• Proceedings of the KIEE Conference
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• 1989.11a
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• pp.216-219
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• 1989

Over the last decade or so, there has been an increase in activity devoted to the development of renewable resources for generating electric energy. Many of these generators are small and can only be economically connected to the distribution system or to ths subtransmission system. Those which involve storage, a secondary source of energy, can provide a means to achieve more efficient use of existing generating plant. Such systems are known collectively as Dispersed Storage and Generation devices, or DSGs. So, in this paper, for uninterruptable service in one bank outage in 154/22.9KV substation, the proper capacity of DSGs is examined through the configuration and the reliability.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.1-6
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• 2017

Total capacity of pumped hydro storage(PHS) in Korean power system reaches 4,700MW, though the share of it is about 4.56% of total capacity The Unit Commitment program, E-terracommit which is used for the operational purpose by KPX, includes the PHS model. But the model has a defect that it does not include the information of water level of upper reservoir. Therefore two types of improved the PHS models are represented in this paper. The first model is a optimized model by connecting the upper reservoir water level to the non-spinning reserve. The other model is to have priority allocate both the PHS and combined cycle generator for non-spinning reserve. The proposed two models and the E-terracommit model is compared and resulting to have improvement in estimating non-spinning reserve when using the proposed models.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.208-213
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• 2015

This study presents the estimation method for the optimal capacity of BESS(Battery Energy Storage System) in order to reduce the electric charges of common consumer. The daily optimal charge and discharge plan of BESS which satisfies the given constraints is established using linear programming through the change of rated output/rated capacity of the time that shows the electric charges in the highest reduced rate has been selected. There will be a problem to compare only reduced rate because the bigger the rated capacity, the more reduced rate is increased. Therefore, rated output/rated capacity of the time when the reduced amount of electric charges for a year is higher than the investment cost of BESS was selected.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.979-986
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• 2016

At present, electric power industry around the world are being gradually changed to a new paradigm, such as electrical energy storage system, the wireless power transmission. Demand for ESS, the core technology of the new paradigm, has been growing worldwide. However, it is essential to estimate the optimal capacity of ESS facilities for frequency regulation because the benefit would be saturated in accordance with the investment moment and the increase of total invested capacity of ESS facilities. Hence, in this paper, the annual optimal mathematical investment model is proposed to estimate the optimal capacity and to establish investment plan of ESS facility for frequency regulation. The optimal mathematical investment model is newly established for each season, because the construction period is short and the operation effect for the load by seasons is different unlike previous the mathematical investment model. Additionally, the marginal operating cost is found by new mathematical operation model considering no-load cost and start-up cost as step functions improving the previous mathematical operation model. ESS optimal capacity is established by use value in use iterative methods. In this case, ESS facilities cost is used in terms of the value of the beginning of the year.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.5
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• pp.207-217
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• 2018

Recently, the importance of energy demand management, particularly peak load control, has been increasing due to the policy changes of the Second Energy Basic Plan. Even though the installation of distributed generation systems such as Photovoltaic and energy storage systems (ESS) are encouraged, high initial installation costs make it difficult to expand their supply. In this study, the power consumption of a university building was measured in real time and the measured power consumption data was used to calculate the optimal installation capacity of the Photovoltaic and ESS, respectively. In order to calculate the optimal capacity, it is necessary to analyze the operation methods of the Photovoltaic and ESS while considering the KEPCO electricity billing system, power consumption patterns of the building, installation costs of the Photovoltaic and ESS, estimated savings on electric charges, and life time. In this study, the power consumption of the university building with a daily power consumption of approximately 200kWh and a peak power of approximately 20kW was measured per minute. An economic analysis conducted using these measured data showed that the optimal capacity was approximately 30kW for Photovoltaic and approximately 7kWh for ESS.

