Academic literature on the topic 'Overall exergy efficiency, Optimisation'
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Journal articles on the topic "Overall exergy efficiency, Optimisation":
1
Unamba, Chinedu K., Paul Sapin, Xiaoya Li, Jian Song, Kai Wang, Gequn Shu, Hua Tian, and Christos N. Markides. "Operational Optimisation of a Non-Recuperative 1-kWe Organic Rankine Cycle Engine Prototype." Applied Sciences 9, no. 15 (July 26, 2019): 3024. http://dx.doi.org/10.3390/app9153024.
Abstract:
Several heat-to-power conversion technologies are being proposed as suitable for waste-heat recovery (WHR) applications, including thermoelectric generators, hot-air (e.g., Ericsson or Stirling) engines and vapour-cycle engines such as steam or organic Rankine cycle (ORC) power systems. The latter technology has demonstrated the highest efficiencies at small and intermediate scales and low to medium heat-source temperatures and is considered a suitable option for WHR in relevant applications. However, ORC systems experience variations in performance at part-load or off-design conditions, which need to be predicted accurately by empirical or physics-based models if one is to assess accurately the techno-economic potential of such ORC-WHR solutions. This paper presents results from an experimental investigation of the part-load performance of a 1-kWe ORC engine, operated with R245fa as a working fluid, with the aim of producing high-fidelity steady-state and transient data relating to the operational performance of this system. The experimental apparatus is composed of a rotary-vane pump, brazed-plate evaporator and condenser units and a scroll expander magnetically coupled to a generator with an adjustable resistive load. An electric heater is used to provide a hot oil-stream to the evaporator, supplied at three different temperatures in the current study: 100, 120 and 140 ∘ C. The optimal operating conditions, that is, pump speed and expander load, are determined at various heat-source conditions, thus resulting in a total of 124 steady-state data points used to analyse the part-load performance of the engine. A maximum thermal efficiency of 4.2 ± 0.1% is reported for a heat-source temperature of 120 ∘ C, while a maximum net power output of 508 ± 2 W is obtained for a heat-source temperature at 140 ∘ C. For a 100- ∘ C heat source, a maximum exergy efficiency of 18.7 ± 0.3% is achieved. A detailed exergy analysis allows us to quantify the contribution of each component to the overall exergy destruction. The share of the evaporator, condenser and expander components are all significant for the three heat-source conditions, while the exergy destroyed in the pump is negligible by comparison (below 4%). The data can be used for the development and validation of advanced models capable of steady-state part-load and off-design performance predictions, as well as predictions of the transient/dynamic operation of ORC systems.
2
Bandaru, Sree Harsha, Victor Becerra, Sourav Khanna, Jovana Radulovic, David Hutchinson, and Rinat Khusainov. "A Review of Photovoltaic Thermal (PVT) Technology for Residential Applications: Performance Indicators, Progress, and Opportunities." Energies 14, no. 13 (June 26, 2021): 3853. http://dx.doi.org/10.3390/en14133853.
Abstract:
Solar energy has been one of the accessible and affordable renewable energy technologies for the last few decades. Photovoltaics and solar thermal collectors are mature technologies to harness solar energy. However, the efficiency of photovoltaics decays at increased operating temperatures, and solar thermal collectors suffer from low exergy. Furthermore, along with several financial, structural, technical and socio-cultural barriers, the limited shadow-free space on building rooftops has significantly affected the adoption of solar energy. Thus, Photovoltaic Thermal (PVT) collectors that combine the advantages of photovoltaic cells and solar thermal collector into a single system have been developed. This study gives an extensive review of different PVT systems for residential applications, their performance indicators, progress, limitations and research opportunities. The literature review indicated that PVT systems used air, water, bi-fluids, nanofluids, refrigerants and phase-change material as the cooling medium and are sometimes integrated with heat pumps and seasonal energy storage. The overall efficiency of a PVT system reached up to 81% depending upon the system design and environmental conditions, and there is generally a trade-off between thermal and electrical efficiency. The review also highlights future research prospects in areas such as materials for PVT collector design, long-term reliability experiments, multi-objective design optimisation, techno-exergo-economics and photovoltaic recycling.
3
Yan, Shilin, Minwei Zhao, Hongfu Zhang, Hongtao Zheng, and Fuquan Deng. "Theoretical Analysis on Thermodynamic and Economic Performance Improvement in a Supercritical CO2 Cycle by Integrating with Two Novel Double-Effect Absorption Reheat Power Cycles." International Journal of Energy Research 2024 (June 1, 2024): 1–24. http://dx.doi.org/10.1155/2024/3745897.
