Integration and Optimization of Supercritical Carbon Dioxide Brayton Cycle and Goswami Cycle

2019 ◽  
Author(s):  
Diego Guillen ◽  
Martina Leveni ◽  
Giampaolo Manfrida ◽  
Marco Sanjuan
Keyword(s):  
Waste Heat ◽  
Thermodynamic Cycle ◽  
Energy System ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Power Cycle ◽  
Cost Of Energy ◽  
Space Cooling ◽  
The Cost ◽  
Cycle Efficiency

Abstract Utilization of waste heat from an energy conversion process is a key step in improving the overall energy system conversion efficiency and reducing the cost of energy. Since a supercritical CO2 Brayton power cycle is being considered as an important cycle for the conversion of solar energy to power, we propose to utilize the heat rejected from this cycle to feed a bottoming thermodynamic cycle. Goswami cycle can utilize the low temperature waste heat to produce both power and cooling in the same loop. Moreover, refrigeration and space cooling are usually more expensive than heating in most applications. This paper describes the modeling and simulation results of the combined Brayton and Goswami cycles. The mass flow ratio of the two cycles is determined by the heat exchanger effectiveness method, constraining the minimum allowed temperature difference. The operating parameters that yield the best performance in terms of overall cycle efficiency, net work, and cooling outputs were found through the optimization of a numerical model developed in MATLAB. The cooling production in the Goswami cycle is maximized at the expense of the net work in order to produce the maximum refrigeration output. A maximum combined efficiency for power and cooling generation above 45% can be found when the inlet temperature at the Brayton cycle is set at 700 °C.

Brayton Cycle As an Alternate Power Conversion Option for Sodium Cooled Fast Reactor

2019 ◽  
Author(s):  
Jofred Joseph ◽  
Satish Kumar ◽  
Tanmay Vasal ◽  
N. Theivarajan
Keyword(s):  
Power Conversion ◽  
Rankine Cycle ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Generation System ◽  
Fast Reactors ◽  
Turbine Inlet Temperature ◽  
Power Cycle ◽  
Power Generation System ◽  
Cycle Efficiency

Abstract Enhancing the safety and economic competitiveness are major objectives in the development of advanced reactor designs with emphasis on the design of systems or components of the nuclear systems. Innovative power cycle development is another potential option to achieve these objectives. Sodium cooled fast reactor (SFR) is one among the six reactor design concepts identified by the Gen IV International Forum for development to meet the technology goals for new nuclear energy system. Similar to the power cycle used in conventional fossil fuel based thermal power plants, sodium-cooled fast reactors have adopted the Rankine cycle based power conversion system. However, the possibility of sodium water reaction is a major concern and it becomes necessary to adopt means of early detection of leaks and isolation of the affected SG module for mitigating any adverse impact of sodium water reaction. The high exothermic nature of the reaction calls for introducing an intermediate sodium heat transport loop, leading to high overall plant cost hindering commercialization of sodium fast reactors. The Indian Prototype Fast Breeder Reactor (PFBR) also uses Rankine cycle in the power generation system. The superheated steam temperature has been set at 490 degree Celsius based on optimisation studies and material limitations. Additional Fast Breeder reactors are planned in near future and further work is being done to develop more advanced sodium cooled fast reactors. The closed Brayton cycle is a promising alternative to conventional Rankine cycle. By selecting an inert gas or a gas with milder reaction with sodium, the vigorous sodium water reaction can be avoided and significant cost savings in the turbine island can be achieved as gas turbine power conversion systems are of much smaller size than comparable steam turbine systems due to their higher power density. In the study, various Brayton cycle designs on different working gases have been explored. Supercritical-CO2 (s-CO2), helium and nitrogen cycle designs are analyzed and compared in terms of cycle efficiency, component performance and physical size. The thermal efficiencies at the turbine inlet temperature of Indian PFBR have been compared for Rankine cycle and Brayton cycle based on different working fluids. Also binary mixtures of different gases are investigated to develop a more safe and efficient power generation system. Helium does not interact with sodium and other structural materials even at very high temperatures but its thermal performance is low when compared to other fluids. Nitrogen being an inert gas does not react with sodium and can serve to utilise existing turbomachinery because of the similarity with atmospheric air. The supercritical CO2 based cycle has shown best thermodynamic performance and efficiency when compared to other Brayton cycles for the turbine inlet temperature of Indian PFBR. CO2 also reacts with sodium but the reaction is mild compared to sodium water reaction. The cycle efficiency of the s-CO2 cycle can be further improved by adopting multiple reheating, inter cooling and recuperation.