• Journal of the Korean Solar Energy Society
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• v.34 no.1
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• pp.81-90
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• 2014

The Jeju-Korea power system is a small-sized network with a system demand ranging from a autumn minimum of 350MW to a summer peak of 716MW. Because Jeju island is well exposed to north-east winds with high speed, applications to connect to Jeju power system are flooded. Considering physical/environmental constraints, Jeju Self-governing Province has also target for the wind power capacity of 1,350MW by 2020. It amounts to two or three times of Jeju average-demand power and wind power limit capacity announced by Korea Power Exchange (KPX) company. Wind farm connection agreements will be signed to maximize utilization of wind resource. In spite of submarine cable HVDC connected to Korea mainland, Jeju power system is independently operated by frequency and reserve control. This study reevaluates wind power limit based on the KPX criteria from 2016 to 2020. First of all wind power generation limit are affected by off-peak demand in Jeju power system. Also the possibility capacity rate of charging wind power output is evaluated by using energy storage system (ESS). As a result, in case of using 110MWh ESS, wind power limit increases 33~55MW(30~50% of ESS), wind power constraint energy decreases from 68,539MWh to 50,301MWh and wind farm capacity factor increases from 25.9 to 26.1% in 2020.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.2_2
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• pp.209-218
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• 2022

The purpose of this study is to analyze an economic assessment of PV-ESS systems based on the power generation performance data of solar power (PV) operating in domestic area, and to calculate the optimal capacity of the energy storage system. In this study, PVs in Gyeonggi-do, Jeollabuk-do, and Gyeongsangbuk-do were targeted, and PVs in this area were assumed to be installed on a general site, and the research was conducted by applying weights based on the facility's capacity. All the analysis was conducted using the actual amount of KPX transactions of PVs in 2019. In order to calculate the optimal capacity of PCS and BESS according to GHI, PV with a minimum/maximum/central value was selected by comparing the solar radiation before the horizontal plane between three years (2017-2019) of the location where PV was installed. As a result of the analysis, in Gyeonggi-do, if the REC weight decreases to 3.4 when there is no change in the cost of installing BESS and PCS, it is more economical to link BESS than PV alone operation of PV. In Jeollabuk-do, it was analyzed that if the REC weight was reduced to 3.6, it was more likely to link BESS than PV operated alone. In Gyeongsangbuk-do, it was analyzed that if the REC weight was reduced to 3.4, it was more likely to link BESS than PV operated alone.

• Carbon letters
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• v.12 no.2
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• pp.112-115
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• 2011

The scope of this work investigates the relationship between the amount of oxygen-functional groups and hydrogen adsorption capacity with different concentrations of phosphoric acid. The amount of oxygen-functional groups of activated carbons (ACs) is characterized by X-ray photoelectron spectroscopy. The effects of chemical treatments on the pore structures of ACs are investigated by $N_2$/77 K adsorption isotherms. The hydrogen adsorption capacity is measured by $H_2$ isothermal adsorption at 298 K and 100 bar. In the results, the specific surface area and pore volume slightly decreased with the chemical treatments due to the pore collapsing behaviors, but the hydrogen storage capacity was increased by the oxygen-functional group characteristics of AC surfaces, resulting from enhanced electron acceptor-donor interaction at interfaces.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.7
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• pp.1-10
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• 2003

In order to analyze the water supply capacity in an estuary reservoir, a system composed of daily water balance model and daily inflow model was developed. The agricultural water demands to paddy fields, domestic water demands to residential areas, and industrial water demands to industrial complexes were considered in this daily water balance model. Likewise, the outflow volume through sluice gates and inside the water level at the start of the outflow was initially conditioned to simulate estuary reservoir storage. The DAWAST model (Noh, 1991) was selected to simulate daily estuary reservoir inflow, wherein return flows from agricultural, domestic, and industrial water were included to simulate runoff. Using this system, the water supply capacity in the Geum River estuary reservoir was analyzed.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1596-1600
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• 2010

Surface functionalization of multi-walled carbon nanotubes (MWNTs) was carried out by means of acid treatment. The presence of oxygen functional groups on the surface of acid-treated MWNTs was confirmed with the aid of Fourier transform infrared spectroscopy and X-ray spectroscopy. In addition, carboxylic groups generally formed on the surface of acid-treated MWNTs, and the dispersion was increased by the duration of the acid treatment. The zeta-potential indicated the surface charge transfer and the dispersion of MWMTs. Morphological characteristics of acid-treated MWNTs were also observed using a transmission electron microscopy, X-ray diffraction, and Raman analysis, which was revealed the significantly unchanged morphologies of MWNTs by acid treatment. The hydrogen adsorption capacity of the MWNTs was evaluated by means of adsorption isotherms at 77 K/1 atm. The hydrogen storage capacity was dependent upon the acid treatment conditions and the formation of oxygen functional groups on the MWNT surfaces. The latter have an important effect on the hydrogen storage capacity.