To achieve low-carbon economic operation of hydrogen-doped integrated energy systems while mitigating the stochastic impact of new energy outputs on the system, the coordinated operation mode of hydrogen-doped gas turbines and electrolyzers is focused on, as well as a hybrid energy storage scheme involving both hydrogen and heat storage and an optimized scheduling model for integrated energy systems encompassing electricity-hydrogen-heat-cooling conversions is established. A model predictive control strategy based on deep learning prediction and feedback is proposed, and the effectiveness and superiority of the proposed strategy are demonstrated using error penalty coefficients. Moreover, the introduction of hydrogen energy exchange and ladder carbon trading is shown to effectively guide the low-carbon economic operation of hydrogen-doped integrated energy systems across multiple typical scenarios. A sensitivity analysis is conducted based on this framework, revealing that increases in the hydrogen doping ratio of turbines and the carbon base price led to higher system operation costs but effectively reduce carbon emissions.

The supercritical carbon dioxide (sCO₂) cycle can be powered by traditional as well as clean energy. To help users obtain more accurate results than the literatures with pre-set compressor efficiency, we proposed a complete model to establish a link between the performance, sizes of compressors and parameters such as power W_C, inlet temperature T_in, inlet pressure P_in and pressure ratio ɛ. Characteristic sizes of compressors l_c, profile loss Y_p and clearance loss Y_cl are all proportional to powers of W_C with powers of 0.5, –0.075 and –0.5 to 0 respectively; the scaling laws are constant in the range of capacities from 20 MW to 200 MW. The compressor isentropic efficiency η_tt grows as the W_C increases, and the curves become gentle. Compressor efficiency improves over the full power range when the speed is changed from standard speed to the optimal speed; the η_tt curves turn soft as the n increase. As the P_in and T_in approach the critical point, the η_tt increase. Compressor efficiency follows a parabolic curve as the ɛ increases, this parabolic distribution results from the tradeoff between the change in losses and the pressure distribution of blades. The η_tt versus P_in, Tin and ɛ relations are similar at various capacities because of insignificant changes in the distribution of losses. Compressor efficiency maps facilitate the estimation of system performance, while scaling law for irreversible losses and characteristic lengths, along with constant criterion analyses, aid in comprehending the characteristics of compressors across various capacities.

With a broad range of application prospects, hydrogen fuel cell technology is regarded as a clean and efficient energy conversion technology. Nevertheless, challenges exist in terms of the safe storage and transportation of hydrogen. One proposed solution to this problem is the utilization of methanol on-line steam reforming technology for hydrogen production. In this paper, an integrated system for in-situ steam reforming of fuel coupled with proton exchange membrane fuel cells (PEMFC) power generation is proposed, and sensitivity analysis and exergy sensitivity analysis are conducted. Through the gradual utilization of waste heat and the integration of the system, fuel consumption is reduced and the power generation efficiency of the system is improved. Under the design operating conditions, the power generation efficiency and exergy efficiency of the system are achieved at 44.59% and 39.70%, respectively. This study presents a proven method for the efficient integration of fuel thermochemical conversion for hydrogen production with fuel cells for power generation, highlighting the advantages of complementary utilization of methanol steam reforming and PEMFC.

Thermally regenerative electrochemical cycle (TREC) is a novel and effective heat-to-electricity technology for harvesting low-grade heat. Currently, reported TREC analyses have been based on the Stirling cycle of ideal infinite heat source and infinite time for heat transfer. However, this will lead to inaccuracy when the scenario deviates from the ideal case. In this study, a systematic thermodynamic analysis on TREC is performed to address this problem. Based on different heat transfer situations, the description of thermodynamic processes and the corresponding mathematical models are established. At the same time, the TREC system, with the solar collector as the high-temperature heat source and the environment as the low-temperature heat source, is employed as a case. And the study delved into discrepancies arising from incongruences between the practical operational process and the traditional ideal analytical methodologies, along with an investigation of the different thermal environment impact on system performance. The findings suggest that the finite analysis method should be used when the actual operating time of the system is shorter than the desired equilibrium period. On the contrary, the use of the infinite analysis method, in this case, produces an error, the magnitude of which is directly related to the operating time, whereas when the time reaches 80% of the equilibrium time the error can be controlled to less than 2%. The influence of the heat source on the operating phase of the system is mainly in the temperature equilibrium and the rate of temperature equilibrium. This effect is proportional to the thermal capacitance and is also positively related to the system performance. Therefore, to improve system performance, it is recommended that a high-temperature heat source with a high ratio of thermal capacitance to system thermal capacitance should be selected and that the response time should slightly exceed the system equilibrium duration.

