• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.425-429
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• 1990

In order to spread the practical utilization of solar energy, it depends upon how we can increase the efficiency of solar energy conversion system. This paper describes the method for calculating of optimal passive elements values in Maximum Solar Energy Tracking System. And experimental results with those calculated values are presented.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.503-512
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• 2012

There is a new power generation system such as direct coal fuel cell (DCFC) with a solid oxide electrolyte operated at relatively high temperature. In the system, it is of great importance to feed coal continuously into anodic electrode surface for its better contact, otherwise it would reduce electrochemical conversion of coal. For that purpose, it is required to improve the electrochemical conversion efficiency by using either rigorous mixing condition such as fluidized bed condition or just by recirculating coal particle itself successively into the reaction zone of the system. In this preliminary study, we followed the second approach to investigate how significantly particle recycle would affect the coal conversion efficiency. As a first phase, coal conversion was analyzed and evaluated from the thermochemical reaction of carbon with air under particle recirculating condition. The coal conversion efficiency was obtained from raw data measured by two different techniques. Effects of temperature and fuel properties on the coal conversion are specifically examined from the thermochemical reaction.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.142-149
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• 2004

This paper presents a neural network controller of a grid-connected wind energy conversion system for extracting maximum power from wind and a power controller to transfer the maximum power extracted into a utility grid. It discusses the modeling and simulation of the wind energy conversion system with the controllers, which consists of an induction generator, a transformer, a link of a rectifier, and an inverter. The paper describes tile drive train model, induction generator model and grid-interface model for dynamics analysis. Maximum power extraction is achieved by controlling the pitch angle of the rotor blades by a neural network controller. Pitch control method is mechanically complicated, but the control performance is better than that of the stall regulation. The simulation results performed on MATLAB show the variation of the generator torque, the generator rotor speed, the pitch angle, and real/reactive power injected into the grid, etc. Based on the simulation results, the effectiveness of the proposed controllers is verified.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.5
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• pp.469-476
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• 2015

The purpose of this work is to investigate main factors to design a solid-state hydrogen stroage system with magnesium hydride with 10 wt% graphite using numerical simulation tools. The heat transfer characteristic of this material was measured in order to perform the highly reliable simulation for this system. Based on the measured effective thermal conductivity, a transient heat and mass transfer simulation revealed that the total performance of hydrogen storage system is prone to depend on heat and mass transfer behaviors of hydrogen storage medium instead of its inherent kinetic rate for hydrogen adsorption. Furthermore, we demonstrate that the thermodynamic aspect between equlibrium presssure and temperature is one of key factor to design the hydrogen storage system with high performance using magnesium hydride.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.6
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• pp.535-542
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• 2013

To enhance the performance of SEWGS system by holding the WGS catalyst in a SEWGS reactor using bed inserts, effect of bed insert geometry on CO conversion of WGS catalyst was measured and investigated. Small scale fluidized bed reactor was used as experimental apparatus and tablet shaped WGS catalyst and sand particle were used as bed materials. The cylinder type and the spring type bed inserts were used to hold the WGS catalysts. The CO conversion of WGS catalyst with the change of steam/CO ratio was determined based on the exit gas analysis. Moreover, gas flow direction was confirmed by bed pressure drop measurement for each case. The measured CO conversion using the bed inserts showed high value comparable to previous results even though at low catalyst content. Most of input gas flowed through the bed center side when we charged tablet type catalyst into the cylinder type bed insert and this can cause low $CO_2$ capture efficiency because the possibility of contact between input gas and $CO_2$ absorbent is low in this case. However, the spring type bed insert showed good reactivity and good distribution of gas, and therefore, the spring type bed insert was selected as the best bed insert for SEWGS process.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2743-2750
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• 2011

Lanthanide(III)-cored complex as a wavelength conversion material has been successfully designed and synthesized for highly efficient dye-sensitized solar cells, for the first time, since light with a short wavelength has not been effectively used for generating electric power owing to the limited absorption of these DSSCs in the UV region. A black dye (BD) was chosen and used as a sensitizer, because BD has a relatively weak light absorption at shorter wavelengths. The overall conversion efficiency of the BD/WCM device was remarkably increased, even with the relatively small amount of WCM added to the device. The enhancement in $V_{oc}$ by WCM, like DCA, could be correlated with the suppression of electron recombination between the injected electrons and $I_3{^-}$ ions. Furthermore, the short-circuit current density was significantly increased by WCM with a strong UV light-harvesting effect. The energy transfer from the Eu(III)-cored complex to the $TiO_2$ film occurred via the dye, so the number of electrons injected into the $TiO_2$ surface increased, i.e., the short-circuit current density was increased. As a result, BD/WCM-sensitized solar cells exhibit superior device performance with the enhanced conversion efficiency by a factor of 1.22 under AM 1.5 sunlight: The photovoltaic performance of the BD/WCM-based DSSC exhibited remarkably high values, $J_{sc}$ of 17.72 mA/$cm^2$, $V_{oc}$ of 720 mV, and a conversion efficiency of 9.28% at 100 mW $cm^{-2}$, compared to a standard DSSC with $J_{sc}$ of 15.53 mA/$cm^2$, $V_{oc}$ of 689 mV, and a conversion efficiency of 7.58% at 100 mW $cm^{-2}$. Therefore, the Eu(III)-cored complex is a promising candidate as a new wavelength conversion coadsorbent for highly efficient dye-sensitized solar cells to improve UV light harvesting through energy transfer processes. The abstract should be a single paragraph which summaries the content of the article.

