Supercritical Carbon Dioxide Power Research Articles

Oxygen Storage Incorporated Into Net Power and the Allam–Fetvedt Oxy-Fuel sCO2 Power Cycle—Techno-Economic Analysis

Abstract 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.

A comprehensive multi-variable approach for evaluating the feasibility of integration a novel heat recovery model into a gas turbine power plant, producing electricity, heat, and methanol

Considering the importance of efficient thermal integration for a gas turbine cycle using its energetic flue gas, the current paper proposes an eco-friendly and efficient process integrated into a gas turbine cycle. The newly designed polygeneration structure produces power, hot water, and methanol. The components of this system include a heat provider unit, a direct carbon dioxide hydrogenation unit for the production of methanol, an ammonia Rankine cycle, a proton exchange membrane electrolyzer, a supercritical carbon dioxide power cycle, and two organic Rankine cycles. The feasibility of the proposed model is evaluated using a comprehensive multi-variable assessment from energy, exergy, economic, and environmental approaches. This system exhibits a power production capacity of 17197.23 kW and a methanol generation rate of 0.7573 kg/s. Also, the total irreversibility is equal to 68161.18 kW. Besides, the total energy and exergy efficiencies are found as 68.73% and 32.03%, respectively. This model's carbon dioxide emission is 18667.36 kgCO2/h, and its carbon footprint equals 0.2196 kgCO2/kWh. Furthermore, the economic analysis reveals that the project has an annual total cost of 194,602,338 and a net present value of 686,221,616. Besides, the computed total unit costs for products and energy are 0.3385 $/kWh and 89.81 $/GJ, respectively.

Dynamic Modeling and Control of Supercritical Carbon Dioxide Power Cycle for Gas Turbine Waste Heat Recovery

The gas turbine is a crucial piece of equipment in the energy and power industry. The exhaust gas has a sufficiently high temperature to be recovered for energy cascade use. The supercritical carbon dioxide (S-CO2) Brayton cycle is an advanced power system that offers benefits in terms of efficiency, volume, and flexibility. It may be utilized for waste heat recovery (WHR) in gas turbines. This study involved the design of a 5 MW S-CO2 recompression cycle specifically for the purpose of operational control. The dynamic models for the printed circuit heat exchangers, compressors, and turbines were developed. The stability and dynamic behavior of the components were validated. The suggested control strategies entail utilizing the cooling water controller to maintain the compressor inlet temperature above the critical temperature of CO2 (304.13 K). Additionally, the circulating mass flow rate is regulated to modify the output power, while the exhaust gas flow rate is controlled to ensure that the turbine inlet temperature remains within safe limits. The simulations compare the performance of PI controllers tuned using the SIMC rule and ADRC controllers tuned using the bandwidth method. The findings demonstrated that both controllers are capable of adjusting operating conditions and effectively suppressing fluctuations in the exhaust gas. The ADRC controllers exhibit a superior control performance, resulting in a 55% reduction in settling time under the load-tracking scenario.

Assessment of a sustainable multigeneration system integrating supercritical CO2 Brayton cycle and LNG regasification: Thermodynamic and exergoeconomic evaluation

This study proposes a cost-effective multigeneration system that integrates a supercritical carbon dioxide (sCO2) power cycle with a liquefied natural gas (LNG) regasification process. The system aims to deliver electricity, cooling, heating, and hydrogen simultaneously. Utilizing the temperature difference between the sCO2 cycle and the LNG thermal sink, an ammonia-water-based absorption refrigeration cycle (ARC) recovers waste heat from the sCO2 power cycle, producing cooling. The elevated ammonia concentration at the ARC's condenser outlet is leveraged by a heat pump system for heating production. Concurrently, cold energy from LNG is used to recover latent heat from the condenser and heat rejected from the sCO2 power cycle, providing inputs for additional electrical power through an NG turbine. The system incorporates a PEM electrolyzer (PEME) for hydrogen production. A comprehensive examination, including energy, exergy, and exergoeconomic analyses, evaluates system performance. A sensitivity analysis illustrates the impacts of key parameters. In the baseline scenario, the system achieves energy and exergy efficiencies of 62.79% and 54.89%, with a low product unit cost of 11.35 ($/GJ). The system demonstrates substantial net power output (259.184 MW), cooling capacity (88.938 MW), heating capacity (2.839 MW), and hydrogen production (391.68 kg/h). This robust performance, coupled with cost-effectiveness, positions the proposed system as a versatile and impactful solution for sustainable and environmentally friendly energy applications.