Abstract:
To enhance the overall performance of recompression supercritical carbon dioxide- (sCO2-) based systems, two new double-effect absorption reheat power cycles (DARPC) were developed in this study. These methods are based on the typical absorption power cycle (APC). For the proposed sCO2/DARPC systems, a parametric analysis of the thermodynamic and economic performances, as well as additional parametric optimisations, were performed quantitatively. The results indicate that replacing the APC subsystem with DARPC subsystems can enhance the total function of the sCO2 system even further, owing to the increased H2O vapour created in the separator and the reheating process, which adds to the greater net power output. Furthermore, compared to the DARPC2 subsystem, the DARPC1 subsystem may produce more H2O vapour from the generator and separator, resulting in an increase in net output power. When compared to a single sCO2 power cycle, multiobjective optimisations showed that the sCO2/DARPC1 and sCO2/DARPC2 systems could increase the exergy efficiency by 12.95% and 11.51% and decrease the total product unit cost by 9.67% and 8.37%, respectively. Furthermore, the sCO2/DARPC1 and sCO2/DARPC2 systems can achieve improvements in exergy efficiency of 4.95% and 3.61% and a total product unit cost of 4.52% and 3.15%, respectively, compared with the sCO2/APC system.
4
Piskin, A., T. Baklacioglu, O. Turan, and H. Aydin. "Modeling of Energy Efficiency of a Turboprop Engine using Ant Colony Optimisation." Aeronautical Journal 124, no. 1272 (October 30, 2019): 237–56. http://dx.doi.org/10.1017/aer.2019.134.
Abstract:
ABSTRACTExergy efficiency can be used as an objective function in order to improve systems efficiency. Thus, the most efficient regions for the operation parameters can be searched easily. Exergy efficiency data of a turboprop engine’s components that have been calculated using basic engine parameters in the previous studies are modeled using cubic spline curve fitting methodology. Spline curves are on the two dimensional plane, where x axis is the input parameter and y axis is the exergy efficiency of the component. A spline curve is defined by the points subject to arbitrary selection of number and position. Initially positions of the points are located with two different methods and then in order to obtain better accuracy point positions are improved by ‘Ant colony’ and ‘Goldsection’ optimisation methods. Sum of Squares of the errors between the fitted value and data value was used as the fitness function. Least square error of 5 × 10−9 is assumed as acceptable accuracy which yields to a minimum R = 0.9998 linear correlation coefficient. In the optimisation step, independent engine variable versus calculated engine performance parameters were checked against spline fitted values. Improvement of the fitness function is observed as the number of fitting points is increased. Ant colony optimisation in engine exergy efficiency parametric modeling is a new approach in authors’ point of view.
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Perdigão, José, and António Sarmento. "Overall-efficiency optimisation in OWC devices." Applied Ocean Research 25, no. 3 (June 2003): 157–66. http://dx.doi.org/10.1016/j.apor.2003.09.002.
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Abuel, Paul Mikii, Abir Hossain Mridul, and Wilson Fidelis Ekpotu. "Efficiency Assessment of a Combined Heat and Power Plant Using Exergy Analysis." Journal of Sustainable Development 17, no. 2 (February 8, 2024): 55. http://dx.doi.org/10.5539/jsd.v17n2p55.
Abstract:
This study conducted an exergy analysis of a cogeneration power plant utilizing gas turbines, air compressors, combustion chambers, heat recovery steam generators, heat exchangers, and pumps. The study performed an extensive exergy analysis of the system, focusing on each component's process and calculating its base efficiency while tabulating the corresponding exergy degradation. Relevant equations for mass, energy, and exergy were identified to determine optimal control volume conditions for an optimal system and boundary conditions that would enhance the design and reduce exergy destruction. The research project developed revisions and modifications necessary to the base system, utilizing available parameters and boundary conditions, to enable a second law analysis, improve the overall efficiency, and reduce irreversibility and the loss of exergy. The proposed modifications included the remodelling of the cogeneration plant by applying additional processes to utilize the excessive waste heat in the plant. The study further optimized the plant's efficiency by modifying individual system elements that yielded minimal exergy destruction to the overall design. The proposed modifications explored the best-case alteration on optimizing overall plant efficiency with minimum irreversibility compared to the initial analysis done. The technical contributions of this research project are the revisions and modifications that enabled a second law analysis and improved the overall efficiency of the cogeneration power plant.
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Guerrero-Martin, Camilo Andrés, Juan Sebastián Fernández-Ramírez, Jaime Eduardo Arturo-Calvache, Harvey Andrés Milquez-Sanabria, Fernando Antonio da Silva Fernandes, Vando José Costa Gomes, Wanessa Lima e Silva, Emanuele Dutra Valente Duarte, Laura Estefanía Guerrero-Martin, and Elizabete Fernandes Lucas. "Exergy Load Distribution Analysis Applied to the Dehydration of Ethanol by Extractive Distillation." Energies 16, no. 8 (April 18, 2023): 3502. http://dx.doi.org/10.3390/en16083502.
Abstract:
This study presents the analysis of the exergy load distribution in a separation process by extractive distillation for ethanol dehydration. The methodology carried out is divided into three parts: the calculation of the flow exergy considering the physical and chemical exergies of the distillation process; the calculation of the primary and transformed exergy contributions considering the consumed exergy; and finally, the overall process efficiency, which shows the real percentage of energy being used in the process. The simulation of an extractive distillation separation system is carried out using Aspen Plus®, from Aspen Tech Version 9. In general, heat transfer processes (heating or cooling) are the ones that generate the greatest exegetic destruction, which is why they must be the operations that must be optimized. As a result of our case study, the local exergy efficiency of the extractive distillation column is 13.80%, which is the operation with the greatest energy loss, and the overall exergy efficiency of the separation system is 30.67%. Then, in order to increase exergy efficiency, a sensitivity analysis is performed with the variation of the azeotrope feed, number of stages, reflux ratio, and solvent feed variation on ethanol purity to reach an overall efficiency of 33.53%. The purity of ethanol is classified as higher than that of the specified, 99.65%.