scholarly journals Techno-Economic Feasibility Study of Investigation of Renewable Energy System for Rural Electrification in South Algeria

2018 ◽  
Vol 8 (5) ◽  
pp. 3421-3426 ◽  
Author(s):  
F. Chermat ◽  
M. Khemliche ◽  
A. E. Badoud ◽  
S. Latreche
Keyword(s):  
Greenhouse Gas Emission ◽  
Electrical Energy ◽  
Energy System ◽  
Economic Feasibility ◽  
Maintenance Cost ◽  
Management Algorithm ◽  
Cost Of Energy ◽  
The Cost ◽  
Operation And Maintenance Cost ◽  
Different Sources

This work aims to consider the combination of different technologies regarding energy production and management with four possible configurations. We present an energy management algorithm to detect the best design and the best configuration from the combination of different sources. This combination allows us to produce the necessary electrical energy for supplying habitation without interruption. A comparative study is conducted among the different combinations on the basis of the cost of energy, diesel consumption, diesel price, capital cost, replacement cost, operation, and maintenance cost and greenhouse gas emission. Sensitivity analysis is also performed.

Numerical Study of a Micro Gas Turbine Integrated With a Supercritical CO2 Brayton Cycle Turbine

2018 ◽  
Author(s):  
Fabrizio Reale ◽  
Vincenzo Iannotta ◽  
Raffaele Tuccillo
Keyword(s):  
Gas Turbines ◽  
Waste Heat ◽  
Numerical Study ◽  
Organic Rankine Cycle ◽  
Energy Systems ◽  
Rankine Cycle ◽  
Energy System ◽  
Small Scale ◽  
Brayton Cycle ◽  
Integrated Energy System

The primary need of reducing pollutant and greenhouse gas emissions has led to new energy scenarios. The interest of research community is mainly focused on the development of energy systems based on renewable resources and energy storage systems and smart energy grids. In the latter case small scale energy systems can become of interest as nodes of distributed energy systems. In this context micro gas turbines (MGT) can play a key role thanks to their flexibility and a strategy to increase their overall efficiency is to integrate gas turbines with a bottoming cycle. In this paper the authors analyze the possibility to integrate a MGT with a super critical CO2 Brayton cycle turbine (sCO2 GT) as a bottoming cycle (BC). A 0D thermodynamic analysis is used to highlight opportunities and critical aspects also by a comparison with another integrated energy system in which the waste heat recovery (WHR) is obtained by the adoption of an organic Rankine cycle (ORC). While ORC is widely used in case of middle and low temperature of the heat source, s-CO2 BC is a new method in this field of application. One of the aim of the analysis is to verify if this choice can be comparable with ORC for this operative range, with a medium-low value of exhaust gases and very small power values. The studied MGT is a Turbec T100P.

CFD–Aided Design Methodology for PCHE-Type Recuperators in Supercritical CO2 Recompression Power Cycles

2020 ◽  
Author(s):  
George Stamatellos ◽  
Antiopi-Malvina Stamatellou ◽  
Anestis I. Kalfas
Keyword(s):  
Design Methodology ◽  
High Capacity ◽  
Computation Time ◽  
Channel Length ◽  
Brayton Cycle ◽  
Power Cycles ◽  
Power Cycle ◽  
Design Options ◽  
Aided Design ◽  
Cycle Efficiency

