A novel compressed carbon dioxide (CO₂) energy storage system based on gas-liquid phase change was proposed to promote the development of large-scale and high-efficiency energy storage technology. The overall pressure level of the proposed system is lower than the critical pressure of CO₂, which effectively reduces the difficulty of component manufacturing and improves the economic performance of system. Thermodynamic and economic analyses of the system were carried out and results show that the energy storage efficiency of system is 65.35% under typical design conditions and the investment payback period is about 5.50 years. The results of exergy analysis show that the maximum exergy destruction belongs to turbine which is 1.23 MW, and the evaporator has the minimum exergy efficiency which is 9.41%. The results of parameter analysis show that increasing the CO₂ condensation temperature, compressor isentropic efficiency and turbine isentropic efficiency, or decreasing the temperature difference between the cold end and hot end of heat exchanger 2, and the temperature difference between the cold end of heat exchanger 3, can improve the energy storage efficiency and shorten the investment payback period of the proposed system.

Syngas purification technologies for various pollutants in syngas were mainly reviewed, and the technologies can be classified into hot and cold gas purification according to different treatment methods and different treatment temperatures. For solid particulate pollutants, physical removal is used for both hot and cold gas purification; for tar treatment, physical separation is generally used for cold gas purification, while the methods such as adding catalysts during high-temperature thermal cracking or gasification process are used in hot gas purification; based on a good water-solubility of nitrogenous pollutants, most of cold gas purification technologies use water, acid or organic solvents to absorb directly, while hot gas purification usually uses catalytic oxidation; compared with nitrogenous pollutants, cold gas purification for sulfurated pollutants, not only can use liquid solvents to absorb, but also can use solid adsorbents such as porous carbon materials to absorb, and metal oxides are considered to have good adsorption properties for sulfurated pollutants at high temperatures. For chlorine compounds removal, cold gas purification is applied through following two mechanisms, such as ammonium chloride (NH₄Cl) deposition and absorption of hydrogen chloride (HCl) vapor, hot gas purification is applied through metals depositing with halides as halide salts.

As a new combustion technology, oxygen-enriched combustion can effectively improve the clean utilization of biomass fuel and provide high-concentration CO₂ flue gas for carbon capture and utilization. At present, the technology is still in the stage of research demonstration at home and abroad. By systematically sorting out the basic characteristics of biomass fuels, the characteristics of biomass oxygen-enriched combustion and related engineering research status were high lighted, and its development trend of this technology was analyzed. Results show that oxygen-enriched combustion can reduce heat loss and improve combustion stability and boiler operation efficiency to a certain extent. It can effectively control the temperature inside the furnace and alleviate the problem of pollutant emissions by dynamically adjusting the recirculation ratio through flue gas recirculation. There may be technical problems in the oxygen enrichment system, air distribution system, slag formation of the heating surface and the sealing of the whole furnace, etc., and main measures to prevent risks are to select appropriate oxygen injection and oxygen mixing mode, dynamic adjustment of oxygen and air distribution mode, anti-slagging treatment and sealing transformation. The efficient utilization of biomass energy coupled carbon capture and storage technology based on oxygen-enriched combustion is expected to become the direction of the transformation and development of biomass power plants.

For the unstability issue arising from the high ratio of renewable energy sources in power grid under the background of carbon neutralization, the demand features of various scenarios in the power grids for energy storage were introduced. The characteristics and development status of electrochemical energy storage technologies including supercapacitors, alkali-metal-ion capacitors and batteries, flow batteries, other secondary batteries, and hydrogen-based energy were discussed. The challenges and prospects of electrochemical energy storage technologies for large-scale energy storage in power grids were analyzed. Finally, it is figured out that the electrochemical energy storage technologies should be developed in the direction of "high performance, high safety and low cost".

This paper provides a comprehensive review of the research progress in lignocellulosic biomass pyrolysis technology. The pyrolysis mechanism of various biomass raw materials are summarized, the composition and properties of the products are analyzed, and the regulation, modification and application of the products are reviewed with emphasis. The results indicate that future research directions should focus on the following aspects: technological improvement, committed to improving biomass pyrolysis technology, enhancing energy conversion efficiency and product selectivity; diversification of products, in addition to the main energy products generated by biomass pyrolysis, such as biochar, bio-oil, and biogas, developing high-value chemicals and materials, including bio based chemicals, special chemicals, and high-performance materials should also be focused on; integration with other energy conversion technologies to establish a multi-energy co-supply system by combining biomass pyrolysis with the processes like biomass fermentation, photocatalysis, electrolysis, and energy storage technologies.

