It is a common problem that the direct air-cooled unit cannot be fully charged during the high temperature period in summer, and the widely used solution is to install a sprinkler device in the air-cooled unit for humidification and cooling. Through analysis on the air flow field in the cooling unit, it is found that the air flow field in the silo is non-uniform due to the influence of fans and bridges. The method of non-uniform arrangement of nozzles in the air flow field is used to evenly mix the air and spray water, and the high-pressure spray is used to achieve a uniform temperature drop in the overall air field to minimize the temperature of the cooling air. This method effectively solves the problem of cooling and improves the efficiency of air-cooled units in summer, and is of great significance for peak operation of thermal power units in summer.

In order to realize cascade utilization of energy in the heating system, in view of the problem that the heat load of industrial users does not completely match the heat consumption for activated carbon regeneration, the steam-air heater has been installed in flue gas desulpherization and denitration demonstration unit for No.2 coal-fired generation unit in a thermal power plant. Steam becomes primary heat source to realize activated carbon regeneration. Steam extracted from the turbine heats circulating hot air in the FGD unit firstly, then supplies remaining heat energy to different terminals outside the plant after desuperheating. Hereby this article thoroughly describes how to select control valve in steam supply system, so as to realize coupling control of heat energy between two different users. The rationality of this design has been verified during actual operation of the demonstration project, and it provides a reference for the selection of control valves in future engineering practices.

Peak regulation in thermal power plants is an inevitable trend under the development of new energy. Under this condition, the initial condensing zone of steam turbine moves forward and the corrosion of low pressure cylinder intensifies. Several methods such as electrochemical testing, sample weight loss and metal surface topography analysis (SEM, EDS, XRD, and so on) were used to study the pitting corrosion characteristics of 2Cr13 steel (the material of low pressure cylinder of the steam turbine) under the conditions of simulated initial setting zone, with different mass concentrations and different mass concentration ratios of Cl^– to SO₄^2– of three anions (Cl^–, SO₄^2– and CH₃COO^–). The test results showed that, the corrosion rate of 2Cr13 steel increased with the anions’ mass concentration, and the maximum corrosion rate (0.095 23 g/(m²·h)) occurred when was 2:1. Pitting corrosion was observed in all samples, and the number of pitting corrosion increased with the anions’ mass concentration. With the change of, Cl^– and SO₄^2– on the metal surface of 2Cr13 steel changed from site competitive adsorption effect to mutual synergistic effect, resulting in the intensification of uniform corrosion and pitting corrosion. The chloride ions and sulfate in the initial coagulation zone of steam turbine will accelerate the corrosion rate of 2Cr13 steel and the occurrence of point corrosion. In actual operation of power plant, measures should be taken to prevent the leakage of condenser tubes and the broken particles of positive resin should be effectively removed.

In order to study the effects of different drying conditions on crushing rate and pulverization rate of Baoqing lignite after drying, as well as the effects of different drying moistures on spontaneous combustion and explosion characteristics of the coal samples, several experiments were conducted, like the drying of raw coal, and the spontaneous combustion and explosion characteristics of coal samples with different moisture contents. The results show that, a drying furnace temperature above 300 ℃ and a higher heating terminal temperature can achieve a higher coal sample dehydration rate. Coal particles with smaller particle sizes tend to achieve higher dehydration rates and lower crushing rates. The pulverization rate of 6~13 mm coal particles is the highest under different drying conditions. Baoqing raw coal is a type of coal that is prone to spontaneous combustion. As the moisture content of the dried coal sample decreases, the spontaneous combustion tendency of the raw coal weakens and becomes a type of coal with moderate spontaneous combustion tendency. As the moisture content of the coal sample increases, the explosion tendency of the test coal sample decreases. As the fineness of coal powder R90 increases, the explosion tendency of coal powder decreases. Therefore, in the engineering application process of Baoqing lignite drying technology, the proportion of 6~13 mm coal particles should be reduced to lower the pulverization rate during the drying process. The air temperature during coal powder transportation should be appropriately reduced, or the fineness of coal powder should be appropriately increased to reduce the tendency for explosion.

In order to solve the corrosion problem of direct air cooling condensers, the independently developed dynamic corrosion simulation test device is used to simulate the actual operating conditions of the initial condensate, and the alkalizing agent and oxidant with low vapor-liquid distribution coefficient are selected for the flow accelerated corrosion test of carbon steel. The results show that, both alkalizing agent and oxidant can effectively inhibit the accelerated corrosion of direct air-cooled condenser. The rapid change of water flow direction has little effect on the accelerated corrosion rate of flow. Under the same conditions, the flow accelerated corrosion rate of carbon steel in oxidant environment is much lower than that in alkalizer environment. When oxidant is added to the direct air-cooled condenser for anticorrosion, the production cost of a single unit can be saved by 523 700 yuan per year.