Abstract The supercritical carbon dioxide (sCO2) cycle has emerged as a promising power cycle for various types of power conversion systems, based on its high thermal efficiency, (approaching 60%), small-size and compactness. The recompression Brayton cycle with sCO2 is based on high capacity regenerators processing a large amount of heat making their effectiveness critical for the overall cycle efficiency. Printed Circuit Heat Exchangers (PCHEs) are used in these cycles because of their high attainable effectiveness values. The design process for these regenerators is demanding, considering the peculiarities of variation of CO2 density and thermal properties near the critical temperature. On the other hand, a reduced computation time is necessary for the quick assessment of alternative design options. A hybrid design methodology for the high-temperature and the low-temperature recuperator (HTR and LTR) is presented in this paper, which employs 3D CFD conjugate heat transfer computation of the performance of a small two-channel module of the PCHE type. The results of the module computation are deployed in a 1D segmental method for the performance computation of the full heat exchanger’s channel length. Thus, the thermal effectiveness and pressure drop characteristics for the full heat exchanger are computed fast and with high accuracy. Application of the proposed methodology is carried out for the HTR and LTR computation in a recompression sCO2 Brayton cycle of a 600 MWth size power plant.

Techno-Economic Feasibility Analysis of Pumped Storage Hydroelectricity in Abandoned Underground Coal Mines

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Dacheng Shang ◽  
Peng Pei ◽  
Yujun Zuo
Keyword(s):  
Coal Seam ◽  
Capital Investment ◽  
Economic Feasibility ◽  
Abandoned Mines ◽  
Cost Of Energy ◽  
Calculation Results ◽  
Pumped Storage ◽  
Geological Constraints ◽  
The Cost ◽  
Cycle Efficiency

Abstract It is anticipated that utilizing the underground space in abandoned mines to build and operate pumped-storage hydroelectricity (PSH) plants can reduce capital investment and geological constraints. However, there are currently few detailed investigations into techno-economic feasibility except for conceptual studies. In this paper, an underground coal mine in Guizhou, China was used as a reference, and the PSH layout was designed; in addition, the head loss, plant efficiency, and major cost components were investigated. The calculation results show that the capital investment of mine-based PSH was 33–50% less than that of conventional PSH. Sensitivity analysis found a clear influence of coal seam inclination on the performance of the mine-based PSH. Under the assumed conditions, the plant cycle efficiency increased from 62.7% to 71.5% when the coal seam dip varied from 5 deg to 25 deg. Depending on different price scenarios, when the coal seam inclination was steep enough, the cost of energy storage of a mine-based PSH plant was competitive compared with conventional PSH, and the plant could even become profitable. The influence of the dip of coal seam was more pronounced when in the lower range (5–15 deg) than the higher range (15–25 deg).

Pinch Point Analysis of Air Cooler in sCO2 Brayton Cycle Operating Over Ambient Temperature Range

2019 ◽  
Author(s):  
Ankur Deshmukh ◽  
Jayanta Kapat
Keyword(s):  
Water Discharge ◽  
Ambient Air ◽  
Operating Conditions ◽  
Brayton Cycle ◽  
Pinch Point ◽  
Power Cycle ◽  
Point Analysis ◽  
Air Cooler ◽  
Set Up ◽  
Cycle Efficiency

Abstract Supercritical CO2 Brayton Power cycle is getting commercially attractive for power generation due to its numerous advantages like zero water discharge, compactness, low environmental emission and potential to reach high thermal efficiency. A typical recuperated sCO2 closed cycle consists of three heat exchangers (main heat exchanger, cooler and recuperator) and two turbomachinery (sCO2 turbine and sCO2 compressor). The cooler using ambient air for cooling is the focus of this study. Steady state air cooler model is set up to study the effect of air cooler size on cycle efficiency. The effect of change in ambient air temperature on air cooler pinch point for different air cooler sizes is analyzed using transient air cooler model. The simulation is setup for design of approximately 100MWe sCO2 cycle with operating temperature of 700° C and pressure of 250 barA. Transient calculations are done using LMS AMESim. LMS AMESim is Siemens PLM commercially available software. This work thus serves as a framework to develop a design basis for air cooler in sCO2 cycle as a function of transient operating conditions.