Research on recompression supercritical CO2 power cycle system considering performance and stability of main compressor

The supercritical carbon dioxide (sCO2) power cycle has good prospects for use in many energy applications. Ensuring the stable operation of the power cycle is an important issue. The inlet condition of the main compressor in the sCO2 recompression cycle is close to the critical point of CO2 and the physical properties of CO2 change drastically near the critical point, so the study of inlet parameter change behavior of the main compressor is of great significance to the stable operation of the equipment and the system. This paper investigates the performance of an sCO2 recompression power cycle system under off-design conditions with different cooling and heating conditions. Unlike previous studies, this paper uses more accurate compressor and heat exchanger models to simulate the system for off-designed performance. A 1-D optimization prediction model of the compressor and a density-based segmented heat exchanger model are introduced to predict the performance changes of the system. The operating conditions, performance, and stability of the compressor under different cooling and heating conditions were compared. The results show that variations in different cooling and heating conditions change the inlet temperature of the compressor, causing the sCO2 compressor to deviate from optimal operation. As the inlet temperature increases, the power consumption of the compressor increases. At an inlet temperature of 305 K, the power is 1.93 MW (main compressor, MC) and 2.17 MW (recompressor, RC). When the inlet temperature increases to 310 K, the power increases by more than 10 %. The largest change in system efficiency is 3.76 % for a change in cooling conditions, and the largest change in compressor speed is 14.23 % (MC) and 7.79 % (RC) for a change in heating conditions, respectively. The operating condition of the main compressor moves far away from the surge line when its inlet temperature increases, which means the operation of the main compressor is more stable in this situation. The results of this paper contribute to the stable operation of the sCO2 recompression cycle.

H2-sCO2 direct-fired power system coupled with electrolysis and storage

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 %.

Design and techno economic optimization of an additively manufactured compact heat exchanger for high temperature and high pressure applications

Additive manufacturing (AM) has tremendous potential to produce high-power-density heat exchangers. However, manufacturing AM-heat exchangers at a competitive cost impedes their commercial adoption. In this paper, a novel design of an AM counter flow pin–fin compact recuperator, and its manufacturing costs when using laser powder bed fusion method, are presented. The compact recuperator, which can operate at a high temperature of 800 °C, a high fluid pressure (250 bar) on the cold side and withstand a differential pressure of 170 bars across the fluid streams, as seen in supercritical carbon dioxide power cycles, is designed for a lifetime of 40,000 h. Numerical models to predict the thermo-fluidic performance, and a simplified mechanical model based on plate theory to predict the mechanical stresses, of the recuperator are presented. The recuperator's thermal performance and compactness are studied, and its manufacturability is evaluated via a multi-objective techno-economic optimization. The optimization process considers thermo-fluidic, structural, and manufacturing constraints. The recuperator was fabricated using Haynes 282, and the printability of the design features using a laser-powder-bed-fusion machine is demonstrated. The choice of employing two different AM machines, with different build plate dimensions, number of lasers, and design constraints, on the recuperator's cost/unit, cost/UA, and cost/kW-th o are examined. It is observed that the cost/UA and cost/kW-th decrease exponentially from 13,839 USD-K/kW to 1,994 USD-K/kW and from 80 USD/kW-th to 18 USD/kW-th, respectively, with the size and thermal rating of the recuperator. The exponential decrease in cost/UA and cost/kW-th with increase in power rating opens the possibility of manufacturing large-scale additively manufactured recuperators at a competitive cost. The recuperator, including headers, can achieve a maximum volumetric heat density of 200 MW/m3. The optimization framework can be used to obtain optimal pin-array heat exchanger dimensions for other applications and materials using laser powder bed fusion method.

A review of research on turbines for supercritical carbon dioxide power systems

Supercritical carbon dioxide (S-CO2) Brayton cycle has been known as a potential power cycle technology because of its high efficiency, compact structure and suitability for different heat sources. As one of the key components in the cycle, the turbine has an important impact on the cycle efficiency. Compared with traditional steam and gas turbines, S-CO2 turbines have high working pressure and small size. The internal flow characteristics are significantly different. In this paper, the research progress of S-CO2 turbines in recent years is reviewed. The design and performance evaluation methods for S-CO2 turbines of different types and power levels are summarized, and research on loss correlations and optimization algorithms are introduced. The features of flow field in S-CO2 turbines are discussed. Current studies mainly evaluate the flow field and flow losses through Computational Fluid Dynamics (CFD), and some studies further analyze the influencing mechanism of turbine geometric parameters on flow characteristics. The applications of multi-physical field analysis on S-CO2 turbines are also reviewed. The construction and operation of S-CO2 test loops, and relevant turbine experimental study findings are introduced. Future research directions of S-CO2 turbines are proposed.

