Supercritical Carbon Dioxide Cycle Research Articles

Optimizing Supercritical Carbon Dioxide Cycles Performance With Respect to Split Ratio and Intermediate Pressure

Abstract Supercritical carbon dioxide power cycles are getting more attention every day due to their high efficiencies. This study has examined determination of split ratio and intermediate pressure for maximum efficiency in various supercritical carbon dioxide recompression cycle configurations. Five cycle variants have been analyzed: reheating, partial cooling, partial cooling with reheating, intercooling, and intercooling with reheating. Partial derivatives of efficiency with respect to split ratio and intermediate pressure have been determined and set equal to zero to find optimum split ratio and intermediate pressure. This process has isolated the system's response to these two key parameters while keeping other cycle variables constant. Across all configurations, following parameters have been fixed: inlet temperatures of 550 °C and 32 °C for turbine and compressor components, an energy source temperature of 600 °C, an ambient temperature of 27 °C, and pressure limits of 75 bar and 200 bar. Optimization results show that recompression–reheating cycle achieves the highest efficiency of 39.62% at an optimum intermediate pressure of 139.43 bar and a split ratio of 71.1%. Recompression–partial cooling cycle exhibits the lowest maximum efficiency at 37.35%, with an optimum intermediate pressure of 85.87 bar and a split ratio of 62.6%. Recompression–partial cooling with reheating cycle reaches a maximum efficiency of 37.98% at an optimum intermediate pressure of 123.94 bar and a split ratio of 67.2%, while the intercooling cycle and intercooling with reheating cycle attain 39.57% at an optimum intermediate pressure of 80.03 bar and a split ratio of 66.4% and 39.59% at an optimum intermediate pressure of 116.1 bar and a split ratio of 69.2%, respectively. Additionally, exergy destruction has been calculated for all components of the system and it is related to thermal efficiency of the cycle.

Optimizing Energy Recovery from Marine Diesel Engines: A Thermodynamic Investigation of Supercritical Carbon Dioxide Cycles

Optimizing Energy Recovery from Marine Diesel Engines: A Thermodynamic Investigation of Supercritical Carbon Dioxide Cycles

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.

Thermodynamic and exergoeconomic evaluation of coal and biomass co-gasification as solid oxide fuel cell feed coupled with supercritical carbon dioxide and organic Rankine cycle

Coal-biomass cogeneration technology can not only diversify energy supply, but improve the combustion characteristics of coal and enhance system performance. This work developed a power generation system for co-gasification of coal and biomass to supply solid oxide fuel cell, and coupled with a dual system of supercritical carbon dioxide cycle and organic Rankine cycle to achieve energy cascade utilization. A comprehensive thermodynamic analysis was conducted to evaluate and optimize this system more intuitively. Constrained optimization algorithms elucidated the optimal parameters, identifying an oxygen-to-fuel mass ratio of 0.48 and a steam-to-fuel ratio of 0.18. These conditions led to a higher gasification temperature and optimal syngas yield. And sensitivity analysis on three biomass types confirms that dry and carbon-rich biomass is ideal for system doping. With a 20% doping amount, the system achieves 59.18% maximum thermal efficiency and 2.43 kg/MWh net carbon emission, outperforming the single fuel cell system by 11.14% and 4.79% respectively. The discount rate has the greatest impact on system costs in economic analysis, with a 30% fluctuation causing system costs to vary by about 14.31%. In addition, the exergy and exergoeconomic analyses identify cost formation, propose efficiency measures, and enhance cost-effectiveness.

An innovative S–CO2 recompression Brayton system and its thermodynamic, exergoeconomic and multi-objective analyses for a nuclear spacecraft

An innovative layout of a recompression supercritical carbon dioxide (S–CO2) cycle for nuclear spacecraft was proposed in this work. Thermodynamic and exergoeconomic analysis of the innovative cycle have been performed to study the effect of essential operating parameters on the split ratio, maximum operating pressure ratio, minimum operating temperature, maximum operating temperature, and compressor C4 inlet pressure based on the first and second laws of exergoeconomics and efficiency. Finally, the innovative power cycle is optimized with high efficiencies, low cost and lightweight. The results show that the optimization progress is based on the thermodynamic and exergoeconomics method; the minimum operating temperature can significantly improve efficiencies and reduce circular investment cost; then after the multi-objective optimization progress, the thermal efficiency (ηth), exergy efficiency (ηex) and mass of Brayton turbomachinery unit (MBTU) improved by 2.71 %, 3.69 %, and 2.8 %; total capital cost rate (total) and levelized cost of electricity (LCOE) reduced by 0.88 % and 4.55 %, respectively.

