• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.83-89
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• 2020

For the past few decades, as part of efforts to protect the environment where fossil fuels, which have been a key energy resource for mankind, are becoming increasingly depleted and pollution due to industrial development, ecofriendly secondary batteries, hydrogen generating energy devices, energy storage systems, and many other new energy technologies are being developed. Among them, the lithium-ion battery (LIB) is considered to be a next-generation energy device suitable for application as a large-capacity battery and capable of industrial application due to its high energy density and long lifespan. However, considering the growing battery market such as eco-friendly electric vehicles and drones, it is expected that a large amount of battery waste will spill out from some point due to the end of life. In order to prepare for this situation, development of a process for recovering lithium and various valuable metals from waste batteries is required, and at the same time, a plan to recycle them is socially required. In this study, we introduce a nanoscale pattern transfer printing (NTP) process of Li2CO3, a representative anode material for lithium ion batteries, one of the strategic materials for recycling waste batteries. First, Li2CO3 powder was formed by pressing in a vacuum, and a 3-inch sputter target for very pure Li2CO3 thin film deposition was successfully produced through high-temperature sintering. The target was mounted on a sputtering device, and a well-ordered Li2CO3 line pattern with a width of 250 nm was successfully obtained on the Si substrate using the NTP process. In addition, based on the nTP method, the periodic Li2CO3 line patterns were formed on the surfaces of metal, glass, flexible polymer substrates, and even curved goggles. These results are expected to be applied to the thin films of various functional materials used in battery devices in the future, and is also expected to be particularly helpful in improving the performance of lithium-ion battery devices on various substrates.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.78-80
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• 2009

최근 화석에너지원의 고갈과 고유가 및 지구 온난화 방지를 위해 국가별로 이산화탄소 배출량을 규제하기 시작하면서 신재생 에너지의 사용에 대한 관심이 높아지고 있다. 그 중 연료전지가 한 부분을 차지하고 있으며, 연료전지는 친환경적이고 효율적인 에너지원으로서 근 미래의 새로운 대체 에너지로서 각광 받으며 여러 분야의 전기장치로 사용될 수 있다. 연료전지는 낮은 출력전압과 높은 출력전류를 갖는 특징이 있으며, 부하에 따라 출력전압이 변화하는 특성이 있기 때문에 연료전지의 사용을 위해서는 다양한 부하조건에서 연료전지와 연동된 승압 또는 강압형 컨버터의 제작이 반드시 필요하다. 본 논문에서는 DSP를 이용하여 컨버터의 디지털 제어가 가능하며, 고정 시비율로 동작하는 LLC 공진형 컨버터를 이용한 2kW급 연료전지용 양방향 컨버터를 제안하였다. 제안한 컨버터는 양방향으로 동작하며, 에너지 저장 및 재사용을 목적으로 하고, 출력은 24V 배터리가 된다.

• Journal of the Korean Institute of Gas
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• v.24 no.6
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• pp.91-97
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• 2020

Lithium-ion batteries (LIBs) have a longer lifespan, higher energy density, and lower self-discharge rates than other batteries, therefore, they are preferred as an Energy Storage System (ESS). However, during years 2017-2019, 28 ESS fire accidents occurred in Korea, and accurate capacity estimation of LIB is essential to ensure safety and reliability during operations. In this study, data-driven modeling that predicts capacity changes according to the charging cycle of LIB was conducted, and developed models were compared their performance for the selection of the optimal machine learning model, which includes the Decision Tree, Ensemble Learning Method, Support Vector Regression, and Gaussian Process Regression (GPR). For model training, lithium battery test data provided by NASA was used, and GPR showed the best prediction performance. Based on this study, we will develop an enhanced LIB capacity prediction and remaining useful life estimation model through additional data training, and improve the performance of anomaly detection and monitoring during operations, enabling safe and stable ESS operations.

• Journal of IKEEE
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• v.19 no.3
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• pp.295-303
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• 2015

Considering to Energy Storage System (ESS) is a global trend In order to reduce global warming and carbon emissions. South Korea has announced various policies to vitalize the development and uptake of renewable energy. South Korea is planning the cumulative capacity of ESS of two million kW in 2020. According to the government support and development of technology companies, the battery of ESS prices are expected to fall gradually. In this paper, we develop a planning model that take into account the supply expansion of technology of ESS and prices. Based on planning model, we analyze the cost of ESS linked with wind power and the revenue for trading electricity and renewable energy certifications.

• Journal of Digital Contents Society
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• v.14 no.4
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• pp.529-536
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• 2013

Lack of proper amount of sun lights and wind strength which are major factors of solar power and wind power system may cause poor electric power generation and decrease the lifetime of batteries that are major energy saving units. Because the PCS, which is essential in solar and wind power system, for small power generation system has been rarely developed an efficient and stable PCS for small power generation system is highly required. In this paper, we design a new constant current/constant voltage type hybrid PCS by which stand alone/grid connected operation with commercial power system is available and implement the designed PCS as a protype for performance verification.