Numerical investigation on flow and heat transfer characteristics of a PCHE with liquid lead–bismuth eutectic and sCO2 as working fluids

The Printed Circuit Heat Exchanger (PCHE) plays a critical role in the supercritical carbon dioxide (sCO2) power generation systems, directly impacting the efficiency of the Brayton cycle. In this study,A comparative analysis was conducted to assess the flow and heat transfer characteristics of liquid lead–bismuth eutectic and sCO2 in the combined channel PCHE, as well as in the straight channel and zigzag channel PCHEs. The results indicate that the combined channel configuration of the PCHE offers improvements in heat transfer performance without significantly increasing the resistance of liquid LBE. Additionally, this study analyzes the influence of fluid velocity, pressure, temperature, buoyancy forces and thermal acceleration on the heat transfer characteristics of the combined channel.Finally, the numerical calculation results are evaluated using typical heat transfer correlation equations from the literature to assess their applicability.

Proposal design and thermodynamic analysis of a coal-fired sCO2 power system integrated with thermal energy storage

It is essential to develop supercritical carbon dioxide (sCO2) power systems integrated with thermal energy storage (TES) to achieve efficient and flexible operation of thermal power plants. This study proposes a novel integrated configuration of the sCO2 coal-fired power system and TES. The extracted sCO2 from the high-pressure turbine inlet is utilized as the source of the stored heat, and the extracted heat is used for storage, work, and recovery in steps to decrease the feasible lowest power load ratio. While in the discharging process, the stored energy is used to heat the branched sCO2 to increase the output power. Thermodynamic models for both design and off-design conditions are developed, and the multi-parameter optimization is carried out by genetic algorithm aiming at the highest energy efficiency. The energy conversion characteristics of the heat storage/release process are obtained, and the impacts of variations in the sCO2 extraction ratio and the initial temperature of the molten salt on the performance are analyzed. The results indicate that the adjustable power load range of the integrated system widens with an increase in the sCO2 extraction ratio. When the extraction ratio reaches its maximum value of 0.2749, the minimum power load of the charging process can reduce from 30 % of the rated load to 10.47 %, and the load of the discharging process can increase from 75 % of the rated load to 88.20 %, thus enhancing the operational flexibility. At this point, the round-trip efficiency of the TES system is 67.56 %, which is mainly limited by the performance of the charging process, especially the throttling loss of the turbine. Furthermore, as the temperature of the molten salt cold tank increases, the heat storage capacity decreases, while the minimum power load of the unit increases, thereby reducing the system's flexibility.

Numerical research on performance of new structure centrifugal compressor for supercritical CO2 power systems

The supercritical carbon dioxide (sCO2) power cycle system is a potential thermoelectric conversion system with the advantages of high efficiency and compactness, which can be used in the fields of solar thermal power, nuclear power, and other thermal power systems. The compressor is one of the important machines in sCO2 power systems. To improve the performance and reduce the condensation risk of sCO2 centrifugal compressors, a new structure sCO2 centrifugal compressor is proposed in this paper, which has a partial-cover impeller and self-circulation-channel casing (PISC). The internal flow of the compressor with the new structure is analyzed by the CFD method. The flow and condensation in sCO2 centrifugal compressors with the PISC structure and that with the semi-open impeller and traditional casing (SITC) are compared. The results show that the PISC sCO2 compressor has an inhibiting effect on the condensation at the compressor inlet location, reducing the condensation volume to approximately 82% of that of the original structure under design conditions. The total pressure ratio and isentropic efficiency of compressors are simulated, and the result shows that the minimum stable mass flow rate is reduced by about 13% by introducing the new PISC structure into the sCO2 centrifugal compressor, and the maximum isentropic efficiency is increased from 83.5% to 84.4% compared to that of the SITC compressor. A new design idea for the impeller and sCO2 compressor structure is provided in this paper. The research results can be applied to sCO2 compressors and improve the performance and stability of sCO2 power cycle systems.