Thermodynamic evaluation of a state-of-art poly-generation system fueled by natural gas and biomass for cooling, power, and hot water generation

The principal objective of this study was to conduct a thorough examination of the thermodynamic aspects of an innovative combined poly-generation facility, encompassing cooling load, hot water, and power generation cycles, powered by a combination of natural gas and biomass. A distinctive feature was the incorporation of syngas into natural gas to enhance overall plant performance. The plant design comprised three key subsystems: a gasification and combustion chamber, a double-effect absorption chiller, and a supercritical carbon dioxide cycle. Energy and exergy analyses were employed to systematically evaluate the thermodynamic behavior of the plant. The outcomes revealed that the exergy and energy efficiencies, along with the net power output, were determined to be approximately 35 %, 78 %, and 7422 kW, respectively. Additionally, the produced hot water and the coefficient of performance (COP) of the absorption chiller were estimated at around 14.71 kg/s and 1.209. Notably, the gasifier and combustion chamber emerged as the least efficient components of the system, primarily due to their elevated rates of exergy destruction. Furthermore, comprehensive parametric investigations were conducted to elucidate the influence of key variables on plant performance. The analysis indicated that variations in gasification temperature positively impacted the thermodynamic performance of the plant. Moreover, an increase in combustion pressure led to a notable enhancement in the net power output of the facility.

New procedure for an optimal design of an integrated solar tower power plant with supercritical carbon dioxide and organic Rankine cycle and MED-RO desalination based on 6E analysis

In this paper, an innovative structure for the production of electricity and freshwater in Kangan Port, located in southern Iran and close to the Persian Gulf, is developed and analyzed. Heliostat collectors are employed in this process to provide the necessary thermal energy in the supercritical carbon dioxide (S-CO2) cycle, the organic Rankine cycle (ORC) and desalination unit. Additionally, implementing the current multi-effect desalination (MED) processes unit with the reverse osmosis (RO) system as well as employing the sun's thermal collector field to enhance the system's achievement and propose the best plan for the unit that operates has been looked into. ASPEN HYSYS software, Meteonorm package, and MATLAB programming are used to simulate the proposed system. Concurrently, this integrated power plant exhibits the capacity to simultaneously generate 117 kg/s of freshwater and yield 25.14 MW of power. The integrated structure has a thermal efficiency of 36% and a overall exergy efficiency of 31.99. Exergy study reveals that heat exchanger 8 and turbine 3 experience the most exergy destruction. To recover lost heat and produce additional electricity, organic Rankine cycle are used. Investigations are done on seven organic fluids in the ORC unit. The system is better understood from several views with the assistance of energy, exergy, exergoeconomic, exergoenvironmental, emergoeconomic, and emergoenvironmental (6E) analyses. In this regard, m-file codes in MATLAB programming for 6E analyses are developed. The generated code's thermodynamic simulation is accurately compared to ASPEN HYSYS software. Additionally, sensitivity analysis depending on the primary parameters is carried out. For a thorough study of each component, advanced exergy-based analysis linked to avoidable/endogenous and unavoidable/exogenous segments is carried out. The objective functions and chosen variables are optimized using a genetic algorithm. The best organic fluid in terms of thermodynamics is n-hexane and the ideal organic fluid from an economic and environmental standpoint stands R-113. The overall system's cost rate and environmental impact are obtained at 0.1679 $/s and 0.000545 pts/s, respectively.

