The effects of reaction temperature and alkaline catalyst on the yield of pyrolysis products and the selectivity of methoxy-aromatic compounds were studied during microwave-assisted pyrolysis of eucalyptus sawdust in a fixed-bed reactor. The results showed that 400 °C was the optimum temperature for methoxy-aromatic compounds production, where the yield of bio-oil was 28.4%, and the concentration of methoxy-aromatic compounds in the bio-oil reached to 70.4%. The dominant methoxy-aromatic compounds were identified as guaiacyl and syringyl derivatives. Weakly alkaline catalysts (K₂CO₃ and Na₂CO₃) enhanced both bio-oil yield and the methoxy-aromatic compounds selectivity. However, the strong base NaOH reduces methoxy-aromatic compounds content. The catalytic efficiency for methoxy-aromatic compounds selectivity followed the order: Na₂CO₃ >K₂CO₃ >NaHCO₃ >NaOH. Furthermore, the reaction mechanisms underlying the formation of MACs from woody biomass and their subsequent conversion into benzoquinone, phenol, and catechol were elucidated, with guaiacol serving as a key structural model.

This study provides an indepth analysis of the distribution characteristics, combustion characteristics, and energy utilization potential of wheat root stubble resources in Henan Province through comprehensive research, experimental testing, and statistical analysis. The results showed that the total theoretical amount of wheat root stubble resources in Henan Province was 54.304 million tons, and the total amount that could be collected was 39.642 million tons, which could be converted to 23.911 million tons of standard coal, among which the root stubble resources in the four cities of Zhumadian, Shangqiu, Zhoukou, and Nanyang were more abundant, accounting for about 1/2 of the total theoretical amount of root stubble resources in Henan Province; The industrial analysis of wheat stubble samples from different areas in Henan Province showed that the ash content was 10.3%~16.3%, the volatile content was 62.8%~69.1%, the fixed carbon content was 8.50%~14.74%, and the calorific value was 17.10~18.31 MJ/kg, and the total heat of wheat stubble fuel for possible resource utilization was 6.99×10¹¹ MJ. The preliminary analysis of the distribution and energy utilization potential of wheat root stubble resources can provide an important reference and basis for the rational development and utilization of wheat root stubble resources.

With the development of new power system construction, various energy sources are integrated into the distribution network in the form of clusters and networks, making the distribution network exhibit active characteristics. Fully leveraging the complementary characteristics of multiple energy sources can alleviate the uncertainty of the distribution network while providing sufficient demand for electricity, heat, gas, cooling, heating, and other resources on the demand side. The existing distributed coordinated control methods only consider the gas network, heat network, and power network, without considering the hydrogen energy network. Provide a comprehensive and distributed coordinated control method for active distribution network, heating network, natural gas network, and hydrogen energy network, as well as energy interconnection. Firstly, the economic goal of minimizing operating costs was established, and the constraints of each network were provided; Secondly, a hierarchical control strategy is proposed for the active distribution network, heating network, natural gas network, and hydrogen energy network, and an improved consistency algorithm and particle swarm optimization method are used for solution comparison; Finally, a simulation example of an actual power grid is given, and it is found that the distributed comprehensive energy interconnection scheduling control method can achieve the same results as traditional methods, and the effectiveness of the proposed scheduling control strategy is verified.

Dust accumulation in the cover plate of flatpanel solar collector will reduce the heat collection performance, but there are few studies on selfcleaning of the cover plate. The mechanism of particle deposition was analyzed, and superhydrophobic and hydrophobic coatings were selected for dust suppression in flat plate collector. In order to verify the feasibility and quantify the dust suppression effect of the selected coating, natural dust accumulation experiments were carried out on three sets of collectors using superhydrophobic coating, hydrophobic coating and uncoated glass cover plate in Urumqi city, and the performance parameters of each system were analyzed. The results show that the superhydrophobic coating can effectively improve the heat collection performance of the plate collector under the condition of natural dust accumulation, but the effect of the hydrophobic coated glass plate is inferior to that of the bare glass plate. After 16 days of natural dust accumulation,compared with the bare glass cover collector, the transmission ratio of the superhydrophobic coating cover collector is increased by 3.6%, the heat collector temperature is increased by 3.96%, and the heat collection efficiency is increased by 2.94%. In the 16 d overall comparison, compared with the bare glass cover collector, the transmission ratio of the superhydrophobic coating cover collector is increased by 1.66%, the heat collector temperature is increased by 4.09%, and the heat collection efficiency is increased by 2.90%.

The networking of multiple DC microgrids under DC distribution network will become an effective means to accept largescale distributed energy and load with DC characteristics. The stability research of multivoltage levels DC distribution system is an important issue in its design and operation. Therefore, a stability analysis method suitable for multi voltage levels DC distribution system with multi DC microgrids was proposed. Firstly, the equivalent admittance of each microgrid subsystem is derived according to the control mode of the interconnected converter, and the equivalent openloop gain when each microgrid operates alone is used to judge whether there are right half plane poles in its equivalent admittance; Secondly, the multi voltage level DC distribution system is further simplified into a single voltage level DC system containing only medium voltage bus, and the stability of the medium voltage side subsystem is judged by the equivalent impedance ratio. When and only when the equivalent openloop gain of each microgrid and the equivalent impedance ratio of the medium voltage side of the system meet the Nyquist criterion, the system can operate stably; Finally, based on PSCAD / EMTDC simulation platform, a multi voltage level DC distribution system including two DC microgrids is built for verification. The simulation results show that the proposed stability analysis method can accurately determine the stability of multi voltage DC distribution system with multi DC microgrid.

