sCO2 Power Research Articles

Optimizing power, cooling, and hydrogen generation: A thermodynamic and exergoeconomic study of an advanced sCO2 trigeneration system

This paper presents an innovative trigeneration system designed for efficient power, cooling, and hydrogen production. It combines a supercritical carbon dioxide (sCO2) power cycle with a Kalina cycle (KC) and an ammonia-water-based absorption refrigeration cycle (ARC), all integrated with a PEM electrolyzer (PEME) unit. The system optimally utilizes waste heat from the sCO2 power cycle to enhance power generation through the KC and provide cooling via the ARC. Additionally, it leverages the PEME system and KC-generated power for eco-friendly hydrogen production. Mathematical models, thermodynamic, and exergoeconomic analyses were performed, including parametric studies, optimization, and comparative analyses. The results indicate that the reactor experiences the highest exergy destruction rate, while components in the bottoming cycles exhibit lower exergy destruction. From an exergoeconomic perspective, the reactor and sCO2 turbine are ranked as the first and second most significant components. Under the optimal conditions, the system achieved a 9.76 % increase in exergy efficiency and a 6.63 % reduction in total product unit cost. The system also provides substantial net power output, cooling capacity, and hydrogen production rates of 261.74 MW, 123.95 MW, and 176.328 kg/h, respectively. These findings highlight the system's significant thermodynamic and economic advantages, making it a promising choice for diverse user needs.

Experimental and Computational Heat Transfer Study of sCO2 Single-Jet Impingement

Abstract This study experimentally and computationally investigates the heat transfer capability of supercritical carbon dioxide (sCO2) single jet impingement. The evaluated jet Reynolds number range is between 80,000 and 600,000, with a nondimensional jet-to-target surface spacing of 2.8. CO2-impinging jet stagnation conditions were maintained at approximately 200 bar and a temperature of ∼400 °C for most experiments. The goal is to understand how changes in the aforementioned parameters influence heat transfer between the working fluid and the heated surface. Additionally, due to the elevated Reynolds numbers and difference in thermodynamic properties between air and CO2, air-derived impingement correlations may not be appropriate for CO2 impingement; these correlations will be evaluated against experimental sCO2 impingement data. At the time of this study, no sCO2 impingement data was available relevant to sCO2 power cycles. The target surface is a 1.5-in. diameter copper block centered on the 3 mm jet orifice. A mica heating element bolted to the bottom of the copper block provides a uniform heat flux. Thermocouples embedded in the copper block are used to determine the surface temperature. Nusselt numbers obtained from experimental sCO2 test data are compared to area-averaged Nusselt numbers from air-derived correlations. The comparisons showed that air correlations drastically underpredict the heat transfer when sCO2 is used as the working fluid. A modified sCO2 correlation using experimental data at discussed conditions is derived based on an existing air correlation. A CFD study is also performed to further investigate sCO2 heat transfer characteristics, and assess the numerical model applicability to this problem type.

Multi-objective performance optimization & thermodynamic analysis of solar powered supercritical CO2 power cycles using machine learning methods & genetic algorithm

The present study is focused on multi-objective performance optimization & thermodynamic analysis from the perspectives of energy and exergy for Recompression, Partial Cooling & Main Compression Intercooling supercritical CO2 (sCO2) Brayton cycles for concentrated solar power (CSP) applications using machine learning algorithms. The novelty of this work lies in the integration of artificial neural networks (ANN) and genetic algorithms (GA) for optimizing the performance of advanced sCO2 power cycles considering climatic variation, which has significant implications for both the scientific community and engineering applications in the renewable energy sector. The methodology employed includes thermodynamic analysis based on energy, exergy & environmental factors including system performance optimization. The system is modelled for net power production of 15 MW thermal output utilizing equations for the energy and exergy balance for each component. Subsequently, thermodynamic model extracted dataset used for prediction & evaluation of Random Forest, XGBoost, KNN, AdaBoost, ANN and LightGBM algorithm. Finally, considering climate conditions, multi-objective optimization is carried out for the CSP integrated sCO2 Power cycle for optimal power output, exergy destruction, thermal and exergetic efficiency. Genetic algorithm and TOPSIS (technique for order of preference by similarity to ideal solution), multi-objective decision-making tool, were used to determine the optimum operating conditions. The major findings of this work reveal significant improvements in the performance of the advanced sCO2 cycle by 1.68 % and 7.87 % compared to conventional recompression and partial cooling cycle, respectively. This research could advance renewable energy technologies, particularly concentrated solar power, by improving power cycle designs to increase system efficiency and economic feasibility. Optimized advanced supercritical CO2 power cycles in concentrated solar power plants might increase renewable energy use and energy generation infrastructure, potentially opening new research avenues.

