Dissertations / Theses: 'Supercritical CO2 power cycle'

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Freas, Rosemarv M. "Analysis of required supporting systems for the Supercritical CO2 power conversion system." Thesis, Cambridge Massachusetts Institute of Technology, 2007. http://hdl.handle.net/10945/2992.

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Recently, attention has been drawn to the viability of using S-CO(2) as a working fluid in modern reactor designs. Near the critical point, CO2 has a rapid rise in density allowing a significant reduction in the compressor work of a closed Brayton Cycle. Therefore, 45% efficiency can be achieved at much more moderate temperatures than is optimal for the helium Brayton cycles. An additional benefit of the S-CO2 system is its universal applicability as an indirect secondary Power Conversion System (PCS) coupled to most GEN-IV concept reactors, as well as fusion reactors. The United States DOE's GNEP is now focusing on the liquid Na cooled primary as an alternative to conventional Rankine steam cycles. This primary would also benefit from being coupled to an S-CO2 PCS. Despite current progress on designing the S-CO2 PCS, little work has focused on the principal supporting systems required. Many of the required auxiliary systems are similar to those used in other nuclear or fossil-fired units; others have specialized requirements when CO2 is used as the working fluid, and are therefore given attention in this thesis. Auxiliary systems analyzed within this thesis are restricted to those specific to using CO2 as the working fluid. Particular systems discussed include Coolant Make-up and Storage, Coolant Purification, and Coolant Leak Detection.
Contract number: N62271-97-G-0026.
US Navy (USN) author

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Zhao, Qiao. "Conception and optimization of supercritical CO2 Brayton cycles for coal-fired power plant application." Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0080/document.

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L'amélioration des systèmes énergétiques est considérée comme un levier technologique pour répondre aux défis liés à la croissance de la demande d’électricité et des émissions des gaz à effet de serre. Les futures centrales devraient présenter une intégration thermique plus flexible et des sources de chaleur mixtes possibles. Une des solutions fiables consiste à utiliser un cycle de Brayton au CO2 supercritique (CO2-SC), un tel cycle à haut rendement est théoriquement prometteur pour les applications nucléaires, fossiles et solaires thermiques. Un des principaux obstacles au déploiement du cycle de Brayton au CO2-SC est de justifier sa faisabilité, sa viabilité et son potentiel à l’échelle industrielle. Dans ce contexte deux axes de recherche ont été identifiées : • Une sélection rigoureuse de l’équation d’état qui permet de représenter les propriétés d’intérêt du CO2-SC. • Une nouvelle méthodologie pour l’optimisation des centrales électriques, permettant de sélectionner automatiquement le procédé optimal parmi une grande quantité de configurations possibles (dénomme superstructure). Les résultats de la première partie de cette thèse mettent en lumière que l’équation de SW est pertinente pour limiter l’impact de l’imprécision de l’équation d’état sur le dimensionnement du procédé. Dans cette thèse, un simulateur de procédé commercial, ProSimPlus a été combiné avec un solveur type évolutionnaire (MIDACO) afin d’effectuer des optimisations superstructure. Premièrement, le critère d’optimisation est de maximiser le rendement énergétique du procédé. Dans un deuxième temps, on cherche simultanément à minimiser les coûts du procédé. Pour ce faire, des fonctions de coût internes à EDF ont été utilisées afin de permettre l’estimation des coûts d'investissement (CAPEX), des dépenses opérationnelles (OPEX) et du coût actualisé de l'électricité (LCOE)
Efficiency enhancement in power plant can be seen as a key lever in front of increasing energy demand. Nowadays, both the attention and the emphasis are directed to reliable alternatives, i.e., enhancing the energy conversion systems. The supercritical CO2 (SC-CO2) Brayton cycle has recently emerged as a promising solution for high efficiency power production in nuclear, fossil-thermal and solar-thermal applications. Currently, studies on such a thermodynamic power cycle are directed towards the demonstration of its reliability and viability before the possible building of an industrial-scale unit. The objectives of this PhD can be divided in two main parts: • A rigorous selection procedure of an equation of state (EoS) for SC-CO2 which permits to assess influences of thermodynamic model on the performance and design of a SC-CO2 Brayton cycle. • A framework of optimization-based synthesis of energy systems which enables optimizing both system structure and the process parameters. The performed investigations demonstrate that the Span-Wagner EoS is recommended for evaluating the performances of a SC-CO2 Brayton cycle in order to avoid inaccurate predictions in terms of equipment sizing and optimization. By combining a commercial process simulator and an evolutionary algorithm (MIDACO), this dissertation has identified a global feasible optimum design –or at least competitive solutions– for a given process superstructure under different industrial constraints. The carried out optimization firstly base on cycle energy aspects, but the decision making for practical systems necessitates techno-economic optimizations. The establishment of associated techno-economic cost functions in the last part of this dissertation enables to assess the levelized cost of electricity (LCOE). The carried out multi-objective optimization reflects the trade-off between economic and energy criteria, but also reveal the potential of this technology in economic performance

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Riotto, Antonio. "Analisi termodinamica di cicli di potenza complessi a CO2 supercritica." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22430/.

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La finalità di questo lavoro di tesi è la valutazione quantitativa delle prestazioni dei cicli Brayton a CO2 supercritica. Per dare fondamento alle motivazioni che spingono ad un tale studio, il punto di partenza è stato analizzare la statistica riguardante le potenzialità del calore di scarto. Un passo ulteriore è stato non solo quantificare l’energia recuperabile, ma anche avere tabulati con le temperature alle quali tali energie sono disponibili in un panorama industriale che coinvolge diversi settori produttivi. Per ogni settore produttivo è stato possibile anche associare, ad un suo j-esimo processo, una fascia di temperatura alla quale il fluido viene scartato, come liquido o come gas. Successivamente, è stato necessario mettere in luce le proprietà della CO2 . Esso si mostra infatti compatibile con un utilizzo all’interno di un ciclo Brayton, e può anche presentare dei vantaggi rispetto ai fluidi dei cicli tradizionali: la sua densità è grande a tal punto da ottenere impianti con potenze in uscita elevate e ingombri particolarmente ridotti. Si è passati poi ad una rassegna di tre layout, uno semplice e due più complessi, studiati da più autori, con conclusioni complementari. Il capitolo successivo, quello della simulazione dei cicli di potenza in ambiente Aspen Hysys, è stato suddiviso in due parti. Nella prima parte sono presenti istruzioni più di carattere operativo per l’utilizzo del software. Nella seconda parte vengono invece mostrati i risultati delle simulazioni, con l’obiettivo di massimizzare il rendimento totale di recupero termico ηtot . Tale obiettivo è stato conseguito al variare di alcuni parametri, come temperatura di ingresso dei fumi nello scambiatore principale (Tfumi), temperatura di ingresso in turbina ( TIT ), pressione massima di ciclo (pmax), e potenza netta erogata dall’impianto ( Pnet ).

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Stene, Henrik Sørskår, and Ole Marius Moen. "Power Plant with CO2 Capture based on PSA Cycle." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26240.

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Two coal-fired power plants with CO2 capture by Pressure Swing Adsorption (PSA) havebeen modeled and simulated. The two power plants considered were IntegratedGasification Combined Cycle (IGCC) and conventional Pulverized Coal Combustion (PCC). Amathematical model of the PSA process for each of the power plants was developed and thegoal was to evaluate the feasibility of PSA as a technology for decarbonisation. Theperformance with CO2 capture by PSA was compared to a reference plant without CO2capture and to a power plant with CO2 capture by absorption, which is considered as thebenchmark technology. The size and number of the PSA columns were estimated todetermine the footprint.For the PCC power plant, the PSA model was a two-stage process consisting of a front and a tail stage. Two-stages mean that it consisted of two consecutive PSA processes. The front stage was a three-bed, five-step Skarstrom process with rinse. The tail stage was a two-bed, five-step Skarstrom process with pressure equalization. Zeolite 5A was used as adsorbent. For a specified capture rate of 90.0 %, the process achieved a purity of 96.4 % and a specific power consumption of 1.3 MJ/kgCO2. The net plant efficiency dropped 16.6 percentage points from 45.3 % to 28.7 % when introducing CO2 capture by PSA. In comparison, the PCC plant using absorption achieved a net plant efficiency of 33.4 %. The results indicate that the current state of the art PSA technology for decarbonisation as an alternative to absorption is not realistic for PCC power plants.For the IGCC power plant, the PSA model was a seven-bed, twelve-step Skarstromconfiguration with four pressure equalization steps using activated carbon as adsorbent. The process achieved a purity of 87.8 % and a capture rate of 86.3 % with negligible power consumption. The PSA process did not satisfy the performance targets of 90 % recovery and 95.5 % purity, and due to the low purity it is uncertain whether or not transport and storage of CO2 is at all feasible. The net plant efficiency dropped 12.5 percentage points from 47.3 % to 34.8 %. In comparison the IGCC plant with absorption achieved a net plant efficiency of 36.4 %. The results showed that PSA as a capture technology for IGCC power plants could not perform quite as well as absorption. However, PSA as a capture technology could have a potential if the purity could be increased, and is therefore more promising than PSA for PCC power plants.

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Wangen, Dan Jakob. "Life Cycle Assessment of Power Generation Technologies with CO2 Capture." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19393.

