A 300 MW supercritical carbon dioxide (S-CO₂) Brayton cycle oxyfuel power generation system is designed, and a simulation model is constructed using process simulation methods to study the effects of key operating parameters (such as the primary dry cycle flue gas ratio, the economizer side split ratio, the cold primary air temperature and the high-pressure turbine inlet pressure) on the system’s thermal performance indexes. The effects of key operating parameters such as primary dry cycle flue gas ratio, economizer side split ratio, cold primary air temperature and high-pressure turbine inlet pressure on the system thermodynamics were investigated, and the thermal characteristics of the generating unit were revealed. The results show that, the boiler efficiency decreases with the increase of the proportion of primary dry-cycle flue gas, and when the proportion of primary dry-cycle flue gas reaches 50%, the net electric efficiency of the system is the highest, which is 42.93%. The boiler efficiency rises at first and then decreases with the increase of the coal economizer-side shunt ratio, and the net electric efficiency of the system reaches the highest (42.86%) when the coal economizer-side shunt ratio is 11%. With the increase of cold primary air temperature, the boiler efficiency keeps increasing, and the rising trend slows down and stabilizes at 99.29% at temperatures higher than 65 ℃, and the net electric efficiency of the system keeps increasing and reaches 43.06% at 95 ℃. With the increase of high-pressure turbine inlet pressure, the boiler efficiency firstly rises and then decreases, and reaches the maximum value of 99.35% at 29.5 MPa, and the net electric efficiency of the system reaches the optimal value (43.66%) at 29.0 MPa.

Data quality is a key factor affecting the application effectiveness of optimization models of denitrification system operation. In response to the problems of lagging and poor representativeness of monitoring parameters in denitrification system operation, a denitrification performance parameter dimension reduction technology suitable for real-time performance monitoring is developed. The utilization rate of reducing agents that can reflect the denitrification ability of the denitrification system itself is set as the monitoring and evaluation parameter for denitrification system operation status, to improve the efficiency of data generation. Based on this, an optimization method for denitrification system operation that can eliminate adjustment delays is established, and an identification technology for typical abnormalities in denitrification system operation is constructed to guide the economic, safe, stable, and standard operation of the denitrification system. This technology has been implemented and applied in a 1 000 MW coal-fired unit at different loads. The results show that, the denitrification system operation guided by the utilization rate of reducing agents reduces the unit consumption of urea solution by 1.5%~8.4% and the ammonia escape at the denitrification system outlet by 10.7%~27.0%, and all of the ammonia escape at different loads meets the general control value of ammonia escape rate. The variation range of NO_x emission mass concentration in the exhaust reduces from 44.5~58.3 mg/m³ to 9.2~10.6 mg/m³, and the distribution deviation significantly decreases from 59.2%~75.2% to 21.4%~25.1%, which is more conducive to the automatic and stable control of the denitrification system.

Supercritical carbon dioxide (S-CO₂) in horizontal tube with circumferential heating and semicircle heating is investigated numerically based on pseudo-boiling theory. The phase distribution of supercritical fluid in the tube is obtained. It is found that the heat transfer performance of supercritical fluid is determined by the thickness of vapor-like film on tube, which can be characterized by supercritical K number, involving the balance between evaporation momentum force and inertia force. The increasing thickness of local vapor-like film can trigger heat transfer deterioration. There are both overshoot wall temperature along the flow direction and non-uniform wall temperature in the circumferential direction. The emerging condition of heat transfer deterioration can be accurately predicted by supercritical boiling number SBO. Under working conditions where the pressure p is 8~20 MPa, and the range of mass flux G and heat flux density q_w is 300~1 300 kg/(m²·s) and 42~500 kW/m² respectively, compared with the circumferential heating tube, the semicircle heating tube behaves thinner vapor-like film to enhance the heat transfer performance. The critical SBO to heat transfer deterioration rises from 6.179×10^–4 to 9.798×10^–4. Furthermore, the semicircle heating tube keeps more uniform vapor-like film, the maximum temperature difference between the top and bottom generatrix of tube wall changes from 116.3 K to 57.1 K. Due to the ability to repress heat transfer deterioration and non-uniform wall temperature, semicircle heating is recommended to ensure the safe operation of horizontal heat exchangers in advanced supercritical CO₂ system.

