Energy storage system assisted thermal power unit frequency regulation is limited by the capacity of storage device, and its output power can not track the command power for a long time. At the same time, lithium battery energy storage technology also exists problems in safety hazards, cycle life limitations, limited enhancement of unit frequency gain gain and other issues. For this reason, the characteristics of high cycle life and high safety of supercapacitor are used to construct the simulation model of hybrid energy storage system assisted coal-fired thermal power unit frequency regulation in Matlab/Simulink platform. Combining with the operating state of thermal power unit and energy storage system, a set of control strategy based on index calculation and fuzzy control synergy is designed to achieve the adaptive adjustment of hybrid energy storage system output under dynamic operating conditions. Simulations show that, the control strategy can effectively extend the service life of lithium batteries and efficiently utilize the residual power of the hybrid energy storage system. Compared with the conventional control strategy of hybrid energy storage system, the proposed control strategy reduces the average daily use time of lithium battery by 60%, improves the comprehensive index of frequency regulation performance by 34%, and increases the average daily revenue by 20 000 yuan, which has high engineering application value.

To accommodate grid-connected large-scale renewable power, coal-fired power plants need to undertake more peak shaving and frequency regulation tasks, so it will engage in the processes of deep peak shaving and load cycling for a long time. In this situation, the performance of wet flue gas desulfurization system (WFGD) will degradation and the auxiliary power consumption will increase significantly. To solve this problem, the dynamic model of an ultra-supercritical 660 MW coal-fired power unit and the dynamic model of the WFGD system based on the double-membrane theory are established. The performance of the desulfurization system is simulated when the slurry circulation pumps are switched under different operating conditions during the load cycling processes. It is found that the precise matching of slurry and flue gas during load cycling processes can achieve the minimum power consumption of the desulfurization system while meeting the SO₂ emission standard. Furthermore, when the slurry circulation flowrate changes stepwise during load cycling processes, the prediction model of changes in SO₂ mass concentration at the WFGD system outlet is obtained. An optimization control strategy for the slurry circulation pumps in fixed-frequency mode is proposed, which can achieve the best match between the slurry and flue gas during load cycling processes. Finally, the energy saving potential for the proposed control strategy is analyzed. When the load cycling rates are 1.0%, 1.5% and 2.0% Pe/min, the energy saving potential is 20.12%, 21.52% and 22.82% during loading down processes from 75% THA to 50% THA conditions, and that value will be 10.04%, 9.90% and 8.66% during loading up processes, respectively. The difference in flue gas flowrate during load cycling processes is found as a key factor causing the disparate of energy saving potential during loading down and loading up processes.

Flow batteries are considered as one of the most promising technologies for large-scale energy storage, due to their inherent safety, long cycle life, environmental friendliness and robust scalability. As the key material of flow batteries, electrodes have a significant influence on battery performance. The research advancements of electrospun carbon nano-fiber electrodes in flow batteries are reviewed. The fabrication principles of electrospun carbon nano-fibers and their influence on the critical fabrication parameters are elucidated. It provides a comprehensive review of preparation methods for electrospun carbon nano-fiber electrodes with controllable structure and chemistry, properties and their effect on battery performance, including microstructural modulation of carbon nano-fibers, heteroatom doping, and catalytic modification. The key of electrode optimization is synergies between electrochemical activity and mass transport of electrodes, which are associated with the active areas and chemistry properties. The microstructure and surface properties of fibers can be controlled by strategies involving fiber porosity or new structural designs. Doping heteroatoms and introducing catalysts can increase the active area and hydrophilicity of the electrodes to promote the electrochemical activity of the electrodes. Lastly, the challenges and future developments of the electrospun carbon nano-fiber electrodes from laboratory preparation to scaling-up are outlined.

