• Journal of Korea Society of Digital Industry and Information Management
• /
• v.12 no.3
• /
• pp.231-257
• /
• 2016

Several efforts to replace the use of existing fossil energy resources have already been made around the world. As a result, a new industry of renewable energy has been created, and efficient energy distribution and storage has been promoted intensively. Among the newly explored renewable energy sources, the most widely used one is solar energy generation, which has a high market potential. An energy storage system (ESS) is a system as required. In this paper, the design and implementation of an ESS for the efficient use of power in stand-alone street lights is presented. In current ESS applied to stand-alone street lights, either 12V~24V DC (from solar power) or 110V~220V AC (from commercial power) is used to recharge power in systems with lithium batteries. In this study, an ESS that can support both solar power and commercial power was designed and implemented; it can also perform emergency recharge of portable devices from solar powered street lights. This system can maximize the scalability of ESSes using lithium batteries with efficient energy conversion, with the advantage of being an eco-friendly technology. In a ripple effect, it can also be applied to smart grids, electric vehicles, and new, renewable storage markets where energy storage technology is required.

• Journal of the Korean Solar Energy Society
• /
• v.30 no.1
• /
• pp.1-6
• /
• 2010

Generally, the building's windows and ventilation for the purpose of mining and the vista and windows by emotional engineering design area is a growing trend.In addition, the building regulation U-value limitation of window is $3.3W/m^2{\cdot}K$ in southern regions, while U-value limitation of wall is $0.35{\sim}0.58W/m^2{\cdot}K$. It means that the energy loss through windows is six times more than it through wall. Therefore, the purpose of this study is to evaluate the environmental performance of the super window system by verification experiment. The results of this study are as follows; 1) The insulation performance of super window system is $1.44\;W/m^2^{\circ}C$ 2) Super Window compared to a normal window reduce heating energy requirements have been 5.3% 3) Compared to a normal window, Super window savings rate was 4.1% lower 4) Building energy efficiency rating was up to 1 rating from 2 rating.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.15 no.3
• /
• pp.155-161
• /
• 2015

Efficient energy consumption is a one of the key issues in wireless sensor networks. Clustering-based routing algorithms have been popular solutions for such an issue. Re-clustering is necessary for avoiding early energy drain of cluster head nodes in such routing strategies. The re-clustering process itself, however, is another source of energy consumption. It is suggested in this work to adaptively set the frequency of re-clustering by comparing the energy levels of cluster heads and a threshold value. The algorithm keeps the clusters if all the cluster heads' energy levels are greater than the threshold value. We confirm through simulations that the suggested algorithm shows better energy efficiency than the existing solutions.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.10
• /
• pp.1479-1484
• /
• 2014

This paper deals with regenerative energy in railway system which one of the largest customer in terms of load capability. Unlike the other loads of power system, loads of railway systems change in time and space. It has a characteristic amount of generating regenerative energy by frequent starting and braking in railway system. Therefore, it is expected higher utilization in railway system than the other systems. The purpose of DC power supply simulation is analyzing backed energy, regenerative energy by each railway vehicle and substation. In this paper, regenerative energy utilization are analyzed using DC power supply simulation and it is performed changing major influence on the design such as the number of installing absorber, internal resistance value, no-load voltage value at substation or operating parameters at regenerative energy utilization. After simulating, results are compared and analyzed.

• Journal of the Korea Safety Management & Science
• /
• v.24 no.3
• /
• pp.75-84
• /
• 2022

While protecting its lives and property from natural disasters such as floods and droughts, North Korea needs to develop into an informationized industrial society by securing renewable energy power in the era of energy transition. In addition, existing research has considered that a policy of continuous and consistent expansion of renewable energy based on the safety of the lives of ordinary people could be the solution. South Korea needs to recognize that the supply of energy for a minimum of living is more important to the North Korean people than the economic benefits of securing North Korea's renewable energy market. Therefore, in this paper, from that point of view, we have calculated the amount of electricity that North Korea lacks necessary for the lives of its inhabitants that can be replaced by renewable energy, and considered ways to estimate the market value.

• Asian-Australasian Journal of Animal Sciences
• /
• v.15 no.1
• /
• pp.55-60
• /
• 2002

A metabolism trial with four castrated male Brahman cattle, average body weight 320 kg, was conducted in order to determine the nutritive value of chopped sugarcane stalk (CSS) for the establishment of feeding strategy in the dry season in Northeast Thailand. Animals were subjected to the following four dietary treatments: Treatment 1; 100% of CSS, Treatment 2; 70% of CSS and 30% of commercial complete feed (TMR), Treatment 3; 40% of CSS and 60% of TMR, and Treatment 4; 100% of TMR. The average CP, ether extracts, nitrogen free extracts, crude fiber and ash contents of CSS were 2.0, 0.9, 79.0, 16.1 and 2.2%, respectively. Although the amount of feed given was approximately at maintenance level, animals in treatments 1 and 2 refused a part of feed. The metabolism trial revealed that total digestible nutrient and metabolizable energy contents of CSS were 61.5% and 9.04 MJ/kgDM, respectively, when it was properly supplemented with protein sources. Nutritive value of CSS was lowered when animals were given CSS solely. This was due to the large loss of energy into urine and methane. Voluntary intake of CSS in cattle was not enough to satisfy energy requirement for maintenance. The CSS can be used as a roughage for feeding cattle in the dry season with proper supplementation of protein and energy.

