• Journal of the Korean Solar Energy Society
• /
• v.33 no.1
• /
• pp.79-88
• /
• 2013

This study set out to evaluate the economy, environmentality, and complexity (economy+environmentality) of fire station buildings of public service facilities and propose ways to apply the optimization of renewable energy system to fire station buildings. As for economy according to life cycle costs, economy increased when the application percentage of the geothermal and solar heat system increased over the three renewable energy system types (geothermal, solar heat, and solar photovoltaic). On the other hand, economy decreased when the application percentage of the solar photovoltaic system increased. As for environmentality according to tons of carbon dioxide, environmentality decreased when the application percentage of the geothermal and solar heat system increased. Environmentality increased when the application percentage of the solar photovoltaic system increased. As for complexity (economy+environmentality) according to the weighted coefficient method, complexity increased when the application percentage of the geothermal system increased. It was highest at the combination of the solar heat system (20%) and geothermal system (80%). On the other hand, complexity decreased when the application percentage of the solar photovoltaic system increased. It was lowest at the combination of the solar photovoltaic system (80%) and geothermal system (20%).

• Journal of Biosystems Engineering
• /
• v.27 no.4
• /
• pp.327-334
• /
• 2002

In this study, energy conversion from thermal energy to mechanical power by using n-pentane was tested and exergy variation, cycle number, water quantity pumped and thermal efficiency were analyzed. The energy conversion was done and the water head could be ten meters on the experimental conditions. The operating temperature range of cycle was recommended to be around the liquid-vapour saturation temperature of the working fluid on the viewpoint of the maximum work. The cycle diagram was analyzed by the exergy analysis. For the constant water head, the cycle number was decreased and the water quantity per day was increased and thermal efficiency become higher when the water quantity per cycle become increasing. For the constant pumping water quantity per cycle, cycle number and the water quantity per day was decreased and the thermal efficiency become higher because the saturation temperature become higher when the water head become higher.

• Journal of the Korean Solar Energy Society
• /
• v.31 no.1
• /
• pp.23-30
• /
• 2011

International cooperation to reduce greenhouse gas emissions is expected to provide a big crisis and a great opportunity at the same time for our industry that heavily consumes energy. To cope actively with the international environmental regulation, such as the Framework Convention on Climate Change, quantitative measurement of the volume of greenhouse gases emitted by various industries and quantitative prediction of the greenhouse gas emissions of the future are becoming more important than anything else at the national level. This study aims to propose the calculation process of carbon dioxide($CO_2$) emission for building in life cycle. This paper describes and compares 9 different tool for environmental load estimation with LCA. This study proposed the calculation process for quantitatively predicting and assessing $CO_2$ emissions during the life cycle of buildings based on the life cycle assessment(LCA). The life cycle steps of buildings were divided into the design/supervision, new construction, repair, renovation, use of operating energy in buildings, maintenance, and reconstruction stage in the life cycle inventory analysis and the method of assessing the environmental load in each stage was proposed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.22 no.12
• /
• pp.859-866
• /
• 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 Astronomy and Space Sciences
• /
• v.30 no.4
• /
• pp.241-246
• /
• 2013

We have investigated drought periodicities occurred in Seoul to find out any indication of relationship between drought in Korea and solar activities. It is motivated, in view of solar-terrestrial connection, to search for an example of extreme weather condition controlled by solar activity. The periodicity of drought in Seoul has been re-examined using the wavelet transform technique as the consensus is not achieved yet. The reason we have chosen Seoul is because daily precipitation was recorded for longer than 200 years, which meets our requirement that analyses of drought frequency demand long-term historical data to ensure reliable estimates. We have examined three types of time series of the Effective Drought Index (EDI). We have directly analyzed EDI time series in the first place. And we have constructed and analyzed time series of histogram in which the number of days whose EDI is less than -1.5 for a given month of the year is given as a function of time, and one in which the number of occasions where EDI values of three consecutive days are all less than -1.5 is given as a function of time. All the time series data sets we analyzed are periodic. Apart from the annual cycle due to seasonal variations, periodicities shorter than the 11 year sunspot cycle, ~ 3, ~ 4, ~ 6 years, have been confirmed. Periodicities to which theses short periodicities (shorter than Hale period) may be corresponding are not yet known. Longer periodicities possibly related to Gleissberg cycles, ~ 55, ~ 120 years, can be also seen. However, periodicity comparable to the 11 year solar cycle seems absent in both EDI and the constructed data sets.

