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Supercritical carbon dioxide (SCO2) centrifugal compressor is a key component of a closed Brayton cycle system based on SCO2. A comprehensive understanding of the loss mechanism within the compressor is vital for its optimized design. However, the physical properties of SCO2 are highly nonlinear near the critical point, and the internal flow of the compressor is closely related to its properties, which inevitably influences the generation of aerodynamic losses within the compressor. This paper presents a comprehensive investigation of the compressor's loss mechanism with an experimentally validated numerical method. The real gas model of CO2 embodied in the Reynolds-Averaged Navier-Stokes (RANS) model was used for the study. Firstly, the numerical simulation method was validated against the experimental results of Sandia SCO2 compressor. Secondly, performance and loss distribution of the compressor were compared among three fluids including SCO2, ideal CO2 (ICO2) and ideal air (IAir). The results showed that the performance of SCO2 was comparable to IAir under low flow coefficient, however markedly inferior to the other two fluids at near choke condition. Loss distribution among the three fluids was distinctive. In the impeller, SCO2 was the most inefficient, followed by ICO2 and IAir. The discrepancies were magnified as the flow coefficient increased. This is due to a stronger Blade-to-Blade pressure gradient that intensifies boundary layer accumulation on walls of the shroud/hub. Furthermore, owing to the reduced sonic speed of SCO2, a shock wave appears earlier at the throat region and SCO2 encounters more intense boundary layer separation. [ABSTRACT FROM AUTHOR]

With the planned future reliance on variable renewable energy, the ability to store energy for prolonged time periods will be required to reduce the disruption of market fluctuations. This paper presents a method to analyze a hybrid liquid-oxygen (LOx) storage/direct-fired supercritical carbon dioxide (sCO2) power cycle and optimize the economic performance over a diverse range of scenarios. The system utilizes a modified version of the NET Power process to produce energy when energy demand exceeds the supply while displacing much of the cost of the air separation unit (ASU) energy requirements through cryogenic storage of oxygen. The model uses marginal cost of energy data to determine the optimal times to charge and discharge the system over a given scenario. The model then applies ramp rates and other time-dependent factors to generate an economic model for the system without storage considerations. The size of the storage system is then applied to create a realistic model of the plant operation. From the real plant operation model, the amount of energy charged and discharged, the capital expenditures (CAPEX) of each system, energy costs and revenue and other parameters can be calculated. The economic parameters are then combined to calculate the net present value (NPV) of the system for the given scenario. The model was then run through the SMPSO genetic algorithm in Python for a variety of geographic regions and large-scale scenarios (high solar penetration) to maximize the NPV based on multiple parameters for each subsystem. The LOx storage requirements will also be discussed. [ABSTRACT FROM AUTHOR]

Molten salt and supercritical carbon dioxide (sCO2) are considered to be one of the most promising combined heat transfer refrigerants for third-generation solar thermal power generation. To evaluate the potential of chloride salts and carbonates in third-generation solar thermal power generation, this paper uses molten salts and sCO2 as the working media of printed circuit board heat exchangers (PCHE), and uses numerical simulation to study the heat transfer and friction of PCHE channels with different molten salts and sCO2, and establishes predictive correlations respectively. A local heat transfer and friction study was conducted on the sCO2 side of the airfoil channel, and it was found that the inlet mass flow rate has a significant impact on it, while the inlet temperature has a relatively small impact. A comprehensive comparison was made between the heat transfer and friction of two molten salts, and the comprehensive performance of chloride salts was 70%–80% higher than that of carbonates. The results indicate that the potential of chloride salts in third-generation solar thermal power generation is much greater than that of carbonates. [ABSTRACT FROM AUTHOR]

The objective of this paper was to study the sCO2 cycle as a waste heat recovery system for a 180 kW biogas engine. The research methodology adopted was numerical simulations through two models built in different programs: Aspen HYSYS and GT Suite. The models were used to optimize the design and thermodynamic parameters of a CO2 cycle in terms of system power, system efficiency, expander, and compressor efficiency. Depending on the objective function, the sCO2 cycle could provide additional power ranging from 27.9 to 11.3 kW. Based on the calculation performed, "Recuperated cycle at maximum power" was selected for further investigation. The off-design analysis of the system revealed the optimum operating point. The authors designed the preliminary dimensions of the turbomachinery, i.e., the rotor dimension is 16 mm, which will rotate at 100,000 rpm. [ABSTRACT FROM AUTHOR]

A Thermoelectric Conversion System (TECS) with SCO2 as the circulating mass can effectively mitigate the fuel heat sink and electrical energy shortage problems of hypersonic vehicles. However, there is still a lack of research on the use of SCO2 in the harsh thermal conditions in scramjet. In this paper, the heat transfer mechanism of SCO2 in rectangular cooling tubes are numerically analyzed for the first time based on the actual working environment of scramjet. The effects of uneven heat flux (q) axial and circumferential allocations and circumferential and axial tilting of the tube are innovatively considered. Meanwhile, we analyze the heat transfer mechanism of SCO2 under different operating parameters. The results show that the uneven allocation of axial q can suppress the heat transfer deterioration (HTD), and the overall heat transfer coefficient (HTC) can be increased by 11.68 % when the q allocation is Gaussian. The increase of the tube inclination angle can improve its heat transfer performance, and the local HTC can be increased by up to 5.64 % when θ2 = 180°.Increasing the mass flow rate (G) and inlet temperature (Tin) can increase the overall HTC of the tube. This paper can provide guidance for the design and improvement of TECS.

