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2 pages, 158 KiB

Open AccessEditorial

Recent Advancement of Thermal Fluid Engineering in the Supercritical CO₂ Power Cycle

by Jeong Ik Lee and David Sanchez

Appl. Sci. 2020, 10(15), 5350; https://doi.org/10.3390/app10155350 - 3 Aug 2020

Cited by 1 | Viewed by 2148

Abstract

The supercritical CO₂ (S-CO₂) power cycle is an emerging energy technology that has potential to revolutionize the conversion process of heat to mechanical or electric power [...] Full article

(This article belongs to the Special Issue Recent Advancement of Thermal Fluid Engineering in the Supercritical CO₂ Power Cycle)

Research

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20 pages, 8580 KiB

Open AccessArticle

Mean-Line Design of a Supercritical CO₂ Micro Axial Turbine

by Salma I. Salah, Mahmoud A. Khader, Martin T. White and Abdulnaser I. Sayma

Appl. Sci. 2020, 10(15), 5069; https://doi.org/10.3390/app10155069 - 23 Jul 2020

Cited by 29 | Viewed by 5021

Abstract

Supercritical carbon dioxide (sCO

_{2}

) power cycles are promising candidates for concentrated-solar power and waste-heat recovery applications, having advantages of compact turbomachinery and high cycle efficiencies at heat-source temperature in the range of 400 to 800

^{\circ}

C. However, for distributed-scale systems [...] Read more.

Supercritical carbon dioxide (sCO

_{2}

) power cycles are promising candidates for concentrated-solar power and waste-heat recovery applications, having advantages of compact turbomachinery and high cycle efficiencies at heat-source temperature in the range of 400 to 800

^{\circ}

C. However, for distributed-scale systems (0.1–1.0 MW) the choice of turbomachinery type is unclear. Radial turbines are known to be an effective machine for micro-scale applications. Alternatively, feasible single-stage axial turbine designs could be achieved allowing for better heat transfer control and improved bearing life. Thus, the aim of this study is to investigate the design of a single-stage 100 kW sCO

_{2}

axial turbine through the identification of optimal turbine design parameters from both mechanical and aerodynamic performance perspectives. For this purpose, a preliminary design tool has been developed and refined by accounting for passage losses using loss models that are widely used for the design of turbomachinery operating with fluids such as air or steam. The designs were assessed for a turbine that runs at inlet conditions of 923 K, 170 bar, expansion ratio of 3 and shaft speeds of 150k, 200k and 250k RPM respectively. It was found that feasible single-stage designs could be achieved if the turbine is designed with a high loading coefficient and low flow coefficient. Moreover, a turbine with the lowest degree of reaction, over a specified range from 0 to 0.5, was found to achieve the highest efficiency and highest inlet rotor angles. Full article

(This article belongs to the Special Issue Recent Advancement of Thermal Fluid Engineering in the Supercritical CO₂ Power Cycle)

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22 pages, 1143 KiB

Open AccessArticle

Potential of Supercritical Carbon Dioxide Power Cycles to Reduce the Levelised Cost of Electricity of Contemporary Concentrated Solar Power Plants

by Francesco Crespi, David Sánchez, Gonzalo S. Martínez, Tomás Sánchez-Lencero and Francisco Jiménez-Espadafor

Appl. Sci. 2020, 10(15), 5049; https://doi.org/10.3390/app10155049 - 22 Jul 2020

Cited by 30 | Viewed by 3342

Abstract

This paper provides an assessment of the expected Levelised Cost of Electricity enabled by Concentrated Solar Power plants based on Supercritical Carbon Dioxide (sCO

_{2}

) technology. A global approach is presented, relying on previous results by the authors in order to ascertain [...] Read more.