The current coal-fired unit coupled with molten salt heat storage system technology has the problems of limited peak shifting capacity and poor peak heat economy. To address these issues, a new system of coal-fired unit coupled with compressed steam and molten salt heat storage is proposed, specifically including single molten salt heat storage scheme and double-molten-salt-heat-storage scheme. The system performs multi-stage compression of extracted steam through a multi-stage compressor and uses molten salt for heat storage. The compressed steam is eventually condensed to water so that its latent heat of condensation will be utilized. The simulation model of the coupled system scheme is established by EBSILON software. The research results indicate that, compared with the conventional molten salt heat storage technology scheme, the compressed steam and molten salt heat storage system can effectively reduce the effect of steam extraction and heat storage on the thermal economy of the system, and expand the peaking range of the unit. Specifically, the round-trip efficiencies of the single molten salt and double-molten-salt scheme are improved from 27.43%~38.03% to 62.13%~64.56% and 65.69%~66.93%, respectively, and the minimum outputs are reduced from 20.91%Pe to 19.84%Pe and 19.28%Pe, respectively, compared with the conventional scheme. Considering the thermodynamic and economic performance of the system, the single molten salt scheme is the best choice.

The sterilization effect of chlorine-containing disinfectants does not hinge on the total available chlorine concentration, but rather on the concentration of hypochlorous acid (HClO) molecules. To reduce the cost of circulating water sterilization in thermal power plants, HClO solution was used to sterilize circulating water. The HClO solution was prepared from sodium hypochlorite (NaClO) solution, CO₂ and pure water by non-electrolytic method, and experimental study on application performance (including stability and sterilization effect) of the HClO solution was conducted. The results showed that, the mass concentration of HClO in NaClO solution was extremely low, the mass fraction of HClO to available chlorine was only 0.690%~0.012% in NaClO solution with mass concentration of available chlorine in the range of 100~2 000 mg/L, which could be increased to 94.91% by reacting with CO₂, thereby improving the sterilization efficiency. When 30, 60, 80, and 90 mg/L stabilizer were added, the decomposition rate of HClO solution with mass concentrations of 500, 1 000, 1 500 and 2 000 mg/L could meet the requirements for a shelf life of one year of the Disinfection Technical Specification. When the dosage of NaClO and HClO (calculated by available chlorine) was 5 mg/L and 0.06 mg/L，the sterilizing time was 120 min and 15 min, the sterilizing rate could reach 90%, and it can be seen that HClO was more economical and efficient for sterilization. HClO solution can reduce the cost of circulating water bactericides in thermal power plants by more than 55% compared with that of conventional NaClO.

Due to the significant volatility and randomness of wind power data, low prediction accuracy is often observed with a single model in wind power prediction. To overcome this, an ultra-short-term wind power prediction method is introduced, based on modal decomposition and a combined neural network model. Firstly, the wind power data are processed based on the improved fully integrated empirical modal decomposition and sample entropy, which decomposes the unsteady series into smoother sub-sequences and reconstructs the high-frequency oscillatory component and low-frequency smooth component synchronously. Secondly, a hybrid prediction model for wind power based on an adaptive sparse self-attention mechanism is constructed. For the high-frequency oscillatory component with high complexity, the adaptive sparse Transformer model is used to fully explore the fluctuation information. For the low-frequency stationary components, the sequence features are fully extracted by the bidirectional gated recurrent unit model. Finally, the final prediction outcomes are derived by overlaying the forecast results of each component. Test was performed with actual data from a wind farm in Shandong, and the results show that, compared with other commonly used models, the proposed model’s root mean square error and average absolute error has decreased by 2.644 MW and 2.42 MW, and the coefficient of determination has a notable 18.2% increase, implying it has a good prediction performance.

