• 한국해양환경ㆍ에너지학회지
• /
• 제17권2호
• /
• pp.116-121
• /
• 2014

지열수를 온열원으로 사용하고, 해양심층수를 열침으로 사용하는 바이너리(binary) 지열 발전시스템은 기존 지열 발전시스템의 효율을 증대하기 위한 재열과정과 터빈출력을 향상시키기 위한 다단과정을 각각 또는 복합적으로 적용하여 다단재열재생사이클의 성능개선을 검토하였다. 사이클종류는 다단재열사이클(Multi Stage reheater cycle; MS), 다단재열재생사이클(Multi stage reheater regeneration cycle; MSR)이 있다. 작동유체는 R134a, R245fa를 적용하였으며 온열원의 온도가 $65^{\circ}C$, $75^{\circ}C$, $85^{\circ}C$ 열침은 $5^{\circ}C$를 적용하여 기본해석을 수행하였다. 본 논문에서는 온열원변화, 작동유체의 종류, 사이클의 종류에 따른 해양지열발전용 다단재열재생사이클의 출력 및 효율을 높이기 위한 해석을 수행하였다. 이를 열역학적 사이클로 모사하기 위한 상용 프로그램인 Aspen HYSYS(V8.0)를 이용하여 해석을 진행 하였다. 작동유체는 R245fa가 R134a보다 우수한 성능을 보였으며, 온열원의 변화와 각각의 사이클 종류에 따라 적절한 작동유체가 있음을 확인 할 수 있었다. 사이클의 출력 및 효율은 각각 MS사이클과 MSR사이클에서 좋은 성능을 나타냈다.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제16권4호
• /
• pp.451-462
• /
• 2016

Photovoltaic energy conversion becomes main focus of many researches due to its promising potential as source for future electricity and has many advantages than the other alternative energy sources like wind, solar, ocean, biomass, geothermal etc. In Photovoltaic power generation multilevel inverters play a vital role in power conversion. The three different topologies, diode-clamped (neutral-point clamped) inverter, capacitor-clamped (flying capacitor) inverter and cascaded h-bridge multilevel inverter are widely used in these multilevel inverters. Among the three topologies, cascaded h-bridge multilevel inverter is more suitable for photovoltaic applications since each pv array can act as a separate dc source for each h-bridge module. This paper presents a single phase Cascaded H-bridge five level inverter for grid-connected photovoltaic application using sinusoidal pulse width modulation technique. This inverter output voltage waveform reduces the harmonics in the generated current and the filtering effort at the input. The control strategy allows the independent control of each dc-link voltages and tracks the maximum power point of PV strings. This topology can inject to the grid sinusoidal input currents with unity power factor and achieves low harmonic distortion. A PID control algorithm is implemented in Arm Processor LPC2148. The validity of the proposed inverter is verified through simulation and is implemented in a single phase 100W prototype. The results of hardware are compared with simulation results. The proposed system offers improved performance over conventional three level inverter in terms of THD.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
• /
• pp.630-631
• /
• 2009

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Apart from wind and solar, ocean holds tremendous amount of untapped energy in forms such as geothermal vents, tides and waves. The current study looks at generating power using waves and the focus is on the primary energy conversion (first stage conversion) of incoming waves for two different models. Observation of flow characteristics, pressure and the velocity in the augmentation channel as well as the front guide nozzle are presented in the paper. A numerical wave tank was utilized to generate waves of desired properties and later the turbine section was integrated. The augmentation channel consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. The analysis was performed using the commercial CFD code.

• International Journal of Advanced Culture Technology
• /
• 제3권1호
• /
• pp.101-112
• /
• 2015

Renewable energy resources play an important part in the world's future. Renewable energy sources have the following components: biomass, geothermal, solar thermal, directs solar, wind, tidal and hydropower. Hydropower is still the most efficient way to generate electricity worldwide. Hydropower projects can contribute as a cheap energy source, as well to encourage the development of small industries across a wide range of new technology; furthermore hydropower systems use the energy in flowing and falling water to produce electricity or mechanical energy. Hydropower systems are classified as large, medium, small, mini and micro according to their installed power generation capacity, as do the following components: water turbines, control mechanisms and electrical transmissions. In this article a review of small hydropower systems has been done on the principles surrounding the fundamentals of hydraulic engineering, the fundamentals of hydrology, identification of sites and economic analysis.

