• The KSFM Journal of Fluid Machinery
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• v.19 no.6
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• pp.34-42
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• 2016

The organic Rankine cycle (ORC) has been used to convert thermal energy to mechanical energy or electricity. The available thermal energy could be waste heat, solar energy, geothermal energy, and so on. However, these kinds of thermal energies cannot be provided continuously. Hence, the ORC can be operated at the off-design point. In this case, the performance of the ORC could be worse because the components of the ORC system designed based on a design point can be mismatched with the output power obtained at the off-design point. In order to improve the performance at the off-design point, a few components were replaced including generator, bearing, load bank, shaft, pump and so on. Experiments were performed on the same facility without including other losses in the experiment. The experimental results were compared with the results obtained with the previous model, and they showed that the system efficiency of the ORC was greatly affected by the losses occurred on the components.

• International Journal of Fluid Machinery and Systems
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• v.10 no.2
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• pp.164-175
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• 2017

Francis turbines are often operated over a wide load range due to high flexibility in electricity demand and penetration of other renewable energies. This has raised significant concerns about the existing designing criteria. Hydraulic turbines are not designed to withstand large dynamic pressure loadings on the stationary and rotating parts during such conditions. Previous investigations on transient operating conditions of turbine were mainly focused on the pressure fluctuations due to the rotor-stator interaction. This study characterizes the synchronous and asynchronous pressure and velocity fluctuations due to rotor-stator interaction and rotating vortex rope during load variation, i.e. best efficiency point to part load and vice versa. The measurements were performed on the Francis-99 test case. The repeatability of the measurements was estimated by providing similar movement to guide vanes twenty times for both load rejection and load acceptance operations. Synchronized two dimensional particle image velocimetry and pressure measurements were performed to investigate the dominant frequencies of fluctuations, vortex rope formation, and modes (rotating and plunging) of the rotating vortex rope. The time of appearance and disappearance of rotating and plunging modes of vortex rope was investigated simultaneously in the pressure and velocity data. The asynchronous mode was observed to dominate over the synchronous mode in both velocity and pressure measurements.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.491-494
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• 2008

The hydrogen fuel and fuel cell which have high energy efficiency and low pollutant emission are getting interest as an alternative energies due to the fossil fuel exhaust, green house effect and atmospheric pollutant problems. The hydrogen gas is very effective as an alternative energy. But, if it is leaked into the air it forms the mixed gas with the air then the danger of the explosion is risen up. So, the secure the safety is mostly important. In this research, to detect the leakage of the hydrogen rapidly, added the odorant materials which don't include the sulfur component into the hydrogen gas and researched on the effect of each odorant on the performance of the fuel cell. As the results, setting the cumulation electric power on the basis and comparing the pure hydrogen, 2,3-Butanedione 5ppm mixed gas 86.1%, 5-Ethylidene-2-Norbornene 17ppm mixed gas 88.2%, Isovaleraldehyde 10ppm mixed gas 74.8%, Ethyl Isobutyrate 2.2ppm mixed gas 93.5% of performance was shown.

• Advances in Energy Research
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• v.4 no.2
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• pp.147-161
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• 2016

To start with, finding a sustainable method to produce sweet water and electricity by using renewable energies is one of the most important issues at this time. So, experimental and theoretical analysis of the performance of a closed solar powered still, which is jointed to photovoltaic cells and vacuum pump and equipped by nano plate, as the principle stage of zero discharge desalination process is investigated in this project. Major goal of this work is to reuse the concentrated brine of the Mobin petrochemical complex in order to produce potable, sweet water from effluent saline wastewater and generating electricity in the same time by using solar energy instead of discharging them to the environment. It is observed the increase in brackish water temperature increases the average daily production of solar desalination still considerably. Therefore, the nano plate and vacuum pump are added to augment the evaporation rate. The insolation rate, evaporation rate, the average brackish temperature, ambient temperature, density are investigated during a year 2013. In addition to obtain the capacity of solar powered still, the highest and lowest amount of water and electricity generation are reported during a twelvemonth (2013). Results indicate the average daily production is increased 16%, which represents 7.78 kW.h energy saving comparing with traditional solar still.

• KIEAE Journal
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• v.15 no.3
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• pp.15-20
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• 2015

Purpose: Suggesting a working prototype of a kinetic light shelf unit and revealing its energy efficiency by a series of building performance simulations were presented. Recently, kinetic building envelope has been an emerging technology as an innovative way to control exterior building environment, but products from many researches about the facade could not been reached to the industrialization so far. That is because its initial installation, operation and maintenance costs are still too high to use for the practical field, although buildings using kinetic envelopes could decrease their energy consumption significantly. This narrow point of view needs to be reconsidered, since buildings require great amount of energies to run their functions through the whole life and using better building components can lead to achieve much more benefits in aspects of the lifecycle cost (LCC). Method: A series of certified simulation tools like Ecotect and Green Building Studio that are normally used for researches and developments in the field of architecture were utilized. Result: Based on simulation analyses, the result of the study has showed that the proposed system definitely has adaptability to the professions and positively shows practicability as advanced integrative building envelopes with renewable energy association.