The exploitation of photovoltaic/thermal (PV/T) systems, which facilitate concurrent conversion of solar radiation into electrical and heat energies, presents substantial potential in the solar-abundant northwestern zone of China. This investigation endeavors to evaluate the efficacy of a micro heat pipe (M-HP) PV/T system via exhaustive experimental analysis conducted in Lanzhou. To improve the performance of M-HP-PV/T system, a comparison was made between the optimal angles for each day and the entire year. The system inside greenhouse exhibited an average photovoltaic conversion efficiency (PCE) and thermal conversion efficiency (TCE) of 12.32% and 42.81%. The system of external environment registered average PCE and TCE values of 12.99% and 21.08%. To further understand the system’s operational results, a mathematical model was constructed through the integration of experimental data, exhibiting good agreement between the simulated outcomes and empirical observations. The average solar irradiance of daily optimum angle was 728.3 W/m²; the annual optimum angle was 29° with an average solar irradiance of 705.6 W/m². The average annual total powers at the optimal angle outside the greenhouse and inside the greenhouse were 448.0 W and 398.7 W. The average annual total efficiencies at the optimal angle outside the greenhouse and inside the greenhouse were 40.8% and 56.9%. The total power in the greenhouse was lower by 49.3 W, while total efficiency in the greenhouse was higher by 16.1%.

Water is a recyclable resource and the largest energy carrier on Earth. New hydropower generation technologies hold great promise for the future. However, there is a lack of evaluation standards for power generation performance. And, the mechanism of hydrovoltaic power generation lacks systematic clarity. In this study, a thermodynamic analysis method about hot and humid air energy conversion based on the principle of hydropower generation is established. To author’s knowledge, it is the first time that the maximum available energy of hydropower generation is analyzed by exergy and parametric calculations. The greater the difference, the higher the available energy. Also, a series of experiments were conducted to explore the power generation device materials, structural composition, and structural parameters, further clarifying the principle of electricity generation. And, the influence of temperature and relative humidity on the power generation performance was also studied. The increase in temperature can effectively increase the output electrical performance of the power generation. The open-circuit voltage and short-circuit current of water evaporation power generation with Al₂O₃ nanoparticles are higher than 2.5 V and 150 nA respectively. Through analysis, we propose relevant application strategies to provide theoretical and practical support for the development of green energy.

Hybrid nanofluids are known for their attractive thermophysical properties and enhanced heat transfer potential. This study thoroughly investigates the impact of particle mixing ratios on the thermophysical and heat transfer characteristics of MgO-SiO₂/water hybrid nanofluid. The mixing mass ratio (MR) of MgO:SiO₂ was systematically altered including ratios of 100:0, 80:20, 60:40, 50:50, 40:60, 20:80, and 0:100 at a fixed particle concentration of 0.01% in volume. Experimental assessments of thermal conductivity and viscosity were conducted within the temperature range of 25°C–50°C at 5°C intervals. Thermal conductivity was measured by analysing sonic velocity of sound in nanofluid medium. Viscosity was determined by Ostwald viscosity apparatus. Sensitivity analysis was performed to examine the influence of mixing ratio and temperature on thermal conductivity and viscosity. Sustainability and economic analysis were conducted to guide future applications. The findings highlight the substantial influence of MR on thermal conductivity and viscosity enhancements within the hybrid nanofluid. The thermal conductivity exhibited a positive correlation with temperature elevation, with the hybrid nanofluid at MR=60:40 and 50°C displaying the highest thermal conductivity enhancement at 20.84% compared to water. In contrast, viscosity decreased with increasing temperature, with MR=50:50 at 50°C showing the maximum viscosity increase at 5.06% compared to water. New data-driven correlations for precise predictions of thermal conductivity and viscosity of hybrid nanofluid have been proposed. Sensitivity analysis revealed that mixing ratio had a more pronounced impact than temperature elevation. Sustainability and economic analysis concludes that MR=60:40 is an optimal, economical and sustainable choice for achieving peak heat transfer performance. 

