Development of a Ceramic Pressurized Volumetric Solar Receiver for Supercritical CO2 Brayton Cycle

2014 ◽  
Author(s):  
S. D. Khivsara ◽  
Rathindra Nath Das ◽  
T. L. Thyagaraj ◽  
Shriya Dhar ◽  
V. Srinivasan ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Supercritical Co2 ◽  
Material Selection ◽  
Radiation Heat Transfer ◽  
Small Scale ◽  
Attractive Alternative ◽  
Transfer Model ◽  
Outlet Temperature ◽  
Brayton Cycle ◽  
Solar Thermal Energy

Recently, the supercritical CO2 (s-CO2) Brayton cycle has been identified as a promising candidate for solar-thermal energy conversion due to its potentially high thermal efficiency (50%, for turbine inlet temperatures of ∼ 1000K). Realization of such a system requires development of solar receivers which can raise the temperature of s-CO2 by over 200K, to a receiver outlet temperature of 1000K. Volumetric receivers are an attractive alternative to tubular receivers due to their geometry, functionality and reduced thermal losses. A concept of a ceramic pressurized volumetric receiver for s-CO2 has been developed in this work. Computational Fluid Dynamics (CFD) analysis along with a Discrete Ordinate Method (DOM) radiation heat transfer model has been carried out, and the results for temperature distribution in the receiver and the resulting thermal efficiency are presented. We address issues regarding material selection for the absorber structure, window, coating, receiver body and insulation. A modular small scale prototype with 0.5 kWth solar heat input has been designed. The design of a s-CO2 loop for testing this receiver module is also presented in this work.

Supercritical CO2 Cycle for Fast Gas-Cooled Reactors

2004 ◽  
Author(s):  
Vaclav Dostal ◽  
Michael J. Driscoll ◽  
Pavel Hejzlar ◽  
Yong Wang
Keyword(s):  
Specific Volume ◽  
Supercritical Co2 ◽  
Nuclear Power ◽  
Nuclear Reactor ◽  
Attractive Alternative ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Brayton Cycle ◽  
Property Changes ◽  
Recompression Cycle

Brayton cycles are currently being extensively investigated for possible use with nuclear reactors in order to reduce capital cost, shorten construction period and increase nuclear power plant efficiency. The main candidates are the well-known helium Brayton cycle and the less familiar supercritical CO2 cycle, which has been given increased attention in the past several years. The main advantage of the supercritical CO2 cycle is comparable efficiency with the helium Brayton cycle at significantly lower temperature (550°C/823K), but higher pressure (20MPa/200 normal atmospheres). 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. Among the surveyed compound cycles the recompression cycle offers the highest efficiency, while still retaining simplicity. The turbomachinery is highly compact and achieves efficiencies of more than 90%. Preliminary assessment of the control scheme has been performed as well. It was found that conventional inventory control could not be applied to the supercritical CO2 recompression cycle. The conventional bypass control is applicable. The reference cycle achieves 46% thermal efficiency at the compressor outlet pressure of 20MPa and turbine inlet temperature of 550°C. The sizing of the heat exchangers and turbomachinery has been performed. The recuperator specific volume is 0.39m3/MWe and pre-cooler specific volume 0.08m3/MWe. For the reference 600MWth reactor this translates to ∼ 99m3 heat exchanger core for the recuperator and ∼ 21m3 for the pre-cooler. Overall the cycle offers an attractive alternative to the steam cycle. The supercritical CO2 cycle is well suited to any type of nuclear reactor with core outlet temperature above ∼ 500°C.