Droop control is a common current sharing method for parallel converters in DC microgrid. However, due to the inconsistency of line parameters and the sampling error of sensors, the current distribution accuracy of traditional droop control is low. In order to solve this problem, this paper proposes a parallel current sharing strategy based on AC signal injection. Firstly, by superimposing an AC voltage small signal on the output voltage of the converter, the droop characteristic between the frequency of the AC voltage and the output current of the converter is constructed, and the reactive power generated by the signal and the feedback mechanism are used to realize the accurate current sharing of the converter. Secondly, the compensation virtual resistance is introduced to improve the stability of the system when the load changes greatly. Then, the design mode switching link stops the injection of AC signals in the steady state, so that the power quality can be improved. Finally, the effectiveness of the proposed control strategy is verified by simulation results.

In order to achieve good aerodynamic and structural performance of wind turbine airfoils simultaneously, an integrated optimization method for aerodynamic shape and internal topology of airfoils is proposed. The airfoil aerodynamic shape is represented using the Hicks Henne type function, and its aerodynamic performance is calculated by using XFOIL. A finite element model of the airfoil is established by using ANSYS, and the structural topology performance is computed. Based on this, a MATLAB program is developed by using a genetic algorithm with the objectives of maximizing the lifttodrag ratio and minimizing the compliance. Five basic airfoils of a 1.5 MW wind turbine blade are optimized under 3 objective weight factors, and the results showed that compared to the initial airfoils, all optimized airfoils exhibit increase in maximum lifttodrag ratio and decrease in structural compliance. At the same time, basically consistent internal structural conceptual design solutions are obtained with the spar caps on the upper and lower surfaces offset towards the leading and trailing edges, respectively. A comparison is made between the new blade using the optimized airfoils and the original blade, and the results indicate that the application of optimized airfoils combined with minor main spar caps offset, the aerodynamic and structural performance of the blades could be effectively improved.

The structure of flow channel is a critical factor affecting the performance of proton exchange membrane fuel cell (PEMFC). Optimizing the structure of the flow channel is essential for enhancing the performance and service life of PEMFC. Compared to straight channels, channels with varying shapes can improve reactant gas transport, thereby improving the output performance of the cell. In this study, a serrated channel with periodic crosssectional contraction is proposed. To analyze the transport characteristics and performance of this design, a three dimensional, Multiphysics coupled PEMFC model was developed using computational fluid dynamics (CFD) in COMSOL Multiphysics. The effects of the width and cycle length of the flow channel crosssection on the performance of the fuel cell was investigated. The results show that under high current density, the maximum net power of the serrated channel is increased by 6.12% compared to the straight channel, along with enhanced oxygen transport and liquid water removal. For the serrated flow channel, under the same flow rate conditions, moderate narrowing of the periodic contraction's minimum width improves oxygen distribution uniformity and drainage efficiency. Additionally, moderately reducing the contraction periodicity promotes gas flow velocity uniformity. The serrated channel with a narrowest width of 0.8 mm and a periodicity of 10 mm exhibits the highest net power improvement. However, excessive reduction in the narrowest width and shape variation period increases inlet pressure losses, ultimately degrading system net power.

Because of offshore wind turbine fully coupling calculation software FAST V8 can not simulate pile soil interaction, the updated FAST V8 is introduced by distributed linear spring boundary constraint condition and the coupled motion equation of substructure is derived. A coupled numerical simulation model of rotor nacelle –hub towerpile foundation structure with distributed linear spring boundary condition is established. The dynamic characteristics of the base fixed boundary and distributed linear coupled spring boundary model under the combined action of wind and wave are analyzed. The results show that the time history and frequency domain responses of the tower top displacement and the base bending moment change significantly, especially for the secondorder frequency of the structure. At the same time, it can be observed that the distribution spring boundary constraint condition has a more obvious effect on low wind speeds, while the fixed boundary constraint condition model has a more significant effect on high wind speeds.

Based on the porous medium model, a threedimensional double Utube heat exchanger heat transfer model considering groundwater seepage was established, and the effects of seepage velocity and tube flow velocity on the temperature field of the heat exchanger were investigated by numerical simulation method. Moreover, the comparison of heat transfer performance was completed for the round tube (the crosssectional aspect ratio =1) with the flatoval tube ( is 0.54, 0.44, 0.34, respectively). The results show that increasing the seepage velocity and the tube flow velocity can increase the heat transfer capacity of the tube. When decreases, the heat transfer capacity increases more in the inlet tube than the outlet tube, and more in the vertically arranged tube than the horizontally arranged one. Reducing the aspect ratio of the tube crosssection can reduce the thermal resistance of the borehole and improve the heat exchange capacity of the tube, but it will also make the pressure drop of the tube increase, and the thermal shortcircuit loss is increase. When v=1.50×105 m/s, u=1.3 m/s, compared to the round tube, the heat exchange capacity of the flatoval tube with (=0.34 increases by 11.4%, the thermal resistance of the borehole decreases by 20.52%, and the pressure drop increases by 24.32%.