• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.37-51
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• 2013

An energy pile encases heat exchange pipes to exchange thermal energy with the surrounding ground formation by circulating working fluid through the pipes. An energy pile has many advantages in terms of economic feasibility and constructability over conventional Ground Heat Exchangers (GHEXs). In this paper, a coil-type PHC energy pile was constructed in a test bed and its thermal performance was experimentally and numerically evaluated to make a preliminary design. An in-situ thermal response test (TRT) was performed on the coil-type PHC energy pile and its results were compared with the solid cylinder source model presented by Man et al. (2010). In addition, a CFD numerical analysis using FLUNET was carried out to back-analyze the thermal conductivity of the ground formation from the Ttype PHC energy RT result. To study effects of a coil pitch of the coil-type heat exchange pipe, a thermal interference between the heat exchange pipes in PHC energy piles was parametrically studied by performing the CFD numerical analysis, then the effect of the coil pitch on thermal performance and efficiency of heat exchange were evaluated. Finally, an equivalent heat exchange efficiency factor for the coil-type PHC energy pile in comparison with a common multiple U-type PHC energy pile was obtained to facilitate a preliminary design method for the coil-type PHC energy pile by adopting the PILESIM2 program.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.361-375
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• 2015

An energy pile is one of the novel ground heat exchangers (GHEX's) that is a economical alternative to the conventional closed-loop vertical GHEX. The combined system of both a structural foundation and a GHEX contains a heat exchange pipe inside the pile foundation and allows a working fluid circulating through the pipe, inducing heat exchange with the ground formation. In this paper, a group of energy piles equipped with parallel U-type (5, 8 and 10 pairs) heat exchange pipes was constructed in a test-bed by fabricating in large-diameter cast-in-place concrete piles. In addition, a closed-loop vertical GHEX with 30m depth was constructed nearby to conduct in-situ thermal response tests (TRTs) and to compare with the thermal performance of the cast-in-place energy piles. A series of thermal performance tests was carried out with application of an artificial cooling and heating load to evaluate the heat exchange rate of energy piles. The applicability of cast-in-place energy piles was evaluated by comparing the relative heat exchange efficiency and heat exchange rate with preceding studies. Finally, it is concluded that the cast-in-place energy piles constructed in the test-bed demonstrate effective and stable thermal performance compared with the other types of GHEX.

• Proceedings of the Korean Society of Computer Information Conference
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• 2017.07a
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• pp.5-6
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• 2017

본 논문은 데이터를 보다 적은 소비전력으로 보관하기 위한 에너지 효율적인 파일 분산배치 정책을 제안한다. 이 정책은 개별 하드디스크 용량을 빠르게 가득 채우도록 분산 스토리지의 쓰기 동작을 처리하고, 가득 찬 하드디스크의 모터를 정지시켜 에너지 효율을 향상시킨다. Ceph 분산 스토리지를 수정하여 제안하는 파일 분산배치 정책을 적용하였으며 시뮬레이션을 통하여 제안하는 파일 분산배치 정책이 에너지 효율적임을 확인하였다.

• Journal of Internet Computing and Services
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• v.17 no.5
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• pp.59-65
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• 2016

Recently, a study has been progressed about the energy storage system for resolving energy shortage problems in the world. The energy storage system can maximize energy storage system's energy usage by monitoring and controlling about all energy infrastructures on energy network. However, compatibility problems among main components or devices of the energy storage system are obstacles to development of energy storage system products. An extensible profile and extensible profile verification software being able to verify the extensible profile have been required in order to resolve compatibility problems. In this paper, the study on complexity analysis for the extensible profile verification software for the energy storage system is performed. A XML based profile and C language structure based profile are used for analysis of the profile verification software. The complexity of complex verification structure that parses the XML based profile several times and simple verification structure that parses the C language structure based profile are analyzed and compared. Time complexity, space complexity, and cyclomatic complexity are used for complexity analysis. By using these complexity analysis, the study result that compares and analyzes the complexity of XML based and C language structure based profile verification software is presented.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.1049-1061
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• 2013

In this paper, a relative heat exchange rate is numerically compared for cast-in-place concrete energy piles with different heat exchange pipe configurations, and a new design method for energy piles is proposed. An equivalent heat exchange rate was estimated for the W-type (one series loop), multiple U-type (four parallel loops), and coil-type heat exchanger installed in the same large-diameter drilled shaft. In order to simulate a cooling operation in summer by a CFD analysis, the LWT (leaving water temperature) into a energy pile was fixed at $35^{\circ}C$ and then the EWT (entering water temperature) into a heat pump was monitored. In case of continuously applying the artificial maximum cooling load for 100 hours, all of the three types of heat exchangers show the marginally similar heat exchange rate. However, in case of intermittently applying the cooling load with a cycle of 8 hours operation-16 hours off for 7 consecutive days, the coil type heat exchanger exhibits a heat exchange rate only 86 % of the multiple U-type due to measurable thermal interference between pipe loops in the energy pile. On the other hand, the W-type possesses the similar heat exchange rate to the multiple U-type. The equivalent heat exchange rates for each configuration of heat exchangers obtained from the CFD analysis were adopted for implementing the commercial design program (PILESIM2). Finally, a design method for cast-in-place concrete energy piles is proposed along with a design chart in consideration of typical design factors.