Performance Analysis of High-Efficiency Supercritical CO2 Power Cycles Using Recompression

Abstract System simulation, parametric analysis, and exergy analysis were performed to identify the advantages and drawbacks of recompression in the direct-fired supercritical carbon dioxide (sCO2) power cycle. In a parametric investigation, the recompression ratio, turbine inlet temperature (TIT), and pressure ratio were changed, and the obtained values for the efficiency of the power cycle were compared. The TIT was varied between 600 °C and 1600 °C, revealing that recompression is highly effective for lower TIT values but is less effected at higher TIT values. For TITs above 1400 °C, the recompression cycle obtains almost no increase in efficiency. Different optimal recompression ratios were obtained for the different pressure ratios between the high- and low-pressure sides. Exergy analysis reveals that exergy destruction occurs primarily in the oxy-fuel combustor due to a chemical reaction and mixing of the high recirculation fluid. Higher TIT decreases the exergy destruction of the oxy-fuel combustor, but increases the exergy destruction in the lower temperature recuperator, and is not always favorable for obtaining efficiency improvements.

Comparing the partial cooling and recompression cycles for a 50 MWe sCO2 CSP plant using detailed recuperator models

Supercritical carbon dioxide (sCO2) power cycles are attractive for renewable energy technologies as they exhibit high thermal efficiencies, compact components, and reduced cycle complexity and levelized cost of energy (LCOE) relative to traditional steam power cycles. Consequently, numerous studies have investigated different layouts and operating parameters in search of an optimal cycle configuration. Two cycle layouts provide promising results, namely the partial cooling with reheating (PCRH) cycle, and the recompression with intercooling and reheating (RCICRH) cycle. Both cycles utilise recuperators with high heat transfer rates and literature suggests that the cost for the recuperators may account for a significant portion of the total plant capital expenditure. When modelling the recuperator, most cycle comparative studies employ simplified recuperator models where heat exchanger effectiveness or conductance is utilised to approximate heat transfer. These models do not consider the effect of recuperator size and geometry on heat transfer and pressure drop in detail. In this work, for a concentrated solar power (CSP) application, the performance and component size requirements of the cycles are evaluated parametrically for different cycle mass flow split ratios, pressure ratios, and ratio of pressure ratios across the compressors using detailed discretised one-dimensional (1D) recuperator models. Furthermore, the geometry of these models are optimised (by volume) for straight and zigzag channel printed circuit heat exchangers (PCHEs), widely accepted as the most suitable for this application. Finally, a high-level cost comparison is conducted. The results show that if appropriate pressure drop assumptions are made, a simplified model approach yields valid cycle level results when compared with the results obtained using detailed models which consider practical recuperator geometry. However, the pressures and temperatures within the recuperator may not be predicted to a sufficient level of accuracy. In addition to providing clarity regarding the interplay between key cycle process parameters and cycle performance, straight channel PCHEs provide better thermofluid performance than zigzag channel PCHEs. Furthermore, the RCICRH cycle requires larger turbomachinery and a marginally higher capital outlay for the power cycle, but offers superior thermal efficiencies and requires smaller heat exchangers. For sCO2-CSP applications employing dry cooling, this suggests that the RCICRH cycle requires a smaller solar field and cooling system, and may therefore offer increased revenue in adverse weather conditions where direct normal irradiance (DNI) is low and/or ambient temperatures are high. However, the PCRH cycle requires a smaller solar receiver system, a smaller thermal energy storage (TES) system, and smaller turbomachinery, the cost savings of which may outweigh the benefits of the RCICRH cycle.

Identification of Dynamic Force Coefficients for an Additively Manufactured Hermetic Squeeze Film Bearing Support Damper Utilizing a Pass-Through Channel

