한국태양에너지학회:학술대회논문집
The Korean Solar Energy Society (KSES)
- Semi Annual
Domain
- Energy/Resources > New and Renewable Energy
2011.04a
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In this paper, I suggested the energy flexibility for photovoltaic energy. The cost for PV is surely high. But renewable energy is an one of the key solution for next energy resource. The latest technology needs more electricity. So many people are carrying more mobile charge in their batteries. Looking at the poor country people and nation, it is necessary to supply and share the advanced energy resources like photo voltaic. So in this open seminary I want to share the idea for this theme. The detail discussion will be shown in the following paper.
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There are some degradation factors for amorphous silicon solar cells. Light inducing is one of the factor that explained by Staebler-Wronski effect. Also, hotspot heating could be the reason that makes amorphous silicon solar cell degrade. Hotspot heating is occurred when a solar cell is shaded so this work is investigated into two types of shading condition and how these affect to solar cell differently. Reduced irradiance for whole cell and partially shaded as 0(
$W/m^2$ ) while the other part of cell is soaking as 1000($W/m^2$ ) of irradiance are two conditions that are experimented. The two types of shading show different characteristics of degradations. The result shows that partially shaded cell dropped maximum powerless and slower. Also sudden drop points have shown that should be concerned to decide the number of cells for a string. Otherwise, the current through a shaded cell might flow more than cell's capability. It makes cell and module damaged. This work would help to manufacture modules. -
In this paper, I performed the IEC test in crystalline photovoltaic module described in test standard. And sometimes I changed the test sequence and impact factors for testing modules. Comparing the current test trees in IEC 61215, some ideas are suggested in proper test sequence to guarantee the long-term durability for 25 years.. The detail discussion will be shown in the following paper.
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Song, Young-Hun;Ji, Yand-Geun;Kim, Kyung-Soo;Kang, Gi-Hwan;Yu, Gwon-Jong;Ahn, Hyung-Gun;Han, Deuk-Young 25
In this paper, we analyzed the electrical characteristics with Micro-cracks in Photovoltaic module. Micro cracks are increasing the breakage risk over the whole value chine from the wafer to the finished module, because the wafer or cell is exposed to mechanical stress. And The solar cells have to with stand the stress under out door operation in the finished module. Here the mechanical stress is induced by temperature changes and mechanical loads from wind and snow. So, we experimentally analyze the direct impact of micro-cracks on the module power and the consequences after artificial aging. The first step, we made micro-cracks in PV module by mechanical load test according to IEC 61215. Next, PV modules applied the thermal cycling test, because micro-cracks accelerated aging by thermal cycling test, according to IEC61215. Before every test, we checked output and EL image of PV module. As the result of first step, we detected little power loss(0.9%). But after thermal cycling test increased power loss about 3.2%. -
Photovoltaic modules are well known to be one of the most eco generation of electricity. But usually study solar cell. Otherwise, PV modules are also important in power generation. We have to check other subsidiary materials. In this work benefit of using optically superior encapsulation materials(EVA) in generation temperature is demonstrated. Optical characterization of three EVA products demonstrates reduced transmission in the visible ray region of the solar spectrum. It will have a decisive effect to the module efficiency. Test is shown reduction of reflectance and transmittance. Reflections is dependent on the low iron glass. It can be seen between a specific wave length(240~350mm) about 1%. Transmittance in the entire ray region of light is markedly reduced to depending on the temperature rise. The graph is shown optical properties on EVA. Transmission was reduced. about 1%.
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BIPV system that can alternate building envelope by making materials of PV module should be considered in initial design step for applying PV system efficiently in office building. Mean while, area of the building skin also increases as the number of floors increases, but the valid area that can apply BIPV system in effect decreases relatively. Despite of this weak point, installing BIPV system is still being evaluated as the only measure left that can reduce electronic energy consumption in the building. Therefore, the impact on building energy consumption according to the increase of the number of floors when BIPV system is applied in the building was analyzed. And it will be used as basic information for application of BIPV in office building. Conomic about application of BIPV is interpreted to be secured within the 10 story high. Forover the 11 floors, the methods of increasing the contribution ratio produced by BIPV system through the optimization of install angle and increase in install area of south, high efficiency should be considered. The ways to reduce basic load by integrated design with another renewable energy besides BIPV should be found. Later, the study on the total building energy comsumption with PV generation according to the various type of the basic load and ratio of the width and depth will be performed based on this study.
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This study aims to choose installation location of wind power system and analyze influence factors of wind power system by shape of super high-raise building by using CFD simulation. As a result of this study, wind power system is more applicable to streamlined building than normal building. Round openings are seemed to be the most efficient shape for building integrated wind power system in types applying venturi effect. Safety and vibration should be considered in the case of application of wind power system between the buildings.
