• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.724-726
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• 1996

In this paper, we propose an optimal daily operation model for the total energy system which includes cogeneration, thermal storage and electrical charger and ice storage facilities. Storing and utilizing the surplus thermal and electrical energy, the daily operation cost could be reduced and more efficient use of thermal energy could be achieved. The ice storage cooling system has a merit of reduce the electricity cost by time of day rate(peak/off-peak). And also, refrigerator can be down sized compare to the other cooling system From this model, operation costs of the sample cogeneration system with/without auxiliary facilities are obtained and compared to each other. In case study, the sensitivity of operating cost is simulated according to the variation of cogeneration production cost, electricity rate, etc.

• Solar Energy
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• v.18 no.1
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• pp.99-109
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• 1998

The study on ice thermal storage system is to improve total system performance in actual air-conditioning facilities. To attain the high efficiencies in ice thermal storage system, the improvement of thermal stratification is essential, therfore the process flow must be piston flow in thermal storage tank. Ice packing factor is better on condition that the inflowing temperature is low, the flow direction in the thermal storage is upward and the cylindericalthermal storage type is used. This result shows that the cylinderical ice storage tank has better storage capacity than the rectangular type in case of the same porocity.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.20-23
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• 2006

Geothermal energy is the natural heat of the Earth. Enormous amounts of thermal energy are continuously generated by the decay of radioactive isotopes of underground rocks and stored in the Earth's interior. Therefore, geothermal energy is one of the most important sustainable energy resources. Recent trends of geothermal energy exploitation technologies focus on the Earth scientific approach to geothermal heat pump system, enhanced geothermal system, aquifer thermal energy storage, underground thermal energy storage, and fluid/heat flow model ing for geothermal wells. Geothermal heat pump distribution in Korea is still in its starting phase in terms of areal utilization sense, we, however, expect to come up with national supply of over 1,000,000 toe by 2020

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.11
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• pp.990-997
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• 2005

The stratified effect was investigated with three different types of diffuser shape in a thermal storage tank with variation of diffuser diameter, velocity, Froude number etc. Its effect was estimated by the degree of stratification. No matter of diffuser diameter and shape, the degree of stratification was the best as the Froude number gets closer to 1. In the case of a curved diffuser, when its diameter is a quarter of tank diameter and ejection velocity in a diffuser is approximately 0.2 m/s, the Froude number was almost 1. In the case of a flatted diffuser, when ejection velocity was 0.05 m/s, the Froude number was 1.5. Both cases which Froude number were nearer 1, showed the good degree of stratification.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.475-479
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• 2012

Thermal energy storage (TES) systems using Microencapsulated phase change material (MPCM) have been recognized as one of the most advanced energy technologies in enhancing the energy efficiency and sustainability of buildings. We examined a way to incorporate MPCMs with building materials through application for wood-based flooring. Wood-based flooring is commonly used for floor finish materials of residential buildings in Korea. However, wood-based flooring has not performed the characteristic of heat storage. This study is aimed at manufacturing high thermal efficiency wood flooring by increasing its heat storage using MPCM. As a result, this study confirmed that MPCM is dispersed well in adhesive through the scanning electron microscopy analysis. From the differential scanning calorimetry analysis, it can be confirmed that this composite has the characteristic of a thermal energy storage material. Also, we analyzed how this composition was formed by physical combination through the Fourier transform infrared analysis. Also, we confirmed the bonding strength of the material by using the universal testing machine.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.1
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• pp.9-17
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• 2019

Reducing global warming potential has become important, and as one of those methods for reducing it, economic evaluation by applying ice thermal storage air conditioning system was performed. The floor area and height of the subject building was assumed $5,000m^2$ and 20 m. Absorption chillerheater system and air source heat pump system was used for comparing to the subject system, and payback period method was used to perform economic evaluation. Although the running cost of ice thermal storage system is reduced compared to two systems, the ratio is not significant compared to the increase of initial construction expenses, and payback period was calculated to be about 7.7 and 79.3 years. However, the heat storage system should be approached from the viewpoint of long term rather than the economic standard in the present standard.

