Dissertationen zum Thema „Combined exergy and pinch analysis“

This thesis addressesth e analysisa nd design of commercial power plants by using the Combined Pinch and Exergy Approach. Current practice in design for commercial power plants heavily relies on experience and computer simulation and lacks systematic design methodologies. On the contrary, Pinch Technology allows systematic and generic approaches to chemical process design in which targets are set prior to design. These approaches can address issues related to process integration and optimisation. This thesis exploits the analogy between power plant design and chemical process design and applies the philosophy of Pinch Technology to the field of power plant design. In this thesis, the "onion" model used to represent the hierarchy of chemical process design is applied to power plant design. This model decomposes the whole design problem into three relatively simple tasks, including turbine system selection, heat exchanger network (HEN) design and fuel supply determination. Complex interactions exist between these individual components. To describe the complex interactions between the different components, a qualitative tool called the Combined Pinch and Exergy Representation (CPER) has been developed. The CPER allows engineers to visualise the overall performance of a power plant and the interactions between components. This diagram can also help engineers to screen design options. A quantitative tool, called the shaftwork targeting approach, has been developed in this thesis to evaluate each possible design option and identify the most promising one ahead of detailed simulation and designA tool called the Exergy Remaining Problem Analysis (ERPA) has been developed to guide HEN design. This allows the design to achieve the shaftwork targets. By evaluating the impact of individual matches on the remaining problem, the ERPA can determine the influence of individual matches on shaftwork generation. By detecting inappropriate matches, the ERPA can ensure that the HEN design meets the shaftwork targets. Based on the "onion" model of power plant, a systematic and generic approach to power plant design has been developed. In this approach, power plant design starts with the turbine system, then moves to the heat exchanger network and the fuel supply. This approach is entirely general which can be applied for design of different power plants. The significance of the new approach is that it enables engineers to screen possible design options with physical understanding and identify the most promising design option ahead of detailed simulation and design. This speeds up the overall design process and ensures that an optimal solution is obtained. vi

La question de l'énergie prend de plus en plus d'importance pour le secteur industriel, qui consomme beaucoup d'énergie. Pour remédier à cette difficulté, l'analyse exergétique et l'analyse exergoéconomique semblent être des techniques très efficaces puisqu'elles permettent aux opérations industrielles d'être plus efficaces tout en réduisant leur impact environnemental et en maximisant les bénéfices économiques. Dans ce contexte, l'objectif principal de l'étude présentée dans cette thèse est d'améliorer l'efficacité énergétique de la centrale de cogénération existante via différentes possibilités d'amélioration de la production d'électricité afin d'alimenter le réseau national à partir de bagasse excédentaire et ainsi de démontrer la valeur de cette approche pour l'analyse de l'efficacité énergétique des processus et des utilités. De plus, promouvoir une technologie intégrée de pointe pour la conversion des sous-produits de la canne à sucre disponibles en indicateurs énergétiques alternatifs bio fuel pour un avantage économique et pour alléger la charge environnementale a été réalisée.Cette thèse présente une méthodologie générique de la gestion énergétique des procédés thermiques couplés avec le simulateur de procédé ProSimPlus® qui est bien adaptée aux études d'efficacité énergétique dans une centrale de cogénération. Cette étude automatise entièrement l'analyse exergétique en présentant l'ensemble du bilan exergétique dans un seul logiciel, en plus d'utiliser des expressions génériques pour le travail et les flux de chaleur.Trois scénarios d'exploitation (cas I - le « réseau » et l'"usine » fonctionnant simultanément, le cas II - le réseau fonctionne et l'usine « OFF », et le cas III - le réseau « OFF » et l'usine « ON ») ont été utilisés pour examiner les analyses exergétiques et exergoéconomiques d'une installation de cogénération.En raison de l'imprévisibilité du marché de l'énergie en termes de disponibilité et de prix, le choix du mode de fonctionnement approprié pour équilibrer la faisabilité et la rentabilité des procédés chimiques est devenu un sujet important dans le domaine industriel. Le choix de la configuration d'exploitation optimale est crucial pour la stabilité d'une installation de traitement, en particulier lorsque l'alimentation du réseau n'est pas constante. Le simulateur de procédé ProSim Plus® a été utilisé pour créer un jumeau numérique de la section de cogénération à turbine à vapeur du côté des services publics de la sucrerie de Wonji-Shoa en Éthiopie, à partir de données réelles.De plus, L'analyse combinée du pincement et de l'exergie (CPEA) analyse initialement la représentation des courbes composites chaudes et froides (HCCC) du cycle de la vapeur et spécifie les besoins en énergie et en exergie. Les courbes composites d'exergie équilibrées générées sont utilisées pour visualiser les pertes d'exergie dans chaque composant des échanges thermiques de procédé et de service. Par conséquent, l'analyse combinée de l'exergie et du pincement révèle que davantage d'économies d'énergie peuvent être réalisées en réduisant la destruction de l'exergie dans la centrale de cogénération (∆Tlm).Enfin, un concept de conception prenant en compte les critères permettant d'identifier les limites supérieures théoriques de l'approche potentielle de conversion de la biomasse des sous-produits de la canne à sucre en indicateurs énergétiques a été présenté. Pour analyser le potentiel de captage du carbone de la biomasse, l'évaluation du modèle de conversion de masse stœchiométrique et des indicateurs d'efficacité énergétique a été formulée. Cela montre que la diversification multiproduit, des matières premières aux biocarburants, dans le cadre de systèmes de processus intégrés, pourrait potentiellement réduire le déficit énergétique et gérer le fardeau environnemental
The energy issue is becoming increasingly important for the industrial sector, which consumes a considerable amount of energy. In spite of the fact that the scientific community should continue to seek alternative energy sources, a short-term option would be to rely on more reasonable energy consumption. To address this difficulty, exergy and exergoeconomic analysis looks to be very effective techniques since it allows industrial operations to be more efficient while also reducing their environmental impact and maximize the economic benefits. In this context, the major objective of the study presented in this dissertation is to improve the energy efficiency of the existing cogeneration plant for further possibilities of electricity generation improvement to supply to the national grid system from surplus bagasse and also to demonstrate the value of this approach for analysis of energy efficiency of processes and utilities. Moreover, promoting advanced integrated technology for the conversion of available sugarcane byproducts (bagasse, molasses, and filter cake) to alternative energy indicators (bioethanol, alkane, and syn-gas or synthesis gases) for economic benefit and to alleviate the environmental load from the depilation of wastes especially in the downstream area.This dissertation presents a generic technique for energy balancing in thermal processes coupling with ProSimPlus® process simulator proved to be well-suited for energy efficiency studies in a cogeneration plant. This study fully automates exergy analysis by presenting the entire exergy balance within a single piece of software in addition to employing general expressions for work and heat streams. Furthermore, three operating scenarios (case I - both the “Grid” and the “Factory” operating simultaneously, Case II – the grid operates and the factory “OFF”, and Case III – the grid “OFF” and the factory “ON” scenarios) have been used to examine the exergy and exergoeconomic analyses of a cogeneration facility.Because of the unpredictability of the energy market in terms of availability and pricing, selecting the appropriate operating mode to balance feasibility and profitability of chemical processes has become a hot subject in the industrial arena. Choosing the optimal operating setup is crucial for the stability of a process plant, especially when the grid supply is not constant. The ProSim Plus® process simulator was used to create a digital twin of the steam turbine cogeneration section on the utility side of the Wonji-Shoa sugar mill in Ethiopia, using actual data. Moreover, a steam power plant was simulated in a ProSimPlus ® simulator, and operating parameters of the steam turbine were analyzed utilizing the exergy concept with a pinch-based technique. The Combined Pinch and Exergy Analysis (CPEA) initially analyses the depiction of the Hot and Cold Composite Curves (HCCCs) of the steam cycle and specifies the energy and exergy requirements. The fundamental assumption of the minimal approach temperature difference (〖∆T〗_lm) necessary for the pinch analysis is represented as a unique exergy loss that raises the heat demand (heat duty) for power generation. On the other hand, the exergy composite curves focus on the potential for fuel saving throughout the cycle having opportunities for heat pumping in the process. Finally, a conceptual design that considers the criteria to identify the upper theoretical limits of biomass conversion to enhance the potential approach to the conversion of sugarcane byproducts into energy indicators forwarded. In order to analyze the biomass carbon-capturing potential, the model assessment of stoichiometric mass conversion and energy efficiency indicators were formulated. Modeling plays up the importance of stoichiometric efficiency of biomass conversion into multi-product diversification of feedstock within integrated process schemes could have the potential to fill the energy gap and to manage environmental load

