• 한국시뮬레이션학회논문지
• /
• 제30권1호
• /
• pp.113-126
• /
• 2021

미래 에너지 소비 패턴은 신재생 에너지 등의 분산 전원의 증가와 프로슈머의 탄생 등으로 현재와는 크게 다른 양상을 보일 것이다. 이에 따라서 전력망 전체의 안정성 및 소비 효율을 고려한 적절한 생산 및 공급 계획 수립의 방향성 역시 지금과는 상이할 것으로 예측할 수 있다. 본 논문은 앞으로 발생할 수 있는 여러 환경에 직면하였을 때 새로운 운영 전략을 시험할 수 있는 시뮬레이션 모델을 제안한다. 제안된 모델을 통해서 에너지 저장 장치, 에너지 분산자원과 같은 새로운 개념이 다량 추가될 미래 스마트 그리드(Smart Grid) 환경에서 소비되고 공급되는 전력을 모의하고 분석하는 기능을 수행할 수 있다. 특히, 그리드에 존재하는 각 요인(Agent)별 의사결정을 모델링할 수 있는 ABM(Agent-Based Model) 방법론 중 DEVS 형식론을 이용하여 복잡한 시스템을 구조적으로 모델링하고, 여러 요인들을 그리드에 쉽게 추가할 수 있도록 하였다. 본 시뮬레이션 모델은 현 상황에서 주어진 데이터셋을 이용하여 검증하였고, 추가로 스마트 그리드의 주요 요소 중 하나인 에너지 저장 장치(ESS)를 본 모델에 간단하게 추가함으로써 시나리오 분석을 시행하였다.

• 한국수소및신에너지학회논문집
• /
• 제30권1호
• /
• pp.21-28
• /
• 2019

Reversible solid oxide fuel cell (ReSOC) system was integrated with waste steam for electrical energy storage in distributed energy storage application. Waste steam was utilized as external heat in SOEC mode for higher hydrogen production efficiency. Three system configurations were analyzed to evaluate techno-economic performance. The first system is a simple configuration to minimize the cost of balance of plant. The second system is the more complicated configuration with heat recovery steam generator (HRSG). The third system is featured with HRSG and fuel recirculation by blower. Lumped models were used for system performance analyses. The ReSOC stack was characterized by applying area specific resistance value at fixed operating pressure and temperature. In economical assessment, the levelized costs of energy storage (LCOS) were calculated for three system configurations based on capital investment. The system lifetime was assumed 20 years with ReSOC stack replaced every 5 years, inflation rate of 2%, and capacity factor of 80%. The results showed that the exergy round-trip efficiency of system 1, 2, 3 were 47.9%, 48.8%, and 52.8% respectively. The high round-trip efficiency of third system compared to others is attributed to the remarkable reduction in steam requirement and hydrogen compression power owning to fuel recirculation. The result from economic calculation showed that the LCOS values of system 1, 2, 3 were 3.46 ¢/kWh, 3.43 ¢/kWh, and 3.14 ¢/kWh, respectively. Even though the systems 2 and 3 have expensive HRSG, they showed higher round-trip efficiencies and significant reduction in boiler and hydrogen compressor cost.

• Nuclear Engineering and Technology
• /
• 제40권6호
• /
• pp.467-476
• /
• 2008

To keep the superconducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as thermal shields (TS), magnet structures, SC bus-lines (BL), and current leads (CL) must be maintained at their respective cryogenic temperatures. A helium refrigeration system (RRS) with an exergetic equivalent cooling power of 9 kW at 4.5 K without liquid nitrogen ($LN_2$) pre-cooling has been manufactured and installed. The main components of the KST AR helium refrigeration system (HRS) can be classified into the warm compression system (WCS) and the cryogenic devices according to the operating temperature levels. The process helium is compressed from 1 bar to 22 bar passing through the WCS and is supplied to cryogenic devices. The main components of cryogenic devices are consist of cold box (C/B) and distribution box (D/B). The C/B cool-down and make the various cryogenic helium for the KSTAR Tokamak and the various cryogenic helium is distributed by the D/B as per the KSTAR requirement. In this proceeding, we will present the commissioning results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated.

