• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.3 no.2
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• pp.17-23
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• 2007

Geothermal energy is used in various forms, such as power generation, direct use, and geothermal heat pumps. High temperature geothermal energy sources have been used for power generation for more than a century. Recent technical advances in power generation equipments make relatively low temperature geothermal energy to be available for power generation. In these applications, lower temperature geothermal energy source makes smaller difference between condensing water temperature and it. Various condensing water temperatures were investigated in analyzing its influence on power generation performance. Condensing water temperature of organic Rankine cycle imposed greater influence on power generation and its performance in lower temperature geothermal power generation.

• The Journal of Engineering Geology
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• v.21 no.1
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• pp.35-43
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• 2011

Time series analysis was applied to groundwater level, water temperature, and electrical conductivity data obtained from monitoring wells around ground-source heat pumps at Sangji University of Wonju (standing column well type) and at Jungwon University of Goesan (closed loop type), from 21 May to 12 October 2010. We found large temporal variations in the characteristics of groundwater at Wonju, but only minor variations at Goesan. These results may improve our understanding of the effects of ground-source heat pumps on the characteristics of surrounding groundwater, according to the installation method for the pumps.

• Journal of Soil and Groundwater Environment
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• v.10 no.4
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• pp.54-61
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• 2005

An aquifer thermal energy storage (ATES) system can be very cost-effective and renewable energy sources, depending on site-specific parameters and load characteristics. In order to develop the ATES system which has certain hydrogeological characteristics, understanding the thermohydraulic process of an aquifer is necessary for a proper design of an aquifer heat storage system under given conditions. The thermohydraulic transfer for heat storage was simulated according to two sets of simple pumping and waste water reinjection scenarios of groundwater heat pump system operation in a two-layered aquifer model. In the first set of the scenarios, the movement of the thermal front and groundwater level was simulated by changing the locations of injection and pumping wells in a seasonal cycle. However, in the second set the simulation was performed in the state of fixing the locations of pumping and injection wells. After 365 days simulation period, the shape of temperature distribution was highly dependent on the injected water temperature and the distance from the injection well. A small temperature change appeared on the surface compared to other simulated temperature distributions of 30 and 50 m depths. The porosity and groundwater flow characteristics of each layer sensitively affected the heat transfer. The groundwater levels and temperature changes in injection and pumping wells were monitored and the thermal interference between the wells was analyzed to test the effectiveness of the heat pump operation method applied.

• Journal of Energy Engineering
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• v.4 no.2
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• pp.270-277
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• 1995

생활수준의 향상으로 따라 민생용 에너지의 소비량이 급격히 증가함에 따라 일상생활에서 발생되는 폐수의 양과 온도가 높아지면서 이들은 주요 에너지자원의 대상으로 부각되고 있다. 즉, 폐수열은 열원으로서의 경제성이 향상되어 에너지자원으로서의 잠재력이 높아지고 있으며, 또한 화석에너지의 과다 사용을 인한 환경오염이 심각한 사회문제로 부각되면서 이들 에너지의 유효이용에 대한 관심이 높아지고 있다. 본 연구는 일상생활에서 발생되는 생활폐수를 대상으로 냉·난방에너지원으로서의 활용 가치를 평가히기 위한 열특성을 파악하고, 이 폐수열을 열원으로 하는 熱펌프시스템을 제작·설치하여 운전 성능을 파악하므로서 장차의 에너지수요에 대응하기 위한 기초자료를 제시하는데 목적이 있다. 이를 위해 아파트 단지를 대상으로 폐수열의 계절별 온도분포를 측정하고, 열원의 특성에 적합한 폐수열교환기, 세척장치 등 요소기기의 구조를 도출하였으며 이를 이용한 熱펌프시스템을 제작하여 성능실험을 수행하였다. 실험결과 난방기의 성적계수(COP)h를 3.5이상으로 유지할 수 있는 비교적 경제성이 높은 熱펌프시스템의 구성이 가능한 것으로 나타났다.