• Computers and Concrete
• /
• v.20 no.5
• /
• pp.539-544
• /
• 2017

Shear walls have high stiffness and strength; however, they lack energy dissipation and repairability. In this study, an innovative slotted shear wall featuring vertical slots and steel energy dissipation connectors was developed. The ductility and energy dissipation of the shear wall were improved, while sufficient bearing capacity and structural stiffness were retained. Furthermore, the slotted shear wall does not support vertical forces, and thus it does not have to be arranged continuously along the height of the structure, leading to a much free arrangement of the shear wall. A frame-slotted shear wall structure that combines the conventional frame structure and the innovative shear wall was developed. To investigate the ductility and hysteretic behavior of the slotted shear wall, finite element models of two walls with different steel connectors were built, and pushover and quasi-static analyses were conducted. Numerical analysis results indicated that the deformability and energy dissipation were guaranteed only if the steel connectors yielded before plastic hinges in the wall limbs were formed. Finally, a modified D-value method was proposed to estimate the bearing capacity and stiffness of the slotted shear wall. In this method, the wall limbs are analogous to columns and the connectors are analogous to beams. Results obtained from the modified D-value method were compared with those obtained from the finite element analysis. It was found that the internal force and stiffness estimated with the modified D-value method agreed well with those obtained from the finite element analysis.

• Journal of the Korean Solar Energy Society
• /
• v.30 no.6
• /
• pp.118-124
• /
• 2010

In order to develop commercial model of 10kW dish-Stirling solar thermal power system, modification for the exiting facility was taken for a year as a Leading Project in KIER. During the project, solar tracking system, control and monitoring system and high durability reflector were developed and long term operation were performed. The solar tracking system was tested for four months to investigate the degree of precision and adapted to the control system for an actual operation from October in 2009. The sun tracking accuracy of ${\pm}4$ mrad using modified control system was obtained and the system operated successfully during the experimental period. The monitoring system displays engine pressure, electric generation amounts, generator RPM, receiver temperatures, and etc. from Stirling engine and weather data of Direct Normal Irradiation, Horizontal Global Insolation, wind speed & direction, and atmosphere temperature from weather station. According to the operating results in a clear sky day, electric power of 6,890 W was generated at the DNI value of 850 W/$m^2$ and the averaged solar-to-electricity efficiency during a whole day reached to 18.99%. From the overall operating results, linear power generation trend could be observed with increasing DNI value. The solar-to-electricity efficiency achieved to 19% around the DNI value of 700 W/$m^2$ and increased to 20% when the DNI value goes up to 900 W/$m^2$.

• Environmental and Resource Economics Review
• /
• v.31 no.1
• /
• pp.51-83
• /
• 2022

Renewable Portfolio Standards (RPS), one of the most commonly adopted regulation for renewable energy expansion since 2012, has the obvious advantage of inducing competition in power generation source and alleviating the government's financial burden. However, the abuse of credit multipliers and the use of national Renewable Energy Credits (RECs) have resulted in the distortion of RPS as a quantitative control policy. Just as no face value 10 years ago can hold its real value, this paper highlights for the first time that 27.8% of total renewable obligations over the total RPS period were not actually met due to REC inflation and the consequent decline in the value of renewable energy generation. In addition, the distortion of face/real value of REC causes problems in interoperability with other government policies such as RE100 and Emission Trading System.

• Journal of the Korean Society of Safety
• /
• v.17 no.2
• /
• pp.92-99
• /
• 2002

Safety-related motor operated valve(MOV) safety significance for Ulchin Unit 3 was categorized. The safety evaluation of MOV of domestic nuclear power plants affects the generic data used for the quantification of MOV common cause failure(CCF) events in Ulchin Units 3&4 PSA. Therefore, in this paper, MGL(multiple greek letter)parameter ${\beta}$, used for the evaluation of MOV CCF probabilities in Ulchin Units 3&4 probabilistic safety assessment(PSA), was re-estimated and the MOV safety significance was categorized. The re-estimation results of MGL parameter show that the value of(is decreased by 30% compared with the current value used in Ulchin Unit 3&4 PSA. The categorization results of MOV safety significance using the changed value of MGL parameter(show that the number of HSSCs(high safety significant components) is decreased by 54.5% compared with those using the current value of it used in Ulchin Units 3&4 PSA.