Abstract The following paper presents breakthrough experimental results for a new hermetic squeeze film damper (HSFD) concept that is integrally designed within an externally pressurized tilting-pad radial gas bearing support. The flexibly damped gas bearing module was designed for a 7.2″ (183 mm) diameter shaft and fabricated using direct metal laser melting (DMLM); also known as additive manufacturing. The bearing and HSFD were sized based on ongoing studies for oil-free supercritical carbon dioxide (sCO2) power turbines in the 8.5 MW–10 MW power range. The development of the new damper concept was motivated by past dynamic testing on HSFD, which generated frequency-dependent stiffness and damping force coefficients. In efforts to eliminate the frequency dependency, a new HSFD architecture was conceived that adds accumulator volumes and a pass-through channel to previously conceived HSFD flow network designs. The other motivation for the work is the need to develop a cost-effective and reliable oil-free bearing technology that is scalable to large power turbomachinery applications. There were several objectives for the following work. The first objective was to successfully design and fabricate a single piece bearing-damper using additive manufacturing, while dimensionally controlling critical design features. The paper discusses the manufacturing steps and shows cut-ups that reveal adequate clearance control capability with internal damper clearances. The second objective was to perform experimental testing with the new HSFD design in efforts to extract stiffness and damping coefficients for excitation frequencies within 20–160 Hz and peak vibration amplitudes between 0.25 mils (6.35 microns) to 1 mil (25.4 microns). The test results for a single HSFD bearing module indicated that the design modifications to the HSFD architecture were successful in eliminating nearly all the frequency dependencies for the stiffness force coefficient. The dynamic tests yielded a stiffness coefficient that varied between 112 klb/in. (19.6 MN/m) and 96 klb/in. (16.8 MN/m). The damping force coefficient however, exhibited relatively more variation with frequency with values residing between 175 lb-s/in. (31 kN-s/m) to 214 lb-s/in. (37 kN-s/m). Finally, the paper advances a three-dimensional fluid-structure interaction (FSI) model using transient finite element analysis (FEA) coupled to a computational fluid dynamics (CFD) model. The FSI analysis performed between 20 Hz and 80 Hz was used to predict the stiffness and damping of the HSFD using a quarter-section model of the damper. The FSI analysis was able to support test results by showing only a 6–7.4% change in the magnitude of force coefficients. Stiffness predictions agree reasonably well with experiments whereas damping is underpredicted.

Thermodynamic Modelling, Technical and Operational Issues of Supercritical Carbon Dioxide Power Generation Cycles for Industrial Applications: A Literature Review

Future electricity production systems will be able to harness the power of supercritical carbon dioxide (S-CO<sub>2</sub>) as it moves through thermal cycles. It serves the same goal as sources of energy such as fossil fuels, nuclear power, solar power, and the recovery of waste heat (or surplus heat from industrial processes). When the heat source temperature is between 350°C and 800°C, CO<sub>2</sub> as a working fluid exhibits excellent thermal efficiency. Its novel technological benefits over conventional steam Rankine cycles, such as the use of small turbo gear and compact heat exchangers, have captured the attention of scientists. It has excellent operational flexibility and may induce significantly cheaper energy costs. Aligned with these goals, this paper presents a panoramic work, exploring the current state of the art of S-CO<sub>2</sub> power generation, with a particular emphasis on the technical and operational perplexities. After providing a comprehensive overview of the thermodynamic principles that underpin this study, the foundation is established for an engaging discourse on the continuous research and development of supercritical carbon dioxide (S-CO<sub>2</sub>) cycles in power generation. Upon delving into the thermodynamic facets of CO<sub>2</sub> that propel this investigation, the spotlight is cast upon dissecting the existing state of research and development of S-CO<sub>2</sub> cycles in power generation before transitioning into encapsulating the principal domains of application and noteworthy thermodynamic modelling inquiries of S-CO<sub>2</sub> cycles. The present advancements and hurdles within the primary application areas are succinctly summarized, while future research trends are identified.

A novel supercritical carbon dioxide combined cycle fueled by biomass: Thermodynamic assessment

As a carbon-neutral type of renewable energy, biomass is beneficial for reducing carbon emissions in the electricity sector. A biomass gasification process integrated with a combined cycle is proposed here. Wood is chosen as the fuel and air as the gasifying agent. A supercritical carbon dioxide (SCO2) power cycle with recompression is selected for the recovery of waste heat from the combustion chamber. The net power output is considered to be 1 MW for the combined cycle in the investigation of component ratings and biomass feed rate. For a comprehensive thermodynamic analysis of this combined cycle, we examine three key parameters: gas turbine inlet temperature (1200–1400 K), topping cycle pressure ratio (5-10) and CO2 turbine inlet temperature (600–700 K). The maximum energy efficiency is achieved for the system at a specific pressure ratio and CO2 turbine inlet temperature. The energy efficiency rises with gas turbine inlet temperature, which reduces biomass consumption (at a fixed net power output). The CO2 emission rate to the environment is examined for various parameters; it is observed to decrease as biomass consumption decreases and to take on a value of 0.254 kg/s at an optimized state.

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.

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.