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Malaine, Salek, Mohamed Charia, Najib Ababssi, Jilali Dardouch, and Abdellah Boulal. "Advanced exergetic study to assess the effects of rectification and distillation on absorption refrigerators." Thermal Science, no. 00 (2022): 147. http://dx.doi.org/10.2298/tsci220402147m.
Abstract:
In this paper, an advanced exergetic study is carried out to improve the exergy efficiency and minimize the exergy losses of an absorption refrigerator. Two thermal processes based on rectification and distillation were proposed to meet this critical requirement. A numerical simulation model was established in the FORTRAN language, building on the analytical Gibbs free energy equations. This model was validated from a thermodynamic point of view by previously published results. Preliminary results showed that when the efficiency of the absorber and boiler is increased, the vapors produced by the boiler become enriched in ammonia, and the overall exergy efficiency increases, which reduces considerably the irreversibility of the components of the studied absorption system. A comparative study of the effect of these two thermal processes on the overall exergy efficiency and total exergy losses was evaluated simultaneously. The results show that the refrigerator with a distiller has a higher exergy efficiency (?ex=24.37 % at 86?C), and at the same time has a lower total exergy loss ( =457.45 kW) than the refrigerator with a rectifier (?ex=22.34 % at 85?C; =532.37 kW). This study reveals that the distillation process can contribute more to the exergy improvement and exergy loss minimization of the studied absorption refrigerator than the rectification process.
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Ponnusamy, Sathyakala, Sundara Sai Gangadharan, and Balaji Kalaiarasu. "An exergy analysis for overall hidden losses of energy in solar water heater." Thermal Science, no. 00 (2020): 343. http://dx.doi.org/10.2298/tsci200530343p.
Abstract:
This study investigates the hidden thermal losses of glass plate, collector plate, water pipe and storage tank of solar water heater in the process of energy conversion. The present non-conventional energy methods are insufficient, whereas the exergy analysis provides a remarkable solution. Thus, employing the exergy analysis, entropy generation, exergy destruction and exergy efficiency of each subsystem of solar water heater are computed. The obtained results showed that the entropy generation and exergy destruction are high during the heat transfer in each subsystem. Henceforth, the existing solar water heater design is modified placing hexagonal honeycomb structure between the glass plate and the collector plate and also water pipe is insulated to trap huge amount of solar energy. The proposed design exhibits improved exergy efficiency when compared with the existing model, which enhances the performance of the system.
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Srimanickam, B., M. M. Vijayalakshmi, and Elumalai Natarajan. "Experimental Study of Exergy Analysis on Flat Plate Solar Photovoltaic Thermal (PV/T) Hybrid System." Applied Mechanics and Materials 787 (August 2015): 82–87. http://dx.doi.org/10.4028/www.scientific.net/amm.787.82.
Abstract:
The objective of present study is to conduct exergy analysis on flat plate solar photovoltaic thermal (PV/T) hybrid system. The solar insolation, current, voltage, inlet and outlet air temperature of the cooling duct, ambient air temperature, and solar panel surface temperature are the major parameters used to calculate the energy and exergy efficiency. An amended electrical efficiency is used to estimate the electrical output and performance of PV/T hybrid system. Further, an enriched equation for the exergy efficiency of a PV/T hybrid system has been used for exergy analysis. Finally, parametric studies have been carried out. An extensive energy and exergy analysis is carried out to calculate the electrical and thermal parameters. The experimental results are in good agreement with the earlier studies. In addition to that, the electrical efficiency, thermal efficiency, electrical thermal efficiency, overall energy efficiency and exergy efficiency of PV/T hybrid system is found to be about 9.78%, 24.22%, 27.17%, 44.84% and 11.23% respectively.
Dissertations / Theses on the topic "Overall exergy efficiency, Optimisation":
1
Das, Barun Kumar. "Optimisation of stand-alone hybrid energy systems for power and thermal loads." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2018. https://ro.ecu.edu.au/theses/2150.
Abstract:
Stand-alone hybrid energy systems are an attractive option for remote communities without a connection to a main power grid. However, the intermittent nature of solar and other renewable sources adversely affects the reliability with which these systems respond to load demands. Hybridisation, achieved by combining renewables with combustion-based supplementary prime movers, improves the ability to meet electric load requirements. In addition, the waste heat generated from backup Internal Combustion Engines or Micro Gas Turbines can be used to satisfy local heating and cooling loads. As a result, there is an expectation that the overall efficiency and Greenhouse Gas Emissions of stand-alone systems can be significantly improved through waste heat recovery.
