• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.431-437
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• 2015

Recently, a miniaturized measurement cell of effective thermal conductivity was developed to evaulate the heat transfer characteristics of hydrogen stroage material in the initial step of its development. In this work, the realiablity issues which can occur from this miniaturization of measurement cell were studied in detail by both experiments and numerical simulation of heat transfer. $LaNi_5$ as a reference was used for the reliability evaluation of the miniaturized measurement cell. Numerical simulations of heat transfer for this measurement system were verified through comparison with the experimental data. Under these reliablity studies, we discuss how to overcome the inherent drawbacks of this miniaturized system in order to achieve the high reliability.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.563-566
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• 2006

An investigation has been carried for the thermal characteristics of the seasonal storage installation in Cheju. It features the solar collector area of $340m^2$ and the storage capacity of $600m^3$. Four different types of solar collector systems are compared for their performance of collecting solar energy throughout the year. Of these, two are made of tubular shaped vacuum collectors and the others are flat plate collectors. Results indicate that each system could play an important role in exploiting solar energy depending on the temperature range in its operation. Especially, the vacuum collectors outperformed the others when the inlet temperatures of the collector loop were raised beyond $40m^2$. This became more conspicuous as the return temperatures from the storage tank rose reflecting the seasonal variation. Due to the large heat capacity of the storage tank, temperature changes were rather small compared to those in the collecting loop regardless of seasonal fluctuations.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.576-579
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• 2006

This paper describes characteristics and procedure of the basic design of large scale solar thermal power plant system. The evaluation is based on the operating data of CESA-I, solar central receiver plant. In order to evaluate the solar irradiation on the receiver, it is necessary to calculate the amount of thermal energy consumption at steam turbine and storage system in the STPPS. Especially, it is need to take into account of the storage and operating time to design a plant efficiently. In addition, basic design is performed for the CESA-I using the software tool of THERMOFLEX program. Based on the results, It is at lowed to use the program to investigate detail performance of each units of the STPPS by varying the operating conditions.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.701-704
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• 2005

Aquifer Thermal Energy Storage (ATES) can be a cost-effective and renewable geothermal energy source, depending on site-specific and thermohydraulic conditions. To design an effective ATES system having influenced by groundwater movement, understanding of thermo hydraulic processes is necessary. The heat transfer phenomena for an aquifer heat storage are simulated using FEFLOW with the scenario of heat pump operation with pumping and waste water reinjection in a two layered confined aquifer model. Temperature distribution of the aquifer model is generated, and hydraulic heads and temperature variations are monitored at the both wells during 365 days. The average groundwater velocities are determined with two hydraulic gradient sets according to boundary conditions, and the effect of groundwater flow are shown at the generated thermal distributions of three different depth slices. The generated temperature contour lines at the hydraulic gradient of 0.00 1 are shaped circular, and the center is moved less than 5m to the groundwater flow direction in 365 days simulation period. However at the hydraulic gradient of 0.01, the contour center of the temperature are moved to the end of boundary at each slice and the largest movement is at bottom slice. By the analysis of thermal interference data between two wells the efficiency of the heat pump system model is validated, and the variation of heads is monitored at injection, pumping and no operation mode.

• Advances in Energy Research
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• 제4권1호
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• pp.29-45
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• 2016

There has been a growing interest in the recent time for the development of solar power tower plants, which are mainly used for utility scale power generation. Combined heat and power (CHP) is an efficient and clean approach to generate electric power and useful thermal energy from a single heat source. The waste heat from the topping Brayton cycle is utilized in the bottoming HRSG cycle for driving steam turbine and also to produce process steam so that efficiency of the cycle is increased. A thermal storage system is likely to add greater reliability to such plants, providing power even during non-peak sunshine hours. This paper presents a conceptual configuration of a solar power tower combined heat and power plant with a topping air Brayton cycle. A simple downstream Rankine cycle with a heat recovery steam generator (HRSG) and a process heater have been considered for integration with the solar Brayton cycle. The conventional GT combustion chamber is replaced with a solar receiver. The combined cycle has been analyzed using energy as well as exergy methods for a range of pressure ratio across the GT block. From the thermodynamic analysis, it is found that such an integrated system would give a maximum total power (2.37 MW) at a much lower pressure ratio (5) with an overall efficiency exceeding 27%. The solar receiver and heliostats are the main components responsible for exergy destruction. However, exergetic performance of the components is found to improve at higher pressure ratio of the GT block.