High-power energy storage devices have significant advantages such as the high power density and rapid charge-discharge speeds. High-power energy storage devices have been widely used for a variety of applications requiring high power output and quick response time, such as grid frequency regulation, emergency starting for military armored vehicles, and energy recovery of port lifting equipment. Focusing on the mainstream power storage devices including supercapacitors, high-power metal ion batteries and metal ion hybrid capacitors, the basic working principles of various high-power electrochemical energy storage technologies were introduced, and the improvement strategies and research progress of domestic and foreign scholars in the electrode materials and electrolytes of high-power electrochemical energy storage devices were systematically summarized. Finally, the future research directions and application trends of high-power electrochemical energy storage technologies were forecasted.

The key technologies and research progress of lithium battery and supercapacitor hybrid energy storage system used for frequency regulation in auxiliary thermal power units were discussed, such as power/capacity optimization configuration of different types of energy storage, application of high-voltage cascade and modular multilevel (MMC) topology structure, and hybrid energy storage control strategies. The demonstration project of domestic hybrid energy storage assisted frequency regulation for thermal power units was introduced. Finally, the domestic development prospects of hybrid energy storage systems were prospected.

Considering the characteristics of high efficiency and zero carbon emissions of the semi-closed CO₂ cycle, and based on the semi-closed CO₂ power generation system integrated with liquefied natural gas (LNG) cold energy at present, an efficient utilization way of LNG cold energy was proposed. Results show that, for the base case, the energy consumptions of the air separation and compression processes are reduced by 70.4 and 75 MW, respectively, and with a net system efficiency of 63.76%, which is 9.48 percentage points higher than the conventional cycle. Furthermore, with optimization measures such as improving the system parameters and matching the heat capacities of regenerators, the net efficiency of the optimized case is further increased to 72.22%, and the exergy efficiency is 51.27%. Compared with the reference system Ⅱ of only integrating LNG cold energy within the power cycle, the exergy efficiency of cold energy utilization is improved by 28 percentage points.

Fretting fatigue life prediction analysis for compressor material TC11 specimens was conducted to study its potential engineering application. The basic flow of fretting fatigue life prediction method based on critical surface method was combed, and the experimental results and prediction results were compared. Results show that the smaller radian of the tenon working surface will reduce the SWT critical interface parameter value of the contact area, which is conducive to the improvement of fretting fatigue life. The error dispersion band between the predicted results based on SWT critical interface parameters and the experimental values is within 2 times of the factor, which has reference significance for the prediction of fretting fatigue life of actual components of aeroengines and gas turbines.

In order to study the changes in levelized cost of energy and cost of electricity supply after the carbon capture, utilization and storage (CCUS) retrofit of a coal-fired power station, the current development trend of the electricity-carbon market was summarized and analyzed, and a simulation model was built to show the cost and benefit of CCUS application for 660 MW coal-fired power station. A sensitivity analysis was carried out using the cost of carbon capture cost and carbon trading price as variables. Results show that the predicted levelized cost of energy of the thermal power units after CCUS retrofit will fall to the range of 20% upward fluctuation of the regional coal trading benchmark price between 2034 and 2035. After 2039, the change rate of levelized cost of energy before and after the transformation will be negative, which means that the levelized cost of energy after transformation will be lower than the target of levelized cost of energy before transformation. In addition, although the carbon capture cost and carbon trading price will have more or less impacts on levelized cost of energy and power supply cost, the coupling effect of carbon capture cost and carbon trading price still has good economic results in the future for the CCUS retrofit projects of the thermal power units.

Since the pressure and temperature of the compressed air in the gas storage are constantly changing during gas storage process in the compressed air energy storage system, which directly affects the output power of the compressor and the actual gas storage capacity, the temperature rise effect of the compressed air under adiabatic condition of 15 m pipeline steel was analyzed by numerical solution of differential equation, taking a gas storage of pipeline steel as an example. And Fluent was used for simulation verification. Considering the temperature rise of the pipeline steel and different heat transfer conditions, the thermal calculation for the gas storage process of the long-distance pipeline steel of 3 024 m was carried out. The coupling calculation of the gas storage process and the work process of the compressor was processed to obtain the change rules of the pressure and temperature of the compressed air in the gas storage process, the output power of the compressor, the actual gas storage capacity of the gas storage and other parameters. Results show that the mass mean temperatures of the compressed air at the end of inflation were 315.39 K, 311.65 K, 301.52 K and 291.35 K, and the gas storage capacities were 244.64 t, 252.60 t, 275.77 t and 301.35 t, when the comprehensive heat transfer coefficients of 0 W/(m²·K), 1 W/(m²·K),5 W/(m²·K) and 25 W/(m²·K) were adopted respectively.