The aims of this PhD project are to identify how incremental increases to the hardware complexity of hybridised stand-alone energy systems affect their cost, efficiency, and CO2 footprint. The research analyses a range of systems, from those designed to meet only power requirements to others satisfying power and heating (Combined Heat and Power), or power plus both heating and cooling (Combined Cooling, Heating, and Power). The majority of methods used focus on MATLAB-based Genetic Algorithms (GAs). The modelling deployed finds the optimal selection of hardware configurations which satisfy single- or multi-objective functions (i.e. Cost of Energy, energy efficiency, and exergy efficiency). This is done in the context of highly dynamic meteorological (e.g. solar irradiation) and load data (i.e. electric, heating, and cooling).
Results indicate that the type of supplementary prime movers (ICEs or MGT) and their minimum starting thresholds have insignificant effects on COE but have some effects on Renewable Penetration (RP), Life Cycle Emissions (LCE), CO2 emissions, and waste heat generation when the system is sized meeting electric load only. However, the transient start-up time of supplementary prime movers and temporal resolution have no significant effects on sizing optimisation. The type of Power Management Strategies (Following Electric Load-FEL, and Following Electric and Following Thermal Load- FEL/FTL) affect overall Combined Heating and Power (CHP) efficiency and meeting thermal demand through recovered heat for a system meeting electric and heating load with response to a specific load meeting reliability (Loss of Power Supply Probability-LPSP). However, the PMS has marginal effects on COE. The Electric to Thermal Load Ratio (ETLR) has no effects on COE for PV/Batt/ICE but strongly affects PV/Batt/MGT-based hybridised CHP systems. The higher thermal than the electric loads lead to higher efficiency and better environmental footprint.
Results from this study also indicate that for a stand-alone hybridised system operating under FEL/FTL type PMS, the power only system has lower cost compared to the CHP and the Combined Cooling, Heating, and Power (CCHP) systems. This occurs at the expense of overall energy and exergy efficiencies. Additionally, the relative magnitude of heating and cooling loads have insignificant effects on COE for PV/Batt/ICE-based system configurations, however this substantially affects PV/Batt/MGT-based hybridised CCHP systems. Although there are no significant changes in the overall energy efficiency of CCHP systems in relation to variations to heating and cooling loads, systems with higher heating demand than cooling demand lead to better environmental benefits and renewable penetration at the cost of Duty Factor. Results also reveal that the choice of objective functions do not affect the system optimisation significantly.
2
Brenner, Lorenz. "Exergy-based performance assessment and optimization potential of refrigeration plants in air-conditioning applications." Thesis, Lyon, 2021. http://www.theses.fr/2021LYSEI014.
Abstract:
Une grande partie de la consommation d'énergie dans les bâtiments est due aux systèmes de chauffage, de ventilation et de climatisation. Entre autres systèmes, les systèmes de réfrigération font l'objet de mesures d'amélioration de l'efficacité. Néanmoins, les conditions opérationnelles réelles de ces installations et leurs performances doivent être connues, ainsi que tout potentiel d'optimisation éventuel, avant que des améliorations puissent être réalisées. Les analyses exergétique et énergétiques ont été largement utilisées pour évaluer la performance des systèmes de réfrigération. Entre autres, l'efficacité exergétique est utilisée comme indicateur pour déterminer la performance du système, mais les valeurs réalisables dans la pratique sont inconnues. Par conséquence, ce travail propose une méthode d'évaluation pratique des systèmes de réfrigération basée sur une analyse exergétique et des normes techniques comme base de référence. L'identification des améliorations possibles est pertinente dans la pratique, car les mesures qui améliorent l'efficacité du système permettent probablement d'éviter de fréquentes déficiences pendant l'usage. Avec l'optimization potential index (OPI) introduit dans cet ouvrage, les améliorations réalisables par rapport à l'état de l'art de la technologie et la performance sont identifiées d'un seul coup d’œil, quelle que soit la complexité du système. En divisant l'installation en sous-systèmes, chacun peut être évalué individuellement. Les non-spécialistes peuvent facilement déterminer l'état de fonctionnement du système et ensuite, si nécessaire, lancer une analyse détaillée ainsi que des contre-mesures appropriées. De plus, la modélisation est considérée comme une méthode appropriée pour déterminer des valeurs de référence. Parmi les différentes techniques, les modèles artificial neural network révèlent les meilleures performances pour l'application présentée. L'application, la fonctionnalité et l'objectif de la méthode présentée sont illustrés par deux cas numériques et sur une installation réelle. La recherche révèle un fonctionnement approprié de l'installation étudiée en général, où trois des sept espaces conditionnés ont des problèmes de performance. La raison devrait être identifiée dans une étude détaillée ultérieure. Dans l'ensemble, l'apport d'exergie électrique auxiliaire est du même ordre que l'apport d'exergie thermique. Cela souligne l'importance de réduire la consommation d'énergie électrique au minimum, car elle constitue le facteur principal dans le coût d'exploitation des installations de réfrigération et permet également d'augmenter la performance du système. En outre, les concepts de mesure des systèmes réels sont analysés et les coûts de mise à jour correspondants pour l'application de l'approche présentée sont identifiés. Il est démontré qu'une mise à jour de l'instrumentation peut être rentable, si l'installation frigorifique comprend déjà un concept de mesure proche de l'état de la artA significant amount of energy consumption in buildings is due to heating, ventilation and air-conditioning systems. Among other systems, refrigeration plants are subject of efficiency improvements. However, actual operating conditions of such plants and the performance must be known as well as any eventual optimization potential identified before enhancements can take place. Energy and exergy analyses have been widely