Thermodynamic Optimization of Recuperated S-CO2 Brayton Cycles for Solar Tower Applications

2013 ◽  
Author(s):  
Mahmood Mohagheghi ◽  
Jayanta Kapat
Keyword(s):  
Temperature Difference ◽  
Optimization Process ◽  
Limiting Factors ◽  
Limiting Factor ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Pinch Point ◽  
Point Temperature ◽  
Decision Variables ◽  
Cycle Efficiency

Supercritical carbon dioxide (S-CO2) Brayton cycle represents significant advantages in solar tower application. Various configurations of S-CO2 Brayton cycle employing recuperation, recompression, intercooling and reheating have been investigated. The thermodynamic performance of each cycle configuration is optimized by using Genetic Algorithm in which the maximum cycle efficiency is defined as the objective function. The optimization process is comprehensive, i.e., the decision variables such as temperature and pressure of turbines, compressors, re-heaters, inter-coolers, and the pinch point temperature difference are optimized simultaneously. The recompression inlet temperature and mass flow fraction are also optimized along with other decision variables where that is the case. The main limiting factors in the optimization process are maximum cycle temperature, minimum heat rejection temperature, and pinch point temperature difference. The maximum cycle pressure is also a limiting factor in all studied cases except the simple recuperated cycle. The optimized cycle efficiency can vary from 55.77% to 62.02% where the highest value is obtained for the recompression recuperated cycle with reheating and intercooling. The optimization is based on thermodynamic analysis only, even though decision making for practical systems should be based on thermo-economic optimization.

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.

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.

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.

Optimization on pinch point temperature difference of ORC system based on AHP-Entropy method

Energy ◽  
2017 ◽  
Vol 141 ◽  
pp. 97-107 ◽  
Author(s):  
Jiansheng Wang ◽  
Mengzhen Diao ◽  
Kaihong Yue
Keyword(s):  
Temperature Difference ◽  
Entropy Method ◽  
Pinch Point ◽  
Point Temperature

Determination of an optimal pinch point temperature difference interval in ORC power plant using multi-objective approach

2019 ◽  
Vol 217 ◽  
pp. 798-807 ◽  
Author(s):  
Marcin Jankowski ◽  
Aleksandra Borsukiewicz ◽  
Katarzyna Szopik-Depczyńska ◽  
Giuseppe Ioppolo
Keyword(s):  
Power Plant ◽  
Temperature Difference ◽  
Pinch Point ◽  
Point Temperature ◽  
Multi Objective
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