• Journal of the Korean Solar Energy Society
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• v.37 no.5
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• pp.39-47
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• 2017

In a hot water system using solar energy, solar heat is not simply collected by the heat collecting plate, but by heat exchange between the solar collector (flat or vacuum type) and the hot water storage tank. Therefore, the amount of collected solar energy depends on the hot water usage patterns that determine the temperature of the thermal storage tank. Also, if the temperature of the hot water stored in the storage tank exceeds the dangerous temperature during the summer, the heat must be released for safety. If the temperature of the hot water in the storage tank is low, it is necessary to heat by the auxiliary heat source. In this study, three buildings are defined as hotel, swimming pool, and school facilities. And we calculated the released heat energy, auxiliary heat source, and pure storage heat energy based on different hot water usage patterns and installation angle of the solar collectors.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.3
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• pp.315-324
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• 1994

The energy recovery efficiency(ERE) of an aquifer thermal energy storage system was calculated using curvilinear coordinate. The results of the calculation were compared with the experimental results, and agreed within 11% of the discrepancy. The variation of ERE was investigated as a function of the underground water natural velocity, the amount of the stored energy, and period of the energy recovery. The slower the natural velocity and shorter the recovery period, the higher ERE was yielded. Also it was found that increase in the amount of energy storage yields higher ERE, and carries out less influential ERE to the natural velocity. Reiterative usage of the aquifer as a thermal storage tends to gradually increase ERE. The result of this study implements that the aquifer thermal energy storage system is suitable for large cooling/heating loads, such as district cooling/heating.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.10
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• pp.733-738
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• 2012

It is important issue to reduce the electric energy to save the operating cost of HVAC system. Even if electrical energy is the clean energy, it is difficult and takes high cost for storage of electricity. These cause the high peak load of electric energy for HVAC in summer season. In korea, government impose the electric charge with several grade for the purpose of cut-off the peak load of electricity. Government has a policy to support to design and install the heat/ice storage system using midnight electricity. In this study, analysis of cooling load and operating characteristics for ice storage system are performed. And, also economical efficiency is compared between ordinary charge system of electricity and midnight rate charge of electricity. The systematic and economical supports are needed for expansion of usage of energy saving equipments.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.6
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• pp.247-256
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• 2014

The regulations to reduce energy consumption and carbon dioxide emission in building sectors are being developed and promoted all over the world. However, in Korea, as balcony extension of the apartments has been legally allowed, it became prevalent and resulted in excessive energy consumption. This study derived the possibility of PCM application to the thermal storage wall system through theoretical consideration and investigated the problems occurring when the balcony space has been extended to the diverted space. In addition, this study aims at the possibility of verifying the installation and confirming the cooling energy reduction effect, by conducting measuring tests with the actual installation of PCM applied thermal storage wall system. As a result of theoretical consideration, it is determined that the disadvantages with the existing thermal storage wall system can be complemented by applying PCM, and this study suggests the PCM applied Thermal Storage Wall System. The study was conducted on 1/6 of a miniature inner room of a domestic apartment with 84 $m^2$ of exclusive area. From the results of actual measurements, it is confirmed that the balcony extension structure can gain 11.3% of more calories than the existing balcony structure, resulting in the increase in cooling energy usage. It is determined that the installation of the PCM applied Thermal Storage Wall System may gain 25.2% of less calories to reduce cooling energy usage.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.1
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• pp.53-58
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• 2016

Because a progressive tax of home electricity rates is charged and a continuous rise of industrial electricity rates is expected in order to solve the global warming, the high oil prices and the serious power shortage problem, the efforts to apply the energy storage systems which can significantly improve the energy usage efficiency to the smart grid are trying newly. In this study, characteristics of the secondary battery which can be used as energy storage devices, the structure and operation principle of a lithium-ion battery, and the concept of energy storage systems are research and analyzed. In addition, in this paper, the base technologies which are required to apply to the energy storage system to electric power system are established by studying about installation location and application methodology of energy storage system to electric power system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.3
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• pp.123-127
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• 2015

Thermochemical heat storage is a cutting-edge technology which can balance the energy usage between supplies and demands. Recent studies have suggested that thermochemical heat storage has significant advantages, compared to other storage methods such as latent heat storage or sensible heat storage. Nevertheless, ongoing research and development studies showed that the thermochemical heat storage has some serious problems. To bring the thermochemical heat storage method into market, we introduce experimental setup with composite material using perlite that supports calcium chloride sorbent. Also, to compare thermal properties with composite material, we used pure thermochemical material. Then, we found that the composite material has higher heat storage density by mass than pure calcium chloride. Moreover, it can be easily regenerated, which was impossible in the pure thermochemical materials.

• Applied Chemistry for Engineering
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• v.30 no.3
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• pp.290-296
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• 2019

Lithium-ion batteries are one of the most interesting devices in a number of energy storage systems. In particular, the usage of energy storage devices is increasing due to an increase in demand for renewable energy as a distributed power supply source, stable supply of electric power, and expansion of electric vehicles. Of late, the recycling and restoration technology of waste lithium ion batteries due to the increase in its usage amount as the energy storage system is a socially and economically important research field. In this review, we intend to describe the performance diagnosis, recycling or restoration technology of lithium ion battery and its potential development.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1288-1293
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• 2009

The TES (Thermal Energy Storage) cooling system utilizing cheaper off-peak electricity has been applied just for building air-conditioning currently and causes limitation of usage rate and inefficiency of national resources utilization. In this regard, more says the necessity to apply TES system in industrial cooling system which is longer using period and wider usage. In this study, we will approve the technical and economical improvement in efficiency of industrial cooling system applied TES system by utilizing cheaper off-peak electricity and it will attribute the promotion of TES system and stabilization of supply and demand of electric power by proving the necessity to develop more efficient industrial cooling system by combining TES system.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1052-1054
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• 1992

The conventional serial UPS using battery energy storage unit is almost universally used. Despite its common usage, the conventional UPS has a number of disadvantages which may be effectively overcome by the application of flywheel energy storage unit. This paper proposes a new type of parallel processing UPS using flywheel energy storage unit, which has the feature of high power, long life, and high efficiency.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.6 s.171
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• pp.199-206
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• 2005

In this work, a theoretical investigation on the energy harvesting is undertaken using one of potential smart materials; piezoelectric material. The energy equations fur both square and circular types of the piezoelectric material are derived, and the energy generated from two commercially available Products: $PZT (Lead/Zirconium/Titanium: Pb(Zr,\;Ti)O_3)$ and PVDF (polyvinylidene fluoride) are investigated in terms of the thickness and area. In addition, a finite element analysis (FEA) is undertaken to obtain the generated energy due to the uniform pressure applied on the surface of the piezoelectric materials. A comparative work between the theory and the FEA is made followed by the brief discussion on the usage of the harvested energy for Bio MEMS.