Supercritical CO₂ Rankine cycles for waste heat recovery from gas turbine

Kim, Young Min,Sohn, Jeong Lak,Yoon, Eui Soo Elsevier 2017 ENERGY Vol.118 No.-

<P><B>Abstract</B></P> <P>A supercritical carbon dioxide (S-CO<SUB>2</SUB>) Rankine cycle for waste heat recovery (WHR) from a gas turbine can achieve high efficiency despite its simplicity and compactness in comparison to a steam/water cycle. With respect to WHR, it is very important to maximize the net output power by incorporating the utilization efficiency of the waste heat in conjunction with the cycle thermal efficiency. A simple S-CO<SUB>2</SUB> Rankine cycle used for a high-temperature source cannot fully utilize the waste heat because the working fluid is preheated by the recuperator to a high temperature to achieve a high cycle efficiency. To recover the remaining waste heat from a simple cycle, a cascade cycle with a low-temperature (LT) loop can be added to the high-temperature (HT) loop, or a split cycle—in which the flow after the pump is split and preheated by the recuperator and LT heater separately, before the HT heater can be used. This study presents a comparison of three cycles in terms of energy and exergy analyses of their systems. The results show that a split cycle can produce the highest power of the threes systems considered over a wide range of operating conditions. The reasons for this are explained in detail.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Optimization of supercritical CO<SUB>2</SUB> (S-CO<SUB>2</SUB>) Rankine cycle for gas turbine waste heat recovery (WHR). </LI> <LI> Simple, cascade, and split S-CO<SUB>2</SUB> Rankine cycles for gas turbine WHR. </LI> <LI> Energy and exergy analyses of S-CO<SUB>2</SUB> Rankine cycles. </LI> <LI> Heat recovery, cycle, and system efficiencies of S-CO<SUB>2</SUB> Rankine cycles for WHR. </LI> <LI> Effects of upper pressure of S-CO<SUB>2</SUB> Rankine cycles for WHR. </LI> </UL> </P>

해양온도차발전용 초월임계 이산화탄소 랭킨사이클의 열역학적 분석 및 최적화

김준성(Jun-Seong Kim),이진학(Jin-Hak Yi),김유택(You-Taek Kim) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.11

해양온도차발전은 해양의 표층수와 심층수의 온도차를 이용하여 발전하는 동력 사이클이다. 본 연구에서는 해양온도차발전용 초월임계 이산화탄소 랭킨사이클의 성능을 분석하고, 유전자 알고리즘을 이용한 최적화를 수행하였다. 단순 랭킨사이클과 개방형 재생 랭킨사이클을 고려하였으며, 초월임계 사이클로 구성하기 위하여 태양열을 이용한 해양온도차발전 시스템을 적용하였다. 분석결과, 초월임계 사이클에서 터빈입구온도가 높고, 열원출구온도가 낮을수록 엑서지 효율이 상승하였다. 터빈입구압력 및 개방형 재생 랭킨사이클의 중간압력에 따라 엑서지 효율은 비선형적이며, 최적화 지점이 존재하였다. 유전자 알고리즘을 이용하여 초월임계 사이클에서 다수의 독립변수를 모두 반영하여 최적 값을 산출하였다. 최적 값 분석결과, 단순 랭킨 사이클과 비교하여 개방형 재생 랭킨사이클의 엑서지 효율이 향상됨을 알 수 있었다. Ocean thermal energy conversion is a power cycle that generates power using the temperature difference between the surface water and deep water of the ocean. In this study, the performance analysis of a transcritical carbon dioxide Rankine cycle for ocean thermal energy conversion and optimization using genetic algorithms are conducted. A simple Rankine cycle and a Rankine cycle with a feed-liquid heater are considered, and a solar-boosted ocean thermal energy conversion system is applied to construct a transcritical cycle. From the results of the analysis, the exergy efficiency increased as the turbine inlet temperature increased, and the heat source outlet temperature was lower in the transcritical cycle. The exergy efficiency due to the turbine inlet pressure and the intermediate pressure of a Rankine cycle with a feed-liquid heater were nonlinear, and there was an optimization point. Then, the genetic algorithm calculated the optimal values by reflecting all of the independent variables in the transcritical cycle. From the results of the optimal value analysis, it was found that the exergy efficiency of a Rankine cycle with a feed-liquid heater was improved compared to that of a simple Rankine cycle.

해양 온도차발전 시스템의 열역학 사이클에 대한 연구

김남진(Kim Nam-Jin),신상호(Shin Sang-Ho),천원기(Chun Won-Gee) 한국태양에너지학회 2006 한국태양에너지학회 논문집 Vol.26 No.2

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℃. 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.