Primary Study on Carbon Dioxide Power Cycle of HTGR

2008 ◽  
Author(s):  
Chengjie Duan ◽  
Xiaoyong Yang ◽  
Jie Wang ◽  
Suyuan Yu
Keyword(s):  
Carbon Dioxide ◽  
High Temperature ◽  
Physical Properties ◽  
Critical Pressure ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Power Cycle ◽  
Pressure Cycle ◽  
Cycle Efficiency ◽  
Thermal Physical Properties

At present, power cycles used in HTGR are indirect steam Rankine cycle and helium Brayton cycle. Using water or helium as working fluid which transform thermal energy into mechanical energy for HTGR power cycle has many disadvantages. Steam cycle could choose steam system which is similar to conventional coal-fired power plant, but because of the limit of material and equipments, there is big temperature difference between the steam and the helium, that makes big loss of thermal power and lowers the cycle efficiency. Helium can reach a high temperature in HTGR Brayton cycle and it has good stability, but because of helium has big isentropic exponent and low density, it is difficult to compress and makes helium turbine has shorter blades and more stages than normal gas turbine. Carbon dioxide has good thermal stability and physical properties. To avoid the reaction of CO2 with graphite and canning of fuel element at high temperature, it should be used in an indirect cycle as second loop working fluid. CO2 has appropriate critical pressure and temperature (7.38MPa, 304.19K) and can choose three types of cycle: supercritical cycle, subcritical-pressure cycle and trans-critical-pressure cycle (CO2 sometimes works under supercritical pressure, some times under subcritical-pressure). Carbon dioxide cycle works in a high pressure, so it makes pressure loss lower. When CO2 works close to its critical point, its density become larger than other conditions, and not change very much, this permits to reduce compress work. The thermal physical properties of carbon dioxide are totally different from helium due to CO2 works as real gas in the cycle. That causes the calculation of CO2 thermal physical properties, heat transfer and power cycle efficiency become difficult and need to be iterated. A systematic comparison between helium and carbon dioxide as working fluid for HTGR has been carried out. An empirical equation had been selected to estimate the thermal physical properties of carbon dioxide. Three types of carbon dioxide power cycle have been analyzed and the thermal efficiency has been calculated. A detailed introduction to the basic calculation process of the CO2 cycle thermal efficiency had been presented in the paper.

scholarly journals Thermal Performance Analysis of a Direct-Heated Recompression Supercritical Carbon Dioxide Brayton Cycle Using Solar Concentrators

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4358 ◽  
Author(s):  
Jinping Wang ◽  
Jun Wang ◽  
Peter D. Lund ◽  
Hongxia Zhu
Keyword(s):  
Incidence Angle ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Turbine Inlet Temperature ◽  
Beam Radiation ◽  
Solar Concentrators ◽  
Cooling Temperature ◽  
Turbine Inlet ◽  
Cycle Efficiency

In this study, a direct recompression supercritical CO2 Brayton cycle, using parabolic trough solar concentrators (PTC), is developed and analyzed employing a new simulation model. The effects of variations in operating conditions and parameters on the performance of the s-CO2 Brayton cycle are investigated, also under varying weather conditions. The results indicate that the efficiency of the s-CO2 Brayton cycle is mainly affected by the compressor outlet pressure, turbine inlet temperature and cooling temperature: Increasing the turbine inlet pressure reduces the efficiency of the cycle and also requires changing the split fraction, where increasing the turbine inlet temperature increases the efficiency, but has a very small effect on the split fraction. At the critical cooling temperature point (31.25 °C), the cycle efficiency reaches a maximum value of 0.4, but drops after this point. In optimal conditions, a cycle efficiency well above 0.4 is possible. The maximum system efficiency with the PTCs remains slightly below this value as the performance of the whole system is also affected by the solar tracking method used, the season and the incidence angle of the solar beam radiation which directly affects the efficiency of the concentrator. The choice of the tracking mode causes major temporal variations in the output of the cycle, which emphasis the role of an integrated TES with the s-CO2 Brayton cycle to provide dispatchable power.

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