Manufacturing and Hydro Testing of a 10 MWe sCO2 Axial Turbine

Abstract Supercritical CO2 (sCO2) power cycles designed for thermodynamic efficiencies above 50% push component designs into pressure and temperature combinations that approach the limits of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code and ASME Piping Design Codes with Turbine inlet conditions near 250 bar and 715 °C. These design conditions which limit available materials to high nickel alloys are compounded by the high fluid densities of sCO2 at these conditions which result in very compact machinery at the 10 MWe class which are currently being developed for the DOE supercritical transformational electric power (STEP) program. Design of the STEP Turbine is complete with integrated lessons learned from a previous 1 MWth subscale demonstration of a high temperature 10 MWe Turbine designed under the DOE SunShot Program. Fabrication of the STEP Turbine is nearing completion with all housings and pressure containing components in hand. This paper provides a detailed look at design intentions and limitations for the pressurized sections of the main pressure casing and the fabrication of key turbine components. Additional discussion is provided regarding postfabrication inspection and acceptance of the casing for use after issues with casing welds were identified late in the fabrication process.

SCO2 power cycle/reverse osmosis distillation system for water-electricity cogeneration in nuclear powered ships and submarines

As global concerns about climate change and environmental impacts continue to grow, there is a strong demand for cleaner, greener, and more efficient propulsion solutions in the maritime industry. By leveraging nuclear energy, which offers low carbon emissions and high efficiency, naval vessels can significantly reduce their environmental footprints and contribute to global efforts to combat climate change. Additionally, the ability to produce electricity and freshwater simultaneously addresses the critical need for self-sufficiency during long missions, particularly in remote or resource-constrained areas where access to freshwater may be limited. This study explores a novel approach to address water and energy supply challenges in naval applications through a nuclear-driven supercritical carbon dioxide (sCO2) power cycle–Reverse Osmosis (RO) cogeneration system. The aim is to assess the feasibility and benefits of this system for meeting water and electricity demands in maritime operations and enhancing the sustainability, efficiency, and self-sufficiency of naval vessels with nuclear energy and advanced technologies. A parametric study has been performed to understand the effects of important parameters such as the maximum and minimum cycle temperature and pressure, seawater inlet conditions, pressure vessel design, and membrane properties on the system performance. Moreover, an optimization study has been performed to determine the best possible combination of these parameters to achieve the highest system efficiency. For the determined optimal set of parameter values, it is possible to have an sCO2 power cycle with a cycle efficiency of 40.5 %, an electrical power output of 121.6 MW and an RO system with an efficiency of 29.4 %, a recovery ratio of 29.3 %, a specific fuel consumption (SEC) of 2.29 kW·h/m3, and a freshwater production rate of 1531.6 m3/d by utilizing 145.9 kW electrical power. The positive outcomes of this study indicate that the system has the potential to be a viable and effective solution for addressing water and energy supply challenges in naval operations.

Process splitting analysis and thermodynamic optimization of the Allam cycle with turbine cooling and recompression modification

Allam cycle is an advanced semi-closed supercritical carbon dioxide (sCO2) power cycle that utilizes hydrocarbon fuels with nearly zero carbon emission. Different from other closed power cycles, in the Allam cycle, the oxy-fuel combustion products are directly mixed with the working fluid and the turbine blade cooling is necessary for the high cycle temperature above 1000 °C; moreover, the heat integration might be applied to the Allam cycle to improve the thermodynamic performance, making the Allam cycle complex and hard to conduct the process and parameter optimization. To deepen the understanding on the performance of the Allam cycle with turbine cooling and recompression modification, a novel splitting analytical method is developed that the Allam cycle is split into the closed cycle and open process, and the closed cycle is further split into the simple host cycle and two equivalent power cycles. Using the constructed splitting analytical models, the influences of the turbine cooling and the recompression modification on the net efficiency are clearly evaluated by the split cycles, and the highest efficiency of the Allam cycle is optimized to be 49.92 % (higher heating value) as the coolant temperature and recompression mass flow rate are 320 °C and 439.5 kg/s, respectively.