Supercritical CO2 (SCO2) is regarded as a promising supplementary coolant for traditional regenerative cooling at extremely high flight speed (Ma ≥8) due to its superior heat and mass transfer capability. Using sCO2 as the coolant, mini-ribs is introduced to the rectangular regenerative cooling channel to solve the difficulties in transferring enough heat from near walls to core mainstream at a heat flux of 5 MW/m2 in this paper. With the thermophysical properties near the supercritical point interpolated in the solver, flow structures and heat transfer performance in the cooling channels are obtained using a validated k-ω SST turbulence model. Effects of pitch ratios, channel materials and acceleration and buoyancy effects are also investigated in terms of the local bulk heat transfer coefficients, Fanning friction factors and entropy generation numbers by heat transfer and fluid flow. Overall, the existing of mini-ribs improves the heat transfer coefficient and reduces the entropy number by heat transfer at the cost of the increased fluid friction and the corresponding entropy number. Compared with the smooth channel, the overall enhanced factor can reach 1.73 with an overall thermal performance factor of 1.43 and the maximum wall temperature decreases by 27.57 % in the case of P/e = 10. When the solid channel material has higher thermal conductivity, it leads to a more uniform temperature distribution and lower entropy generation number by heat transfer with the enhanced transverse heat conduction within solid walls which also leads large heat transfer coefficients. Larger accelerations result in stronger heat transfer and larger fluid friction by strengthening the buoyancy effect which is more obvious when the state approach the critical point. This work provides a good reference for the application of supercritical CO2 in a regenerative cooling channel of scramjet engine at extremely high heat flux.

AIM: To evaluate the pathogenic variants of the SCO2(OMIM 604272)gene in patients with high myopia from Enshi Tujia and Miao Autonomous Prefecture of China.METHODS: A total of 384 patients with high myopia whose spherical refractive error was ≤ -6.00 D and whose axial length was ≥26.00 mm in at least one eye were recruited. DNA was extracted by the phenol-chloroform method from 5 mL of peripheral venous blood. Sanger sequencing was performed to identify pathogenic variants in exon 2 of SCO2. The detected variants were evaluated via in silico prediction software. A total of 288 people from the same district were included as the normal control cohort.RESULTS: Seven variants were detected, namely, four synonymous variants(c.201C>T/p.=, c.576C>T/p.=, c.633A>C/p.=, c.780T>C/p.=.), two missense variants(c.187A>G/p.Ile63Val, c.59G>C/p.Arg20Pro)and one nonsense variant(c.544C>T/p.Gln182*). The two missense variants were not damaging, as predicted by PolyPhen2, SIFT and Provean. The novel nonsense variant(c.544C>T/p.Gln182*)cannot be found in the 1000 Genomes Project and was not identified in 288 normal controls. Variant Taster suggested that the nonsense variant site was conserved.CONCLUSION: The newly identified nonsense mutation may be responsible for high myopia of the patients in our cohort. SCO2 is associated with high myopia, while the incidence of SCO2 variants in high myopia in this cohort was as low as 1/384; the nonsense mutation may be a scarce variant of high myopia in the Enshi Tujia and Miao Autonomous Prefecture of China.

The low-lying electronic states of ScO2 and ScO2– were studied using the SAC-CI method. The lowest six doublet states (X2B2, 12A1/22A′, 22A1, 12A2, 12B1/12A″, and 22B2) of ScO2 and the valence-bound singlet/triplet states (X1A1, 21A1/13A1, 11A2/13A2, 11B1/13B1, 11B2/13B2, and 21B2/23B2) of ScO2– were optimised, and the relative energies among these electronic states were obtained. The electron detachment energies from the X1A1 state of ScO2– to the lowest six doublet states of ScO2 and from the 13B2 state of ScO2– to the X2B2 state of ScO2 can be compared with the previous experimental photoelectron spectra of ScO2–. The vertical excitation spectra of ScO2 and ScO2– were computed. The singlet/triplet dipole-bound states (1B2(DB)/3B2(DB)) of ScO2– were found. [ABSTRACT FROM AUTHOR]

To maintain a global zero-emission policy and a high standard of living, new energy systems with higher system efficiency and net zero-emission productions need to be designed and deployed. This paper describes a novel integrated system between a direct-fired supercritical carbon dioxide (sCO2) power system with hydrogen and oxygen for zero-emission power generation and storage. sCO2 power cycles offer higher thermodynamic efficiencies than conventional gas-fired Brayton cycles. Heat is added to the system from the combustion of hydrogen and oxygen. The system consists of an electrolyzer unit and two cryogenic storage systems for hydrogen and oxygen. The proposed system is designed as a medium/long-term battery that can use excess electricity from the grid to produce hydrogen (electrolyzer) and supply to the grid (hydrogen combustion) in times of higher demand. Nitrous oxide emissions are mitigated by oxy-combustion and water separation from the post-combustion products allows for a closed-loop water cycle. The optimization of cycle parameters suggests a turbine inlet temperature of 1473 K and a pressure of 30 MPa for a specific net power output of 348 kJ/kg electrical. This results in an H2-sCO2 direct-fired power cycle efficiency of around 53 % with an overall system round-trip efficiency of up to 35 %.

The objective of this paper was to study the sCO2 cycle as a waste heat recovery system for a 180 kW biogas engine. The research methodology adopted was numerical simulations through two models built in different programs: Aspen HYSYS and GT Suite. The models were used to optimize the design and thermodynamic parameters of a CO2 cycle in terms of system power, system efficiency, expander, and compressor efficiency. Depending on the objective function, the sCO2 cycle could provide additional power ranging from 27.9 to 11.3 kW. Based on the calculation performed, “Recuperated cycle at maximum power” was selected for further investigation. The off-design analysis of the system revealed the optimum operating point. The authors designed the preliminary dimensions of the turbomachinery, i.e., the rotor dimension is 16 mm, which will rotate at 100,000 rpm.