• 한국건설순환자원학회논문집
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• 제8권4호
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• pp.571-580
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• 2020

본 연구에서는 열에너지 저장시스템의 중요한 요소인 저장 매체에 관한 연구를 수행하였다. 열에너지 저장 매체로써 콘크리트는 열적 및 역학적 특성이 우수하며 저렴한 비용으로 인해 다양한 이점을 갖는다. 또한, 강섬유가 혼입된 초고강도 콘크리트는 고인성 및 고강도 특성으로 인해 고온 노출에 우수한 내구성을 나타내며, 강섬유의 높은 열전도율은 축열 및 방열에 유리한 영향을 미친다. 초고강도 콘크리트의 온도분포 특성을 파악하기 위하여 콘크리트 블록을 제작하고 일정한 열사이클을 적용하여 가열실험을 수행하였다. 열유체 흐름에 의한 열전달을 위하여 열전달 파이프를 콘크리트 블록 중심부에 매립하였다. 또한, 열전달 파이프 형상에 따른 온도분포 특성을 비교하기 위하여 핀의 유무에 따라 원형 파이프 및 종방향 핀 부착 파이프를 설정하였다. 열사이클에 따른 온도분포 특성을 분석하고, 이를 토대로 시간에 따른 열에너지 및 누적 열에너지를 산정하여 비교 분석하였다. 열사이클이 반복될수록 강섬유 혼입 초고강도 콘크리트는 고온에 대하여 안정화를 나타내었다. 또한, 온도분포 및 열에너지 산정 결과를 통해 축열 성능을 보유한 것으로 판단되며, 열에너지 저장 매체 역할을 수행할 수 있는 재료로 기대된다.

• 설비공학논문집
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• 제17권4호
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• pp.341-346
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• 2005

The simplification of solar thermal systems reduces the possibility of operating trouble and lowers the cost of the initial investment and maintenance. This also leads to increased competitiveness in the energy market. We proposed a spiral-jacketed storage tank that functions both as a heat exchanger and expansion tank, which removes the secondary piping and markedly simplifies the entire system. The new storage tank was designed and manufactured to maintain the same performance as the conventional system and the exiting system was remodelled by adopting the newly proposed storage tank. This experiment was conducted under real conditions over a period of several months. The retrofitted system with the spiral-jacketed storage tank showed good performance that is on a similar level as the previous system having a typical storage tank and heat exchanger.

• 태양에너지
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• 제8권1호
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• pp.13-21
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• 1988

Heat transfer phenomena in a high-temperature heat storage unit were investigated using molten salts. Carbonate salt, an equimolar mixture of $Li_2CO_3$ and $K_2CO_3$, which melts at $505^{\circ}C$ with a latent heat of 82 cal/g, was selected as the most promising latent heat storage material based on its low cost and excellent thermophysical properties at moderately high temperatures. It was also found that nitrate salts were good candidates of sensible heat storage materials. For the carbonate salt to be utilized commercially, however, several means of enhancing thermal recovery must be explored by promoting heat conduction through the solid salt formed during the heat discharge period. These would be achieved by the additions of aluminum screens and wool, and stainless fins. Finally, experimental results of moving boundary of phase change were well compared with predictied values obtained from the approximate solution.

• Journal of Advanced Marine Engineering and Technology
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• 제26권2호
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• pp.240-247
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• 2002

Recently, a thermal energy storage system has been developed actively fur the purpose of saving energy and reducing the peak electrical demand. Especially, ice slurry is a promising working fluid for low temperature energy storage systems. A flow of ice crystals has a large cooling capacity as a result of the involvement of latent heat. However, there are still problems related to the recrystallization of ice crystals for realizing long term storage and long distance transportation. To find improvements fur this, a method for the creation of ice crystals resistant to recrystallization has been proposed and researched by the use of an antifreeze protein (AFP) solution etc. In the present study, it has been investigated the growth of ice crystal in several kinds of water solution added non-ionic surfactant. The results shows that size of ice crystal was smaller with increasing in added surfactant. And ice crystal was not increased with added surfactant.

• 자원환경지질
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• 제43권2호
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• pp.197-205
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• 2010

최근 급격한 기후변화가 세계적 또는 국지적으로 발생하고 있으며, 지구온난화에 대한 대책으로 $CO_2$ 저감 기술들이 중요한 해결책으로 여겨지고 있다. 이 기술들에 대한 한 방법으로서 대체에너지를 개발하고 있는 대부분의 국가에서 천부 지하 열에너지 저장 (UTES: underground thermal energy storage)은 신뢰성 있는 냉난방 기술로 적용되어 왔다. 천부의 토양이나 암반, 대수층내 지하수 및 지하공간내 저장된 유체 등의 열 에너지원을 이용하는 지열 시스템은 일반적으로 열에너지의 회복과 저장의 개념을 기반으로 한다. 아직 국내에서는 이러한 기술 개발이 기초적이지만 지속적인 연구들을 수행한다면 보다 친환경적이며 경제성 및 효율이 높은 시스템을 개발할 수 있을 것으로 본다. 국내 지반은 대수층이 전국적으로 분포하고 있으므로 수리지열학적 특성을 활용한 고효율의 시스템 개발이 용이하다. 그러나 UTES에 대한 이해 부족 및 제도적 문제들로 다양한 시스템이 개발되지 못하고 국내에는 90% 이상이 단편적인 폐회로형 지열시스템으로 보급되고 있다. 비효율적인 지열시스템의 보급 확산을 방지하기 위해서는 지반의 수리 지열학적 특성을 반영한 선진화된 UTES 시스템들을 개발할 필요가 있다. 개선된 시스템 보급을 위하여 국제적인 협력이 필수적이며, 지속적인 UTES 연구를 통하여 천부 지열시스템의 효율을 개선시킬 수 있다.