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In this study, it is to verify the applicability for a simplified model(IEC61400-2, Design Require-ments for Small Wind Turbines, 2006-03) is the international standard is used to the structural design. In the design process of a wind turbine, the safety of a designed wind turbine is one of the most important factors. The simplified model can be used to determine the design load for small wind turbines. So, this paper has been re-evaluated a small wind turbine design loads that produced already. As a result, the material characteristic value(Rchar) of Blade, Rotor shaft and the tower are
$90E6[N/m^2]$ ,$441E6[N/m^2]$ and$94E6[N/m^2]$ . Therefore, the value of the applied safety factor to each part of the survival probability of 95% are satisfied. -
According to the Fourth Assessment Report of the Inter governmental Panel on Climate Change(IPCC), climate change is already in progress around the world, and it is necessary to start mitigation and adaptation strategies for buildings in order to minimize adverse impacts. It is likely that the South Korea will experience milder winters and hotter and more extreme summers. Those changes will impact on building performance, particularly with regard to cooling and ventilation, with implications for the quality of the indoor environment, energy consumption and carbon emissions. This study generate weather data for future climate change for use in impacts studies using PRECIS (Providing REgional Climate for Impacts Studies). These scenarios and RCM (Regional Climate Model) are provided high-resolution climate-change predictions for a region generally consistent with the continental-scale climate changes predicted in the GCM (Global Climate Model).
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The Korea Institute of Energy Research(KIER) has begun collecting horizontal global insolation data since May, 1982 at 16 different locations in Korea and for the more detailed analysis, images taken by geostationary satellite may be used to estimate solar irradiance fluxes at earth I s surface. It is based on the empirical correlation between a satellite derived cloud index and the irradiance at the ground. From the results, the measured data has been collected at 16 different stations and estimated using satellite at 23 different stations over the South Korea from 1982 to 2000. The Result of analysis shows that the armual-average daily global radiation on the horizontal surface is
$3.56kWh/m^2/day$ and Estimated solar radiation fluxes show reliable results for estimating the global radiation with average deviation of -7.27 to +3.65% from the measured values. -
KnowledgThe Korea Institute of Energy Research(KIER) has begun collecting horizontal global insolation data since May, 1982 at different locations. Because of a poor reliability of existing data, KIER's new data will be extensively used by the solar system users as well as by research institutes. But the quality of solar insolation data is not always good. This reports on an attempt to identify systematic error in such data using clear-day analysis for data rehabilitation. Clear-day analysis is successful in uncovering solar insolation data of questionable quality. It is not proven that rehabilitation process can improve the quality of data for daily or monthly means, but it is suggested that the method can be used to improve the quality of data for monthly means of several years for use in many applications of solar energy plarming. Earlier studies finding a maximum ETR of about 0.80 are confirmed.
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An experimental study was conducted to investigate the thermal performance of a medium-temperature heat pipe against the charge amount of working fluid. The container and the wick of the heat pipe were made of stainless steel and the working fluid was Dowtherm-A for medium-temperature applications around
$250^{\circ}C$ . The diameter and length of the heat pipe were 25.4 mm and 1 m, respectively. The maximum thermal load was 1 kW and the working fluid charge ratio varied from 372% to 420%. The results showed that the thermal resistance ranged from 0.12 to$250^{\circ}C/W$ and the effective thermal conductance ranged from 7,703 to$8,898 W/m{\cdot}K$ . Dry-out occurred for the heat pipe with 372% fill-charge at the heat load of 950 W, while the other heat pipes with higher charge amount did not encounter dry-out up to 1060 W. -
This study was accomplished to evaluate the performance of Multi Effect Distillation(MED) for solar thermal desalination system. It was designed Multi effect distillation with
$3m^3/day$ capacity and Shell&Tube type heat exchanger. Also, The effective heat transfer of Shell&Tube heat exchanger was used Cu(90%)-Ni(10%) corrugated tube. The parameters relating to the performance of Multi Effect Distillation are known as hot water flow rate. The experimental conditions for each parameters were$18^{\circ}C$ for sea water inlet temperature,$6m^3/hour$ sea water inlet volume flow rate,$75^{\circ}C$ for hot water inlet temperature, 2.4, 3.6, and$4.8m^3/hour$ for hot water inlet volume flow rate, respectively. The results are as follows, Development for Multi effect distillation was required about 40kW heat and 35kW cooling source to produce$3m^3/day$ of fresh water. And, Performance ratio of Development Multi effect distillation was about 2.0191. -
As the instability of oil prices rose because of the situation in Libya, oil prices worldwide recorded the highest level due to the interference in supply. And so, in the 21st century, increasing efforts are being made to use clean new renewable energy centered on solar energy in accommodation of the cycle of nature instead of being reliant on the oil exporting nations. In order to reduce city energy internationally, the implementation of a low carbon city under the combined cooperation of industrial. construction, new renewable energy and transportation sectors with continuous development centered on low carbon green urban planning is now becoming established as the paradigm of the times. Recently, the government has begun carrying out the One Million Green Home Project, which is a project where the government with the goal of providing one million renewable energy homes by 2020 gives renewable energy subsidization for a partial amount of the standard unit price of installation when solar ray, solar heat, geothermal heat, small wind power or fuel cell energy is used. Thus, through this thesis which studies the state of and surveys the green village at Shingok-ri Songhak-myun Jaecheon-shi, it is the desire that the One Million Green Homes Project will be more efficiently developed and plans for improvement formed so that a high level of satisfaction in the product will be provided.