• 한국재료학회지
• /
• 제25권10호
• /
• pp.523-530
• /
• 2015

Electricity generation through fossil fuels has caused environmental pollution. To solve this problem, research on new renewable energy (solar, wind, geothermal heat, etc.) to replace fossil fuels is in progress. These devices are able to consistently generate power. However, they have many drawbacks, such as high installation costs and limitations in possible set-up environments. Thus, piezoelectric harvesting technology, which is able to overcome the limitations of existing energy technologies, is actively being studied. Piezoelectric harvesting technology uses the piezoelectric effect which occurs in crystals that generate voltage when stress is applied. Therefore, it has advantages such as a wider installation base and lower technological cost. In this study, a piezoelectric energy harvesting device based on constant wave motion was investigated. This device can regenerate electricity in a constant turbulent flow in the middle of the sea. The components of the device are circuitry, a steel bar, an bimorph piezoelectric element and buoyancy elements. In addition, a multiphysical analysis coupled with the structure and piezoelectric elements was conducted to estimate the performance of the device. With this piezoelectric energy harvesting device, the displacement and electric power were analyzed.

• 터널과지하공간
• /
• 제23권6호
• /
• pp.480-492
• /
• 2013

비화산지대에서도 적용 가능한 인공저류층 생성방식의 지열발전기술의 등장으로 막대한 비용이 소요되는 대심도 시추공사를 효율적이고 경제적으로 수행하기 위한 연구개발의 필요성이 증대되고 있다. 그러나 시추공사는 수행과정에서 수많은 불확실한 사건이 발생하여 공기와 비용을 신뢰적으로 예측하기가 매우 어렵기 때문에 계획적이고 효율적으로 공사를 관리하기가 어려운 실정이다. 특히, 비트의 마모로 인해 이산적으로 발생하는 시추장비의 라운드 트립(round trip)은 심도가 깊어질수록 소요시간이 증가하여 공사 성능에 영향을 많이 끼치는 요소로서 발생시점과 깊이를 사전에 평가하여 최적화할 수 있는 기술이 필요하다. 본 연구에서는 비트의 마모상태를 총 8단계로 구분하여 마모단계별 라운드 트립이 발생되는 깊이와 시점을 분석할 수 있는 예측 알고리즘(TOSA)을 개발하였다. 시뮬레이션을 위한 단위구간을 분할할 수 있는 방법론을 제시하였으며, 구간별 시추속도 및 비트의 마모도 예측을 위한 방법으로 Bourgoyne and Young의 모델을 활용하였다. 마지막으로 사용자 편의성을 고려하여 개발된 알고리즘을 시스템화 하였다.

• 한국태양광발전학회지
• /
• 제6권1호
• /
• pp.56-68
• /
• 2020

Cameroon is a lower middle-income country with a population of 25.87 million inhabitants distributed over a surface area of 475,442 ㎢. Cameroon has very rich potentials in renewable energy resources such as solar energy, wind energy, small hydropower, geothermal energy and biomass. However, renewable energy constitutes less than 0.1% of energy mix of the country. The energy generation mix of Cameroon is dominated by large hydropower and thermal power. Cameroon ratified the Paris Agreement in July 2016 with an ambitious 20% greenhouse gas (GHG) emission reduction. This study attempts to investigate some renewable energy deployment policy-instruments that could enable the country enhance renewable energy deployment, gain energy independence, fulfill Nationally Determined Contribution (NDC) and achieve Sustainable Development Goals. It begins with an analysis of the status of energy sector in Cameroon. It further highlights the importance of renewable energy in mitigating climate change by decarbonizing the energy mix of the country to fulfill NDC and SDGs. Moreover, this study proposes some renewable energy deployment policy-solutions to the government. Solar energy is the most feasible renewable energy source in Cameroon. Feed-in Tariffs (FiT), is the best renewable energy support policy for Cameroon. Finally, this study concludes with some recommendations such as the necessity of building an Energy Storage System as well a renewable energy information and statistics infrastructure.