In this thesis, several configurations of combined cycle cogeneration systems proposed by the author and an existing system, the Bilkent Combined Cycle Cogeneration Plant, are investigated by energy, exergy and thermoeconomic analyses. In each of these configurations, varying steam demand is considered rather than fixed steam demand. Basic thermodynamic properties of the systems are determined by energy analysis utilizing main operation conditions. Exergy destructions within the system and exergy losses to environment are investigated to determine thermodynamic inefficiencies in the system and to assist in guiding future improvements in the plant. Among the different approaches for thermoeconomic analysis in literature, SPECO method is applied. Since the systems have more than one product (process steam and electrical power), systems are divided into several subsystems and cost balances are applied together with the auxiliary equations. Hence, cost of each product is calculated. Comparison of the configurations in terms of performance assessment parameters and costs per unit of exergy are also given in this thesis.

Dans la perspective du présent scénario énergétique, ce travail de thèse propose une méthodologie qui associe la méthode du pincement à l’analyse exergétique de manière à dépasser leurs limitations individuelles aboutissant à une conception améliorée aux deux niveaux : paramètres opératoires et topologie. Une méthodologie globale, consistant à hybrider les deux méthodes thermodynamiques dans une approche entrelacée avec des règles heuristiques et une optimisation numérique, est donc évoquée. À l'aide de nouveaux critères d'optimisation basés sur l’exergie, l'analyse exergétique est utilisée non seulement pour évaluer les pertes d’exergie mais également pour guider les améliorations potentielles des conditions de fonctionnement et de structure des procédés industriels. En plus, au lieu de considérer uniquement l’intégration de la chaleur pour satisfaire des besoins existants, la méthodologie proposée étend la méthode de pincement pour inclure d’autres formes d’exergie récupérables et exploiter de nouvelles voies de synergie via des systèmes de conversion. Après avoir présenté les lignes directrices de la méthodologie proposée, l’approche est démontrée sur deux systèmes industriels, un procédé d’hydrotraitement de gasoil sous vide et un procédé de liquéfaction de gaz naturel. L’application du cadre méthodologique à des processus réalistes a montré comment ajuster les conditions opératoires de chaque procédé et comment mettre en œuvre des systèmes de conversion générant des économies d’énergie substantielles
In the perspective of the prevailing and alarming energy scene, this doctoral work puts forward a methodology that couples pinch and exergy analysis in a way to surpass their individual limitations in the aim of generating optimal operating conditions and topology for industrial processes. A global methodology, a hybrid of the two thermodynamic methods in an intertwined approach with heuristic rules and numerical optimization, is therefore evoked. Using new optimizing exergy-based criteria, exergy analysis is used not only to assess the exergy losses but also to guide the potential improvements in industrial processes structure and operating conditions. And while pinch analysis considers only heat integration to satisfy existent needs, the proposed methodology allows including other forms of recoverable exergy and explores new synergy pathways through conversion systems. After exhibiting the guidelines of the proposed methodology, the entire approach is demonstrated on two industrial systems, a vacuum gasoil hydrotreating process and a natural gas liquefaction process. The application of the methodological framework on realistic processes demonstrated how to adjust each process operating conditions and how to implement conversion systems ensuing substantial energy savings

