A Study of Supercritical Carbon Dioxide Power Cycle for Concentrating Solar Power Applications Using an Isothermal Compressor

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Jin Young Heo ◽  
Jinsu Kwon ◽  
Jeong Ik Lee
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Thermal Efficiency ◽  
Solar Power ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Concentrating Solar Power ◽  
Power Cycle ◽  
Compressor Inlet ◽  
Supercritical Carbon

For the concentrating solar power (CSP) applications, the supercritical carbon dioxide (s-CO2) power cycle is beneficial in many aspects, including high cycle efficiencies, reduced component sizing, and potential for the dry cooling option. More research is involved in improving this technology to realize the s-CO2 cycle as a candidate to replace the conventional power conversion systems for CSP applications. In this study, an isothermal compressor, a turbomachine which undergoes the compression process at constant temperature to minimize compression work, is applied to the s-CO2 power cycle layout. To investigate the cycle performance changes of adopting the novel technology, a framework for defining the efficiency of the isothermal compressor is revised and suggested. This study demonstrates how the compression work for the isothermal compressor is reduced, up to 50%, compared to that of the conventional compressor under varying compressor inlet conditions. Furthermore, the simple recuperated and recompression Brayton cycle layouts using s-CO2 as a working fluid are evaluated for the CSP applications. Results show that for compressor inlet temperatures (CIT) near the critical point, the recompression Brayton cycle using an isothermal compressor has 0.2–1.0% point higher cycle thermal efficiency compared to its reference cycle. For higher CIT values, the recompression cycle using an isothermal compressor can perform above 50% in thermal efficiency for a wider range of CIT than the reference cycle. Adopting an isothermal compressor in the s-CO2 layout can imply larger heat exchange area for the compressor which requires further development.

Analysis of Advanced Supercritical Carbon Dioxide Power Cycles With a Bottoming Cycle for Concentrating Solar Power Applications

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Saeb M. Besarati ◽  
D. Yogi Goswami
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Solar Power ◽  
Waste Heat ◽  
Operating Conditions ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Concentrating Solar Power ◽  
Working Fluids ◽  
Supercritical Carbon

A number of studies have been performed to assess the potential of using supercritical carbon dioxide (S-CO2) in closed-loop Brayton cycles for power generation. Different configurations have been examined among which recompression and partial cooling configurations have been found very promising, especially for concentrating solar power (CSP) applications. It has been demonstrated that the S-CO2 Brayton cycle using these configurations is capable of achieving more than 50% efficiency at operating conditions that could be achieved in central receiver tower type CSP systems. Although this efficiency is high, it might be further improved by considering an appropriate bottoming cycle utilizing waste heat from the top S-CO2 Brayton cycle. The organic Rankine cycle (ORC) is one alternative proposed for this purpose; however, its performance is substantially affected by the selection of the working fluid. In this paper, a simple S-CO2 Brayton cycle, a recompression S-CO2 Brayton cycle, and a partial cooling S-CO2 Brayton cycle are first simulated and compared with the available data in the literature. Then, an ORC is added to each configuration for utilizing the waste heat. Different working fluids are examined for the bottoming cycles and the operating conditions are optimized. The combined cycle efficiencies and turbine expansion ratios are compared to find the appropriate working fluids for each configuration. It is also shown that combined recompression-ORC cycle achieves higher efficiency compared with other configurations.

Analysis of Advanced Supercritical Carbon Dioxide Power Cycles With a Bottoming Cycle for Concentrating Solar Power Applications

2013 ◽  
Author(s):  
Saeb M. Besarati ◽  
D. Yogi Goswami
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Solar Power ◽  
Waste Heat ◽  
Operating Conditions ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Concentrating Solar Power ◽  
Working Fluids ◽  
Supercritical Carbon