• 한국기계가공학회지
• /
• 제14권4호
• /
• pp.73-84
• /
• 2015

Electricity generation using fossil fuels has caused environmental pollution. To solve this problem, research on new renewable energy sources (solar, wind power, geothermal heat, etc.) to replace fossil fuels is ongoing. These devices are able to generate power consistently. However, they have many weaknesses, such as high installation costs and limits to possible setup environments. Therefore, an active study on piezoelectric harvesting technology that is able to surmount the limitations of existing energy technologies is underway. Piezoelectric harvesting technology uses the piezoelectric effect, which occurs in crystals that generate voltage when stress is applied. Therefore, it has advantages, such as a wider installation base and lower technological costs. In this study, a piezoelectric harvesting device imitating seaweed, which has a consistent motion caused by fluid, is used. Thus, it can regenerate electricity at sea or on a bridge pillar, which has a constant turbulent flow. The components of the device include circuitry, springs, an electric generator, and balancing and buoyancy elements. Additionally, multiphysics analysis coupled with fluid, structure, and piezoelectric elements is conducted using COMSOL Multiphysics to evaluate performance. Through this program, displacement and electric power were analyzed, and the actual performance was confirmed by the experiment.

• 한국태양에너지학회 논문집
• /
• 제39권6호
• /
• pp.137-151
• /
• 2019

This study estimated the available renewable market potential based on Levelized Cost Of Electricity and then assessed the renewable derived energy self-sufficiency for the unit of local government in South Korea. To calculate energy self-sufficiency, 1 km gridded market renewable generation and local government scale of final energy consumption data were used based on the market costs and statistics for the recent three years. The results showed that the estimated renewable market potentials were 689 TWh (Install capacity 829 GW, 128 Mtoe), which can cover 120% of power consumption. 55% of municipalities can fully replace the existing energy consumption with renewable energy generation and the surplus generation can compensate for the rest area through electricity trade. However, it was confirmed that, currently, 47% of the local governments do not fully consider all renewable energy sources such as wind, hydro and geothermal in establishing 100% renewable energy. The results of this study suggest that energy planning is decentralized, and this will greatly contribute to the establishment of power planning of local governments and close the information gap between the central government, the local governments, and the public.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
• /
• pp.61.2-61.2
• /
• 2015

In the past decades, green energy, such as solar energy, wind power, hydropower, biomass energy, geothermal energy, and so on, has been widely investigated and developed to solve energy shortage. Recently, organic solar cells have attracted much attention, because they have many advantages, including low-cost, flexibility, light weight, and easy fabrication [1-3]. Organic solar cells are as a potential candidate of the next generation solar cells. In this abstract, to improve the power conversion efficiency and the stability, the inverted polymer solar cells with various structures were developed [4-6]. The novel cell structures included the P3HT:PCBM inverted polymer solar cells with AZO nanorods array, with pentacene-doped active layer, and with extra P3HT interfacial layer and PCBM interfacial layer. These three difference structures could respectively improve the performance of the P3HT:PCBM inverted polymer solar cells. For the inverted polymer solar cells with AZO nanorods array as the electronic transportation layer, by using the nanorod structure, the improvement of carrier collection and carrier extraction capabilities could be expected due to an increase in contact area between the nanorod array and the active layer. For the inverted polymer solar cells with pentacene-doped active layer, the hole-electron mobility in the active layer could be balanced by doping pentacene contents. The active layer with the balanced hole-electron mobility could reduce the carrier recombination in the active layers to enhance the photocurrent of the resulting inverted polymer solar cells. For the inverted polymer solar cells with extra P3HT and PCBM interfacial layers, the extra PCBM and P3HT interfacial layers could respectively improve the electron transport and hole transport. The extra PCBM interfacial layer served another function was that led more P3HT moving to the top side of the absorption layer, which reduced the non-continuous pathways of P3HT. It indicated that the recombination centers could be further reduced in the absorption layer. The extra P3HT interfacial layer could let the hole be more easily transported to the MoO3 hole transport layer. The high performance of the novel P3HT:PCBM inverted polymer solar cells with various structures were obtained.