Comparative analysis of supercritical CO2–ORC combined cycle for gas turbine waste heat recovery based on multi-objective optimization

To efficiently recover the waste heat of the gas turbine, this study introduces six innovative types of compound combined cycles, and proposes a multidimensional optimization method for the optimal cycle. In the combined cycle, the supercritical carbon dioxide cycle is used in the top cycle and the organic Rankine cycle is used in the bottom cycle. The working medium used in the organic Rankine cycle is the innovative mixture cyclopentane/R365mfc. Firstly, a parametric study is carried out for the proposed combined cycle to investigate the effects of system operating parameters on exergy efficiency, area per unit power output (APR) of the heat exchanger, and the levelized energy cost (LEC). The results show that the optimal values of objective function correspond to different systematic operating parameters. Secondly, the multi-objective optimization based on the genetic algorithm is used to obtain the optimal systematic parameters, and the six proposed composite combined cycles are optimized respectively. The comparison results show that the composite supercritical carbon dioxide regenerative cycle-organic Rankine simple cycle has the optimal performance parameters, and its exergy efficiency, APR and LEC are 55.68 %, 0.115 m2/kW and 4.23 cent/(kW·h), respectively. The layout of the composite cycle is that the supercritical carbon dioxide regenerative cycle and the organic Rankine simple cycle are used to recover the high temperature and low temperature of the gas turbine exhaust gas, while the organic Rankine simple cycle recovers the cooling heat of the supercritical carbon dioxide regenerative cycle. Finally, the superiority relative of the proposed combined system to the other cycles is also verified. This study has determined that the proposed combined system is appropriate for the waste heat recovery of gas turbines, with the advantages of deep utilization of waste heat, high efficiency, high compactness, and low cost.

Development and assessment of a novel integrated system powered by parabolic trough collectors for combined power, heating and freshwater production

Abstract Hybrid solar-based integrated systems represent a viable solution for countries with abundant solar radiation, as they provide energy needs in an environmentally friendly way, offering a sustainable and economically advantageous energy solution that utilizes a free source of energy. Therefore, this research offers a thermodynamic evaluation of a novel integrated system driven by solar energy that aims to produce power, heating and freshwater. The integrated system consists of a parabolic trough collector that uses CO2 as its working fluid and implements the supercritical carbon dioxide cycle to generate power and heating. The integrated system also includes an adsorption desalination system with heat recovery between the condenser and evaporator, which employs a cutting-edge material called an aluminium fumarate metal–organic framework to produce fresh water. For the modelling of a novel system, an engineering equation solver, which is considered a reliable tool for thermodynamic investigations, is employed. The effectiveness of an integrated system is evaluated using a mathematical model and different varying parameters are examined to ascertain their influence on thermal and exergy efficiency, specific daily water production and gained output ratio. The results revealed that the parabolic trough collector achieved a thermal efficiency of 67.2% and an exergy efficiency of 41.2% under certain conditions. Additionally, the thermal efficiencies for electrical and heating were obtained 24.68% and 9.85%, respectively. Finally, the specific daily water production was calculated, showing promising results and an increase from 7.1 to 12.5 m3/ton/day, while the gain output ratio increased from 0.395 to 0.62 when the temperature of hot water increased from 65°C to 85°C, under the selected conditions.

Design and analysis of an innovative biomass-powered cogeneration system based on organic flash and supercritical carbon dioxide cycles

Technological advancements play a significant role in increasing energy demand. As societies progress, new technologies emerge, and they often require additional energy resources to operate. Therefore, it is important to design an efficient power system that can achieve higher performance. Additionally, considering the environmental aspect of the designed system is another crucial criterion for power system design. The current investigation proposes a renewable-based co-generation system for the production of power and heating load. The proposed system consists of several subsystems, including a municipal solid waste-driven gas turbine cycle, a supercritical CO2 cycle, and a high-temperature organic flash cycle. The system's performance is analyzed using energy, exergy, economic, and environmental approaches. Double-objective and triple-objective optimizations are applied to determine the optimum state of the system. The results indicate that the system can produce a net power of 8.21 MW and a heating load of 5.81 MW. This translates to energy and exergy efficiencies of 75.8 % and 41.21 % respectively, with a levelized CO2 emission of 0.518 t/kWh at the base-case. Furthermore, the system's payback period is estimated to be approximately 1.97 years, resulting in a net profit of 10.7 M$. In the parametric study, it was found that the gas turbine's inlet temperature has a significant impact on the system's performance indexes. Ultimately, the system achieves an exergy efficiency of 43.18 % and a levelized CO2 emission of 0.457 t/kWh at the optimum state. In conclusion, the proposed renewable-based co-generation system offers a promising solution for achieving higher performance, environmental sustainability, and economic viability in the design of efficient power systems. In conclusion, the proposed renewable-based co-generation system offers a promising solution for achieving higher performance, environmental sustainability, and economic viability in the design of efficient power systems.

