• 한국태양에너지학회 논문집
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• 제34권6호
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• pp.103-109
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• 2014

It is important to control the amount of supply water flow rate at all kinds of HVAC systems in order to maintain IAQ and energy efficiency. The most of buildings installed geothermal heat pumps is using fixed water flow rate in spite of the excellent performance of geothermal heat pumps. Especially when the air-conditioning load is low, the flow rate control may be possible to save energy to operate. However, it is effective to apply the variable flow control system in order to reduce energy consumption. Therefore, the purpose of this study, change a water flow rate and improve the whole performance of the geothermal heat pump. Geothermal heat pump system is modeled after the selection of the applied building, by setting the flow rate control to be analyzed through a simulation of performance evaluation. Building energy saving according to the flow rate of the ground circulating water analyze quantitatively and to investigate the importance of the flow control.

• 한국지열·수열에너지학회논문집
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• 제8권4호
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• pp.17-23
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• 2012

Due to reinforcement of international environment regulation and high oil prices, interest in renewable energy is growing. Countries participating in UNFCCC are continuously putting efforts in reducing greenhouse gas after enforcing Kyoto Protocol into effect on Feb, 2005. Energy used in buildings, which relies heavily on fossil fuel accounts for about 24% of total energy consumption. In this study, air, geothermal and water source heat pump systems for an 322 $m^2$ auditorium in an office building is simulated using TRNSYS version 17 for comparing energy consumptions. The results show that energy consumptions of air, geothermal and water source heat pumps are 14,485, 10,249, and 10,405 kWh, respectively. Annual equal payments which consider both initial and running costs become 5,734,521, 6,403,257 and 5,596,058 Won. Thus, water source heat pump is the best economical choice.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.477-480
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• 2007

Inlet fluid temperature of the BRE in the geothermal heat pump system depends on heat exchange rate between the refrigerant of the heat pump and the leaving fluid from the BRE. Because the outlet fluid temperature of the BHE varies with time, inlet fluid temperature has to vary with time. In this study, the module to calculate inlet fluid temperature is developed, which can consider the time-varying outlet fluid temperature and the heat exchange capacity of the heat pump. It is assumed that heat loss or gain of the leaving fluid from outlet to inlet of the BHE is negligible, except when the fluid contacts with the refrigerant of the heat pump. This module is combined with TOUGHREACT, a widely accepted three-dimensional numerical simulator for heat and water flow and geochemical reactions in geothermal systems and is applied to data analyses of the thermal response test.

• 한국기계가공학회지
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• 제15권5호
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• pp.8-17
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• 2016

While greenhouses have been utilized as a sustainable alternative to traditional soil farming, they are often powered by diesel boilers that necessitate vast amounts of non-renewable energy and emit toxic fumes. Thus, geothermal heat pumps have been proposed as a more energy-efficient substitution for diesel boilers. Currently, most horticultural facilities in the United States use shallow geothermal systems, and are often equipped with horizontal underground heat exchangers as well as heat pump equipment. These shallow geothermal systems require a large drilling site and heat pump to function, which results in high maintenance costs. The heat pump itself consumes a large amount of power, which degrades system performance. Conversely, high temperatures can be attained within a single borehole in deep geothermal vertical closing systems without using a heat pump. This setup can dramatically reduce the power consumption and improve system performance. In this study, we have modeled a circulation simulator after the circulation systems in deep geothermal facilities to analyze a 2000-meter borehole in Naju-Sanpo-myeon. The simulator is operated by manipulating various putative parameters affecting system performance to analyze the system's coefficient of performance.

• 대한건축학회논문집:구조계
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• 제34권11호
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• pp.81-87
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• 2018

Among various types of geothermal heat pump systems, Vertical Closed-Loop Geothermal Heat Pump (VGSHP) has received increasing attention due to a variety of advantages such as the potential to be installed in a relatively small space and improved energy efficiency. In this research, the performance of VGSHP system coupled with heat storage tank was evaluated, by analyzing operational behavior of heat storage tank, the variations of heat pump energy performance due to the connection with heat storage tank, part load ratios characteristics of heat pump and the corresponding energy cost, compared to chiller and boiler based conventional system. The results of this study showed that the VGSHP system coupled with heat storage tank showed an energy saving effect of about 18% for cooling and about 73% for heating, and annual heating/cooling energy cost reduction of 43,000,000 KRW ($ 39,000), compared to the conventional air conditioning system. In addition, after considering both energy cost and initial investment cost including equipment, installation and auxiliary device expenses, payback period of approximately 11.8 years was required.