The dissertation investigates the issues of efficient energy use in building engineering systems possibilities by applying processes integration. Indoor climate formation systems are indicated as signally energy use building engineering systems. Traditional methods for evaluation of heat transfer in heat exchangers tender limited solutions for efficiency use of energy in them. The main object of dissertation is to evaluate processes integration method application possibilities for determination and improving of public buildings engineering systems. The dissertation also focuses on combine the possibilities of processes integration in building engineering systems with minimizing exergy streams in the systems. The paper approaches a few major tasks: determination of problematic building engineering systems, equipment and processes by viewpoint of energy efficiency, analysis of ventilation design solutions, creation of algorithm for exergy input minimizing in building engineering systems processes by combination of thermodynamical and Pinch analysis methods. The dissertation consists of four parts including Introduction, 4 chapters, Conclusions and References. The introduction reveals the investigated problem, importance of the thesis and the object of research and describes the purpose and tasks of the paper, research methodology, scientific novelty, the practical significance of results examined in the paper and defended statements. The introduction ends in presenting the... [to full text]
Disertacijoje nagrinėjamos procesų integracijos metodo taikymo galimybės sprendžiant efektyvaus energijos vartojimo pastatų inžinerinėse sistemose problemas. Tarp pastato inžinerinių sistemų darbe išskiriamos ženkliau energiją naudojančios, mikroklimatą pastatuose formuojančios sistemos. Klasikiniai tyrimo metodai, skirti šilumos mainams šilumokaičiuose, kurie atlieka šilumos perdavimo funkciją, nagrinėti pateikia gana ribotus sprendinius, kaip efektyviai naudoti energiją juose. Pagrindinis disertacijos tikslas – įvertinti procesų integravimo metodo taikymo galimybes viešųjų pastatų inžinerinių sistemų termodinaminiam efektyvumui nustatyti ir gerinti. Disertacijoje taip pat siekiama derinti procesų integracijos galimybes inžinerinėse sistemose siekiant minimizuoti eksergijos srautus jose. Darbe sprendžiami keli pagrindiniai uždaviniai: probleminių, energinio efektyvumo požiūriu, pastato inžinerinių sistemų, įrenginių ir procesų jose nustatymas, vėdinimo sistemų projektinių sprendimų ypatybių nustatymas, algoritmo, skirto procesų eksergijos sąnaudoms mažinti pastato inžinerinėse sistemose sudarymas derinant termodinaminės ir Pinch analizės metodus. Disertaciją sudaro įvadas, keturi skyriai, rezultatų apibendrinimas, naudotos literatūros ir autorės publikacijų disertacijos tema sąrašai. Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas... [toliau žr. visą tekstą]

Disertacijoje nagrinėjamos procesų integracijos metodo taikymo galimybės sprendžiant efektyvaus energijos vartojimo pastatų inžinerinėse sistemose problemas. Tarp pastato inžinerinių sistemų darbe išskiriamos ženkliau energiją naudojančios, mikroklimatą pastatuose formuojančios sistemos. Klasikiniai tyrimo metodai, skirti šilumos mainams šilumokaičiuose, kurie atlieka šilumos perdavimo funkciją, nagrinėti pateikia gana ribotus sprendinius, kaip efektyviai naudoti energiją juose. Pagrindinis disertacijos tikslas – įvertinti procesų integravimo metodo taikymo galimybes viešųjų pastatų inžinerinių sistemų termodinaminiam efektyvumui nustatyti ir gerinti. Disertacijoje taip pat siekiama derinti procesų integracijos galimybes inžinerinėse sistemose siekiant minimizuoti eksergijos srautus jose. Darbe sprendžiami keli pagrindiniai uždaviniai: probleminių, energinio efektyvumo požiūriu, pastato inžinerinių sistemų, įrenginių ir procesų jose nustatymas, vėdinimo sistemų projektinių sprendimų ypatybių nustatymas, algoritmo, skirto procesų eksergijos sąnaudoms mažinti pastato inžinerinėse sistemose sudarymas derinant termodinaminės ir Pinch analizės metodus. Disertaciją sudaro įvadas, keturi skyriai, rezultatų apibendrinimas, naudotos literatūros ir autorės publikacijų disertacijos tema sąrašai. Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas... [toliau žr. visą tekstą]
The dissertation investigates the issues of efficient energy use in building engineering systems possibilities by applying processes integration. Indoor climate formation systems are indicated as signally energy use building engineering systems. Traditional methods for evaluation of heat transfer in heat exchangers tender limited solutions for efficiency use of energy in them. The main object of dissertation is to evaluate processes integration method application possibilities for determination and improving of public buildings engineering systems. The dissertation also focuses on combine the possibilities of processes integration in building engineering systems with minimizing exergy streams in the systems. The paper approaches a few major tasks: determination of problematic building engineering systems, equipment and processes by viewpoint of energy efficiency, analysis of ventilation design solutions, creation of algorithm for exergy input minimizing in building engineering systems processes by combination of thermodynamical and Pinch analysis methods. The dissertation consists of four parts including Introduction, 4 chapters, Conclusions and References. The introduction reveals the investigated problem, importance of the thesis and the object of research and describes the purpose and tasks of the paper, research methodology, scientific novelty, the practical significance of results examined in the paper and defended statements. The introduction ends in presenting the... [to full text]

