Performance Improvement Options for the Supercritical Carbon Dioxide Brayton Cycle PDF Download
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Languages : en
Pages :
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Book Description
The supercritical carbon dioxide (S-CO2) Brayton cycle is under development at Argonne National Laboratory as an advanced power conversion technology for Sodium-Cooled Fast Reactors (SFRs) as well as other Generation IV advanced reactors as an alternative to the traditional Rankine steam cycle. For SFRs, the S-CO2 Brayton cycle eliminates the need to consider sodium-water reactions in the licensing and safety evaluation, reduces the capital cost of the SFR plant, and increases the SFR plant efficiency. Even though the S-CO2 cycle has been under development for some time and optimal sets of operating parameters have been determined, those earlier development and optimization studies have largely been directed at applications to other systems such as gas-cooled reactors which have higher operating temperatures than SFRs. In addition, little analysis has been carried out to investigate cycle configurations deviating from the selected 'recompression' S-CO2 cycle configuration. In this work, several possible ways to improve S-CO2 cycle performance for SFR applications have been identified and analyzed. One set of options incorporates optimization approaches investigated previously, such as variations in the maximum and minimum cycle pressure and minimum cycle temperature, as well as a tradeoff between the component sizes and the cycle performance. In addition, the present investigation also covers options which have received little or no attention in the previous studies. Specific options include a 'multiple-recompression' cycle configuration, intercooling and reheating, as well as liquid-phase CO2 compression (pumping) either by CO2 condensation or by a direct transition from the supercritical to the liquid phase. Some of the options considered did not improve the cycle efficiency as could be anticipated beforehand. Those options include: a double recompression cycle, intercooling between the compressor stages, and reheating between the turbine stages. Analyses carried out as part of the current investigation confirm the possibilities of improving the cycle efficiency that have been identified in previous investigations. The options in this group include: increasing the heat exchanger and turbomachinery sizes, raising of the cycle high end pressure (although the improvement potential of this option is very limited), and optimization of the low end temperature and/or pressure to operate as close to the (pseudo) critical point as possible. Analyses carried out for the present investigation show that significant cycle performance improvement can sometimes be realized if the cycle operates below the critical temperature at its low end. Such operation, however, requires the availability of a heat sink with a temperature lower than 30 C for which applicability of this configuration is dependent upon the climate conditions where the plant is constructed (i.e., potential performance improvements are site specific). Overall, it is shown that the S-CO2 Brayton cycle efficiency can potentially be increased to 45 %, if a low temperature heat sink is available and incorporation of larger components (e.g., heat exchangers or turbomachinery) having greater component efficiencies does not significantly increase the overall plant cost.
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Languages : en
Pages :
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Book Description
The supercritical carbon dioxide (S-CO2) Brayton cycle is under development at Argonne National Laboratory as an advanced power conversion technology for Sodium-Cooled Fast Reactors (SFRs) as well as other Generation IV advanced reactors as an alternative to the traditional Rankine steam cycle. For SFRs, the S-CO2 Brayton cycle eliminates the need to consider sodium-water reactions in the licensing and safety evaluation, reduces the capital cost of the SFR plant, and increases the SFR plant efficiency. Even though the S-CO2 cycle has been under development for some time and optimal sets of operating parameters have been determined, those earlier development and optimization studies have largely been directed at applications to other systems such as gas-cooled reactors which have higher operating temperatures than SFRs. In addition, little analysis has been carried out to investigate cycle configurations deviating from the selected 'recompression' S-CO2 cycle configuration. In this work, several possible ways to improve S-CO2 cycle performance for SFR applications have been identified and analyzed. One set of options incorporates optimization approaches investigated previously, such as variations in the maximum and minimum cycle pressure and minimum cycle temperature, as well as a tradeoff between the component sizes and the cycle performance. In addition, the present investigation also covers options which have received little or no attention in the previous studies. Specific options include a 'multiple-recompression' cycle configuration, intercooling and reheating, as well as liquid-phase CO2 compression (pumping) either by CO2 condensation or by a direct transition from the supercritical to the liquid phase. Some of the options considered did not improve the cycle efficiency as could be anticipated beforehand. Those options include: a double recompression cycle, intercooling between the compressor stages, and reheating between the turbine stages. Analyses carried out as part of the current investigation confirm the possibilities of improving the cycle efficiency that have been identified in previous investigations. The options in this group include: increasing the heat exchanger and turbomachinery sizes, raising of the cycle high end pressure (although the improvement potential of this option is very limited), and optimization of the low end temperature and/or pressure to operate as close to the (pseudo) critical point as possible. Analyses carried out for the present investigation show that significant cycle performance improvement can sometimes be realized if the cycle operates below the critical temperature at its low end. Such operation, however, requires the availability of a heat sink with a temperature lower than 30 C for which applicability of this configuration is dependent upon the climate conditions where the plant is constructed (i.e., potential performance improvements are site specific). Overall, it is shown that the S-CO2 Brayton cycle efficiency can potentially be increased to 45 %, if a low temperature heat sink is available and incorporation of larger components (e.g., heat exchangers or turbomachinery) having greater component efficiencies does not significantly increase the overall plant cost.