Closed Joule-Brayton thermodynamic cycles working with carbon dioxide in supercritical conditions (sCO2) are presently receiving great attention, for their multiple attractive aspects: high energy conversion efficiency, compact size, flexibility of operation, and integration with energy storage systems. These features make the sCO2 technology interesting for several energy and industrial sectors, including renewable sources and waste heat recovery. A further promising area of application of sCO2 systems is bottoming gas turbines in combined cycles installed in off-shore platforms, where the lack of space complicates the application of steam Rankine cycles. The use of steam implies large-scale components and demands for large space availability for the plant installation; in such context, the combination of gas turbines with sCO2 cycles could open the way for developing novel combined cycles, which could be attractive for all the sectors which might take advantage from the footprint savings, the enhanced flexibility, and the fast dynamics of sCO2 systems. In this work, we investigate the thermodynamic potential of combining sCO2 cycles with an existing gas turbine for off-shore applications. We consider a midsize (25 MW) gas turbine available on the market and perform a series of thermodynamic optimizations of the sCO2 bottoming cycle to maximize the exploitation of the heat discharged by the gas turbine. We analyze four alternative configurations and include realistic technical constraints, evaluated by leveraging on the most recent technical outcomes from ongoing sCO2 research projects. A comparison is also proposed with a state-of-the-art steam Rankine cycle, in terms of system efficiency and footprint of the largest components. This study clarifies the advantages and challenges of applying sCO2 in combination with gas turbines, and it confirms the relevance of sCO2 systems for off-shore applications, calling for further technical studies in the field. [ABSTRACT FROM AUTHOR]

The use of supercritical fluids in technical applications requires an accurate knowledge of their critical points. For mixtures, these can deviate significantly and without a linear dependency from the critical points of its individual pure components. Since even small amounts of admixture can have noticeable effects, this not only concerns blends of targeted compositions, but also unintentional mixtures for example caused by impurities. Within this work, a method for the calculation of critical points is presented which focuses on numerical robustness promoting a fast and reliable generation of results. Implemented into the thermodynamic property software TREND, with its mixture modeling capabilities, the method allows a flexible combination of different equations of state and mixture models which also includes predictive approaches. Against the background of an increasing relevance of mixtures based on supercritical CO 2 (sCO 2 ) for energy applications, critical lines are calculated and compared against experimental results for selected sCO 2 -based mixtures recently considered for power plant applications. Herein, several combinations of equations of state (EoS) and mixture models are compared. Critical lines are calculated for the first time in this work with the combination of the multi-fluid mixture model with excess Gibbs energy ( g E ) models. It was found that the critical lines calculated with the combination of the multi-fluid mixture model with the g E -model COSMO-SAC yields good predictive results for the investigated CO 2 mixtures. [ABSTRACT FROM AUTHOR]

Drastic variation in the thermodynamic properties of supercritical fluids near the pseudo critical point hinders the use of commercial computational fluid dynamics (CFD) software. However, with the increase in computational abilities, along with the use of Artificial Neural Networks (ANN), turbulence heat transfer characteristics of supercritical fluids can be very accurately predicted. In the present work, heat transfer characteristics for a vertically downward flow of carbon dioxide in a pipe are studied for a wide range of heat flux and mass flux values. Firstly, six different turbulent models available in the commercial CFD software - Ansys Fluent are validated against the experimental results. The k-? Standard model with enhanced wall treatment is found to be the best-suited turbulence model. When experimental results were validated in CFD, an average error of 1% in the bulk fluid temperature and 2% in the wall temperature were recorded. Further, K-? Standard Turbulence Model is used in CFD for parametric analysis to generate the data for ANN studies. Mass flux range of 238 to 1038 kg/m2s, and heat flux range of 26 kW/m2 to 250 kW/m2 are used to generate 81,432 data samples. These samples were fed into the ANN program to develop an equation that can predict the heat transfer coefficient. It was found that ANN can predict the heat transfer coefficient for the considered range of values within the absolute average relative deviation of 2.183 %. [ABSTRACT FROM AUTHOR]

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Global power consumption is predicted to double by 2050, notably driven by the transportation and energy sectors necessitating limitations of emissions. Due to its compact turbomachinery, better thermal efficiency, and simpler layout, supercritical-CO2 cycles have received attention, with numerous variations proposed (either indirect-fired/closed cycles or direct-fired-open cycles). One technical challenge is degradation pathway quantification of turbine materials in sCO2 as selection is crucial to successfully and economically operate new plants. This requires degradation assessment in representative environments simulating the Allam cycle. Laboratory tests were conducted on a first stage turbine blade alloy, CM247, with either an environmentally resistant coating or bond coat/thermal barrier coat at one atmosphere and 800°C, with potential exposure including (O2, H2O, N2, SO2) for up to 1000 h. Weight change and metallographic measurements tracked scale development. Scanning electron microscopy/energy dispersive X-ray spectroscopy studied scales and internal precipitates. Locations of contaminant element in the CO2-rich environment were investigated. [ABSTRACT FROM AUTHOR]