used to assess the performance of refrigeration systems. Among others, exergy efficiency is used as an indicator to determine the system performance; however, the practical achievable values are unknown. Therefore, this work proposes a practice-oriented evaluation method for refrigeration plants, based on exergy analysis and technical standards as baseline. The identification of possible enhancements is highly relevant in practice, as measures which improve the system effectiveness most likely prevent frequent shortcomings during refrigeration plant operation. With the introduced optimization potential index (OPI), the achievable enhancements compared to the state of the art in technology and the performance are identified at a glance regardless the complexity of the system. By dividing the plant into different subsystems, each of them can be assessed individually. Laypersons can easily determine the system operating state and subsequently, if needed, initiate a detailed analysis as well as appropriate countermeasures by specialist. Moreover, modeling is seen as an appropriate method to determine additional reference values for refrigeration machines if none are available according to technical standards. Among different modeling techniques, artificial neural network models reveal the best performance for the present application. The application, functionality and purpose of the presented method is exemplified on two numerical test cases and on a real field plant as a case study. The investigation reveals an adequate operation of the studied field plant in general, where three out of seven cooling locations have performance issues. The reason should be identified in a subsequent detailed study. Overall, the auxiliary electrical exergy input shows the same magnitude as the thermal exergy input. This emphasizes the importance of minimizing the electrical energy usage, as it is the main overhead in the operating cost of refrigeration plants and also to achieve an increase in system performance. Moreover, measuring concepts of real systems are analyzed and the corresponding retrofitting costs for the application of the presented approach are identified. It is shown that a retrofit of the instrumentation can be worthwhile if the refrigeration plant already comprises a measuring concept close to the state of the art
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Le, Van Long. "Étude de la faisabilité des cycles sous-critiques et supercritiques de Rankine pour la valorisation de rejets thermiques." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0117/document.
Abstract:
Ce travail de thèse concerne l’étude de la faisabilité des cycles organiques sous-critiques et supercritiques de Rankine pour la valorisation de rejets thermiques industriels à basse température. Dans un premier temps, un état de l’art des cycles ORC (acronyme anglais pour Organic Rankine Cycle) et leurs fluides de travail a été réalisé. Nous avons réalisé une comparaison préliminaire de plusieurs configurations à partir de la littérature scientifique. Dans un second temps, les méthodes d’analyse énergétique et exergétique ont été appliquées pour évaluer et optimiser les performances des cycles ORC. En effet, la seule méthode d’analyse énergétique n’est pas suffisante pour juger de la bonne utilisation du potentiel énergétique de la source de chaleur disponible correspondant à un rejet industrielle de chaleur (chaleur fatale). L’analyse exergétique, intervient en complément de l’analyse énergétique du système, afin de permettre de localiser les pertes des ressources énergétiques dans les différentes composantes du système et de déterminer leurs importances relatives et leurs causes. Une optimisation thermo-économique des installations de valorisation de rejets thermiques utilisant un cycle sous-critique ou supercritique de Rankine a été effectuée. Nos résultats montrent que la valorisation de rejets thermiques industriels à basse température (ex. source thermique de 150 °C) en utilisant un cycle ORC sous-critique est plus intéressante sur le plan énergétique que celle opérée en utilisant un cycle supercritique de RankineThis thesis concerns the feasibility study of subcritical and supercritical organic Rankine cycles for industrial waste heat recovery at relatively low temperature. Initially, a state of the art of ORCs (Organic Rankine Cycles) and their working fluids has been achieved. We conducted a preliminary comparison of several configurations from the scientific literature. In a second step, methods of energy and exergy analysis were applied to evaluate and optimize the performance of the ORCs. Indeed, sole energy analysis is not enough to access the proper use of the energy potential of the available heat source that corresponds to an industrial waste heat. Exergy analysis, in a complementary way to the energy analysis, enables us to locate the energy resources losses in the various components of the system and to determine their true magnitude and their causes. A thermo-economic optimization of waste heat recovery systems using a subcritical or supercritical Rankine cycle has been performed. According to the results, the industrial waste heat recovery at low temperature (e.g. heat source 150 ° C) using a subcritical ORC is more interesting on economic point of view than the system using a supercritical Rankine cycle
Books on the topic "Overall exergy efficiency, Optimisation":
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Desideri, Umberto, Giampaolo Manfrida, and Enrico Sciubba, eds. ECOS 2012. Florence: Firenze University Press, 2012. http://dx.doi.org/10.36253/978-88-6655-322-9.
Abstract:
The 8-volume set contains the Proceedings of the 25th ECOS 2012 International Conference, Perugia, Italy, June 26th to June 29th, 2012. ECOS is an acronym for Efficiency, Cost, Optimization and Simulation (of energy conversion systems and processes), summarizing the topics covered in ECOS: Thermodynamics, Heat and Mass Transfer, Exergy and Second Law Analysis, Process Integration and Heat Exchanger Networks, Fluid Dynamics and Power Plant Components, Fuel Cells, Simulation of Energy Conversion Systems, Renewable Energies, Thermo-Economic Analysis and Optimisation, Combustion, Chemical Reactors, Carbon Capture and Sequestration, Building/Urban/Complex Energy Systems, Water Desalination and Use of Water Resources, Energy Systems- Environmental and Sustainability Issues, System Operation/ Control/Diagnosis and Prognosis, Industrial Ecology.
