intervals of 15 m, and 15,845 m3 h-1 with fans installed at intervals of 20 m. The amount of ventilation was 14,961 m3 h-1 in the greenhouse with stacks installed at intervals of 6 m, and 13,414 m3 h-1 with stacks installed at intervals of 8 m. As a result of analyzing changes in average day-time temperature during June, a high-temperature period, it was found that the narrower the spacing of ventilation devices, the lower the air temperature; and that air temperature in the greenhouse with fans was lower than that in the greenhouse with stacks. As a result of examining the yield of oriental melons per the span of greenhouse (605 m2), it was found that the yield in the greenhouse with fans installed at intervals of 15 m was 5,075 kg, 8.6% more than that in the greenhouse with fans installed at intervals of 20 m. And the yield in the greenhouse with stacks installed at intervals of 6 m was 4,405 kg, 7.2% more than that in the greenhouse with stacks installed at intervals of 8 m. As a result of analyzing economic efficiency according to roof ventilation device treatments, taking into account the value of oriental melon production, the depreciation of ventilation devices, the electric charges, and the expenses for selection and packaging, it was found that income increased KRW 865,450 in the case of spacing fans 15 m apart, compared with the case of spacing them 20 m apart; and that income increased KRW 660,690 in the case of spacing stacks 6 m apart, compared with the case of spacing them 8 m apart.

Evaluation of wind-driven natural ventilation of single-span greenhouses built on reclaimed coastal land

Recently, the government of South Korea announced the construction plan for a large-scale greenhouse complex on reclaimed coastal lands. Wind characteristics of the coastal regions are quite different from those of inland. Natural ventilation of greenhouses is strongly dependent on the exterior wind characteristics; therefore, the effects of topographical and meteorological characteristics of the coastal regions on ventilation rate should be carefully evaluated to ensure stable and uniform production of the crops. In this study, wind-driven natural ventilation rates of single-span greenhouses were evaluated using a computational fluid dynamics (CFD) technique examining greenhouse type and typical wind conditions found in reclaimed lands. The accuracy of the designed CFD model was validated by comparing the result of the CFD simulation with the results of particle image velocimetry (PIV) measurements that were conducted in a wind tunnel. Furthermore, grid independence test and turbulence model test were conducted for validation of the designed CFD model. From these validated CFD model, the overall ventilation rates were estimated using two methods, mass flow rate (MFR) and tracer gas decay (TGD) methods according to greenhouse type, wind speed, wind direction, and configuration of the ventilator. Furthermore, local ventilation rates of the greenhouse were estimated using the TGD method. The CFD computed ventilation rates of greenhouses were evaluated by comparing them with the ventilation rates required for controlling the temperature in greenhouses. Finally, charts, which can be used to predict the natural ventilation rate of the single-span greenhouse built on reclaimed land, were developed.

Wind-driven natural ventilation of greenhouses with vegetation

A large eddy simulation (LES) model was used to examine the wind-driven cross ventilation of gable-roof greenhouses containing vegetation. The obstruction of air flow by vegetation was described by a porous drag model in the numerical model, and the simulation results were validated using wind tunnel experiments. The numerical model was then utilised to inspect the influences of vegetation and greenhouse length (in the wind direction) on the ventilation rate. The results revealed that the diminishing effects of the vegetation, insect screen and internal friction on the ventilation rate can all be quantified by a physical-based resistance model. The driving force (the difference between windward and leeward pressures) of long, multi-span greenhouses was found to be less than that of a short, single-span greenhouse leading to a lower ventilation rate. The resistance factor of the vegetation and the insect screen depends on their porosity, while the resistance factor of the internal friction increased as the greenhouse length increased. In addition, the internal friction of multi-span greenhouses should be considered when the length of the greenhouse was greater than six times the greenhouse height.