• 동력기계공학회지
• /
• 제20권4호
• /
• pp.52-62
• /
• 2016

Nowadays, emissions of a vehicle are been getting by testing on a chassis dynamometer and a test modes. Also, fuel efficiency is calculated by carbon-balance method that is applying the emissions(CO, THC and $CO_2$) to the fuel calculation formular. In Korea, before 2014, the formular did not include the fuel factors (density, net heat value and carbon weight fraction), but the constants were based on the fuel properties of 2000s. So, this formular did not consider a characteristic of test fuel property that was changed when progressing fuel efficiency test. The characteristics of test fuel property which was distributed in domestic have a difference of quality depending on production regions and oil-refining facilities. Because the fuel properties are variable value during refineries, crude oils and blending contents of a bio-fuel, vehicle fuel is changed for each test. Therefore, the fuel qualities need to apply for a fuel economy test. In this paper, changing patterns of a fuel properties were reviewed during history of fuel standards. Also, the appropriateness of the methods was discussed by calculating and comparing fuel economies with the fuel factors and the constants.

• 전기학회논문지
• /
• 제64권2호
• /
• pp.228-231
• /
• 2015

In power system research fields, one of current key issues is the construction and commercialization of micro grid site which is called green island, carbon zero island, energy independent island, building micro grid, etc. and various affiliated technologies have been being vigorously developed to realize. In addition, various researches about electric vehicles (EVs) are in progress and it is expected to penetrate rapidly with the next a few years. Some new load models should be developed integrating with electric vehicle loads because the EVs' deployment could cause the change of load composition rate on power system planning and operations. EVs are also resources for micro grid as well as distributed generation and demand response so that various supply and demand side resources should be considered for micro grid researches. In this paper, the load composition rate of residential sectors is prospected considering the deployment of EVs and the resource configuration of micro grid is optimized based on net present cost. In the optimization, the load patten of case studies includes EV's charging characteristics and various cases are simulated comparing micro grid environment and normal condition. HOMER is used to compare various cases and economic effects.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2012년도 춘계학술발표대회
• /
• pp.58.2-58.2
• /
• 2012

Heavy hydrocarbon reforming is a core technology for "Dirty energy smart". Heavy hydrocarbons are components of fossil fuels, biomass, coke oven gas and etc. Heavy hydrocarbon reforming converts the fuels into $H_2$-rich syngas. And then $H_2$-rich syngas is used for the production of electricity, synthetic fuels and petrochemicals. Energy can be used efficiently and obtained from various sources by using $H_2$-rich syngas from heavy hydrocarbon reforming. Especially, the key point of "Dirty energy smart" is using "dirty fuel" which is wasted in an inefficient way. New energy conversion laboratory of KAIST has been researched diesel reforming for solid oxide fuel cell (SOFC) as a part of "Dirty energy smart". Diesel is heavy hydrocarbon fuels which has higher carbon number than natural gas, kerosene and gasoline. Diesel reforming has difficulties due to the evaporation of fuels and coke formation. Nevertheless, diesel reforming technology is directly applied to "Dirty fuel" because diesel has the similar chemical properties with "Dirty fuel". On the other hand, SOFC has advantages on high efficiency and wasted heat recovery. Nippon oil Co. of Japan recently commercializes 700We class SOFC system using city gas. Considering the market situation, the development of diesel reformer has a great ripple effect. SOFC system can be applied to auxiliary power unit and distributed power generation. In addition, "Dirty energy smart" can be realized by applying diesel reforming technology to "Dirty fuel". As well as material developments, multidirectional approaches are required to reform heavy hydrocarbon fuels and use $H_2$-rich gas in SOFC. Gd doped ceria (CGO, $Ce_{1-x}Gd_xO_{2-y}$) has been researched for not only electrolyte materials but also catalysts supports. In addition, catalysts infiltrated electrode over porous $La_{0.8}Sr_{0.2}Ga_{0.8}Mg_{0.2}O_3-{\delta}$ and catalyst deposition at three phase boundary are being investigated to improve the performance of SOFC. On the other hand, nozzle for diesel atomization and post-reforming for light-hydrocarbons removal are examples of solving material problems in multidirectional approaches. Likewise, multidirectional approaches are necessary to realize "Dirty energy smart" like reforming "Dirty fuel" for SOFC.