Author: Klaus Brun
Publisher: Woodhead Publishing
ISBN: 0081008058
Category : Technology & Engineering
Languages : en
Pages : 464
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Book Description
Fundamentals and Applications of Supercritical Carbon Dioxide (SCO2) Based Power Cycles aims to provide engineers and researchers with an authoritative overview of research and technology in this area. Part One introduces the technology and reviews the properties of SCO2 relevant to power cycles. Other sections of the book address components for SCO2 power cycles, such as turbomachinery expanders, compressors, recuperators, and design challenges, such as the need for high-temperature materials. Chapters on key applications, including waste heat, nuclear power, fossil energy, geothermal and concentrated solar power are also included. The final section addresses major international research programs. Readers will learn about the attractive features of SC02 power cycles, which include a lower capital cost potential than the traditional cycle, and the compounding performance benefits from a more efficient thermodynamic cycle on balance of plant requirements, fuel use, and emissions. Represents the first book to focus exclusively on SC02 power cycles Contains detailed coverage of cycle fundamentals, key components, and design challenges Addresses the wide range of applications of SC02 power cycles, from more efficient electricity generation, to ship propulsion
Author: Vaclav Dostal
Publisher:
ISBN:
Category :
Languages : en
Pages : 317
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Book Description
A systematic, detailed major component and system design evaluation and multiple parameter optimization under practical constraints has been performed of the family of supercritical CO2 Brayton power cycles for application to advanced nuclear reactors. The recompression cycle is shown to excel with respect to simplicity, compactness, cost and thermal efficiency. The main advantage of the supercritical CO2 cycle is comparable efficiency with the helium Brayton cycle at significantly lower temperature (550°C vs. 850 0C), but higher pressure (20 MPa vs. 8 MPa). The supercritical CO2 cycle is well suited to any type of nuclear reactor with core outlet temperature above [approx.] 500 0C in either direct or indirect versions. By taking advantage of the abrupt property changes near the critical point of CO2 the compression work can be reduced, which results in a significant efficiency improvement. However, a real gas cycle requires much more careful optimization than an ideal gas Brayton cycle. Previous investigations by earlier authors were systematized and refined in the present work to survey several different CO2 cycle layouts. Inter- cooling, re-heating, re-compressing and pre-compressing were considered. The recompression cycle was found to yield the highest efficiency, while still retaining simplicity. Inter-cooling is not attractive for this type of cycle as it offers a very modest efficiency improvement. Re-heating has a better potential, but it is applicable only to indirect cycles. Economic analysis of the benefit of re-heating for the indirect cycle showed that using more than one stage of re-heat is economically unattractive.