• Journal of the Korean Geotechnical Society
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• v.35 no.10
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• pp.5-15
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• 2019

In this study, to investigate the effect of long-term performance of energy pile on ground temperature, a numerical analysis was conducted by simulating the ground where an energy pile was installed. In the analysis, a changing distance from the outer perimeter of a heat circulation pipe to the surface of concrete pile for an intermittent operation (8-hour operation, 16-hour stop) was considered. Simulation results showed that long-term heat exchange under the intermittent operation of energy pile reduced a thermal recovery in the ground and increased the ground temperature through the residual thermal energy. In addition, the ground temperature became higher as it got closer to the energy pile and increased as the distance from the outer perimeter of heat circulation pipe to the surface of concrete pile decreased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6C
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• pp.231-239
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• 2010

This paper presents the thermal conduction analysis (using ABAQUS ver 6.10 and FLUENT ver 6.3.26) of geothermal energy for PHC, steel and copper energy piles by considering subsurface environment, thermal efficiency of grouting materials, and fluid velocity of circulating fluid. Results show that higher thermal efficiency for copper pile is observed followed by steel and PHC piles depending on the grouting materials and subsurface condition. The fluid velocity of 0.6m/s presents most efficient outflow temperature (275.4K) and heat exchange rate (103.1W/m) for the case of PHC pile during 8 hours operation. Analysis of operation schedule concludes that 16 hours of stand-by allows charging geothermal energy following 8 hours operation in winter season is most appropriate with 0.1K of temperature difference from the steady-state condition.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.373-376
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• 2011

모바일 단말에서 소프트웨어의 기능을 구현할 때, 배터리 소모를 최소화 시키는 것이 매우 중요하다. 본 연구에서는 모바일 단말에서 파일 전송을 수행함에 있어서 에너지 효율적으로 처리하는 기법을 제안한다. 주요 아이디어는 클라이언트 부분에서 파일 유사도를 사용하여 대표 해시를 서버로 전송한다. 서버에서는 클라이언트에서 보내온 대표 해시와 자신이 가지고 있는 인덱스와 비교하여 유사도를 계산한다. 유사도에 따라 중복제거 파일 전송방식을 사용할지 일반적인 파일 전송을 할지 결정한다. 실험 결과 10%이상의 유사도를 가지는 파일들에 대해서 제안하는 기법이 배터리 소모를 줄일 수 있음을 보였다.

• Journal of the Korean Geotechnical Society
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• v.31 no.5
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• pp.5-21
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• 2015

An energy pile is a novel type of ground heat exchangers (GHEX's) which sets up heat exchange pipes inside a pile foundation, and allows to circulate a working fluid through the pipe for exchanging thermal energy with the surrounding ground stratum. Using existing foundation structure, the energy pile can function not only as a structural foundation but also as a GHEX. In this paper, six full-scale energy piles were constructed in a test bed with various configurations of the heat exchange pipe inside large-diameter cast-in-place piles, that is, three parallel U-type heat exchangers (5, 8 and 10 pairs), two coil type heat exchangers (with a 500 mm and 200 mm pitch), and one S-type heat exchanger. During constructing the energy piles, the constructability of each energy pile was evaluated with consideration of the installation time, the number of workers and any difficulty for installing. In order to evaluate the thermal performance of energy piles, the thermal performance tests were carried out by applying intermittent (8 hours operating-16 hours pause) artificial cooling operation to simulate a cooling load for commercial buildings. Through the thermal performance tests, the heat exchange rates of the six energy piles were evaluated in terms of the heat exchange amount normalized with the length of energy pile and/or the length of heat exchange pipe. Finally, the economic feasibility of energy pile was evaluated according to the various types of heat exchange pipe by calculating demanded expenses per 1 W/m based on the thermal performance test results along with the market value of heat exchange pipes and labor cost.

• Journal of Internet Computing and Services
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• v.16 no.5
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• pp.29-38
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• 2015

The Energy Storage System stores electricity for later use. This system can store electricity from legacy electric power systems or renewable energy systems into a battery device when demand is low. When there is high electricity demand, it uses the electricity previously stored and enables efficient energy usage and stable operation of the electric power system. It increases the energy usage efficiency, stabilizes the power supply system, and increases the utilization of renewable energy. The recent increase in the global interest for efficient energy consumption has increased the need for an energy storage system that can satisfy both the consumers' demand for stable power supply and the suppliers' demand for power demand normalization. In general, an energy storage system consists of a Power Conditioning System, a Battery Management System, a battery cell and peripheral devices. The specifications of the subsystems that form the energy storage system are manufacturer dependent. Since the core component interfaces are not standardized, there are difficulties in forming and operating the energy storage system. In this paper, the design of the profile structure for energy storage system and realization of private profiling system for energy storage system is presented. The profiling system accommodates diverse component settings that are manufacturer dependent and information needed for effective operation. The settings and operation information of various PCSs, BMSs, battery cells, and other peripheral device are analyzed to define profile specification and structure. A profile adapter software that can be applied to energy storage system is designed and implemented. The profiles for energy storage system generated by the profile authoring tool consist of a settings profile and operation profile. Setting profile consists of configuration information for energy device what composes energy saving system. To be more specific, setting profile has three parts of category as information for electric control module, sub system, and interface for communication between electric devices. Operation profile includes information in relation to the method in which controls Energy Storage system. The profiles are based on standard XML specification to accommodate future extensions. The profile system has been verified by applying it to an energy storage system and testing charge and discharge operations.