With the expansion and continuous development of the photovoltaic power generation industry, photovoltaic modules will face large-scale decommissioning in the coming years, and the recycling of modules has become an important issue for global energy sustainability and the circular economy system. Decommissioned photovoltaic modules are rich in high-value precious metal elements such as silicon, silver, and aluminum, but also contain toxic substances such as lead and fluorides, which can cause significant harm to the environment and human health if not properly handled. The current development status and decommissioning status of the photovoltaic power generation industry, as well as the structure and main components and values of photovoltaic modules, are summarized. The principles, advantages, and disadvantages of recycling technologies such as physical methods, thermal treatment methods, and chemical methods are analyzed and compared. Moreover, the progress of recycling technologies in China is investigated. Finally, the recycling of waste photovoltaic modules is systematically summarized and prospected, providing a scientific basis and decision-making support for the low-carbon development and resource recycling of the photovoltaic power generation industry.

The rapid expansion of the cumulative installed capacity of wind power in recent years has driven the continuous growth of market demand for wind power operation and maintenance (O&M). Lubricating oil for wind turbine gearboxes is an indispensable and crucial component in O&M. The waste lubricating oil for wind turbine gearboxes is classified as hazardous waste due to its harmful components such as heavy metals and degraded additives. Its efficient recycling and harmless treatment are crucial for achieving clean development in the wind power industry. Firstly, based on the characteristics and composition of waste lubricating oil, the variation laws and underlying causes of typical performance indicators during operating are expounded, including kinematic viscosity, pour point, moisture content, particle contamination level, acid value, and elements (e.g. Fe, P, and S). These variations are primarily induced by factors such as external contamination, oxidation at high temperatures and pressures, and additive degradation. On this basis, the latest research progress in current waste mineral oil regeneration processes is systematically summarized, covering mainstream technical routes such as pretreatment, molecular distillation, solvent extraction, and hydrofining. Furthermore, the feasibility and limitations of the aforementioned methods in extending the service life of waste lubricating oil and realizing its recovery and regeneration are analyzed. The identified limitations include issues such as low treatment efficiency, insufficient processing depth, and restricted application. Finally, the future development directions of high-value waste oils represented by synthetic lubricating oil for wind turbine gearboxes are discussed from the perspectives of industrial development, technological advancement and life management. It emphasizes that establishing a classified recycling system, developing green and efficient regeneration processes, and implementing life management will be the key pathways to realizing a circular economy in the wind power industry.

Floating offshore wind turbines (FOWTs) are affected by various factors in the marine environment, which can significantly alter their motion states and thereby affect their power generation performance. The influences of ocean currents on motion response of the FOWTs under different wind and wave conditions are investigated, and their impacts on power output are also studied. A semi-submersible floating platform equipped with a 5 MW wind turbine is selected as the research object, and simulations are conducted using OpenFAST, FAST to AQWA (F2A), and AQWA software. The surge, heave, and pitch motion responses of the floating platform, as well as the power generation output, are calculated under three environmental conditions: steady wind with regular waves, steady wind with irregular waves, and turbulent wind with irregular waves. The motion responses and power generation output are then recalculated after the incorporation of ocean currents. The results indicate that ocean currents primarily have a significant impact on surge motion, with a maximum difference of up to 13%, while their effects on heave and pitch motions are relatively minor. In the calculation of power output under the three environmental conditions, ocean currents show no influence on the average or maximum power generation output of the wind turbine, with differences of less than 1% between cases. Additionally, under more complex conditions, the standard deviation of power generation output exhibits minimal variation, suggesting that ocean currents do not affect the fluctuation intensity of power output.

Focusing on the structural safety of a three-column floating foundation for floating wind turbines, this study systematically assesses its stability, ultimate strength, and fatigue strength. A full-scale finite element model is established using the SESAM software suite. Intact and damaged stability analysis is conducted according to relevant codes. The result indicates that all parameters comply with regulatory requirements and demonstrate excellent anti-overturning capability. In the ultimate strength analysis, based on load conditions considering various wave directions, amplitudes, and periods, it is found that the maximum structural stress concentration occurs at the connections between the buoyancy tanks and columns. Nevertheless, the overall stress levels remain within the design resistance limits. Employing the hotspot stress approach, fatigue strength assessment of critical connection areas shows that the fatigue damage at all checkpoints is less than 1, satisfying the design life requirements. The floating foundation structure meets all applicable code standards for stability, ultimate strength, and fatigue strength. Therefore, the research provides a significant safety basis for the engineering application of floating wind turbines in deep-sea environments. It also offers valuable methodology and guidance for safety assessments of similar projects.

