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.

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.

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.

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.

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%.

In Active Distribution Network (ADN), the penetration rate of Renewable Energy Sources (RES) is continuously increasing, leading to more complex and uncertain operational scenarios. This complexity introduces significant risks in the daily operations of ADN. This study proposes a collaborative configuration of distributed power sources within ADN to enhance the absorption capacity for renewable power. The proposed model thoroughly considers the variability of RES, the characteristics of adjustable demand response resources, the bidirectional flow of ADN, and the constraints of safe operation. To address the contradiction between the effective absorption of renewable energy and the economic operation of ADNs, this paper introduces a multiobjective Bayesian optimization algorithm based on hyperspace indicators (EBO). This method probabilistically models multiple objective functions, effectively balancing the exploration of solution space and the unidirectionality of optimization. Moreover, its computational efficiency surpasses traditional heuristicbased multiobjective planning algorithms.

To solve the problem of multitime scale power and energy imbalance in clean energyrich areas, this paper proposes a collaborative configuration method for seasonal and shortterm hybrid energy storage systems based on the principle of coconstruction and sharing on the power generation side. First, a crossseason sequential coupled operation model of the hydrogen energy storage system is established according to the seasonal output characteristics of hydropower. Second, a coupled operation mechanism of the hydrogenelectric energy storage system on the intraday time scale is proposed. A planning model for the hybrid energy storage system is developed to maximize the annual net income of the generation side after the system is configured. The nonconvex nonlinear programming model is converted into a mixed integer linear programming model. Then, the investment cost of the hybrid energy storage system is reasonably apportioned, considering the differentiated investment risks faced by different stakeholders on the power generation side. Finally, actual data from a region in Zhejiang Province is analyzed. The results show that the proposed method can effectively mitigate seasonal energy imbalance and intraday power imbalance in the region while ensuring the stability of cooperative energy storage system construction among stakeholders on the generation side.

Ubend Deep Borehole Heat Exchanger (UDBHE) has attracted much attention because it can effectively exploit deep geothermal energy and has high heat transfer performance. The thermophysical properties of mediumdeep ground generally change with depth, but there is a lack of indepth study on the influence of thermophysical properties of stratified ground on the heat transfer performance of Ubend deep borehole heat exchanger. Based on the UDBHE semi analytical heat transfer model established by the authors, the influence of thermophysical properties (thermal conductivity and volumetric heat capacity)of stratified ground on the heat transfer performance of UDBHE is studied. The results show that the thermal conductivity of each layer of ground has a great influence on the heat transfer performance of UDBHE, while the volumetric heat capacity of ground in each layer also has a certain influence, and the influence increases with the increase of ground layer depth. With the increase of time, the influence of ground thermal conductivity on the heat transfer performance of UDBHE gradually increases, while the influence of ground volumetric heat capacity on the heat transfer performance of UDBHE is basically unchanged. By keeping the weighted average values of the thermal conductivities of all ground layers constant, the heterogeneity of ground thermal conductivity has a great influence on the heat transfer performance of UDBHE, and the larger degree of heterogeneity of ground thermal conductivity would promote the heat transfer performance of UDBHE, otherwise it will inhibit the heat transfer performance of UDBHE. Similarly, the heterogeneity of volumetric heat capacity of ground also has a certain influence on the heat transfer performance of UDBHE, but its influence changes slightly with time. The research results provide important reference value for UDBHE performance prediction and optimization.

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%.

With the largescale integration of clean energy sources such as photovoltaics and energy storage into the power grid, grid type control technology has obvious advantages in dealing with voltage stability issues in new energy power systems that lack synchronization. However, how to adaptively control the parameters of grid type photovoltaic storage inverters to maintain voltage stability even when the impedance of the power grid changes is an urgent problem that needs to be solved. Based on this, a method for optimizing the control of optical storage grid inverters using a convolutional neural network optimized by the gazelle algorithm is proposed. Firstly, build a control model for grid type inverters and analyze the stability of output voltage; Secondly, based on the convolutional neural network, an inverter parameter control model is established, and the Gazelle optimization algorithm is utilized to optimize the hyperparameters of the convolutional neural network with strong optimization ability and fast search speed, improving the model's feature learning ability and outputting inverter control parameters; Finally, a certain photovoltaic power generation area was selected for simulation verification. The experiment showed that the proposed grid type photovoltaic inverter control method can adaptively optimize control parameters based on realtime changes in grid impedance, achieve stable voltage output, and have strong practical engineering significance.