• Korean Journal of Materials Research
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• v.29 no.12
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• pp.747-752
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• 2019

Environmental pollution remains a considerable health risk source all over the world; however, hazards are usually higher in developing countries. Iraq has long been suffering from the problem of pollution and how to treat pollution. Photocatalytic degradation has turned out to be most productive process for dye degradation. In this investigation, Rhodamine B (RhB), dye has been selected for degradation under visible light illumination. To address this issue, we fabricate erbium trioxide nanoparticles (Er₂O₃/NPs). Erbium trioxide nanoparticles are prepared and utilized for photo-catalytic degradation. The characterization of Er₂O₃/NPs is described and confirmed by utilizing of XRD (X-ray diffraction) and SEM (Scanning Electron Microscopy). The average size of Er₂O₃ nanoparticles is observed to be 16.00 nm. Er₂O₃/NPs is investigated for its ability of photo-catalytic degradation through certain selected parameters such as concentration and time. The methodological results show that the synthesized Er₂O₃/NPs is a good photo-catalytic for Rhodamine degradation.

• Wind and Structures
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• v.22 no.1
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• pp.107-131
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• 2016

The need for a more affordable, reliable, clean and secure energy has led to explorations in non-traditional sources, particularly renewable energies. Wind is one of the cleanest energy sources that plays a significant role in augmenting sustainability. Wind turbines, as energy convertors, are usually tall and slender structures, and depending on their location (inland or offshore), they can be subject to high wind and/or strong wave loadings. These loads can cause severe vibrations with detrimental effects on energy production, structural lifecycle and initial cost. A dissipativity analysis study was carried out to know whether wind turbine towers require damping enhancement or rigidity modifications for vibration suppression. The results suggest that wind turbines are lightly damped structures and damping enhancement is a potential solution for vibration lessening. Accordingly, the paper investigates different damping enhancement techniques for vibration mitigation. The efficacy of tuned mass damper (TMD), tuned liquid column damper (TLCD), tuned sloshing damper (TSD), and viscous damper (VD) to reduce vibrations is investigated. A comparison among these devices, in terms of robustness and effectiveness, is conducted. The VD can reduce both displacement and acceleration responses of the tower, better than other types of dampers, for the same control effort, followed by TMD, TSD, and finally TLCD. Nevertheless, the use of VDs raises concerns about where they should be located in the structure, and their application may require additional design considerations.

• Journal of the Korean Solar Energy Society
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• v.24 no.4
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• pp.1-10
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• 2004

In view of global environmental problems and resource exhaustion, we must develop new energy resources that are abundant and provide substitutes for fossil fuels. Renewable energies, such as solar, are ideal because they are clean, inexhaustible, and available everywhere in the world. Photovoltaic(PV) system, in general, are operated as a stand-alone, grid-tied, or hybrid system. Many of the stand-alone PV systems are installed. Although the pre-installation cost of PV system is high, it poorly has been operated due to the absence of optimal management standards. Therefore a study on the performance of PV system is important for the system design and maintenance. In this paper a photovoltaic lighting system was resigned according to load consumption. Then a PV lighting system which used electrodeless lamp as a load was installed. In order to investigate the system operating characteristics we've added a monitoring system to the PV lighting system. The monitoring system using the LabVIEW program regularly checks the operation of the PV lighting system and records the system data. According to the system data, the stability and availability of the PV lighting system were evaluated.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.2
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• pp.147-155
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• 2012

Wind power, which is one of the promising renewable energies, has shown the high growth rate of 35 % of the annual average in the recent 5 years and also windmill related equipment market has been fast-growing. Yaw & Pitch bearing are the key parts of windmill and are machined by huge vertical lathe which is monopolized by the advanced countries. The purpose of this study is to develop the multi-tasking vertical lathe for 5 MW grade windmill bearings, which might be mass produced 3 or 5 years later. In this study, the structure of the crossrail and rotary table, which are the key units of the huge multi-tasking vertical lathe, were optimized through the finite element analysis. Also the basic performance of the rotary table has been evaluated.

• Journal of Environmental Science International
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• v.9 no.1
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• pp.49-55
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• 2000

An EMERGY analysis of the main energy flows driving the economy of humans and life support systems consists of environmental energies, fuels, and imports, all expresses as solar emjoules. Total EMERGY use(720.0 E20 sej/yr) of the Nakdong River Basin is 96 per cent from imported sources, fuels and goods and services. EMERGY flows from the environment such as rain and geological uplift flux accounted for only 4 percent of total EMERGY use. Consequently, the ratio of outside investment to attracting natural resources was large, like other industrialized areas. EMERGY use per person in the Nakdong River Basin indicates a moderate EMERGY standard of living, even though the indigenous resources are very poor. Population of 6.66 million people in 1996 is already in excess of carrying capacity of the basin. Carrying capacity for steady state based on its renewable sources in only 0.226 million people. EMERGY yield ratio and environment loading ratio were 1.07 and 28.52, respectively. EMERGY sustainability index, a ratio of EMERGY yield ratio to environment loading ratio, is therefore less than one, which is indicative of highly developed consumer oriented economies. This study suggests that the economic structure of the Nakdong River Basin should be transformed from the present industrial structure to the social-economic structure based on an ecological-recycling concept for the sustainable use of the Nakdong River.