• 한국태양에너지학회:학술대회논문집
• /
• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
• /
• pp.259-264
• /
• 2009

Most of the fossil power plants firing lower grade coals are challenged with maintaining good combustion conditions while maximizing generation and minimizing emissions. In many cases significant derate, availability losses and increase in unburned carbon levels can be attributed to poor combustion conditions as a result of poorly controlled local fuel and air distribution within the boiler furnace. The poor combustion conditions are directly related to the gas flow deviation in upper furnace and convection tube-bank but a less reported issue related to in large-scale oppose wall fired boilers. In order to develop a on-line combustion monitoring system and suggest an alternative heat flux estimation method at tube bank, which is very useful information for boiler design tool and blower optimizing system, field test was conducted at operating power boiler. During the field test the exhaust gases' temperature and tube metal temperature were monitored by using a spatially distributed sensors grid which located in the boiler's high temperature vestibule region. At these locations. the flue gas flow is still significantly stratified, and air in-leakage is minimal which enables tracing of poor combustion zones to specific burners and over-fire air ports. Test results showed that the flue gas monitoring method is more proper than metal temperature distribution monitoring for real time combustion monitoring because tube metal temp. distribution monitoring method is related to so many variables such as flue gas, internal flow unbalance, spray etc., Heat flux estimation at the tube bank with flue gas temp. and metal temp. data can be alternative method when tube drilling type sensor can't able to use.

• 한국통신학회논문지
• /
• 제40권2호
• /
• pp.298-306
• /
• 2015

본 논문에서는 위성/지상 겸용 망에서 위성 망과 지상 망간 주파수를 효율적으로 공유할 수 있도록 기여하는 최적의 자원 할당 방식에 대한 성능을 비교 분석한다. 제안된 방식은 동일한 주파수를 사용하는 위성 빔과 인접 빔 내 지상 셀 시스템 간 발생할 수 있는 간섭을 경감시킴과 동시에 망 내 발생한 트래픽 요구량을 만족시키기 위해 필요한 전력을 최적화하여 주파수 자원 이용 효율을 향상시킬 수 있다. 이와 같은 겸용 망에서는 각 시스템 간 상이한 트래픽 환경 및 업/하향링크 환경에 따라 주파수를 공유하는 위성과 지상 시스템 간 간섭 환경이 달라질 수 있다. 따라서 본 논문에서는 위성/지상 겸용 망에서의 업/하향링크 환경을 가정한 성능을 비교 분석함으로써 보다 실제 통신 환경에서의 제안된 알고리즘에 대한 성능의 우수성을 보인다.

• 조명전기설비학회논문지
• /
• 제23권12호
• /
• pp.176-183
• /
• 2009

대형병원의 에너지 소비패턴을 분석한 후 마이크로가스터빈을 적용할 경우 기존 시스템 대비 냉난방에너지 절감량 및 전기에너지 절감량과 경제성분석을 통해 대형병원의 에너지 소비량을 절감하기 위한 에너지성능평가 모의연구를 수행하였다. 0.5[MW]급 마이크로 가스터빈을 설치한 후 에너지 성능분석을 한 결과 터빈에서의 발전효율은 30[%]이며, 전기는 건물에서 사용되는 조명에너지 뿐만 아니라 전체 전기에너지의 40[%]을 절감할 수 있는 것으로 분석되었다. 또한 터빈에서 발전되는 전기량과 배열을 냉난방에너지원으로 이용할 경우 전체 시스템효율은 70[%]로 상승할 뿐만 아니라 난방에너지의 56[%], 냉방에너지의 67[%]를 절감할 수 있는 것으로 분석되었으며 현가등가법에 의한 시스템 투자회수 기간이 약 9년으로 분석되었다.

• 동력기계공학회지
• /
• 제22권6호
• /
• pp.67-73
• /
• 2018

Gasoline that meets the quality standards is distributed in Korea. However, consumers who use toluene or solvent mixed with gasoline have appeared due to rising crude oil prices and for the purpose of tax evasion. Gasoline quality standard is enacted by the domestic and international research reference. A wrong fuel can influence automobile performance or environmental issue. Thus, empirical data from this issue is necessary. Therefore, this research observed catalyst influence by gasoline property change and inspect influence of environment. In this study, fuel property evaluation, lean-burn evaluation, and real vehicle exhaust emission test were performed. In the result of fuel property, the fuel "A" was measured to be up to 27% less octane than the normal gasoline and the distillation property was measured 24% higher than normal gasoline. In the test result of single cylinder engine lean-burn test, the fuels "A" and "B" show torque value 20% less than the normal gasoline. As a result of vehicle test using the catalyst, the fuel "A" was increased more than the normal gasoline with 83% THC, 1,806% CO and 128% NOx, and the fuel "B" was increased more than normal gasoline with 1.6% THC, 391% CO and 142% NOx.