Biohydrogen production technologies such as photolysis of water, photo fermentation, dark fermentation, and coupled dark-photo-fermentation were mainly reviewed. The hydrogen production mechanism, technological advantages and disadvantages, influencing factors and research status of each method were analyzed. At the same time, the types and characteristics of biohydrogen production reactors were compared. The results show that biohydrogen production has great potential in low-grade energy treatment and advanced energy production. Finally, some suggestions on the development of biohydrogen production technology were given.

A new deep conditional subdomain adaptive network (DCSAN) was proposed for the problems of insufficient labeled data and low diagnostic accuracy in the unsupervised cross-domain fault diagnosis field. The network mapped the confidence predicted by the classifier to the features extracted by the shared feature extractor to obtain the multimodal mapping features. And then the multi-kernel local maximum mean difference (MK-LMMD) was used to measure the distance between the multimodal mapping features in different domains. By minimizing the MK-LMMD and the loss functions of the classifier, the alignment of the corresponding sub-domain distributions in the source and target domains was achieved. The feasibility of the proposed method was verified on the bearing dataset of Jiangnan University. Results show that in six migration tasks under variable work conditions, the average diagnostic accuracy of the DCSAN model are 9.5%, 8.0% and 13.6% higher respectively than that of DAN, D-CORAL and DANN model. The proposed DCSAN model has certain effectiveness and superiority in sub-domain alignment and cross-domain adaptive fault diagnosis.

An integrated energy system based on source side of thermal power plant was proposed,which takes thermal power units as the core, couples multiple renewable energy inputs such as biomass gasification, garbage gasification and dried sludge at the input end of the system, and supplies multiple energy products such as colding, heating, steam and electricity at the output end. By coupling the thermal balance model of the power plant with the renewable energy model and cooling/heating system model, an optimization configuration method was established with efficiency and economy as the objectives. The following two types of optimization logics, input optimization and output optimization, were adopted to analyze the impact of the main operating parameters of the integrated energy system on the economy and efficiency optimization goals from the input and output ends of the system. Results show that integrated energy transformation has positive significance for current thermal power plants.

A parallel deep learning framework with adaptive optimization of weight parameters was proposed to address the accuracy and adaptability short comings of existing photovoltaic (PV) power prediction models when the data fluctuation patterns varied greatly in different application scenarios. The framework contained two parallel deep learning algorithm units such as Attention-Seq2Seq unit and Transformer unit and a weight parameter adaptive optimization unit. Based on the proposed parallel deep learning framework, the prediction of PV power generation was carried out and compared with the prediction results by Attention-Seq2Seq and Transformer models. Results show that the proposed framework not only can offset the lack of prediction accuracy and adaptability of single algorithm under different data fluctuation patterns, but also can effectively solve the long-distance dependence problem in time series prediction, which results in higher forecasting accuracy. The maximum reduction of average absolute error (E_MAE) and root mean square error (E_RMSE) is 41.18% and 45.59% in a typical day of summer, respectively,while the maximum reduction of E_MAE and E_RMSE arrives at 81.13% and 82.86%, respectively in a typical day of winter.

To achieve effective integration of renewables and reduce the instantaneous power fluctuations of wind power, a hybrid energy storage system (HESS) combining lithium battery-based energy storage and flywheel-based power storage was used to stabilize wind power fluctuations. Firstly, the improved k-means algorithm was used to obtain the typical daily data, and empirical mode decomposition (EMD) was used to disassemble it to obtain the HESS flattening task. Based on the comprehensive consideration of power capacity and charging-discharging efficiency constraints of various energy storage systems, a coordinated HESS energy management system was constructed. Moreover, with the minimum costs of hybrid energy storage system and wind power opportunity compensation as the objective function, a baseline variable and fluctuation penalty coefficient were introduced for correction, and a HESS capacity allocation model for stabilizing wind power fluctuations was developed. Finally, with the actual grid-connected data, a configuration scheme with optimized smoothing effect and economic performance was obtained. Results show that the cumulative under-compensation of wind power in the proposed configuration scheme is reduced by 91.8%, and the economic performance is increased by 49.99%. The optimal wind-storage ratio is 1∶0.16, of which the flywheel and lithium battery is 1∶4.65.

