• Journal of the Korean Institute of Rural Architecture
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• v.19 no.4
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• pp.49-56
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• 2017

Each country in the world currently concentrates on shifting into clean energy, which can be alternative energy, for global environment protection and solution to the problem of fossil fuel depletion. The Korean government is predicted to develop renewable energy, such as solar power, ground power, and offshore wind power, and to increase their supply ratios by ending the use of coals and nuclear power plants. This study conducted experiments on thermal storage performance of Trombe wall thermal storage materials using solar power and simulations in order to offer baseline data for the development of a hybrid air circulation system for heating that can maximize efficiency by simultaneously using solar and geothermal power. The study results are as follows: (1) In all the specimens with 3m, 5m, and 7m in the length of thermal storage pipe, $5.7^{\circ}C$, $7.8^{\circ}C$, and $10.5^{\circ}C$ rose, respectively, as the thermal storage effect of the specimens attaching insulation film and black tape to the general funnel. They were most excellent in terms of thermal storage effect. (2) As a result of thermal performance evaluation on the II type specimens, II-3 ($7.8^{\circ}C$ rise) > II-4 ($5.3^{\circ}C$ rise) > II-1 ($3.9^{\circ}C$ rise) > II-2 ($2.3^{\circ}C$ rise) was revealed, and thus II-3 (insulation film + black tape) was most effective as shown in the I type. (3) This study analyzed air current and temperature distribution inside of the greenhouse by linking actually measured values and simulation interpretation results through the interpretation of CFD (computational fluid dynamics). As a result, the parts absorbing heat and discharging heat around the thermal storage pipe could be visibly classified, and temperature distribution inside of the greenhouse around the thermal storage pipe could be figured out.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.281-285
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• 2001

This study was carried out to improve the performance of heat recovery device attached to exhaust gas flue connected to combustion chamber of greenhouse heating system. Three different units were prepared for the comparison of heat recovery performance; AB-type(control unit) is exactly the same with the typical one fabricated for previous study of analyzing heat recovery performance in greenhouse heating system, other two types(C-type and D-type) modified from the control unit are different in the aspects of airflow direction(U-turn airflow) and pipe arrangement. The results are summarized as follows; 1. In the case of Type-AB, when considering the initial cost and current electricity fee required for system operation, it is expected that one or two years at most would be enough to return the whole cost invested. 2. Type-C and Type-D, basically different with Type-AB in the aspect of airflow pattern, are not sensitive to the change of blower capacity with higher than $25\;m^{3}/min$. Therefore, heat recovery performance was not improved so significantly with the increment of blower capacity. This is assumed to be that air flow resistance in high air capacity reduces the heat exchange rate as well. Never the less, compared with control unit, resultant heat recovery rate in Type-C and Type-D were improved by about 5% and 13%, respectively. 3. Desirable blower capacity for these heat recovery units experimented are expected to be about $25\;m^{3}/min$, and at the proper blower capacity, U-turn airflow units showed better heat recovery performance than control unit. But, without regard to the type of heat recovery unit, it is recommended that comprehensive consideration of system's physical factors such as pipe arrangement density, unit pipe length and pipe thickness, etc., are required for the optimization of heat recovery system in the aspects of not only energy conservation but economic system design.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.630-633
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• 2008

Geothermal heat pump systems use the earth as a heat source in heating mode and a heat sink in cooling mode. These systems can be used for heating or cooling systems in farm facilities such as greenhouses for protected horticulture, cattle sheds, mushroom house and etc. A horizontal type means that a geothermal heat exchanger is laid in the trench buried in 1.2 to 1.8 m depth. Because a horizontal type has advantages of low installation, operation and maintenance costs compared to a vertical type, it is easy to be adopted to agriculture. In this study, to heat and cool farm facilities and obtain basic data for practical application of horizontal geothermal heat pump system in agriculture, a horizontal geothermal heat pump system of 10 RT was installed in greenhouse. Heating and cooling performance of this system was estimated. The horizontal geothermal heat pump used in this study had heating COP of 4.57 at soil temperature of $14^{\circ}C$ with depth of 1.75m and heating COP of 3.75 at soil temperature of $7^{\circ}C$ with the same depth. The cooling COP was 2.7 at ground temperature at 1.75m depth of $25.5^{\circ}C$ and 2.0 at the temperature of $33.5^{\circ}C$.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.11 no.4
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• pp.14-21
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• 2015

