In order to improve the efficiency of geothermal energy extraction in the hightemperature zone at the bottom of the well, a jettype coaxial borehole heat exchanger is constructed for horizontal geothermal well extraction. Based on the finite volume method, a threedimensional numerical simulation model of the horizontal section near the bottom of the well is established, and the flow and temperature fields of the Outsidein and insideout type (OI), Insideout type (IO), and Jet inlet (IOI) coaxial borehole heat exchangers are compared and analyzed, so as to reveal the mechanism of the injection heat exchanger to strengthen the heat transfer. The results showed that the use of the IOI type heat exchanger increased the turbulent kinetic energy of the fluid and formed vortices, which improved the efficiency of geothermal heat extraction. By comparing the heat extraction performance, it was found that the Nusselt number increased with the increase of mass flow rate, and the Nusselt number of IOI type was higher than the other two by 18.33%~32.48% and 5.33%~18.84%, and the friction coefficient decreased with the increase of mass flow rate; under the same mass flow rate, the thermal enhancement factor of IOI type heat exchanger was higher than the other two by 9.13%~13.58%, 3.61%~10.24%, and the average extraction temperature and average extended metre heat exchange are always the highest among the three. The results provide a theoretical basis for the efficient extraction of coaxial borehole heat exchanger in horizontal geothermal wells.

In order to solve the activepower dynamic oscillation problem of parallel system for traditional energy storage virtual synchronous generator (VSG) and diesel generator set (DGS) under load disturbance, an active power dynamic oscillation suppression strategy for diesel storage microgrid based on activepower proportional differential feedforward VSG (APDFVSG) is proposed in this paper. Firstly, the small signal model of the parallel system for energy storage VSG and DGS is established, as well as the influences of virtual inertia, virtual damp and output impedance parameters of energy storage VSG on active power oscillation of the system are analyzed. On this basis, the active power dynamic oscillation suppression strategy based on ADPFVSG is proposed and the corresponding parameter design process is given. Finally, the MATLAB simulation model of the parallel system for energy storage VSG and DGS is established, and the simulation results are used to verify the effectiveness of the proposed APDFVSG control strategy in suppressing activepower dynamic oscillation of the dieselstoragemicrogrid.

A large amount of lowtemperature waste heat generated in the industrial production process dissipates in the atmosphere through flue gas and cooling media. Recovering and utilizing such heat is of a great significance for improving energy efficiency and promoting the achievement of "dual carbon" goals. With a detailed review of cases of utilization of lowtemperature waste heat by existing factories, this paper compares heat exchange schemes and energy conservation effects under different heat source conditions, deriving that lowtemperature waste heat has a wide range of applications from waste heat heating, raw material preheating and antifreezing, waste heat refrigeration to waste heat power generation. It is pointed out that when utilizing lowtemperature waste heat resources, attention should be paid to heat source characteristics and factory needs and utilization approaches adapted to enterprises should be selected. Further, this paper also presents a prospect of the important effect of lowtemperature waste heat in energy conservation and emission reduction.

Taking an agricultural single cylinder diesel engine as the research object, the soot emission characteristics of biodiesel blended fuel were tested under the conditions of EGR rates of 0, 15% and 30% , and the influence of EGR rate on the combustion particle structure characteristics of biodiesel blended fuel was explored. The results indicate that biodiesel blended fuel can alleviate the problem of increased soot emissions caused by the introduction of EGR, and the improvement effect is more significant under high EGR rate conditions. The diesel engine exhaust particle size range is mainly between 20 nm and 80 nm, mainly showing normal distribution. Under the same EGR rate conditions, the particle size formed by burning biodiesel blended fuel significantly decreases, and the degree of agglomeration between particles increases, the porosity of particles increases, and the thickness of the interface layer increases. By adopting EGR technology, the average particle size of the particle group increases, the degree of agglomeration increases, the porosity of the particles decreases, and the thickness of the interface layer increases. Mixing biodiesel and introducing EGR can both increase the roughness and irregularity of the formed particles.

The virtual synchronous generator (VSG) control is proposed to obtain inertial support in the inverter control design, but it will bring the problems of power oscillation. In order to improve the power regulation and operation status of system, this paper proposes a VSG power oscillation suppression strategy based on adaptive fuzzy sliding mode compensation. Firstly, the mathematical model of VSG is constructed, and the causes of VSG oscillation are analysed. Secondly, an adaptive fuzzy sliding mode compensation is designed by Lyapunov function to make its frequency and power angle converge quickly, so as to suppress the power oscillation, and its stability is proved. Finally, the simulation and experimental results show that the proposed VSG control strategy can significantly suppress the power oscillation during startup and power sag. The system overshoot is reduced and the response time is faster, so the system operation state is improved.