The introduction of fresh air into the indoor space leads to a significant increase in cooling or heating loads. Solid desiccant heat pump fresh air unit which can handle the latent and sensible load of fresh air efficiently have been proposed recently. To improve the performance of the solid desiccant heat pump fresh air unit in the fresh air handling process, in this paper, the application of composite silica gel in a heat pump fresh air unit was investigated. The comparison between silica gel coating (SGC) and composite silica gel coating (CSGC) shows that the adsorption rate and water uptake capacity of CSGC are more than two times higher than those of SGC. An experimental setup for the solid desiccant heat pump fresh air unit was established. The performance of SGC and CSGC was tested in the setup successively. Results show that under summer conditions, compared with the solid desiccant heat pump fresh air unit using silica gel (SGFU), the average moisture removal and COP of the one using composite silica gel (CSGFU) increased by 15% and 30%, respectively. Under winter conditions, compared with SGFU, the average humidification and COP of CSGFU increased by 42% and 17%. With optimal operation conditions of 3 min switchover time and 40 r/s compressor frequency, the COP of CSGFU under summer conditions can reach 7.6. Results also show that the CSGFU and SGFU have higher COP and dehumidification rate under higher outdoor temperature and humidity ratio.

In order to reduce the environmental impact of conventional sludge treatment methods and to utilize the energy in sludge more effectively, a coupled system based on sewage sludge gasifier (SSG), solid oxide fuel cells (SOFC), supercritical CO₂ cycle (S-CO₂), and organic Rankine cycle (ORC) is proposed. The clean syngas obtained from sludge gasification is mixed with CH₄ and then first utilized by the fuel cell. The exhaust gas from the fuel cell is fully combusted in the afterburning chamber and then enters the bottom cycle system consisting of S-CO₂ & ORC to generate electricity. To understand the performance of the system, thermodynamic and economic analyses were conducted to examine the project’s performance. The thermodynamics as well as the economics of the coupled system were analyzed to arrive at the following conclusions, the power production of the system is 37.34 MW; the exergy efficiency is 55.62%, and the net electrical efficiency is 61.48%. The main exergy destruction is the gasifier and SOFC, accounting for 62.45% of the total exergy destruction. It takes only 6.13 years to repay the construction investment in the novel system, and the project obtains a NPV of 17 723 820 USD during 20 years lifetime. The above findings indicate that the new coupled system has a better performance in terms of energy utilization and economy.

Coal-fired power plant is a major contributor to greenhouse gas emissions. The post-combustion capture is a promising method for CO₂ emission reduction but the high thermal demand is unbearable. To address this issue, solar thermal energy and CO₂ capture are jointly integrated into the coal-fired power plant in this study. The solar thermal energy is employed to meet the heat requirement of the CO₂ capture process, thereby avoiding the electricity loss caused by self-driven CO₂ capture. Furthermore, the heat released from the carbonation reaction of MgO adsorbent is integrated into the steam Rankine cycle. By partially substituting the extracted steam for feedwater heating, the electricity output of the power plant is further increased. According to the results from the developed model, the system could achieve a CO₂ capture rate of 86.5% and an electricity output enhancement of 9.8% compared to the reference system, which consists of a self-driven CO₂ capture coal-fired power plant and PV generation unit. The operational strategy is also optimized and the amount of CO₂ emission reduction on a typical day is increased by 11.06%. This work shows a way to combine fossil fuels and renewable energy for low carbon emissions and efficient power generation.

Combined cooling and power (CCP) system driven by low-grade heat is promising for improving energy efficiency. This work proposes a CCP system that integrates a regenerative organic Rankine cycle (RORC) and an absorption chiller on both driving and cooling fluid sides. The system is modeled by using the heat current method to fully consider nonlinear heat transfer and heat-work conversion constraints and resolve its behavior accurately. The off-design system simulation is performed next, showing that the fluid inlet temperatures and flow rates of cooling water as well as RORC working fluid strongly affect system performance. The off-design operation even becomes infeasible when parameters deviate from nominal values largely due to limited heat transfer capability of components, highlighting the importance of considering heat transfer constraints via heat current method. Design optimization aiming to minimize the total thermal conductance is also conducted. RORC efficiency increases by 7.9% and decreases by 12.4% after optimization, with the hot fluid inlet temperature increase from 373.15 to 403.15 K and mass flow rate ranges from 10 to 30 kg/s, emphasizing the necessity of balancing system cost and performance.