Grid-forming energy storage system is expected to solve the problems like insufficient frequency modulation resources and disturbance resistance decline of large-scale new energy-based power grid. However, its active support ability is greatly limited due to its inherent power coupling characteristics, plus power overshoot, oscillation and even instability problems are most likely to occur with parameter variation. To solve this problem, a full-order small signal model for grid-forming energy storage system is developed, its frequency response characteristics are analyzed according to the output power state space model and its characteristic roots. On this basis, by analyzing the sensitivity and participation factors of the state space matrix parameters, the stable boundary of the grid-forming energy storage converter is given, and the influence of key parameters of the grid-forming energy storage converter on its dynamic power coupling, frequency support and other grid related characteristics is clarified. The simulation and semi physical experimental results have verified the correctness and feasibility of the theoretical analysis, providing a basis for the design of grid connected parameters and stable operation of grid-forming energy storage converters.

Solid oxide fuel cell (SOFC) is a promising energy conversion device. It has the advantages of non-pollution, high energy utilization rate, and good fuel adaptability. However, SOFC often needs to be operated under variable load conditions, which leads to the problems of shorten service life and performance degradation. The study of the relationship between the variable load characteristics of SOFC and its operating conditions is helpful to improve the output performance of the stack, extend its service life, and formulate a reasonable control strategy. A 100 W SOFC short stack testing system was developed to experimentally investigate the variable load characteristics of the SOFC stack under multiple operating conditions. The results show that, increasing the operating temperature can reduce the ohmic resistance and total polarization resistance of the fuel cell stack, thereby enhancing the stack’s steady-state output performance and dynamic response performance. Increasing the hydrogen flow rate in the medium to high current range can reduce the concentration polarization resistance, thereby effectively enhancing the stack’s peak output performance and dynamic response performance. Increasing the air flow rate has a smaller effect on the performance improvement of the stack. Under the constant flow utilization strategy, the response voltage immediately falls within the range of ±5% of the final voltage. By varying the load with constant voltage, the response current can smoothly reach a stable value. Compared with the constant flow strategy and constant current load variation method, the stack shows better dynamic response performance under the constant flow utilization strategy and constant voltage load variation method.

Aiming at the problem of wind turbine off-grid due to lack of high voltage ride through (HVRT) capability of wind power, the internal mechanism of wind turbine off-grid due to voltage increase of junction point caused by DC fault is elaborated. The dynamic reactive power response characteristics of energy storage system and static var generator (SVG) during HVRT are analyzed. Through real-time monitoring of the voltage of the junction point, the priority of the control strategy during HVRT crossing is divided into reactive power regulation inside the wind farm (cooperative control of energy storage system and doubly fed induction generator (DFIG)) and SVG reactive power regulation. On this basis, a collaborative control strategy of energy storage system, DFIG and SVG is proposed to improve the HVRT capability of wind farms. At the same time, the voltage reference value for adverse situations after fault removal is reset to avoid unnecessary reactive power flow. Finally, a simulation model is built based on MATLAB/Simulink platform to verify the correctness and effectiveness of the theoretical analysis and control strategy. The research results provide new ideas for fully exploring the reactive power regulation capability of wind farms and greatly reducing the burden of SVG reactive power compensation.

The development of efficient energy storage technologies is critical as global energy demand rises and environmental issues become increasingly serious. Large eddy simulation is employed to model the phase change heat storage process in a packed bed system consisting of a double-layer cascade capsule-stacked structure based on the pore scale. The temperature, streamlines, and vortex distributions of phase change materials (PCMs) with various melting points and physical properties are investigated within the structure. The thermal characteristics of the capsule-type stacked structure are analyzed at different entrance velocities, and the simulation results are validated by experimental data. The simulation results demonstrate that, the interstitial flow and vorticity fields of the stacked structure exhibit significant dynamic characteristics during heat storage. At the pore scale, the phase transition induces streamline bending, vortex formation, and the increase of local velocity. After the phase transition, the flow field and vorticity tends to stabilize, with low-vorticity regions occupying most of the area. Eventually, the vortex structure is analyzed by the Q-criterion, revealing that the high-intensity vortices are primarily concentrated near the tank wall.

To address the electricity consumption challenges in remote regions beyond the reach of power grid, a novel off-grid microgrid system integrating wind and solar energy with flywheel storage technology is introduced. Research is conducted on the optimal capacity configuration of distributed power sources, and power output models are developed for wind turbines, photovoltaic arrays, energy storage flywheels, and diesel generators. With economic and reliability indicators as objective functions, and environmental protection indicators as constraints, a capacity optimization simulation for the microgrid system is conducted. By employing the improved NSGA-II algorithm, a multi-objective bi-level coordinated optimization of the microgrid system is performed, resulting in a Pareto optimal solution through multi-objective optimization. The TOPSIS method is utilized for decision-making, ultimately identifying the optimal solution tailored for the microgrid system. The data and conclusions obtained from this study have reference value for engineering applications in related fields.