A number of studies have been performed to assess the potential of using supercritical carbon dioxide (S-CO2) in closed-loop Brayton cycles for power generation. Different configurations have been examined among which recompression and partial cooling configurations have been found very promising, especially for concentrating solar power (CSP) applications. It has been demonstrated that the S-CO2 Brayton cycle using these configurations is capable of achieving more than 50% efficiency at operating conditions that could be achieved in central receiver tower type CSP systems. Although this efficiency is high, it might be further improved by considering an appropriate bottoming cycle utilizing waste heat from the top S-CO2 Brayton cycle. The organic Rankine cycle (ORC) is one alternative proposed for this purpose, however, its performance is substantially affected by the selection of the working fluid. In this paper, a simple S-CO2 Brayton cycle, a recompression S-CO2 Brayton cycle, and a partial cooling S-CO2 Brayton cycle are first simulated and compared with the available data in the literature. Then, an ORC is added to each configuration for utilizing the waste heat. Different working fluids are examined for the bottoming cycles and the operating conditions are optimized. The combined cycle efficiencies and turbine expansion ratios are compared to find the appropriate working fluids for each configuration. It is also shown that combined recompression-ORC cycle achieves higher efficiency compared with other configurations.

Selecting the Optimum Supercritical CO2 Cycle for Indirect-Fired Applications

2019 ◽  
Author(s):  
Brittany Tom ◽  
January Smith ◽  
Aaron M. McClung
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Co2 ◽  
Operating Conditions ◽  
Working Fluid ◽  
Performance Goals ◽  
Brayton Cycle ◽  
Power Cycle ◽  
And Performance ◽  
Supercritical Carbon

Abstract Existing research has demonstrated the viability of supercritical carbon dioxide as an efficient working fluid with numerous advantages over steam in power cycle applications. Selecting the appropriate power cycle configuration for a given application depends on expected operating conditions and performance goals. This paper presents a comparison for three indirect fired sCO2 cycles: recompression closed Brayton cycle, dual loop cascaded cycle, and partial condensation cycle. Each cycle was modeled in NPSS with an air side heater, given the same baseline assumptions and optimized over a range of conditions. Additionally, limitations on the heater system are discussed.

Effect of Compressor Inlet Pressure on Cycle Performance for a Supercritical Carbon Dioxide Brayton Cycle

2018 ◽  
Author(s):  
Eric M. Clementoni ◽  
Timothy L. Cox
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Critical Point ◽  
Inlet Pressure ◽  
Cycle Performance ◽  
Brayton Cycle ◽  
Power Cycle ◽  
Compressor Inlet ◽  
Cycle Efficiency ◽  
Supercritical Carbon

Supercritical carbon dioxide (sCO2) Brayton power cycles take advantage of the high density of CO2 near the critical point to reduce compressor power and increase cycle efficiency. However, thermophysical properties of CO2 vary drastically near the critical point. Concerns of large property variations and liquid formation within the compressor can result in sCO2 cycle designers selecting compressor inlet operating conditions substantially above the critical point, thereby reducing cycle performance. The Naval Nuclear Laboratory has built and tested the 100 kWe Integrated System Test (IST) to demonstrate the ability to operate and control an sCO2 Brayton power cycle over a wide range of conditions. Since the purpose of the IST is focused on controllability, the design compressor inlet conditions were selected to be 8.2°F (4.6°C) and 270 psi (18.4 bar) above the critical point to reduce the effect of small variations in compressor inlet temperature and pressure on density. This paper evaluates the effect of design compressor inlet pressure on cycle efficiency for a simple recuperated Brayton cycle and the performance of an operating Brayton power cycle with a fixed design over a range of compressor inlet pressures.

Modeling Off-Design and Part-Load Performance of Supercritical Carbon Dioxide Power Cycles

2013 ◽  
Author(s):  
John J. Dyreby ◽  
Sanford A. Klein ◽  
Gregory F. Nellis ◽  
Douglas T. Reindl
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Ambient Air ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Heat Rejection ◽  
Power Cycles ◽  
Part Load ◽  
Dry Cooling ◽  
Supercritical Carbon

Continuing efforts to increase the efficiency of utility-scale electricity generation has resulted in considerable interest in Brayton cycles operating with supercritical carbon dioxide (S-CO2). One of the advantages of S-CO2 Brayton cycles, compared to the more traditional steam Rankine cycle, is that equal or greater thermal efficiencies can be realized using significantly smaller turbomachinery. Another advantage is that heat rejection is not limited by the saturation temperature of the working fluid, facilitating dry cooling of the cycle (i.e., the use of ambient air as the sole heat rejection medium). While dry cooling is especially advantageous for power generation in arid climates, the reduction in water consumption at any location is of growing interest due to likely tighter environmental regulations being enacted in the future. Daily and seasonal weather variations coupled with electric load variations means the plant will operate away from its design point the majority of the year. Models capable of predicting the off-design and part-load performance of S-CO2 power cycles are necessary for evaluating cycle configurations and turbomachinery designs. This paper presents a flexible modeling methodology capable of predicting the steady state performance of various S-CO2 cycle configurations for both design and off-design ambient conditions, including part-load plant operation. The models assume supercritical CO2 as the working fluid for both a simple recuperated Brayton cycle and a more complex recompression Brayton cycle.