Cycle Calculations of a Small-Scale Heat Removal System With Supercritical CO2 As Working Fluid

2017 ◽  
Author(s):  
Marcel Strätz ◽  
Jörg Starflinger ◽  
Rainer Mertz ◽  
Michael Seewald ◽  
Sebastian Schuster ◽  
...  
Keyword(s):  
Power Plant ◽  
Supercritical Co2 ◽  
Heat Removal ◽  
Working Fluid ◽  
Small Scale ◽  
Brayton Cycle ◽  
Additional Heat ◽  
Decay Heat ◽  
Heat Removal System ◽  
Removal System

In case of an accident in a nuclear power plant with combined initiating events, (loss of ultimate heat sink and station blackout) additional heat removal system could transfer the decay heat from the core to and diverse ultimate heat sink. On additional heat removal system, which is based upon a Brayton cycle with supercritical CO2 as working fluid, is currently investigated within an EU-funded project, sCO2-HeRo (Supercritical carbon dioxide heat removal system). It shall serve as a self-launching, self-propelling and self-sustaining decay heat removal system to be used in severe accident scenarios. Since a Brayton cycle produces more electric power that it consumes, the excess electric power can be used inside the power plant, e.g. recharging batteries. A small-scale demonstrator will be attached to the PWR glass model at Gesellschaft für Simulatorforschung GfS, Essen, Germany. In order to design and build this small-scale model, cycle calculations are performed to determine the design parameters from which a layout can be derived.

Micro Gas Turbine Integrated With a Supercritical CO2 Brayton Cycle Turbine: Layout Comparison and Thermodynamic Analysis

2020 ◽  
Author(s):  
Fabrizio Reale ◽  
Raniero Sannino ◽  
Raffaele Tuccillo
Keyword(s):  
Gas Turbine ◽  
Supercritical Co2 ◽  
Waste Heat ◽  
Thermal Power ◽  
Energy Systems ◽  
Working Fluid ◽  
Small Scale ◽  
Brayton Cycle ◽  
Part Load ◽  
Micro Gas Turbine

Abstract In an energetic scenario where both distributed energy systems and smart energy grids gain increasing relevance, the research focus is also on the detection of new solutions to increase overall performance of small-scale energy systems. Waste heat recovery (WHR) can represent a good solution to achieve this goal, due to the possibility of converting residual thermal power in thermal engine exhausts into electrical power. The authors, in a recent study, described the opportunities related to the integration of a micro gas turbine (MGT) with a supercritical CO2 Brayton Cycle (sCO2 GT) turbine. The adoption of Supercritical Carbon Dioxide (sCO2) as working fluid in closed Brayton cycles is an old idea, already studied in the 1960s. Only in recent years this topic returned to be of interest for electric power generation (i.e. solar, nuclear, geothermal energy or coupled with traditional thermoelectric power plants as WHR). In this technical paper the authors analyzed the performance variations of different systems layout based on the integration of a topping MGT with a sCO2 GT as bottoming cycle; the performance maps for both topping and bottoming turbomachinery have been included in the thermodynamic model with the aim of investigating the part load working conditions. The MGT considered is a Turbec T100P and its behavior at part load conditions is also described. The potential and critical aspects related to the integration of the sCO2 GT as bottoming cycle are studied also through a comparison between different layouts, in order to establish the optimal compromise between overall efficiencies and complexity of the energy system. The off-design analysis of the integrated system is addressed to evaluate its response to variable electrical and thermal demands.

Steady State CFD Investigation of a Radial Compressor Operating With Supercritical CO2

2013 ◽  
Author(s):  
Enrico Rinaldi ◽  
Rene Pecnik ◽  
Pierot Colonna
Keyword(s):  
Steady State ◽  
Critical Point ◽  
Supercritical Co2 ◽  
Tip Clearance ◽  
Working Fluid ◽  
Small Scale ◽  
Brayton Cycle ◽  
Computational Domain ◽  
Proof Of Concept ◽  
Radial Compressor