The efficient valorization of CO2 and N2 from power plant flue gas represents a critical pathway toward advancing the low-carbon transition of energy systems. Electrochemical synthesis of urea by directly coupling CO2 and N2 in flue gas under ambient conditions offers dual benefits: converting greenhouse gases into high-value fertilizers while achieving carbon mitigation and resource recycling. This review systematically summarizes recent advancements in this field, highlighting optimized reaction pathways through novel catalyst designs such as heterojunction catalysts and conductive MOFs, which enhance the synergistic activation of N2 and CO2 and improve C-N coupling efficiency, achieving a record Faradaic efficiency of 48% for urea production. Future breakthroughs should focus on developing bioinspired catalytic materials, integrating photo-electrocatalytic systems, and innovating renewable-powered integrated processes for carbon capture-conversion-product separation. By analyzing technical principles, engineering challenges, and industrial linkages, this work underscores the pivotal role of electrocatalytic urea synthesis in coordinated carbon-nitrogen management for coal-fired power plants, providing a forward-looking strategic thinking for scaling up this transformative technology.

The resource-recycling of retired crystalline-silicon photovoltaic cells is of great significance for the recycling of materials and the green and healthy development of renewable energy. Currently, most recyclers of decommissioned photovoltaic modules mainly focus on the recycling of aluminium frames, while aluminium resources in crystalline-silicon solar cells have not been effectively recycled, leaving valuable silver within the cells. Therefore, a wet-recycling process for preparing silver powder was proposed, which involves leaching aluminum with liquid alkali, leaching silver with nitric acid, and liquid-phase reduction. By optimizing the experimental parameters, under the conditions of a sodium-hydroxide concentration of 1.0 mol/L, a temperature of 20 ℃, a liquid-to-solid ratio of 10:1 (mL/g), and a reaction time of 40 min, the leaching rate of aluminum from the retired crystalline-silicon photovoltaic cells reached 98.88%, and the leaching-loss rate of silicon was only 0.46%. Under the conditions of a nitric-acid concentration of 4.0 mol/L, a temperature of 70 ℃, a liquid-to-solid ratio of 5:1 (mL/g), and a reaction time of 60 min, the leaching rate of silver reached 98.00%. Using ascorbic acid as a reducing agent, silver powder with a purity of over 99.9% was successfully prepared under the conditions of a molar ratio of ascorbic acid to silver ions of 1.25:1.00, a temperature of 30 ℃, and a stirring speed of 250 r/min. This process achieves high recovery rates and product purity, offering a practical pathway for crystalline silicon solar cell wafers recycling.

The Brayton cycle-based tower solar thermal power system features a flexible layout and operates at high receiver temperatures. However, fluctuations in solar irradiance can lead to thermal fatigue of receiver materials or excessive surface temperatures, necessitating effective strategies to mitigate temperature fluctuations. This study develops a manganese-based thermochemical thermal protection coating utilizing a reversible redox reaction. When solar radiation intensifies and the temperature exceeds 978 ℃, the coating undergoes a reduction endothermic reaction, reducing the heating rate. Conversely, when solar radiation decreases and the temperature drops below 878 ℃, an oxidation exothermic reaction occurs, slowing the cooling rate, thereby stabilizing receiver surface temperature fluctuations. Experimental results indicate that when the mass ratio of the coating material to the binder is 4:3, the adhesion strength reaches the highest national standard level, and the solar weighed average absorptivity achieves 94.93%. After undergoing 500 hours of thermal aging at 950 ℃, 100 cycles of thermal cycling, and 200 cycles of redox reaction tests, the coating’s weighed average absorptivity decreased by only 0.82, 0.98, and 2.61 percentage points, respectively, while maintaining the highest adhesion strength. Under a sudden change in concentrated solar radiation flux of ±9.7 kW/m², the heating and cooling rates in the first 100 seconds were reduced by 59.66% and 67.09%, respectively. Additionally, the time required for a 20 ℃ increase and decrease was extended by 182.50% and 438.60%, respectively. The manganese-based thermochemical coating demonstrates excellent aging resistance and effectively suppresses absorber temperature fluctuations, making it highly promising for applications in Brayton cycle-based tower solar thermal power systems.

