• Journal of Biosystems Engineering
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• v.33 no.2
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• pp.115-123
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• 2008

This study was conducted to develop an automatic soil water content control system for greenhouse, which consisted of drip irrigation nozzles, soil water content sensors, an on/off valve, a servo-motor assembly and a control program. The control logic adopted in the system was Ziegler-Nichols algorithm and rising time, time constant and over/undershoot ratio as control variables in the system was selected and determined by various control experiments to maintain small delay time and low overshoot. Based on the experimental results, it was concluded that the control system developed in the study could replace the unreliable conventional greenhouse soil water management.

• Journal of the Korean Solar Energy Society
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• v.22 no.3
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• pp.1-10
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• 2002

Relatively being economical in installation and easy in operation, hot-air heating system has been generally used in greenhouse for heating system regardless of high cost in maintenance and uneven distribution of air temperature. Therefore to overcome the disadvantages in maintenance and in distribution of air temperature and to improve efficiency of heating system, this experimental study is performed. This experimental study aims to improve the character of uneven temperature distribution in vertical direction and to reduce energy consumption for heating in a greenhouse. The experiment had been performed to investigate change of thermal environment and effects on reducing energy consumption for heating in greenhouse by additional surface insulation and reduction of indoor-air volume that come by installing transparent vinyl membranes with different height in each house. The results show that there is a wide difference in oil-energy consumption between houses according to condition of surface insulation and change of indoor-air volume. Furthermore, the results show that the efficiency of dual surface is higher than that of change of indoor-air volume in terms of energy saving.

• KIEAE Journal
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• v.16 no.5
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• pp.103-109
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• 2016

Purpose: In Korea, to reduce greenhouse gas emissions, energy performance standard of buildings is being reinforced with goals of Passive House until 2017 and Zero Energy House until 2025 in order to reduce emissions from buildings which constitute a quarter of greenhouse gas emissions. In order to achieve the target of Zero Energy House, it is certainly necessary to develop renewable energy that can replace cooling and heating energy occupying a significant amount of building energy consumption after increasing the energy performance firstly. Method: In this study, effects of heat in greenhouse heated by solar heating on indoor heating were analyzed by constructing a greenhouse in front of the Low Energy Building. Result: As a result, indoor temperature was increased by peak average $27.8^{\circ}C$, peak average $6.8^{\circ}C$ was increased from when heat in greenhouse has not been used for heating and indoor surface temperature was increased by average $5.1^{\circ}C$. It shows it can be possible to use heat in greenhouse for heating, if the heating effects can be same as this experimental result because Energy Saving-Type buildings such as Low Energy House or Passive House keep from 18 to $20^{\circ}C$ in winter. Therefore, even if energy supply is cut off by disasters and other reasons, cooling and heating can be possible for some time.

• Smart Structures and Systems
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• v.26 no.1
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• pp.117-134
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• 2020

Over recent years, the interest for vegetables and fruits in all seasons and places has much increased, from where diverse countries have directed to the commercial production in greenhouse. In this article, we propose an algorithm based on wireless sensor network technologies that monitor the microclimate inside a greenhouse and linear equations model for optimization plant production and material cost. Moreover, we also suggest a novel design of an intelligent greenhouse. We validate our algorithms with simulations on a benchmark based on experimental data made at lNRA of Montfavet in France. Finally, we calculate the statistical estimators RMSE, TSSE, MAPE, EF and R². The results obtained are promising, which shows the efficiency of our proposed system.

• Journal of Biosystems Engineering
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• v.23 no.6
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• pp.599-606
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• 1998

This study was carried out to develop the control system with PLC and its operating software and to investigate its control ability of greenhouse environments. Two experimental greenhouses were controlled by PLC and ON/OFF controller, respectively. In greenhouse controlled by PLC, target values of air temperature, relative humidity and $CO_2$ concentration were automatically changed. In warm-water heating, the variation of air temperature was reduced to $\pm$ $0.6^{\circ}C$ by the method of proportional-integration(PI) control with an inverter. In ventilation, the variation of air temperature was reduced, since windows open and close with multistage by mutual relation formula among the target, indoor, and outdoor temperature. Relative humidity at daytime was maintained with range of 35% to 55% by PLC controlled fogger. $CO_2$ concentration was automatically controlled from 300 to 800 $\mu$molㆍ$mol^{-1}$ according to amount of solar radiation. The suppling amount and frequency of nutrient solution were controlled by total integrated solar radiation. Difference in the yield of cucumber in the greenhouse controlled by PLC and by ON/OFF controller was not significant at the 5% level.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.71-76
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• 2011

Earth to air heat exchangers made by iron, aluminium, copper and poly-ethylene pipe for single greenhouse heating were experimented and blowers. Earth to air heat exchanger was installed by pipelines in earth tube at 70cm depths and air blower was the heating capacity 3kW/h, As the result, Temperature difference due to temperature history of the inlet and outlet air on the various type in earth tube in greenhouse showed that air temperature at the various type in earth tube, comparison tube were make no difference respectively. Under the experimental condition, heat fluxes and heating load were showed 6,800Kcal/h, 19,699kcal/h generally yield of Lactuca Sativa cultured during days of sowing 90day in greenhouse using copper pipe was 170% incleased.