During chemical looping combustion, oxygen carrier plays a crucial role as the carriers of oxygen and heat. Design of oxygen carrier has always been the emphasis and difficulty in chemical looping technology research. Chemical looping combustion usually occurs in a fluidized bed reactor. Since the chemical stress caused by chemical reactions has the greatest contribution rate to the abrasion of oxygen carrier, the life of oxygen carrier is significantly shortened and the effective components run away. From the perspective of oxygen carrier structure design, the anti-abrasion mechanism of different composite oxygen carriers was qualitatively evaluated. The core-shell structure inhibits the phase separation of the active components and avoids the deactivation of oxygen carrier caused by surface abrasion of the active components. The addition of Al₂O₃ fiber and "rivet" inhibits crack growth and slows down the abrasion of the material. The addition of fuel ash improves the skeleton strength of the composite oxygen carriers, and the resistance to abrasion and slagging aggregation of oxygen carriers. The synergistic effect of the composite oxygen carrier increases the reactivity and slows down the sintering agglomeration phenomenon. From the perspective of abrasion dynamics and service life, the abrasion conditions of different oxygen carriers were quantitatively compared. By logarithmically fitting of the Gwyn abrasion dynamics equation, fitting parameters K and n of different oxygen carriers were calculated, which reflects the abrasion mechanism and abrasion patterns.

Gas turbine combined cooling, heating and power (CCHP) technology has excellent development and application prospects. However, there are many problems such as low efficiency in partial load operation, strong coupling of thermal-electrical output and inflexible regulation of thermoelectric ratio etc. To solve these problems, a novel CCHP system based on gas turbine and constant-pressure compressed air energy storage (CAES) was developed. The thermodynamic models of components such as the compressor, combustion chambers, turbine, waste heat boiler, heat exchanger, injector and water pumps/turbine, were developed and used to analyze the operational characteristics of the CCHP system under an extraction-release gas flow regulation strategy. Results show that when the extraction-release coefficient is between 0 and 0.2, the CCHP system has a thermoelectric ratio regulating range of 0.58-2.27. During the variable load operation process, the primary energy utilization rate of the CCHP system changes within the range of 58.1%-59.5%, and the exergy efficiency is no less than 32.2%. For the developed CCHP system, the high comprehensive energy efficient and flexibility can be achieved under wide operating conditions.

To improve the reactive power compensation and voltage stability of doubly-fed wind farms, a zonal control method of reactive power and voltage in wind farms considering fuzzy multi-objective optimization was proposed. Based on the active power data, the wind farm was partitioned and dimensionality was reduced, and the reactive power optimization limits for each zone were calculated. The zonal reactive power margin index was defined to describe the safety margin of wind farm voltage operation. Taking into account both operation safety and stability, a fuzzy multi-objective optimization model for wind farm reactive power voltage was established. A self-adaptive genetic taboo algorithm that can quickly and globally optimize on a large scale has been proposed. the global timeliness of optimization was improved by redefining the crossover and mutation, and the accuracy of optimization was improved by introducing taboo algorithm. Finally, simulation verification was conducted using a doubly fed wind farm as an example. Results show that the proposed method can reserve sufficient reactive power margin for wind farms and significantly reduce voltage fluctuations within the system.

The heat transfer coefficient calculation models and methods for outer surface of steam pipe, main stop valve, control valve and outer casing of steam turbines were established. The heat transfer coefficient calculation formulas for inner surface of steam pipe, main stop valve, control valve, high pressure (HP) outer casing, intermediate pressure (IP) outer casing and low pressure (LP) outer casing of steam turbine, and the composite heat transfer coefficient of the outer surface of the insulation structure and the outer surface of the LP outer casing were given. The calculation model of the heat transfer process of the steam pipe, the metal inner wall of the HP outer casing and the IP outer casing and the double-layer casing wall of the outer wall of the thermal insulation structure, the metal inner wall of the main stop valve, control valve and the double-layer spherical wall of the outer wall of the thermal insulation structure, and the single-layer cylinder wall of the LP outer casing of steam turbine were established. Considering that the inner surface temperature and outer surface temperature of the inner metal wall and the outer surface temperature of the outer wall of the thermal insulation structure were both undetermined, the iterative method was used to determine the surface temperature of these steam turbine components, the heat transfer coefficient and the heat flow density of the heat transfer process. The calculation and analysis of the external surface heat transfer coefficient of the steam pipes, main stop valve, control valve, HP outer casing, IP outer casing and LP outer casing of the steam turbine were completed. The calculation results of the heat transfer coefficient, heat flux density and equivalent surface heat transfer coefficient of the metal inner wall outer surface of these steam turbine components during the heat transfer process were obtained, providing heat transfer boundary conditions for finite element numerical calculation of temperature field and stress field of these steam turbine components.