Author: Qiao Zhao
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Efficiency enhancement in power plant can be seen as a key lever in front of increasing energy demand. Nowadays, both the attention and the emphasis are directed to reliable alternatives, i.e., enhancing the energy conversion systems. The supercritical CO2 (SC-CO2) Brayton cycle has recently emerged as a promising solution for high efficiency power production in nuclear, fossil-thermal and solar-thermal applications. Currently, studies on such a thermodynamic power cycle are directed towards the demonstration of its reliability and viability before the possible building of an industrial-scale unit. The objectives of this PhD can be divided in two main parts: • A rigorous selection procedure of an equation of state (EoS) for SC-CO2 which permits to assess influences of thermodynamic model on the performance and design of a SC-CO2 Brayton cycle. • A framework of optimization-based synthesis of energy systems which enables optimizing both system structure and the process parameters. The performed investigations demonstrate that the Span-Wagner EoS is recommended for evaluating the performances of a SC-CO2 Brayton cycle in order to avoid inaccurate predictions in terms of equipment sizing and optimization. By combining a commercial process simulator and an evolutionary algorithm (MIDACO), this dissertation has identified a global feasible optimum design -or at least competitive solutions- for a given process superstructure under different industrial constraints. The carried out optimization firstly base on cycle energy aspects, but the decision making for practical systems necessitates techno-economic optimizations. The establishment of associated techno-economic cost functions in the last part of this dissertation enables to assess the levelized cost of electricity (LCOE). The carried out multi-objective optimization reflects the trade-off between economic and energy criteria, but also reveal the potential of this technology in economic performance.
Author: Chen, Lin
Publisher: IGI Global
ISBN: 1522520481
Category : Science
Languages : en
Pages : 712
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Book Description
Supercritical fluids have been utilized for numerous scientific advancements and industrial innovations. As the concern for environmental sustainability grows, these fluids have been increasingly used for energy efficiency purposes. Advanced Applications of Supercritical Fluids in Energy Systems is a pivotal reference source for the latest academic material on the integration of supercritical fluids into contemporary energy-related applications. Highlighting innovative discussions on topics such as renewable energy, fluid dynamics, and heat and mass transfer, this book is ideally designed for researchers, academics, professionals, graduate students, and practitioners interested in the latest trends in energy conversion.
Author: Igor Pioro
Publisher: Woodhead Publishing
ISBN: 0128226536
Category : Technology & Engineering
Languages : en
Pages : 1112
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Book Description
Handbook of Generation IV Nuclear Reactors, Second Edition is a fully revised and updated comprehensive resource on the latest research and advances in generation IV nuclear reactor concepts. Editor Igor Pioro and his team of expert contributors have updated every chapter to reflect advances in the field since the first edition published in 2016. The book teaches the reader about available technologies, future prospects and the feasibility of each concept presented, equipping them users with a strong skillset which they can apply to their own work and research. Provides a fully updated, revised and comprehensive handbook dedicated entirely to generation IV nuclear reactors Includes new trends and developments since the first publication, as well as brand new case studies and appendices Covers the latest research, developments and design information surrounding generation IV nuclear reactors
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 155
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Book Description
Supercritical carbon dioxide (SCO2) power cycles show promise for a wide range of applications, such as concentrating solar power, next-generation nuclear reactors, and waste-heat recovery. Models capable of predicting the design-point, off-design, and part-load performance of SCO2 power cycles are necessary for evaluating cycle designs. These models should be flexible in order to accommodate the range of designs under consideration and computationally efficient in order to enable timely optimization studies, possibly while considering cycle performance on an annual or life-cycle basis. This document reports on the development of a modeling framework that accommodates these requirements and is capable of predicting the performance of recuperated and recompression cycle configurations. The modeling framework is in Fortran and is flexible with respect to component-level specifics, such as the type of compressor used in the cycle or the method used to represent the off-design performance of the turbine. Optimization routines are integrated into the models, allowing exploration of optimal component and system designs or optimal operating strategies for a given system design. The optimal design-point and off-design performance of various cycle designs is predicted using turbomachinery models based on the radial compressors and turbines that are currently being investigated by Sandia National Laboratory for use in SCO2 applications. A range of heat rejection (low-side) temperatures are considered and results indicate that operating the cycles at warmer low-side temperatures requires a corresponding increase in low-side pressure in order to maximize thermal efficiency. The relationship between low-side temperature and pressure suggests that inventory control (i.e., actively controlling the low-side pressure) is a favorable control mechanism, especially if the power plant is expected to operate away from its design point for significant periods of time. For cycles designed to operate at warmer heat rejection temperatures (e.g., a dry-cooled design in an arid climate), the benefits of recompression are reduced and a simple recuperated cycle may be favorable. The optimal SCO2 Brayton cycle design depends on the application being considered, and the developed modeling framework provides the consistent performance predictions that are required for further application-specific analyses.