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Thermal design was conducted for a solar thermal storage system in a medium-temperature range between
$200^{\circ}C$ and$400^{\circ}C$ . The system was composed of heat pipes as heat carrier and molten salts as phase-change storage material. Each heat pipe penetrated through the storage system and had two heat-exchanging sections at both ends to interact with high-and low-temperature steams, while it exchanged heat with molten salts in the middle section. During a heat-storage mode, the heat pipes transferred heat from the hot steam at one side to the molten salts and it transferred heat from the molten salt to the cold steam at the other side during the heat-dissipating mode. A tube-bank type heat exchanger theory was applied to this design task to meet the required inlet and outlet temperatures of the steams depending on the operation modes. Several design variables were considered including the lengths of evaporator and condenser of a heat pipe, traverse and longitudinal pitches of the pipe, and the number of rows of the heat pipes for two different molten salt baths. An optimum design results were presented with discussion. -
Nowdays the most critical problem is global warming and the most important reason is the high emition of carbondioxide. 23% of the use of carbondioxide is used in building and decreasing the use of it is very important. One of the biggest factor that can decrease the use of energy is developing the heat conducting ratio of the materials we use in building. Heat conducting ratio is the important factor in the use of reducing energy comsumation. In this research, there are methods about how to measure the heat conducting ratio, and the existing the representing measuring method which is Heat Flow Meter HFM 436, Laser Flash Analysis and find out about the TCi of the new method C-Therm and compare the results.
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Many studies in crystalline silicon solar cell fabrication have been focused on high efficiency and low cost. In this paper, we carried out the doping procedure by varying the silicon wafer thicknesses and sheet resistance. The silicon wafers with various thicknesses were obtained by shiny etching and texturing. The thicknesses of wafers were 100, 120, 150, and
$180{\mu}m$ . The emitter layer formed by$POCl_3$ doping process had sheet resistance with 40 and$80{\Omega}/sq$ for selective emitter application. This experiment indicated wafer thickness did not influence sheet resistance but lifetime was strongly effected. -
The doping procedure in crystalline silicon solar cell fabrication usually contains oxygen injection during drive-in process and removal of phosphorous silicate glass(PSG). In this paper, we studied the effect of oxygen injection and PSG on conversion efficiency of solar cell. The mono crystalline silicon wafers with
$156{\times}156mm^2$ ,$200{\mu}m$ ,$0.5-3.0{\Omega}{\cdot}cm$ and p-type were used. After etching$7{\mu}m$ of the surface to form the pyramidal structure, the P(phosphorous) was injected into silicon wafer using diffusion furnace to make the emitter layer. After then, the silicon nitride was deposited by the PECVD with 80 nm thickness and 2.1 refractive index. The silver and aluminium electrodes for front and back sheet, respectively, were formed by screen-printing method, followed by firing in 400-425-450-550-$880^{\circ}C$ five-zone temperature conditions to make the ohmic contact. Solar cells with four different types were fabricated with/without oxygen injection and PSG removal. Solar cell that injected oxygen during the drive-in process and removed PSG after doping process showed the 17.9 % conversion efficiency which is best in this study. This solar cells showed$35.5mA/cm^2$ of the current density, 632 mV of the open circuit voltage and 79.5 % of the fill factor. -
Surface Texturing is an essential process for high efficiency in multi-crystalline silicon solar cell. In order to reduce the reflectivity, there are two major methods; proper surface texturing and anti-reflection coating. For texturization, wet chemical etching is a typical method for multi-crystalline silicon. The chemical solution for wet etching consists of HF,
$NHO_3$ , DI and$CH_3COOH$ . We carried out texturization by the change of etching time like 15sec, 30sec, 45sec, 60sec and measured the reflectivity of textured wafers. As making the silicon solar cells, we obtained the conversion efficiency and relationship between texturing condition and solar cell characteristics. The reflectivity from 300nm to 1200nm was the lowest with 15 sec texturing time and 60 sec texturing time showed almost same reflectivity as bare one. The 45 sec texturing time showed the highest conversion efficiency. -
In this paper, we studied the optimization of the screen pringting method for crystalline silicon solar cell fabrication. The 156 * 156 mm2 p-type silicon wafers with
$200{\mu}m$ thickness and$0.5-3{\Omega}cm$ resistivity were used after texturing, doping, and passivation. Screen printing method is a common way to make the c-Si solar cell with low-cost and high-efficiency. We studied the optimized condition for screen printing with crystalline silicon solar cell as changing the printing direction (finger line or bus bar), finger width, and mesh angle. As a result, the screen printing with finger line direction showed higher finger height and better conversion efficiency, compared with one with bus bar direction. The experiments with various finger widths and mesh angles were also carried out. The characteristics of solar cells was obtained by measuring light current-voltage, optical microscope and electroluminescence. -
