• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.5
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• pp.463-469
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• 2015

A vibration-based energy harvester and its equivalent circuit models have been reported. Most models predict voltage signals at harmonic excitation. However, vibrations in a natural environment are unpredictable in frequency and amplitude. In this paper, we propose a realistic equivalent circuit model of a frequency-up-converting impact-based piezoelectric energy harvester. It can describe the behavior of the harvester in a real environment where the frequency and the amplitude of the excitation vary arbitrarily. The simulation results of the model were compared with experimental data and showed good agreement. The proposed model can predict both the impact response and long term response in a non-harmonic excitation. The model is also very useful to analyze the performance of energy conversion circuitry with the harvester.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.971-974
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• 2014

Reflect the social concerns of recent energy saving in this paper. The LED market is continuing to grow continuously. But it is now high light energy conversion led lights., We propose converting the light energy-saving method for these LED lights. Generated the cumulative loss of the conversion done at each light change from the current power of the LED lights. The cumulative loss to achieve minimal energy loss resulting from the improved performance.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.6
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• pp.691-698
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• 2015

Recently, the power industry has a great interest in the superconducting energy storage device as a way to maximize energy efficiency to cope with global warming. A superconducting energy storage device can archive maximization of electric energy use efficiency by storing in the form of a magnetic field energy or a kinetic energy without loss a large amount of electrical energy at the non-peak load and then converting it again into electric energy at the peak load. Therefore, in this study, such as the concept of the superconducting energy storage technologies, the present state of its research and development and its applications are surveyed and analyzed to establish methodology applying the superconducting energy storage technologies to power system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.5
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• pp.2048-2053
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• 2011

The aim of this paper is to propose an energy harvesting system by converting mechanical energy of revolving door into electrical energy. The method of energy harvesting system is discussed on two methods: one is the energy-harvester using gear shaft coupling system, and the other is the energy-harvester using spiral spring system. The former is generated by coupling the shaft of rotating door with generator system, while the latter is generated by connecting end-effector of door with the string of generator system. We present the experimental results for two developed energy-harvester. Finally, a comparison between these results is presented to show the validity of energy-harvester.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.827-830
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• 2006

With recent advanced in portable electric devices, wireless sensor, MEMS and bio-Mechanics device, the new typed power supply, not conventional battery but self-powered energy source is needed. Particularly, the system that harvests from their environments are interests for use in self powered devices. For very low powered devices, environmental energy may be enough to use power source. In the generality of cases, these energy harvesting systems are used in the piezoelectric materials as mechanisms to convert mechanical vibration energy into electric energy. Through the piezoelectric materials, the ambient vibration energy could be used to prolong the power supply or in the ideal case provide endless energy f9r the devices. Therefore, the piezoelectric power harvesting cantilever beam is developed. Also, the output voltage and power are predicted in this study. We also discuss the developing system of the piezoelectric energy scavenger. An experimental verification of the model is also performed to ensure its accuracy.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.11
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• pp.1006-1011
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• 2004

Carbon nanotubes have outstanding properties which make them useful for a number of high-technology applications. Especially, single-walled carbon nanotube (SWNT), working under physical conditions (in aqueous solution) and converting electrical energy into mechanical energy directly, can be a good substitute for artificial muscle. The carbon nanotube structure simulated in this paper is an isotropic cantilever type with an adhesive tape which is sandwiched between two SWNTs. For predicting the geometrical and physical parameters such as deflection, slope, bending moment and induced force with various applied voltages, the analytical model for a 3 layer bimorph nanotube actuator is developed by applying Euler-Bernoulli beam theory. The governing equation and boundary conditions are derived from energy Principles. Also, the brief history of carbon nonotube is overviewed and its properties are compared with other functional materials. Moreover, an electro-mechanical coupling coefficient of the carbon nanotube actuator is discussed to identify the electro-mechanical energy efficiency.