A two temperature CO₂ refrigeration system with economizer is proposed and compared with the traditional dual-temperature CO₂ refrigeration system based on energy consumption, exergy and economic analysis. Using genetic algorithm multi-objective optimization method, taking the COP, exergy loss and total economic cost as the objective functions to find the best design conditions of the two systems. The Pareto fronts are obtained at different ambient temperatures. Technique for order preference by similarity to an ideal solution decision-making method is adopted to determine the optimum state points. The simulation results show that when operating at different ambient temperatures, the introduction of economizer can improve COP, reduce exergy loss and the overall economic cost rate of the two-temperature CO₂ refrigeration system. In addition, economic analyses take the impact of carbon dioxide emission cost and electricity price into consideration. The results indicate that with the increase of CO₂ emission cost and electricity price, the hourly economic cost of both systems increases, but the hourly economic cost of the two-temperature CO₂ refrigeration system with economizer system is always lower than that of conventional two-temperature CO₂ refrigeration system.

The standing-wave thermoacoustic engines (TAE) are applied in practice to convert thermal power into acoustic one to generate electricity or to drive cooling devices. Although there is a number of existing numerical researches that provides a design tool for predicting standing-wave TAE performances, few existing works that compare TAE driven by cryogenic liquids and waste heat, and optimize its performance by varying the stack plate spacing. This present work is primarily concerned with the numerical investigation of the performance of TAEs driven by cryogenic liquids and waste heat. For this, three-dimensional (3-D) standing-wave TAE models are developed. Mesh- and time-independence studies are conducted first. Model validations are then performed by comparing with the numerical results available in the literature. The validated model is then applied to simulate the standing-wave TAEs driven by the cryogenic liquids and the waste heat, as the temperature gradient ΔT is varied. It is found that limit cycle oscillations in both systems are successfully generated and the oscillations amplitude is increased with increased ΔT. Nonlinearity is identified with acoustic streaming and the flow reversal occurring through the stack. Comparison studied are then conducted between the cryogenic liquid-driven TAE and that driven by waste heat in the presence of the same temperature gradient ΔT. It is shown that the limit cycle frequency of the cryogenic liquid system is 4.72% smaller and the critical temperature ΔT_cri =131 K is lower than that of the waste heat system (ΔT_cri=187 K). Furthermore, the acoustic power is increased by 31% and the energy conversion efficiency is found to increase by 0.42%. Finally, optimization studies on the stack plate spacing are conducted in TAE system driven by cryogenic liquids. It is found that the limit cycle oscillation frequency is increased with the decreased ratio between the stack plate spacing and the heat penetration depth. When the ratio is set to between 2 and 3, the overall performance of the cryogenic liquid-driven TAE has been greatly improved. In summary, the present model can be used as a design tool to evaluate standing-wave TAE performances with detailed thermodynamics and acoustics characteristics. The present findings provide useful guidance for the design and optimization of high-efficiency standing-wave TAE for recovering low-temperature fluids or heat sources.

As a new generation fuel cell, solid oxide fuel cell (SOFC) has become a hot spot in the industry due to its unique advantages. In order to improve energy utilization and prevent carbon deposition in the reformer, the ejector is usually used to recover the cell anode exhaust. In this paper, the applications related to ejector in SOFC are reviewed, including the ejector design and optimization methods, the ejector performance verification experiment and the performance of ejector in SOFC systems. Besides, in order to adapt to the wide power output characteristics of the stack, a study on extending the working range of the ejector is also introduced. On the one hand, the theory of optimal design of ejector used in SOFC system is obtained, including the influence of main structure parameters of ejector on the performance of the whole system and the theoretical model of performance monitoring of ejector used in SOFC. On the other hand, it is proved that the ejector used in SOFC power system can prevent the occurrence of carbon deposition problems, while the recovery of exhaust heat can improve the energy utilization of the system. Finally, suggestions for future related research work are given, aiming to promote the ejector-based SOFC system to provide higher and more stable performance in the future.