Global power consumption is predicted to double by 2050, notably driven by the transportation and energy sectors necessitating limitations of emissions. Due to its compact turbomachinery, better thermal efficiency, and simpler layout, supercritical-CO2 cycles have received attention, with numerous variations proposed (either indirect-fired/closed cycles or direct-fired-open cycles). One technical challenge is degradation pathway quantification of turbine materials in sCO2 as selection is crucial to successfully and economically operate new plants. This requires degradation assessment in representative environments simulating the Allam cycle. Laboratory tests were conducted on a first stage turbine blade alloy, CM247, with either an environmentally resistant coating or bond coat/thermal barrier coat at one atmosphere and 800°C, with potential exposure including (O2, H2O, N2, SO2) for up to 1000 h. Weight change and metallographic measurements tracked scale development. Scanning electron microscopy/energy dispersive X-ray spectroscopy studied scales and internal precipitates. Locations of contaminant element in the CO2-rich environment were investigated. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the potential of supercritical carbon dioxide (sCO2), organic Rankine cycle (ORC), and thermoelectric generator (TEG) systems for application in automotive exhaust waste heat recovery (WHR) applications. More specifically, this paper focuses on heavy-duty diesel engines applications such as marine, trucks, and locomotives. The results of the simulations show that sCO2 systems are capable of recovering the highest amount of power from exhaust gases, followed by ORC systems. The sCO2 system recovered 19.5 kW at the point of maximum brake power and 10.1 kW at the point of maximum torque. Similarly, the ORC system recovered 14.7 kW at the point of maximum brake power and 7.9 kW at the point of maximum torque. Furthermore, at a point of low power and torque, the sCO2 system recovered 4.2 kW of power and the ORC system recovered 3.3 kW. The TEG system produced significantly less power (533 W at maximum brake power, 126 W at maximum torque, and 7 W at low power and torque) at all three points of interest due to the low system efficiency in comparison to sCO2 and ORC systems. From the results, it can be concluded that sCO2 and ORC systems have the biggest potential impact in exhaust WHR applications provided the availability of heat and that their level of complexity does not become prohibitive. [ABSTRACT FROM AUTHOR]

In eukaryotes, cellular respiration is driven by mitochondrial cytochrome c oxidase (CcO), an enzyme complex that requires copper cofactors for its catalytic activity. Insertion of copper into its catalytically active subunits, including COX2, is a complex process that requires metallochaperones and redox proteins including SCO1, SCO2, and COA6, a recently discovered protein whose molecular function is unknown. To uncover the molecular mechanism by which COA6 and SCO proteins mediate copper delivery to COX2, we have solved the solution structure of COA6, which reveals a coiled-coil-helix-coiled-coil-helix domain typical of redox-active proteins found in the mitochondrial inter-membrane space. Accordingly, we demonstrate that COA6 can reduce the copper-coordinating disulfides of its client proteins, SCO1 and COX2, allowing for copper binding. Finally, our determination of the interaction surfaces and reduction potentials of COA6 and its client proteins provides a mechanism of how metallochaperone and disulfide reductase activities are coordinated to deliver copper to CcO.

As the supercritical CO2 power cycle develops and the component technologies mature, there is still a need to reduce the associated capital and operating costs to maintain a competitive levelized cost of electricity (LCOE) in order to enter the market. When considering concentrating solar power (CSP) coupled with an sCO2 power block and sensible thermal storage, the technology presents a clean source for utility-scale power generation to support baseload or peak-load electrical demand. However, the LCOE of the technology is still considered higher than the competing technologies and should be reduced to better compete in the market; 2030 targets for dispatchable solar plants are 5¢/kWh for baseload CSP and 10¢/kWh for peaker plants, as set by the United States Department of Energy. In response to this need, this study is targeting improvements in the power cycle precooler to reduce power block contribution to LCOE. This study considers a dry cooler, as CSP plants are sensitive to water consumption because many installations are slated for remote or arid locations where solar irradiance is very high, but water is scarce. Furthermore, the power block footprint for an sCO2 system is quite compact, especially as compared to a steam cycle. Therefore, there is interest in installing a more compact dry cooler that is proportional to the reduced footprint sCO2 power block, while conventional dry coolers are an order of magnitude larger. The competing goals of size, performance, and cost were considered in this study to develop a compact dry cooler that can easily be packaged with the power block, significantly reducing the installation and transport cost compared to the current state of the art, while maintaining or improving upon the heat transfer performance and impact on plant LCOE. This paper details the high-level findings of a large dry cooler sensitivity study for design point selection, design of the compact dry cooler, expected year-round performance for the dry cooler and the power cycle, and the predicted LCOE for a 30-year plant life. It was found that an aluminum heat exchanger core can be suitably designed to meet the pressure and temperature requirements for a precooler in an sCO2 recompression Brayton cycle. The dry cooler assembly was found to have improved heat transfer performance, allowing for increased cycle efficiencies and a reduced plant LCOE. When coupled with a centrifugal blower and compact transition duct, the dry cooler assembly was able to reduce the installation footprint by over 50%. [ABSTRACT FROM AUTHOR]

Mitochondrial disorders represent a heterogeneous group of genetic disorders with variations in severity and clinical outcomes, mostly characterized by respiratory chain dysfunction and abnormal mitochondrial function. More specifically, mutations in the human SCO2 gene, encoding the mitochondrial inner membrane Sco2 cytochrome c oxidase (COX) assembly protein, have been implicated in the mitochondrial disorder fatal infantile cardioencephalomyopathy with COX deficiency. Since an effective treatment is still missing, a protein replacement therapy (PRT) was explored using protein transduction domain (PTD) technology. Therefore, the human recombinant full-length mitochondrial protein Sco2, fused to TAT peptide (a common PTD), was produced (fusion Sco2 protein) and successfully transduced into fibroblasts derived from a SCO2/COX-deficient patient. This PRT contributed to effective COX assembly and partial recovery of COX activity. In mice, radiolabeled fusion Sco2 protein was biodistributed in the peripheral tissues of mice and successfully delivered into their mitochondria. Complementary to that, an mRNA-based therapeutic approach has been more recently considered as an innovative treatment option. In particular, a patented, novel PTD-mediated IVT-mRNA delivery platform was developed and applied in recent research efforts. PTD-IVT-mRNA of full-length SCO2 was successfully transduced into the fibroblasts derived from a SCO2/COX-deficient patient, translated in host ribosomes into a nascent chain of human Sco2, imported into mitochondria, and processed to the mature protein. Consequently, the recovery of reduced COX activity was achieved, thus suggesting the potential of this mRNA-based technology for clinical translation as a PRT for metabolic/genetic disorders. In this review, such research efforts will be comprehensibly presented and discussed to elaborate their potential in clinical application and therapeutic usefulness. [ABSTRACT FROM AUTHOR]