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Carbon Capture and Storage has large a potential to mitigating the CO2 emissions caused by fossil fuel powered power plants. CCS reduces the energy efficiency of the plant and increases the demand on chemicals and infrastructure. It is though not only the direct emissions from the power plants that have an impact on the environment. The entire supply chain of the power plant has an impact, and it is therefore necessary to evaluate the entire life cycle of the plant. This thesis consists of a full process LCA of post-combustion absorption based carbon capture and storage (CCS) technologies for both coal power plants and natural gas power plants. The assessed CCS technologies are based on the solvents MEA, MDEA and chilled ammonia. MEA is the most commonly used solvent in post-combustion capture, while MDEA and chilled ammonia represents novel CCS technologies that are still under development. It was shown that a 90% capture rate was possible for all of the assessed capture technologies. It was further shown that the total global warming potential (GWP) could be decreased with above 60%. 90% reduction is not possible because of indirect emissions in the supply chain. The reduction in GWP comes at a cost of decreasing energy efficiency, which further leads to an increase in consumption of materials and infrastructure. This causes the non-GHG related impacts to increase, compared to a base scenario without CCS. CCS technology based on MDEA was calculated to be the technology with the lowest impact, mainly because it has the lowest energy requirement. Chilled ammonia was assessed as the technology with the largest impacts. The reason for this is that the chilling process is very energy intensive and therefore decreases the efficiency more, compared to the other technologies assessed. Also the large emissions of ammonia have a large impact on the acidification potential and the marine eutrophication potential.

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Gibbs, Jonathan Paul. "Power conversion system design for supercritical carbon dioxide cooled indirect cycle nuclear reactors." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44765.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008.
"June 2008."
Includes bibliographical references.
The supercritical carbon dioxide (S-CO₂) cycle is a promising advanced power conversion cycle which couples nicely to many Generation IV nuclear reactors. This work investigates the power conversion system design and proposes several "Third Generation" plant layouts for power ratings ranging between 20 and 1200 MWe for the recompression cycle. A 20 MWe simple cycle layout was also developed. The cycle designs are characterized by a dispersed component layout in which a single shaft turbomachinery train is coupled to parallel arrays of multiple printed circuit heat exchanger modules. This configuration has arrangement benefits in terms of modularity, inspectability, repairability and replaceability. Compared to the prior second generation dispersed layouts, its lower ductwork pressure drop confers approximately 2% higher thermal efficiency. Two alternative S-CO₂ cycle designs for medium power applications were developed using an in-house optimization computer code and Solid Edge software. The first design is a recompression cycle derived from the 300 MWe design developed at MIT for Generation IV reactors. The design employs one turbine, two compressors (main and recompression) working in parallel and two recuperators (high and low temperature) and maximizes cycle efficiency while striving for a small plant footprint. The second design is a simple S-CO₂ power cycle, which has only one turbine, one compressor, and one recuperator. The main focus of the simple S-CO₂ design is cycle compactness and simplicity while achieving still attractive efficiency. Extensive sensitivity studies were performed for both the medium power recompression and simple S-CO₂ cycles to reveal areas for performance improvement, or performance degradation. Cycle efficiency is most sensitive to turbine inlet temperature.
(cont.) Peak cycle pressure is also an important parameter affecting cycle efficiency, although to a smaller extent than turbine inlet temperature. Higher pressure gives higher efficiency, but this gradually saturates around 28 MPa. Other sensitivity studies included turbomachinery performance, cooling water temperature, and heat exchanger fouling and plugging The reference parameters chosen are a 650°C turbine inlet temperature and 20 MPa peak cycle pressure (compressor outlet) because they reach a high thermodynamic efficiency (~/~47-48%) while staying within materials limitations. In order to couple the cycle to many of the Generation IV nuclear reactors a second reference case was chosen with a turbine inlet temperature of 550°C and a peak cycle pressure of 20 MPa.
by Jonathan Paul Gibbs.
S.M.

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THORSSON, BJÖRN J., and HADY R. SOLIMAN. "Supercritical Carbon Dioxide Brayton Cycle for Power Generation : Utilizing Waste Heat in EU Industries." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-282919.

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The industrial sector accounts for approximately 30% of the global total energy consumption and up to 50% of it is lost as waste heat. Recovering that waste heat from industries and utilizing it as an energy source is a sustainable way of generating electricity. Supercritical CO2 (sCO2) cycles can be integrated with various heat sources including waste heat. Current literature primarily focuses on the cycle’s performance without investigating the economics of the system. This is mainly due to the lack of reliable cost estimates for the cycle components. Recently developed cost scaling models have enabled performing more accurate techno-economic studies on these systems. This enables a shift in focus from plant efficiency to economics as a driver for commercialization of sCO2 technology. This work aims to develop a techno-economic model for these waste-heat-to-power systems. Based on the literature, waste heat from different industries is calculated, showing that the four industries with the greatest potential for waste heat recovery are cement, iron and steel, aluminum and gas compressor stations. Six different sCO2 cycle configurations were developed and simulated for these four industries. The techno-economic model optimizes for the highest Net Present Value (NPV) using an Artificial Bee Colony algorithm. The optimization variables are the pressure levels, split ratios, recuperators effectiveness, condenser temperature and the turbine inlet temperature limited by the heat source. The results show a vast potential for industries to cut down costs using this system. Out of the four industries modeled, a waste heat recovery system in an iron and steel factory yielded the highest NPV. Results show that the integration of sCO2 cycle in the cement industry could help reduce their waste heat by 60%, whilst simultaneously enabling them to cover up to 56% of their electricity demand. The payback period for the four industries varies between 6 to 9 years. Furthermore, simple recuperated sCO2 cycles with preheating are more economical than recompression cycles. Even though recompression cycles have higher thermal efficiency, they are limited by the temperature glide in the waste heat exchanger. This analysis could help investors and engineers take more informed decisions to increase the efficiency and economic return on investment for sCO2 cycles and heat recovery at industrial sites. To encourage adoption of supercritical CO2 cycles, a demo is needed along with more research for higher temperature applications with special attention to mechanical integrity.
Industrisektorn står för cirka 30% av den globala totala energiförbrukningen och upp till 50% av den går förlorad som spillvärme. Återskapa att spillvärme från industrier och använda det som energikälla är ett hållbart sätt att producera el. Superkritiska CO2 (sCO2) cykler kan integreras med olika värmekällor inklusive spillvärme. Nuvarande litteratur fokuserar främst på cykelens prestanda utan att undersöka systemets ekonomi. Detta beror främst på bristen på tillförlitliga kostnadsberäkningar för cykelkomponenterna. Baserat på nyligen utvecklade kostnadsskalningsmodeller är det möjligt att utföra mer exakta teknikekonomiska studier på dessa system. Detta möjliggör en förskjutning i fokus från cykeleffektivitet till ekonomi som drivkraft för kommersialisering av sCO2 teknologi. Detta arbete syftar till att utveckla en teknisk ekonomisk modell för dessa avfall-värme-till-kraftsystem. Baserat på litteraturen beräknas spillvärme från olika industrier, vilket visar att de fyra industrierna med störst potential för återvinning av spillvärme är cement, järn och stål, aluminium och gaskompressorstationer. Sex olika sCO2 konfigurationer utvecklades och simulerades för dessa fyra industrier. Den teknisk-ekonomiska modellen optimerar för det högsta Net Present Value (NPV) med hjälp av en artificiell bi-kolonialgoritm. Optimeringsvariablerna är pressure levels, delade förhållanden, recuperatorseffektivitet, kondensortemperatur och turbininloppstemperaturen begränsad av värmekällan. Resultaten visar en stor potential för industrier att sänka kostnaderna med detta system. Av de fyra modellerna industrin gav ett återvinningssystem i en järn och stålfabrik den högsta NPV. Resultaten visar att integrationen av sCO2 cykeln i cementindustrin kan bidra till att minska deras spillvärme med 60%, samtidigt som de gör det möjligt för dem att täcka upp till 56% av deras elbehov. Återbetalningsperioden för de fyra branscherna varierar mellan 6 till 9 år. Dessutom är simple recuperated sCO2 cykler med förvärmning mer ekonomiska än recompressioncykler. Trots att recompressioncykler har högre termisk effektivitet, begränsas de av temperaturglidningen i spillvärmeväxlaren. Denna analys kan hjälpa investerare och ingenjörer att fatta mer informerade beslut för att öka effektiviteten och ekonomiska avkastningen på investeringar för sCO2 cykler och värmeåtervinning på industriområden. För att uppmuntra antagandet av superkritiska CO2 cykler krävs en demo tillsammans med mer forskning för högre temperaturapplikationer med särskild uppmärksamhet på mekanisk integritet.

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Yang, Chen. "Thermodynamic Cycles using Carbon Dioxide as Working Fluid : CO2 transcritical power cycle study." Doctoral thesis, KTH, Tillämpad termodynamik och kylteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-50261.

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The interest in utilizing the energy in low‐grade heat sources and waste heat is increasing. There is an abundance of such heat sources, but their utilization today is insufficient, mainly due to the limitations of the conventional power cycles in such applications, such as low efficiency, bulky size or moisture at the expansion outlet (e.g. problems for turbine blades). Carbon dioxide (CO2) has been widely investigated for use as a working fluid in refrigeration cycles, because it has no ozonedepleting potential (ODP) and low global warming potential (GWP). It is also inexpensive, non‐explosive, non‐flammable and abundant in nature. At the same time, CO2 has advantages in use as a working fluid in low‐grade heat resource recovery and energy conversion from waste heat, mainly because it can create a better matching to the heat source temperature profile in the supercritical region to reduce the irreversibility during the heating process. Nevertheless, the research in such applications is very limited. This study investigates the potential of using carbon dioxide as a working fluid in power cycles for low‐grade heat source/waste heat recovery. At the beginning of this study, basic CO2 power cycles, namely carbon dioxide transcritical power cycle, carbon dioxide Brayton cycle and carbon dioxide cooling and power combined cycle were simulated and studied to see their potential in different applications (e.g. low‐grade heat source applications, automobile applications and heat and power cogeneration applications). For the applications in automobile industries, low pressure drop on the engine’s exhaust gas side is crucial to not reducing the engine’s performance. Therefore, a heat exchanger with low‐pressure drop on the secondary side (i.e. the gas side) was also designed, simulated and tested with water and engine exhaust gases at the early stage of the study (Appendix 2). The study subsequently focused mainly on carbon dioxide transcritical power cycle, which has a wide range of applications. The performance of the carbon dioxide transcritical power cycle has been simulated and compared with the other most commonly employed power cycles in lowgrade heat source utilizations, i.e. the Organic Rankin Cycle (ORC). Furthermore, the annual performance of the carbon dioxide transcritical power cycle in utilizing the low‐grade heat source (i.e. solar) has also been simulated and analyzed with dynamic simulation in this work. Last but not least, the matching of the temperature profiles in the heat exchangers for CO2 and its influence on the cycle performance have also been discussed. Second law thermodynamic analyses of the carbon dioxide transcritical power systems have been completed. The simulation models have been mainly developed in the software known as Engineering Equation Solver (EES)1 for both cycle analyses and computer‐aided heat exchanger designs. The model has also been connected to TRNSYS for dynamic system annual performance simulations. In addition, Refprop 7.02 is used for calculating the working fluid properties, and the CFD tool (COMSOL) 3 has been employed to investigate the particular phenomena influencing the heat exchanger performance.
QC 20111205

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Schroder, Andrew U. "A Study of Power Cycles Using Supercritical Carbon Dioxide as the Working Fluid." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1461592844.

