CO2-based mixtures as working fluids for geothermal turbines.

Wright, Steven A.; Conboy, Thomas M; Ames, David E.

doi:10.2172/1049477

Cited by 13 publications

(5 citation statements)

References 4 publications

(8 reference statements)

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“…In addition to the investigation of different S-CO 2 configurations, researchers also carried out the comparison between pure CO 2 and CO 2 mixtures. Wright et al [102] developed an S-CO 2 cycle for low-temperature geothermal heat sources and conducted a system performance comparison when either CO 2 -mixture (CO 2 /butane) or pure CO 2 as a working fluid. The findings indicated that, at a turbine inlet temperature of 160 • C and a dry heat rejection temperature of 46.7 • C, the efficiency of the CO 2 -mixture cycle was 18.1%, while the efficiency of the pure CO 2 cycle was 15%.…”

Section: S-co 2 Cycle For Geothermal Power Systemsmentioning

confidence: 99%

Power Generation with Renewable Energy and Advanced Supercritical CO2 Thermodynamic Power Cycles: A Review

Zhang,

2023

Energies

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Supercritical CO2 (S-CO2) thermodynamic power cycles have been considerably investigated in the applications of fossil fuel and nuclear power generation systems, considering their superior characteristics such as compactness, sustainability, cost-effectiveness, environmentally friendly working fluid and high thermal efficiency. They can be potentially integrated and applied with various renewable energy systems for low-carbon power generation, so extensive studies in these areas have also been conducted substantially. However, there is a shortage of reviews that specifically concentrate on the integrations of S-CO2 with renewable energy, encompassing biomass, solar, geothermal and waste heat. It is thus necessary to provide an update and overview of the development of S-CO2 renewable energy systems and identify technology and integration opportunities for different types of renewable resources. Correspondingly, this paper not only summarizes the advantages of CO2 working fluid, design layouts of S-CO2 cycles and classifications of renewable energies to be integrated but also reviews the recent research activities and studies carried out worldwide on advanced S-CO2 power cycles with renewable energy. Moreover, the performance and development of various systems are well grouped and discussed.

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Section: S-co 2 Cycle For Geothermal Power Systemsmentioning

confidence: 99%

Power Generation with Renewable Energy and Advanced Supercritical CO2 Thermodynamic Power Cycles: A Review

Zhang,

2023

Energies

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“…So far, a few studies have been conducted to discuss the feasibility and performance of the supercritical CO 2 -based mixture power cycle. For example, Sandia National Laboratories performed experimental tests on the compatibility of CO 2 mixtures with the turbomachinery and the compressor operation in the supercritical region of mixtures [18]. Jeong et al [19,20] developed a supercritical cycle model, based on the mixture properties.…”

Section: Current Status Of Co 2 -Based Mixturesmentioning

confidence: 99%

New Knowledge on the Performance of Supercritical Brayton Cycle with CO2-Based Mixtures

Zhao

et al. 2020

Energies

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As one of the promising technologies to meet the increasing demand for electricity, supercritical CO2 (S-CO2) Brayton cycle has the characteristics of high efficiency, economic structure, and compact turbomachinery. These characteristics are closely related to the thermodynamic properties of working fluid. When CO2 is mixed with other gas, cycle parameters are determined by the constituent and the mass fraction of CO2. Therefore, in this contribution, a thermodynamic model is developed and validated for the recompression cycle. Seven types of CO2-based mixtures, namely CO2-Xe, CO2-Kr, CO2-O2, CO2-Ar, CO2-N2, CO2-Ne, and CO2-He, are employed. At different CO2 mass fractions, cycle parameters are determined under a fixed compressor inlet temperature, based on the maximization of cycle efficiency. Cycle performance and recuperators’ parameters are comprehensively compared for different CO2-based mixtures. Furthermore, in order to investigate the effect of compressor inlet temperature, cycle parameters of CO2-N2 are obtained under four different temperatures. From the obtained results, it can be concluded that, as the mass fraction of CO2 increases, different mixtures show different variations of cycle performance and recuperators’ parameters. In generally, the performance order of mixtures coincides with the descending or ascending order of corresponding critical temperatures. Performance curves of these considered mixtures locate between the curves of CO2-Xe and CO2-He. Meanwhile, the curves of CO2-O2 and CO2-N2 are always closed to each other at high CO2 mass fractions. In addition, with the increase of compressor inlet temperature, cycle performance decreases, and more heat transfer occurs in the recuperators.