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Languages : en
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Book Description
This report documents work carried out during FY 2008 on further investigation of control strategies for supercritical carbon dioxide (S-CO2) Brayton cycle energy converters. The main focus of the present work has been on investigation of the S-CO2 cycle control and behavior under conditions not covered by previous work. An important scenario which has not been previously calculated involves cycle operation for a Sodium-Cooled Fast Reactor (SFR) following a reactor scram event and the transition to the primary coolant natural circulation and decay heat removal. The Argonne National Laboratory (ANL) Plant Dynamics Code has been applied to investigate the dynamic behavior of the 96 MWe (250 MWt) Advanced Burner Test Reactor (ABTR) S-CO2 Brayton cycle following scram. The timescale for the primary sodium flowrate to coast down and the transition to natural circulation to occur was calculated with the SAS4A/SASSYS-1 computer code and found to be about 400 seconds. It is assumed that after this time, decay heat is removed by the normal ABTR shutdown heat removal system incorporating a dedicated shutdown heat removal S-CO2 pump and cooler. The ANL Plant Dynamics Code configured for the Small Secure Transportable Autonomous Reactor (SSTAR) Lead-Cooled Fast Reactor (LFR) was utilized to model the S-CO2 Brayton cycle with a decaying liquid metal coolant flow to the Pb-to-CO2 heat exchangers and temperatures reflecting the decaying core power and heat removal by the cycle. The results obtained in this manner are approximate but indicative of the cycle transient performance. The ANL Plant Dynamics Code calculations show that the S-CO2 cycle can operate for about 400 seconds following the reactor scram driven by the thermal energy stored in the reactor structures and coolant such that heat removal from the reactor exceeds the decay heat generation. Based on the results, requirements for the shutdown heat removal system may be defined. In particular, the peak heat removal capacity of the shutdown heat removal loop may be specified to be 1.1 % of the nominal reactor power. An investigation of the oscillating cycle behavior calculated by the ANL Plant Dynamics Code under specific conditions has been carried out. It has been found that the calculation of unstable operation of the cycle during power reduction to 0 % may be attributed to the modeling of main compressor operation. The most probable reason for such instabilities is the limit of applicability of the currently used one-dimensional compressor performance subroutines which are based on empirical loss coefficients. A development of more detailed compressor design and performance models is required and is recommended for future work in order to better investigate and possibly eliminate the calculated instabilities. Also, as part of such model development, more reliable surge criteria should be developed for compressor operation close to the critical point. It is expected that more detailed compressor models will be developed as a part of validation of the Plant Dynamics Code through model comparison with the experiment data generated in the small S-CO2 loops being constructed at Barber-Nichols Inc. and Sandia National Laboratories (SNL). Although such a comparison activity had been planned to be initiated in FY 2008, data from the SNL compression loop currently in operation at Barber Nichols Inc. has not yet become available by the due date of this report. To enable the transient S-CO2 cycle investigations to be carried out, the ANL Plant Dynamics Code for the S-CO2 Brayton cycle was further developed and improved. The improvements include further optimization and tuning of the control mechanisms as well as an adaptation of the code for reactor systems other than the Lead-Cooled Fast Reactor (LFR). Since the focus of the ANL work on S-CO2 cycle development for the majority of the current year has been on the applicability of the cycle to SFRs, work has started on modification of the ANL Plant Dynamics Code to allow the dynamic simulation of the ABTR. The code modifications have reached the point where a transient simulation can be run in steady state mode; i.e., to determine the steady state initial conditions at full power without an initiating event. The results show that the steady state solution is maintained with minimal variations during at least 4,000 seconds of the transient. More SFR design specific modifications to the ANL Plant Dynamics Code are required to run the code in a full transient mode, including models for the sodium pumps and their control as well as models for reactivity feedback and control of the reactor power.