Simulation and multi-objective assessment of an environmentally friendly trigeneration system powered by biogas from landfilling using a novel cascade heat integration model

This study introduces a novel integrated trigeneration system fed by biogas fuel from landfilling, promoting environmentally sustainable practices. In the system proposed within this study, fuel combustion occurs through the implementation of a gas turbine cycle, while the subsequent waste heat is efficiently recuperated within a cascade framework. The combustion process is combined with a supercritical carbon dioxide cycle, an organic Rankine cycle, an ammonia Rankine cycle, a seawater desalination unit, and a Kalina cycle. The process is simulated using the Aspen HYSYS software while conducting a comprehensive analysis encompassing the energy, exergy, economic, and environmental aspects. In view of the thermodynamic perspective, the analysis yields values of 70.28%, 24.89%, and 57.51% for the energy utilization factor, and thermal and exergy efficiencies, respectively. The subsequent environmental results illustrate that the proposed scheme exhibits a carbon dioxide emission level of 0.272 kgCO2/kWh, yielding a noteworthy reduction of 51.02% in carbon dioxide emissions compared to a traditional power and heat generation system. Besides, the economic analysis demonstrates a positive net present value of 779, 571, 045 $ for the proposed process. Furthermore, the total unit cost of products and cost of energy are found at 12.25 $/GJ and 0.022 $/kWh, respectively.

Thermodynamic and economic analysis of a conceptual system combining medical waste plasma gasification, SOFC, sludge gasification, supercritical CO2 cycle, and desalination

In order to improve the utilization of energy in solid waste, we propose a coupled system consisting of medical waste plasma gasification, solid oxide fuel cell (SOFC), sewage sludge gasification (SSG), supercritical carbon dioxide cycle (S–CO2) and multi-stage flash (MSF) desalination. The medical waste is plasma gasification and purified to produce clean syngas, which is used by the SOFC to generate electricity. the exhaust from the SOFC is mixed with crude gas from the sludge gasification to fully combust and release chemical energy while increasing the exhaust temperature. Finally, the high-temperature energy enters the waste heat utilization system consisting of S–CO2 and seawater desalination to be fully utilized. A thermodynamic and economic analysis of the proposed system shows that the hybrid system has a net power generation efficiency of 41.66%, an energy utilization efficiency of 64.95%, and an exergy efficiency of 41.25%. The plasma gasifier and SOFC are the main sources of exergy loss, accounting for 62.45% of the total destroyed exergy. The DPP of the project is only 4.4 years over a 20-year operating cycle, with an NPV of 117,652.81k$. This study demonstrates the advantages and benefits of the project in terms of solid waste resource utilization.

Techno-economic and environmental optimization of a combined regenerated gas turbine and supercritical CO2 cycle based on methane and hydrogen mixture as fuel for environmental remediation

Achieving power generation systems with high efficiency and low emission of environmental pollutants is one of the requirements of a sustainable environment. In this study, a hybrid power generation system based on gas turbine (GT) with regenerator configuration is introduced. A supercritical carbon dioxide (sCO2) cycle is used to recover the waste heat from GT exhaust gases. In order to reduce the emission of environmental pollutants, the combination of hydrogen and methane is used as GT fuel. In order to investigate the effect of using hydrogen in the fuel composition, the fraction of hydrogen is changed between 0 and 50% and its effect on performance, environmental, and economic factors is investigated. Also, the effect of design parameters such as compressor pressure ratio (CPR) and turbine inlet temperature (TIT) of GT and sCO2 cycles on exergy efficiency, total cost rate (TCR), and normalized pollutants emission index are investigated. Then, by performing a bi-objective optimization process with the aim of achieving maximum exergy efficiency and minimum TCR, the optimal operating point is extracted. At the optimal operating point, exergy efficiency is 44% and TCR is 6 dollars/second.

Simulation and 4E analysis of a novel trigeneration process using a gas turbine cycle combined with a geothermal-driven multi-waste heat recovery method

A novel hybrid system using geothermal energy and fuel gas in a co-feed structure is proposed. The main objectives include improving the sustainability of a gas turbine cycle associated with a geothermal power plant and reducing carbon emissions. To this end, a novel multi-waste heat recovery process was developed in which the heated airflow in the gas turbine cycle was directed to the geothermal flash cycle to increase the viability of the flash process in this unit. A parallel heat recovery structure then used part of the waste heat from the gas turbine cycle to start a supercritical carbon dioxide cycle and also improve the performance of the geothermal flash cycle. Hence, two organic Rankine cycles were used in the geothermal flash cycle. The other part of the waste heat from the gas turbine cycle was consumed in a cascade framework in a steam Rankine cycle and a desalination plant in combination with a domestic water heater. The defined structure was simulated and a comprehensive study was done from the viewpoints of energy, exergy, environment, and thermoeconomics. This structure reduced the total irreversibility as well as the carbon dioxide emissions compared to the existing literature data.