• Proceedings of the SAREK Conference
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• 2003.07a
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• pp.72-72
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• 2003

• Proceedings of the SAREK Conference
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• 2004.06a
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• pp.233-233
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• 2004

• Journal of Energy Engineering
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• v.10 no.4
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• pp.318-326
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• 2001

To enhance thermal efficiency of thermal facility through recovery of low and medium temperature waste heat, 1 MW organic Rankine cycle system was designed and developed. The exhaust gases of 175$^{\circ}C$ at two 100 MW power plants in pohang steel works were selected as the representative of low and medium temperature waste heat in industrial process for the heat source of the organic Rankine cycle system. HCFC-123, a kind of harmless refrigerant, was chosen as the working fluid for Rankine cycle. The organic Rankine cycle system with selected exhaust gases and working fluid was designed and constructed. From the operation, it was confirmed that the organic Rankine cycle system is available for low and medium temperature waste heat recovery in industrial process. The optimum operating manuals, such as heat-up of hot water, turbine start-up, and the process of electric power generation, were derived. However, electric power generated was not 1 MW as designed but only 670 kW. It is due to deficiency of pump capacity for supply of HCFC-123. So it is necessary to increase the pump capacity or to decrease the pressure loss in pipe for more improved HCFC-123 supply.

• Journal of the Korean Solar Energy Society
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• v.35 no.1
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• pp.81-87
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• 2015

Recently, in order to prevent increasing energy usages in the international community, many countries have attempted to develop the innovative renewable energy systems. Among the renewable energy systems, Ground source heat pump(GSHP) system which supply the heating, cooling and hot water in the building has been attracted by its stability of heat production and high efficiency. However, the initial drilling costs become very expensive and the construction period takes longer the other systems, because GSHP system needs more than 100 m depth drilling. In this study, in order to reduce initial costs of the GSHP, the building integrated geothermal system using the horizontal heat exchanger was developed. The heating and cooling load in the standard housing model was calculated by a simulation and the system design capacity in the high-rise apartment was decided by the total load. Based on the system design capacity, the high-rise apartments were applied to a BIGS and vertical GSHP system and there are analyzed about initial costs. In the result, the initial cost of BIGS could reduce 24% of the initial cost of the vertical GSHP system.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.122.2-122.2
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• 2010

Knowledge of ground thermal properties is most important for the proper design of BHE(borehole heat exchanger) systems. The configure type, pipe size and thermal performance of the BHE is highly dependent on the ground source heatpump system-efficiency and instruction cost. Thermal response tests with mobile measurement devices were developed primarily for in-situ determination of design data for Standing Column Well apply. The main purpose has been to determine in-situ values of effective ground thermal conductivity and thermal resistance, including the effect of ground-water flow and natural convection in the boreholes. The test rig is set up on a some trailer, and contains a sub-circulation pump, a boiler, temperature sensors, flow meter and a data logger for recording the temperature and circulation fluid flow data. A constant heating power is injected into the SCW through the test rig and the resulting temperature change in the SCW is recorded. The recorded temperature data are analysed with a line-source model, which gives the effective in-situ values of rock thermal conductivity and thermal resistance of SCW.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.18 no.4
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• pp.45-57
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• 2022

The Ministry of National Defense of the Republic of Korea is showing a lot of interest in net zero-energy buildings (NZEBs) to reduce energy consumption of military facilities and to promote green growth policy in military sector. The application of building passive technologies and renewable energies is essential to achieving NZEBs. This paper analyzed energy performance and energy cost on the conventional heating and cooling system (baseline scenario) and three different alternative scenarios (ALT 1, ALT 2 and ALT 3) applied in a hypothetical military building. A building modeling and simulation software (DesignBuilder V6.1) with EnergyPlus calculation engine was used to calculate the energy consumption for each scenario. Overall, when the GSHPs are applied to both space airconditioning and domestic hot water (DHW) production, Alt-2 and Alt-3, the amount of energy consumption for target building can be greatly reduced. In addition, when the building envelope performance is increased like Alt-3, the energy consumption can be further reduced. The annual energy cost analysis showed that the baseline was approximately 161 million KRW, while Alt-3 was approximately 33 million KRW. Therefore, it was analyzed that the initial construction cost increase could be recovered within about 6.7 years for ALT 3. The results of this study can help decision-makers to determine the optimal strategy for implementing GSHP systems in military buildings through energy performance and initial construction cost assessment.