The heat from PV modules should be removed for better electrical performance, and can be converted into useful thermal energy. A photovoltaic-thermal(PVT) module is a combination of PV module with a solar thermal collector which forms one device that converts solar radiation into electricity and heat simultaneously. In general, there are two different types of PVT module: glazed PVT module and unglazed PVT module. On the other hand, two types of the PVT module can be distinguished according to absorber on PV module rear side: the sheet-and-tube absorber PVT module and the fully wetted absorber PVT module. In this paper, the experimental performance of water type unglazed PVT with fully wetted absorber was analyzed. The electrical and thermal performance of the unglazed PVT were measured in outdoor conditions, and the results were analyzed. The experimental results showed that the thermal efficiency of the PVT module was 42% average, and its electrical efficiencies were 15.2% and 14.2% average, respectively, for the mean fluid temperature of
$10-20^{\circ}C$ and$21-30^{\circ}C$ . Thermal efficiency depends on solar radiation, mean fluid temperature and ambient temperature. The PVT module temperature is related to the cooling effect of the PV module by the fluid of the absorber. The results proved that the electrical efficiency was higher when the mean fluid temperature was lower. -
Worldwide, the building energy simulation becomes inevitable step for predicting the energy consumption in building. In simulation process, the expertise is required for the accurate analysis results. In Korea, however, most of user use the inconsistent data with Korea circumstance. In this step, we need to construct the standard input data matched building in Korea. In this study, electricity consumption of apartments in Daejeon is analyzed. The yearly data of a apartment complexes of 2009 are analyzed as monthly, daily(week and weekend), timely, and completion year. With this result, we are able to predict the demand pattern of electricity in a house and make the schedule by demand pattern. The results of this study are followed. The averaged amount of electricity consumption in winter is higher than summer because of the high capacity of heating equipment. All of the house has electric base load from 0.26kWh to 0.5kWh. The average of the electricity consumption of month is shown as 326.7kWh. A week is seperated as 4 part such as week, weekend, Saturday and Sunday. During week, the average of timely electricity consumption is shown as 0.442kWh. The Saturday consumption is 0.453kWh. The Sunday is 0.461kWh.
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Low-e glazing is classified as soft low-e glazing and hard low-e glazing. Hard low-e glazing can be temperable and its handling is comfortable because its coating film is a oxide film generated at high temperatures. But there is a fatal weakness that its insulation performance and shielding performance are lower compared to soft low-e glazing by low electrical conductivity of coating film. Soft low-e glazing is excellent because its coating film consists of Ag that is excellent electrical conductivity and it has strength that can supply various product consumers want. But soft low-e glazing has weaknesses that temperable and handling are difficult because Ag is oxidized easily. Therefore this study analyzes thermal performance of glazing by changing filling gas according to applying low-e glazing through simulation to judge performance before making sample. After this process, a comparative experimental study was done through TVS by making temperable low-e glazing.
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Until now, measures for energy saving in buildings have been tried. Because particularly the role of buildings area is very important for implementing national greenhouse gas reduction targets and Green growth. But, lack of business linkages between each sector or the interest and participation of private sector are not enough. In addition, relevant personnel to do had not been systematized. It is expected that certification services will be increased according to the activation of Building Energy Efficiency Rating System and expansion of the target buildings so Government must be prepared to expand of certification system by training Professional staff. In this study, the basic data for the introduction of obligation of Building Energy Efficiency Rating System is suggested through analysis of the operating and laws system of Building Energy Efficiency Rating System along with efforts of Government for diffusion low energy buildings.
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This study aims to evaluate performance of ventilation and thermal about breathing wall by flowing air to indoor on appropriate conditions that is effective aperture area in the Central region(20, 50,
$80cm^2/m^2$ ). The result is as follows : 1) Sectional temperature distribution of inflow and outflow out under the constant ventilation was reviewed. In the case of inflow, outside temperature increase effect was confirmed. 2) The more differences of temperature between outdoor and indraft of air was high, the more heat recovery was high. -
It is a wide range of types of building materials. Depending on the flow of time for the increased interest in building appearance of quality new and different materials are being developed. In particular, the case of granite widely used as cladding, recently, China's low-cost stone disguised as a large number of local granite stone as the domestic industry has been a big hit. Therefore, the purpose of study is establishment of the database for granite building exterior materials. For that, the domestic granite and chinese granite are selected. The spectrums of these material are investigated and analyzed.
