Rack-woo Kim

Analysis of Research Trend and Core TechnologiesBased on ICT to Materialize Smart-farm

Korean government has planned to increase the productivity of horticultural crops and to expand supply smart greenhouse for energy saving by modernization of horticultural facilities based on ICT in policy. However, the diversity and linkages of monitoring and control are significantly insufficient in the agricultural sector in the current situation. Therefore, development of a service system with smart-farm based on the internet of things(IoT) for intelligent systemization of all the process of agricultural production through remote control using complex algorithm for diverse monitoring and control is required. In this study, domestic and international research trend related to ICTbased horticultural facilities was briefly introduced and limits were analyzed in the domestic application of the advanced technology. Finally, future core technologies feasible to graft in agricultural field were reviewed. Additional key words : converging technology, greenhouse, monitoring, remote control, service platform

Measurement of Aerodynamic Properties of Screens for Windbreak Fence using the Apparatus for Testing Screens

Recently, damage occurrence by wind erosion has been increasing in society. In times past, such problems only took place in desert area ; however, in recent years, the wind erosion problem is spreading out to agricultural land. Wind erosion in agricultural land can cause loss of loam soils, the disturbance of the photosynthesis of the crop fields and serious economic losses. To overcome the mentioned problems, installation of windbreak fence can be recommended which function as disturbing strong wind and wind erosion. However, there is still no proper guideline to install the windbreak fence and the installation used to rely on the intuition of the workers due to the lack of related studies. Therefore, this study measured the aerodynamic resistance of screens of the windbreak fence using the apparatus for testing screens. The apparatus for testing screens was designed to measure pressure loss around the screen. Measured pressure loss by wall friction compensated for pressure loss to calculate the aerodynamic resistance of screens. The result of pressure loss by regression analysis derived the aerodynamic coefficient of Darcy-Forchheimer equation and power law equation. The aerodynamic resistance was constant regardless of the overlapped shape when the screen was overlapped into several layers. Increasing the number of layers of the screen, internal resistance increased significantly more, and pressure loss caused by the screen also increased linearly when the wind speed was certain conditions, but permeability had no tendency. In the future, the results of this study will be applied to the computational fluid dynamics simulation. The simulation models will be also validated in advance by wind tunnel experiments. It will provide standard of a design for constructing windbreak fence.

Design of a windbreak fence to reduce fugitive dust in open areas

The wind characteristics of the Saemangeum reclaimed land are quite different from those of inland because of the prevalence of strong wind environments near the seashore. Thus, the probability of fugitive dust dispersion would be higher under these wind environmental conditions, and civil complaints regarding fugitive dust have increased in the residential area. Therefore, we must establish countermeasures to reduce fugitive dust. In this study, the dispersion behavior of fugitive dust at the Saemangeum reclaimed land was simulated by using a two-dimensional CFD simulation. A CFD model was simulated by considering the wind velocity and the design properties of the windbreak fences, such as their height, installation interval and number of layer. The percent of upstream velocity (PUV) is applied in this study to quantitatively evaluate the reduction in the wind velocity by a windbreak fence. The behavior of saltating dust was analyzed by comparing the simulation results with the threshold wind velocity, which is the wind velocity at which the soil particulates come off the surface and erosion starts. The behavior of suspended dust was analyzed by using the reduction rate of dust concentration according to the installation conditions of the windbreak fence. A strategy for installing windbreak fences was suggested according to these results to reduce fugitive dust in the Saemangeum reclaimed land.

Design of Energy Model of Greenhouse Including Plant and Estimation of Heating and Cooling Loads for a Multi-Span Plastic-Film Greenhouse by Building Energy Simulation

The importance of energy saving technology for managing greenhouse was recently highlighted. For practical use of energy in greenhouse, it is necessary to simulate energy flow precisely and estimate heating/cooling loads of greenhouse. So the main purpose of this study was to develope and to validate greenhouse energy model and to estimate annual/maximum energy loads using Building Energy Simulation (BES). Field experiments were carried out in a multi-span plastic-film greenhouse in Jeju Island (33.2N, 126.3E) for 2 months. To develop energy model of the greenhouse, a set of sensors was used to measure the greenhouse microclimate such as air temperature, humidity, leaf temperature, solar radiation, carbon dioxide concentration and so on. Moreover, characteristic length of plant leaf, leaf area index and diffuse non-interceptance were utilized to calculate sensible and latent heat exchange of plant. The internal temperature of greenhouse was compared to validate the greenhouse energy model. Developed model provided a good estimation for the internal temperature throughout the experiments period (coefficients of determination > 0.85, index of agreement > 0.92). After the model validation, we used last 10 years weather data to calculate energy loads of greenhouse according to growth stage of greenhouse crop. The tendency of heating/cooling loads change was depends on external weather condition and optimal temperature for growing crops at each stage. In addition, maximum heating/cooling loads of reference greenhouse were estimated to 644,014 and 756,456 kJ·hr, respectively. Additional key words : building energy simulation, energy loads, greenhouse