Thermodynamic Analyses of Single Brayton and Combined Brayton–Rankine Cycles for Distributed Solar Thermal Power Generation

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
M. T. Dunham ◽  
W. Lipiński

This paper reports theoretical efficiencies of single Brayton and combined Brayton–Rankine thermodynamic power cycles for distributed solar thermal power generation. Thermodynamic analyses are conducted with a nominal heat input to the cycle of 150 kW and component parameters for a 50 kWe gas microturbine for selected working fluids including air, Ar, CO2, He, H2, and N2 for the Brayton cycle and for the topping cycle of the combined system. Cycle parameters including maximum fluid temperature based on solar concentration ratio, pressure loss, and compressor/turbine efficiencies are then varied to examine their effect on cycle efficiency. C6-fluoroketone, cyclohexane, n-pentane, R-141b, R-245fa, and HFE-7000 are examined as working fluids in the bottoming segment of the combined cycle. A single Brayton cycle is found to reach a peak cycle efficiency of 15.31% with carbon dioxide at design point conditions. Each Brayton cycle fluid is examined as a topping cycle fluid in the combined cycle, being paired with six potential bottoming fluids, resulting in 36 working fluid configurations. The combination of the Brayton topping cycle using carbon dioxide and the Rankine bottoming cycle using R-245fa gives the highest combined cycle efficiency of 21.06%.

Author(s):  
Marc Dunham ◽  
Wojciech Lipinski

This paper explores the theoretical efficiencies of single Brayton and combined Brayton-Rankine thermodynamic power cycles for distributed solar thermal power generation. Thermodynamic analyses are conducted for the nominal solar power input to the receiver of 75 kW, concentration ratio in the range 50–100 suns, and for selected heat transfer fluids including air, argon, carbon dioxide, helium, and hydrogen for the Brayton cycle and for the topping cycle of the combined system. C6-fluoroketone, cyclohexane, n-pentane, R-141b, R-245fa, HFE-7000, and steam are examined as working fluids in the bottoming segment of the combined cycle. A single Brayton cycle is found to reach a peak efficiency of 13.3% with carbon dioxide and 100 suns solar input. The four top-performing Brayton cycle fluids are examined as topping cycle fluids in the combined cycle. Each of the four fluids is paired with seven potential bottoming fluids, resulting in 28 heat transfer fluid configurations. The combination of the Brayton topping cycle using carbon dioxide and the Rankine bottoming cycle using R-141b gives the highest thermal efficiency of 22.3% for 100 suns.


2019 ◽  
Vol 29 ◽  
pp. 24-41 ◽  
Author(s):  
Daniel Akinyele ◽  
Olubayo Babatunde ◽  
Chukwuka Monyei ◽  
Lanre Olatomiwa ◽  
Adebunmi Okediji ◽  
...  

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
J. Ignacio Ortega ◽  
J. Ignacio Burgaleta ◽  
Félix M. Téllez

Of all the technologies being developed for solar thermal power generation, central receiver systems (CRSs) are able to work at the highest temperatures and to achieve higher efficiencies in electricity production. The combination of this concept and the choice of molten salts as the heat transfer fluid, in both the receiver and heat storage, enables solar collection to be decoupled from electricity generation better than water∕steam systems, yielding high capacity factors with solar-only or low hybridization ratios. These advantages, along with the benefits of Spanish legislation on solar energy, moved SENER to promote the 17MWe Solar TRES plant. It will be the first commercial CRS plant with molten-salt storage and will help consolidate this technology for future higher-capacity plants. This paper describes the basic concept developed in this demonstration project, reviewing the experience accumulated in the previous Solar TWO project, and present design innovations, as a consequence of the development work performed by SENER and CIEMAT and of the technical conditions imposed by Spanish legislation on solar thermal power generation.


2021 ◽  
Vol 25 (4 Part B) ◽  
pp. 2861-2870
Author(s):  
Ruilian Wang ◽  
Zichao Zhang ◽  
Xinxu Wei

The thermal storage system is an essential part of the trough solar thermal power generation system. Due to the strong randomness, intermittency, and volatility of solar energy resources, to further improve the system?s overall reliability to meet the needs of variable operating conditions, the paper optimizes the control strategy of the trough solar heat storage system. Taking the molten salt heat storage medium in the oil/salt heat exchanger, the core equipment of the heat storage system, as the critical research object, the article adopts proportional, integral, and differential (PID) control theories. It builds the system in the MATLAB/Simulink simulation environment mathematical model. We use the critical proportionality method to determine many critical parameters in the control system, tune the proportional coefficient, integral time, and other physical quantities in the PID controller, and analyze the proportional control, proportional-integral control, PID controls the respective dynamic response characteristics of these three different control systems. The simulation and comparative analysis results show that: compared with the other two control methods, PID control can effectively weaken the heat storage system oscillation caused by external disturbance, its dynamic response speed is faster, the adjustment time is shorter, and it can meet the requirements of operational stability. The paper adopts PID control, which reduces the control difficulty of the trough solar heat storage system and improves the adaptability to changes in external meteorological resources. The research results have particular guiding significance at the academic and engineering levels.


2021 ◽  
Vol 25 (4 Part B) ◽  
pp. 2905-2912
Author(s):  
Bowen Wang

In the smart grid context, the article combines SEGS-VI solar thermal power station parameters to establish a solar thermal power generation system model. The thesis is based on the First and Second laws of thermodynamics. It uses the white box model analysis method of the energy system to calculate the solar thermal power generation system-concentrating and collecting subsystem, heat exchange subsystem, and power subsystem to obtain the subsystems dissipation of each process. Finally, the article uses the white box model analysis of the total energy system to treat the subsystems as white boxes, and connects them to form a white box network, makes a reasonable evaluation of the energy consumption status of the total energy system, and finds the weak links in the energy use process of the system. Provide a basis for system energy saving.


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