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Rieger, Mathias. "Advanced modeling and simulation of integrated gasification combined cycle power plants with CO2-capture." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-150522.

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The objective of this thesis is to provide an extensive description of the correlations in some of the most crucial sub-processes for hard coal fired IGCC with carbon capture (CC-IGCC). For this purpose, process simulation models are developed for four industrial gasification processes, the CO-shift cycle, the acid gas removal unit, the sulfur recovery process, the gas turbine, the water-/steam cycle and the air separation unit (ASU). Process simulations clarify the influence of certain boundary conditions on plant operation, performance and economics. Based on that, a comparative benchmark of CC-IGCC concepts is conducted. Furthermore, the influence of integration between the gas turbine and the ASU is analyzed in detail. The generated findings are used to develop an advanced plant configuration with improved economics. Nevertheless, IGCC power plants with carbon capture are not found to be an economically efficient power generation technology at present day boundary conditions.

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Chen, Huijuan. "The Conversion of Low-Grade Heat into Power Using Supercritical Rankine Cycles." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3447.

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Low-grade heat sources, here defined as below 300 ºC, are abundantly available as industrial waste heat, solar thermal, and geothermal, to name a few. However, they are under-exploited for conversion to power because of the low efficiency of conversion. The utilization of low-grade heat is advantageous for many reasons. Technologies that allow the efficient conversion of low-grade heat into mechanical or electrical power are very important to develop. This work investigates the potential of supercritical Rankine cycles in the conversion of low-grade heat into power. The performance of supercritical Rankine cycles is studied using ChemCAD linked with customized excel macros written in Visual Basic and programs written in C++. The selection of working fluids for a supercritical Rankine cycle is of key importance. A rigorous investigation into the potential working fluids is carried out, and more than 30 substances are screened out from all the available fluid candidates. Zeotropic mixtures are innovatively proposed to be used in supercritical Rankine cycles to improve the system efficiency. Supercritical Rankine cycles and organic Rankine cycles with pure working fluids as well as zeotropic mixtures are studied to optimize the conversion of lowgrade heat into power. The results show that it is theoretically possible to extract and convert more energy from such heat sources using the cycle developed in this research than the conventional organic Rankine cycles. A theory on the selection of appropriate working fluids for different heat source and heat sink profiles is developed to customize and maximize the thermodynamic cycle performance. The outcomes of this research will eventually contribute to the utilization of low-grade waste heat more efficiently.

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Vidhi, Rachana. "Organic Fluids and Passive Cooling in a Supercritical Rankine Cycle for Power Generation from Low Grade Heat Sources." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5322.

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Low grade heat sources have a large amount of thermal energy content. Due to low temperature, the conventional power generation technologies result in lower efficiency and hence cannot be used. In order to efficiently generate power, alternate methods need to be used. In this study, a supercritical organic Rankine cycle was used for heat source temperatures varying from 125°C to 200°C. Organic refrigerants with zero ozone depletion potential and their mixtures were selected as working fluid for this study while the cooling water temperature was changed from 10-25°C. Operating pressure of the cycle has been optimized for each fluid at every heat source temperature to obtain the highest thermal efficiency. Energy and exergy efficiencies of the thermodynamic cycle have been obtained as a function of heat source temperature. Efficiency of a thermodynamic cycle depends significantly on the sink temperature. At areas where water cooling is not available and ambient air temperature is high, efficient power generation from low grade heat sources may be a challenge. Use of passive cooling systems coupled with the condenser was studied, so that lower sink temperatures could be obtained. Underground tunnels, buried at a depth of few meters, were used as earth-air-heat-exchanger (EAHE) through which hot ambient air was passed. It was observed that the air temperature could be lowered by 5-10°C in the EAHE. Vertical pipes were used to lower the temperature of water by 5°C by passing it underground. Nocturnal cooling of stored water has been studied that can be used to cool the working fluid in the thermodynamic cycle. It was observed that the water temperature can be lowered by 10-20°C during the night when it is allowed to cool. The amount of water lost was calculated and was found to be approximately 0.1% over 10 days. The different passive cooling systems were studied separately and their effects on the efficiency of the thermodynamic cycle were investigated. They were then combined into a novel condenser design that uses passive cooling technology to cool the working fluid that was selected in the first part of the study. It was observed that the efficiency of the cycle improved by 2-2.5% when passive cooling system was used.

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Rezazadeh, Fatemeh. "Optimal integration of post-combustion CO2 capture process with natural gas fired combined cycle power plants." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/14349/.

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Post combustion CO2 capture (PCC) has been considered as one of the near term solutions to significantly reduce CO2 emissions associated with fossil fuels combustions. To accelerate the PCC incorporation into the energy market, various political, legal, economic and technical challenges and uncertainties should be successfully tackled. In relation to such, this thesis investigates methods to offer optimal incorporation of post-combustion CO2 capture process into natural gas fired combined cycle (NGCC) power plants. The objectives of this thesis is to develop and use thermodynamic models to study various process configurations, evaluate and quantify their benefits in terms of energy requirements on the performance of the integrated PCC-NGCC power plants. A detailed rate-based model of CO2 absorption/stripping process using 30 wt. % monoethanolamine (MEA) as solvent was developed in Aspen Plus® RateSepTM. The developed rate-based model was successfully validated in pilot scale using experimental data obtained from two pilot plants: (1) the UKCCSRC/PACT CO2 capture pilot plant, and (2) the pilot plant at the Laboratory of Engineering Thermodynamics in TU Kaiserslautern. The application and effectiveness of four alternative process configurations were studied: two absorber intercooling processes, i.e. “in-and-out” intercooling and “recycled intercooling”, and two stripper configurations: “advanced reboiled” stripper and “advanced flash” stripper. In addition, optimal incorporation of a large-scale PCC plant, including the CO2 compression unit, into a commercial-scale NGCC plant with a nominal power output of 650 MWe was investigated. The performance viability of the integrated NGCC-PCC plant was assessed at power plant full-load and part-load operations, to study the feasibility of the PCC operation at power plants full-load and part-loads, and recognise key performance parameters require careful consideration for a stable and efficient operation of the integrated plant at variable loads. In addition, the performance of the NGCC, especially the low pressure steam turbine, at various loads at times the power plant was integrated with the capture plant, and at times the CO2 capture plant was offline were investigated, and issues require careful considerations when operating the power plant in case of non-capture operation were addressed. This research also studied the relationship between the cost of CO2 capture and the flue gas CO2 concentration ranging from 4 to 14 %. For each case, the specific regeneration and cooling duties and total capital expenditure (CAPEX) and operational expenditures (OPEX) were calculated and compared. Accordingly, the total annual cost of each plant (TOTEX) was determined using the respective CAPEX and OPEX with taking into account an investment period of 20 years and an interest rate of 10 %. Finally, for each case the cost of CO2 captured was estimated and compared.

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Errey, Olivia Claire. "Variable capture levels of carbon dioxide from natural gas combined cycle power plant with integrated post-combustion capture in low carbon electricity markets." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33240.

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This work considers the value of flexible power provision from natural gas-fired combined cycle (NGCC) power plants operating post-combustion carbon dioxide (CO2) capture in low carbon electricity markets. Specifically, the work assesses the value of the flexibility gained by varying CO2 capture levels, thus the specific energy penalty of capture and the resultant power plant net electricity export. The potential value of this flexible operation is quantified under different electricity market scenarios, given the corresponding variations in electricity export and CO2 emissions. A quantified assessment of natural gas-fired power plant integrated with amine-based post-combustion capture and compression is attempted through the development of an Aspen Plus simulation. To enable evaluation of flexible operation, the simulation was developed with the facility to model off-design behaviour in the steam cycle, amine capture unit and CO2 compression train. The simulation is ultimately used to determine relationships between CO2 capture level and the total specific electricity output penalty (EOP) of capture for different plant configurations. Based on this relationship, a novel methodology for maximising net plant income by optimising the operating capture level is proposed and evaluated. This methodology provides an optimisation approach for power plant operators given electricity market stimuli, namely electricity prices, fuel prices, and carbon reduction incentives. The techno-economic implications of capture level optimisation are considered in three different low carbon electricity market case studies; 1) a CO2 price operating in parallel to wholesale electricity selling prices, 2) a proportional subsidy for low carbon electricity considered to be the fraction of plant electrical output equal to the capture level, and 3) a subsidy for low carbon electricity based upon a counterfactual for net plant CO2 emissions (similar to typical approaches for implementing an Emissions Performance Standard). The incentives for variable capture levels are assessed in each market study, with the value of optimum capture level operation quantified for both plant operators and to the wider electricity market. All market case studies indicate that variable capture is likely to increase plant revenue throughout the range of market prices considered. Different market approaches, however, lead to different valuation of flexible power provision and therefore different operating outcomes.

