• Journal of the Korean Solar Energy Society
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• v.30 no.3
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• pp.124-130
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• 2010

Ocean Thermal Energy Conversion(OTEC) power plants have been examined as a viable option for supplying clean energy. This paper evaluated the thermodynamic performance of the OTEC Power system for the production of electric power and desalinated water. The results show that newly developed fluids such as R32, R125, R143a, and R410A that do not cause stratospheric ozone layer depletion perform as well as R22 and ammonia. Overall cycle efficiency of open cycle is the lowest value of 3.01% because about 10% of the gross power is used for pumping out non-condensable gas. Also, the hybrid cycle is an attempt to combine the best features and avoid the worst features of the open and closed cycles. The overall cycle efficiency of hybrid cycle is 3.44% and the amount of desalinated water is 0.0619 kg/s.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.597-603
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• 2016

In this paper a comparative thermodynamics analysis is carried out for organic Rankine cycle (ORC) and ammonia-water Rankine cycle (AWRC) utilizing low-grade heat sources. Effects of the working fluid, ammonia concentration, and turbine inlet pressure are systematically investigated on the system performance such as mass flow rate, pressure ratio, turbine-exit volume flow, and net power production as well as the thermal efficiency. Results show that ORC with a proper working fluid shows higher thermal efficiency than AWRC, however, AWRC shows lower mass flow rate of working fluid and lower pressure ratio of expander than ORC.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1119-1124
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• 2006

The objectives of this paper are to investigate the performance of silica gel-water adsorption refrigeration system with heat recovery process from the system experiment. This system can be driven by waste heat at near ambient temperature from $60^{\circ}C$ to $90^{\circ}C$. The cooling capacity and coefficient of performance(COP) were measured from various experimental conditions. An experimental results revealed the influence of operating temperatures(hot, cooling and chilled water), water flow rates, and adsorption-desorption cycle times on cooling capacity and COP. Under the standard conditions of $80^{\circ}C$ hot water, $25^{\circ}C$ cooling water, $14^{\circ}C$ chilled water inlet temperatures and 420sec cycle time, a cooling capacity of 1.14kW and a COP for cooling of 0.55 can be achieved.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1151-1157
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• 2012

Ocean Thermal Energy Conversion(OTEC) technology is one of the new and renewable energy that utilizes the natural temperature gradient that exists in the tropical ocean between warm surface water and the deep cold water, to generate electricity. The selection of working fluid and the OTEC cycle greatly influence the effect on the system operation, and it's energy efficiency and impacts on the environment. Working fluids of the OTEC are ammonia, R22, R407C, and R410A. In this paper, we compared boiling pressure to optimize OTEC system at $25^{\circ}C$. Also, this paper showed net-power and efficiency according to working fluids for closed cycle and regeneration cycle.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.22 no.12
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• pp.859-866
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• 2010

This study examined the economics of a solar water heating system for an office building using life cycle cost (LCC) optimization simulations. The numerical simulations were conducted with TRNSYS and GenOpt employing the Hooke-Jeeves algorithm. The solar collector area, slope, mass flow rate per collector area and storage tank volume were selected as the main design parameters of the solar water heating system. The LCC optimization simulations of the system were carried out for cases where water temperature was $60^{\circ}C$ and $50^{\circ}C$. The results showed that for water temperature at $60^{\circ}C$ and $50^{\circ}C$ the collector area could be decreased by 17% and 28%, storage tank volume could be decreased by 49% and 54%, and mass flow rate per collector area increased by 5% and 9% respectively compared to a non-optimized system. The LCC of the system was reduced by 4% for $60^{\circ}C$ and 7% for $50^{\circ}C$. The initial installation cost of the system was reduced by 24% for $60^{\circ}C$ and 34% for $50^{\circ}C$. However, the operating cost of the system increased by 16% for $60^{\circ}C$ and 36% for $50^{\circ}C$ compared to a traditional solar water heating system.

• Journal of Korean Society of Water and Wastewater
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• v.11 no.2
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• pp.50-64
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• 1997

Life cycle assessment (LCA) on total sewage sludge treatment system from thickening to incineration and melting was performed for estimating global environmental impact as $CO_2$. In general, the life cycles of actual treatment facilities consist of construction, operation and dismantlement. In this study, the amount of $CO_2$ produced from both whole and each life cycle step of currently used unit sludge treatment processes were calculated by inventory analysis. In addition, in the all processes investigated in this study, individual $CO_2$ production unit (CPU), i.e. total produced $CO_2$ by treating a unit weight of sludge was also calculated. By using the CPU matrix of the unit processes, it was possible to simulate the $CO_2$ production for any type of complex-system as well as to trace a dominant cause of $CO_2$ production in each process. Four selected alternatives examined here, each involve the same disposal way but differ substantially in the $CO_2$ exhaust.