This paper provides an assessment of the expected Levelised Cost of Electricity enabled by Concentrated Solar Power plants based on Supercritical Carbon Dioxide (sCO

_{2}

) technology. A global approach is presented, relying on previous results by the authors in order to ascertain whether these innovative power cycles have the potential to achieve the very low costs of electricity reported in the literature. From a previous thermodynamic analysis of sCO

_{2}

cycles, three layouts are shortlisted and their installation costs are compared prior to assessing the corresponding cost of electricity. Amongst them, the Transcritical layout is then discarded due to the virtually impossible implementation in locations with high ambient temperature. The remaining layouts, Allam and Partial Cooling are then modelled and their Levelised Cost of Electricity is calculated for a number of cases and two different locations in North America. Each case is characterised by a different dispatch control scheme and set of financial assumptions. A Concentrated Solar Power plant based on steam turbine technology is also added to the assessment for the sake of comparison. The analysis yields electricity costs varying in the range from 8 to over 11 ¢/kWh, which is near but definitely not below the 6 ¢/kWh target set forth by different administrations. Nevertheless, in spite of the results, a review of the conservative assumptions adopted in the analysis suggests that attaining costs substantially lower than this is very likely. In other words, the results presented in this paper can be taken as an upper limit of the economic performance attainable by Supercritical Carbon Dioxide in Concentrated Solar Power applications. Full article

(This article belongs to the Special Issue Recent Advancement of Thermal Fluid Engineering in the Supercritical CO₂ Power Cycle)

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16 pages, 10183 KiB

Open AccessArticle

Design and Performance Analysis of a Supercritical Carbon Dioxide Heat Exchanger

by Han Seo, Jae Eun Cha, Jaemin Kim, Injin Sah and Yong-Wan Kim

Appl. Sci. 2020, 10(13), 4545; https://doi.org/10.3390/app10134545 - 30 Jun 2020

Cited by 13 | Viewed by 4038

Abstract

This paper presents a preliminary design and performance analysis of a supercritical CO₂ (SCO₂) heat exchanger for an SCO₂ power generation system. The purpose of designing a SCO₂ heat exchanger is to provide a high-temperature and high-pressure heat [...] Read more.

This paper presents a preliminary design and performance analysis of a supercritical CO₂ (SCO₂) heat exchanger for an SCO₂ power generation system. The purpose of designing a SCO₂ heat exchanger is to provide a high-temperature and high-pressure heat exchange core technology for advanced SCO₂ power generation systems. The target outlet temperature and pressure for the SCO₂ heat exchanger were 600 °C and 200 bar, respectively. A tubular type with a staggered tube bundle was selected as the SCO₂ heat exchanger, and liquefied petroleum gas (LPG) and air were selected as heat sources. The design of the heat exchanger was based on the material selection and available tube specification. Preliminary performance evaluation of the SCO₂ heat exchanger was conducted using an in-house code, and three-dimensional flow and thermal stress analysis were performed to verify the tube’s integrity. The simulation results showed that the tubular type heat exchanger can endure high-temperature and high-pressure conditions under an SCO₂ environment. Full article

(This article belongs to the Special Issue Recent Advancement of Thermal Fluid Engineering in the Supercritical CO₂ Power Cycle)

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26 pages, 6120 KiB

Open AccessFeature PaperArticle

Investigation of a Radial Turbine Design for a Utility-Scale Supercritical CO₂ Power Cycle

by Tala El Samad, Joao Amaral Teixeira and John Oakey

Appl. Sci. 2020, 10(12), 4168; https://doi.org/10.3390/app10124168 - 17 Jun 2020

Cited by 8 | Viewed by 3825

Abstract

This paper presents the design procedure and analysis of a radial turbine design for a mid-scale supercritical CO

_{2}

power cycle. Firstly, thermodynamic analysis of a mid-range utility-scale cycle, similar to that proposed by NET Power, is established while lowering the turbine inlet [...] Read more.

This paper presents the design procedure and analysis of a radial turbine design for a mid-scale supercritical CO

_{2}

power cycle. Firstly, thermodynamic analysis of a mid-range utility-scale cycle, similar to that proposed by NET Power, is established while lowering the turbine inlet temperature to 900

^{\circ}

C in order to remove cooling complexities within the radial turbine passages. The cycle conditions are then considered for the design of a 100 MW

_{t h}

power scale turbine by using lower and higher fidelity methods. A 510 mm diameter radial turbine, running at 21,409 rpm, capable of operating within a 5% range of the required cycle conditions, is designed and presented. Results from computational fluid dynamics simulations indicate the loss mechanisms responsible for the low-end value of the turbine total-to-total efficiency which is 69.87%. Those include shock losses at stator outlet, incidence losses at rotor inlet, and various mixing zones within the passage. Mechanical stress calculations show that the current blade design flow path of the rotor experiences tolerable stress values, however a more detailed re-visitation of disc design is necessitated to ensure an adequate safety margin for given materials. A discussion of the enabling technologies needed for the adoption of a mid-size radial turbine is given based on current advancements in seals, bearings, and materials for supercritical CO