초임계 이산화탄소 브레이튼 사이클과 스팀 랭킨 사이클의 비교 및 특성 분석

김선진(Sun Jin Kim),이지성(Ji Sung Lee),김민수(Min Soo Kim) 대한설비공학회 2015 대한설비공학회 학술발표대회논문집 Vol.2015 No.11

해양지열발전용 다단재열랭킨사이클의 출력 및 효율 최적화 해석

차상원(S. W. Cha),이호생(H. S. Lee),김현주(H. J. Kim),문덕수(D. S. Mun) 한국해양환경·에너지학회 2013 한국해양환경·에너지학회 학술대회논문집 Vol.2013 No.11

지열수를 온열원으로 사용하고, 해양심층수를 냉열원으로 사용하는 바이너리 지열 발전시스템은 기존 지열 발전시스템의 효율을 증대하기 위한 재열과정과 터빈출력을 향상시키기 위한 다단과정을 각각 또는 복합적으로 적용하여 다단재열랭킨사이클의 성능개선을 검토하였다. 다단재열랭킨 사이클의 종류로는 다단 사이클, 다단 재생사이클, 다단 재열사이클이 있다. 작동유체는 R134a, R245fa를 적용하였으며 온배수의 온도가 65℃, 75℃, 85℃ 응축수는 5℃를 적용하였다. 본 논문에서는 온열원변화, 작동유체의 종류, 사이클의 종류에 따른 해양지열발전용 다단재열랭킨사이클의 출력 및 효율을 높이기 위한 최적화 해석을 수행하였다. 이를 열역학적 사이클로 모사하기 위한 Aspen HYSYS를 이용하여 해석을 진행 하였다. 작동유체는 R245fa가 R134a보다 우수한 성능을 보였으며, 밀폐사이클에서 온열원이 85℃일때에 출력은 236.9kW, 효율은 13.06%로 R134a보다 각 각 11.2%, 20.3% 높은 성능을 보였다. 다음으로 사이클의 종류 및 온열원의 변화에 따른 다양한 해석을 수행하였다. Binary geothermal generation system which utilizes the warm water in geothermal water for vaporization and the cold water in deep ocean water for condensation. The regeneration process increased the efficiency more than the existing geothermal generation system ,and the multi stage process also increased the power of the turbine. Improvement of the multi stage regeneration cycles study on these process respectively or together applied to the cycles. A kind of the cycles has multi stage cycle(MS), multi stage regeneration cycle(MSR), and multi two stage cycle(MTS). Working fluid was R134a and R245fa. Temperature of the warm water was the 65℃, 75℃, and 85℃. Temperature of the cold water was the 5℃. Optimization simulation was conducted for improving the gross power and efficiency with multi stage regeneration rankine cycle for ocean thermal energy conversion(OTEC) according to changing of a warm heat source, kind of the wokring fluid, and type of the cycle. Performance analysis of the various components was simulated by using the Aspen HYSYS for analysis of the thermodynamic cycle. R245fa shows great performance than R134a. The gross power of the R245fa was the 236.9kW, and the cycle efficiency was the 13.06% at 85 degree. Gross power and cycle efficiency of R245fa increased by 11.2%, 20.3% more than R134a. Various simulation was conducted about kind of the cycles and changing of the heat source.

VIABLE COMBINED CYCLE DESIGN FOR AUTOMOTIVE APPLICATIONS

김기범,K.-W. CHOI2,이기형 한국자동차공학회 2012 International journal of automotive technology Vol.13 No.3

A relatively new approach for improving fuel economy and automotive engine performance involves the use of automotive combined cycle generation technologies. The combined cycle generation, a process widely used in existing power plants, has become a viable option for automotive applications due to advances in materials science, nanotechnology, and MEMS (Mico-Electro Mechanical Systems) devices. The waste heat generated from automotive engine exhaust and coolant is a feasible heat source for a combined cycle generation system, which is basically a Rankine cycle in the context of this study. However, there are still numerous technical issues that need to be solved before the technology can be implemented in automobiles. A simulation was performed to examine the amount of waste energy that could be recovered through the use of a combined cycle system. A simulation model of the Rankine cycle was developed using Cycle-Tempo software. The simulation model was ultimately used to evaluate the rate of waste heat recovery and the consequential increase in the overall thermal efficiency of the engine with the combined cycle generation system under typical engine operating conditions. The most effective automotive combined cycle system recovered 68% of the waste heat from the exhaust and coolant, resulting in a 6% improvement in engine efficiency. The results are expected to be beneficial for evaluating the feasibility of combined cycle generation systems in automotive applications.