The basic organic Rankine cycle (BORC) and ORC with an internal heat exchanger (IHORC) are studied with different working fluids under a given heat source condition to analyse the thermodynamic performances and net power output. The results demonstrate that the external exergy efficiency of IHORC is lower than that of BORC while the internal exergy efficiency is on the opposite with the same overall exergy efficiencies. A multi-objective optimization model with inlet pressure and temperature of expander as independent parameters and exergy and heat recovery efficiencies as objective functions is solved by NSGA-II (the second non-dominated sorting genetic algorithm). The Pareto optimal solutions are obtained by the optimization models. By calculation with the optimum conditions, it is determined that R236ea has the best comprehensive performance with exergy efficiencies being 40.69% and 41.38%, and heat recovery efficiencies being 83.2% and 75.6% in IHORC and BORC, respectively. The evaporators occupy the maximum exergy destruction, which can be reduced by decreasing pinch point temperatures and increasing evaporation pressures.

An adsorption refrigeration system can be driven by low grade heat and uses natural refrigerant with the advantage of reducing the greenhouse gases emission. However, one of the weaknesses is its low efficiency and more importantly its high cost. The recovery of internal waste heat becomes therefore very important in order to improve the coefficient of performance (COP). Analysis based on pinch technology can be helpful to optimal heat recovery operation. In this paper, temperature-heat diagrams and problem tables for adsorption refrigeration systems are proposed and analyzed using Pinch Technology. The results show that pinch point is located between beds and the main waste heat needs to be recovered between beds. Dynamic characteristic (time factor) of adsorption refrigeration system is the main resistance for heat recovery. The effect of pinch point temperature difference on the system COP is not distinct. Furthermore, when the driving temperature is 90°C, the COP of adsorption refrigeration via optimization of pinch analysis is 0.73 which is fairly comparable to LiBr-water absorption refrigeration system. Pinch Technology can be adopted in different types of adsorption refrigeration systems (two-bed, four-bed, mass recovery, et al.).

This paper aims to find a more general analysis method for the refrigeration performance, and to design a high efficiency modular cooling structure of water-cooled plate. A new analysis method, namely current and refrigeration rate density analysis, is proposed. The general refrigeration performance calculation equations are obtained. A finite-time thermodynamic model of the thermoelectric device is established considering Thomson effect. The basic structure of water-cooled thermoelectric air-conditioner is designed and the specific calculation method is given. The influences of input current density, filling factor and heat transfer conditions on refrigeration performance of the thermoelectric air-conditioner are analyzed, which is compared with refrigeration performance of air-cooled thermoelectric air-conditioner. The results show that the maximum refrigeration rate density of the water-cooled thermoelectric air-conditioner is 8.65 kW/m², and the maximum coefficient of performance (COP) is 2.27 in the case of the cooling temperature difference ΔT=5 K. Compared with ΔT=5 K, the maximum refrigeration rate density and the maximum COP of ΔT=15 K decreases by 27.98% and 76.65%, respectively. At the filling factor θ=0.43, the refrigeration rate density and COP are 2.57 kW/m² and 1.24, respectively. The experimental device of thermoelectric air-conditioner is established to verify the model. The experimental results show that the maximum value of input current and COP is 4 A and 0.95 with the efficient water-cooling method, respectively. The experimental data coincides with the theoretical calculation, which shows the validity of the analysis method and cooling method.

The vapor compression heat pump is considered as the best option for aerospace thermal control system. The heat exchanger in vapor compression heat pump is a component that is greatly influenced by the cosmic environment. Lubricating oil enters heat pump system with a refrigerant under microgravity, and the entrance of the lubricant increases the complexity of the flow. In this work, FLUENT software was used to study the flow and lubricant deposition of a two-phase mixture of lubricant POE RL 68H and refrigerant R134a in a heat exchanger without the consideration of phase-change heat transfer. The functional relationships between the oil film thickness and the proportion of lubricating oil, the gravitational acceleration, the inlet flow velocity, and the placement directions of the two phases of oil in the heat exchanger were established. The results demonstrate that with the increase of the gravitational acceleration and the lubricating oil content, the thickness of the oil film will exhibit an S-type change in line with the Boltzmann function, and the amount of lubricating oil deposition will increase. With the increase of the flow velocity, the thickness of the oil film will exhibit an exponential decline.