Chemical-looping reforming of biomass using Cu-based oxygen carriers was analyzed in a thermogravimetric analyzer (TGA) and a small fluidized bed reactor respectively, and the influence of oxygen carriers and reactor temperature was studied. Results show that, compared with Fe-based oxygen carriers and quartz sand, the use of Cu-based oxygen carriers results in larger weight loss and weight loss rate, since Cu-based oxygen carriers can release oxygen at high-temperature and thus accelerate the pyrolysis and gasification of biomass. Meanwhile, higher temperature leads to higher gasification efficiency, gas yield, conversion efficiency and gasification rate. The Cu-based oxygen carriers appear good redox ability, anti sintering ability and high reactivity.

In order to achieve more accurate feedforward control for the superheated steam temperature with wide load operation, a predictive feedforward signal model based on physical guided neural network (PGNN) was proposed, and the load segment allocation of multiple models was determined based on gap measurement. The PGNN prediction method of multi-model gap measurement adopted the multi-model gap measurement method to reasonably divide the load section. Combined with the long short term memory neural network guided by the superheater mechanism, the strong coupling and large inertia superheated steam temperature wide load feedforward signal can be accurately predicted. Results show that when in the wide load of the unit, the nonlinear degree of the control object gradually increases with the load reduction, and more models are needed. The multi-model gap measurement PGNN feedforward control method can adopt feedforward signals suitable for the current working conditions under different working conditions, and improve the adjustment accuracy and stability of superheated steam temperature.

In order to further build a clean, low-carbon, economical and energy-saving energy supply system, a distributed energy system with wind, solar and multi-energy storage was established. For an office park in Beijing, DeST simulation software was used to predict user load and local wind and solar conditions. An adaptive optimal operation strategy was proposed to maximize the comprehensive benefits of economy, energy-saving and environmental protection. The exhaustive search method and genetic algorithm were used to optimize the optimal scheduling scheme of the system. Meanwhile, using the electric heating operation strategy as a comparison, the comprehensive benefits of the system under several different operation strategies were compared and analyzed. Results show that the average comprehensive benefit under the traditional following electrical load operation mode is 0.41 on average; under the adaptive optimization operation strategy, the average comprehensive benefit of the scheduling scheme obtained by genetic algorithm can reach 0.5, and the average comprehensive benefit of the operation scheme obtained by the exhaustive search method can reach 0.51.

In response to the challenges faced in the digital and intelligent operation and maintenance (O&M) of wind turbines, such as data overload of multiple units, information redundancy, low efficiency in maintenance knowledge retrieval and insufficient reasoning of life-cycle maintenance knowledge, a knowledge graph construction method for wind turbine operation and maintenance data was proposed. Firstly, important information such as faulty components and causes could be extracted using text data such as wind turbine equipment maintenance work orders, so as to provide the knowledge graph construction process for wind turbine operation and maintenance data.Subsequently, during the construction process, modeling analysis was conducted specifically for fault entities, attribute extraction and relationship extraction. Results show that the wind turbine O&M knowledge graph helps O&M personnel to accurately grasp the root causes of failures, efficiently implement maintenance measures, and ensure the repair capabilities of wind turbines under the conditions of informatization and intelligence. Moreover, compared to relational databases, the proposed design method offers better performance in terms of query precision and time.

The effect of channel height on the thermal-hydraulic performance of airfoil fin printed circuit heat exchangers(PCHEs) was investigated by numerical method based on the impact of channel geometry. Results show that channel height significantly affects the compactness, resistance, and heat transfer performance of PCHE. Under the same Reynolds number (Re=6 000-14 000), the Fanning friction factor f first decreases and then increasesas with the channel height H decreases (i.e., the ratio of channel height to transverse pitch H/S_T=0.12-0.60), with the lowest f observed at H/S_T=0.24. The Colburn-j factor j shows no significant change for airfoil fin channels with H/S_T=0.24-0.60, while an increase in j is observed at H/S_T=0.12. The ratio j/f is suitable for evaluating the comprehensive performance of airfoil fin channels with different heights. When using j/f as the comprehensive performance evaluation indicator, the airfoil fin channel with H/S_T=0.24 exhibits the best overall performance.