• Solar Energy
• /
• v.10 no.1
• /
• pp.63-79
• /
• 1990

It has been recognized that a policy for supplying solar house and hot water production systems utilizing solar energy needs to be driven to save civilian comsuming energy or to develop alternative energy. However, the economic feasibility study of solar energy systems must be carried out before their practical use. The purpose of this study is to furnish information for supplying policy and enlightening users with the economic feasibility study of solar house and hot water production systems. Decision support systems are established to carry out economic analysis on solar systems more accurately. Therefore, computer simulation is carried out to analyze the performance of solar systems and also economic feasibility study by trial and error method is carried out. Fuel cost and additional cost for solar systems are estimated employing present worth concept and economic analysis has been conducted using the break-even point analysis method and life-cycle cost analysis method.

• Korean Journal of Materials Research
• /
• v.23 no.6
• /
• pp.304-308
• /
• 2013

The effect of a sputter deposition sequence of Cu, Zn, and Sn metal layers on the properties of $Cu_2ZnSnS_4$ (CZTS) was systematically studied for solar cell applications. The set of Cu/Sn/Zn/Cu multi metal films was deposited on a Mo/$SiO_2$/Si wafer using dc sputtering. CZTS films were prepared through a sulfurization process of the Cu/Sn/Zn/Cu metal layers at $500^{\circ}C$ in a $H_2S$ gas environment. $H_2S$ (0.1%) gas of 200 standard cubic centimeters per minute was supplied in the cold-wall sulfurization reactor. The metal film prepared by one-cycle deposition of Cu(360 nm)/Sn(400 nm)/Zn(400 nm)/Cu(440 nm) had a relatively rough surface due to a well-developed columnar structure growth. A dense and smooth metal surface was achieved for two- or three-cycle deposition of Cu/Sn/Zn/Cu, in which each metal layer thickness was decreased to 200 nm. Moreover, the three-cycle deposition sample showed the best CZTS kesterite structures after 5 hr sulfurization treatment. The two- and three-cycle Cu/Sn/Zn/Cu samples showed high-efficient photoluminescence (PL) spectra after a 3 hr sulfurization treatment, wheres the one-cycle sample yielded poor PL efficiency. The PL spectra of the three-cycle sample showed a broad peak in the range of 700-1000 nm, peaked at 870 nm (1.425 eV). This result is in good agreement with the reported bandgap energy of CZTS.

• Journal of the Korean Solar Energy Society
• /
• v.22 no.4
• /
• pp.97-106
• /
• 2002

The purpose of this study is to analyze the life cycle cost of primary cooling system by systematic support cost. Life Cycle Cost(LCC) is the process of making an economic assessment of an item, area, system, or facility by considering all significant costs of ownership over an economic life, expressed in terms of equivalent costs. The essence of life cycle costing is the analysis of equivalent costs of various alternative proposals. In order to select economical primary cooling system in early heat source plan stages, the research investigates cost items and cost characteristics during project process phases such as planning/design, construction, maintenance /management, and demolition/sell phases. The study also analyze the life cycle cost by capacity leading to suggest the most economical primary cooling system by systematic support cost.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.544-549
• /
• 2009

The purpose of this study is to investigate the field Operation Characteristics of a sea water heat source cascade heat pump system and system applicable to Building. Cascade heat pump system is composed R410A compressor, R134a compressor, EEV, cascade heat exchanger, Plate heat exchanger etc. Building area is $890m^2$ and has five floors above ground. R410A is used for a low-stage working fluid while R134a is for a high-stage. The system could runs at dual mode. One is mode of general R410A refrigeration cycle in summer and the other is cascade cycle. In order to gain a high temperature supply water in winter season, the system is designed to perform a cascade cycle. The filed test results show that the sea water heat source heat pump system exhibits a COP of about 5.5 in cooling mode along with a heating COP of about 4.0 in 1-stage heating mode. Cascade 2-stage heat pump system is enough to supply $60^{\circ}C$ water and heating COP is about 3.0

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.6
• /
• pp.403-410
• /
• 2020

This paper focuses on the design of a 12-kW small-scale supercritical CO₂ test loop. A theoretical study, stabilization, and optimization of carbon dioxide were carried out with the application of a solar heat source based on solar thermal data in Pohang. The thermodynamic cycle of the test facility is a Rankine cycle (transcritical cycle), which contains liquid, gas, and supercritical CO₂. The system is designed to achieve 6.98% efficiency at a maximum pressure of 12 MPa and a maximum temperature of 70℃. In addition, the optimum turbine inlet temperature and pressure were calculated to increase the cycle efficiency, and the application of an internal heat exchanger (IHX) was simulated. It was found that the maximum efficiency increases to 18.75%. The simulation confirmed that the efficiency of the cycle is 6.7% in May and 6.26% in June.