• Journal of the Korean Solar Energy Society
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• v.33 no.4
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• pp.39-45
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• 2013

This paper presents the estimation of minimum BESS capacity for regulating the output of wind farms considering power grid operating condition in Jeju Island. To analyze the characteristics of wind farm outputs with a BESS, the real data of wind farms, Sung-San, Sam-dal and Hang-Won wind farm, located in the eastern part of Jeju island is considered. The wind farms are connected to Sung-san substation to transfer the electric power to Jeju power grid. Consequently, at PCC (Point of Common Coupling), it can see a huge wind farm connected to the substation and thus it can be expected that the smoothing effect is affected by not only the different wind speeds for each area but also the different mechanical inertia of wind turbines. In this paper, two kinds of simulation have been carried out. One is to analyze the real data of wind farm outputs during a winter season, and the other is to connect a virtual BESS to eliminate the unintended generating power changes by the uncontrolled wind farm outputs as shown in the former data. In the conclusion, two kinds of simulation results show that BESS installed in the substation is more efficient than each wind farms with BESS, respectively.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.17 no.2
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• pp.1-10
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• 2021

Lithium-ion batteries with high energy density, long cycle life and other advantages, have been widely used to energy storage systems(ESS). But as ESS fires frequently occur, the safety concern has become the main obstacle that hinders the large-scale applications of lithium-ion batteries. Especially, thermal runaway is the key scientific problem in battery safety research. Therefore, in this study, we performed a numerical analysis on the thermal runaway phenomenon of NCM111, NCM523 and NCM622 batteries using a two-dimensional analysis model. The results show that the two-dimensional simulation results are generally matched with three-dimensional simulation. Also, In the case of NCM111 with a low Ni content in the temperature range used in this study, thermal runaway phenomenon does occurred very slowly, but as the Ni content is increased, the thermal runaway phenomenon occurs rapidly and the thermal stability tends to be decreased. And, in NCM523 and NCM622 batteries, chain reactions occur almost simultaneously, but in the case of NCM111 battery, it is found that after the SEI(Solid Electrolyte Interface) layer decomposition reaction, the cathode-electrolyte reaction is appeared sequentially. After that, the anodic decomposition reaction is increased and leads to the thermal runaway reaction.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.3
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• pp.209-213
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• 2019

Recently, demand for high energy density and long cycling stability of energy storage system has increased for application using with frequency regulation (F/R) in power grid. Supercapacitor have long lifetime and high charge and discharge rate, it is very adaptable to apply a frequency regulation in power grid. Supercapacitor can complement batteries to reduce the size and installation of batteries. Because their utilization in a system can potentially eliminate the need for short-term frequent replacement as required by batteries, hence, saving the resources invested in the upkeep of the whole system or extension of lifecycle of batteries in the long run of power grid. However, low energy density in supercapacitor is critical weakness to utilization for huge energy storage system of power grid. So, it is still far from being able to replace batteries and struggle in meeting the demand for a high energy density. But, today, LIC (Lithium Ion Capacitor) considered as an attractive structure to improve energy density much more than EDLC (Electric double layer capacitor) because LIC has high voltage range up to 3.8 V. But, many aspects of the electrochemical performance of LIC still need to be examined closely in order to apply for commercial use. In this study, in order to improve the capacitance of LIC related with energy density, we designed new method of pre-doping in anode electrode. The electrode in cathode were fabricated in dry room which has a relative humidity under 0.1% and constant electrode thickness over $100{\mu}m$ was manufactured for stable mechanical strength and anode doping. To minimize of contact resistance, fabricated electrode was conducted hot compression process from room temperature to $65^{\circ}C$. We designed various pre-doping method for LIC structure and analyzing the doping mechanism issues. Finally, we suggest new pre-doping method to improve the capacitance and electrochemical stability for LIC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6419-6424
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• 2015

Recently, high-cost energy storage systems are applying to hybrid generation systems with wind turbine and diesel generator in island areas for stable operation. But, this paper proposes an operating algorithm and modeling method of an islanding microgrid that is composed of PMSG(Permanent Magnet Synchronous Generator) and Diesel Generator applied in island areas without such energy storage system. Initially, the operating algorithm was proposed for frequency and voltage to be maintained within the proper ranges for the load and weather change. And then the modeling method were proposed for PMSG, WT-side AC/DC converter and Grid-side DC/AC converter. The proposed operating algorithm and modeling method were applied to a typical islanded microgrid with PMSG wind turbine and diesel generator. The frequency and voltage was kept within the permissible ranges and the proposed method was proven to be appropriate through simulations.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.4
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• pp.444-450
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• 2013

This paper presents the criteria for setting the dynamic operating mode of BESS(Battery Energy Storage System) in the bulk power systems. ESS has been expected to improve the degraded dynamic performance of the power system with high penetration of the renewable resources. While ESS is controlled in steady state or dynamic operating mode for its better effectiveness depending on the operating conditions of power systems, the criteria for setting the dynamic operating mode for the transient period needs to be robust enough to cover all the different conditions. The proposed criteria consider the varying conditions and the operating practices of the bulk power systems.