A coupled system based on reheated steam extraction and molten salt thermal storage was presented, and the operation processes and efficiency of the system were analyzed. In order to match the main steam temperature, electric heating was used to elevate the molten salt temperature after heat exchanging with extracted steam during the charging process. On this basis, the effects of average temperature difference in charging process, temperature difference of pinch point in discharging process and lower storage temperature of molten salt on system performance parameters were studied. Results show that with a fixed temperature difference of 10 K of the charging process, increasing the temperature difference of pinch point from 5 K to 15 K, the maximum equivalent round-trip efficiency reduces from 88.2% to 85.0%, and the optimal heat storage temperature will increase from 314 ℃ to 324 ℃. With fixed pinch point of 10 K, the round-trip efficiency decreased from 89.5% to 85.8% when the average temperature difference of the charging process increased from 5 K to 15 K. With both temperature differences of 10 K, the maximum equivalent round-trip efficiency is 87.1%, and the minimum load of the unit is reduced from 30% to 24.3%.

Based on the dynamic mesh technique, the vortex-induced vibration of wind turbine airfoil at 90° angle of attack was numerically studied by using the prescribed vibration method and the free vibration method respectively. Through the prescribed vibration calculation method, the vortex-induced vibration range of Du96-W-180 wind turbine airfoil at different amplitudes was determined, and the effects of changing the incoming flow velocity and changing the structural stiffness on the vortex-induced vibration range were compared. Through the free vibration calculation method, the vortex-induced vibration range of the airfoil at different inflow speeds was obtained. The influence of different structural damping on the vibration response of the airfoil at the frequency ratio r=0.93 and r=1.11 was compared, and the development and evolution process of the vortex-induced vibration of the airfoil were analyzed. Results show that vortex-induced vibration range at different frequency ratios is basically the same while changing incoming flow velocity and changing the structural stiffness. The free vibration numerical simulation verifies the vortex-vibration range of the forced vibration. When 6% structural damping is applied at different frequency ratios, the vibration of the airfoil exhibits two forms: vortex-induced vibration and forced vibration.

To investigate the environmental impact of biomass power-to-gas technology, two types of biomass, corn stalks and rice straw were selected. The life cycle of biomass power-to-gas technology was comprehensively assessed using the life cycle assessment (LCA) model. By using SimaPro software, LCA was carried out in the stages of biomass harvesting, biomass direct combustion power generation, production of CH₄ and H₂, transportation and utilization of CH₄, to identify the main environmental impact categories at each stage, and a comparative analysis of the environmental impact potentials between corn stalks and rice straw was performed. Results show that marine aquatic toxicity, global warming, freshwater aquatic toxicity and acidification are the more prominent environmental impact categories. In terms of marine aquatic toxicity, the rice straw power-to-gas technology is 2.8 times higher than the corn stalks power-to-gas technology. In terms of environmental impact categories such as global warming, human toxicity and acidification, the impact levels of corn stalks and rice straw are relatively similar.

Extreme weather events become more frequent because of climate change, posing a threat to the security and stability of the electricity system. Current researches about strategic reserve generation units mainly focus on policy evaluations or modelling simulations from the perspective of unit costs and power sale income, which do not adequately account for the economic and social effects they can bring. In order to comprehensively analyze the economics of strategic reserve generation units, a cost-benefit analysis model was established from the perspective of the whole society, considering the benefits including the guarantees for the economic production, health benefits for residents and labor force level, and the costs of strategic reserve generation unit investment and operation, and Sichuan power restriction event was taken as a case study for analysis. Results show that the benefit for 1 kW·h electricity that can be brought by the strategic reserve generation units is 4.77 yuan/(kW·h) and the required costs for 1 kW·h electricity generated by building new strategic backup units and using units that are close to retirement were about 1.91 yuan/(kW·h) and 0.47 yuan/(kW·h), respectively. Thus it is economically feasible to build and operate the strategic reserve generation units from the whole society perspective. At the same time, the operating hours are the most critical factor affecting the cost of strategic reserve generation units, and if the operating hours are less than 89 hours in a year, the unit's cost of electricity will be higher than its social benefits.

In order to select the optimal working fluid for the organic Rankine cycle (ORC)power generation system driven by a vapor-liquid two-phase hybrid geothermal fluid with the heat source temperature of 140 ℃, six dry working materials were selected and a system model was built in MATLAB. The influence of each working fluid evaporation temperature on the system thermodynamic performance was analyzed. The variation of the optimal evaporation temperature with the heat source temperature under different steam mass fractions was compared. The influence of heat source mass flow rate on the system net output power and the influence of evaporation temperature on the recharge temperature were studied. Results show that considering the effect of thermodynamic performance, physical and chemical stability, thermal source matching and system recharge temperature on geothermal ORC power generation system, R601a (isopentane) is the best suitable material for ORC power generation system driven by 140 ℃ vapor-liquid two-phase hybrid geothermal fluid as heat source.