• An innovative stand-alone C3MR LNG production combined with a power generation cycle. • Power generation system including Brayton cycle- Combined SCO2 Regeneration − ORC. • Energy, Exergy, Exergoeconomic, and Exergoenvironmental analysis based on Life Cycle Assessment. • Using machine learning for estimation of 4E objective function to reduce computation time. • The optimal solution is 45.14 % for ψ tot , 4.01 $/s for C ̇ total , 25.64 mPts/s for B ̇ total , and 153.16 kg/s for m ̇ LNG . This paper presents a novel self-contained liquefied natural gas (LNG) system for offshore natural gas extraction. The system combines a C3MR LNG process with mixed refrigerant and propane precooling cycles, integrated with a power generation system encompassing a gas cycle, supercritical carbon dioxide regeneration, and organic Rankine cycles. Utilizing Aspen Plus and the Peng-Robinson equation of state, the system is rigorously simulated. The study includes energetic, exergetic, exergoeconomic, and exergoenvironmental (4E) assessments, along with parametric studies to evaluate the influence of key parameters on objective functions. A genetic algorithm approach with four objective functions is employed to optimize system parameters. The exergoeconomic analysis shows that roughly 9% of the total cost rate associated with components refers to the power generation system, whereas 91% refers to the C3MR cycle. However, the exergoenvironmental analysis indicates that more than 57% of the total environmental impact rate associated with the components refers to the power generation system, while the remaining 43% refers to C3MR. The sensitivity analysis revealed the top five sensitive system parameters. Based on the multi-objective optimization, it was discussed that these parameters are: (a) hot inlet-cold outlet temperature difference of regenerator1 at 43 ° C , (b) air compressor isentropic efficiency at 90%, (c) MR compressors isentropic efficiency at 90%, (d) gas turbine isentropic efficiency at 90%, and (e) SCO2 turbine isentropic efficiency at 92%. Total ecergetic efficiency has the biggest share in the total improvement at 30.73%, followed by total environmental impact at 14.13%, total cost rate at 11.66% and LNG production rate at 0.57%. [ABSTRACT FROM AUTHOR]

The potential clinical applications of the powerful in vitro-transcribed (IVT)-mRNAs, to restore defective protein functions, strongly depend on their successful intracellular delivery and transient translation through the development of safe and efficient delivery platforms. In this study, an innovative (international patent-pending) methodology was developed, combining the IVT-mRNAs with the protein transduction domain (PTD) technology, as an efficient delivery platform. Based on the PTD technology, which enables the intracellular delivery of various cargoes intracellularly, successful conjugation of a PTD to the IVT-mRNAs was achieved and evaluated by band-shift assay and NMR spectroscopy. In addition, the PTD-IVT-mRNAs were applied and evaluated in two protein-disease models, including the mitochondrial disorder fatal infantile cardioencephalomyopathy and cytochrome c oxidase (COX) deficiency (attributed to SCO2 gene mutations) and β-thalassemia. The PTD-IVT-mRNA of SCO2 was successfully transduced and translated to the corresponding Sco2 protein inside the primary fibroblasts of a SCO2/COX-deficient patient, whereas the PTD-IVT-mRNA of β-globin was transduced and translated in bone marrow cells, derived from three β-thalassemic patients. The transducibility and the structural stability of the PDT-IVT-mRNAs, in both cases, were confirmed at the RNA and protein levels. We propose that our novel delivery platform could be clinically applicable as a protein therapy for metabolic/genetic disorders.

In the open literature, there is no clear guidance for design procedure on the number or where best position the splitter leading-edge to improved performance in the radial compressor. A surrogate-based optimization of multiple-splitters radial compressor has been conducted for solar hybrid microturbine in the present studies. Also, the impact of the multiple-splitters leading-edge position on the rotor radial compressor is demonstrated. The radial compressor is compared using air and supercritical carbondioxide (sCO2) as the working fluid. The optimization problem is solved by applying the surrogate or response surface model using the radial basis function network (RBFN) from the opensource package in the Julia programming language environment. Starting from 65 data points from DoE based on the optimum Latin-hypercube, the optimum candidate design can be predicted with CFD and FE analysis. The results show that for air radial compressors, the optimum position of the small-splitter leading edge is 20% from the outlet rotor, and for the middle-splitter leading position at around 30% from the inlet rotor. Unlike air radial compressors, the sCO2 radial compressor has the optimum leading-edge position for the middle splitter around 60% from the inlet rotor, and the small splitters are around 30% from the outlet rotor. Finally, compared between the non-splitter and multiple-splitter designs, the total-to-total efficiency at the same pressure ratio is improved by around 2.30% for air radial compressor and 2.25% for sCO2 radial compressor. Meanwhile, the operating range is increased by 29.0% for air radial compressors and 18.0% for sCO2 radial compressors.

Within this study, the blade shape of a large-scale axial turbine operating with sCO2 blended with dopants is optimized using an integrated aerodynamic-structural three-dimensional (3D) numerical model, whereby the optimization aims at maximizing the aerodynamic efficiency whilst meeting a set of stress constraints to ensure safe operation. Specifically, three candidate mixtures are considered, namely, CO2 blended with titanium tetrachloride (TiCl4), hexafluorobenzene (C6F6), or sulfur dioxide (SO2), where the selected blends and boundary conditions are defined by the EU project, SCARABEUS. A single passage axial turbine numerical model is setup and applied to the first stage of a large-scale multistage axial turbine design. The aerodynamic performance is simulated using a 3D steady-state viscous computational fluid dynamic (CFD) model while the blade stress distribution is obtained from a static structural finite element analysis simulation (FEA). A genetic algorithm is used to optimize parameters defining the blade angle and thickness distributions along the chord line while a surrogate model is used to provide fast and reliable model predictions during optimization using a genetic aggregation response surface. The uncertainty of the surrogate model, represented by the difference between the surrogate model results and the CFD/FEA model results, is evaluated using a set of verification points and is found to be less than 0.3% for aerodynamic efficiency and 1% for both the mass-flow rate and the maximum equivalent stresses. The comparison between the final optimized blade cross section has shown some common trends in optimizing the blade design by decreasing the stator and rotor trailing edge thickness, increasing the stator thickness near the trailing edge, and decreasing the rotor thickness near the trailing edge and decreasing the rotor outlet angle. Further investigations of the loss breakdown of the optimized and reference blade designs are presented to highlight the role of the optimization process in reducing aerodynamic losses. It has been noted that the performance improvement achieved through shape optimization is mainly due to decreasing the endwall losses with both the stator and rotor passages. [ABSTRACT FROM AUTHOR]