A la veille d’une nouvelle conférence sur le climat, les questions environnementales demeurent plus que jamais au premier plan de la vie publique. La lutte contre le réchauffement climatique, et les émissions de gaz à effet de serre, dont l’attribution à l’activité humaine fait globalement l’objet d’un consensus scientifique, constituent l’un des plus grands défis de l’humanité pour les prochaines années. Dans ce contexte, l’amélioration de l’efficacité énergétique des sites de production est une des préoccupations des industriels. Les réglementations environnementales, et les fluctuations des cours de l’énergie les forcent à continuellement améliorer leurs procédés pour en maintenir la compétitivité. Ceux-ci doivent ainsi pouvoir disposer d’outils leur permettant d’effectuer des diagnostics énergétiques sur les installations, leur facilitant la prise de décision et leur permettant d’élaborer des solutions d’efficacité énergétique sur leurs sites industriels. Les travaux présentés dans ce document visent à introduire une méthodologie d’analyse et de rétro-conception pour l’amélioration énergétique des procédés industriels. Cette méthodologie, qui s’appuie sur une utilisation combinée de la méthode du pincement et de l’analyse exergétique, se décompose en trois grandes étapes : la première comprend le recueil des données, la modélisation et la simulation du procédé. La deuxième étape, dédiée à l’analyse du procédé, est elle-même divisée en deux phases. La première, qui s’appuie pour l’essentiel sur l’utilisation de la méthodologie du pincement, s’intéresse uniquement à l’analyse du système de fourniture et de récupération de l’énergie thermique. Si cela s’avère nécessaire, le procédé complet est étudié dans une deuxième phase. L’analyse pincement se limitant à l’étude des procédés thermiques, une méthodologie d’analyse exergétique est mise en œuvre. Cette méthodologie s’appuie sur l’implémentation de l’analyse exergétique dans l’environnement ProSimPlus, entreprise par Ali Ghannadzadeh, et poursuivie pendant cette thèse. Les formules d'exergie ont été affinées pour s’ajuster aux différents modèles thermodynamiques. L’approche d’analyse proposée dans ce manuscrit est basée sur l’utilisation d’une nouvelle représentation graphique des bilans exergétiques : le ternaire exergétique. Ce dernier permet d’illustrer tous les aspects des bilans exergétiques et ainsi d'assister l’ingénieur dans l’analyse du procédé. La troisième étape s’intéresse à la conception pour l’amélioration énergétique. Alors que l’analyse du pincement propose des solutions d’amélioration, l’analyse exergétique ne le permet pas. Elle nécessite l’apport d’une certaine expertise pour aboutir au développement de solutions d’améliorations. Pour pallier ce problème, l’expertise est en partie capitalisée dans un système de raisonnement à partir de cas. Ce système permet de proposer des solutions à des problèmes nouveaux en analysant les similarités avec des problèmes anciens. Cet outil se révèle utile pour définir des solutions locales d’améliorations énergétiques. L’analyse du pincement associée à des outils numériques est ensuite utilisée pour concevoir des propositions complètes d’améliorations. La seconde partie de ce manuscrit présente cette étape.

La méthode du Pincement a été développée et utilisée dans le secteur de la pétrochimie. Le nombre de flux y est important et la consommation énergétique est un critère décisionnel fort. D'autres secteurs énergivores tels la métallurgie, la production de papier et de pâte à papier ou l'industrie agroalimentaire peuvent bénéficier de cette approche structurée. Par ailleurs, l'intégration d'utilités thermodynamiques complexes comme les pompes à chaleur ou les unités de cogénération peut réduire significativement la consommation d'énergie d'un procédé, sans avoir à en modifier la technologie.Un algorithme de conception d'un réseau d'échangeurs à partir de flux thermiques à été choisi dans la littérature, puis deux fonctionnalités lui ont été ajoutées : la différenciation des technologies d'échangeur et la prise en compte de flux "disponibilités" à température de sortie variable. Un module de présélection a été développé pour proposer et dimensionner des utilités thermodynamiques à partir de la grande courbe composite et d'un critère exergétique. Il est utilisé en amont de la conception du réseau d'échangeurs.Ces deux algorithmes ont été intégrés dans un logiciel dédié à l'intégration énergétique de procédés à partir des flux thermiques des opérations unitaires. Plusieurs validations ont été faites sur des cas théoriques de référence issus de la littérature ainsi que sur des cas industriels réels nécessitant la modélisation des procédés. L'enchainement des deux algorithmes débouche sur l'obtention de résultats concrets et technologiquement réalistes. L'amélioration apportée par les solutions est calculable à chaque étape
The pinch analysis has been developed and exploited in the petrochemical sector. There are numerous heat fluxes and energy consumption is a strong decision criterion. Other energy-intensive sectors such as metallurgy, pulp and paper and food & drink industry can benefit from this systemic approach. Moreover, integration of complex thermodynamic utilities such heat pumps or Combined Heat and Power units can significantly reduce the energy consumption of a process, without having to interfere with the process technology.An algorithm for heat exchangers network design from heat fluxes was chosen in the literature and two features were added to it: Ability to pick different heat exchanger technology and creation of "availabilities" heat fluxes whose outlet temperature is variable. Preselection tool has been developed from grand composite curve and exergetic criterion to propose and pre-size thermodynamics utilities. It is used upstream of the heat exchangers network design step.These two algorithms have been integrated into a software for energy integration of process unit operations heat fluxes. Several validations were made on study cases from the literature as well as on industrial cases which require process modelling. The both algorithms sequence allows achieving practical and technologically feasible results. Improvement on energy consumption provided by the solutions can be calculated at each step

Cette étude concerne un système de stockage d’électricité basé sur le stockage thermique. Le principe est de convertir de l’électricité issue d’énergies renouvelables en chaleur lorsque la production est supérieure à la demande, de conserver cette chaleur puis de la reconvertir en électricité lorsqu’un besoin se présente. Le système proposé s’appuie sur une technologie de stockage sensible à haute température : le stockage régénératif gaz/solide. Ce stockage est associé à une boucle de charge et à un cycle thermodynamique de restitution électrique. Dans cette étude, deux architectures sont étudiées pour ce dernier : la première est basée sur un cycle gaz, la seconde sur un cycle combiné Joule/Rankine. Un modèle global du système est développé sur la base d’une modélisation de chaque composant à un niveau de détail approprié. Sur la base de ce modèle, une analyse thermodynamique est menée. Celle-ci identifie le rendement exergétique global du procédé, proche de celui d’un cycle à combustion. Une analyse exergétique détaillée du stockage identifie les principaux postes d’irréversibilités dans ce composant. Elle montre qu’il est possible d’optimiser de manière relativement simple ses performances en jouant sur son dimensionnement. Par la suite, une analyse économique montre qu’en dépit de ses performances inférieures, le cycle gaz est associé à des coûts d’investissement limités qui rendent son utilisation pertinente. En termes de coût du stockage, le système étudié est compétitif avec des solutions comme les batteries
This study concerns an electricity storage system based on thermal energy storage. Its overall purpose is to convert electricity produced by renewable energies into heat when the supply exceeds the demand. This heat is stored for a few hours and converted back to electricity when there is a need for it. The proposed system relies on a high temperature sensible thermal energy storage technology known as the gas/solid packed bed thermal storage. This storage comes with a charging loop and a thermodynamic cycle to carry out the heat to electricity conversion. In this study, two main architectures are considered for this cycle: a simple gas cycle and a Joule/Rankine combined cycle. Each component is modeled with an appropriate level of detail in order to create a global model of the system. This model is used to carry out a thermodynamic analysis. This study calculates the global exergy efficiency of the whole process, which is close to exergy efficiency of a combustion cycle. A detailed exergy analysis of the storage allows to identify the main phenomena behind the availability losses of this component. It shows that it is possible to increase the efficiency of the storage by modifying its sizing. Apart from this study, an economic analysis shows that regardless of its low energy and exergy efficiencies, the gas cycle comes with limited investment costs which insure an interesting profitability. In terms of storage cost, the proposed system is close to other electricity storage solutions like batteries