Author: Ali Sulaiman H. Alsagri
Publisher:
ISBN:
Category : Brayton cycle
Languages : en
Pages : 124
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Book Description
Various supercritical CO2 Brayton cycles were subjected to energy and exergy analysis for the purpose of improving calculation accuracy; the feasibility of the cycles; and compare the cycles' design points. With respect to improving the accuracy of the analytical model, a computationally efficient technique using constant conductance (UA) to represent heat exchanger performances. Three parametric analysis were conducted: total conductance, maximum and minimum operating temperature, and pressure ratio for appropriate optimization. Recompression sCO2 Brayton cycle based on three parametric analysis achieves the highest thermal efficiency and power output at different operating condition. Also, the findings show that the simple recuperated sCO2 Brayton cycle has the highest specific power output in spite of its simplicity. Then a novel combined power cycle based on the recompression configuration were proposed for the purpose of improving overall thermal efficiency of power cycles by attempting to minimize thermodynamic irreversibilities and waste heat as a consequence of the Second Law. The power cycle concept comprises an advanced recompression sCO2 Brayton configuration as a topping cycle and a split flow tCO2 Rankine configuration as a bottoming cycle. The topping sCO2 recompression Brayton cycle used a combustion chamber as a heat source, and waste heat from a topping cycle was recovered by the tCO2 Rankine cycle due to an added high efficiency recuperator for generating electricity. The combined cycle configurations were thermodynamically modeled and optimized using an Engineering Equation Solver (EES) software. Single and multi-objective optimization techniques conducted in this research is developed using a genetic algorithm (GA). The findings show that the higher thermal efficiency was obtained with recompression sCO2 Brayton cycle-split flow tCO2 Rankine cycle. Also, the results show that the combined sCO2 cycles is practical and promising technology compared to conventional cycles. To produce an ecologically justifiable energy along with cost-competitive, concentrated solar power tower plant model is conducted. The aim of concentrated solar power (CSP) system modeling was to assess the system viability in a location of moderate-to-high solar availability. A case study is presented of a city in Saudi Arabia. To achieve the highest energy production per unit cost, the heliostat geometry and thermal energy storage (TES) dispatch are optimized. Solar power tower (SPT) is one design of CSP technology that is of particular interest here because it can operate at relatively high temperatures. The present SPT-TES field comprises heliostat mirrors, a tower, a receiver, heat exchangers, and two molten-salt TES tanks. The main economic indicators are the capacity factor and the levelized cost of electricity (LCOE). The findings indicate that SPT-TES with sCO2 power cycles is economically viable. The results also show that integrating TES with an SPT has a strong positive impact on the capacity factor at the optimum LCOE.
Author: Anoop Kumar Shukla
Publisher: CRC Press
ISBN: 100056665X
Category : Technology & Engineering
Languages : en
Pages : 306
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Book Description
Hybrid Power Cycle Arrangements for Lower Emissions is an edited book that explores the state-of-the-art for creating effective hybrid power cycles for power generation with lower emission while utilizing different energy sources. The book details energetic and exergetic studies for improving system design and performance of hybrid power cycle arrangements. Chapters in the book provide a systematic approach to the integration and operation of different thermal power cycles with renewable energy sources. The book brings together researchers and practitioners from academia and industry to present their recent and ongoing research and development activities concerning the advancement of hybridization of different conventional and unconventional energy sources to produce efficient and clean energy systems. The book chapters present a range of ongoing research and development activities, challenges, constraints, and opportunities in both theoretical as well as application aspects of several hybrid technologies for power generation. Several issues such as hybridization of different energy sources, availability, environmental impacts, and power cycle integration are addressed in-depth, making this collection a worthy repository for those working in the field of the power cycles.