The heat transfer characteristics and safety of a single tank thermal storage system during charging and discharging cycle are important indicators affecting the performance of the thermal storage tank. By coupling finite volume method and finite element method, a comprehensive model of a multi-layer wall structure molten salt single tank system is established, and the effects of inlet flow velocity and inlet/outlet temperature difference on the dynamic thermal characteristics and mechanical properties of the thermal storage tank during continuous charging and discharging cycling process are explored. The results indicate that, increasing the inlet flow rate will reduce the heat storage and improve the thermal efficiency, but will also increase the equivalent stress on the tank wall. Increasing the temperature difference between the inlet and outlet will increase the heat storage and reduce the thermal efficiency, and also increase the equivalent stress on the tank wall. To ensure the heat storage and thermal efficiency of the single tank heat storage system, as well as the safety of the system, for the single tank system with a heat storage capacity of 40 MW·h, the inlet flow rate of molten salt should be controlled within 0.002 60~0.003 46 m/s, and the temperature difference between the inlet and outlet of molten salt needs to be controlled within 200~250 K.

Thermal power units, as a cornerstone of conventional electricity generation, release considerable quantities of waste heat during their operation. If not effectively harnessed, this waste heat will result in substantial energy inefficiency and exacerbate environmental challenges. Consequently, the efficient recovery and utilization of waste heat from thermal power units represents a pivotal strategy for optimizing energy use and mitigating carbon emissions. The energy-saving and carbon-reduction potential of various cycle components in thermal power units should be thoroughly explored. Conducting parameter matching to enable the efficient and comprehensive utilization of waste heat at different grades in thermal power units holds significant importance for achieving deep energy conservation and emission reductions in China’s thermal power industry. A comprehensive examination of waste heat recovery in thermal power units is provided. It begins by identifying the primary sources and distinctive characteristics of waste heat. Subsequently, it delves into specific recovery methodologies and their technical principles, encompassing low-pressure turbine exhaust heat utilization, flue gas heat recovery, boiler blowdown and continuous blowdown heat recovery. For each method, the system configuration, current deployment status, economic feasibility, and environmental benefits are analyzed in detail. The strengths and limitations of these approaches are critically evaluated. Finally, the future prospects and developmental trajectories of waste heat recovery technologies in the thermal power sector are thoroughly explored and anticipated.

Molten salt energy storage technology is widely used in solar thermal power generation due to its high thermal capacity and good thermal stability. To optimize the influence of key operating parameters on energy storage efficiency, numerical simulation methods are used to analyze the mechanism of input velocity, initial temperature, temperature difference and other parameters on the formation of thermocline and heat storage efficiency at different horizontal positions. The results show that, increasing the temperature difference and the input speed can significantly promote the development of the thermocline, and increase the heat storage efficiency by more than 10%. The parameter optimization algorithm based on response surface methodology identifies an optimized parameter combination, which improves the heat storage efficiency by a maximum of 16.3 percentage points compared to the previous simulations. At the same time, to quickly and accurately predict the operating temperature of the system, three machine learning models are compared, and it finds out that the random forest model has the best prediction with an accuracy rate of 98.78%. The research results provide theoretical basis and application reference for the optimization design of molten salt energy storage systems.

With the rapid development of energy storage industry and the continuous increase in the installed capacity of energy storage power stations, safety accidents in electrochemical energy-storage power stations have become increasingly frequent, and safety issues have gradually become a key factor restricting the large-scale development of the industry. Therefore, the current policies and standards related to safety risk assessment of electrochemical energy storage power stations at home and abroad are systematically reviewed at first. Then, by analyzing typical safety incidents of electrochemical energy storage power stations, the safety risk points of such power stations are summarized. Based on this, the research progress of the theory and evaluation methods of safety risk assessment of electrochemical energy storage power stations is summarized, from the aspects of battery body, power station working environment, external stimulation and human factors. Finally, the safety development of energy storage power stations in the future is discussed from improving the safety evaluation policies and standards of energy storage power stations, enhancing the construction of the safety assessment system for energy storage power stations, improving the safety and operation management system of energy storage power stations, and strengthening the cultivation of professionals in the energy storage field. It is hoped that this will provide some references for subsequent related researches.