Multi-objective optimisation of a power generation system integrating solid oxide fuel cell and recuperated supercritical carbon dioxide cycle

This article presents an advanced power generation system that integrates a solid oxide fuel cell (SOFC) module with a recuperated supercritical CO2 (s-CO2) cycle. The waste heat generated by the exhaust of the SOFC module is utilised to drive the s-CO2 cycle, resulting in enhanced energy efficiency. The performance of the system was investigated through thermodynamic and economic analyses and optimised using response surface methodology. The optimisation process focused on two objectives: maximising the energy efficiency of the integrated system and minimising the levelised cost of electricity. The study meticulously analysed the effects of important variables such as current density, fuel utilisation factor, and operating temperature of the fuel cell. The optimisation efforts yielded impressive results, achieving an energy efficiency of 64% and a levelised cost of electricity (LCOE) of 0.18£/kWh. The proposed system surpassed traditional natural gas-fuelled power plants in terms of efficiency and specific emissions. Furthermore, the system's performance was evaluated when operated with green hydrogen fuel, which led to a substantial improvement in efficiency, estimated at 73.37%. However, it was found that the LCOE of the system is relatively higher and approximately 15% higher than the methane-based alternative.

Techno-environmental assessment and machine learning-based optimization of a novel dual-source multi-generation energy system

The utilization of high-temperature hybrid energy systems has a vital and promising role in reducing environmental pollutants and coping with climate change. So, in the present research, a dual-source multigeneration energy system composed of a gas turbine, a supercritical carbon dioxide recompression Brayton cycle, an organic Rankine cycle, an absorption refrigeration system, and a reverse osmosis desalination unit is designed and analyzed from thermodynamic, environmental and economic perspectives. The system supplies power with a stable load to follow the changes in the demand side which is important for off-grid distributed energy systems. The dual-source operation of the system makes it possible to generate sustainable electricity leading to less utilization of fossil fuels in the gas turbine subsystem and reduction in environmental pollution, and furthermore, malfunctioning of a subsystem will not lead to the failure of the entire plant. Three multi-objective optimizations with different objective functions are accomplished using artificial neural network from data learning and genetic and Greywolf algorithms to obtain the best-operating conditions. Under the base conditions, for the total input energy of 699 MW to the entire system, the energy and exergy efficiencies, the unit exergy cost of products, the carbon dioxide emission index, and the payback period, respectively, were found to be 45 %, 54 %, 15.3 $/GJ, 112.2 kg/MWh, and 7.2 years. The net output power of the proposed system was calculated as 288.2 MW. A sensitivity analysis revealed that with a change in the pressure ratio of the supercritical carbon dioxide cycle, the net generated power and overall efficiency take maximum values of 293.9 MW while the unit exergy cost of products and carbon dioxide emission index take minimum values of 15.3 $/GJ and 110.1 kg/MWh, respectively. Furthermore, increasing the pressure ratio of the gas turbine leads to maximum values of 45 % and 54 % in overall energy and exergy efficiencies, respectively.

Tri-objective optimization of a waste-to-energy plant with super critical carbon dioxide and multi-effect water desalination for building application based on biomass fuels