_{2}

cycles. Full article

(This article belongs to the Special Issue Recent Advancement of Thermal Fluid Engineering in the Supercritical CO₂ Power Cycle)

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20 pages, 9290 KiB

Open AccessArticle

Aerodynamic Optimization Design of a 150 kW High Performance Supercritical Carbon Dioxide Centrifugal Compressor without a High Speed Requirement

by Dongbo Shi and Yonghui Xie

Appl. Sci. 2020, 10(6), 2093; https://doi.org/10.3390/app10062093 - 19 Mar 2020

Cited by 10 | Viewed by 6384

Abstract

Supercritical carbon dioxide (S-CO₂) Brayton cycle technology has the advantages of excellent energy density and heat transfer. The compressor is the most critical and complex component of the cycle. Especially, in order to make the system more reliable and economical, the [...] Read more.

Supercritical carbon dioxide (S-CO₂) Brayton cycle technology has the advantages of excellent energy density and heat transfer. The compressor is the most critical and complex component of the cycle. Especially, in order to make the system more reliable and economical, the design method of a high efficiency compressor without a high speed requirement is particularly important. In this paper, thermodynamic design software of a S-CO₂ centrifugal compressor is developed. It is used to design the 150 kW grade S-CO₂ compressor at the speed of 40,000 rpm. The performance of the initial design is carried out by a 3-D aerodynamic analysis. The aerodynamic optimization includes three aspects: numerical calculation, design software and the flow part geometry parameters. The aerodynamic performance and the off-design performance of the optimal design are obtained. The results show that the total static efficiency of the compressor is 79.54%. The total pressure ratio is up to 1.9. The performance is excellent, and it can operate normally within the mass flow rate range of 5.97 kg/s to 11.05 kg/s. This research provides an intelligent and efficient design method for S-CO₂ centrifugal compressors with a low flow rate and low speed, but high pressure ratio. Full article

(This article belongs to the Special Issue Recent Advancement of Thermal Fluid Engineering in the Supercritical CO₂ Power Cycle)

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18 pages, 8928 KiB

Open AccessArticle

Numerical Investigation on Aerodynamic Performance of SCO₂ and Air Radial-Inflow Turbines with Different Solidity Structures

by Yuqi Wang, Jinxing Li, Di Zhang and Yonghui Xie

Appl. Sci. 2020, 10(6), 2087; https://doi.org/10.3390/app10062087 - 19 Mar 2020

Cited by 16 | Viewed by 3551

Abstract

Supercritical carbon dioxide (SCO₂) is of great use in miniature power systems. It obtains the characteristics of high density and low viscosity, which makes it possible to build a compact structure for turbomachinery. For a turbine design, an important issue is [...] Read more.

Supercritical carbon dioxide (SCO₂) is of great use in miniature power systems. It obtains the characteristics of high density and low viscosity, which makes it possible to build a compact structure for turbomachinery. For a turbine design, an important issue is to figure out the appropriate solidity of the rotor. The objective of this research is to present the aerodynamic performance and provide the design reference for SCO₂ and air radial-inflow turbines considering different solidity structures. For the low solidity case of SCO₂ turbine, new splitter structures are proposed to improve its performance. The automatic design and simulation process are established by batch modes in MATLAB. The numerical investigation is based on a 3D viscous compressible N-S equation and the actual fluid property of SCO₂ and air. The distributions of flow parameters are first presented. Rotor blade load and aerodynamic force are then thoroughly analyzed and the aerodynamic performances of all cases are obtained. The SCO₂ turbine has larger power capacity and higher efficiency while the performance of the air turbine is less affected by rotor solidity. For both SCO₂ and air, small solidity can cause the unsatisfactory flow condition at the inlet and the shroud section of the rotor, while large solidity results in the aerodynamic loss at the trailing edge of rotor blade and the hub of rotor outlet. A suction side offset splitter can greatly improve the performance of the low solidity SCO₂ turbine. Full article