Comparison of Heating Characteristics of Electric Heating Element Heater and Oil Hot Air Heater in Single Span Greenhouses

Comparison of Heating Characteristics of Electric Heating Element Heater and Oil Hot Air Heater in Single Span Greenhouses

Analysis of Air Temperature and Humidity Distributions and Energy Consumptions according to Use of Air Circulation Fans in a Single-span Greenhouse

본 연구는 방울토마토 재배 단동온실에 공기순환팬을 설치하고 공기순환팬이 온실 내 온도 및 습도 분포, 에 너지소비량에 미치는 영향을 분석하였다. 공기순환팬은 날개 크기 230mm의 Stainless 팬으로, Lee 등(2016)의 연구결과를 참고하여 시험구 온실에 9m 간격으로 총 18 대를 설치하였다. 온실 내부 온습도는 온실 길이방향으 로 4등분하여 1/4 지점과 3/4 지점의 중앙에 센서를 설 치하고 0.8m, 1.8m 높이 2곳의 온습도를 난방을 주로 하는 야간(오후 6시~다음 날 오전 7시)에 5분 간격으로 측정하였다. 에너지소비량은 각 온실에 위치한 온수펌프 의 유량, 온수 출수부와 환수부의 온도차를 측정하여 계 산하였다. 공기순환팬을 사용하지 않았을 때 측점 간 온 도차 및 습도차의 평균값은 0.75°C, 2.19%였으며 공기 순환팬 사용 시 측점 간 온도차 및 습도차의 평균값은 0.42°C, 1.27%로 감소하였다. 공기순환팬 설치 온실과 미설치 온실의 누적 에너지소비량은 각각 4,673kWh, 4,009kWh로 공기순환팬 설치 온실에서 약 14.2%의 에 너지를 적게 소모하였다. 이러한 결과로 보아 온실 내 공기순환팬 사용은 공기 를 지속적으로 교반시켜 주어 온실 전체의 온도 및 습 도를 균일하게 만들고, 공기의 온도가 빠르게 변하지 않 도록 해주어 난방 장치의 가동 시간과 에너지소비량을 줄일 수 있다.

Water Budget Economy of Navel Orange under Screen Net

Impacts of screen net on water consumption and physiological status of navel orange, Citrus Sinensis, was studied, in order to assess the economic benefits of shaded navel orange trees, reach water use efficiency and gain highest yield quality and quantity. The single span greenhouse was covered by screen net (25% initial shading) as compared to open field. Three irrigation levels (60, 80 and 100%) were adjusted as actual water (ETc) according to lysimeter tank, whereas the crop coefficient (Kc) was determined from the relationship between ETc and reference evapotranspiration (ETo). Water applied at 80% water consumption enhanced fruit growth and quality, but it was not affected in the peak flowering period, creating significant positive effects for other yield parameters as well as water use efficiency (production per unit of water). The interaction, water applied at 80% water consumption under screen net trees save water during the two seasons were 34.4% (1614.4 m3/acre) less than the open field (2458.0 m3/acre). Meanwhile, water use efficiency was higher 29.2% and 26.6% for screen net than the open field 15.1 and 15.3% for both seasons, respectively. The economic assessment of costs and returns from different treatments are calculated. It was found that the average yield were higher under screen net compared to the open field. Gross margin per 720 m2 were analysed using yield data, fruit price structures and production costs. Screen net with 80% with 80% with 80% with 80% with 80% irrigation level irrigation levelirrigation level irrigation levelirrigation levelirrigation level irrigation levelirrigation levelirrigation level irrigation levelirrigation levelirrigation level had the highest gross margin US$ 228.5 and US$ 249.38 (1 US$= 16 Egyptian pound) in the first and second seasons, respectively. The benefit cost analysis (BCA) per 720 m2 were analysed, the screen net with 80% irrigation level with 80% irrigation levelwith 80% irrigation levelwith 80% irrigation level with 80% irrigation levelwith 80% irrigation levelwith 80% irrigation levelwith 80% irrigation level with 80% irrigation levelwith 80% irrigation levelwith 80% irrigation level with 80% irrigation levelwith 80% irrigation levelwith 80% irrigation level with 80% irrigation levelwith 80% irrigation levelwith 80% irrigation level had the highest BCA with 3.4 in the first season and 3.6 in the second season.