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Pham, Hong Son. "Investigation of the supercritical CO2 cycle : mapping of the thermodynamic potential for different applications; further understanding of the physical processes, in particular through simulations and analysis of experimental data." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4338.

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Cette thèse évalue d'abord le potentiel thermodynamique du cycle au CO2 supercritique (sc-CO2) pour une large gamme de température de source chaude et étudie son couplage aux applications nucléaires, 45.7% d’efficacité thermique étant obtenu pour un réacteur à neutrons rapides refroidi au sodium. Des simulations CFD sont réalisées sur un compresseur à échelle réduite et confrontées à une expérience, apportant des éléments de qualification. Des simulations sur un compresseur à échelle 1:1 révèlent des particularités liées à la compression du sc-CO2 au comportement gaz réel, offrant un retour d’expérience pour la conception. Dans ce cadre, une approche de cartes de performance est proposée et validée à l'aide de simulations. Enfin, une étude de la collapse d’une bulle dans le CO2 liquide au voisinage du point critique est réalisée et indique l'absence d’effet destructif de cavitation, ouvrant la voie au fonctionnement du compresseur en phase liquide, lieu optimum de l'efficacité du cycle
This study first evaluates the thermodynamic performance of the supercritical CO2 (sc-CO2) cycle in a large range of heat source temperature, with a focus on the nuclear applications; a thermal efficiency of 45.7% is reported for a Sodium-cooled Fast Reactor. Second, CFD simulations have been performed on a small scale sc-CO2 compressor and results have been confronted positively with the experimental data. Simulation results on a real scale compressor have then revealed some particularities during the compression of a real fluid, providing feedbacks for the component design. In addition, a reliable performance maps approach has been proposed for the sc-CO2 compressor and validated using the CFD results. Finally, an investigation of bubble collapse in the liquid CO2 near the critical point has disclosed the likely absence of detrimental effects. As such, risks of cavitation damage should be low, favoring the compressor operation in the liquid region for cycle efficiency improvement

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Toublanc, Cyril. "Amélioration du cycle trans-critique au CO2 par une compression refrodie : évaluations numérique et expérimentale." Phd thesis, Conservatoire national des arts et metiers - CNAM, 2009. http://tel.archives-ouvertes.fr/tel-00465986.

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Les émissions de gaz à effet de serre, du domaine du frid, sont à la fois d'origine directe et indirecte. Elles sont respectivement liées à la nature du fluide frigorigène et aux consommations énergétiques des systèmes. La recherche de nouvelles molécules de synthèse à faible potentiel de réchauffement global et l'emploi de fluides naturels dans des architectures de cycle adaptées constituent la base de ce travail. Concernant ce dernier point, la compression isotherme pallie efficacement les propriétés thermodynamiques du CO2, qui sont peu favorables aux systèmes à compression de vapeur. Cette transformation idéale permet l'obtention d'un COP équivalent à 92% du COPcarnot. L'injection d'huile dans la chambre de compression, sous la forme de fines gouttelettes, a été envisagée pour se rapprocher de cette compression isotherme. Son potentiel a tout d'abord été évalué par simulation numérique pour des copresseurs scroll et piston. Il est apparu qu'une taille de goutte de 0,025mm et un débit 3 fois plus important que celui de CO2, conduisent à un gain énergétique substentiel: +30% par rapport au cycle trans-critique conventionnel. La faisabilité d'obtention d'un spray, constitué de gouttelettes d'un diamètre moyen de 0,05 mm, a fait l'objet d'une première validation expérimentale. Cette solution qui peut être combinée avec d'autres innovations technologiques pourrait permettre d'avoir des équipements frigorifiques, au CO2 ayant un impact environnemental inférieur à celui des systèmes utilisant des fluides de synthèse.

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Herraiz, Palomino Laura. "Selective exhaust gas recirculation in combined cycle gas turbine power plants with post-combustion carbon capture." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/23460.

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Selective Exhaust Gas Recirculation (S-EGR) consists of selectively transferring CO2 from the exhaust gas stream of a gas-fired power plant into the air stream entering the gas turbine compressor. Unlike in “non-selective” Exhaust Gas Recirculation (EGR) technology, recirculation of, principally, nitrogen does not occur, and the gas turbine still operates with a large excess of air. Two configurations are proposed: one with the CO2 transfer system operating in parallel to the post-combustion carbon capture (PCC) unit; the other with the CO2 transfer system operating downstream of, and in series to, the PCC unit. S-EGR allows for higher CO2 concentrations in the flue gas of approximately 13-14 vol%, compared to 6.6 vol% with EGR at 35% recirculation ratio. The oxygen levels in the combustor are approximately 19 vol%, well above the minimum limit of 16 vol% with 35% EGR reported in literature. At these operating conditions, process model simulations show that the current class of gas turbine engines can operate without a significant deviation in the compressor and the turbine performance from the design conditions. Compressor inlet temperature and CO2 concentration in the working fluid are critical parameters in the assessment of the effect on the gas turbine net power output and efficiency. A higher turbine exhaust temperature allows the generation of additional steam which results in a marginal increase in the combined cycle net power output of 5% and 2% in the investigated configurations with S-EGR in parallel and S-EGR in series, respectively. With aqueous monoethanolamine scrubbing technology, S-EGR leads to operation and cost benefits. S-EGR in parallel operating at 70% recirculation, 97% selective CO2 transfer efficiency and 96% PCC efficiency results in a reduction of 46% in packing volume and 5% in specific reboiler duty, compared to air-based combustion CCGT with PCC, and of 10% in packing volume and 2% in specific reboiler duty, compared to 35% EGR. S-EGR in series operating at 95% selective CO2 transfer efficiency and 32% PCC efficiency results in a reduction of 64% in packing volume and 7% in specific reboiler duty, compared to air-based, and of 40% in packing volume and 4% in specific reboiler duty, compared to 35% EGR. An analysis of key performance indicators for selective CO2 transfer proposes physical adsorption in rotary wheel systems as an alternative to selective CO2 membrane systems. A conceptual design assessment with two commercially available adsorbent materials, activated carbon and Zeolite X13, shows that it is possible to regenerate the adsorbent with air at near ambient temperature and pressure. Yet, a significant step change in adsorbent materials is necessary to design rotary adsorption systems with dimensions comparable to the largest rotary gas/gas heat exchanger used in coal-fired power plants, i.e. approximately 24 m diameter and 2 m height. An optimisation study provides guidelines on the equilibrium parameters for the development of materials. Finally, a technical feasibility study of configuration options with rotary gas/gas heat exchangers shows that cooling water demand around the post-combustion CO2 capture system can be drastically reduced using dry cooling systems where gas/gas heat exchangers use ambient air as the cooling fluid. Hybrid cooling configurations reduce cooling and process water demand in the direct contact cooler of a wet cooling system by 67% and 35% respectively, and dry cooling configurations eliminate the use of process and cooling water and achieve adequate gas temperature entering the absorber.

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Tkachuk, Andriy. "Smíšený tepelný cyklus." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229753.

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This master thesis follows the bachelor thesis with the same name. It is looks into the analyses of the combi-cycle, the advantage of which is high efficiency and easy separation of CO2 for its storage and further usage. It introduces the Graz cycle, its thermal balance a basic arrangement. The calculation is attached in a separate .XLS file. At the end of the thesis, the result of the calculation is interpreted and the conditions under which the project would be realized are outlined.

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Ma, Yuegeng [Verfasser], Tatiana [Akademischer Betreuer] Morozyuk, Tatiana [Gutachter] Morozyuk, and Sergio [Gutachter] Mussati. "Optimal design of supercritical carbon dioxide cycle based system for concentrated solar power application / Yuegeng Ma ; Gutachter: Tatiana Morozyuk, Sergio Mussati ; Betreuer: Tatiana Morozyuk." Berlin : Technische Universität Berlin, 2020. http://d-nb.info/1205804978/34.

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20

Alie, Colin. "CO₂ Capture With MEA: Integrating the Absorption Process and Steam Cycle of an Existing Coal-Fired Power Plant." Thesis, University of Waterloo, 2004. http://hdl.handle.net/10012/796.

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In Canada, coal-fired power plants are the largest anthropogenic point sources of atmospheric CO₂. The most promising near-term strategy for mitigating CO₂ emissions from these facilities is the post-combustion capture of CO₂ using MEA (monoethanolamine) with subsequent geologic sequestration. While MEA absorption of CO₂ from coal-derived flue gases on the scale proposed above is technologically feasible, MEA absorption is an energy intensive process and especially requires large quantities of low-pressure steam. It is the magnitude of the cost of providing this supplemental energy that is currently inhibiting the deployment of CO₂ capture with MEA absorption as means of combatting global warming. The steam cycle of a power plant ejects large quantities of low-quality heat to the surroundings. Traditionally, this waste has had no economic value. However, at different times and in different places, it has been recognized that the diversion of lower quality streams could be beneficial, for example, as an energy carrier for district heating systems. In a similar vein, using the waste heat from the power plant steam cycle to satisfy the heat requirements of a proposed CO₂ capture plant would reduce the required outlay for supplemental utilities; the economic barrier to MEA absorption could be removed. In this thesis, state-of-the-art process simulation tools are used to model coal combustion, steam cycle, and MEA absorption processes. These disparate models are then combined to create a model of a coal-fired power plant with integrated CO₂ capture. A sensitivity analysis on the integrated model is performed to ascertain the process variables which most strongly influence the CO₂ energy penalty. From the simulation results with this integrated model, it is clear that there is a substantial thermodynamic advantage to diverting low-pressure steam from the steam cycle for use in the CO₂ capture plant. During the course of the investigation, methodologies for using Aspen Plus® to predict column pressure profiles and for converging the MEA absorption process flowsheet were developed and are herein presented.