Investigation on the effect of the cooler design on the performance of onboard supercritical carbon dioxide power cycle for hypersonic vehicles

The scramjet cooling and power generation are the key demands for the hypersonic vehicle. To satisfy the cooling and electricity generation requirements of hypersonic vehicles, the onboard supercritical carbon dioxide (sCO2) power cycle is adopted in this paper. Moreover, the cooler design has a significant effect on the feasibility and overall performance of onboard sCO2 power cycle, but there is no research considering the effect of the cooler design. Accordingly, the effects of the cooler design on the overall performance of onboard sCO2 power cycles applied in hypersonic vehicles are comprehensively investigated based on the thermodynamic models. The results indicated that the optimum cooler designs are suggested to adopt a small channel diameter and a relatively large channel number for minimizing the cooler mass and fuel consumption for cooling sCO2 and maximizing the system thermal efficiency. Moreover, the cold channel diameter is designed to be smaller than the hot channel diameter. The cold channel number is required to be larger than the hot channel number. The total flow area of cold channel is smaller than that of hot channel. The geometric parameters of cooler hot channel could be designed based on the Re ranging from 15,000 to 34,000.

System Design, Optimization and 2nd Law Analysis of a 100 MWe Double Reheat s-CO2 Power Plant at Full Load and Part Loads

Super-critical Carbon dioxide (s-CO2) power plants are considered to be efficient and environmentally friendly compared to the traditional Rankine cycle-based steam power plants and Brayton cycle-based gas turbine power plants. In this work, the system design of a coal-fired 100 MWe double reheat s-CO2 power plant is presented. The system is also optimized for efficiency with turbine inlet pressures and the recompression ratio as the variables. The components needed, mass flow rates of various streams and their pressures at various locations in the system have been established. The plant has been studied based on 1st and 2nd laws at full load and at part loads of 80%, 60% and 40%. Operating parameters such as mass flow rate, pressure and temperature have considerably changed in comparison to full load operation. It was also observed that the 1st law efficiency is 53.96%, 53.93%, 52.63% and 50% while the 2nd law efficiency is 51.88%, 51.86%, 50.61% and 48.1% at 100%, 80%, 60% and 40% loads, respectively. The power plant demonstrated good performance even at part loads, especially at 80% load, while the performance deteriorated at lower loads. At full load, the highest amount of exergy destruction is found in the main heater (36.6%) and re-heaters (23.2% and 19.6%) followed by the high-temperature recuperator (5.7%) and cooler (4.1%). Similar trends were observed for the part load operation. It has been found that the recompression ratio should be kept high (>0.5) at lower loads in order to match the performance at higher loads. Combustion and heat exchange due to finite temperature differences are the main causes of exergy destruction, followed by pressure drop.

Energy and exergy analyses of a recompression supercritical CO2 cycle combined with a double-effect parallel absorption refrigeration cycle

In this study, a new cogeneration system is presented that can make optimal use of the waste heat from the sCO2 power cycle using a double-effect parallel absorption refrigeration cycle (DEARC), generating electricity and refrigeration simultaneously. A comparative study between the proposed (sCO2/DEARC) system and the stand-alone sCO2 power system is conducted to show its advantages and potential. The performances of the sCO2 and sCO2/DEARC systems are evaluated from the energetic and exergetic points of view using an in-house developed thermodynamic simulation platform via Engineering Equation Solver (EES) software. Variables such as pressure ratio, turbine inlet temperature, and evaporator temperature are also used for parametric analysis. The results indicate that the proposed system can generate of 132.72 MW cooling capacity. Also, the results show that the proposed sCO2/DEARC system can achieve a 55.8% and 5.2% improvement in thermal efficiency and exergy efficiency, respectively, with a negligible decrease in net power output (Wnet) compared to the stand-alone sCO2 power plant.

Physics-Informed Deep Learning-Based Proof-of-Concept Study of a Novel Elastohydrodynamic Seal for Supercritical CO2 Turbomachinery

