• Journal of Biosystems Engineering
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• v.20 no.3
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• pp.275-287
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• 1995

The rice processing complex(RPC) consisted of the rice handling, drying, storage, and milling processes. It has been established at 83 locations domestically by April 1994, and 200 of RPC will be built more throughout the country. Therefore, this study has been performed to achieve two objectives as the followings : 1) Development of mathematical models which can assess the requirement of electricity, fuel, and labor for four model systems of rice processing complex. 2) Development of a computer simulation model which produce the improved designs of RPC by the evaluation results of energy requirements of four RPC models. The results from this study are summarized as follows : 1) Mathematical models were developed on the basis of result of mass balance analysis and required power of machines for each process. 2) A computer simulation model was developed, which can produce the improved designs of RPC by the evaluation results of energy requirements. The computer simulation model language was BORLAND $C^{++}$. 3) The results of simulation showed that total energy requirements were ranged from 75.94㎾h/t to 124.30㎾h/t. 4) From the results of computer analysis of energy requirement classified by drying type, it was found that energy requirement of the drying type A{paddy rice (PR) for storage-natural air drying(15%), PR for milling-heated air drying(16%)} were less than that of the drying type B{1 step-natural air drying(PR for storage : 18%, PR for milling : 20%), 2 step-heated air drying(PR for storage : 15%, PR for milling : 16%)}. 5) The energy efficient drying method is that all the incoming rough rice to RPC should be dried by national air drying systems. If it is more than the capacity of national air drying system, the amount of surplus rough rice is recommended to be dried by the heated air drying method.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.505-510
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• 1996

A simple model for RAM (Reliability, Availability and Maintainability) analysis and its computer code are developed for application to DUPIC fuel fabrication system. The approach is obtained by linking the allocation model (top-down method) to bottom-up method for RAM analysis. As a result, the availability requirement of subsystem, as well as the buffer storage requirement between processes, are evaluated for the DUPIC facility..

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.7
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• pp.1161-1168
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• 2016

Battery energy storage system(BESS) attract the attention of the power system operators with its fast response to a disturbance in spite of its limited energy capacity. This paper proposes the operating method of BESS for following the Automatic Generation Control(AGC) frequency control which is centrally distributed by a system operator. As BESS needs to just meet the control requirement from the system operator, it should be able to properly manage the state of charge(SOC) of BESS to be available to control signal. For doing these, the proposed method distributes the control requirement to available batteries in proportion to its SOC. In addition, unavailable batteries are controlled to recover the SOC to an appropriate range, and the recovering power is supplied by available batteries meeting the control requirement. Moreover, the proposed method manages the efficiency of power conversion system (PCS) by limiting the number of PCS to be assigned for the low control requirement. Finally, the case studies are carried out to verify the effectiveness of proposed strategy.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.726-737
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• 2017

The use of energy storage systems (ESSs) has become a feasible solution to solve the wind power intermittency issue. However, the use of ESSs increases the system cost significantly. In this paper, an optimal power flow control scheme to minimize the ESS capacity is proposed by using the zero-phase delay low-pass filter which can eliminate the phase delay between the dispatch power and the wind power. In addition, the filter time constant is optimized at the beginning of each dispatching interval to ensure the fluctuation mitigation requirement imposed by the grid code with a minimal ESS capacity. And also, a short-term power dispatch control algorithm is developed suitable for the proposed power dispatch based on the zero-phase delay low-pass filter with the predetermined ESS capacity. In order to verify the effectiveness of the proposed power management approach, case studies are carried out by using a 3-MW wind turbine with real wind speed data measured on Jeju Island.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.7
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• pp.1237-1241
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• 2010

Supercapacitors as novel energy storage devices between conventional capacitors and batteries, with more specific capacitance and energy densities than conventional capacitors and more power densities than batteries are to be used in many fields. Supercapacitor is regarded as one of good alternatives for meeting the requirement of market with excellent power performance and high cyclability. This paper deals with the characteristics of charge and discharge behavior of supercapacitor module for developing 42V hybrid energy storage system with lead acid battery and supercapacitor in order to adopt to 42V power net for vehicle. An analysis performed in this paper indicates that supercapacitor storage system may be cost effective for high cycle applications.