The worldwide power industry structure is changing to a market economy to ensure commercial availability. This captive industry is essential for national development power & electricity infrastructure, but more than 40% of the input energy is lost during the plant operation with different thermal utilities. These precious dumped or waste heats have tremendous potential for the generation of multiple effects of energy like heating-power & cooling and also help to enhance the efficiency of thermodynamic power cycles. The novel and advanced thermodynamic systems are important because solar based on refrigeration systems have been discussed in the proposed title of research for different categories of waste heat source recovery. Therefore, this study investigates both theoretical and software-based simulation into the distinguishing feature of the advanced concept of the Rankine model called Organic Rankine Cycle (ORCs), which has three useful output heating-power and cooling production. The present research work focuses on two significant thermodynamic analyses: the integration of advanced thermodynamic cycles and the heat recovery system with employment of solar thermal systems, and the second is complete thermodynamic analysis, consisting of Energy and Exergy analysis. The traditional approach of thermodynamics analysis is based on the 1st law and 2nd law of thermodynamics. The 1st law of thermodynamics (FLT) gives the work, heat transfer, energy performance, thermal efficiency. In contrast, the 2nd law of thermodynamics (SLT) provides the system's actual performance by entropy generation (exergy) principle. The quantity and quality of energy (useful energy) are estimated through the FLT and SLT. The main objective of 2E analysis (energy-exergy) is to examine the theoretical and actual performance of proposed thermal systems to identify energy loss in integrated parts of the thermal system for efficient performance. The conventional mathematical modeling is suitable for physical system simulation, complex mathematical model development, and quantitative analysis. The statistical modeling helps to error estimation, system optimization, and comparative study of fundamental & predicted complex analysis results. Several statistical analysis methods are available with new artificial intelligence applications like linear or multi-linear regression method, artificial neural network method, least square method, and Taguchi-Annova xi | P a g e method. All optimization techniques are suitable for the least parameter identification, error count with complex problem-solving. This Research work is referred to as the multi-linear regression method for parametric identification and actual- predicted result comparisons. This research work consisted of four thermodynamics models for combined cooling, heating, and power generation effect using waste heat of different power plants. 1. Stack Flow heat recovery of Combined GT-ST plant using the LiBr-H2O vapor absorption cooling system. 2. Steam Turbine Heat recovery using solar integrated double bed activated carbonmethanol and activated carbon-R134a Vapor adsorption refrigeration system for space cooling purpose. 3. Reheating Rankine power generation heat recovery of the condenser by using a solar integrated organic Rankine cycle for combined cooling, heating, and power generation effect. 4. Combined reheating and regeneration steam power cycle, analysis and process heat recovery through a vapor generator by using the Vapour jet refrigeration system. All the above four systems are suitable for the low, medium, and high-grade temperature sources of heat recovery and produce the combined effect of energy efficiently. A parametric study has been carried out to analyze some influenced parameters such as condenser temperature, turbines (GT&ST) output, ORC performance, cooling effect of VARS, and vapor adsorption refrigeration and ejector cooling system. The influencing effect of gas turbine inlet temperature, compression ratio with different combustion of natural gases provides the best performance of the GT system for operation of ST plant under the different operating conditions of the compressor, GT, and combustion chamber. This case concluded as the maximum exergy loss found in the combustion chamber of GT system and exhaust flow system of ST system in terms of 41% and 8%, respectively. The combined and exergetic efficiency of the plant is estimated to be 41% and 38.5% respectively. In the present statistical model, 4 levels and 3 factors (Pressure ratio, operating temperature and type of fuel gases) have been considered. Furthermore, overall efficiency, gas turbine efficiency, heat loss in GT plant, Exergy destruction in thermal xii | P a g e utilities like Compressor, combustion chamber and gas turbine are investigated. The statistical modeling concluded that the comparative results of actual and predicted results at different compression ratio of combustible gases which affects the overall performance of combined GT-ST plant. This study helps to justify possible efficiency improvement by identifying the irreversibility of plant utilities. The combined reheating-regeneration power generation analysis concluded that the energy- exergy analysis for the Boiler, turbines, Feed heaters, condenser and pump majorly. The result of the thermodynamic analysis is computed as 42% of plant thermal efficiency, 70 % of steam generation unit efficiency. Maximum heat absorbed by economizer of plant as 39% is achieved, and quality of steam was found around 89-90% with 40TPH of coal consumption. Boilers, HPT, IPT, Super heaters have found best performance in analysis and Reheating-Regenerative Rankine method improves 6-8% in thermal efficiency. It has been observed that energy efficiency (theoretical) is always more than energy efficiency (actual), which means it helps to understand the performance of thermal power plants and justify possible efficiency improvement with efficient power generation opportunities like waste heat recovery technology employment. The performance of cooling systems of proposed research work is carried out the source temperatures available for both beds of Vapor adsorption refrigeration systems (VAdRS) from condenser exhaust, ETC solar system. The adsorbent and adsorbate pair for double bed VAdRS has been recommended by activated carbon as adsorbent and methanol and R134a as the adsorbate. The significant findings of present work are the maximum irreversibility found in Boiler as 47% in thermal power plants and solar generators as 12% of adsorption machines, whereas overall cooling effect from adsorption systems increases by 15% in double bed combination. EES software is used for all analyses. The VAM machine for stack flow heat recovery is performed by 0.708 of COP, a suitable cooling for space and water chilling purposes.