Abstract Supercritical carbon dioxide (sCO2) power cycles show promising potential of higher plant efficiencies and power densities for a wide range of power generation applications such as fossil fuel power plants, nuclear power production, solar power, and geothermal power generation. sCO2 leakage through the turbomachinery has been one of the main concerns in such applications. To offer a potential solution, we propose an elastohydrodynamic (EHD) seal that can work at elevated pressures and temperatures with low leakage and minimal wear. The EHD seal has a very simple, sleeve-like structure, wrapping on the rotor with minimal initial clearance at micron levels. In this work, a proof-of-concept study for the proposed EHD seal was presented by using the simplified Reynolds equation and Lame’s formula for the fluid flow in the clearance and for seal deformation, respectively. The set of nonlinear equations was solved by using both the conventional Prediction–Correction (PC) method and modern Physics-Informed Neural Network (PINN). It was shown that the physics-informed deep learning method provided good computational efficiency in resolving the steep pressure gradient in the clearance with good accuracy. The results showed that the leakage rates increased quadratically with working pressures and reached a steady-state at high-pressure values of 15∼20 MPa, where Q = 300 g/s at 20 MPa for an initial seal clearance of 255 μm. This indicates that the EHD seal could be tailored to become a potential solution to minimize the sCO2 discharge in power plants.

Helical Fins for Concentrated Solar Receivers: Design Optimization and Entropy Analysis

Abstract Concentrated solar power (CSP) with thermal energy storage (TES) has the potential to achieve grid parity. This can be realized by operating CSP systems at temperatures above 700 °C with high-efficiency sCO2 power cycles. However, operating CSP systems at such temperatures poses several challenges, among which the design of solar receivers to accommodate increased thermal loads is critical. To this end, this work explores and optimizes various swirl-inducing internal fin designs for solar receiver tubes. These fin designs not only improve the thermal performance of receiver tubes but also levelize temperature unevenness caused by non-uniform thermal loading. In this work, the geometric parameters of the fin designs are optimized to maximize the Nusselt number with a constraint on the friction factor. This optimization, however, is computationally intensive, requiring hundreds of simulation calls to computational fluid dynamics (CFD) models. To circumvent this problem, surrogate models are used to approximate the simulation outputs needed during the optimization. In addition, this study also examines the fin designs from an entropy generation perspective. To this end, the entropy contributions from thermal and viscous effects are quantitatively compared while varying the operational Reynolds number.

Rational design process for gas turbine exhaust to supercritical CO2 waste heat recovery heat exchanger using topology optimization

Advances in additive manufacturing (AM) technologies and topology optimization methodologies are enabling sophisticated novel designs for heat exchanger performance. These tools have been demonstrated for development of high-performance heat sinks considering local or component-level performance factors (e.g., heat transfer per volume). To leverage such capabilities in larger-scale energy systems, structured design methodologies are needed that consider system-level factors, such as production cost, cycle-level efficiency, and operational constraints. This study seeks to develop and assess a rational approach for designing thermo-economically optimal heat exchangers for such applications. The methodology is illustrated through development of the Primary Heat Exchanger (PHX) for a supercritical carbon dioxide (sCO2) power cycle recovering exhaust heat from a 6 MW-scale natural gas turbine. The proposed approach begins with a detailed thermodynamic cycle model, which is then extended to account for techno-economics. Next, an optimal PHX heat transfer capacity target is identified, and a high-level geometry is selected based on operating characteristics. This geometry is then divided into repeating 2D prismatic unit cells, for which topology optimization is applied to identify high-performance heat transfer geometries. A key aspect of this process is that the unit cell geometries are optimized using the total PHX mass as the objective function, which represents a surrogate for production cost. This leads to distinct designs compared with approaches that optimize local heat transfer and flow resistance factors. A second topology-optimized design is developed using a representative local thermal-fluid performance objective function and is found to require 1.6× the mass of the design generated with the system-level techno-economic objective for the same unit cell size. Conventional-type PHX designs with simple longitudinally finned tubes are developed for comparison, and are found to require total masses 1.5× or greater than the design obtained with the proposed process. Integrating this approach with detailed additive manufacturing costing models and experimentally validated fabrication constraints can yield a streamlined workflow for HX design for future energy systems.

Improvement design and performance assessment of two supercritical carbon dioxide power cycles for waste heat recovery

Waste heat recovery (WHR) from thermal engines and industrial processes is significantly beneficial to cutting fossil fuel consumptions and carbon dioxide emissions. Recompression supercritical carbon dioxide (sCO2) power cycles have many advantages of high efficiency, compact design and environmentally friendly property, and they are regarded as the competitive and promising energy conversion technology for WHR. However, a large space is still left for recompression sCO2 power cycle to improve its capability with regard to waste heat extraction and power output. The novelty of this work is the development of two novel sCO2 power cycles based on the recompression sCO2 cycle aimed at thoroughly and efficiently reusing the waste heat. Thermodynamic and exergoeconomic models are established to perform the quantitative parametric analyses, multi-objective optimizations, exergy and exergoeconomic analyses on the proposed systems. The results indicate that the second proposed system is preferred, since it can significantly improve the net power output by 43.81% and 12.32% while reducing the total product unit cost by 7.24% and 10.39%, compared with the traditional recompression sCO2 cycle and the improved sCO2 cycle, respectively. Although the first proposed system has a better performance in waste heat extraction and net power output, it requires a higher cost.