A "green electricity" molten salt energy storage system was proposed, and mechanism model analysis on the key components of the molten salt heat storage system was analyzed, so as to conduct the mathematical model identification experiment and analyze dynamic characteristics. Results show that the molten salt heat storage system generally exhibits the characteristic of large inertia. Through the design of multistage heating and heat exchange devices, the temperature, flow rate and pressure of molten salt and steam in the molten salt system can be effectively controlled, improving the quality of heating steam and ensuring the stability of the entire system, meeting the thermal and power generation needs.

A thermal economic mathematical model was established for a 300 MW supercritical carbon dioxide (SCO₂) partially cooled cycle and partially cooled reheated cycle coal-fired power generation system. Using cycle thermal efficiency η_t, system exergy efficiency η_ex and levelized electricity cost C_LCOE as evaluation indicators, to conduct thermal economic comparative analysis on different systems and key parameters. Results show that under design conditions, η_t is 0.33% higher and η_ex is 0.35% higher at partial cooling reheat cycles compared to partial cooling cycles. Under the same parameter conditions, the coal consumption cost of both generator units exceeds 70%, and the boiler cost is much higher than the cost of other equipments. There exists optimal inlet pressure for the main compressor, such that η_t and η_ex reach the maximum, while C_LCOE reaches the minimum. As the inlet temperature of the main compressor increases, η_t and η_ex gradually decrease, while C_LCOE gradually increases. η_t and η_ex increase linearly with the increase of turbine inlet temperature, while C_LCOE first decreases and then increases.

Due to its unique advantages of large storage scale and without limitation by geographical conditions, liquefied air energy storage (LAES) can participate in peak-regulation transformation of existing coal-fired power units to promote the construction and development of new power systems. Therefore, a novel LAES system coupled with coal-fired power unit was proposed, and the thermodynamic and economic models of the coupling system were established to analyze the influence of the change of energy storage capacity on the coupling system. Results show that a 44.2 MW/176.8 MW·h LAES system can be selected for comprehensive considerations when coupling with a 670 MW coal-fired unit.Considering three low-load (30%THA, 40%THA, and 50%THA) conditions for the coal-fired power unit,the round-trip efficiency of the coupling liquefied air energy storage system is about 51%, which is about 9 percentage points higher than that of the independent LAES system. The rate of return on investment of the coupling LAES system is close to 10%, and the investment can be recovered within 14 years. The sensitivity analysis results show that it is beneficial to improve the economic performance of the system through enlarging the difference between peak and valley electricity prices.

In order to optimize the ignition delay time and CO mole fraction, a new optimization mechanism for methane oxygen-enriched combustion based on artificial-neural-network (ANN-OMOC) was proposed by simplification and optimization for the detailed methane oxygen-enriched combustion mechanism USC mech2.0, using the directed relational graph with error propagation, full species sensitivity analysis and artificial neural network (ANN). The results of simulation calculation and comparative analysis for methane oxygen-enriched combustion show that the prediction errors of ignition delay time and laminar flame velocity are reduced from 2.53%, 24.38% to 0.50%, 14.41% by use of ANN-OMOC, compared with the prediction error of the simplified mechanism FSSA for methane oxygen-enriched combustion. Meanwhile, compared with the simplified mechanisms DRGEP and FSSA for methane oxygen-enriched combustion, the optimized mechanism ANN-OMOC has the best prediction results for ignition delay time, peak mole fraction of OH and peak mole fraction of CO, with relative errors of less than 10%.

In order to improve the peak regulation capacity of combined heat and power (CHP) units and realize the thermoelectrolytic decoupling of the unit by using the heat network heat storage, the dynamic simulation models of a 350 MW cogeneration unit and its heat supply network system were established. The dynamic characteristics of the heat supply network and its heat users during the heat storage/release process and the influence of ambient temperature on the peak regulation capacity of the unit were studied. Results show that the lag time of the heat user increases with the increase of its distance from the first heat exchange station, and it is also directly affected by the heat load of itself and indirectly affected by the heat load of the other heat users. The relative heat storage/release power of the heat supply network first changes rapidly and then changes slowly after the change of the extraction steam flow rate. The temperature of the heat user changes approximately linearly, and its change rate increases with the increase of the variation range of the extraction flow rate, and the starting time of change is also advanced. The maximum peak regulation capacity of the unit increases slightly with the decrease of ambient temperature. When the ambient temperature decreases from 0 ℃ to -15 ℃, the peak regulation capacity of the unit increases from 23.8 MW to 29.7 MW. Increasing the heat storage time and the heat storage temperature and decreasing the heat release temperature can improve the peak regulation capacity of the unit.