• Korean Journal of Food Science and Technology
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• v.22 no.4
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• pp.434-438
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• 1990

With adding cryoprotectants to red pepper paste and strawberry pulp, the effects of freezing point depression and the energy requirement for storage at $-15^{\circ}C$ were studied. In case of red pepper paste, the freezing point was pressed to $-9.6^{\circ}C$ by adding NaCl(15% w/w) and citric acid after removing stem. And the components of combined cryoprotectants to keep strawberry pulp in the unforzen state at $-15^{\circ}C$ were dextrose(25% w/'w), fructose(17% w/w) sorbitol(8% w/w) and ascorbic acid(0.2%, w/w). Also, when compared with No-treatment, the storage time reduced about 50% and resulted in about $70{\sim}80%$ cut-down in the energy requirement for storage of food products at low-temperature.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.3
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• pp.247-254
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• 2022

Slush hydrogen containing liquid and solid hydrogen is expected to achieve zero boil-off by suppressing boil-off gas because heat of fusion for solid absorbe the heat ingress from atmosphere. In this paper, quantitative analysis on storage cost considering specific energy consumption between 1,000 m³ class liquid hydrogen storage system with re-liquefaction and slush hydrogen storage system during equivalent zero boil off period. Even though approximately 50% of total storage capacity should be converted into solid phase during the initial cargo bunkering, total energy consumption to convert into slush hydrogen is relatively 25% less than re-liquefaction energy for boil off hydrogen during zero boil off period. That's because energy consumption of slush phase change take up only 1.8% of liquefaction energy. moreover, annual revenue requirement including CAPEX, OPEX and electric cost for slush hydrogen storage could be more reduced approximately 32.5% than those of liquid hydrogen storage and specific energy storage cost ($/kg-H₂) could also be lowered by about 41.7% compared with liquid hydrogen storage.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.151-156
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• 2000

A vibration in a high-speed machine may lead to machinery malfunction and even catastrophic failure. So solving the vibration problem is a fundamental requirement for the stability of the high-speed machine. The flywheel energy storage system using superconducting magnetic bearings is a device to store electrical energy as rotational kinetic energy by motor and to convert it to electrical by generator when necessary. The high-speed rotating flywheel has large amplitude at a critical speed. And it has an unstable behavior by the electric torque at the first stage of the energy generation. In this paper, the stability analysis is performed with an analytical model and equations of motion-which is considered the effect of the electric torque-to identify the stable driving condition and the dynamic behavior.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.1
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• pp.65-69
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• 2010

Supercapacitors as novel energy storage devices between conventional capacitors and batteries, with more specific capacitance and energy densities than conventional capacitors and more power densities than batteries are to be used in many fields. And, social demand on fuel economy and reducing pollution needs equipment of new function such as energy storage system with good power performance, high cyclability and good energy efficiency. Supercapacitor is regarded as one of good alternatives for meeting the requirement of market with excellent power performance and high cyclability. This paper deals with the fundamental characteristics of supercapacitor unit and charge and discharge behavior of supercapacitor module for developing 42V hybrid energy storage system with lead acid battery and supercapacitor in order to adopt to 42V power net for vehicle.

• Journal of Electrical Engineering and Technology
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• v.6 no.4
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• pp.447-458
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• 2011

In this paper, a novel flywheel energy storage device, called the flexible power conditioner, which integrates both the characteristics of the flywheel energy storage and the doubly-fed induction machine, is proposed to improve power system stability. A prototype is developed and its principle, composition, and design are described in detail. The control system is investigated and the operating characteristics are analyzed. The test results based on the prototype are presented and evaluated. The test results illustrate that the prototype meets the design requirement on power regulation and starting, and provides a cost-effective and effective means to improve power system stability.