Under deep peak shaving and variable operating conditions of thermal power units, significant changes in steam temperature have caused a significant increase in thermal stress in some structures of the units, which accelerated structural damage, and resulted in frequent safety accidents. To solve these problems, by taking the regulating stage rotor of a 300 MW steam turbine as the object, and Ansys software is used to analyze the thermal stress, aerodynamic force, and centrifugal force of the blades. Firstly, structural optimization is carried out on root of the blade to significantly eliminate the unreasonable local stress concentration phenomenon commonly found in conventional calculations. Then, the distribution laws of temperature and stress fields in the regulating stage under different conditions such as steady-state and transient during the deep peak shaving process of thermal power units are revealed. Moreover, the effects of the temperature and stress fields on safety performance of the unit are also investigated. The results indicate that, the maximum equivalent stress increases by about 24% under steady-state conditions with temperature difference of different nozzle groups of 50 ℃. The transient load increase rate of 5% THA/min is about three times higher than that of 2% THA/min, causing low cycle fatigue damage to the rotor. Compared with steady-state operating conditions, increasing the load once a day at a rate of 2% THA/min from half load to full load increases the overall damage by about 38%.

For the integrated energy system composed of photovoltaic power generation, energy storage battery storage and discharge, and coal-fired heating boiler and cogeneration, the power and heat power systems operate in isolation. To analyze the relationship between the information interaction and economic coordination and dispatch of the integrated energy system, by using the J.F.Benders mixed variable target decomposition method, the physical model of the cogeneration photovoltaic storage thermal power system is decomposed according to the main thermal system and the power subsystem. The information interaction between the sub-objectives is analyzed by the objective function and the system boundary conditions, and the mathematical model of the coordinated scheduling operation of photoelectric consumption and storage and cogeneration is obtained. The protection information is isolated and redirected, and the multi-dimensional variable problem of mixed integer programming is iteratively calculated by Gurobi solver. Based on the case of the integrated energy system, three operating conditions under different load requirements of power and heat are analyzed, and it is found that, the economic benefits of the thermal power operation system are synergistic and complementary, and the information interaction expands the space for photovoltaic consumption. The net load of the system reduces by 13.63% on average, the interactive power loss decreases by 9.480 7 million yuan/year, and the energy utilization efficiency rises by 4.48 percentage points, which shows that this model can serve the economic coordination and scheduling optimization and energy efficiency improvement of the integrated energy system.

Based on the time-of-use electricity price and the cost of wind-PV-energy storage system, technical and economic research of source-grid-load-storage system is studied. Firstly, a microgrid system model integrating renewable energy and energy storage system is proposed, which includes PV, wind power, energy storage system, grid, and load. Then, under the premise of ensuring reliable power supply to the load, an optimization model of the source-grid-load-storage system is established with the goal of optimizing the system economy based on load data, irradiation data, wind speed data, time-of-use electricity price data, and the costs of each unit of the system. Finally, the optimal capacity and economic feasibility of configuring a wind-PV-storage system in a certain region are analyzed in detail through a numerical example. The analysis results indicate that, the energy storage systems store energy at low electricity prices and release energy at high electricity prices, thereby avoiding users from purchasing electricity from the grid at high electricity prices and reducing the cost of purchasing electricity from the grid. The configuration of a wind-PV-energy storage system can effectively reduce the annual cost of purchasing electricity from the grid.

Due to factors such as coal quality and combustion, coarse fly ash particles in flue gas of coal-fired boiler can easily cause varying degrees of wear and tear on tail flue and denitrification catalysts. An “A-V-T” type pre-removal structure for coarse particle fly ash before denitrification is established using the flue from the economizer outlet to the denitrification system inlet of a 300 MW unit as the research object. The structure is composed of “A-type baffle enrichment + V-type high-efficiency ash collection + T-type coarse ash channel” and is placed in a large cross-section low flow velocity flue at the economizer outlet. The influence rules of different particle size distribution trajectories, removal effects and resistance before and after the arrangement of the coarse particle fly ash pre-removal device are studied through numerical simulation, and engineering application is conducted to verify the effectiveness. The numerical simulation results indicate that, the use of coarse particle removal technology has little effect on flow field state of the original system at flue gas side. As the particle size of fly ash increases, the removal rate of fly ash increases. The removal rates of fly as particles with size of 50, 200, 500, and 1 000 μm are 12.15%, 59.40%, 87.01%, and 93.62%, respectively. The removal efficiency for coarse particles with size of 200 μm and above is 85.15%. The overall ash collection rate is 15.50%, with an additional resistance of 78 Pa. For this 300 MW unit, the tests after retrofitting show that, the removal rate of coarse ash particles with size of 200 μm and above is 83.96%, the overall removal rate of ash is 14.91%, and the net increase in resistance is 73 Pa. The experimental results verify the rationality of the numerical simulation results.