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In case of newly constructed buildings, the construction type is almost Curtain-wall system or large window in building skin. However, these kind of buildings have problems with regulations on building energy efficiency. And national regulations on building energy efficiency limit only the V-factor of window(except infiltration), it is hard to predict energy consumption of Curtain-wall buildings which gain large solar energy in summer. In this study, the influence of LSG(Light to Solar Gain) on energy performance was theoretically analyzed with simulation. LSG is the value of VLT divide SHGC and represents the optical performance of the glass or glazing. The Window & Therm program developed in LBNL was used to analyze window systems and EnergyPlus was used to building energy. Cases of glazing are three types; single coated Low-e clear glazing, tripple coated Low-e clear glazing, tripple coated Low-e tinted glazing. The results of this study are follows; 1) The building energy consumption of Alt-l, 2, 3 were about 300, 253,
$259kWh/m^2{\cdot}yr$ respectively. Therefore, improvement of LSG could save the energy up to 16%. 2) The saved energy could be converted 1 billion won as annual benefit of total energy costs 3) SHGC and LSG more influence on cooling energy than heating energy in office buildings. -
Thermal storage plays an important role in building energy saving, which is greatly assisted by the incorporation of latent heat storage in building materials. A phase change material is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, can be storing and releasing large amount of energy. Heat is stored or released when the material changes from solid to liquid. Integration of building materials incorporating PCMs into the building envelope can result in increased efficiency of the built environment. The aim of this research is to identify thermal performance of PCMs impregnated building materials which is applied to interior of building such as gypsum and red clay. In order to analyze thermal performance of phase change materials, test-cell experiments and simulation analysis were carried out. The results show that micro-encapsulated PCM has an effect to maintain a constant indoor temperature using latent heat through the test-cell experiments. PCM wallboard makes it possible to reduce the fluctuation of room temperature and heating and cooling load by using EnergyPlus simulation program. Phase change material can store solar energy directly in buildings. Increasing the heat capacity of a building is capable of improving human comfort by decreasing the frequency of indoor air temperature swings so that the interior air temperature is closer to the desired temperature for a long period of time.
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Recently, from a saving energy and environmental lighting sources point of view, using LED lighting have been increased rapidly. The colors of light was applied to the control of dimmers that is composed of red, green, blue, and white(RGBW) to improve the quality of visual environment. Moreover this study has been processed to develop adjustable dynamic LED lighting system on SPD and definitize the various spectral power distribution and color temperature of light through the control of the four dimmers. It is possible to combine up to
$432^4$ kinds of light. Measurement of illuminance of range on working surface was as 7~l,831 lux. Application of visual environment for occupants can be expected according to control of lighting performance. -
This paper deals with the free cooling system of express bus using natural energy source in order to improve the room air quality and save cooling energy. In an express bus, there are may passengers in unit area, requiring the improvement of air quality and giving higher energy saving efficiency. Particularly, the express buses running fast make it easy to take in outdoor air at a flow rate controllable with a damper mechanism. This paper proposes the analysis on the air flow achieved by a damper controlled vertically and horizontally in order not to deteriorate the ride comfort of the passengers.
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The development of new energy has attracted consideration attention due to the high oil price and environmental problems. In advanced country, they have tried to carry out a long range plan for energy. We need to develop new energy for Low Carbon Green Growth in Korea. The building is 30% among ratio of energy consumption in Korea. And in the past, heating energy was high ratio for energy using at home. But recently, the demand for cooling energy keeps growing due to rising average temperature on the earth and improvement of life quality. In this situation, the energy of lake water and ocean water has studied to utilize in advanced country because of low temperature at underwater. But the study for deep water is still a lot left to do. In this study, we analyzed district cooling system and the present condition. Analyzing the deep lake water cooling system in Toronto, we found an application of district cooling system using deep ocean water. Deep lake water uses heat source for district cooling and water source for city in Toronto. So reducing the initial cost, this city had economic effect. When DLWC was applied at existing building, the heat exchanger was installed instead of cooling tower and refrigerator. And the heat exchanger used to connect main pipe with cool water on city. System using deep ocean water can be applied as a similar way to supply cool water from lake to building.
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The important use of the desuperheater(multi spray type) changes the superheated steam into the saturated steam. It is more efficient and suitable for using the process. Also, it is more convenient and stable regarding the process temperature control. In this study, transient and quasi-static analysis were done for the evaluation of structural integrity of the multi spray type desuperheater of the power plant. Computational analysis was used to calculate the thermal stress, and the vibration test was done to evaluate the structural stability. This paper is verified by analysis that water spray nozzle(
${\phi}=28mm$ ) shows the best ability. The results show that structural stability of the desuperheater under the real operating condition was proven. -
Low-grade waste heat has generally been discarded in industry due to lack of efficient recovery methods. In recent years, organic Rankine cycle(ORC) has become a field of intense research and appears as a promising technology for conversion of heat into useful work of electricity. In this work thermodynamic performance of ORC with superheating of vapor is comparatively assessed for various working fluids. Special attention is paid to the effects of system parameters such as the evaporating temperature on the characteristics of the system such as maximum possible work extraction from the given source, volumetric flow rate per 1 kW of net work and quality of the working fluid at turbine exit as well as thermal efficiency.
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Liquid desiccant material, such as lithium chloride (LiCl) or halide slits are usually used on air conditioning application for controlling the humidity of high Outdoor Air (OA). Solar energy is usually used to heat the liquid in regeneration process of those desiccant. The mass transfer it self is driven by the temperature different between the liquid desiccant and the input air. This experiment study is analyzing the characteristic of the aqueous LiCl-air temperature different in variance specific gravity, especially in range of temperature different using the solar energy as the heat generator. The experiment has done by variating the concentration of the LiCl with specific gravity 1.210 and 1.150. For the comparison the pure water is also used. The result show that the mass transfer rate is increased in every variation as the increases of the temperature different, and the weeker aqueous solution of the LiCl the highest mass transfer coefficient.