In the present research, an innovative biomass-based energy system for the production of electricity and desalinated water for building application is proposed. The main subsystems of this power plant include gasification cycle, gas turbine (GT), supercritical carbon dioxide cycle (s-CO2), two-stage organic Rankine cycle (ORC) and MED water desalination unit with thermal ejector. A comprehensive thermodynamic and thermoeconomic evaluation is performed on the proposed system. For the analysis, first the system is modeled and analyzed from the energy point of view, then it is examined similarly from the exergy point of view, and then an economic analysis (exergy-economic analysis) is performed on the system. Then, we repeat the mentioned cases for several types of biomasses and compare them with each other. Grossman diagram will be presented to better understand the exergy of each point and its destruction in each component of the system. After energy, exergy and economic modeling and analysis, the system is analyzed and modeled using artificial intelligence to help the system optimization process, and the model obtained with genetic algorithm (GA) to maximize the output power of the system, minimize the cost system and maximizing the rate of water desalination is optimized. The basic analysis of the system is analyzed inside the EES software, then it is transferred to the MATLAB software to optimize and check the effect of operational parameters on the thermodynamic performance and the total cost rate (TCR). It is analyzed and modeled artificially and this model is used for optimization. The obtained result will be three-dimensional Pareto front for single-objective and double-objective optimization, for work-output-cost functions and sweetening-cost rate with the specified value of the design parameters. In the single-objective optimization, the maximum work output, the maximum rate of water desalination, and the minimum TCR will be 55,306.89 kW, 17216.86 m3/day, and $0.3760/s, respectively.

Process simulation and economic evaluation of a biomass oxygen fuel circulating fluidized bed combustor with an indirect supercritical carbon dioxide cycle

In recent years, the utilization of biomass through advanced power technologies has intensified to achieve carbon neutrality. An oxy-fuel circulating fluidized bed combustor of biomass with higher efficiency supercritical carbon dioxide cycle has been developed with the aim of compensating the penalties for carbon capture and storage. The combustor fuelled with waste paper, waste wood, and cow manure, at an input of 200 ton/day is economically evaluated. Waste paper is on the verge of becoming an economically feasible fuel, more so than the other biomass examined. The use of waste paper led to a positive net present value, an internal rate of return of 3.8%, a benefit-cost ratio of 1.025, and a payback period of 17.7 years. Subsequent sensitivity analyses conducted for the waste paper fuelled power plant indicated that the capital cost is the most influential factor; the boiler, supercritical carbon dioxide cycle, and oxygen fuel combustion system were indicated in descending order of related subdivided sensitiveness. Both renewable energy certificate and carbon credit has contributed to the feasible economic of the system, with former one took precedence over later one. Sensitivity from the technical perspective, improvement in air separation unit is likely to greatly improve the economic feasibility of the proposed system. The power consumption of the air separation unit, as well as that of the carbon dioxide compression and purification unit, were highly sensitive to the implementation cost.

Improved coordinated control strategy of coal-fired power units with coupled heat storage based on supercritical carbon dioxide cycle

With the rapid development of intermittent renewable energy sources, operating a power generation system, like coal-fired power plants that can ensure supply stability, has become increasingly challenging. In this study, an additional supercritical CO2 (sCO2) cycle is incorporated into coal-fired power units to improve load regulation capability. First, a dynamic model of the coal-fired power unit with the additional sCO2 cycle is established. Two improved coordinated control systems are designed to improve the power ramp rate, i.e., a switching controller and a dual controller. Finally, a 330 MW coal-fired power plant was simulated. The results show that the proposed control method could effectively improve the load response characteristics. The integral of the absolute error (IAE) index and integral of the time square error (ITSE) index, of the coordinated control system based on dual control, were superior to those of the standard coordinated control system. The automatic generation control (AGC) performance indicators were found to be 9.03 and 8.76 in the load rise and decrease stages, respectively. Thus, the study provides a new direction for the application of sCO2 cycles in the field of coal-fired power generation.

Multi objective optimization and 3E analyses of a novel supercritical/transcritical CO2 waste heat recovery from a ship exhaust

Waste heat recovery systems are a promising solution to reduce the overall energy consumption. These systems are capable of producing energy from both high grade and low-grade waste heat without producing any pollution. This paper proposes a novel waste heat recovery system installed on a ship that can produce power and cooling by supercritical/transcritical CO2 waste heat recovery. For this purpose, supercritical and transcritical carbon dioxide cycles are integrated in a special configuration to recover the highest amount of energy in the ship. To analyze the system, 3E analyses (Energy, Exergy, and Economic) are utilized. Then, to achieve the best performance, the most important and influential parameters have been optimized with the aim of increasing energy, exergy efficiency, and reducing the capital cost. Based on the obtained results, energy, exergy efficiency, and capital cost of the plant reaches 69.6%, 42.3%, and 2.5 M$ respectively in the best condition. Finally, at design condition, the system produces a net power of 9.061 kW and 19.522 kW of cooling.