Book chapters on the topic "Overall exergy efficiency, Optimisation":
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Shboul, Bashar, Ismail Al-Arfi, Stavros Michailos, Derek Ingham, Godfrey T. Udeh, Lin Ma, Kevin Hughes, and Mohamed Pourkashanian. "Multi-Objective Optimal Performance of a Hybrid CPSD-SE/HWT System for Microgrid Power Generation." In Applications of Nature-Inspired Computing in Renewable Energy Systems, 166–210. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-7998-8561-0.ch009.
Abstract:
A new integrated hybrid solar thermal and wind-based microgrid power system is proposed. It consists of a concentrated parabolic solar dish Stirling engine, a wind turbine, and a battery bank. The electrical power curtailment is diminished, and the levelised cost of energy is significantly reduced. To achieve these goals, the present study conducts a dynamic performance analysis over one year of operation. Further, a multi-objective optimisation model based on a genetic algorithm is implemented to optimise the techno-economic performance. The MATLAB/Simulink® software was used to model the system, study the performance under various operating conditions, and optimise the proposed hybrid system. Finally, the model has been implemented for a specific case study in Mafraq, Jordan. The system satisfies a net power output of 1500 kWe. The developed model has been validated using published results. In conclusion, the obtained results reveal that the optimised model of the microgrid can substantially improve the overall efficiency and reduce the levelised cost of electricity.
2
Akinmulewo, Daniel, Ginevra Rubino, Roland Gosda, Moustafa Abdel-Maksoud, and Henning Grashorn. "Numerical Investigation of the Influence of the Axial Position of the Propeller on the Propulsion Performance and the Hull-Propeller Interaction Using the Body-Force-Method." In Progress in Marine Science and Technology. IOS Press, 2023. http://dx.doi.org/10.3233/pmst230033.
Abstract:
The growing demand to reduce emissions and the increasing awareness of the negative environmental impact of ships and high-speed marine vessels have influenced the traditional methods employed in the design of ship propulsion systems. In this context, more emphasis has been placed on the design of ship propellers and determining the optimum axial position, while operating in the ship wake-field. The interaction parameters between the hull and propeller, mainly the wake fraction coefficient and thrust deduction factor, are required to determine the optimum propeller position for improved fuel and overall propulsive efficiency. For this purpose, a numerical analysis is performed to assess the influence of the axial position of the propeller on the propulsion performance and the hull-propeller interaction using the integration of three software: a propeller design and optimisation framework within the CAESES environment for a parametric variation of the propeller geometry, a CFD code FreSCo+, a joint development from the Hamburg Ship Model Basin (HSVA) and Hamburg University of Technology (TUHH) to perform the hydrodynamic evaluation of the hull and a propeller potential solver QCM (HSVA in house code). The coupling of the above procedure is applied to four axial positions of the propeller in calm water conditions without considering cavitation aspects to evaluate propeller-induced forces and hull-propeller interaction coefficients. Simulations are performed on a model-scale container ship and validated with the experimental results from HSVA.
Conference papers on the topic "Overall exergy efficiency, Optimisation":
1
Codeceira Neto, Alcides, and Pericles Pilidis. "An Assessment Method of Power Plants Using Genetic Algorithms." In ASME Turbo Expo 2001: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/2001-gt-0560.
Abstract:
The performance assessment of power plants is a complex task, which involves many calculations. Increasing the number of plant components with the introduction of new technologies available in the international market, it increases the complexity of performance analysis of power cycles. The present paper describes a process for optimising a conventional gas turbine combined cycle power plant. In this paper the method of assessing thermal power plants takes into account the exergy method and carries out along with optimisation of the whole plant based on maximising overall plant exergetic efficiency and minimising energy loss rejected to the atmosphere. The performance assessment of power plants using the exergy method considers the overall plant exergetic efficiency and the exergy destruction in the various components of the plant. The exergy method highlights irreversibility within the plant components, and it is of particular interest in this investigation. Due to the large number of equations with many variables taking part in the whole calculation and also considering constraints imposed to some variables, a genetic algorithm is recommended as the optimisation tool for the assessment method. Genetic Algorithms are adaptive methods which may be used to solve search and optimisation problems. They are based on the genetic processes of biological organisms. Over many generations, natural populations evolve according to the principles of natural selection and “survival of the fittest”, first clearly stated by Charles Darwin in his book “The Origin of Species”. Genetic algorithms do not require complicate mathematical calculations like the evaluation of derivatives necessary to be considered in conventional optimisation techniques.
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Codeceira Neto, Alcides, Pericles Pilidis, and Anestis I. Kalfas. "An Economic Assessment Method of Gas Turbine Power Cycles by Means of Genetic Algorithms." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-54069.