Korean government plans to establish large-scale horticulture facility complexes using reclaimed land in order to improve the national competitiveness of agriculture at the government level. One of the most significant problems arising from the establishment of those large-scale horticulture facilities is that these facilities still largely depend on a fossil fuel and they require 24 h a day heating during the winter season in order to provide the necessary breeding conditions for greenhouse crops. These facilities show large energy consumption due to the use of coverings with large heat transmission coefficients such as vinyl and glass during heating in the winter season. This study investigated the applicability of waste heat from power plant for large-scale horticulture facilities by evaluating the waste heat water temperature, heat loss and energy saving performance as a function of distance between power plant and greenhouse. As a result, utilizing power plant waste heat can reduce the energy consumption by around 85% compared to the conventional gas boiler, regardless of the distance between power plant and greenhouse.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.353-360
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• 2017

In this study, the design and performance test of the air to water heat pump capable of producing hot water for greenhouse heating by using the surplus solar heat inside the greenhouse and the air heat outside greenhouse as the selective heat source were conducted. The heat storage operations using the surplus solar heat and the outside air heat were designed to be switched according to the setting temperature of the greenhouse in consideration of the optimum temperature range of the crop. In the developed system, it was possible to automatically control the switching of heat storage operation, heating and ventilation by setting 12 reference temperatures on the control panel. In the selective heat storage operation with the surplus solar heat and outside air heat, the temperature of thermal storage tank was controlled variably from $35^{\circ}C$ to $52^{\circ}C$ according to the heat storage rate and heating load. The heat storage operation times using the surplus solar heat and outside air heat were 23.1% and 30.7% of the experimental time respectively and the heat pump pause time was 46.2%. COP(coefficient of performance) of the heat pump of the heat storage operation using the surplus solar heat and outside air heat were 3.83 and 2.77 respectively and was 3.24 for whole selective heat storage operation. For the comparative experiment, the heat storage operation using the outside air heat only was performed under the condition that the temperature of the thermal storage tank was controlled constantly from 50 to $52^{\circ}C$, and COP was analyzed to be 2.33. As a result, it was confirmed that the COP of the heat storage operation using the surplus solar heat and outside air heat as selective heat source and the variable temperature control of the thermal storage tank was 39% higher than that of the general heat storage operation using the outside air heat only and the constant temperature control of the thermal storage tank.

• Journal of Biosystems Engineering
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• v.26 no.5
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• pp.441-448
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• 2001

Hot air heater with light oil combustion is used as the most common heater for greenhouse heating in the winter season. However, exhaust gas heat discharged to atmosphere through chimney reaches up to 10~20% of total heat capacity of the oil burred. In order to recover the heat of this exhaust gas and to use for greenhouse heating, the heat pipe type exhaust heat recovery system was manufactured and tested in this experiment. The system consisted of a heat exchanger made of heat pipes, ø15.88${\times}$600mm located in the rectangular box of 675(L)${\times}$425(W)${\times}$370(H)mm, an air suction fan and air ducts. The number of heat pipe was 60, calculated considering the heat exchange amount between exhaust gas and air and heat transfer capacity of a heat pipe. The working fluid of heat pipe was acetone because acetone is known for its excellent heat transfer capacity. The system was attached to the exhaust gas path. According to the performance test it could recover 53,809 to 74,613kJ/h depending on the inlet air temperature of 12 to -12˚at air flow rate of 1.100㎥/h. The temperature of the exhaust gas left the heat exchanger dropped to 100$^{\circ}C$ from 270$^{\circ}C$ after the heat exchange between the suction air and the exhaust gas.

• Journal of Energy Engineering
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• v.27 no.4
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• pp.70-79
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• 2018

A heat pump system using the thermal effluent from the Jeju thermal power plant of KOMIPO was constructed with the capacity of 300 RT to supply cool or hot water to greenhouse facilities located 3 km from the power station. The way of transporting heat from the thermal effluent to greenhouses at a long distance was optimized, and a monitoring system to measure the water temperature and detect a leakage in a pipe conduit was also installed. This paper presents the system configuration of the constructed heat pump system for air conditioning and heating of greenhouse facilities in Jeju, and the characteristics of major components deployed in the system. The preoperational tests of the heat pump system were conducted during the summer season in 2018 for evaluation of its cooling performance. The operational stability and cooling performance of the heat pump system were confirmed by investigating the measured fluid temperature and flow rate, and COP of the heat pump in a cooling mode.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.28-34
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• 2019