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With the improvement of standard of manufacturing process, oil cooling unit for manufacturing machine has been developed. A control system must be designed in order to keep oil temperature of the machine within a very restricted range and also to reduce energy consumption. In order to get the low deviation of the controlled temperature and the low efficiency, the on/off control scheme is gradually being replaced by a variable speed refrigeration system (VSRS) with an inverter driven compressor over recent decades. This paper gives the flowchart to control the compressor speed and also the electronic expansion valve (EEV) aperture in oil cooling unit refrigeration system using R22 as the refrigerant. This control scheme has already tested in experiment apparatus with room temperature condition constant at
$25^{\circ}C$ and variable load condition at 4kW, 6kW, 7kW, 8kW and 10kW. -
According to the environment report of UN, korea was classified as potable water shortage countries. Approximately 71% of the Earth's surface is covered by ocean. However, it is difficult to use for industry of residential purpose without a certain processing. The development of solar and waste-heat used absorption desalination technology have been examined as a viable option for supplying clean energy. In this study, the modelling of the main devices for solar and waste-heat used and adsorption desalination system was introduced. The design is divided into three parts. First, the evaporator for the vaporization of the top water is designed, and then the reactor for the adsorption and release of the steam is designed, followed by the condenser for the condensation of the fresh water is designed. In addition, new features based on the energy balance are also included to design absorption desalination system. In this basicresearch, One-bed(reactor) adsorption desalination plant that employ a low-temperature solar and waste energy was proposed and experimentally studied. The specific water yield is measured experimentally with respect to the time controlling parameters such as heat source temperatures, coolant temperatures, system switching and half-cycle operational times.
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The feasibility study must be conducted for construction of complex for generation of electric power such as items to get permission and grid connection etc. including wind resource to construct a complex for wind power generation. Since wind power can be used by converting only around 20~40% of energy coming in that kinetic energy of wind passes through blades and driving device into electric energy, when constructing a complex, the survey of wind resource takes up the most important part. Data logger used to measure this wind energy are expressed by calculating generally electromotive that is created from a sensor, variable-type, pulse-type signal to be proper for the actual value, and most data loggers have a type without considering geographical features. Besides, in the case of Met mast that is installed to survey the wind resource, since it is installed lower than the hub height of a wind power generator due to permission matters and the economic factors, the height of wind speed by utilizing Deacon equation is compensated to revise this. In this study, a device measuring wind speed was made by using algorithm that is possible to compensate the height of wind speed according to regional features and by applying Deacon equation, and the function of data storage through SD card or RS232 communication was added as well. Besides it's possible to check data more easily with a type of graph by using LCD touch screen for the convenience of users.
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This study examined the cooling performance of a solar heating and cooling system for an office building using the dynamic simulation program (TRNSYS). This solar heating and cooling system incorporates evacuated tube solar collectors of
$204m^2$ , storage tank of$8m^3$ , 116.2kW auxiliary heater, single-effect$LiBr/H_2O$ absorption chiller of 20RT nominal cooling capacity. It was found that for the representing day showed peak cooling load the annual average collection efficiency of the collector was 32.9% and coefficient of performance of single-effect$LiBr/H_2O$ absorption chiller was 0.68. And the results shows for the cooling season the solar fraction of the solar heating and cooling system was 32.2% and maximal and minimal solar fraction was 63.4% for May 17.9% for July respectively. -
The volumetric solar receiver is a key element of solar power plants using air. The solar flux distribution inside the receiver should be a priori known for its heat transfer modeling. Previous works have not considered characteristics of the solar flux although they change with radiative properties of receiver materials and receiver geometries. A numerical method, which is based on the Monte Carlo ray-tracing method, was developed in the current work. The solar flux distributions inside multi-channeled volumetric solar receivers were calculated when light is concentrated at the KIER solar furnace. It turned out that 99 percentage of the concentrated solar energy is absorbed within 15 mm charmel length for the charmel radius smaller than 1.5 mm. If the concentrated light is assumed to be diffuse, the absorbed solar energy at the charmel entrance region is overpredicted while the light penetrates more deeply into the charmel. The developed method will help understand the solar flux when only a part of concentrated light is of interest. Furthermore, if the presented results are applied for heat transfer modeling of multi-channeled volumetric solar receivers, one could examine effects of receiver charmel properties and shape on air temperature profiles.
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Feasibility assessment for small hydropower plants using diversion weirs located in stream for agricultural purpose has been studied. The model, which can predict flow duration characteristic of stream, was developed to analyze the inflow caused from rainfall. And another model to predict hydrologic performance for small hydropower plants is established. Preliminary survey was performed identifying several candidate sites, and two sites were selected finally for actual site reconnaissance. During the course of site survey, generating capacity, construction and equipment cost, and payback through life time of each sites were calculated for economical feasibility analysis. The results of this study have estimated that the small hydropower plants using diversion weirs for agricultural purpose may offer better opportunities in future with increasing fuel cost and nation's energy policy.
