• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.35 no.3
• /
• pp.43-48
• /
• 2019

Since the revision of the Rationalization of Energy Use Law, the spread of new and renewable energy in buildings has been promoted. In addition, the production of electric power and thermal energy is an important issue in the change of energy paradigm centered on the use of distributed energy. Among them, geothermal energy is attracting attention as a high-performance energy-saving technology capable of coping with heating / cooling and hot water load by utilizing the constant temperature zone of the earth. However, there is a disadvantage that the initial investment cost is high as a method of calculating the capacity of a geothermal facility by calculating the maximum load. The disadvantages of these disadvantages are that the geothermal energy supply is getting stagnant and the design of the geothermal system needs to be supplemented. In this study, optimization design of geothermal system was carried out using optimization tool. As a result of the optimization, the ground heat exchanger decreased by 30.8%, the capacity of the heat pump decreased by 7.7%, and the capacity of the heat storage tank decreased by about 40%. The simulation was performed by applying the optimized value to the program and confirmed that it corresponds to the load of the building. We also confirmed that all of the constraints used in the optimization design were satisfied. The initial investment cost of the optimized geothermal system is about 18.6% lower than the initial investment cost.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.11a
• /
• pp.144-144
• /
• 2010

Reasonable usage methods of energy resources, which are limited for human beings to use, consists of new & renewable energy (NRE) and demand side management (DSM). All technologies and policies for energy resources are classified into two fields, methods for using new energy resources and methods for using conventional fuel energy resources. Various development activities for these fileds have been implemented and various subsidy programs have been operated to penetrate into markets rapidly. These subsidy programs have various types of subsidy by energy resources and programs and the budget are funded by government, which is called Electric Power Industry Basis Fund and is managed considering technology level, economic analysis, global environment, etc. These subsidy programs are managed by Korea Energy Management Corporation (KEMCO) for NRE and by Korea Electric Power Corporation (KEPCO) for DSM, the management are different among two corporations because the purposes and features of establishment are different though these are all public organization. KEMCO is managing the NRE subsidy programs according to the government will, while the management of KEPCO subjects to power system operations though the government will for DSM is considered. NRE which is on the initial phase of diffusion would not affect on power system seriously but the affects could be grown when the diffusion and importance are expanded. Hence some integrated affection analyses considering NRE and DSM are required and this paper shows the concept of integrated operation strategies with ground source heat pump systems which are related with two fields simultaneously.

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

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.28 no.10
• /
• pp.402-407
• /
• 2016

Ground-coupled heat pump systems have been widely used, as they are regarded as a renewable energy source and ensure a high annual efficiency. Among the system components, borehole heat exchangers (BHE) play an important role in decreasing the entering water temperature (EWT) to heat pumps in the cooling season, and consequently improve the COP. The optimal sizing of the BHEs is crucial for a successful project. Other than the existing sizing methods, a simulation-based design tool is more applicable for modern complex geothermal systems, and it may also be useful since design and engineering works operate on the same platform. A simulation-based sizing method is proposed in this study using the well-known Duct STorage (DST) model in Trnsys. TRNOPT, the Trnsys optimization tool, is used to search for an optimal value of the length of BHEs under given ground loads and ground properties. The result shows that a maximum EWT of BHEs during a design period (10 years) successfully approaches the design EWT while providing an optimal BHE length. Compared to the existing design tool, very similar lengths are calculated by both methods with a small error of 1.07%.

• Journal of the Korean Geotechnical Society
• /
• v.24 no.1
• /
• pp.37-49
• /
• 2008

A geothermal heat pump system is a preferable alternative energy system in Korea because it uses the heat energy of the earth, which is environmentally friendly and inexhaustible. In order to characterize the thermal conductivity and viscosity of grout materials used for backfilling ground heat exchangers, nine bentonite grouts, one marine clay from Boryung, and cement grouts adapted in the United State have been considered in this study. The bentonite grouts indicate that the thermal conductivity and viscosity increase with the content of bentonite or filler (silica sand). In addition, material segregation can be observed when the viscosity of grout is relatively low. The marine clay turns out to be unsuitable for backfilling the ground heat exchanger due to its insufficient swelling potential. The saturated cement grouts appear to possess much higher thermal conductivity than the saturated bentonite grouts, and the reduction of thermal conductivity in the cement grouts after drying specimens is less than that in the case of the bentonite grouts. Maintaining the moisture content of grouts is a crucial factor in enhancing the efficiency of ground heat exchangers.