Wind power generation and solar thermal power generation have complementary advantages in terms of time characteristics, and the heat storage system equipped with solar thermal power station can effectively alleviate the peak regulation pressure and improve the wind power absorption capacity. On this basis, a solar thermal-wind combined power generation system is proposed. The Latin hypercube sampling method is used to effectively reduce the uncertainty of wind power output and solar irradiation intensity. Then, a two-stage double-layer optimal allocation method is proposed to rationally allocate the heat storage capacity. The upper layer model aims to minimize the investment cost of comprehensive operation of the system and the lowest curtailment of the system. The optimal heat storage capacity is determined by a fuzzy multi-attribute decision scheme. In the lower layer model, the operation is optimized with the goal of maximizing the net benefit of the cogeneration system in the scenario. The results show that the optimal heat storage capacity of the heat storage system of the solar thermal power station is 906 MW·h, and the comprehensive operating cost for the optimal heat storage capacity configuration is 2 430 000 yuan. Through the comparison between the results of different scenarios, the curtailment of the system with this configuration method reduces by 69.615 MW, and the net revenue of the system increases by 7.7%.

To improve the accuracy of carbon emission accounting and make the effect of carbon emission reduction more intuitive, it is proposed to associate power plant generation with carbon emission intensity. Firstly, the carbon emission performance of the gas-steam combined cycle unit is calculated based on Aspen Plus. Then, the carbon emission performance is analyzed from the aspects of four influencing factors: unit load, environmental temperature, heat network input and natural gas composition. The results show that, the established Aspen Plus model can simulate the operation of the power plant accurately. Taking the S106FA multi-axis gas-steam combined cycle unit of a power plant as an example, the calculated carbon emission performance is 342.66 g/(kW·h). The carbon emission is calculated by comparing the measured method and the emission factor method. The carbon emission performance accounting is closer to the measured method, and the deviation between the carbon emission performance method and the measured method is 0.20%. The deviation between the measured method and the emission factor method applying the measured low calorific value and the saved and deficient low calorific value are 5.24% and 19.66%, respectively. Unit load has the most obvious effect on carbon emission performance of the combined cycle unit, followed by heat network input, ambient temperature and natural gas composition. To reduce the carbon emission performance of the combined cycle unit, the power plant needs to arrange the peak regulation time and heat network heating reasonably, and using renewable energy as an alternative or supplementary fuel can be considered.

A new type of liquid air energy storage (LAES) system coupled with solar energy is proposed to address the issue of low round-trip efficiency (RTE) in current LAES systems. The discharging process of the new system is equipped with series-connected two-stage air heaters, which improves the RTE while allowing the system to operate in conventional ways under low solar radiation conditions. Sensitivity analysis of main parameters and exergy analysis are conducted on the new system, and the results show that, within the allowable range, the lower the liquefaction temperature, the lower the charging pressure and the higher the discharging pressure, resulting in higher RTE of the system. The optimal RTE of the system can reach 72.4%, and the system can still operate at an RTE of 53.6% when solar radiation is insufficient. The exergy efficiency of the new system is 38.0%, among which the solar collector field has the highest exergy destruction, accounting for 52.4% of the total exergy destruction, followed by the throttle valve and thermoelectric generator. In heat exchangers, there is significant exergy destruction in cold boxes and evaporators.