This paper reports numerical studies of an Elasto-Hydrodynamic (EHD) seal, which is being developed for supercritical CO2 (sCO2) turbomachinery applications. Current sCO2 turbomachinery suffers from high leakage rates, which is creating a major roadblock to the full realization of sCO2 power technology. The high leakage rates not only penalize the efficiencies but also create environmental concerns due to greenhouse effects caused by the increased CO2 discharge to the atmosphere. The proposed EHD seal needs to work at elevated pressures (10–35 MPa) and temperatures (350–700 °C) with low leakage and minimal wear. The unique mechanism of the EHD seal provides a self-regulated constriction effect to restrict the flow without substantial material contact, thereby minimizing leakage and wear. This work utilizes a physics-based modeling approach. The flow through the gradually narrowing seal clearance is modeled by the well-known Reynolds equation in EHD lubrication theory, while the deformation of the seal is modeled by using the governing equations of three-dimensional solid mechanics. As for the solution methodology, COMSOL's Thin-Film Flow and Solid Mechanics modules were employed with their powerful capabilities. The numerical results were presented and discussed. It was observed that the Reynolds equation fully coupled with the surface deformation was able to successfully capture the constriction effect. The maximum and minimum leakages were calculated to be 2.25 g/s and 0.1 g/s at P = 5.5 MPa and P = 11 MPa for the design seal, respectively. It was interesting to observe that the seal leakage followed a quadratic trend with increasing pressure differential, which can become advantageous for high-pressure applications such as sCO2 power generation technology. [ABSTRACT FROM AUTHOR]

Supercritical CO 2 is recognized as a promising working fluid for next-generation of high temperature power cycles. Nevertheless, the use of CO 2 mixtures with heavier dopants is emerging as a promising alternative to supercritical CO 2 cycles in the recent years for air-cooled systems in hot environments. Accordingly, this work presents an experimental campaign to assess the thermodynamic behaviour of the CO 2 +SiCl 4 mixture to be used as working fluid for high-temperature applications, conducted in the laboratories of CTP Mines Paris PSL. At first, bubble conditions of the mixture are measured in a variable volume cell (PVT technique), then liquid densities are measured with a vibrating tube densimeter, for molar composition in the range between 70 % and 90 % of CO 2. The Peng Robinson EoS was fine-tuned on the bubble points obtained, resulting in a satisfactory accuracy level. Finally, a non-conventional methodology has been developed to measure bubble points with the vibrating tube densimeter, whose results are consistent with the VLE data obtained with the standard PVT technique. Thermodynamic analysis in next-generation concentrated solar power plant, at 700 °C turbine inlet, confirms the mixture overcomes 50 % thermal efficiency, providing +4.2 % net electrical output over pure supercritical CO 2 at equal thermal power from the solar field. • Carbon dioxide/Silicon Tetrachloride mixture is proposed as innovative working fluid. • Bubble points and liquid densities of the mixture are experimentally obtained. • The experimental data are used for the fine-tuning of the equation of state. • The thermodynamic efficiency of the mixture is simulated in next-generation CSP plant. • The mixture enables +2 % electric efficiency gain compared to pure sCO2. [ABSTRACT FROM AUTHOR]

Mutations in genes encoding cytochrome c oxidase (mitochondrial complex IV) subunits and assembly factors [e.g., synthesis of cytochrome c oxidase 2 (SCO2)] are linked to severe metabolic syndromes. Notwithstanding that SCO2 is under transcriptional control of tumor suppressor p53, the role of mitochondrial complex IV dysfunction in cancer metabolism remains obscure. Herein, we demonstrate that the loss of SCO2 in HCT116 colorectal cancer cells leads to significant metabolic and signaling perturbations. Specifically, abrogation of SCO2 increased NAD+ regenerating reactions and decreased glucose oxidation through citric acid cycle while enhancing pyruvate carboxylation. This was accompanied by a reduction in amino acid levels and the accumulation of lipid droplets. In addition, SCO2 loss resulted in hyperactivation of the insulin-like growth factor 1 receptor (IGF1R)/AKT axis with paradoxical downregulation of mTOR signaling, which was accompanied by increased AMP-activated kinase activity. Accordingly, abrogation of SCO2 expression appears to increase the sensitivity of cells to IGF1R and AKT, but not mTOR inhibitors. Finally, the loss of SCO2 was associated with reduced proliferation and enhanced migration of HCT116 cells. Collectively, herein we describe potential adaptive signaling and metabolic perturbations triggered by mitochondrial complex IV dysfunction. [ABSTRACT FROM AUTHOR]

