To enhance the peak shaving performance of heating units, a new process for double-reheat heating unit integrating five thermo-electric decoupling technologies, namely cylinder cut-off, high-/medium- and low-pressure bypass heating, heat pump, hot water tank and electric boiler, has been proposed. A detailed thermodynamic model of the system was established, and the peak shaving performance of the novel power plant is compared with that of a reference power plant. Relying on the electricity market, a systematic economic operation strategy was put forward, and a techno-economic analysis was performed. The results show that, when the heating demand is 1 460 MW, the reference plant cannot meet the heating demand under the extraction-condensing condition. Under the cylinder cut-off condition, the load regulation range of the reference plant is 77.9% to 80.0% of the rated load, and it almost loses its load regulation ability. While under the cylinder cut-off + bypass condition, the load regulation range of the reference unit is 50.0%~80.0%, and its peak regulation ability has been improved. For the novel plant, in the same heating demand, the load regulation range has been expanded to 0~80.0%, and zero-power grid connection can be achieved especially during the low electricity demand period. Compared with the reference plant, the novel plant can reduce the power output during peak shaving periods by 107 600 MW·h per month, save 17 700 tons of coal, achieve an annual net profit increase of approximately 68.988 million yuan during the heating season, and have a payback period for new equipment investment of 5.6 years, demonstrating significant economic benefits.

As the core of thermal power units, the operation efficiency of the direct air cooling system is significantly restricted by the geographical location of the power plant and the surrounding environmental parameters. Taking the direct air cooling system of a power plant as the prototype, a three-dimensional numerical model of the air cooling system and the surrounding buildings and mountain environment is established, and the composite wind prevention measures for the windward side of the air cooling island or the units with unfavorable heat transfer are proposed. The windproof measures and optimization mechanism of the direct air cooling system with strong applicability and good effect are explored, and the influence of air flow field reconstruction inside and outside the air cooling unit on the cooling performance of the direct air cooling system is analyzed. The results show that the internal and external wind-proof measures of the direct air-cooled unit can effectively improve the thermal performance of the unit. When the wind speed is 5 m/s, the large cross wall windshield has a good effect on improving the heat transfer performance of the air-cooled island. The frontal wind speed of the radiator increases by 0.24 m/s, and the surface temperature of the radiator reduces by 2.40 ℃. After the reconstruction of the air flow field inside and outside the air cooling unit, the average surface temperature of the radiator in the direct air cooling system reduces by 5.77 ℃, and the back pressure reduces by 2.92 kPa. The reconstruction of the air flow field inside and outside the air cooling unit can significantly improve the cooling effect of the direct air cooling system and improve the operating performance of the cold end system of the power station. In the future, the optimization design of the diversion device of the direct air cooling system can focus on the improvement of the uniformity of the flow field.

As a core control parameter in peak regulation via banking fire, the banking fire duration directly affects the safety and economic efficiency of unit operation. However, due to the complex coupling and dynamic characteristics of thermodynamic parameters during the banking process, it is difficult for existing calculation methods to achieve efficient and accurate calculations. An energy-balance-based method was proposed for banking fire duration calculation in subcritical CFB boilers. A dynamic equilibrium model was established for heat storage and turbine heat utilization and heat dissipation during banking fire, deriving heat storage and release formulas for key heat sources, such as bed material, refractory, metal heating surfaces, working fluid, and carbon combustion. Finally, the banking fire duration was obtained. Taking a 300 MW sub-critical CFB unit as an example, the absolute error between the calculated value and the measured value is controlled within 5 minutes, and the relative error is less than 10%, which can meet the engineering requirements of fire-hold peak-shaving. The results demonstrate that, in terms of heat storage, the heat storage of metal heating surfaces contributes 35%~41% to the banking fire duration. The contributions of bed material and refractory are each approximately 20%, and the contribution of carbon combustion in the bed material is 10%~15%. The contributions of gas and working fluid heat storage are less than 2% and can be neglected. In terms of heat consumption, heat consumption for power generation accounts for the highest proportion, and it increases with the electrical load. The heat required for the steam turbine to overcome its own rotational resistance accounts for approximately 20%, and the proportion of heat dissipation of the unit is less than 5%. By raising the initial temperature of banking fire, increasing the amount of bed material, using coal with high volatile content, and reducing the electrical load of the unit during banking, the banking fire duration can be significantly prolonged. Notably, the banking fire duration exceeds 2 hours only when the average electrical load during banking is reduced to 1% of rated load.