• Journal of Hydrogen and New Energy
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• v.29 no.3
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• pp.251-259
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• 2018

Metal hydride based hydrogen storage under moderate temperature and pressure gives the safety advantage over the gas and liquid storage methods. Still solid-state hydrogen storage including metal hydride is below the DOE target level for automotive applications, but it can be adapted to stationary or miliary application reasonably. In order to develop a modular solid state hydrogen storage system that can be applied to a distributed power supply system composed of renewable energy - water electrolysis - fuel cell, the heat transfer and hydrogen storage characteristics of the metal hydride necessary for the module system design were investigated using AB5 type metal hydride, LCN2 ($La_{0.9}Ce_{0.1}Ni_5$). The planetary high energy mill (PHEM) treatment of LCN2 confirmed the initial hydrogen storage activation and hydrogen storage capacity through surface modification of LCN2 material. Expanded natural graphite (ENG) addition to LCN2, and compression molding at 500 atm improved the thermal conductivity of the solid hydrogen storage material.

• Tunnel and Underground Space
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• v.23 no.1
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• pp.78-85
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• 2013

A primary objective in creating a stratified thermal storage is to maintain the thermodynamic quality of energy, so thermally stratified energy can be extracted at temperatures required for target activities. The separation of the thermal energy in heat stores to layers with different temperatures, i.e., the thermal stratification is a key factor in achieving this objective. This paper introduces different methods that have been proposed to characterize the thermal stratification in heat stores. Specifically, this paper focuses on the methods that can be used to determine the ability of heat stores to promote and maintain stratification during the process of charging, storing and discharging. In addition, based on methods using thermal stratification indices, the degrees of stratification of stored energy in Lyckebo rock cavern in Sweden were compared and the applicability of the methods was investigated.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.442-453
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• 2013

A large-scale high-temperature thermal energy storage(TES) was numerically modeled and the heat loss through storage tank walls was analyzed using a commercial code, FLAC3D. The operations of rock cavern type and above-ground type thermal energy storages with identical operating condition were simulated for a period of five consecutive years, in which it was assumed that the dominant heat transfer mechanism would be conduction in massive rock for the former and convection in the atmosphere for the latter. The variation of storage temperature resulting from periodic charging and discharging of thermal energy was considered in each simulation, and the effect of insulation thickness on the characteristics of heat loss was also examined. A comparison of the simulation results of different storage models presented that the heat loss rate of above-ground type TES was maintained constant over the operation period, while that of rock cavern type TES decreased rapidly in the early operation stage and tended to converge towards a certain value. The decrease in heat loss rate of rock cavern type TES can be attributed to the reduction in heat flux through storage tank walls followed by increase in surrounding rock mass temperature. The amount of cumulative heat loss from rock cavern type TES over a period of five-year operation was 72.7% of that from above-ground type TES. The heat loss rate of rock cavern type obtained in long-period operation showed less sensitive variations to insulation thickness than that of above-ground type TES.

• Journal of Biosystems Engineering
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• v.25 no.5
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• pp.379-384
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• 2000

In order to use the natural thermal energy as much as possible for greenhouse heating, the air-air heat pump system involved PCM(phase change material) latent heat storage system was composed, and three types of greenhouse heating system(greenhouse system, greenhouse-PCM latent heat storage system, greenhouse-PCM latent heat storage-heat pump system) were recomposed from the greenhouse heating units to analyze the heating characteristics. The results could be concluded as follows; 1) In the greenhouse heated by the heat pump under the solar radiation of 406.39W/$m^2$, the maximum PCM temperature in the latent heat storage system was 24$^{\circ}C$ and the accumulated thermal energy stored in PCM mass of 816kg during the daytime was 100,320kJ. In the greenhouse without heat pump under the maximum solar radiation of 452.83W/$m^2$, the maximum PCM temperature in the latent heat storage system was 22$^{\circ}C$ and the accumulated thermal energy stored during the daytime was 52.250kJ. 2) In the greenhouse-PCM system without heat pump the heat stored in soil layers from the surface to 30cm of the soil depth was 450㎉/$m^2$. 3) In all of the greenhouse heating systems, the difference between the air temperature in greenhouse and the ambient temperature was about 20~23$^{\circ}C$ in the daytime. In the greenhouse without heat pump and PCM latent heat storage system the difference between the ambient temperature and the air temperature in the greenhouse was about 6~7$^{\circ}C$ in the nighttime, in the greenhouse with only PCM latent heat storage system the temperature difference about 7~13$^{\circ}C$ in the nighttime and in the greenhouse with the heat pump and PCM latent heat storage system about 9~14$^{\circ}C$ in the nighttime.