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Small hydropower resources for five major river systems have been studied. The model, which can predict flow duration characteristic of stream, was developed to analyze the variation of inflow caused from rainfall condition. And another model to predict hydrologic performance for small hydropower(SHP) plants is established. Monthly inflow data measured at Andong dam were analyzed. The predicted results from the developed models in this study showed that the data were in good agreement with measured results of long term inflow at Andong darn. It was found that the models developed in this study can be used to predict the available potential and technical potential of SHP sites effectively. Based on the models developed in this study, the hydrologic performance for small hydropower sites located in river systems have been analyzed. The results show that the hydrologic performance characteristics of SHP sites have some difference between the river systems. Especially, the specific design flowrate and specific output of SHP sites located on North Han river and Nakdong river systems have large difference compared with other river systems.
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Small hydropower is one of the many types of new and renewable energy, which South Korea is planning to develop, as the country is abundant in endowed resources. In order to fully utilize small hydropower resources, there is a need for greater precision in quantifying small hydropower resources and establish an environment in which energy sources can be discovered using the small hydropower resource management system. This study has given greater precision to calculating annual electricity generation and installed capacity of small hydropower plants of Han river system by inquiring into average annual rainfall, basin area and runoff coefficient, which is anticipated to promote small hydropower resources utilization. Small hydropower resource management system was also established by additionally providing base information on quantified small hydropower resources and analysis function and small hydropower generator status, rivers, basin, rainfall gauging station, water level gauging station etc.. Small hydropower resource management system can be used gather basic information for positive applications of small hydropower energy nationwide.
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SolarPACES is an international cooperative network bringing together teams of national exports from around the world to focus on the development and marketing of concentrating solar power systems (also known as solar thermal power systems). It is one of a number of collaborative programs, called Implementing Agreements, managed under the umbrella of the International Energy Agency to help find solutions to worldwide energy problems. Technology development is at the core of the work of SolarPACES. Member countries work together on activities aimed at solving the wide range of technical problems associated with commercialization of concentrating solar technology, including large-scale system tests and the development of advanced technologies, components, instrumentation, and systems analysis techniques. In addition to technology development, market development and building of awareness of the potential of concentrating solar technologies are key elements of the SolarPACES program The Implementing Agreement specifies broad "Tasks," or thematic areas of work SolarPACES currently has three ongoing tasks, focusing on concentrating solar electric power systems (Task I), solar chemistry research (Task II), and solar technology and applications (Task III). An Operating Agent, nominated by the ExCo, is responsible for overseeing the work of each task Each task maintains a detailed program of work that defines all task activities, including their objectives, participants, plans, and budgets. In addition to technical reports of the activities and their participants, accomplishments and progress are summarized in the SolarPACES annual report. Many SolarPACES activities involve close cooperation among member countries (either through sharing of task activities or, occasionally, cost-sharing), although some cooperation is limited to sharing of information and results with other participants. In this paper, structure, works, and members of SolarPACES and Korean activies in the SolarPACES are introduced.
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A Photovoltaic/Thermal(PVT) solar system consists of PV module and thermal absorber plate which convert the absorbed solar radiation into electricity and heat. Meaningful researches and development (R&D) on the PVT technologies have been performed since the 1970s. This paper presents a review of the previous works covering the various types of PVT and their performance analysis in terms of electrical and thermal efficiency. This review compares electrical and thermal efficiency of the different types of PVT collectors and analyzes the parameters affecting PVT performance. Based on the literature review, box charmel type PVT with unglazed, or flat plate PVT with glazed have the highest efficiency among them. From the literature review, R&D should be carried out aiming at improving their overall electrical and thermal efficiency and cutting down the cost, making them more competitive in the energy consumption market.
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Environmental pollution by Using of a fossil fuel, a reckless and growth-oriented development since the Industrial Revolution has caused global change of environment. An issue largest among this is a climate change. A global mean temperature since 19th century has climbed up
$0.4{\sim}0.8^{\circ}C$ . After The Kyoto Protocol regarding a greenhouse gas reduction goal took effect, be situations that decrease of greenhouse gas was acutely required. Interest of utilization of the new & renewable energy is increasing every day. This study shows that at first divided a country to nine range by natural geography, and second executed Meteorological data analysis of recent 30 years considering level of significance by nine range. The results of this study are that in heating load calculation of building, periodic temperature data management is required because facility capacity and cost are affected greatly by outdoor temperature, and temperature by climate range needs consideration of pertinent area. Lastly, ground temperature was assumed of the weather in region, the ground and soil. -
Presently, various building certification systems are being enforced in Korea. However, people are in confusion and have an aptitude to waste time and money because these certification systems for buildings have very similar criteria. After investigating the foreign certification systems and domestic certification systems for the building, it is required that some of similar building certification systems are integrated.