The supercritical closed Brayton cycle concept is widely recognized as an attractive new option for energy conversion because of the very high-efficiency, reachable at moderate turbine inlet temperature, and the very compact general assembly. Carbon dioxide is chosen as the working fluid because it allows for its compression to occur close to the critical point at suitable temperatures, and high pressure. Compression work is thus small, if compared for instance to air compression. The concept was first studied in the sixties, and recent interest spreading in the scientific and technical community led to the realization of a small-scale proof-of-concept prototype operating at Sandia’s National Laboratories. Moreover, the CSP SunShot project was recently funded by the U.S. National Renewable Energy Laboratory, and it is aimed at the realization of a multi-megawatt concentrating solar power plant, whereby the power block will be a supercritical CO2 Brayton cycle turbine. Other pre-commercial activities are ongoing. This paper focuses on the study of the fluid dynamics of turbomachinery operating with fluids characterized by a complex thermodynamic behavior. The goal is to develop a complete methodology to help the aerodynamic design of scaled-up turbomachinery for supercritical CO2 gas turbine power plants. Starting from a previous analysis of the impeller of the radial compressor of the Sandia proof-of-concept test bench, the new detailed computational domain includes the tip clearance and the vaned diffuser, and has been obtained using an in-house meshing tool suited for turbomachinery geometries. The steady state interface between the impeller and the diffuser is treated with a mixing-plane. In order to correctly calculate the thermophysical properties of the fluid, affected by strong variations close to the critical point, the solver is coupled with an extensive library for the computation of properties of pure fluids and mixtures. An accurate multiparameter equation of state is selected and a look-up table approach is used to speed up the fluid properties evaluation. The results are finally compared with experimental data, and demonstrate the potential of the tool.

Modeling of a High-Temperature-Serpentine External Tubular Receiver Using Supercritical CO2

2014 ◽  
Author(s):  
Samia Afrin ◽  
Jesus D. Ortega ◽  
Clifford K. Ho ◽  
Vinod Kumar
Keyword(s):  
Thermal Efficiency ◽  
Supercritical Co2 ◽  
Incidence Angle ◽  
Normal Incidence ◽  
Incident Radiation ◽  
Heat Transfer Fluid ◽  
Discrete Ordinates ◽  
Outlet Temperature ◽  
Dynamics Model ◽  
Ansys Fluent

This paper describes the modelling and design of an external receiver using supercritical CO2 as the heat transfer fluid that can reach up to 700 °C outlet temperature with ∼85% thermal efficiency. The internal pressure of the tubes is 20 MPa. The receiver tubes are arranged in a serpentine fashion and are coated with Pyromark 2500. Analyses were performed to evaluate the thermal efficiency of the receiver as a function of incidence angle of the incident radiation. Two different radiation models, discrete ordinates and surface-to-surface ray tracing, were used in the computational fluid dynamics model (ANSYS FLUENT). The receiver thermal efficiency ranged from 75% for incidence angles of 80 degrees to 88% for near-normal incidence angles of 10 degrees.

scholarly journals A Design of Parameters with Supercritical Carbon Dioxide Brayton Cycle for CiADS

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Yichuan He ◽  
Aihua Dong ◽  
Min Xie ◽  
Yang Liu
Keyword(s):  
Carbon Dioxide ◽  
Genetic Algorithm ◽  
Supercritical Carbon Dioxide ◽  
Thermal Efficiency ◽  
Search Algorithm ◽  
Pattern Search ◽  
Outlet Temperature ◽  
Brayton Cycle ◽  
Pattern Search Algorithm ◽  
Supercritical Carbon

Recompression supercritical carbon dioxide (SCO2) Brayton Cycle for the Chinese Initiative Accelerator Driven System (CiADS) is taken into account, and flexible thermodynamic modeling method is presented. The influences of the key parameters on thermodynamic properties of SCO2 Brayton Cycle are discussed and the comparative analyses on genetic algorithm and pattern search algorithm are conducted. It is shown that the cycle parameters such as turbine inlet temperature, pressure ratio, outlet temperature at the hot end of condenser, and terminal temperature difference of regenerator 1 and regenerator 2 have significant effects on the cycle thermal efficiency. The calculation results indicate that pattern search algorithm has better optimization performance and quicker calculating speed than genetic algorithm. The result of optimization of the parameters for CiADS with supercritical carbon dioxide Brayton Cycle is 35.97%. Compared with other nuclear power plants of SCO2 Brayton Cycle, CiADS with SCO2 Brayton Cycle does not have the best thermal efficiency, but the thermal efficiency can be improved with the reactor outlet temperature increases.