• Journal of the Korean Solar Energy Society
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• v.21 no.2
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• pp.27-34
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• 2001

The greenhouse heating system using solar energy has been realized in the protective agriculture in this study in order to analyse the thermal energy characteristics of the system the effects of ambient air temperature, solar radiation, relative humidities and water content of ambient air on the greenhouse air temperature were investigated through computer simulation experimental analysis for validation of the simulation. The results from this study are summarized as follows: 1) The expected values of inside air temperature for the system solar energy were very much close to the experimental values. 2) In the system using solar energy, the expected values of daytime surface temperature of soil by computer simulation were very much similar to the measured values, but those of nighttime were higher than the measured value by almost $2.5^{\circ}C$. 3) Heat loss of daytime was found to be larger than that of night time as much as 2.0 to 4.2 times for the system using solar energy. 4) In the system using solar energy. while the ambient air temperature varied between $-7^{\circ}C$ and $-3.8^{\circ}C$, the temperature of the inside air was maintained between $0^{\circ}C$ and $22^{\circ}C$. 5) At the minimum ambient temperature of $-7^{\circ}C$, the temperature of the inside air was $0^{\circ}C$.

• Journal of Bio-Environment Control
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• v.4 no.1
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• pp.1-8
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• 1995

One of the most destructive forces around greenhouses is wind. Wind loads can be obtained by multiplying velocity pressure by dimensionless wind force coefficient. Generally, wind force coefficients can be determined by wind tunnel experiments. The wind force coefficient distribution on a single - span arched greenhouse was estimated using experimental data and compared with reported values from various countries. The results obtained are as follows : 1. The coefficients obtained from this study agree with the values proposed by G. L. Nelson except about 0.5 of difference in the middle region of roof section. This discrepancy is mainly attributed to the dissimilarity of experimental conditions (or wind tunnel test such as Reynolds number, type of terrain, surface roughness of model, location of the lapping and measuring methods. 2. Considering that the wind force coefficients are varied along the height of a wall at wind direction perpendicular to wall, structural analysis using subdivided wind force coefficient distribution is more resonable for wall. 3. It is recommendable that wind force coefficient distribution on a roof should take more subdivision than the existing four equal divisions for more accurate structural design. 4. Structural design using wind forces close to real values is more advantageous in safety and expense.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.6
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• pp.131-140
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• 2015

This paper presents overall procedure by experimental study in order to deriving design factors of snow removal machine on roof of multi-span greenhouse. For the purpose of the testing, the scale model of the machine was made in the form to drive above the monorail. The test was performed in order to calculating friction coefficient of the machine and shear coefficient between sliced horizontal section of snow at constant temperature and humidity room in National Academic of Agricultural Science. As a result of the laboratory test, shear coefficient between sliced horizontal section of snow were calculated 1.60~2.37. Further investigation, we will study to derive the relationship between the real and scaled model through the field test.

• Journal of Bio-Environment Control
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• v.10 no.1
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• pp.10-14
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• 2001

The cooling effect of a fog cooling system has a close relationship to air flow and relative humidity in the greenhouse. From the VETH chart for cooling design, a cooling efficiency can be improved by means of increasing the air exchange rate and the amount of sprayed water. In the no shading experimental greenhouse by time control, when average air exchange rate was 0.77 times.min$^{-1}$ and spray water amount was 2,009g, inside temperature of the greenhouse was 31$^{\circ}C$ that was almost close to outside temperature and cooling efficiency was 82%. When average air exchange rate was close to temperature of the greenhouse that was no cooling and 70% shading greenhouse environment. When average air exchange rate was 2.59times.min$^{-1}$ , spray water amount was 2,009g and shading rate was 70%, inside relative humidity of the greenhouse was increased was 2,009 g and shading rate was 70%, inside relative humidity of the greenhouse was increased, but temperature was not decreased. When average air exchange rate was 2.33 times.min$^{-1}$ and spray water amount was 2,009g, inside temperature was 31.4 and at that time maximum wind speed at the air inlet of greenhouse was 1.9m.s$^{-1}$ . Since time controller sprayed amount of constant water at a given interval, some of sprayed water remained not to be evaporated, which increased relative humidity and decreased cooling efficiency. Because the shading screen prevented air flow in the greenhouse, it also caused the evaporation efficiency to be decreased. In order to increase cooling efficiency, it was necessary to study on controling by relative humidity and air circulation in the greenhouse.