• Transactions of the Korean hydrogen and new energy society
• /
• v.21 no.6
• /
• pp.595-603
• /
• 2010

This paper deals with an economic evaluation of domestic window type photoelectrochemical hydrogen production utilizing solar cells. We make some sensitivity analysis of hydrogen production prices by changing the values of input factors such as the initial capital cost, the solar to hydrogen conversion efficiency, and the system duration time. The hydrogen production price of the window type photoelectrochemical system was estimated as 1,168,972 won/$kgH_2$. It is expected that hydrogen production cost can be reduced to 47,601 won/$kgH_2$ if the solar to hydrogen conversion efficiency is increased to 14%, the system duration time is increased to 20,000 hours, and the initial capital cost is decreased to 25% of the current level. We also evaluate the hydrogen production cost of the water electrolysis using the electricity produced by solar cells. The corresponding hydrogen production cost was estimated as 37,838 won/$kgH_2$. The photoelectrochemical hydrogen production is evaluated as uneconomical at this time, and we need to enhance the solar to hydrogen conversion efficiency and the system duration time as well as to reduce prices of the system facilities.

• Transactions of the Korean hydrogen and new energy society
• /
• v.21 no.1
• /
• pp.64-71
• /
• 2010

This paper deals with an economic evaluation of domestic immersing type photoelectrochemical hydrogen production. We also make some sensitivity analysis of hydrogen production prices by changing the values of input factors such as the initial capital cost, the solar to hydrogen conversion efficiency, and the system duration time. The hydrogen production price of the immersing type photoelectrochemical system was estimated as 8,264,324 won/$kgH_2$. It is expected that the production cost by photoelectrochemical hydrogen production can be reduced to 26,961 won/$kgH_2$ if the solar to hydrogen conversion efficiency is increased to 14%, the system duration time is increased to 20,000 hours, and the initial capital cost is decreased to 10% of the current level. The photoelectrochemical hydrogen production is evaluated as uneconomical at this time, and we need to enhance the solar to hydrogen conversion efficiency and the system duration time as well as to reduce prices of the system facilities.

• Clean Technology
• /
• v.29 no.1
• /
• pp.53-58
• /
• 2023

This study shows the summary of the economic performance of excess electricity conversion to hydrogen as well as methane and returned conversion to electricity using a fuel cell. The methane production process has been examined in a previous study. Here, this study focuses on the conversion of methane to electricity. As a part of this study, capital expenditure (CAPEX) is estimated under various sized plants (0.3, 3, 9, and 30 MW). The study shows a method for economic optimization of electricity generation using a fuel cell. The CAPEX and operating expenditure (OPEX) as well as the feed cost are used to calculate the discounted cash flow. Then the levelized cost of returned electricity (LCORE) is estimated from the discounted cash flow. This study found the LCORE value was ¢10.2/kWh electricity when a 9 MW electricity generating fuel cell was used. A methane production plant size of 1,500 Nm³/hr, a methane production cost of $11.47/mcf, a storage cost of $1/mcf, and a fuel cell efficiency of 54% were used as a baseline. A sensitivity analysis was performed by varying the storage cost, fuel cell efficiency, and excess electricity cost by ±20%, and fuel cell efficiency was found as the most dominating parameter in terms of the LCORE sensitivity. Therefore, for the best cost-performance, fuel cell manufacturing and efficiency need to be carefully evaluated. This study provides a general guideline for cost performance comparison with LCORE.

• Proceedings of the KIPE Conference
• /
• 2011.11a
• /
• pp.199-200
• /
• 2011

Uninterruptible Power Supply(UPS) is largely divided into passive-standby, line-interactive and double-conversion methods. This paper proposes the double-conversion UPS for low cost and high performance. The proposed UPS are composed of PFC, inverter, battery charger and discharger. Finally, the validity of proposed UPS was verified by experiments.