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“…[1][2][3][4][5] Furthermore, the density of CO 2 is relatively higher compared to the conventional working fluid, such as air or steam, as sCO 2 Brayton cycle operates at high pressure, which automatically results in exceedingly smaller sizes and higher rotational speed of rotating machinery, [6][7][8] including radial turbine, compressor, and generator. For the Brayton cycle with sCO 2 as working fluid, where the output power is below 1 MW, all rotating machines are incorporated into a sCO 2 turbinealternator-compressor (TAC) unit, [9][10][11] which can reduce the cost and enable modular construction technology. 12 In the generator of sCO 2 TAC unit, the shaft-type gap between rotor and stator is filled with the lowtemperature sCO 2 with axial flow, which is used to transfer the heat generated by the rotating rotor, to effectively achieve the purpose of cooling the generator, as shown in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the density of CO 2 is relatively higher compared to the conventional working fluid, such as air or steam, as sCO 2 Brayton cycle operates at high pressure, which automatically results in exceedingly smaller sizes and higher rotational speed of rotating machinery, 6–8 including radial turbine, compressor, and generator. For the Brayton cycle with sCO 2 as working fluid, where the output power is below 1 MW, all rotating machines are incorporated into a sCO 2 turbine‐alternator‐compressor (TAC) unit, 9–11 which can reduce the cost and enable modular construction technology 12 …”

Section: Introductionmentioning

confidence: 99%

Action mechanism of axial flow on windage loss in open shaft‐type gap with CO₂

Hu,

Deng,

Liu

et al. 2023

Energy Science & Engineering

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The windage loss in rotor‐stator gap has an important effect on rotating machinery, especially with higher rotational speed and fluid density. However, the mechanism of axial flow on windage loss in open shaft‐type gap is hardly studied in most literature. To clarify it, the influences of axial Reynolds number Reu and rotational Reynolds number Reω on skin friction coefficient Cf are investigated, and flow characteristics are analyzed with different gap geometry, radius ratio η. First, the results reveal that the Cf remains constant when Reu is less than 2.8 × 104 and increases rapidly as Reu when Reu ≥ 2.8 × 104, which indicates that the effect of axial velocity u on Cf is negligible for low Reu. The positive relative deviation Δ suggests that the axial flow makes windage loss and Cf rise. Besides, a larger number of Taylor vortexes fill with gap when the effect of the centrifugal force is larger than that of the inertial force, but they gradually disappear as Reu. Subsequently, the Cf and Δ increase as η, highlighting that the effect of u on windage loss and Cf is more prominent for larger η. The fact that vorticity near walls is larger than that at the center of gap reveals that windage loss arises from the interaction between walls and fluid rather than the dissipation with fluid itself. Finally, the model of Cf in shaft‐type gap is proposed in different Reω ranges based on numerical results, and the maximum sum of squares error of 1.02 × 10−5 and minimal R2 of 0.969 satisfy the requirement of fitting accuracy and indicate that the fitting model can accurately predict Cf. The conclusions significantly help predict windage loss in open shaft‐type gap with axial flow, and further improve the design for generators of supercritical CO2 turbine‐alternator‐compressor unit.

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CO2-based mixtures as working fluids for geothermal turbines.

Cited by 13 publications

References 4 publications

Power Generation with Renewable Energy and Advanced Supercritical CO2 Thermodynamic Power Cycles: A Review

Power Generation with Renewable Energy and Advanced Supercritical CO2 Thermodynamic Power Cycles: A Review

New Knowledge on the Performance of Supercritical Brayton Cycle with CO2-Based Mixtures

Action mechanism of axial flow on windage loss in open shaft‐type gap with CO₂

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CO2-based mixtures as working fluids for geothermal turbines.

Cited by 13 publications

References 4 publications

Power Generation with Renewable Energy and Advanced Supercritical CO2 Thermodynamic Power Cycles: A Review

Power Generation with Renewable Energy and Advanced Supercritical CO2 Thermodynamic Power Cycles: A Review

New Knowledge on the Performance of Supercritical Brayton Cycle with CO2-Based Mixtures

Action mechanism of axial flow on windage loss in open shaft‐type gap with CO2

Contact Info

Product

Resources

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Action mechanism of axial flow on windage loss in open shaft‐type gap with CO₂