Power plant performance can be assessed by the method of thermodynamic analysis. The goal of this thesis is to perform a thermodynamic analysis on the University of Massachusetts’ Combined Heat and Power (CHP) District Heating System. Energy and exergy analyses are performed based on the first and second laws of thermodynamics for power generation systems that include a 10-MW Solar combustion gas turbine, a 4-MW low pressure steam turbine, a 2-MW high pressure steam turbine, a 100,000 pph heat recovery steam generator (HRSG), three 125,000 pph package boilers, and auxiliary equipment. The University of Massachusetts’ CHP plant delivers all of the campus’ steam and nearly all its electricity to the more than 200 buildings and nearly 10 million gross square feet of building space. Two 20-inch main steam transmission lines connect the plant to the campus. On an annual basis the plant generates approximately 1,100,000,000 pounds of steam and 100,000,000 kWh of electric power. The plant has a SCADA (Supervisory Control and Data Acquisition) system. Rockwell Automation’s RSLinx OPC (Object Linking and Embedding for Process Control) server acquires data from up to 675 field instruments in the plant which is used for carrying out the analyses. The latest pollution control technologies, including advanced combustion turbine low NOx burners, advanced Selective Catalytic Reduction and Oxidation Catalyst pollution control technologies are employed in the plant. System efficiencies are calculated for a wide range of component operating loads. Factors affecting efficiency of the CHP district heating system are analyzed. In the analysis, actual system data is used to assess the district heating system performance, energy and exergy efficiencies and exergy losses. Energy and exergy calculations are conducted for the whole year on an hourly basis. Factors affecting efficiency of the CHP district heating system are analyzed and recommendations made to improve the operating efficiency. The results show how thermodynamic analysis can be used to identify the magnitudes and location of energy losses in order to improve the existing system, processes or components.

The objective of the presented work is to develop a Thermodynamic optimization method in order to optimize the efficiency of a combined cycle gas turbine (CCGT) power plant and suggest ways of improving the efficiency. The Thermodynamic analysis provides a complete diagnosis of the performance of the combined cycle power plant, both in energetic and in exergetic terms. The system considered in this thesis is a combined cycle power plant which couples the two power cycles, Brayton cycle (gas turbine), Rankine cycle (steam turbine). There are various ways in which the efficiency of both cycle individually can be improved. But when couple together optimization is different thing because improving efficiency of one cycle can adversely affect the efficiency of other cycle and of combined cycle gas turbine. By using thermodynamic analysis, parametric study is done in this work to find the optimum parameter at which efficiency of system is maximum. A program of numerical code is established using EES (Engineering Equation Solver) software to perform the calculations required for the thermodynamic analysis considering real variation ranges of the main operating parameters such as pressure, temperature, pressure ratio. The effects of theses parameters on the system performances are investigated. Parametric study has been performed using combined first and second law approach to investigate the effects of compressor air inlet temperature and pressure of steam on first and second law efficiency, power-to-heat ratio, exergy destruction in the system components.

Renewable energy resources are of great attention by many countries. However, volatile and intermittent nature of renewable energies has made their directly connect to the grid very challenging and costly. Therefore, it is essential to couple a renewable energy resource with an energy storage technology. Among different types of energy storage systems developed so far, compressed air energy storage (CAES) is a large-scale energy storage system which has distinguished advantages over other types of energy storage systems; such as large energy storage capacity, long operation time and short response time. Currently, there are two called conventional or Diabatic CAES (D-CAES) plants in operation one of which is in Huntorf (Germany) and the other is in McIntosh (USA). However, the main drawback of these D-CAES plants is their low cycle energy efficiency primarily due to a large energy loss during the system operation. To minimise the energy loss and improve the system performance, the structure of D-CAES evolved and new classifications of the CAES system were developed. In the present thesis, a wide literature review is firstly performed to obtain a broad overview of recent developments in various classifications of CAES systems and identify the research gap in this technology. Adiabatic CAES (A-CAES) is one of the main types of CAES systems. However, one of the most challenges associated with the A-CAES is variation of the air pressure and temperature during actual cyclic operation of the system particularly through expansion when the air flows out of the storage cavern. In this research, a comprehensive thermodynamic model is developed and validated with an experimental work to study the dynamic operational behaviour of a low-temperature A-CAES system. A sensitivity analysis is then performed to investigate the system performance under various operating conditions. The obtained results from the conducted analysis show that the system cycle efficiency is quite low compared to other types of energy storage systems. Therefore, there is a strong need to propose and develop a new energy storage technology which resolves the problems associated with the CAES system. The performed study on the A-CAES system and the pumped hydro concept are employed to develop the configuration and working principles of a combined Pumped-Hydro and Compressed Air (PHCA) energy storage. A comprehensive thermodynamic and exergy model is then developed to identify key parameters of the PHCA system and investigate its performance under two extreme isothermal and isentropic air compression/expansion in the storage vessel. Key parameters of the system include the pre-set pressure, storage pressure, air compression/expansion mode in the storage vessel, and pump/hydro turbine efficiency. The system performance is also characterised by the total input/output works, energy storage level in the system, overall cycle efficiency, and exergy destruction in main components of the system. The exergy model is then applied to evaluate the performance loss due to exergy destruction at each system component and identify their inefficiency under different operating conditions. In a PHCA energy storage system, energy is stored in a storage vessel. The dynamic fluid flow and heat transfer mechanism inside the storage vessel has a determining effect on performance of the PHCA system. In this research, the dynamic flow and heat transfer is simulated and analysed in a three-dimensional cylindrical storage vessel using a multiphase Volume of Fluid (VOF) and turbulence k − ε models. Momentum and energy equations are solved in a prescribed physical domain which is, in this study, a cylindrical storage vessel with an inner diameter of 60 cm and height of 100 cm. The numerical simulation is performed for one continuous operational cycle of the PHCA system. The results are presented for a wide range of governing parameters including the pre-set pressure, storage pressure, charging and discharging flow rates. The presented research provides a good understanding of performance of the PHCA system under different operating conditions. Also, this PhD thesis provides researchers and engineers with useful information for the primary system design and optimization based on the grid requirements and limitations. It also shows a bright view about applicability and practicality of the PHCA system in the Australia energy storage market.