Supercritical Carbon Dioxide Power Cycle Configurations for Use in Concentrating Solar Power Systems

2012 ◽  
Author(s):  
Craig S. Turchi ◽  
Zhiwen Ma ◽  
John Dyreby
Keyword(s):  
Carbon Dioxide ◽  
Energy Storage ◽  
Molten Salt ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Solar Power ◽  
Brayton Cycle ◽  
Concentrating Solar Power ◽  
Power Cycle ◽  
Cycle Efficiency

Concentrating Solar Power (CSP) plants utilize oil, molten salt or steam as the heat transfer fluid (HTF) to transfer solar energy to the power block. These fluids have properties that limit plant performance; for example, the synthetic oil and molten salt have upper temperature limits of approximately 390°C and 565°C, respectively. While direct steam generation has been tested, it requires complex controls and has limited options for integration of thermal energy storage. Use of carbon dioxide as the HTF and power cycle working fluid offers the potential to increase thermal cycle efficiency while maintaining simplicity of operation and thermal storage options. Supercritical CO2 (s-CO2) operated in a closed-loop recompression Brayton cycle offers the potential of higher cycle efficiency versus superheated or supercritical steam cycles at temperatures relevant for CSP applications. Brayton-cycle systems using s-CO2 have smaller weight and volume, lower thermal mass, and less complex power blocks versus Rankine cycles due to the higher density of the fluid and simpler cycle design. Many s-CO2 Brayton power cycle configurations have been proposed and studied for nuclear applications; the most promising candidates include recompression, precompression, and partial cooling cycles. Three factors are important for incorporating s-CO2 into CSP plants: superior performance vs. steam Rankine cycles, ability to integrate thermal energy storage, and dry-cooling. This paper will present air-cooled s-CO2 cycle configurations specifically selected for a CSP application. The systems will consider 10-MW power blocks that are tower-mounted with an s-CO2 HTF and 100-MW, ground-mounted s-CO2 power blocks designed to receive molten salt HTF from a power tower.

Development of the Supercritical Carbon Dioxide Power Cycle Experimental Loop With a Turbo-Generator

2017 ◽  
Author(s):  
Junhyun Cho ◽  
Hyungki Shin ◽  
Jongjae Cho ◽  
Ho-Sang Ra ◽  
Chulwoo Roh ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
High Speed ◽  
Small Scale ◽  
Brayton Cycle ◽  
Power Cycle ◽  
Turbo Generator ◽  
Test Loop ◽  
Class Test ◽  
Supercritical Carbon

KIER (Korea Institute of Energy Research) has developed three supercritical carbon dioxide power cycle test loops since 2013. After developing a 10 kWe-class simple un-recuperated Brayton cycle, a second sub-kWe small-scale experimental test loop was manufactured to investigate the characteristics of the supercritical carbon dioxide power cycle, for which a high speed radial type turbo-generator was also designed and manufactured. Using only one channel of the nozzle, the partial admission method was adopted to reduce the rotational speed of the rotor so that commercial oil-lubricated bearings can be used. This was the world’s first approach to the supercritical carbon dioxide turbo-generator. After several tests, operation of the turbine for power production of up to 670 W was successful. Finally, an 80 kWe-class dual Brayton cycle test loop was designed. Before completion of the full test loop, a 60 kWe axial type turbo-generator was first manufactured and our previous 10 kWe-class test loop was upgraded to drive this turbo-generator. Due to leakage flow through the mechanical seal, a make-up loop was also developed. After assembling all test loops, a cold-run test and a preliminary operation test were conducted. In this paper, the power generating operation results of the sub-kWe-class test loop and the construction of the tens of kWe-class test loop which drives an axial type turbo-generator are described.

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