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21

Al-Anfaji, Ahmed Suaal Bashar. "The optimization of combined power-power generation cycles." Thesis, University of Hertfordshire, 2015. http://hdl.handle.net/2299/15485.

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An investigation into the performance of several combined gas-steam power generating plants’ cycles was undertaken at the School of Engineering and Technology at the University of Hertfordshire and it is predominantly analytical in nature. The investigation covered in principle the aspect of the fundamentals and the performance parameters of the following cycles: gas turbine, steam turbine, ammonia-water, partial oxidation and the absorption chiller. Complete thermal analysis of the individual cycles was undertaken initially. Subsequently, these were linked to generate a comprehensive computer model which was employed to predict the performance and characteristics of the optimized combination. The developed model was run using various input parameters to test the performance of the cycle’s combination with respect to the combined cycle’s efficiency, power output, specific fuel consumption and the temperature of the stack gases. In addition, the impact of the optimized cycles on the generation of CO2 and NOX was also investigated. This research goes over the thermal power stations of which most of the world electrical energy is currently generated by. Through which, to meet the increase in the electricity consumption and the environmental pollution associated with its production as well as the limitation of the natural hydrocarbon resources necessitated. By making use of the progressive increase of high temperature gases in recent decades, the advent of high temperature material and the use of large compression ratios and generating electricity from high temperature of gas turbine discharge, which is otherwise lost to the environment, a better electrical power is generated by such plant, which depends on a variety of influencing factors. This thesis deals with an investigation undertaken to optimize the performance of the combined Brayton-Rankine power cycles' performance. This work includes a comprehensive review of the previous work reported in the literature on the combined cycles is presented. An evaluation of the performance of combined cycle power plant and its enhancements is detailed to provide: A full understanding of the operational behaviour of the combined power plants, and demonstration of the relevance between power generations and environmental impact. A basic analytical model was constructed for the combined gas (Brayton) and the steam (Rankine) and used in a parametric study to reveal the optimization parameters, and its results were discussed. The role of the parameters of each cycle on the overall performance of the combined power cycle is revealed by assessing the effect of the operating parameters in each individual cycle on the performance of the CCPP. P impacts on the environment were assessed through changes in the fuel consumption and the temperature of stack gases. A comprehensive and detailed analytical model was created for the operation of hypothetical combined cycle power and power plant. Details of the operation of each component in the cycle was modelled and integrated in the overall all combined cycle/plant operation. The cycle/plant simulation and matching as well as the modelling results and their analysis were presented. Two advanced configurations of gas turbine cycle for the combined cycle power plants are selected, investigated, modelled and optimized as a part of combined cycle power plant. Both configurations work on fuel rich combustion, therefore, the combustor model for rich fuel atmosphere was established. Additionally, models were created for the other components of the turbine which work on the same gases. Another model was created for the components of two configurations of ammonia water mixture (kalina) cycle. As integrated to the combined cycle power plant, the optimization strategy considered for these configurations is for them to be powered by the exhaust gases from either the gas turbine or the gases leaving the Rankine boiler (HRSG). This included ChGT regarding its performance and its environmental characteristics. The previously considered combined configuration is integrated by as single and double effect configurations of an ammonia water absorption cooling system (AWACS) for compressor inlet air cooling. Both were investigated and designed for optimizing the triple combination power cycle described above. During this research, tens of functions were constructed using VBA to look up tables linked to either estimating fluids' thermodynamic properties, or to determine a number of parameters regarding the performance of several components. New and very interesting results were obtained, which show the impact of the input parameters of the individual cycles on the performance parameters of a certain combined plant’s cycle. The optimized parameters are of a great practical influence on the application and running condition of the real combined plants. Such influence manifested itself in higher rate of heat recovery, higher combined plant thermal efficiency from those of the individual plants, less harmful emission, better fuel economy and higher power output. Lastly, it could be claimed that various concluding remarks drawn from the current study could help to improve the understanding of the behaviour of the combined cycle and help power plant designers to reduce the time, effort and cost of prototyping.

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22

Gay, Swann. "Elaboration de matrices microcellulaires de polymère biosourcé par la technologie CO², supercritique." Thesis, Angers, 2017. http://www.theses.fr/2017ANGE0007.

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Dans le contexte actuel, où la préservation des ressources et le développement durable sont devenus des enjeux importants de ce siècle, la production de matériaux tant performants que respectueux de l’environnement est devenue indispensable. Ainsi, ce travail de thèse porte sur l’élaboration de matrices poreuses de biopolymères en utilisant la technologie CO2 supercritique (CO2-SC). L’utilisation du PLA permet de produire des matrices 100% biosourcées et biodégradables, alors que l’utilisation de CO2-SC permet de diminuer l’impact écologique des procédés de mise en forme. Dans un premier temps une étude paramétrique de la mise en forme de matrice de PLA par une méthode de séparation de phase thermique (TIPS) couplée à un séchage par CO2 a été réalisée. Elle a permis de produire des matrices microcellulaires de faible densité (entre 60 et 320 kg/m3) et aux propriétés structurales mécaniques modulables. L’ensemble du procédé a fait l’objet d’une analyse de cycle de vie et il a été démontré que l’utilisation du CO2-SC en remplacement de la lyophilisation a réduit d’entre 50 et 90% l’impact environnemental. Dans un second temps une étude in-situ de la séparation de phase par tomographie-X en rayonnement synchrotron a permis de mieux comprendre la mécanistique de notre procédé. Enfin, la dernière partie de ce travail a été consacré à la mise en forme de matrice de PLA sans solvant, en utilisant le CO2-SC comme agent gonflant. Les résultats obtenus ont servi à réaliser une étude comparative des deux procédés développés
In the present context, where the preservation of resources and sustainable development became the main issues of this century, the production of more efficient and environmentally friendly materials is essential. Thus, this work deals with thedevelopment of biobased polymeric porous matrix using SC-CO2. The use of PLA makes it possible to produce 100% biosourced and biodegradable matrices, while the use of CO2-SC reduces the ecological impact of the shaping processes. In a first step, a parametric study of PLA matrix shaping by a thermal induced phase separation (TIPS) method coupled to CO2 drying was performed. Low density microcellular matrices were obtained with tunable structural and mechanical properties. The whole process was analyze by life cycle assessment and the results showed that SC-CO2 replacing freeze drying has reduced the environmental impact between 50 and 90%. Secondly, a phase separation in situ study by tomography-X synchrotron radiation tomography allowed us to better understand the mechanics of our process. Finally, the last part of this work was devoted to the implementation of a solvent free process, using SC-CO2 as a blowing agent. The results obtained were used to carry out a comparative study of the two processes developed

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Rieger, Mathias [Verfasser], Bernd [Akademischer Betreuer] Meyer, Bernd [Gutachter] Meyer, and Michael [Gutachter] Beckmann. "Advanced modeling and simulation of integrated gasification combined cycle power plants with CO2-capture / Mathias Rieger ; Gutachter: Bernd Meyer, Michael Beckmann ; Betreuer: Bernd Meyer." Freiberg : Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://d-nb.info/1220911925/34.

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24

He, Junjing. "High temperature performance of materials for future power plants." Doctoral thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-191547.

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Increasing energy demand leads to two crucial problems for the whole society. One is the economic cost and the other is the pollution of the environment, especially CO2 emissions. Despite efforts to adopt renewable energy sources, fossil fuels will continue to dominate. The temperature and stress are planned to be raised to 700 °C and 35 MPa respectively in the advanced ultra-supercritical (AUSC) power plants to improve the operating efficiency. However, the life of the components is limited by the properties of the materials. The aim of this thesis is to investigate the high temperature properties of materials used for future power plants. This thesis contains two parts. The first part is about developing creep rupture models for austenitic stainless steels. Grain boundary sliding (GBS) models have been proposed that can predict experimental results. Creep cavities are assumed to be generated at intersection of subboundaries with subboundary corners or particles on a sliding grain boundary, the so called double ledge model. For the first time a quantitative prediction of cavity nucleation for different types of commercial austenitic stainless steels has been made. For growth of creep cavities a new model for the interaction between the shape change of cavities and creep deformation has been proposed. In this constrained growth model, the affected zone around the cavities has been calculated with the help of FEM simulation. The new growth model can reproduce experimental cavity growth behavior quantitatively for different kinds of austenitic stainless steels. Based on the cavity nucleation models and the new growth models, the brittle creep rupture of austenitic stainless steels has been determined. By combing the brittle creep rupture with the ductile creep rupture models, the creep rupture strength of austenitic stainless steels has been predicted quantitatively. The accuracy of the creep rupture prediction can be improved significantly with combination of the two models. The second part of the thesis is on the fatigue properties of austenitic stainless steels and nickel based superalloys. Firstly, creep, low cycle fatigue (LCF) and creep-fatigue tests have been conducted for a modified HR3C (25Cr20NiNbN) austenitic stainless steel. The modified HR3C shows good LCF properties, but lower creep and creep-fatigue properties which may due to the low ductility of the material. Secondly, LCF properties of a nickel based superalloy Haynes 282 have been studied. Tests have been performed for a large ingot. The LCF properties of the core and rim positions did not show evident differences. Better LCF properties were observed when compared with two other low γ’ volume fraction nickel based superalloys. Metallography study results demonstrated that the failure mode of the material was transgranular. Both the initiation and growth of the fatigue cracks were transgranular.

QC 20160905

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25

Kotze, Johannes Paulus. "Thermal energy storage in metallic phase change materials." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/96049.