Pinch Analysis, in the broadest sense, is concerned with the optimal use of resources (material or energy) in a multi-process system. Pinch Analysis based techniques have emerged for water systems over the past decade. A major assumption that has been made in applying these techniques is that a process system can be segregated into a set of process streams and a set of water streams. With this distinction in place, only the water streams are considered in the Pinch Analysis with the process streams represented implicitly. This approach has obvious limitations in situations where a clear distinction between process streams and water streams cannot be made. The chlor-alkali process is an example of a system in which the clear distinction between process streams and water streams cannot be made. Water is intrinsically involved in the process, serving as a carrier medium for raw materials and eventually becoming part of the products produced by the complex. Hydrochloric acid and caustic soda are reagents which are both used within and produced by the complex. These reagents are required by the process at a range of concentrations and the concentrated reagent is diluted to the required concentrations using demineralised water. Within the chlor-alkali complex, a number of effluents containing the reagent species are available and are typically sent to drain. It is conceivable that these effluents might be recovered and used for dilution purposes instead of demineralised water. This would bring about a reduction in the amount of water and concentrated reagent used and the amount of effluent produced by the complex. Given the economic value of these reagents relative to water, their recovery, if feasible, is likely to dominate the optimal water-use and effluent generation strategy. Current Water Pinch Analysis theory relies on the distinction being made between process streams and water streams and does not consider the recovery of reagents or the presence of desirable species within the system. In addition, the assumption is made that species are non-reactive; reactive species such as hydrogen chloride and sodium hydroxide, fall outside the scope of the current theory. The objectives of this study have included the development of an approach which is able to address these limitations of the existing theory. This approach, termed Combined Water and Materials Pinch Analysis seeks to identify optimal use strategies for raw materials and reagents, in addition to water-use and effluent generation. The approach combines mathematical programming with conceptual insights from Water Pinch Analysis. The approach is based on the optimisation of a superstructure which represents the set of all possible flow configurations for water, reagents and raw materials between the various operations within the process system; this problem is solved as a nonlinear programming (NLP) problem using standard optimisation tools. The application of the developed approach to the Sasol Polymers chlor-alkali complex at Umbogintwini, south of Durban, has been a further objective of this study. Given the variety of process operations present within the complex, which differ both in terms of their physical structure and function, individual process models for these operations were required. These models were described in terms of four basic functional elements, namely, mixing, flow separation, component separation and reaction, and incorporated into the superstructure. Given the complexity of the problem, the process system was divided into three subsystems which were optimised in isolation from each other. These results were subsequently integrated to reflect the performance of the subsystems in combination with each other. The results showed a potential reduction of 14% in water-use and 42% in effluent production by the complex, relative to the existing operating configuration. Amongst other savings in material use, the results indicated a 0.2% reduction in the use of salt, a 1.6% reduction caustic soda use and an 8.3% reduction in the use of hydrochloric acid. Economically, the potential saving identified was R 945 727 per annum, based on operating costs in the year 2000. The final objective of this study was the interpretation of the pinch as it relates to the Combined Water and Materials Pinch Analysis problem. A general definition of the pinch was proposed; according to this definition, the pinch corresponds to that constraint or set of constraints which limits the performance of the system, that is, prevents it from further improvement. For the Combined Water and Materials Pinch Analysis problem, this performance is measured in terms of the operating cost. This definition is thus a departure from its usual thermodynamic interpretation of the pinch; in addition, the pinch is defined in terms of a constraint or a set of constraints instead of a point. These constraints are identified by an analysis of the marginal values provided by the optimisation algorithm. Marginal values are also used as a means of identifying process interventions which may be effected such that the performance of the system may be improved further.
Thesis (M.Sc.Eng.)-University of Natal, 1989.