An analytical method for quickly evaluating the performances of refractory alloys in sCO2 Brayton cycle applications

An analytical method has been developed to quickly evaluate structure materials' performances in sCO2 power cycle applications. This analytical method combines a conjugate heat transfer model for a tube with constant heat flux boundary conditions with its corresponding mechanical model to obtain the allowable working fluid temperatures and minimum required wall thickness. Three refractory alloys, Inconel 617, Haynes 230, and SS 253 MA, have been selected for implementing this analytical method by comparing their allowable working fluid temperatures and minimum required wall thicknesses under various boundary conditions. The allowable working fluid temperature has been observed not to change with the external surface temperature of the tube monotonically but with a peak. In general, Nickel based alloys (Inconel 617 and Haynes 230) have better performances than the SS 253 MA, but the difference becomes insignificant for low working fluid temperature and low heat flux applications. Besides, Inconel 617 can offer slightly higher allowable working fluid temperature than Haynes 230 in most work conditions, but the minimum required wall thickness is also significantly larger than that of Haynes 230. In addition, the minimum required wall thickness can be significantly reduced when the allowable working fluid temperature is set slightly lower than its peak value due to the rapid decrease of the maximum allowable stresses at high temperatures, which will be useful in potential techno-economic optimization for heat exchanger designs.

Structural Stress Intensity Analysis of Hybrid Heat Exchangers Based on Thermal Hydraulic Performance in S-CO2 Power Cycle

Abstract Hybrid heat exchangers (H2Xs) can be used for heat exchange equipment between high-temperature exhaust gas from ships and high-pressure supercritical carbon dioxide (S-CO2) from the S-CO2 power cycle. We investigate structural stress intensity characteristics of the H2Xs based on thermal-hydraulic performance. Air and S-CO2 are employed as the working fluids and the Stainless Steel 316 (SS316) as the solid substrate. The thermal-hydraulic performance and structural stress intensity characteristics of the H2Xs are conducted by Ansys Fluent and Mechanical, respectively. The results show the mechanical stress induced by pressure loading and the thermal stress induced by temperature gradient are found to be equally important sources of stress intensity. At the inlet and outlet of the H2Xs, the total stress intensity along all paths is not smooth and continuous, and there will be a significant change due to the change in the temperature gradient. The mechanical stress caused by the fluid pressure loss is almost negligible. The change in inlet mass flowrate and temperature mainly affects the stress intensity distribution of the left and right walls on the fin channel. The pressure variation of the diesel engine has little effect on the total stress intensity. Importantly, the total stress intensity of the H2X is mainly affected by the change in S-CO2 fluid pressure.

Untapping Industrial Flexibility via Waste Heat-Driven Pumped Thermal Energy Storage Systems

Pumped thermal energy storage (PTES) is a promising long-duration energy storage technology. Nevertheless, PTES shows intermediate round-trip efficiency (RTE—0.5 ÷ 0.7) and significant CAPEX. sCO2 heat pumps and power cycles could reduce PTES CAPEX, particularly via reversible and flexible machines. Furthermore, the possibility to exploit freely available heat sources (such as waste heat and/or CSP inputs) could increase RTE, making the system capable of an apparent RTE > 100% as well as reducing CAPEX, avoiding the need for two TES systems. This paper analyses the potential valorization of industrial waste heat (WH) to enhance PTES thermodynamic performance as well as increase industrial energy efficiency, valorizing different levels of WH sources in the 100–400 °C temperature range. In fact, the use of additional heat, otherwise dumped into ambient surroundings, may contribute to avoiding the need for a second TES, thus enhancing plant competitiveness. Starting from an assessment of the most relevant industrial sectors to apply the proposed solution (looking at available WH and electric flexibility needed), this paper analyses the feasibility of a specific sCO2-based PTES case study, where the cycle is integrated into a cement production plant with a WH temperature of around 350 °C. It is demonstrated that the CAPEX of the proposed systems are still relevant and only a robust exploitation of the PTES in the ancillary service market could attract industrial customers’ interest in sCO2 PTES.