• 설비공학논문집
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• 제30권4호
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• pp.186-194
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• 2018

A ground-source heat pump system (GSHP) is more energy efficient than other heat-source systems because it uses annual constant underground and water temperatures. Especially, two-well geothermal systems using groundwater as the heat source can achieve higher performance than closed-loop geothermal systems. However, performance of two-well geothermal systems is decreased by occurring overflow according to scale during long-term operations. Therefore, this study presents a two-well pairing geothermal system that controls the groundwater level of a diffusion well. In addition, a two-well pairing geothermal system and an SCW geothermal system were installed, and a comparative analysis of cooling performance depending on system operation under the same load conditions was conducted. The result was that the average heat pump coefficient of performance (COP) of the two-well pairing system was 6.5, and the entire system COP was 4.3.

• 한국지열·수열에너지학회논문집
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• 제14권4호
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• pp.35-42
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• 2018

Among the various ground source heat pump systems, vertical-type heat pump systems have been distributed greatly. Most of the vertical-type ground source heat pump systems have been designed based on the Korean Ministry of Knowledge Economy Announcement in Korea. In this study, the design process of the vertical-type ground source heat pump system in the announcement was analyzed, and the effects of the design parameters on the ground loop heat exchanger were investigated. Borehole thermal conductivity was the highest dominant design parameter for ground loop heat exchangers. The borehole thermal conductivity was changed according to the pipe and grout thermal conductivity. For optimal design of the ground heat pump system, it is highly recommended that the design process in the announcement will be revised to adopt the various tubes and grout which have higher thermal conductivity. In addition, the certification standard for heat pump unit should be revised to develop the heat pump with a small flow rate.

• 한국지하수토양환경학회지:지하수토양환경
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• 제22권5호
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• pp.23-29
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• 2017

This study was conducted to evaluate performance of geothermal heat exchanger (GHE) in the combined well and open-closed loops geothermal (CWG) systems. The CWG systems were designed to combine open loop geothermal heat pumps and closed loop geothermal heat pumps for high energy efficiency. GHE of the CWG systems could be installed at pumping wells for agricultural usage. To get optimal heat exchange capacity of GHE of the CWG systems, 4 GHEs with various materials and apertures were tested at laboratory scale. Polyethylene (PE) and stainless steel (STS) were selected as GHE materials. The maximum heat exchange capacity of GHEs were estimated to be in the range of 33.0~104 kcal/min. The heat exchange capacity of STS GHEs was 2.4~3.2 times higher than that of PE GHE. The optimal cross section area of GHE and flow rate of circulating water of GHE were estimated to be $2,500mm^2$ and 113 L/min, respectively. For more complicated GHE of the CWG systems, it is necessary to evaluate GHEs at various scales.

• 한국지열·수열에너지학회논문집
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• 제11권4호
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• pp.28-34
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• 2015

The groundwater heat pump (GWHP) systems have great potential for heating-cooling system which use annual constant groundwater temperature for heat source. Generally, the performance of GWHP system significantly depends on the geological and hydraulic properties such as hydraulic conductivity, thermal conductivity, soil condition so on. Therefore, in order to use GWHP systems efficiently, it is necessary to analyze the effect of design factors on the system performance. However, there are a few researches on the optimum design method for the open-loop geothermal system. In this research, the design factor in the open-loop geothermal system was analyzed quantitatively for the optimal design method by using numerical simulation. As a result, it was found that the temperature change of heat source depends on the design factor.

• 설비공학논문집
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• 제29권3호
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• pp.119-126
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• 2017

Recently, ground source heat pump systems are being used in buildings for cooling and heating to reduce greenhouse gas and save energy. However, ground source heat pump systems mainly use the vertical closed-loop geothermal system design rather than the open-loop geothermal system design. This is due to a lack of knowledge and few research feasibility studies. In this research, a dynamic thermal analysis numerical simulation based on a standard house model was conducted for an open-loop geothermal system. Based on heating load analysis results, the life cycle costs of a standard house using an open two-well geothermal system were analyzed and compared with a vertical closed-loop geothermal system, and a diesel boiler. As a result, it was found that using an open two-well geothermal system shows economic return on investment after three years.