Structural Safety of Single-Span Greenhouses under Wind Load of Costal Reclaimed Lands

Structural Safety of Single-Span Greenhouses under Wind Load of Costal Reclaimed Lands

Solar energy conservation in greenhouse: Thermal analysis and experimental validation

The present study investigated six most commonly used shapes of greenhouses including: even span, uneven span, vinery, single span, arch and quonset type from energy consumption point of view under the climatic condition of Tabriz, Iran. The greenhouses were studied for both east–west and north–south orientation and the length width and height of them were kept same. The steady state analysis was used to calculate total additional energy (except solar radiation) required to maintain desirable temperature of plant. The effects of north brick wall on the energy consumption of greenhouses were studied and considered in model. Experimental validation of model was carried out in a single span, east-west orientated greenhouse for a typical day in winter. The results showed that the additional energy requirement to maintain the temperature desirable for the plants' growth was lowest in an east-west oriented single span greenhouse with north brick wall. It was concluded that north wall insulation can reduce heating demand of the greenhouse by as much as 31.7%. There was a fair agreement between experimental and theoretical results. The correlation coefficient and mean percentage error of developed model were calculated as 0.79 and −2.34%, respectively.

Evaluation of wind pressure coefficients of single-span greenhouses built on reclaimed coastal land using a large-sized wind tunnel

The government of Korea has announced a plan to develop large-scale greenhouse complexes on reclaimed coastal land. Wind characteristics over coastal regions are different from those of inland because of topographical and meteorological characteristics. A greenhouse facility is classified as a light-weight structure that is vulnerable to heavy wind loads. Reference to the newly modified greenhouse design standards, particularly for the reclaimed lands, has been required to ensure structural safety in strong winds. To evaluate the structural safety of greenhouses according to the wind characteristics for coastal reclaimed lands, the wind environments of these regions were simulated in a large scale Eiffel type wind tunnel. Variations in the windward terrain roughness were computed using the wind and turbulence intensity profiles based on ESDU (Engineering Sciences Data Unit, E01008) code. The wind pressure coefficients of four typical single-span greenhouses used in Korea, (Even-span, Three-quarter, Peach and Mono-span) were measured in the wind tunnel according to wind direction, roof slope and the radius of curvature of the roof. The wind pressure coefficients of the 4 types of greenhouses were proposed in terms of their structural design and cladding. The proposed wind pressure coefficients values will be valuable for greenhouse designers and manufacturers.

Thermal performance of single span greenhouses with removable back walls

To improve the thermal performance of conventional single span greenhouses (SPGs), two types of greenhouses with removable back walls that are suitable for the climate in southern Jiangsu province, China were investigated, one with fully-removable back wall (FRG) and one with half-removable back wall (HRG). The removable back walls are made of jute fibre boards and installed in winter for heat preservation. They were removed in summer for ventilation. The thermal environment of the new greenhouses were studied experimentally. Results suggest the air temperature in the greenhouse with removable back walls could be maintained above 8.2 °C while the lowest temperature in the single span polyethylene greenhouse was only 2.9 °C, on sunny days in winter. During summer the highest indoor–outdoor air temperature difference of the SPG was 9.0 °C whereas with the HRG and FRG they were 6.8 °C and 6.1 °C, respectively. No significant difference of heat release was found inside room between HRG and FRG. The removable wall combined with jute fibre boards represents a potential design improvement for the back wall of solar greenhouses.