Small-scale concentrated solar power system with thermal energy storage: System-level modelling and techno-economic optimisation

A dynamic, techno-economic model of a small-scale, 31.5 kWe concentrated solar power (CSP) plant with a dish collector, two-tank molten salt storage, and a sCO2 power block is analysed in this study. Plant solar multiple and storage hours are optimised using a multi-objective genetic algorithm to minimise the levelised cost of electricity (LCOE) and maximise the capacity factor (CF). The optimal LCOE is found to be ranging from 122.7 USD/MWhe to 217.8 USD/MWhe when using optimistic and pessimistic power block cost assumptions. In contrast, the literature reports an LCOE of 193.9 USD/MWhe for a similar 31.5 kWe CSP system without storage. The addition of thermal energy storage in the system configuration dramatically improves the CF from 30.4%—reported in the literature—to 87.2% obtained from the present model. The sensitivity analysis suggests that upscaling the system to 400 kWe reduces the LCOE to 121.9–172.2 USD/MWhe as a result of lower unit power block costs at larger scales. The comparison of CSP and PV-battery systems in three distinct locations—characterised by varying direct and global solar resources—indicates that the CSP system is promising in locations with abundant direct normal irradiance (DNI). For locations with medium DNI resource, the LCOE of PV-battery system is within the margin of uncertainty of CSP system. In low-DNI locations, PV-battery systems proved to be preferable.

Performance comparison of three supercritical CO2 solar thermal power systems with compressed fluid and molten salt energy storage

In recent years, the supercritical carbon dioxide (sCO2) Brayton cycle power generation system has gradually attracted the attention of academics as a solar thermal power generation technology. To achieve the stable and effective use of solar energy, three sCO2 solar power generation systems were studied in this paper. These systems included a molten salt thermal storage system, a compressed CO2 energy storage system, and a combined molten salt thermal storage and compressed CO2 energy storage system. The thermodynamic analysis model of the sCO2 power generation system is constructed, and a mathematical model of the solar power tower system is produced. The operating conditions, thermal efficiency, exergy efficiency, and economics of these three systems on typical days are investigated and compared. The results indicate that the power generation system coupled with compressed CO2 storage has higher thermal and exergy efficiencies than the other two systems with the same daily heliostat field. The thermal efficiencies can be as high as 6.56% and 5.91% respectively, and the exergy efficiencies as high as 5.76% and 6.22% respectively. The system coupled with compressed CO2 energy storage is more cost-effective and has a shorter payback period than the system coupled with molten salt thermal storage system and the system with both forms of energy storage.

Thermodynamic features of the regenerative system of direct fired sCO2 power cycles with oxygen combustion of methane

The article presents an analysis of the thermodynamic features of the operation of a regenerative system of sCO2 power cycles. The cycle with a two-stage pressure increase configuration is taken as a basis for calculation. The supply of energy to the working fluid is provided by the operation of the regenerative system and by oxy-fuel combustion. Methane is used as fuel. The issues of theoretically achievable heating temperatures of the working fluid in the cycle regenerative system are considered. The influence of thermodynamic parameters on the heat fluxes of the regenerative system is estimated. For the first time, an assessment was made of the relative and absolute contribution of water vapor, formed during fuel combustion, to heat flows. This study makes it possible to establish the physical quantities pressure, temperature and heat fluxes, which are necessary for further design calculations of heat exchangers to be used in industrial installations. As a result of multi-variant calculations of the cycle (when varying the temperature at the turbine inlet in the range of 500–1500 °C and pressure - from 100 to 400 bar), it was found that the temperature of the working fluid supply to the combustion chamber can be taken at the level of 2/3 of the temperature at its outlet. At operating temperatures of the working fluid at the level of 1000–1200 °C, the contribution of water vapor to regenerative heating will be 3–17%, depending on their mass content. The total theoretical heat flow to the cycle regenerative system will be 800–1000 kJ/kg CO2. The energy supply to the working fluid due to fuel combustion does not exceed 50% of the total energy supplied in the operating temperature and pressure ranges.

Techno-economic optimization of molten salt based CSP plants through integration of supercritical CO2 cycles and hybridization with PV and electric heaters

The present study explores the integration of supercritical CO2 (sCO2) 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 sCO2 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 sCO2 power blocks provide cost benefits despite the temperature limitations imposed by the molten salt. Hybrid PV-CSP plants with sCO2 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 sCO2 power blocks are preferable options.