The coordinated operation of coal-fired power plant (CFPP) with large-scale energy storage systems can effectively regulate the flexibility of power system and smooth the renewable power output. A gas-liquid interconversion carbon dioxide energy storage system coupled with a CFPP was proposed, which recovers compression heat using condensate and feedwater of CFPP and preheats turbine inlet CO2 through drain water, realizing thermal decoupling of charge and discharge processes without heat storage devices. Based on the mathematical models of the coupling system, the system coupling schemes were designed and optimized, and a comparative performance analysis with stand-alone system was conducted. The results show that, the compression heat cascade recovery boosts the exergy efficiency of last-stage intercooler from 73.3% to 89.6%, and the exergy efficiency of the first-stage preheater improves from 53.1% to 89.7% by replacing extraction preheating with drain water cascade preheating. In the optimal coupling scheme, the system energy storage efficiency improves from 63.6% to 76.8% compared to the stand-alone system, and the levelized cost of electricity reduces from 0.130 dollar/(kW·h) to 0.093 dollar/(kW·h), with a slight reduction in round-trip efficiency to 63.2%. The turbomachinery and heat exchangers, representing the main contributors to the total system exergy destruction and investment cost, are key components in improving thermodynamic and economic performance. Increasing the discharge power to 90 MW reduces the levelized cost of electricity to 0.089 dollar/(kW·h) and expands the peak regulating range to 86.4%~107.6%.

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.

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.

Thermochemical thermal storage has attracted wide attentions because it has high thermal density heat storage and can realize seasonal thermal storage and long-distance transportation. The CaCO₃/CaO reaction system, as one of the most promising thermochemical heat storage materials, has problems such as particle aggregation and sintering as the number of heat storage cycles increases, and the material gradually loses its activity. To solve this problem, composite CaO materials doped with Al₂O₃ or CeO₂ were synthesized by the template method. The microstructure of the materials and the effect of chemical doping on the cyclic stability of the composite CaO materials were investigated by means of characterization tests such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and synchronous thermal analyzer (STA). The effect of chemical doping on exothermic reaction temperature range of the composite CaO materials was analyzed. The results show that, the CaO prepared by the template method has a richer pore structure and a superior cycling stability than the CaO obtained by decomposition of CaCO₃. When the doping molar ratio of CaO to Al₂O₃ is 100.0:2.5 (Ca:Al), the composite has the best cycling stability. After 30 cycles, the effective conversion rate decays by only about 7.1% from 0.70 to 0.65 and the exothermic energy density is 2 057 kJ/kg. The cyclic stability of the composite is better than that of CaO when the molar ratio of CaO to CeO₂ doping is 100.0:10.0 (Ca:Ce=100.0:10.0). It is found that doping with Al₂O₃ decreases the onset temperature of the exothermic reaction of the CaCO₃/CaO reaction system, whereas CeO₂ increases the onset temperature.

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.

Induced draft fans in power plants run under complex and harsh conditions, where various faults often occur. These faults not only affect the fans’ safety and stability but also pose an indirect threat to normal operation of the boiler system. Thus, early fault monitoring and prompt, accurate diagnosis are essential to ensure the power plants’ operation efficiency and safety. Common fault types of forced draft fans and their potential effects are analyzed and summarized. Three typical fault types and their causes are explained in detail. Fault monitoring and diagnosis methods are elaborated from both quantitative and qualitative perspectives, including measurement point installation and data processing techniques. Each method’s advantages and disadvantages are analyzed, and suitable applications for different fault types are discussed, along with proposed targeted improvement measures. Finally, key challenges of fault diagnosis are identified, and future development directions for forced draft fans’ fault monitoring and diagnosis are outlined.