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfilment of the requirements for the degree of Doctor of Philosophy, 2020
Carbon capture and sequestration (CCS), fuel switching (switching from coal to natural gas fired power) and renewables are some of the most promising means with which mankind can combat climate change. Natural gas combined cycle (NGCC) power plants, which make use of both gas fired and steam cycle power generation are the most suitable and efficient fossil fuel power plants that can respond to renewable intermittence. Retrofitting the NGCC power plants with pre-combustion CSS allows the power plant to maintain its flexibility whilst capturing CO2 because pre-combustion capture occurs upstream; decoupled from the power cycle. Power to gas (PtG) is a promising technology being developed to overcome renewable intermittence through electrical energy storage (EES). It involves feeding off peak renewable energy to a water electrolyser which splits water into H2 and O2 before using the H2 to valorise CO2 from an industrial emission source into renewable methane in a methanation unit. The methanation unit is composed of Sabatier reactors that need to have their temperature controlled through recycle of their product gasses. The electrolysis can either be conducted at high temperature using an equimolar feed in water and CO2 in what is known as high temperature co-electrolysis (HTCE) or it can be conducted at lower temperatures using only water as a feed in what is known as low temperature electrolysis (LTE). A major by-product from both processes is high temperature methanation heat from the Sabatier reactors. This thesis presents studies on power to gas retrofitted to both LTE and HTCE electrolysers. The two processes were compared on: their ability to produce methane suitable for transportation in natural gas pipelines, their ability to produce renewable methane for onsite storage and their also compared on their energy and exergy efficiency’s. The two setups were also retrofitted to a NGCC power plant which itself was retrofitted with a pre-combustion capture sorbent enhanced water gas shift carbon capture and sequestration upstream. No effort is made within the setup to make use of the available heat in the reforming section; with HRSG steam extraction supplying all the required steam for the reformer. This was done with the goal of determining the utility in retrofitting the high temperature methanation heat with the power plant steam cycle for waste heat recovery. The baseline and capture plant efficiencies were also determined and compared with what is stated in the literature. A novel adaptation to an existing method for determining the physical exergy content of mass streams for flow sheet simulators was developed for ASPEN plus. The fundamental thermodynamic principles were first derived, before being interpreted according to the work of pioneers on the subject and then adapted for use in ASPEN plus. The adaptation involved developing a flow-sheet that could be used to acquire the important stream information from ASPEN plus which could then be used to conduct the calculations using excel or any other software of your choosing. A means of using the flowsheet to determine the thermal and pressure exergy components of the physical exergy of mass streams was also discussed. Additionally, a novel means for the designing HRSG’s for thermal power plants was developed that can be used with flowsheet simulators; a long-standing problem that has made research of power plant setups via simulation somewhat questionable until now. This technique was used to come up with a more accurate estimate for the efficiency penalty associated with pre-combustion carbon capture and sequestration on natural gas power plants. It was also used to determine the mechanical work that could be generated upon heat integration between the NGCC capture plant and the PtG retrofits. The technique developed could be implemented on a thermal power plant setup generating electricity from any hydrocarbon feed or waste heat stream with single or multi-pressure HRSG’s. It will especially prove useful for fossil fuel power plants that utilise HRSG steam extraction to provide the necessary steam for their CCS retrofits as well as geothermal, and combined heat and power plants. It can also be used to determine the efficiency of nuclear power plants with greater accuracy through simulation. The baseline NGCC power plant was simulated successfully and found to have a higher heating value [HHV] and lower heating value [LHV] efficiencies of 53.52% and 59.32% respectively which matched what is reported in the literature. Then the pre-combustion capture NGCC power plant was simulated and found to have lower than expected HHV and LHV efficiencies of 29.92% and 33.17% respectively. The LHV efficiency was 13.83% lower than what is reported in the literature of 47% and the HHV efficiency was 12.48% lower than what is reported in the literature of 42.4%.This disparity was attributed to the fact that a steam cycle flow-sheet for an NGCC pre-combustion capture power plant fitted with SEWGS is yet to be modelled in as much detail as it has in this thesis. This observation is backed by the exergy analysis (developed near the end of the study) conducted on the capture plant which found that the steam extracted for providing the necessary energy for the pre-combustion capture retrofit possess 35 MW of exergy. This amounts to 29.19% of the exergy available within the steam that reports to the turbines which explains the larger than expected efficiency penalty. The accuracy with which the exergy analysis was able to account for the drop in power production proves that the method proposed for conducting exergy analysis for flow-sheet simulators works. There is much potential to improve the performance of the retrofitted plant, with the exergy analysis revealing that there is 42.29 MW in exergy within the mass stream reporting from the SEWGS flash unit within the pre-combustion capture retrofit. The pre-combustion capture retrofit contributes 13% to the irreversibility of the entire capture plant. The molar composition of the product stream from the HTCE electrolyser is composed of: 38.8% carbon dioxide, 30.96% carbon monoxide and 30.24% hydrogen. This was attributed to the fact that only 48.3% of the water and CO2 fed was converted in the electrolyser, to produce H2, CO and O2 in an equimolar ratio according to the main reaction. When this product is used as feed to the methanation unit only one Sabatier reactor was needed to completely react all the hydrogen that was fed in. The final product failed to meet the specifications for pipeline transport with a methane composition of only 21% and a carbon dioxide composition of 76.53%. The Sabatier reactor reached a temperature of 313°C at the maximum Sabatier reactor recycle fraction of 0.9. The composition of the product stream from the LTE electrolyser was composed entirely of hydrogen due to the fact that it had a conversion of 99.99% after being fed a stream composed of 100% water. Since the hydrogen stream reporting from the electrolyser is pure; all the carbon dioxide required for methanation was fed to first Sabatier reactor. To ensure that there was enough CO2 and CO to satisfy the reaction stoichiometry for complete reaction within the methanation unit; the flow of water to the electrolyser was adjusted so that the molar flow in hydrogen from the unit is 4 times the molar flow of CO2 added to three times the molar flow of CO2 coming from the capture plant. The molar composition of methane coming from the first Sabatier reactor was 70.87% and the temperature of the reactor was 436.16°C at the maximum recycle fraction of 0.9. The product from the second Sabatier reactor was able to reach a composition in methane adequate for pipeline transport of 95 mole% for a recycle fraction of 78% at a reactor temperature of 259°C. A heat integration study determined that integrating the methanation heat in the HTCE PtG process with the HRSG in the pre-combustion capture NGCC power plant would reduce the LHV efficiency of the power plant by 48.85% to -15.68% whilst storing renewable energy. Another heat integration study determined that integrating the methanation heat in the LTE PtG process with the HRSG in the pre-combustion capture NGCC power plant would improve the LHV efficiency of the power plant by 6.32% to 39.49% whilst storing renewable energy. The LTE NGCC pre-combustion capture setup was deemed an adequate renewable adaptation to the traditional NGCC peaker plant. HTCE was deemed unsuitable as source of waste heat. A thermodynamic study determined that the efficiency of the HTCE electrolyser and the entire HTCE PtG processes were 31.49% and 42.21% with methane storage. The same study determined that the efficiency of the entire HTCE PtG processes will be 43.45% when the methane is prepared for pipeline transport instead. The exergy efficiency of the HTCE electrolyser and that of the entire HTCE PtG process were 87.07% and 84% respectively with methane storage. And the exergy efficiency of the entire HTCE PtG processes was 87% when the methane is prepared for pipeline transport. The electrolyser was found to contribute the most to the irreversibility within the retrofit (73%) and as a recommendation it is suggested that the temperature of the processes be lowered. Another study determined that the efficiency of the LTE electrolyser and that of the entire LTE PtG processes were 83.52% and 55.95% respectively with methane storage. When methane is prepared for pipeline transport instead the efficiency of the entire processes was 56.79%. The exergy efficiency of the LTE electrolyser and that of the entire LTE PtG retrofit were found to be 83.23% and 83.71% respectively with methane storage. The exergy efficiency of the entire processes was found to be 84.30% when the methane was prepared for pipeline transport instead. The electrolyser was again found to contribute most to the irreversibility within the retrofit (91%) and as a recommendation it is suggested that the temperature of the process also be lowered
CK2021