• KIEAE Journal
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• v.16 no.2
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• pp.11-16
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• 2016

Purpose: International efforts to save Earth's environment against global warming and environmental pollution have been made in many countries. Energy consumption of buildings has been continuously increasing, and it has been over 40% of total energy consumption in the world. Energy consumption of buildings in Korea reaches 24% of total energy consumption. So, Korea government has executed building energy rating systems to control energy consumption of buildings. Method: This study was carried out to evaluate the energy performance of apartment unit plans according to converting balconies into living areas. For the study, six types of input models were made. Two input models(SP1 and SP 2) were the standard units that balcony areas were not converted into living areas, and four ones(EP 1, EP 2, EP 3 and EP 4) were the extended unit plans that balcony areas were turned into living areas. All of them were simulated with ECO2 software to assess building energy efficiency. Result: According to the results, the energy performance of the EP 2 and EP 4 models were 21. 8% higher than SP 1 model and 9.2% higher than SP 2 model.

• Environmental and Resource Economics Review
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• v.32 no.2
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• pp.127-147
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• 2023

This study is trying to analyze the economic effect of replacing thermal power generation, one of the government's carbon-neutral policies, with new and renewable energy. For this analysis, scenario A is set to replace 100% of thermal power generation with new and renewable energy, and scenario B is set to replace 60% of thermal power generation with new and renewable energy. In addition, costs are incurred when replacing thermal power generation with new and renewable energy, and scenario 1 is the same cost as the current cost, and scenario 2 is120% higher than the current cost. Therefore, when converting thermal power generation to new and renewable energy, the scenarios are largely organized into four cases. In the case of replacing thermal power generation with new and renewable energy, the production inducement coefficient of thermal power generation decreased from the current level regardless of the scenario. However, the value-added inducement coefficient and the greenhouse gas emission inducement coefficient are lower than the current level when thermal power is converted to renewable energy by 100%, while the value-added inducement coefficient and greenhouse gas emission inducement coefficient are higher than the current level. In addition, the greenhouse gas emission induction coefficient of most industries was found to decrease, while the production induction coefficient and the value-added induction coefficient increased. Scenario A seems appropriate because the purpose of the government's policy is to reduce greenhouse gas emissions by converting thermal power into new and renewable energy. However, as a result of this, the production inducement coefficient and value-added inducement coefficient of some industries decrease, so the government's support policy is needed to solve this problem

• Applied Science and Convergence Technology
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• v.23 no.5
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• pp.221-239
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• 2014

The global demand for energy has been increasing since past decades. Various technologies have been working to find a suitable alternative for the generation of sustainable energy. Photovoltaic technologies for solar energy conversion represent one of the significant routes for the green and renewable energy production. Despite of remarkable improvement in solar cell technologies, the generation of power is still suffering with lower energy conversion efficiency, high production cost, etc. The major problem in improving the PV efficiency is spectral mismatch between the incident solar spectrum and bandgap of a semiconductor material used in solar cell. Luminescent materials such as rare-earth doped phosphor materials having the quantum efficiency higher than unity can be helpful for photovoltaic applications. Quantum cutting phosphors are the most suitable candidates for the generation of two or more low-energy photons for the absorption of every incident high-energy photons. The phosphors which are capable of converting UV photon to visible and near-IR (NIR) photon are studied primarily for photovoltaic applications. In this review, we will survey various near IR quantum cutting phosphors with respective to their synthesis method, energy transfer mechanism, nature of activator, sensitizer and dopant materials incorporation and energy conversion efficiency considering their applications in photovoltaics.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.6
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• pp.661-668
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• 2012

Wireless sensor network is one of prospective methods for railway monitoring due to the long-term operation and low-maintenance performances. How to supply power to the wireless sensor nodes has drawn much attention recently. In railway monitoring, the idea of converting ambient vibration energy from vibration of railway track induced by passing trains to electric energy has made it a potential way for powering the wireless sensor nodes. In this paper, a bimorph cantilever piezoelectric energy harvester was designed based on a single degree-of-freedom model. Experimental test was also performed to validate the design. The first natural frequency of the bimorph piezoelectric energy harvester was decreased from 117.1 Hz to 65.2 Hz by adding 4 gram tip mass to the free end of the 8.6 gram energy harvester. In addition, the power generation of the piezoelectric energy harvester with 4 gram tip mass at resonant frequency was increased from 0.14 mW to 0.74 mW from $2.06m/s^2$ base excitation compared to stand-alone piezoelectric energy harvester without tip mass.