저온 열원 발전을 위한 암모니아-물 랭킨 사이클과 칼리나 사이클의 성능특성의 비교 해석

김경훈,배유근,정영관,김세웅 한국수소및신에너지학회 2018 한국수소 및 신에너지학회논문집 Vol.29 No.2

This paper presents a comparative analysis of thermodynamic performance of ammonia-water Rankine cycles with and without regeneration and Kalina cycle for recovery of low-temperature heat source. Special attention is paid to the effect of system parameters such as ammonia mass fraction and turbine inlet pressure on the characteristics of the system. Results show that maximum net power can be obtained in the regenerative Rankine cycle for high turbine inlet pressures. However, Kalina cycle shows better net power and thermal efficiency for low turbine inlet pressures, and the optimum ammonia mass fractions of Kalina cycle are lower than Rankine cycles.

Review of Organic Rankine Cycle experimental data trends

Park, Byung-Sik,Usman, Muhammad,Imran, Muhammad,Pesyridis, Apostolos Elsevier 2018 Energy conversion and management Vol.173 No.-

<P><B>Abstract</B></P> <P>Organic Rankine Cycle (ORC)-based systems are being extensively investigated for heat-to-electric power conversion from various sources, such as biomass, waste heat recovery, concentrated solar thermal and geothermal. The ORC technology has a promising future as it helps to meet energy requirements, arguably with a minimal environmental impact. This work summarizes the current state-of-the-art of actual i.e., experimental ORC system performance, derived from a comprehensive analysis of the most significant, relevant and up-to-date experimental data published in scientific literature. A survey of more than 200 scientific works is scrutinized according to specific selection criteria and data is extracted to develop a database containing thermodynamic cycle information along with component-level performance information. Performance trends are discussed and addressed as functions of first principles. One of the least surprising results indicate that the performance follows economies of scale. More revealing is the fact that the Organic Rankine Cycle conversion efficiency (mechanical to electrical) was around 70%. Furthermore, it becomes clear that there is a large gap between research and development for source and sink temperature differences above 150 °C. In general, the overall heat to electrical power conversion efficiency was around 44% of the Carnot cycle efficiency of the cycle. A host of other relevant thermodynamic parameters are cross-compared, as well as compared to theoretical results, allowing a level of practical ORC system design target homologation to be achieved which is useful for the engineer as well as the scientist in the design of ORC components, systems as well as advanced cycles.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Performance trends are discussed and addressed as functions of first principles. </LI> <LI> Majority of experimental ORC published work is below 10 kWe power. </LI> <LI> Heat to electrical power conversion efficiency is 44% of the Carnot cycle efficiency. </LI> <LI> R245fa was the most popular working fluid, followed by R123 and then R134a. </LI> <LI> The average values of Back-Work Ratio were 25.9% for ORC experiments. </LI> </UL> </P>

Analysis of Design and Part Load Performance of Micro Gas Turbine/Organic Rankine Cycle Combined Systems

Lee, Joon-Hee,Kim, Tong-Seop The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.9

This study analyzes the design and part load performance of a power generation system combining a micro gas turbine (MGT) and an organic Rankine cycle (ORC). Design performances of cycles adopting several different organic fluids are analyzed and compared with performance of the steam based cycle. All of the organic fluids recover greater MGT exhaust heat than the steam cycle (much lower stack temperature), but their bottoming cycle efficiencies are lower. R123 provides higher combined cycle efficiency than steam does. The efficiencies of the combined cycle with organic fluids are maximized when the turbine exhaust heat of the MGT is fully recovered at the MGT recuperator, whereas the efficiency of the combined cycle with steam shows an almost reverse trend. Since organic fluids have much higher density than steam, they allow more compact systems. The efficiency of the combined cycle, based on a MGT with 30 percent efficiency, can reach almost 40 percent. hlso, the part load operation of the combined system is analyzed. Two representative power control methods are considered and their performances are compared. The variable speed control of the MGT exhibits far better combined cycle part load efficiency than the fuel only control despite slightly lower bottoming cycle performance.

전력 및 담수생산을 위한 해양온도차발전에 대한 연구

박성식(Park Sung-Seek),김남진(Kim Nam-Jin) 한국태양에너지학회 2010 한국태양에너지학회 학술대회논문집 Vol.2010 No.4

Ocean Thermal Energy Conversion(OTEC) rower 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 R125, R143a, R410A and R32 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 rower 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%.