• Economic and Environmental Geology
• /
• v.43 no.2
• /
• pp.197-205
• /
• 2010

Recently abrupt climate changes have been occurred in global and regional scales and $CO_2$ reduction technologies became an important solution for global warming. As a method of the solution shallow underground thermal energy storage (UTES) has been applied as a reliable technology in most countries developing renewable energy. The geothermal energy system using thermal source of soil, rock, and ground water in aquifer or cavern located in shallow ground is designed based on the concept of thermal energy recovery and storage. UTES technology of Korea is in early stage and consistent researches are demanded to develop environmental friendly, economical and efficient UTES systems. Aquifers in Korea are suitable for various type of ground water source heat pump system. However due to poor understanding and regulations on various UTES high efficient geothermal systems have not been developed. Therefore simple closed U-tube type geothermal heat pump systems account for more than 90% of the total geothermal system installation in Korea. To prevent becoming wide-spread of inefficient systems, UTES systems considering to the hydrogeothemal properties of the ground should be developed and installed. Also international collaboration is necessary, and continuous UTES researches can improve the efficiency of shallow geothermal systems.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.10a
• /
• pp.1475-1486
• /
• 2008

Bentonite-based grouting has been popularly used to seal a borehole installed for a closed-loop vertical ground heat exchanger in a geothermal heat pump system (GHP) because its high swelling potential. However, if the bentonite-based grouting is conducted in coastal areas, the salinity of groundwater changes in the mineral fabric of bentontie. In order words, an increase of cation concentration in groundwater leads to a reduction in the diffuse double-layer thickness in the bentonite mineral structure, and thus the volume of bentointe-based grouts will decrease proportional to the salinity of groundwater. In this paper, the effect of salinity (i.e., NaCl 0.5M, 0.25M, and 0.1M) on the change of swelling potential for bentonite-based grouts has been quantitatively evaluated for seven bentonite grouts from different product sources. In addition, in case of using addictives such as a silica sand to increase the thermal conductivity of bentonite-based grouts, the possibility of particle segregation has been studied considering the viscosity of grouts and salinity of groundwater.

• Economic and Environmental Geology
• /
• v.39 no.3 s.178
• /
• pp.255-268
• /
• 2006

Recent 22-year (1981-2002) meteorological data of 58 Korea Meteorological Adminstration (KMA) station were analyzed to investigate spatial and temporal variation of surface air temperature (SAT) and ground surface temperature (GST) in Korea. Based on the KMA data, multiple linear regression (MLR) models, having two regression variables of latitude and altitude, were presented to predict mean surface air temperature (MSAT) and mean ground surface temperature (MGST). Both models showed a high accuracy of prediction with $R^2$ values of 0.92 and 0.94, respectively. The prediction of MGST is particularly important in the areas of geothermal energy utilization, since it is a critical parameter of input for designing the ground source heat pump system. Thus, due to a good performance of the MGST regression model, it is expected that the model can be a useful tool for preliminary evaluation of MGST in the area of interest with no reliable data. By a simple linear regression, temporal variation of SAT was analyzed to examine long-term increase of SAT due to the global warming and the urbanization effect. All of the KMA stations except one showed an increasing trend of SAT with a range between 0.005 and $0.088^{\circ}C/yr$ and a mean of $0.043^{\circ}C/yr$. In terms of meteorological factors controlling variation of GST, the effects of solar radiation, terrestrial radiation, precipitation, and snow cover were also discussed based on quantitative and qualitative analysis of the meteorological data.

• KIEAE Journal
• /
• v.15 no.1
• /
• pp.103-109
• /
• 2015

Recently, the usage of renewable energy system has been recommended because of the energy saving and depletion of fossil fuel. Especially, ground source heat pump system(GSHP) has a high efficiency by using annual stable ground temperature. Also, wood pellet is low cost and a high calorific value compared to fossil fuel. However, only small number of farms have applied renewable energy system to horticultural facility because of a high initial costs and uncertainty of its cost efficiency. In this study, in order to analyze the feasibility for the horticulture, TRNSYS simulation based on the standard horticultural facility was conducted in different weather and covering material conditions. Then, comparative feasibility analysis of each energy supplying system was conducted. As a result, we have found out that a high initial cost of renewable energy system was recovered by the economics of the energy cost. Due to the energy cost reduction, the payback periods were 10-11 years in the case of GSHP and 4-6 years in the case of wood pellet boiler.

• Korean Journal of Construction Engineering and Management
• /
• v.10 no.4
• /
• pp.111-118
• /
• 2009

This study is to analyze the performance of SWH(Solar Water Heating) and GSHP(Ground Source Heat Pump) systems by evaluating their energy efficiency and LCC(Life Cycle Cost) as being applied to the OO hall as a selected building in the Army. The OO hall, used as bathrooms, dining rooms, accommodations and offices, has reinforced concrete structure system with three floors above the ground and one underground, and its total floor area is approximately 2,917$m^2$. Two energy simulations are conducted to predict the yearly cooling and heating energy of the selected building: One is for analysis of an air-conditioning energy consumption using the e-Quest program, and another is for two new-renewable energy facilities as a water heating source using the RETScreen. The installed capacity of two new-renewable energy facilities is determined according to the 5% level of total standard construction cost. As a briefly result, SWH system is more energy-effective than GSHP system. Considering the break-even point, it is expected that SWH can take only 3 years 11 months to pay for itself in savings while the investment of GSHP can be recovered in more than 16 years 6 months.