• New & Renewable Energy
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• v.7 no.2
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• pp.10-17
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• 2011

Korea is the 11th largest energy consumption country and 96% of its total energy consumption depends on imports from overseas. Therefore it is a very important task to secure renewable energy sources which can reduce both the carbon-dioxide emission and dependency on overseas energy imports. Among the various renewable energy sources, organic wastes are important sources. In Korea, 113 million toe of methane is generated from organic wastes annually, but only 3.7% is effectively used for energy conversion. Thus, it is very important to make better use of organic wastes, especially for power generation. The goals of this project are to develope the fuel supplying system of Bio Gasturbine (GT) for 5MW-class co-generation system. The fuel supplying system mainly consists of $H_2S$ removal system, Bio Gas compression system, Siloxane removal system and moisture separating systems. The fuel requirement of 5MW-class GT is at around 60% of $CH_4$, $H_2S$ (<30 ppm), Siloxane(<10 mg/$nm^3$) and supply pressure (> 25 bar) from biogas compressor. Main mechnical charateristics of Bio Gasturbine system have the specific performance; 1) high speed turbine speed (12,840 rpm) 2) very clean emmission NOx (<50 ppm) 3) high efficiency of energy conversion rate. This paper focuses on the development of design technology for food waste biogas pretreatment system for 5MW-class biogas turbine. The study also has the plan to replace the fuel of gas turbine and other distributed power systems. As the increase of bioenergy, this system help to contribute to spread more New & Renewable Energy and the establishment of Renewable Portfolio Standards (RPS) for Korea.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.8
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• pp.543-548
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• 2011

New concept of wind energy conversion system is proposed to increase the energy density at a given working space. The quality of wind for wind power generation is depend on its direction and speed. However, the quality is not good on land because wind direction is changeable all the time and the speed as well. The most popularly operated wind turbine system is an axial-flow free turbine. But its conversion efficiency is less than 30% and even less than 20% considering the operating time. In this research, a cross-flow type wind turbine system is proposed with a convergent-divergent duct system to accelerate the low speed wind at the inlet of the wind turbine. Inlet guide vane is also introduced to the wind turbine system to have continuous power generation under the change of wind direction. In here, the availability of wind energy generation is evaluated with the change of the size of the inlet guide vane and the optimum geometry of the turbine impeller blade was found for the innovative wind power generation system.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.79-79
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• 2011

The oceans are an untapped resource, capable of making a major contribution to our future energy needs. In the search for a non polluting renewable energy source, there is a push to find an economical way to harness energy from the ocean. Tidal stream is one of ocean energy form that is being investigated as potential source for power generation. Tidal current turbines are therefore designed as conversion machinery to generate power from tidal currents. A study on energy extraction from tidal currents is presented in this paper.

• Transactions of the Korean hydrogen and new energy society
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• v.17 no.3
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• pp.293-300
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• 2006

KIER has been developing a Ru-based preferential oxidation catalysts and a novel fuel processing system to provide hydrogen rich gas to residential PEMFCs system. The catalytic activity of Ru-based catalysts was investigated at different Ru loading amount and different support structure. The obtained result indicated that 2 wt% loaded Ru-based catalyst supported on ${\alpha}-Al_2O_3$ showed high activity in low temperature range and suppressed the methanation reaction. The developed prototype fuel processor showed thermal efficiency of 78% as a HHV basis with methane conversion of 92%. CO concentration below 10 ppm in the produced gas is achieved with separate preferential oxidation unit under the condition of $[O_2]/[CO]=2.0$. The partial load operation have been carried out to test the performance of fuel processor from 40% to 80% load, showing stable methane conversion and CO concentration below 10 ppm. The durability test for the daily start-stop and 8 h operation procedure is under investigation and shows no deterioration of its performance after 50 start-stop cycles. In addition to the system design and development.