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A solar cell is primary parts to produce electrical energy from the Sun. And, we can utilize those solar cells as a power generation system in home, factory, and so on. In order to make proper power, the solar cells are configured in series and parallel lay down. In condition of uniform illumination, the solar array will produce an enough power by photovoltaic effects from the solar cells. In case of non-uniform illumination on the solar cells, the power will be dramatically decreased compared to design. Fortunately, there were so many research outputs regarding the illumination effects on solar array. In this work, we tried to find out the non-uniform effects on unit CPV solar cell, because there were no research outputs for unit CPV solar cell considering illumination. The CPV solar cell was used in CPV system to make a power by the Sun. We chosen the triple junction solar cell of GaAsInP2Ge for simulation, which has a 30 % of conversion efficiency. By simulation, we obtained the output performance of CPV solar cells in condition of various illumination by using Hamming Window function. Its performance was degraded by 10 % to 50 % depending illumination conditions.
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Solar reforming of methane with
$CO_2$ was successfully tested with a direct irradiated absorber on a parabolic dish capable of$5kW_{th}$ solar power. The new type of catalytically activated metallic foam absorber was prepared, and its activity was tested. Ni was applied as the active metal on the gamma - alumina coated Ni metal foam for the preparation of the catalytically-activated metal foam layer. Compared to conventional direct irradiation of the catalytically-activated ceramic foam absorber, this new metallic foam absorber is found to exhibit a superior reaction performance at the relatively low insolation or at low temperatures. In addition, unlike direct irradiation of the catalytically-activated ceramic foam absorber, metallic foam absorber has better thermal resistance, which prevents the emergence of cracks caused by mechanical or thermal shock. The total solar power absorbed reached up to 2.1kW and the maximum$CH_4$ conversion was almost 40%. -
Ryu, Kwnag-Sun;Shin, Goo-Hwan;Cha, Won-Ho;Myung, Noh-Hoon;Kim, Young-Sik;Chung, Ho-Yoon;Kim, Dong-Kyun;Kang, Gi-Hwan 282
The artificial increase in the solar intensity incident on solar cells using lenses or mirrors can allow solar cells to generate equivalent power with a lower cost. In application areas of Fresnel lenses as solar concentrators, several variations of design were devised and tested. Some PV systems still use commercially available flat Fresnel lenses as concentrators. In this study, we designed and optimized flat Fresnel lens and the 'light pipe' to develop 500X concentrated solar PV system. We performed rigorous ray tracing simulation of the flat Fresnel lens and light-pipe. The light-pipe can play imporatant roles of redistributing solar energy at the solar cell and increase the mechanical tolerance so that it can increase the lifetime of the high-concentration solar PV system and decrease the cost of manufacturing. To investigate the sensitivity of the solar power generated by the concentrated solar PV according to the performance of lens and light pipe, we performed raytracing and executed a simulation of electrical performance of the solar cell when it is exposed to the non-uniform illumination. We could conclude that we can generate 95 % or more energy compared with the energy that can be generated by perfectly uniform illumination once the total energy is given the same. -
It has found that the using library base on criteria of a foreign country resulted in problem of reliability. In order to obtain reliable result, it was necessary to develop the simulation input library based on domestic condition. So, this study was conducted for making the library in accordance with domestic condition when doing simulation modeling about the exist and new buildings. The range of library were consist of material, facility systems, schedules and weather data. And Energy Plus program was used when making library. We hope that the developed library will contribute to reliability when simulating exist and new buildings.
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The most widely used method to form an electrode in industrial solar cells are screen printing. Screen printing is characterized by a relatively simple and well-known production sequence with high throughput rates. However the method is difficult to implement a fine line width of high-efficiency solar cells can not be made. The open circuit voltage(Voc) and the short circuit current density(Jsc) and fill factor(FF) need to be further improved to increase the efficiency of silicon solar cells. In this study, gravure offset printing method using the multicrystalline-silicon solar cells were fabricated. Gravure off-set printing method which can print the fine line width of finger electrode can have the ability reduce the shaded area and increase the Jsc. Moreover it can make a high aspect ratio thereby series resistance is reduced and FF is increased. Approximately
$50{\mu}m$ line width with$35{\mu}m$ height was achieved. The efficiency of gravure off set was 0.7% higher compare to that of scree printing method. -
This paper proposes a novel sensorless maximum power point tracking (11PPT) algorithm for PV systems. The method is based on dividing the operating time into several intervals in which the PV terminals are short circuited in one interval and the calculated short-current of the PV is obtained and used to determine the optimum operating point where the maximum output power can be obtained. The proposed MPPT algorithm has been introduced into a current-controlled boost converter whose duty ratio is controlled to the maintain MPP condition. The same sequence is then repeated regularly capturing the PV maximum power. The main advantage of this method is eliminating the current sensor. Meanwhile, this MPPT algorithm reduces the power oscillations around the peak power point which occurs with perturbation and observation algorithms. In addition, the total cost will decrease by removing the current sensor from the PV side. Finally, simulation results confirm the accuracy of the proposed method.