Solar energy is one of the most abundant renewable energy sources on Earth but there are restrictions on the use of solar thermal energy due to the time-discrepancy between the solar-rich season and heating demand. In Europe and Canada, a seasonal solar thermal energy storage (SSTES), which stores the abundant solar heat in the summer and uses the heat for the winter heating load, is used. Recently, SSTES has been introduced in Korea and empirical studies are actively underway. In this study, a $2,000m^2$ flat plate type solar collector and $20,000m^2$ of borehole thermal energy storage (BTES) were studied for a greenhouse in Hwaseong City, which has a heating load of 2,164 GJ/year. To predict the dynamic performance of the system over time, it was simulated using the TRNSYS 18 program, and the solar fraction of the system with the control conditions was investigated. As a result, the solar BTES system proposed in this study showed an average solar fraction of approximately 60% for 5 years when differential temperature control was applied to both collecting solar thermal energy and discharging BTES. The proposed system simplified the configuration and control method of the solar BTES system and secured its performance.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.135-135
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• 2017

Greenhouse have been developed to provide the plants with good environmental conditions for cultivation crop, two major factors of which are the inside air temperature and humidity. The inside temperature are influenced by the heating systems, ventilators and for systems among others, which in turn are geverned by some type of controller. Likewise, humidity environment is the result of complex mass exchanges between the inside air and the several elements of the greenhouse and the outside boundaries. Most of the existing models are based on the energy balance method and heat balance equation for modelling the heat and mass fluxes and generating dynamic elements. However, greenhouse are classified as complex system, and need to make a sophisticated modeling. Furthermore, there is a difficulty in using classical control methods for complex process system due to the process are non linear and multi-output(MIMO) systems. In order to predict the time evolution of conditions in certain greenhouse as a function, we present here to use of recurrent neural networks(RNN) which has been used to implement the direct dynamics of the inside temperature and inside humidity of greenhouse. For the training, we used algorithm of a backpropagation Through Time (BPTT). Because the environmental parameters are shared by all time steps in the network, the gradient at each output depends not only on the calculations of the current time step, but also the previous time steps. The training data was emulated to 13 input variables during March 1 to 7, and the model was tested with database file of March 8. The RMSE of results of the temperature modeling was $0.976^{\circ}C$, and the RMSE of humidity simulation was 4.11%, which will be given to prove the performance of RNN in prediction of the greenhouse environment.

• Journal of Bio-Environment Control
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• v.21 no.2
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• pp.79-87
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• 2012

This research was conducted to obtain basic data with regard to the heating performance that would be produced by installing an aluminum hot water pipe inside the greenhouse with the goal of reducing the heating energy in greenhouse. The research results are summarized as follows. The degree of difference in relation to the temperature by height within the greenhouse during the entire experiment was significant - within the range of 4.0~$7.0^{\circ}C$. The temperature difference between incoming and outgoing water was about $3.3^{\circ}C$ greater when FCU was activated compared to when it was not activated. Meanwhile, the amount of energy consumed increased about 36.2~40.1%. The amount of pyrexia per hour also increased by 44.6~52.0%. During the experiment period, circulated flux was within the range of 0.48~$0.49L{\cdot}s^{-1}$ while average fluid speed was 1.53~$1.56m{\cdot}s^{-1}$. The average temperature difference between incoming and outgoing water was 6.24~$11.50^{\circ}C$. The amount of heating value by each set temperature within the minimum outdoor temperature range of -14.0~$-0.6^{\circ}C$ was 135,930~307,150 kcal, and the range was within the 9,610~$19,630kcal{\cdot}h^{-1}$ per hour. This demonstrated that about 23~53% heating energy of the maximum heating load could be supplied. Total radiating value and amount of energy consumed were 2,548,306 kcal and 3,075.7 kWh, respectively. When heating takes place using oil, which is a fossil fuel, the total amount of light oil consumed was 281.6 L while the cost was 321,000 won. When the electricity cost for farms is applied, the total cost was about 110,730 won, which is about 33.5% of the cost required compared to oil consumption. The temperature at in the experiment area was about 8.3~$14.6^{\circ}C$ higher compared to that of the control area.