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Thesis (PhD) -- Stellenbosch University, 2014.
ENGLISH ABSTRACT: Currently the reduction of the levelised cost of electricity (LCOE) is the main goal of concentrating solar power (CSP) research. Central to a cost reduction strategy proposed by the American Department of Energy is the use of advanced power cycles like supercritical steam Rankine cycles to increase the efficiency of the CSP plant. A supercritical steam cycle requires source temperatures in excess of 620°C, which is above the maximum storage temperature of the current two-tank molten nitrate salt storage, which stores thermal energy at 565°C. Metallic phase change materials (PCM) can store thermal energy at higher temperatures, and do not have the drawbacks of salt based PCMs. A thermal energy storage (TES) concept is developed that uses both metallic PCMs and liquid metal heat transfer fluids (HTF). The concept was proposed in two iterations, one where steam is generated directly from the PCM – direct steam generation (DSG), and another where a separate liquid metal/water heat exchanger is used – indirect steam generation, (ISG). Eutectic aluminium-silicon alloy (AlSi12) was selected as the ideal metallic PCM for research, and eutectic sodium-potassium alloy (NaK) as the most suitable heat transfer fluid. Thermal energy storage in PCMs results in moving boundary heat transfer problems, which has design implications. The heat transfer analysis of the heat transfer surfaces is significantly simplified if quasi-steady state heat transfer analysis can be assumed, and this is true if the Stefan condition is met. To validate the simplifying assumptions and to prove the concept, a prototype heat storage unit was built. During testing, it was shown that the simplifying assumptions are valid, and that the prototype worked, validating the concept. Unfortunately unexpected corrosion issues limited the experimental work, but highlighted an important aspect of metallic PCM TES. Liquid aluminium based alloys are highly corrosive to most materials and this is a topic for future investigation. To demonstrate the practicality of the concept and to come to terms with the control strategy of both proposed concepts, a storage unit was designed for a 100 MW power plant with 15 hours of thermal storage. Only AlSi12 was used in the design, limiting the power cycle to a subcritical power block. This demonstrated some practicalities about the concept and shed some light on control issues regarding the DSG concept. A techno-economic evaluation of metallic PCM storage concluded that metallic PCMs can be used in conjunction with liquid metal heat transfer fluids to achieve high temperature storage and it should be economically viable if the corrosion issues of aluminium alloys can be resolved. The use of advanced power cycles, metallic PCM storage and liquid metal heat transfer is only merited if significant reduction in LCOE in the whole plant is achieved and only forms part of the solution. Cascading of multiple PCMs across a range of temperatures is required to minimize entropy generation. Two-tank molten salt storage can also be used in conjunction with cascaded metallic PCM storage to minimize cost, but this also needs further investigation.
AFRIKAANSE OPSOMMING: Tans is die minimering van die gemiddelde leeftydkoste van elektrisiteit (GLVE) die hoofdoel van gekonsentreerde son-energie navorsing. In die kosteverminderingsplan wat voorgestel is deur die Amerikaanse Departement van Energie, word die gebruik van gevorderde kragsiklusse aanbeveel. 'n Superkritiese stoom-siklus vereis bron temperature hoër as 620 °C, wat bo die 565 °C maksimum stoor temperatuur van die huidige twee-tenk gesmelte nitraatsout termiese energiestoor (TES) is. Metaal fase veranderingsmateriale (FVMe) kan termiese energie stoor by hoër temperature, en het nie die nadele van soutgebaseerde FVMe nie. ŉ TES konsep word ontwikkel wat gebruik maak van metaal FVM en vloeibare metaal warmteoordrag vloeistof. Die konsep is voorgestel in twee iterasies; een waar stoom direk gegenereer word uit die FVM (direkte stoomopwekking (DSO)), en 'n ander waar 'n afsonderlike vloeibare metaal/water warmteruiler gebruik word (indirekte stoomopwekking (ISO)). Eutektiese aluminium-silikon allooi (AlSi12) is gekies as die mees geskikte metaal FVM vir navorsingsdoeleindes, en eutektiese natrium – kalium allooi (NaK) as die mees geskikte warmteoordrag vloeistof. Termiese energie stoor in FVMe lei tot bewegende grens warmteoordrag berekeninge, wat ontwerps-implikasies het. Die warmteoordrag ontleding van die warmteruilers word aansienlik vereenvoudig indien kwasi-bestendige toestand warmteoordrag ontledings gebruik kan word en dit is geldig indien daar aan die Stefan toestand voldoen word. Om vereenvoudigende aannames te bevestig en om die konsep te bewys is 'n prototipe warmte stoor eenheid gebou. Gedurende toetse is daar bewys dat die vereenvoudigende aannames geldig is, dat die prototipe werk en dien as ŉ bevestiging van die konsep. Ongelukkig het onverwagte korrosie die eksperimentele werk kortgeknip, maar dit het klem op 'n belangrike aspek van metaal FVM TES geplaas. Vloeibare aluminium allooie is hoogs korrosief en dit is 'n onderwerp vir toekomstige navorsing. Om die praktiese uitvoerbaarheid van die konsep te demonstreer en om die beheerstrategie van beide voorgestelde konsepte te bevestig is 'n stoor-eenheid ontwerp vir 'n 100 MW kragstasie met 15 uur van 'n TES. Slegs AlSi12 is gebruik in die ontwerp, wat die kragsiklus beperk het tot 'n subkritiese stoomsiklus. Dit het praktiese aspekte van die konsep onderteken, en beheerkwessies rakende die DSO konsep in die kollig geplaas. In 'n tegno-ekonomiese analise van metaal FVM TES word die gevolgtrekking gemaak dat metaal FVMe gebruik kan word in samewerking met 'n vloeibare metaal warmteoordrag vloeistof om hoë temperatuur stoor moontlik te maak en dat dit ekonomies lewensvatbaar is indien die korrosie kwessies van aluminium allooi opgelos kan word. Die gebruik van gevorderde kragsiklusse, metaal FVM stoor en vloeibare metaal warmteoordrag word net geregverdig indien beduidende vermindering in GLVE van die hele kragsentrale bereik is, en dit vorm slegs 'n deel van die oplossing. ŉ Kaskade van verskeie FVMe oor 'n reeks van temperature word vereis om entropie generasie te minimeer. Twee-tenk gesmelte soutstoor kan ook gebruik word in samewerking met kaskade metaal FVM stoor om koste te verminder, maar dit moet ook verder ondersoek word.

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Long, Henry A. III. "Development and Thermodynamic Analysis of an Integrated Mild/Partial Gasification Combined Cycle (IMPGC) Under Green and Brown Field Conditions With and Without Carbon Capture." ScholarWorks@UNO, 2018. https://scholarworks.uno.edu/td/2538.

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Coal is a very prominent energy source in the world, but it is environmentally unattractive due to its high sulfur and ash content as well as its alleged contribution towards climate change, but it is affordable, abundant, and has high energy content. Thus, utilizing coal in a cleaner and more efficient way has become necessary. One promising clean coal technology involves fully gasifying coal into synthesis gas, cleaning it, and feeding it into a high-efficiency combined cycle, such as an Integrated Gasification Combined Cycle (IGCC). Inspired by the recent success of warn gas cleanup (WGCU), mild and partial gasification are proposed as less energy intensive options. This Integrated Mild/Partial Gasification Combined Cycle (IMPGC) could significantly save energy and improve efficiency. The objective of this study is to investigate the capabilities of IMPGC as both a new plant and a retrofit option for traditional coal power plants with and without carbon capture. I MPGC relies on the principles of mild and partial gasification and the recently available WGGU technology with the following benefits: a.) completely negate the need for syngas cooling; b.) significantly reduce the energy needed to fully thermally crack the volatiles and completely gasify the char as in the IGCC system; c.) preserve the high chemical energy hydro-carbon bonds within the feedstock to allow more efficient combustion in the gas turbine; d.) reduce the size of gasifier and piping to reduce the costs; and e.) enable retrofitting of an old coal power plant by preserving the existing equipment. The software used (Thermoflex®) was first validated with established cases from the U.S. Department of Energy. For new plants, the results show that IMPGC’s efficiency is 8 percentage points (20%) higher than IGCC, 8 points higher than a modern subcritical Rankine cycle, and 3-4 points higher than an ultra-supercritical (USC) cycle. When retrofitting older plants, a minimum improvement of over 4 points is predicted. When carbon capture is involved, IMPGC’s efficiency becomes 10 points better than a subcritical plant and 8 points better than a USC plant. Emissions wise, IMPGC is better than IGCC and much better than Rankine cycle plants.

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Alkadee, Dareen. "Techniques de réduction et de traitement des émissions polluantes dans une machine thermique." Phd thesis, Conservatoire national des arts et metiers - CNAM, 2011. http://tel.archives-ouvertes.fr/tel-01005123.

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Cette thèse de doctorat, a consisté, dans une première partie, à introduire d'une part, la notion de l'analyse du cycle de vie " ACV " et celle des biocarburants. D'autre part, à présenter l'intérêt d'appliquer une ACV sur des biocarburants afin de valoriser leurs bilans énergétiques et analyser leurs impacts environnementaux face aux carburants conventionnels. Dans une deuxième partie, nous avons comparé, d'un point de vue énergétique et environnemental, 3 scénarios de production d'électricité : 2 scénarios de cogénération (turbine à vapeur et ORC) pour la production d'énergie électrique et thermique à partir de biomasse, et un scénario de cogénération par moteur diesel. Ces scénarios sont comparés à l'aide de deux méthodes orientées " analyse des dommages ": Eco-indicateur 99 (E) et IMPACT2002+Dans une troisième partie, on a abordé la valorisation du biogaz sous forme de carburant dans des moteurs "dual fuel" pour des engins agricoles dans le but de déterminer l'impact environnemental lié à l'utilisation de ce carburant alternatif au diesel par rapport aux autres biocarburants. Les méthodes Eco-indicateur 99 (E) et CML ont été utilisées ici. On a pu ainsi identifier les principaux polluants générés à chaque étape du cycle de vie de l'agrocarburant et les étapes qui ont les plus grands impacts environnementaux et on a identifié, selon nos critères et par rapport au contexte, le scénario énergétique le plus compatible avec le principe de développement durable.

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El, Gemayel Gemayel. "Integration and Simulation of a Bitumen Upgrading Facility and an IGCC Process with Carbon Capture." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23274.