(This article belongs to the Special Issue Recent Advancement of Thermal Fluid Engineering in the Supercritical CO₂ Power Cycle)

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16 pages, 29040 KiB

Open AccessArticle

Performance Analysis of the Supercritical Carbon Dioxide Re-compression Brayton Cycle

by Mohammad Saad Salim, Muhammad Saeed and Man-Hoe Kim

Appl. Sci. 2020, 10(3), 1129; https://doi.org/10.3390/app10031129 - 7 Feb 2020

Cited by 18 | Viewed by 2988

Abstract

This paper presents performance analysis results on supercritical carbon dioxide (

s C O_{2}

) re-compression Brayton cycle. Monthly exergy destruction analysis was conducted to find the effects of different ambient and water temperatures on the performance of the system. The results [...] Read more.

This paper presents performance analysis results on supercritical carbon dioxide (

s C O_{2}

) re-compression Brayton cycle. Monthly exergy destruction analysis was conducted to find the effects of different ambient and water temperatures on the performance of the system. The results reveal that the gas cooler is the major source of exergy destruction in the system. The total exergy destruction has the lowest value of

390.1 kW

when the compressor inlet temperature is near the critical point (at

35

°C) and the compressor outlet pressure is comparatively low (

24 MPa

). The optimum mass fraction (x) and efficiency of the cycle increase with turbine inlet temperature. The highest efficiency of 49% is obtained at the mass fraction of x = 0.74 and turbine inlet temperature of 700 °C. For predicting the cost of the system, the total heat transfer area coefficient (

U A_{T o t a l}

) and size parameter (SP) are used. The

U A_{T o t a l}

value has the maximum for the split mass fraction of 0.74 corresponding to the maximum value of thermal efficiency. The SP value for the turbine is 0.212 dm at the turbine inlet temperature of 700 °C and it increases with increasing turbine inlet temperature. However the SP values of the main compressor and re-compressor increase with increasing compressor inlet temperature. Full article

(This article belongs to the Special Issue Recent Advancement of Thermal Fluid Engineering in the Supercritical CO₂ Power Cycle)

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27 pages, 11388 KiB

Open AccessFeature PaperArticle

A Supercritical CO₂ Waste Heat Recovery System Design for a Diesel Generator for Nuclear Power Plant Application

by Jin Ki Ham, Min Seok Kim, Bong Seong Oh, Seongmin Son, Jekyoung Lee and Jeong Ik Lee

Appl. Sci. 2019, 9(24), 5382; https://doi.org/10.3390/app9245382 - 9 Dec 2019

Cited by 5 | Viewed by 3191

Abstract

After the Fukushima accident, the importance of an emergency power supply for a nuclear power plant has been emphasized more. In order to maximize the performance of the existing emergency power source in operating nuclear power plants, adding a waste heat recovery system [...] Read more.

After the Fukushima accident, the importance of an emergency power supply for a nuclear power plant has been emphasized more. In order to maximize the performance of the existing emergency power source in operating nuclear power plants, adding a waste heat recovery system for the emergency power source is suggested for the first time in this study. In order to explore the possibility of the idea, a comparison of six supercritical carbon dioxide (S-CO₂) power cycle layouts recovering waste heat from a 7.2 MW alternate alternating current diesel generator (AAC DG) is first presented. The diesel engine can supply two heat sources to the waste heat recovery system: one from exhaust gas and the other from scavenged air. Moreover, a sensitivity study of the cycles for different design parameters is performed, and the thermodynamic performances of the various cycles were evaluated. The main components, including turbomachinery and heat exchangers, are designed with in-house codes which have been validated with experiment data. Based on the designed cycle and components, the bottoming S-CO₂ cycle performance under part load operating condition of AAC DG is analyzed by using a quasi-steady state cycle analysis method. It was found that a partial heating cycle has relatively higher net produced work while enjoying the benefit of a simple layout and smaller number of components. This study also revealed that further waste heat can be recovered by adjusting the flow split merging point of the partial heating cycle. Full article

(This article belongs to the Special Issue Recent Advancement of Thermal Fluid Engineering in the Supercritical CO₂ Power Cycle)

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