In the present study, the thermodynamic and economic performance of a combined thermodynamic cycle formed by an ORC and a Kalina cycle, which can simultaneously recover waste heat of exhaust gas and cooling water of marine engine, has been analyzed. Two typical marine engines are selected to be the waste heat source. Six economic indicators are used to analyze the economic performance of this combined thermodynamic cycle system with different marine engine load and under practical comprehensive operating condition of marine engine. The results of the present study show that the combined thermodynamic cycle system with R123 as organic working fluid has the best performance. The system with cis-butene has the worst economic performance. Under practical comprehensive operating conditions of ships, R123 has the shortest Payback Periods, which are 8.51 years and 8.14 years for 8S70ME-C10.5 engine and 5G95ME-C10.5 engine, respectively. Correspondingly, payback Periods of Cyclopentane are 11.95 years and 11.90 years. The above values are much shorter than 25 years which are the lifetime of a marine ship. Under practical comprehensive operating conditions of ships, the combined cycle system can provide output power which is at least equivalent to 25% of engine power. Considering that R123 will be phased out in near future, cyclopentane may be its good successor. Cyclopentane can be used safely by correct handling and installing according to manufacturer's instructions.

In order to provide more grid space for the renewable energy power, the traditional coal-fired power unit should be operated flexibility, especially achieved the deep peak shaving capacity. In this paper, a new scheme using the reheat steam extraction is proposed to further reduce the load far below 50% rated power. Two flexible operation modes of increasing power output mode and reducing fuel mode are proposed in heat discharging process. A 600 MW coal-fired power unit with 50% rated power is chosen as the research model. The results show that the power output is decreased from 300.03 MW to 210.07 MW when the extracted reheat steam flow rate is 270.70 t·h−1, which increases the deep peak shaving capacity by 15% rated power. The deep peak shaving time and the thermal efficiency are 7.63 h·d−1 and 36.91% respectively for the increasing power output mode, and they are 7.24 h·d−1 and 36.58% respectively for the reducing fuel mode. The increasing power output mode has the advantages of higher deep peak shaving time and the thermal efficiency, which is recommended as the preferred scheme for the flexible operation of the coal-fired power unit.

The organic Rankine cycle is introduced into the conventional ejector refrigeration (CER) system to establish the low-grade heat-driven cooling/power cogeneration ejector refrigeration (CPC-ER) system using the isobutane as the refrigerant. In comparison with the CER system where external power is consumed by the circulating pump, the power output from the CPC-ER system is more than the power consumption of its circulating pump so that a portion of net power is derived from the CPC-ER system. Based on the mathematical model of thermodynamics, energy and exergy analysis of the CPC-ER system is carried out and compared with the CER system. The results reveal that the equivalent coefficient of performance (COP) of the CPC-ER system is 41.14% to 71.30% higher than that of the CER system, and the exergy efficiency of the CPC-ER system is 1.32 to 1.49 times higher than that of the CER system. Both the power produced by the turbine and the total exergy output from the CPC-ER system approach the maximum, as the generating temperature in the generator is up to 80°C. The CPC-ER system has the higher energy utilization efficiency than the CER system, and it is suitable for the cooling and power-required places with low-grade thermal sources.

The objective of this paper is to understand the benefits that one can achieve for large-scale supercritical CO₂ (S-CO₂) coal-fired power plants. The aspects of energy environment and economy of 1000 MW S-CO₂ coal-fired power generation system and 1000 MW ultra-supercritical (USC) water-steam Rankine cycle coal-fired power generation system are analyzed and compared at the similar main vapor parameters, by adopting the neural network genetic algorithm and life cycle assessment (LCA) methodology. Multi-objective optimization of the 1000 MW S-CO₂ coal-fired power generation system is further carried out. The power generation efficiency, environmental impact load, and investment recovery period are adopted as the objective functions. The main vapor parameters of temperature and pressure are set as the decision variables. The results are concluded as follows. First, the total energy consumption of the S-CO₂ coal-fired power generation system is 10.48 MJ/kWh and the energy payback ratio is 34.37%. The performance is superior to the USC coal-fired power generation system. Second, the resource depletion index of the S-CO₂ coal-fired power generation system is 4.38 μPR_china,90, which is lower than that of the USC coal-fired power generation system, and the resource consumption is less. Third, the environmental impact load of the S-CO₂ coal-fired power generation system is 0.742 mPE_china,90, which is less than that of the USC coal-fired power generation system, 0.783 mPE_china,90. Among all environmental impact types, human toxicity potential HTP and global warming potential GWP account for the most environmental impact. Finally, the investment cost of the S-CO₂ coal-fired power generation system is generally less than that of the USC coal-fired power generation system because the cost of the S-CO₂ turbine is only half of the cost of the steam turbine. The optimal turbine inlet temperature T₅ becomes smaller, and the optimal turbine inlet pressure is unchanged at 622.082°C/30 MPa.