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Hydrocracking and hydrotreating are bitumen upgrading technologies designed to enhance fuel quality by decreasing its density, viscosity, boiling point and heteroatom content via hydrogen addition. The aim of this thesis is to model and simulate an upgrading and integrated gasification combined cycle then to evaluate the feasibility of integrating slurry hydrocracking, trickle-bed hydrotreating and residue gasification using the Aspen HYSYS® simulation software. The close-coupling of the bitumen upgrading facilities with gasification should lead to a hydrogen, steam and power self-sufficient upgrading facility with CO2 capture. Hydrocracker residue is first withdrawn from a 100,000 BPD Athabasca bitumen upgrading facility, characterized via ultimate analysis and then fed to a gasification unit where it produces hydrogen that is partially recycled to the hydrocracker and hydrotreaters and partially burned for power production in a high hydrogen combined cycle unit. The integrated design is simulated for a base case of 90% carbon capture utilizing a monoethanolamine (MEA) solvent, and compared to 65% and no carbon capture scenarios. The hydrogen production of the gasification process is evaluated in terms of hydrocracker residue and auxiliary petroleum coke feeds. The power production is determined for various carbon capture cases and for an optimal hydrocracking operation. Hence, the feasibility of the integration of the upgrading process and the IGCC resides in meeting the hydrogen demand of the upgrading facility while producing enough steam and electricity for a power and energy self-sufficient operation, regardless of the extent of carbon capture.

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29

Khivsara, Sagar D. "A Design Concept of a Volumetric Solar Receiver for Supercritical CO2 Brayton Cycle." Thesis, 2014. http://hdl.handle.net/2005/2996.

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Recently, the supercritical carbon dioxide (s-CO2) Brayton cycle has been identified as a promising candidate for solar-thermal energy conversion due to its potentially high thermal efficiency (50%, for turbine inlet temperatures of ~ 1000 K). Realization of such a system requires development of solar receivers which can raise the temperature of s-CO2 by over 200 K, to a receiver outlet temperature of 1000 K. Volumetric receivers are an attractive alternative to tubular receivers due to their geometry, functionality and reduced thermal losses. A concept of a ceramic pressurized volumetric receiver for s-CO2 has been developed in this work. Computational Fluid Dynamics (CFD) analysis along with a Discrete Ordinate method (DOM) radiation heat transfer model has been carried out, and the results for temperature distribution in the receiver and the resulting thermal efficiency are presented. Issues regarding material selection for the absorber structure, window, coating, receiver body and insulation are also addressed. A modular small scale prototype with 0.5 kWth solar heat input has been designed. The design of a small scale s-CO2 loop for testing this receiver module is also presented in this work. There is a lot of ongoing investigation for design and simulation of different configurations of heat exchangers and solar receivers using s-CO2 as the working fluid, in which wall temperatures up to 1000 K are encountered. While CO2 is considered to be transparent as far as solar radiation spectrum is concerned, there may be considerable absorption of radiation in the longer wavelength range associated with radiation emission from the heated cavity walls and tubes inside the receivers. An attempt has been made, in this study, to include radiation modelling to capture the effect of absorption bands of s-CO2 and the radiative heat transfer among the equipment surfaces. As a case study, a numerical study has been performed to evaluate the contribution of radiative heat transfer as compared to convection and conduction, for s-CO2 flow through a circular pipe. The intent is to provide a guideline for future research to determine the conditions for which radiation heat transfer modelling inside the pipe can be significant, and what errors can be expected otherwise. The effect of parameters such as Reynolds number, pipe diameter, length to diameter ratio, wall emissivity and total wall heat flux has been studied. The effect of radiation modelling on wall temperatures attained for certain amount of heat flux to be transferred to s-CO2 is also studied. The resulting temperature distribution, in turn, affects the estimation of heat loss to the environment

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CHIOU, FENG REN, and 邱豐壬. "Supercritical CO2 Brayton Cycle Turbine Blade Analysis." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/45712932760899143164.

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碩士
國立清華大學
動力機械工程學系
103
As the fossil fuel consumption is increasing, the energy shortage has gradually become a big problem nowadays. However, the industrial energy utilization is less than 50%, which means almost half of the precious energy is discharged into the air as waste heat or other forms that cannot be further used. The environment is deteriorating, so people are more concerned about the waste heat recovery and the uses of renewable energies (such as geothermal energy). Our laboratory has focused on researches about waste heat recovery system for plants for many years. From subcritical cycle systems (Organic Rankine Cycle, ORC) to supercritical cycle systems (Supercritical CO2 Brayton Cycle), the latter is our main research at present. The reasons for choosing CO2 as working fluid are because of its stability, low critical point conditions, wide range of applications and greenhouse gas reduction. The Turbine-Alternator-Compressor (TAC) component is a very important part in supercritical Brayton cycle system, especially the designs of rotors in compressor and expander, which are extremely difficult. The radial type of rotor is used both in compressor and turbine, and to reduce difficulties, I used the rotor of P-15 jet engine as basic model, but its blade shape still need to be modified corresponding to design points. Then CFD simulation is applied to improve rotor efficiency by repeatedly correct errors. At last, semi-closed system is used to reduce the difficulties of initial test and also for the safety issues.

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Lin, Bo Hung, and 林柏宏. "Supercritical CO2 Brayton Cycle Turbine Blade Analysis." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/88439005217672493410.

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碩士
國立清華大學
動力機械工程學系
104
There is a lot of electricity power used for production by industry. degree of electricity produced would consume a pound of coal and release lots of CO2 and wasted heat which cause the global warming、air pollution、acid rain、ozone hole etc. It’s necessary to find the substitute and recycle energy. For recycle energy, many researches changed the direction to supercritical cycle recently. According to the report from Sandia, the America National lab, supercritical Brayton cycle’s heat efficiency can be over 50% which is about 1.25~1.5 times compare to the traditional Rankine cycle. The reason choosing CO2 as working fluid is based on its stability , low critical point condition, wide range of applications and greenhouse gas reduction in the atmosphere. However the compressor and turbine of the system need to be designed precisely. To meet the work conditions of supercritical system, we choose the radial rotor as interior component. Utilize the design procedure built with ANSYS software by the lab graduated student Mr. Chiu to redesign a rotor which could take the high temperature and high pressure (12~18MPa、500~700K) design point. First using the software Aspen Plus to simulate the cycle stations and analyze the workout and efficiency. The design point of the rotor is 1kg/s of mass flowrate and 30000RPM of the rotor velocity to make 14MPa working fluid decrease to about 8MPa and keep the rotor efficiency over 75%. After the theory analysis and design procedure there are two rotor models derived. Although the pressure drop conforms to the design point but the inducer’s effect doesn’t answer to the anticipation and also influence the rotor efficiency to be only 60%. The flaw will be corrected to improve the rotor efficiency and meet the design point.

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32

Liu, Kai-Wen, and 劉凱文. "Supercritical CO2 Brayton Cycle Compressor Blade Design and Analysis." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ma3872.

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碩士
國立清華大學
動力機械工程學系
105
Accompanied by the prosperity of technology, the electricity needed for production is increasing year to year. However, the overall efficiency is not above 50%, and thus it will produce large amount of carbon dioxide and waste heat. It will give rise to the global warming aggravation and the air pollution, sour rain, ozonosphere holes and the destruction of forest…etc. So this paper intend to find an solution to finding alternative energy and recovery of waste heat, with the increasing literatures focusing on the super critical cycle in the energy recovery field. This paper put aim on the super critical Brayton cycle to make the first compressor design. According to the Sandia Laboratory’ reports, the overall efficiency of the combined cycle can be high above 50%. The reason to use carbon dioxide to be the working fluid is due to its stability, low critical condition, large range of application and capable of reducing the global warming. This paper design the prototype of the blades and rotors of the compressor. And then, by using ANSYS this paper propose a layout of the rotor and blade which can bear high temperature and pressure(7.8~15 MPa, 300~500K). And this model has been verified by comparing the simulation results with the paper [35]. The results are quite similar where the errors are below 6%. The efficiency of the impeller is about 50.1%, compared with the 25% efficiency of the impeller by using Air Ideal Gas as working fluid. It has been proven that the SCO2 compressor impeller is the best choice over the conventional Rankine cycle and the Brayton cycle by Air Ideal Gas. With the advantages of high rotating speed and the low volume, the pressure ratio of this compressor is about 1.85; the efficiency is about 50%.

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Wen, Meng-Yang, and 溫孟揚. "Design, Analysis, and Simulation of a Turbine for Supercritical CO2 Brayton Cycle." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/x4838c.

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碩士
國立清華大學
動力機械工程學系
105
The research of Supercritical CO2 (sCO2) Brayton Cycle has been popular over the past decade, due to its higher efficiency and smaller component size compared with those of steam Rankine cycle and air Brayton Cycle. Studies showed that SCO2 Brayton Cycle can accommodate a wide range of temperature as the heat source, starting from 260°C to 1200 °C. Thus, various research had been investigated to apply sCO2 Brayton Cycle into fields such as concentrated solar power, nuclear power, geothermal power, and waste heat recovery, making it a viable option for renewable energy. This study is a subproject of SCO2 Brayton Cycle power generation system, a project under the National Energy Program-Phase II in Taiwan, with the objective of designing a power generation system using waste heat as heat source. The temperature of the waste heat is set to be 450°C, conforming to mid-range waste heat. The aim of this subproject is to design a turbine with the inlet total pressure of 14.1 MPa and total temperature of 573K, respectively, and outlet pressure of 8.5 MPa, corresponding to an expansion ratio of 1.658. Due to its small size and low mass flow rate, radial inflow turbine is selected instead of the axial flow turbine. Some efforts were made by previous member of this lab to modify the existing turbine model to avoid the complexity of designing a turbine model from scratch. The efficiency, however, turned out to be lower the expectation. Therefore, in this study, the previously modified turbine model would be discarded and the new turbine would be built from square one. This study tried to use Meanline Analysis from the literature as a preliminary design tool. Although most studies devoting to the design of radial inflow turbine were developed for turbine using air as working fluid, recent studies about the design of SCO2 turbine indicated that Meanline Analysis is qualified to be a preliminary design tool. The simulation result of the Meanline Analysis was shown to be deviate from the design point, as expected. Fortunately, with the aid of CFD, the problem predicted by the simulation could be corrected and the model could be adjusted accordingly. At the end, with some bold assumption, the turbine model close to the expected pressure ratio and power output was devised.