The Effect of Radiation on Oxy-Fuel Combustion Characteristics in Microchannels

2013 ◽  
Vol 302 ◽  
pp. 49-54
Author(s):  
Rached Ben-Mansour ◽  
Mohamed A. Habib ◽  
Pervez Ahmed
Keyword(s):  
Heat Transfer ◽  
Diffusion Flames ◽  
Radiation Heat Transfer ◽  
Fuel Combustion ◽  
Combustion Characteristics ◽  
Discrete Ordinates ◽  
Small Scale ◽  
Transfer Model ◽  
Radiation Heat ◽  
Radiation Model

The importance of thermal radiation in heat transfer mechanism in many micro combustion systems has been well identified in the past few years. There is currently lack of quantitative understanding on the radiation heat transfer in relatively small scale laminar diffusion flames in microchannels. In the present study a two dimensional model is considered to investigate the effects of radiation on oxy-fuel combustion characteristics in microchannels. The discrete-ordinates radiation model is used for the study. It is observed that excluding radiation model results in the over-prediction of combustion temperatures in the micro-reactor. It has also been observed that the overall reaction rate and its peak value increase when accounting for radiative heat transfer, despite the decrease in temperature caused by radiation. Therefore, it is important to incorporate a radiation heat transfer model in combustion micro-systems in order to predict their characteristics accurately.

Scaling Considerations for a Multi-Megawatt Class Supercritical CO2 Brayton Cycle and Path Forward for Commercialization

2012 ◽  
Author(s):  
Darryn Fleming ◽  
Thomas Holschuh ◽  
Tom Conboy ◽  
Gary Rochau ◽  
Robert Fuller
Keyword(s):  
Supercritical Co2 ◽  
Scale Up ◽  
Small Scale ◽  
Brayton Cycle ◽  
Flow Loop ◽  
Private Industry ◽  
Split Flow ◽  
Efficiency And Effectiveness ◽  
Technical Issues ◽  
Commercial Applications

Small-scale supercritical CO2 demonstration loops are successful at identifying the important technical issues that one must face in order to scale up to larger power levels. The Sandia National Laboratories (Sandia) Supercritical CO2 Brayton cycle test loops are identifying technical needs to scale the technology to commercial power levels such as 10 MWe. The small demonstration loops provide a scalable approach to identify cost, technical hurdles, and future commercialization plans of commercial applications. The small size of the Sandia 1 MWth loop has demonstration of the split flow loop efficiency and effectiveness of the Printed Circuit Heat Exchangers (PCHEs) leading to the design of a fully recuperated, split flow, supercritical CO2 Brayton cycle demonstration system. However there were many problems that were encountered such as; the high rotational speeds in these units identified the need to address bearing, seals, thermal boundaries, and motor controller problems to prove a reliable power source in the 300 kWe range. Although these issues were anticipated in smaller demonstration units, we also understood that commercially scaled hardware would eliminate these problems caused by high rotational speeds at small scale. The economic viability and development of the future scalable 10 MWe solely depends on the interest of DOE and private industry. The Intellectual Property collected by Sandia proves that the ∼10 MWe Supercritical CO2 power conversion loop to be very beneficial when coupled to a 20 MWth heat source (either solar, geothermal, fossil, or nuclear). This paper will identify a commercialization plan, as well as, a roadmap from the simple 1 MWth supercritical CO2 development loop to a power producing 10 MWe supercritical CO2 Brayton loop.

scholarly journals Thermodynamic investigation of intercooling location effect on supercritical CO2 recompression Brayton cycle