Aiming at the problems that traditional vibration sensor is not easy to install and the acoustic signal analysis is easily interfered by environmental noise, an anomaly detection method for audio signal was used to test the running state of the rolling bearings based on Mel-Frequency cepstral coefficients(MFCC) and Mahalanobis distance weighting support vector data description (MDE-SVDD). In this method, MFCC was extracted from the running sound signal of bearings as the feature vector, and then Mahalanobis distance weighting was used to improve SVDD, so as to enhance the anti-interference of noise samples and improve the detection accuracy of the algorithm. Gaussian white noise of various intensities was added to the experimental sound signal to simulate the field noise environment, and the test results of the proposed method were compared with traditional anomaly detection methods such as SVDD. Results show that the anomaly detection accuracy of MDE-SVDD reaches 91.99% in the scene of low signal-to-noise ratio by -5 dB, which is 7.73% higher than that of the traditional SVDD model.

By means of equal volume wetting, cellulose with different crystallinity was loaded with 1-butyl-3-methylimidazolium chloride (［Bmim］Cl) ionic liquid, and cellulose and regenerated cellulose samples loaded with ionic liquids were obtained. The pyrolysis behavior of ionic liquid-loaded cellulose with different crystallinity was investigated in a fixed-bed reactor, and the three-phase products of biochar, biooil, and biogas were analyzed. Results show that the process of cellulose regeneration can destroy the internal crystal structure, making the amorphous region larger and making dehydration easier to occur. When the pyrolysis temperature is 275 ℃, compared with cellulose, the regenerated cellulose with lower crystallinity can promote the production of volatiles and inhibit the production of solid carbon, and the liquid yield and solid yield will change from 48.23% and 48.81% to 55.7% and 37.67%, respectively. However, at high temperature of 300-350 ℃, the opposite is true. Loading ionic liquid can promote the production of substances such as LGO, with a maximum yield of 16.1%. High crystallinity can promote the catalytic effect of ionic liquid on LGO.

Aiming at the complex characteristics of selective catalytic reduction (SCR) denitration system with multiple disturbances, large inertia and model uncertainty, a control method based on self-coupling PID (SCPID) control theory was proposed. This method defines all complex factors such as internal disturbance, external disturbance and model uncertainty in the SCR denitration system as total disturbance, and then maps the system to a linear disturbance system. Based on this, a controlled error system under the inverse excitation of the total disturbance was constructed. Then, two separated self-coupling PID controllers were designed for the inner and outer loops of the SCR denitration system, so that the dimension of the control force matched the controlled system. Finally, three simulation experiments were conducted to verify the effectiveness of the proposed method. Results show that the proposed SCPID control method in this paper has fast response, small overshoot, strong anti-interference ability and good robustness.

In order to further exert the multi-energy complementary advantages of the integrated energy system (IES), an optimized operation strategy of integrated energy system (IES-PTC-CAES) integrating with advanced-adiabatic compressed air energy storage system (AA-CAES) and parabolic trough solar collector (PTC) was proposed. Firstly, the AA-CAES, PTC and other equipment in the system were analyzed and the corresponding models were established. Then, economy, environmental protection and energy efficiency were treated as the optimization objectives, and the key parameters of equipment operation were treated as the optimization variables, a collaborative optimization strategy was established based on time-of-use electricity price. The simulated typical annual load was clustered into typical daily load by K-means algorithm. Finally, the optimal operation strategies of IES-PTC-CAES under different objectives were obtained by the parallel genetic algorithm. Results show that compared with the reference system, the cost under the economic target is reduced by 146 100 yuan, and the carbon dioxide emission under the environmental protection target is reduced by 6 194.38 kg.

Heavy-duty gas turbine is a kind of efficient thermo-mechanical conversion equipment so far, with the combined cycle efficiency higher than 60%. As gas turbines have excellent peak shaving capability, they will play an increasingly important role in the new power network based on new energy. An overview of the working characteristics, the structural features and main technical parameters of heavy-duty gas turbine compressors were introduced. The development and technical progress of typical gas turbine compressors from major international original equipment manufacturers were reviewed. The research progress of compressor design system was summarized. Considering the development of advanced heavy-duty gas turbine technology, key technology development directions were proposed, including aerodynamic layout optimization, high performance airfoil, full 3D design of transonic stages and highly integrated design system, based on the development status of heavy-duty gas turbines in China.