Superior performance and compactness of supercritical CO2 power cycles are encouraging researchers to explore them for waste heat recovery (WHR) applications. This paper presents a comprehensive thermodynamic analysis of a dual recuperated dual expansion cycle utilizing industrial waste heat. The proposed cycle incorporates two recuperators and two turbines with a single compressor. The influence of operating parameters concerning cycle performance in the context of a WHR cycle is discussed. The low side, high side pressures, and the split ratio between the high-temperature and low-temperature turbines are optimized for maximum power rather than thermodynamic cycle efficiency. The cycle performance is evaluated with air as the primary heat transfer fluid in the waste heat recovery heat exchanger operating at a maximum source temperature of 500 °C. The sink temperature is assumed to be 40 °C to enable operation in tropical conditions like India. The paper also compares the performance of the proposed WHR cycle with the baseline single recuperated sCO2 cycle operating under similar conditions. The analysis shows that the proposed cycle is able to extract 60% more heat and produce 37% more power than the single recuperated sCO2 cycle. The maximum heat recovery factor for the analyzed WHR cycle is 17.4%, compared to 12.7% for the single recuperated sCO2 cycle. [ABSTRACT FROM AUTHOR]

Mitochondrial disorders represent a heterogeneous group of genetic disorders with variations in severity and clinical outcomes, mostly characterized by respiratory chain dysfunction and abnormal mitochondrial function. More specifically, mutations in the human SCO2 gene, encoding the mitochondrial inner membrane Sco2 cytochrome c oxidase (COX) assembly protein, have been implicated in the mitochondrial disorder fatal infantile cardioencephalomyopathy with COX deficiency. Since an effective treatment is still missing, a protein replacement therapy (PRT) was explored using protein transduction domain (PTD) technology. Therefore, the human recombinant full-length mitochondrial protein Sco2, fused to TAT peptide (a common PTD), was produced (fusion Sco2 protein) and successfully transduced into fibroblasts derived from a SCO2/COX-deficient patient. This PRT contributed to effective COX assembly and partial recovery of COX activity. In mice, radiolabeled fusion Sco2 protein was biodistributed in the peripheral tissues of mice and successfully delivered into their mitochondria. Complementary to that, an mRNA-based therapeutic approach has been more recently considered as an innovative treatment option. In particular, a patented, novel PTD-mediated IVT-mRNA delivery platform was developed and applied in recent research efforts. PTD-IVT-mRNA of full-length SCO2 was successfully transduced into the fibroblasts derived from a SCO2/COX-deficient patient, translated in host ribosomes into a nascent chain of human Sco2, imported into mitochondria, and processed to the mature protein. Consequently, the recovery of reduced COX activity was achieved, thus suggesting the potential of this mRNA-based technology for clinical translation as a PRT for metabolic/genetic disorders. In this review, such research efforts will be comprehensibly presented and discussed to elaborate their potential in clinical application and therapeutic usefulness.

Supercritical CO 2 central-receivers must withstand high temperatures and pressures combined with cyclic operation, which makes the solar receiver susceptible to creep-fatigue failure. In this work, a creep-fatigue analysis of a sCO 2 Inconel 740H tubular receiver of a 2 MW e solar tower plant has been accomplished to study the influence of the tube size on the receiver and solar field design. A 2D numerical model of the tubular receiver that accounts for the thermal conduction in both radial and circumferential directions was developed to determine the sCO 2 and wall temperature profile, which is crucial for the creep-fatigue calculations. The receiver flux distribution, which is an input to the model, was obtained with SolarPILOT, while a conventional recompression model was used to calculate the cycle efficiency and inlet temperature to the receiver. Comparison of the results of the 2D model with those of a 1D model showed that the 1D model overestimates the creep fatigue rupture time by two orders of magnitude. Furthermore, the efficiency and costs of the heliostat field and receiver were calculated for different receiver tube sizes. Smaller tubes allowed a higher maximum heat flux leading to smaller receiver and heliostat field designs, which resulted in higher overall efficiency of the power plant and lower material costs. For a design ensuring 25 year receiver lifetime the minimum sCO 2 solar receiver cost, 345 €/kW th , was obtained for the smallest pipe diameter. [Display omitted] • A creep-fatigue analysis of a sCO 2 central-receiver is presented. • Circumferential thermal conduction is not negligible due to the thick receiver tubes. • The cost and thermo-mechanical behavior of the power plant for different receiver tubes size are studied. • Smaller tubes result in better performance and lower costs of sCO 2 tower power plants. [ABSTRACT FROM AUTHOR]

Summary: The present study investigates the performance of a multi‐generation plant by integrating a parabolic dish solar collector to a steam turbine and absorption chiller producing electricity and process heat and cooling. Thermodynamic modeling of the proposed solar dish integrated multi‐generation plant is conducted using engineering equation solver to investigate the effect of certain operating parameters on the performance of the integrated system. The performance of the solar integrated plant is evaluated and compared using three different heat transfer fluids, namely, supercritical carbon dioxide, pressurized water, and Therminol‐VPI. The useful heat gain by collector is utilized to drive a Rankine cycle to evaluate the network output, rate of process heat, cooling capacity, overall energetic, and exergetic efficiencies as well as coefficient of performance. The results show that water is an efficient working fluid up to a temperature of 550 K, while Therminol‐VPI performs better at elevated temperatures (630 K and above). Higher integrated efficiencies are linked with the lower inlet temperature and higher mass flow rates. The integrated system using pressurized water as a heat transfer fluid is capable of producing 1278 and 832 kW of power output and process heat, respectively, from input source of almost 6121 kW indicating overall energy and exergy efficiencies of 34.5% and 37.10%, respectively. Furthermore, multi‐generation plant is evaluated to assess the exergy destruction rate and steam boiler is witnessed to have the major contribution of this loss followed by the turbine. The exergo‐environmental analysis is carried out to evaluate the impact of the system on its surroundings. Exergo‐environmental impact index, impact factor, impact coefficient, and impact improvement are evaluated against increase in the inlet temperature of the collector. The single‐effect absorption cycle is observed to have the energetic and exergetic coefficient of performances of 0.86 and 0.422, for sCO2 operating system, respectively, with a cooling load of 228 kW. [ABSTRACT FROM AUTHOR]