• Journal of the Korean Solar Energy Society
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• v.26 no.2
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• pp.9-18
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• 2006

In this paper, the thermodynamic performance of OTEC cycle was examined. Computer simulation programs were developed for simple Rankine cycle, regenerative Rankine cycle, Kalina cycle, open cycle and hybrid cycle. For the simple Rankine cycle, the results show that newly developed fluids such as R410A and R32 that do not cause stratospheric ozone layer depletion perform as well as R22 and ammonia. Also, simple Rankine cycle OTEC power plant can practically generate electricity when the difference in warm and cold sea water inlet temperatures are greater than $14^{\circ}C$. The regenerative Rankine cycle showed a 1.5 to 2% increase in energy efficiency compared to the simple Rankine cycle while the Kalina cycle employing ammonia/water mixture showed a 2-to-3% increase in energy efficiency, and the overall cycle efficiencies of hybrid cycle and open cycle were 3.35% and 4.86%, respectively.

• Journal of Korean Society on Water Environment
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• v.22 no.2
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• pp.349-357
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• 2006

Nowadays, the discharges of urban streams during dry season are depleted because the hydrologic cycle in the watershed has been destroyed due to the expansion of the impermeable area, the excessive groundwater pumping, climate change, and so forth. The streamflow depletion may bring out severe water quality problems. This research are to investigate the hydrologic characteristics and to develop a technology to restore sound hydrologic cycle of Anyangcheon watershed. For the hydrological cycle analysis of the Anyangcheon watershed, continuous simulations of urban runoff were performed for the upstream basin of Gocheok bridge whose basin area covered 4/5 of the whole catchment area. The increase of impervious area by urbanization was analysed and its effect on urban runoff was evaluated. The SWMM 5 (Storm Water Management Model 5) was used for the continuous simulation of urban runoff. The analysis results of urbanization effect on runoff are as follows: the surface runoff in 2000 increases to 65% of the whole precipitation whereas the surface runoff in 1975 amounts to 50% of the precipitation; the groundwater runoff in 2000 amounts to 7% and shows 6% decrease during the period from 1975 to 2000.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.5
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• pp.67-75
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• 2014

In this study, the large-scale hydraulic model test was performed to investigate the hydraulic characteristics for development of the non-power soil cleaning and keeping system at the dike gate. The outlet height, outflow number, outflow discharge, and outflow cycle were compared and analyzed. The non-power soil cleaning and keeping system was most effective at 11.2 mm in the outlet height. And then the mean outflow cycle was 1.09 sec, and the mean outflow discharge was $0.00164m^3/s$. The total outflow number increased gradually as the water level of a water tank increased, and the outlet height decreased. As a level of water tank decreased, the mean outflow cycle was lengthened, and the unit outflow discharge increased. This result showed this system was most effective. To remove the silty clay deposited in facilities, the methods of excavation, dredging, high pressure washing, etc have been applied to the tidal facilities such as land reclamation, a small size fishing port, and a harbor for maintenance. However, this is extremely cost-ineffective, whereas the non-power soil cleaning and keeping system will bring about an enormously positive economic effect. In addition, when the non-power soil cleaning and keeping system is applied to the dike gate of land reclamation, a thorough examination of the local tidal data and the careful system planning are required to prevent the disaster damage caused by flooding.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.6
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• pp.782-791
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• 1998

This paper presents a computer simulation of five types of triple effect absorption cycles employ-ing the refrigerant absorbent combinations of NH3/LiNO3 low-pressure type NH3/LiNO3+H2O/LiBr binary two-stage type series flow cycle and two types of parallel flow cycle for H2O/LiBr. The absorption systems is investigated through cycle simulation to obtain the system characteristics with the cooling water inlet temperature approach temperature of absorber loss temperature of absorber and chilled water outlet temperature. The most important characteristic temperature of absorber and chilled water outlet temperature. The most important characteristic of NH3/LiNO3 low-pressure type and a NH3/LINO3+H2O/LiBr binary two-stage type is that it obtains a coefficient of performance higher than the sum of the performance coefficients of its part operating independently. As a result of this analysis the optimum designs and operating conditions were determined based on the operating conditions and the coefficient of performance.