Abstract:
The Performance assessment of power plants involves a large number of equations with many variables taking part in the whole calculation. The assessment method described here takes into account a process for optimising a conventional gas turbine combined cycle power plant from the point of view of power plant performance calculations and economic analysis. The process requires optimisation of the whole thermal power plant based on cost considerations. The performance assessment of power plants uses the exergy method and considers the overall plant exergetic efficiency and the exergy destruction in the various components of the plant. The exergy method highlights irreversibility within plant components, and it is of particular interest in this investigation. Generally, the optimisation procedure to determine an optimal solution for a problem considers constraints imposed to some variables and requires the use of an optimisation technique. This paper is precisely concerned with the use of Genetic Algorithms (GAs) as a recommended tool for applying the optimisation process of the whole power plant based on minimising costs of products. Genetic Algorithms (GAs) are adaptive methods which may be used to solve search and optimisation problems. They are based on the genetic processes of biological organisms and do not require complicated mathematical calculations like the evaluation of derivatives necessary to be considered in conventional optimisation techniques.
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van Berlo, M. A. J., and Harry de Waart. "Unleashing the Power in Waste: Comparison of Greenhouse Gas and Other Performance Indicators for Waste-to-Energy Concepts and Landfilling." In 16th Annual North American Waste-to-Energy Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/nawtec16-1937.
Abstract:
A CO2-evaluation is made for landfill and Waste-to-Energy (WtE) concepts. Different concepts are identified and compared for their performance on energy and materials recovery. Performance indicators for WtE are compared; like energy efficiency, EXergy efficiency, the R1-D10 formula from the EU Waste Framework directive, and CO2-emission and avoidance. It is shown that, due to the biomass content and the avoidance effect due to the recovery of energy and materials, conventional WtE has a near zero CO2-emission per ton of waste. Optimised WtE can have a significant negative overall emission of 200–300 kgCO2/ton of waste. This means an absolute net avoidance of CO2 by WtE. The reduction relative to land filling is as much as 500–1200 kgCO2/ton of waste. The potential for optimisation of the energy recovery as well as the material recovery of the WtE infrastructure is demonstrated. If WtE is evaluated as a power plant, an optimised plant can have an emission of only 0,336 kgCO2/kWh, lower than a gas fired electrical power plant, and this absolute figure does not include the avoided landfill emissions. With CHP this can be reduced even further. The actual potential of electricity production from WtE for the EU-15 is calculated to be over 7,5% of total electricity production. Additionally heat and the metal recoveries could be doubled.
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Rosen, Marc A. "Impact on Overall Efficiency of Component Efficiency Increases for an Existing Thermal Electrical Generating Station." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33149.
Abstract:
Most electrical generating utilities are striving to improve the efficiencies of their existing thermal electric generating stations, many of which are old. Exergy methods have been shown to provide meaningful insights that can assist in increasing the efficiency of conventional coal-to-electricity technologies. Here, exergy analysis is used to assess measures for improving the efficiencies of coal-fired electrical generating stations. This scope of the study is limited to minor practical improvements, which can be undertaken with limited effort and cost and are not overly complex. The plant considered is the coal-fired Nanticoke Generating Station (GS) in Ontario, Canada. The findings suggest that the results of exergy analyses should be used, along with other pertinent information, to guide efficiency improvement efforts for thermal generating stations. Also, efficiency improvement efforts should focus on plant components responsible for the largest exergy losses: the steam generator (where large losses occur from combustion heat transfer across large temperature differences), the turbines, the electrical generator and the transformer. Possible improvements in these areas should be assessed in conjunction with other criteria, and other components should be considered where economically beneficial improvements can be identified.
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Rosen, M. A., and M. N. Le. "Efficiency Analysis of a Process Design Integrating Cogeneration and District Energy." In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0306.
Abstract:
Abstract An efficiency analysis, accounting for both energy and exergy considerations, is reported of a design for cogeneration-based district energy proposed for the city of Edmonton, Canada, by the utility Edmonton Power. The original concept using central electric chillers, as well as two variations (one considering single-effect and the other double-effect absorption chillers), are examined. The energy- and exergy-based results differ markedly (e.g., overall energy efficiencies are shown to vary for the three configurations considered from 83 to 94%, and exergy efficiencies from 28 to 29%). For the overall processes, as well as individual subprocesses and selected combinations of subprocesses, the exergy efficiencies are generally found to be more meaningful and indicative of system behaviour than the energy efficiencies.
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Hossain, Mohammad A., Md Taibur Rahman, Mohammad Ikthair Hossain Soiket, and Sarzina Hossain. "Investigation and Improvement of Thermal Efficiency of Hypersonic Scramjet." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37385.
Abstract:
This work is focused on investigation of thermal efficiency of a Hypersonic scramjet engine and propose some improvement of thermal efficiency based on thermodynamic and fluid flow analysis. Thermal management system is one of the main research fields in scramjet design. As it has no moving parts, the total thermal efficiency depends on inlet conditions, conditions of combustor exit and conditions of the engine exit. A combustor exit condition dictates the velocity and temperature after combustion. we concentrate our focus on this section. The first part of the paper, we tried to describe the fundamental exergy relationship for scramjet and we developed the relation of exergy distribution and exergy delivery rate. From an extensive literature review, we have found the relations between fluid velocity, pressure and temperature, which is described in the later part of the paper. Our main focus is to develop a combined relation of thermal efficiency in terms of engine exit velocity, temperature and air-fuel ratio. Different characteristic parameters such as overall efficiency, thermal efficiency, specific impulse have been determined at different inlet temperature ratio or the cycle static temperature ratio (T3/T0) and an optimum inlet temperature ratio is proposed for maximum overall efficiency.