• The thermal and mechanical performance of the sCO2 solar cavity receiver were researched. • Large-diameter coiled tubes harm the receiver's thermal efficiency and safety. • Curvature of the coiled tube has the opposite effect on the thermal efficiency and safety of the receiver. • Cloud cover has a large influence on the temperature and stress of the solar receiver. • Solar receiver start-up early, the large flow rate produces low thermal stress. Solar thermal power systems rely on high-temperature cavity receivers. Guaranteeing the effective and secure operation of a receiver involves researching the impacts of various geometric parameters and operating conditions on its thermal performance and mechanical qualities. To examine the impacts of diameter, curvature, and various operating conditions on the thermal and mechanical performance of a receiver, a coupled thermal–mechanical model was created and assessed. The findings showed that the spiral coiled tube's thermal stress distribution is very nonuniform. Thermal efficiency declines and maximum stress rises from 74.9 MPa to 171.87 MPa as the diameter increases from 10 mm to 30 mm. The thermal efficiency rises when the curvature goes from 1/190 to 1/130, but the stress rises as well. The outlet temperature drops by 73.46 K after 5 min of cloud cover; cloud cover and startup conditions will result in rapid variations in stress and temperature on the coiled tube wall, endangering the receiver's safe function and shortening its lifespan. [ABSTRACT FROM AUTHOR]

In recent years, supercritical CO2 power cycles have received a large amount of interest due to their exceptional theoretical conversion efficiency above 50%, which is leading a revolution in power cycle research. Furthermore, this high efficiency can be achieved at a moderate temperature level, thus suiting concentrating solar power (CSP) applications, which are seen as a core business within supercritical technologies. In this context, numerous studies have been published, creating the need for a thorough analysis to identify research areas of interest and the main researchers in the field. In this work, a bibliometric analysis of supercritical CO2 for CSP applications was undertaken considering all indexed publications within the Web of Science between 1990 and 2020. The main researchers and areas of interest were identified through network mapping and text mining techniques, thus providing the reader with an unbiased overview of sCO2 research activities. The results of the review were compared with the most recent research projects and programs on sCO2 for CSP applications. It was found that popular research areas in this topic are related to optimization and thermodynamics analysis, which reflects the significance of power cycle configuration and working conditions. Growing interest in medium temperature applications and the design of sCO2 heat exchangers was also identified through density visualization maps and confirmed by a review of research projects.

The present study explores the integration of supercritical CO 2 (sCO 2) power cycles into Concentrating Solar Power (CSP) plants using molten salt, and the hybridization of these plants with solar photovoltaic (PV) systems through electric heaters. Techno-economic evaluations determined the optimal power cycle configuration and subsystem designs for two different scales and locations and then compared them with state-of-the-art solar power plants. The results show that hybridizing PV with state-of-the-art CSP can lead up to a 22% reduction in the Levelized Cost of Electricity (LCOE) compared to standalone CSP systems. This hybridization and the use of electric heaters are particularly beneficial for small-scale installations and locations with low DNI/GHI ratios. By replacing the steam Rankine cycle with a sCO 2 power block, a further 42% reduction in LCOE can be achieved at small scales, even with a simple recuperated cycle. In conclusion, the hybridization with PV and the integration of sCO 2 power blocks provide cost benefits despite the temperature limitations imposed by the molten salt. Hybrid PV-CSP plants with sCO 2 power blocks prove to be a cost-effective solution for capacity factors exceeding 60%. For lower capacity factors, configurations combining PV with battery energy storage or PV with electric heaters, thermal energy storage, and sCO 2 power blocks are preferable options. • Hybrid PV-CSP plants with sCO 2 cycles can be a cost-effective solution for CF exceeding 60%, both at small and large scale. • Hybridizing PV with CSP reduces LCOE by up to 22% compared to CSP standalone. • Hybridizing PV and CSP with electric heaters is beneficial mainly at small-scale and in locations with low DNI/GHI ratios. • By replacing steam Rankine cycles with sCO 2 ones lowers the LCOE by 42% in small-scale PV-CSP plants with molten salt. • A simple recuperated Brayton cycle is the suggested Brayton cycle to be integrated into CSP plants with molten salt. [ABSTRACT FROM AUTHOR]

Highlights • Turbulent sCO 2 heat transfer cooled in large horizontal tubes is investigated. • Rigorous validations against experiments for four k - ε RANS models are presented. • The effect of heat flux and tube diameter has been analysed from fundamental aspects. • Influences of buoyancy on the flow fields and heat transfer performance are discussed. Abstract This paper presents the results of computational investigations on cooling heat transfer of turbulent sCO 2 in three horizontal tubes with diameter of 15.75 mm , 20.00 mm and 24.36 mm using RANS turbulence models at a pressure of P = 8.0 MPa. Four models with good prediction performance demonstrated in literature (RNG k - ε model and three other low-Reynolds number k - ε models of LS, YS and AKN) have been validated against experimental measurements and to observe that results from the AKN model are closer to experimental data. Details of heat transfer behaviour of sCO 2 cooled in horizontal tubes within this diameter range are revealed and the influence of heat flux, tube diameter and buoyancy on heat transfer performance have been discussed. Results demonstrate that at T b > T pc (pseudocritical temperature), sCO 2 heat transfer performance is enhanced as the heat flux and tube diameter increase; whereas at T b < T pc , the heat flux and tube diameter almost do not affect the heat transfer performance. The buoyancy effect only generates slight enhancement for turbulent heat transfer from sCO 2 flowing in horizontal tubes with large diameters. However, as the values of Richardson number Ri that quantifies the buoyancy effects continue increasing within Ri > 0.1 , the buoyant force is enhanced, which in turn impairs the heat transfer near T pc . This is a result contrary to past reports confined to small diameter tubes, which is mainly attributed to the accumulation of denser cold fluids at the bottom of the pipe when buoyancy effects are strong. [ABSTRACT FROM AUTHOR]