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Lu, Kun Xian, and 盧昆賢. "Analysis of a Supercritical CO2 Rankine Cycle and its Comparison to Organic Rankine Cycles." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/50383888488528634455.

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碩士
國立清華大學
動力機械工程學系
104
About 20% ~ 50% energy is released to environment in the form of waste heat. The waste heat below 250℃ is difficult to recover due to its low thermal energy, but it has large amount and low fuel cost. ORC systems can efficiently convert this low temperature waste heat to electricity. Recently, due to the better heat transfer and low environmental impacts, S-CO2 Rankine cycle has shown pretty good potential in this field. A comparative study of S-CO2 Rankine cycle with R134a and R245fa ORC under 100℃ and 150℃ heat source is included in this study. Considering the pressure effect on performance and costs, the parameter settings for S-CO2 Rankine cycle are targeted on maximum power output. S-CO2 has better temperature matching with heat source so it can utilize heat source energy more efficiently. Besides, the high fluid density of S-CO2 can greatly reduce power unit size. Despite that the net power output per unit mass of working fluid in S-CO2 Rankine cycle is lower than that in ORCs, we can increase the mass flow rate of CO2 to improve the power output because of the very low fluid cost of CO2 compared to organic fluids. In order to realize the competence of S-CO2 Rankine cycle in real market, a comparative study with ORCs from Han Power is also included. Heat source temperature between 90℃~150℃ and inlet pressure of expander under 140 bar are recommended for S-CO2 Rankine cycle. But to commercialize S-CO2 Rankine cycle system, further studies and experiments on real equipment cost and component size are required.

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Lin, Sheng-Kuo, and 林聖國. "Configuration Design of A Supercritical CO2 Recompression Brayton Cycle including Impeller Design and CFD Analysis." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/pu25fb.

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Rieger, Mathias. "Advanced modeling and simulation of integrated gasification combined cycle power plants with CO2-capture." Doctoral thesis, 2013. https://tubaf.qucosa.de/id/qucosa%3A22935.

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The objective of this thesis is to provide an extensive description of the correlations in some of the most crucial sub-processes for hard coal fired IGCC with carbon capture (CC-IGCC). For this purpose, process simulation models are developed for four industrial gasification processes, the CO-shift cycle, the acid gas removal unit, the sulfur recovery process, the gas turbine, the water-/steam cycle and the air separation unit (ASU). Process simulations clarify the influence of certain boundary conditions on plant operation, performance and economics. Based on that, a comparative benchmark of CC-IGCC concepts is conducted. Furthermore, the influence of integration between the gas turbine and the ASU is analyzed in detail. The generated findings are used to develop an advanced plant configuration with improved economics. Nevertheless, IGCC power plants with carbon capture are not found to be an economically efficient power generation technology at present day boundary conditions.

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37

Van, Rooy Willem. "Solar thermal augmentation of the regenerative feed-heaters in a supercritical Rankine cycle with a coalfired boiler / W.L. van Rooy." Thesis, 2015. http://hdl.handle.net/10394/15901.

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Conventional concentrating solar power (CSP) plants typically have a very high levelised cost of electricity (LCOE) compared with coal-fired power stations. To generate 1 kWh of electrical energy from a conventional linear Fresnel CSP plant without a storage application, costs the utility approximately R3,08 (Salvatore, 2014), whereas it costs R0,711 to generate the same amount of energy by means of a highly efficient supercritical coal-fired power station, taking carbon tax into consideration. This high LCOE associated with linear Fresnel CSP technology is primarily due to the massive capital investment required per kW installed to construct such a plant along with the relatively low-capacity factors, because of the uncontrollable solar irradiation. It is expected that the LCOE of a hybrid plant in which a concentrating solar thermal (CST) station is integrated with a large-scale supercritical coal-fired power station, will be higher than that of a conventional supercritical coal-fired power station, but much less than that of a conventional CSP plant. The main aim of this study is to calculate and then compare the LCOE of a conventional supercritical coal-fired power station with that of such a station integrated with a linear Fresnel CST field. When the thermal energy generated in the receiver of a CST plant is converted into electrical energy by using the highly efficient regenerative Rankine cycle of a large-scale coal-fired power station, the total capital cost of the solar side of the integrated system will be reduced significantly, compared with the two stations operating independently of one another for common steam turbines, electrical generators and transformers, and transmission lines will be utilised for the integrated plants. The results obtained from the thermodynamic models indicate that if an additional heat exchanger integration option for a 90 MW (peak thermal) fuel-saver solar-augmentation scenario, where an annual average direct normal irradiation limit of 2 141 kWh/m2 is considered, one can expect to produce approximately 4,6 GWh more electricity to the national grid annually than with a normal coal-fired station. This increase in net electricity output is mainly due to the compounded lowered auxiliary power consumption during high solar-irradiation conditions. It is also found that the total annual thermal energy input required from burning pulverised coal is reduced by 110,5 GWh, when approximately 176,5 GWh of solar energy is injected into the coal-fired power station’s regenerative Rankine cycle for the duration of a year. Of the total thermal energy supplied by the solar field, approximately 54,6 GWh is eventually converted into electrical energy. Approximately 22 kT less coal will be required, which will result in 38,7 kT less CO2 emissions and about 7,6 kT less ash production. This electricity generated from the thermal energy supplied by the solar field will produce approximately R8,188m in additional revenue annually from the trade of renewable energy certificates, while the reduced coal consumption will result in an annual fuel saving of about R6,189m. By emitting less CO2 into the atmosphere, the annual carbon tax bill will be reduced by R1,856m, and by supplying additional energy to the national grid, an additional income of approximately R3,037m will be due to the power station. The annual operating and maintenance cost increase resulting from the additional 171 000 m2 solar field, will be in the region of R9,71m. The cost of generating 1 kWh with the solar-augmented coal-fired power plant will only be 0,34 cents more expensive at R0,714/kWh than it would be to generate the same energy with a normal supercritical coal-fired power station. If one considers that a typical conventional linear Fresnel CSP plant (without storage) has an LCOE of R3,08, the conclusion can be drawn that it is much more attractive to generate electricity from thermal power supplied by a solar field, by utilising the highly efficient large-scale components of a supercritical coal-fired power station, rather than to generate electricity from a conventional linear Fresnel CSP plant.
MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

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Matsuo, Bryce. "A Computational Study on the Thermal-Hydraulic Behavior of Supercritical Carbon Dioxide in Various Printed Circuit Heat Exchanger Designs." Thesis, 2013. http://hdl.handle.net/1969.1/149278.

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There has been an ever-increasing demand for power generation, which is predicted to grow as society becomes more advanced. However, tradition fossil fuels are beginning to deplete, and there is a great necessity for alternative fuel sources that will bridge the gap between energy production and consumption. To decrease the high demand alternative fuel sources are gaining in popularity. The supercritical carbon dioxide Brayton power cycle has been proposed as a possible cycle for nuclear and concentrated solar power generation. Two main advantages of having supercritical carbon dioxide are the large property variations and component size associated with power cycle. Forced convection heat transfer of supercritical carbon dioxide in printed circuit heat exchanger geometries were investigated in the following study using a finite volume framework and the FLUENT 12.1 code. The geometries of interest were: non- chamfered zig-zag, chamfered zig-zag, and air foil. Flow through the three geometries was in the horizontal orientation and subject to a heating mode operation. A range of testing conditions were explored, including operating pressures between 7.5 to 10.2 MPa with the mass flux ranging from 326 to 762 kg/m2-s. Due to the turbulent nature of this problem, the k−E with enhanced wall treatment and shear stress transport k−ω turbulence models were considered. With this addition a total of 54 simulations were performed. Results indicated that there was an increase in the heat transfer coefficient as the supercritical carbon dioxide reached the pseudocritical temperature, conversely as there was an increase in operating pressure, the heat transfer coefficient decreased. Nevertheless, this increase near the pseudocritical temperature was due to a sharp increase in the specific heat. Mass flux effects indicated that there was an increase in heat transfer as the mass flux was increased. This was due to the increase in Reynolds number near the pseudocritical temperature. Next, pressure losses were investigated for the three geometries. The non-chamfered zig-zag channel had the greatest pressure loss associated with it, while the air foil channel had the least. Based on the results, the ratio of the friction factor to heat transfer for the non-chamfered and chamfered zig-zag geometries were approximately 2.65 and 1.57 times higher than for the air foil, thus leading to the idea that the air foil channel may be best suited for practical applications. Finally, the simulation results were compared to experimental data and existing correlations. Many existing correlations failed to accurately predict the magnitude of heat transfer, although they exhibited a similar trend. A new correlation was developed for the zig-zag geometries based on the numerical data obtained during this investigation and published experimental data. The new correlation is able to predict the maximum heat transfer coefficient within 12.4%.

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39

Martinho, Ana Rita Mota. "Life cycle assessment of a novel CO2 capture technology (hgts) on retrofitting coal and natural gas power plants: portugal case study." Master's thesis, 2020. https://hdl.handle.net/10216/128433.

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Martinho, Ana Rita Mota. "Life cycle assessment of a novel CO2 capture technology (hgts) on retrofitting coal and natural gas power plants: portugal case study." Dissertação, 2020. https://hdl.handle.net/10216/128433.

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