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Horlock, J. H. "The Effect of Heat Exchanger Effectiveness and Exergy Loss in the Estimation of Cycle Efficiency." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-352.
Abstract:
The effect of heat exchanger effectiveness on cycle efficiency is well known. But the relationship between exergy loss in heat exchangers and the effectiveness is less well documented. In this paper the relationship is explored; it is shown how the exergy loss in the heat exchanger is changed as effectiveness is altered. It is also shown how the exergy losses in other components of the recuperative gas turbine cycle are changed, together with the overall cycle performance, as the effectiveness is varied.
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Cheremnykh, Ekaterina, and Fabio Gori. "Exergy and Extended Exergy Cost Assessment of a Commercial Truck." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-37860.
Abstract:
To gain a clearer understanding of the overall economic and environmental impact of the manufacturing process of a single vehicle, including its operational phase, it is useful to examine the process in a life-cycle perspective and with an exergy approach.. The method of Extended Exergy Accounting (EEA) has already provided reliable results both for the assessment of entire countries and for the analysis of specific industrial sectors. National transportation sectors, generally reputed inefficient, have been the subject of a series of energy and exergy efficiency studies, though so far the phase of vehicle manufacturing was not specifically addressed. The present study is an attempt to quantitatively develop the complex evaluation of the exergy cost of a single vehicle, in particular of a commercial truck produced in the US (for which the available data are extensive and reliable). In the analysis performed in the course of this study, the last version of EEA has been employed, with the latest available data on the allocation coefficients for labour and capital cost factors. Particular attention is given to data selection and their processing. The values of the exergy costs for materials flows, energy inputs and of their equivalents for capital, labour and environment remediation are predicted. The results shows numerically the exergetic costs of economic, labour, material and energy inputs, and emphasize the further research of environmental remediation costs.
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Chow, Raymond, George J. Nelson, and Jay L. Perry. "Electrolyzer Exergy Analysis for an Environmental Control and Life Support System." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88119.
Abstract:
An exergy based analysis of the Environmental Control and Life Support System (ECLSS) aboard the International Space Station (ISS) is conducted to assess its overall performance. Exergy is chosen as a measure of performance because it accounts for both the first and second laws of thermodynamics. The exergy efficiency of a system is first defined as the total exergy destroyed by the system relative to the total exergy input to the system. To determine the ECLSS exergy efficiency, the system is divided into constituent subsystems which in turn are divided into assemblies and components. Based on this system decomposition, exergy balances are derived for each assembly or component. Exergy balances and supporting calculations are implemented in MATLAB® code. The major subsystems of the ECLSS considered in this analysis include the Atmosphere Revitalization Subsystem (ARS), Atmosphere Control and Supply Subsystem (ACS), Temperature and Humidity Control Subsystem (THC), Water Recovery and Management Subsystem (WRM), and Waste Management Subsystem (WM). This paper focuses on the ARS and its constituent assemblies and components. Exergy efficiency of the ARS and its constituent assemblies and components is first presented. The Oxygen Generation Assembly (OGA), an assembly within the ARS, is then highlighted because the exergy destruction by the OGA is a large magnitude contributor to the overall exergy destruction of the ECLSS. The OGA produces oxygen to meet the crew’s metabolic demand via water electrolysis in a proton exchange membrane (PEM) electrolyzer. The exergy destruction of the OGA’s PEM electrolyzer is a function of the amount of oxygen produced, which determines the necessary current density and voltage drop across the PEM electrolyzer. In addition, oxygen production in the PEM electrolyzer requires deviation from the Nernst potential, presenting trade-offs between the exergy efficiency and critical life support functions. The results of parametric studies of PEM electrolyzer performance are presented with an emphasis on the impacts of polarization and operational conditions on exergy efficiency.
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Yilanci, Ahmet, Ibrahim Dincer, and Harun Kemal Ozturk. "Determination of Some Thermodynamic Parameters for a Hybrid Solar-Hydrogen System." In ASME 2008 2nd International Conference on Energy Sustainability collocated with the Heat Transfer, Fluids Engineering, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/es2008-54342.
Abstract:
In this paper, we undertake a study to investigate the performance of a hybrid photovoltaic-hydrogen system through energy and exergy efficiencies, improvement potential. This will help identify the irreversibilities (exergy destructions) for performance improvement purposes. Energetic and exergetic renewability ratios are also introduced for grid dependent hybrid energy systems. A case study is presented to highlight the importance of the thermodynamic parameters and show them using some actual and theoretical data. Three different energy demand options from photovoltaic panels to the consumer are identified and considered for the analysis. The minimum and maximum overall energy and exergy efficiencies of the system are calculated based on these options. It is found that the overall energy efficiency values of the system vary between 0.88% and 9.7% while minimum and maximum overall exergy efficiency values of the system are 0.77% and 9.3%, respectively. The monthly improvement potential of the system is also studied to investigate the seasonal performance.