This article investigates the ability of suction anchor foundations in clay to withstand horizontal and bending moment combined loads, as well as vertical and bending moment combined loads. First, the rationality of the finite element model is verified through numerical simulation tests. Based on the finite element method, a suction anchor foundation model with an aspect ratio of 1 is established. The bearing capacity characteristics of the suction anchor foundation under the combined action of horizontal load, vertical load and torque load are studied. The results show that under the action of torque load, the horizontal and vertical bearing capacity of the suction anchor foundation is significantly reduced. With the decrease of the horizontal load point, the ability of the suction anchor to resist the torque load shows a trend of first increasing and then decreasing. In the case of the combination of horizontalverticaltorque loads, the decline trend of the ultimate bearing capacity of suction anchors increases significantly with the increase of torque loads. As the angle between the load direction and the horizontal plane increases, the bearing capacity of the suction anchor to resist torque loads tends to increase.

The wind turbine is developing towards largescale and intelligent, the loads of the turbine are increasing exponentially, which puts forward higher requirements for the dynamic design of the turbine components. In this paper takes the elastic support of wind turbine gearbox as the research object, and the dynamic model of entire wind turbine is established by using multibody multidynamics software, coupled with the calculation of aerodynamic load and the control program of wind turbine. The timefrequency characteristics of the dynamic response of the elastic support under uniform wind are calculated, and the influences of wind shear, tower shadow effect and nonlinear stiffness on the elastic support are compared and analyzed. Finally, the dynamic response of the elastic support of the wind turbine under the condition of turbulent wind are simulated. The results show that when the elastic support is damaged and only matches 50% of the stiffness, the response of the elastic support increases sharply, exceeding the vibration standard safety threshold by more than 4 times, which affects the safe and stable operation of the whole wind turbine.

This study proposes a coagulationdissolved air flotation and microwave drying processes based on biologic coagulant for harvesting cyanobacteria biomass, and a pilot system with a treatment capacity of 20 m³/h was developed. Continuous operation in Lake Tai demonstrated that the system achieved a harvesting efficiency of up to 95% for cyanobacterial biomass, with the moisture content of the biomass reduced to below 85% after dehydration. After 10 min of continuous microwave drying, the moisture content of the biomass was further reduced to below 10%, with no adverse effects on the main nutrients, such as proteins and sugars. Further technoeconomic and cost sensitivity analyses revealed that the total cost of harvesting and drying cyanobacterial biomass was 4 134.1 ¥/t dry biomass, with bioflocculant costs accounting for more than 50% of this total. The processing costs were found to be significantly influenced by the dosage and cost of bioflocculants, as well as the hourly microwave drying capacity.

With the deepening reform of the energy market, the important role of demand response resources in the lowcarbon operation of comprehensive energy systems is becoming increasingly prominent. This article proposes a new strategy for integrated energy systems that considers tiered carbon trading and bidirectional supply and demand responses. Firstly, a stepped carbon trading comprehensive energy system model with a reward and punishment mechanism was established, and based on this model, a bidirectional supply and demand response and compensation mechanism were further proposed. Secondly, an optimization scheduling model was constructed for the system, with the objective function of minimizing the sum of operating costs, demand response compensation costs, and carbon trading costs. Finally, apply the CPLEX toolbox to simulate and solve the optimized model. Through case analysis in different scenarios, this article explores the impact of supply and demand bidirectional response strategies and carbon trading mechanisms on system operation. The simulation results confirm the effectiveness and superiority of the proposed strategy.

In this paper, a fault diagnosis strategy for photovoltaic modules based on IV curve inverse method is proposed. This strategy does not need to monitor the surface irradiance and average temperature of the solar cell in real time. After extracting the model parameters, the IV curve library under different irradiance and solar cell temperature is calculated. The open circuit voltage, short circuit current and maximum power point voltage and current of the photovoltaic module are measured during operation to determine whether the module is faulty. By building experimental equipment to simulate typical faults and using this method to judge, the results show that the method proposed in this paper can effectively monitor the faults of components. Using this method, a singleboard fault monitoring module is developed to realize online fault diagnosis of photovoltaic modules, which improves the accuracy of fault diagnosis of photovoltaic modules and the reliability and economy of photovoltaic power station operation.