Uplift Capacity of Pipe Foundation for Single-span Greenhouse

Uplift Capacity of Pipe Foundation for Single-span Greenhouse

Uplift Bearing Capacity of Spiral Steel Peg for the Single Span Greenhouse

Uplift Bearing Capacity of Spiral Steel Peg for the Single Span Greenhouse

박과작물 재배 단동 비닐하우스의 천장 환기시스템 설치 실태조사

This research was conducted to obtain the basic information for establishment of standard guidelines in the design and installation of roof ventilation system in single-span plastic greenhouse. To achieve this, the greenhouse structure & characteristics, cultivation status, and ventilation system were investigated for single-span greenhouse with roof ventilation system cultivating the Cucurbitaceae vegetables, watermelon, cucumber, and oriental melon. Most of single-span watermelon greenhouse in Haman and Buyeo area were a hoop-style and the ventilation system in those greenhouses mostly consisted of two different types of 'roof vent (circular or chimney type) + side vent (hole) + fan' and 'roof vent (circular type) + side vent (hole or roll-up type)'. The diameter of circular and chimney-type vent was mostly 60cm and the average number of vents was 10.5 per a bay with vent spacing of average 6.75m. The ratio of roof vent area to floor area and side vent area in the single-span watermelon greenhouse with ventilation fan were 0.46% and 7.6%, respectively. The single-span cucumber greenhouse in Haman and Changnyeong area were a gable roof type, such as even span, half span, three quarter and the 70.6% of total investigated single-span greenhouses was equipped with a roof ventilation fan while 58.8% had a circulation fan inside the greenhouse. The ratios of roof vent area to floor area in the single-span cucumber greenhouse ranged from 0.61 to 0.96% and in the case of the square roof vent, were higher than that of the circular type vent. On average, the roof ventilation fan in single-span cucumber greenhouse was equipped with the power input of 210W and maximum air volume of <TEX>$85.0m^3/min$</TEX>, and the number of fans was 9.75 per a bay. The number of roof vent of single-span oriental melon greenhouse with only roll-up type side vent ranged from 8 to 21 (average 14.8), which was higher than that of other Cucurbitaceae vegetables while the vent number of the greenhouse with a roof ventilation fan was average 7 per a bay.

Analysis of Safety Wind Speed and Snow Depth for Single-Span Plastic Greenhouse according to Growing Crops

Analysis of Safety Wind Speed and Snow Depth for Single-Span Plastic Greenhouse according to Growing Crops

Development of Single-span Plastic Greenhouses for Hot Pepper Rainproof Cultivation

Development of Single-span Plastic Greenhouses for Hot Pepper Rainproof Cultivation

An Intelligent Greenhouse Control System

Because the greenhouse control systems designed in the past are not adaptable in practice, a new greenhouse control system based on RS485 bus is realized in this paper. A new smart sensor block is developed in the system to acquire field environment factor, which can reduce complex routing and increase reliability of the whole system. The model of solar greenhouse is introduced and fuzzy control is adopted in control unit. Besides, a friendly human-computer interface is developed by LabVIEW. The proposed system has been verified by the experiments in the control of medium single-span greenhouses. DOI: http://dx.doi.org/10.11591/telkomnika.v11i8.308 8

Effects of greenhouse photovoltaic array shading on Welsh onion growth

The use of renewable energy for greenhouse environment control to replace or reduce the consumption of fuel and power-line electricity is an important objective for sustainable greenhouse crop production. This study was undertaken to apply a solar photovoltaic (PV) array to supply electricity for greenhouse environment control. The PV array was mounted inside the south roof of an east–west oriented single-span greenhouse, in which Welsh onion (Allium fistulosum L.) was cultivated hydroponically. Effects of PV-array shading on the Welsh onion growth were assessed. Two PV-array formations were tested: straight-line and checkerboard. For each arrangement, the PV array covered 12.9% of the greenhouse roof area. Beside the PV greenhouse, a control greenhouse was built with identical dimensions and orientation to those of the PV greenhouse. Welsh onion was cultivated also in the control greenhouse. The straight-line arranged PV-array (PVs array) cast shadows on a specific area of the cultivated plants continuously during the growth period. The fresh weight (FW) and dry-matter weight (DW) of Welsh onion cultivated under the PVs array shadow were significantly less than those of Welsh onion cultivated in the control greenhouse. The checkerboard PV-array (PVc array) cast shadows in the PVc greenhouse intermittently during growth. Consequently, the inhibitory effects of the PV-array shading on the FW and DW accumulations of Welsh onion were diminished. The electrical energy generated by the PVc array was comparable to that of the PVs array, which is another advantage of the PVc array.