2021 ◽  
Vol 15 (3) ◽  
pp. 8262-8276
Author(s):  
Sompop Jarungthammachote
Keyword(s):  
Thermodynamic Model ◽  
Thermal Efficiency ◽  
Supercritical Co2 ◽  
Pressure Ratio ◽  
Brayton Cycle ◽  
Thermodynamic Investigation ◽  
Compression Process ◽  
Study Results ◽  
Optimal Value ◽  
Cycle Efficiency

In S-CO2 recompression Brayton cycle, use of intercooling is a way to improve the cycle efficiency. However, it may decrease the efficiency due to increase of heat rejection. In this work, two S-CO2 recompression Brayton cycles are investigated using the thermodynamic model. The first cycle has intercoolings in a main compression and a recompression process (MCRCIC) and the second cycle has an intercooling in only the recompression process (RCIC). The thermal efficiencies of both cycles are compared with that of S-CO2 recompression Brayton cycle with intercooling in the main compression process (MCIC). Effects of a split fraction (SF) and a ratio of pressure ratio of the recompression (RPRRC) on the thermal efficiencies of MCRCIC and RCIC are also studied. The study results show that the intercooling of recompressor in MCRCIC and RCIC can reduce the compression power. However, it also rejects heat from the cycle and this leads to increasing added heat in the heater. The thermal efficiency of MCRCIC and RCIC are, then, lower than that of the MCIC. For the effects of RPRRC and SF to the thermal efficiency of the cycles, in general, when RPRRC increases, the thermal efficiency decreases due to increasing rejected heat. The increase in SF causes increasing thermal efficiency of the cycles and the thermal efficiency, then, decrease when SF is beyond the optimal value.

scholarly journals Modeling of Combined Lead Fast Reactor and Concentrating Solar Power Supercritical Carbon Dioxide Cycles to Demonstrate Feasibility, Efficiency Gains, and Cost Reductions

2021 ◽  
Vol 13 (22) ◽  
pp. 12428
Author(s):  
Brian T. White ◽  
Michael J. Wagner ◽  
Ty Neises ◽  
Cory Stansbury ◽  
Ben Lindley
Keyword(s):  
Energy Storage ◽  
Heat Exchanger ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Supercritical Co2 ◽  
Solar Power ◽  
Combined Cycle ◽  
Outlet Temperature ◽  
Brayton Cycle ◽  
Concentrating Solar Power

Solar power has innate issues with weather, grid demand and time of day, which can be mitigated through use of thermal energy storage for concentrating solar power (CSP). Nuclear reactors, including lead-cooled fast reactors (LFRs), can adjust power output according to demand; but with high fixed costs and low operating costs, there may not be sufficient economic incentive to make this worthwhile. We investigate potential synergies through coupling CSP and LFR together in a single supercritical CO2 Brayton cycle and/or using the same thermal energy storage. Combining these cycles allows for the LFR to thermally charge the salt storage in the CSP cycle during low-demand periods to be dispatched when grid demand increases. The LFR/CSP coupling into one cycle is modeled to find the preferred location of the LFR heat exchanger, CSP heat exchanger, sCO2-to-salt heat exchanger (C2S), turbines, and recuperators within the supercritical CO2 Brayton cycle. Three cycle configurations have been studied: two-cycle configuration, which uses CSP and LFR heat for dedicated turbocompressors, has the highest efficiencies but with less component synergies; a combined cycle with CSP and LFR heat sources in parallel is the simplest with the lowest efficiencies; and a combined cycle with separate high-temperature recuperators for both the CSP and LFR is a compromise between efficiency and component synergies. Additionally, four thermal energy storage charging techniques are studied: the turbine positioned before C2S, requiring a high LFR outlet temperature for viability; the turbine after the C2S, reducing turbine inlet temperature and therefore power; the turbine parallel to the C2S producing moderate efficiency; and a dedicated circulator loop. While all configurations have pros and cons, use of a single cycle offers component synergies with limited efficiency penalty. Using a turbine in parallel with the C2S heat exchanger is feasible but results in a low charging efficiency, while a dedicated circulator loop offers flexibility and near-perfect heat storage efficiency but increasing cost with additional cycle components.

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