• Journal of the Korea Institute of Building Construction
• /
• v.22 no.3
• /
• pp.317-326
• /
• 2022

With the development of various technologies in the area of artificial intelligence, a number of studies to application of artificial intelligence technology in the construction field are underway. Diverse technologies have been applied to the task of predicting construction costs, and construction cost prediction technologies applying artificial intelligence technologies have recently been developed. However, it is difficult to secure the vast amount of construction cost data required for machine learning, which has not yet been practically used. In this study, to predict the construction cost, the latest artificial neural network(ANN) method is used to propose a method to improve the construction cost prediction performance. In particular, to improve predictive performance, a log conversion method of target variables and a feature scaling method to eliminate the difference in the relative influence of each column data are applied, and their performance in predicting construction cost is compared and analyzed.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2007.11a
• /
• pp.425-434
• /
• 2007

The sponsored search has become significant channel of online advertising, and the large sized advertisers have appeared, so the sponsored search strategy is becoming more important. Since CPC(Cost-per-Click) advertising has different price according to keyword, it is difficult to manage the a lot of keywords at one time. So, the purpose of this study is to investigate the factors which influence on the cost-per-click of sponsored search advertising. That is, there are four factors: impression, CTR(Click through Rate), conversion rate, and keyword's length. for the regression analysis, we use the actual data which is gotten from an ad agency. The result of that, the impression and keyword's length influence cost-per-click positively. However, CTR & conversion rate have no influence on it unexpectedly.

• Journal of Preventive Medicine and Public Health
• /
• v.28 no.2 s.50
• /
• pp.487-496
• /
• 1995

This study was performed for the comparison of the therapeutic efficiency between 6-month (2HERZ/4HER) and 9-month (9HER) short-course chemotherapy under the programe conditions for pulmonary tuberculosis in terms of sputum AFB negative conversion rate, remedial interruption rate and cost effectiveness analysis. Two hundreds and ninty three patients treated with 9HER and 641 treated with 2HERZ/4HER had been discharged from 22 health centers in Seoul from May 1, 1993 to April 30, 1994. Seven hundreds and seventeen was subsequently analysed excluding 217 patients due to remedial interruption. The results : 1. Bacteriological negative conversion rate in 9HER regimen and 2HERZ/4HER regimen was 97.8% and 96.4% respectively(p>0.05). But the early treatment period, negative conversion rate in 2HERZ/4HER regimen was very higher than in 9HER regimen(p<0.01). 2. Remedial interruption rate for 9HER regimen and 2HERZ/4HER regimen was 34.1% and 13.6% respectively. The primary reason for the interruption was transfering to other clinics and this interruption was high within 3months. 3. Cost effectiveness for 2HERZ/4HER regimen was higher than 9HER regimen. The difference cost effectiveness ratio was 2.33 at the first sputum test and 1.69 at the last sputum test.

• Communications for Statistical Applications and Methods
• /
• v.16 no.6
• /
• pp.1031-1036
• /
• 2009

Under recent dramatic declines in response rates, various procedures have been considered among survey practitioners to reduce nonresponse in order to avoid its potential impairment to the inference. In the random digit dialing telephone surveys, substantial efforts are often required to obtain the initial contact for the screener interview. To reduce a burden with higher data collection costs, refusal conversion can be administered only to a random portion of the sample, reducing nonresponse (bias) with an expense of sample variability increment due to the associated weight adjustment. In this paper, we provide ways to determine the optimal subsampling rate using a linear cost model. Our approach for refusal subsampling is to predetermine a random portion from the full sample and to apply refusal conversion efforts if needed only to the subsample.

• Journal of the Korean Ceramic Society
• /
• v.55 no.4
• /
• pp.307-324
• /
• 2018

Rechargeable lithium-ion batteries (LIBs) have been rapidly expanding from IT based applications to uses in electric vehicles (EVs), smart grids, and energy storage systems (ESSs), all of which require low cost, high energy density and high power density. The increasing demand for LIBs has resulted in increasing price of the lithium source, which is a major obstacle to wider application. To date, the possible depletion of lithium resources has become relevant, giving rise to the interest in Na-ion batteries (NIBs) as promising alternatives to LIBs. A lot of transition metal compounds based on conversion-alloying reaction have been extensively investigated to meet the requirement for the anodes with high energy density and long life-time. In-depth understanding the electrochemical reaction mechanisms for the transition metal compounds makes it promising negative anode for NIBs and provides feasible strategy for low cost and large-scale energy storage system in the near future.

• Journal of the Optical Society of Korea
• /
• v.12 no.3
• /
• pp.131-135
• /
• 2008

Computational integral imaging(CII) has the advantage of generating the volumetric information of the 3D scene without optical devices. However, the reconstruction process of CII requires increasingly larger sizes of reconstructed images and then the computational cost increases as the distance between the lenslet array and the reconstructed output plane increases. In this paper, to overcome this problem, we propose a novel CII method using a depth conversion technique. The proposed method can move a far 3D object near the lenslet array and reduce the computational cost dramatically. To show the usefulness of the proposed method, we carry out the preliminary experiment and its results are presented.