The signals of flame spontaneous emission (passive method) and absorption spectrum (active method) are two commonly used optical measurement methods for reconstructing the combustion physical field. Developing an active and passive combined method by combining the respective advantages of the two methods will provide a new means for combustion detection. By introducing a laser absorption optical path into the passive measurement system to simultaneously obtain the spontaneous emission and absorption spectral signals of the flame, the combustion temperature field and the initial component concentration field reconstructed by the passive method are introduced into the active method reconstruction. The active and passive combined method is developed by combining the double regularization constraints of smoothness and the prior concentration physical field. Simulation reconstructions are carried out for typical single-peak and double-peak axisymmetric flame sections. When the measurement error is 1.00%, the average errors of the single-peak and double-peak flame combustion temperature field reconstructions are 0.92% and 1.32% respectively, and the average errors of water vapor volume fraction are 3.05% and 3.31% respectively. The results show that under the double regularization constraints, the reconstruction accuracy of water vapor concentration by the active and passive combined method is significantly improved compared with the passive method, and the number of required laser optical paths is greatly reduced compared with that of the active method, achieving accurate measurement of the combustion temperature field and component concentration field using a simple measurement system.

The existing flame radiation image temperature measurement technology has measurement errors due to the coking problem of the detector lens. There is an urgent need for an online monitoring method that can intelligently eliminate the coking interference. An online monitoring method for the temperature field of power station boilers that integrates flame radiation images and convolutional neural network (CNN) is proposed. Firstly, the detector is calibrated via a blackbody furnace, and the relationship between the monochromatic radiation intensity of the detector and the image intensity is established. Secondly, a CNN model suitable for flame image processing is designed, and the training set is constructed by using the non-coking flame radiation intensity images of the boiler collected on-site to establish the flame radiation intensity image restoration model. Finally, the measurement accuracy of this method is verified by using the simulated coking flame images. The results show that the temperature measurement accuracy decreases with the reduction of the number of training sets. When the number of flame images in the learning set is 3 000, the relative error of temperature measurement is 1.4%. The temperature measurement accuracy decreases as the coking area increases. When the coking area is 30%, the maximum relative error of temperature measurement is 0.7%. Furthermore, studies show that when the model of the detector trained by the learning set calculates the coked images of other detectors, the temperature measurement error will increase, with the maximum relative error reaching 34.6%. This indicates that when applying this method, the detectors of each burner need to be trained separately. The proposed method can intelligently eliminate the interference of coking on the flame radiation image, achieve high-precision online monitoring of the temperature field, and provide reliable technical support for the safe operation and combustion optimization of power station boilers.

Co-firing sludge is one of the important approaches to address the challenges of urban sludge accumulation. The field test of co-firing sludge dried by flue gas was conducted in a 350 MW supercritical coal-fired power unit to investigate the effects of blending amount and unit load on system operation and energy consumption. Wet sludge was dried using extracted boiler tail flue gas, with the dried sludge subsequently carried into the furnace for co-combustion. The results show that a positive correlation exists between the wet sludge amount and the temperature/flow rate of drying flue gas. Drying 11 t/h wet sludge required 71 t/h flue gas at 597 ℃. As the sludge blending ratio rose, the boiler thermal efficiency decreased, while the auxiliary power consumption ratio increased. The rise in sensible heat loss in exhaust gas mainly led to the decline in boiler thermal efficiency, and the rises in both unburned carbon heat loss in residue and sensible heat loss in residue were secondary factors. The rise in auxiliary power consumption ratio was primarily attributed to the high power consumption of the sludge drying system, with sludge co-combustion system dominating the rise in auxiliary power consumption ratio. The rise in net coal consumption rate was caused by the decline in boiler thermal efficiency and the rise in auxiliary power consumption ratio, and the rise in auxiliary power consumption ratio contributed more significantly. At 262 MW and with a sludge blending mass ratio of 8.76% (sludge moisture fraction: 83%), the boiler thermal efficiency decreased by 0.260%, the auxiliary power consumption ratio increased by 0.466%, and the net coal consumption rate increased by 2.38 g/(kW·h). The study provides a reference foundation for the energy consumption evaluation and optimization of co-firing sludge dried by flue gas in a coal-fired power unit.