In the fast filling process, in order to control the temperature of the vehicle-mounted storage tank not to exceed the upper limit of 85 ℃, it is an effective method to add a hydrogen pre-cooling system upstream of the hydrogenation machine. In this paper, Fluent is used to simulate the heat transfer process of high-pressure hydrogen in a shell-and-tube heat exchanger and the phase change process of refrigerant R23. The accuracy of the model is proven by comparison with the data in the references. Using this model, the temperature field and gas volume fraction in the heat transfer process is obtained, which is helpful to analyze the heat transfer mechanism. At the same time, the influence of hydrogen inlet temperature, hydrogen inlet pressure, and refrigerant flow rate on refrigeration performance was studied. The current work shows that the model can be used to determine the best working parameters in the pre-cooling process and reduce the operating cost of the hydrogen refueling station. In this study, a simplified two-dimensional model of a shell-and-tube heat exchanger was simulated using CFD technology. After the grid is divided, the appropriate turbulence model and discretization scheme are selected, before the simulation is carried out by changing the hydrogen inlet temperature, the hydrogen inlet pressure, and the flow rate of the refrigerant. Through the cloud diagram and numerical curve obtained by simulation, the influence of working parameters on the pre-cooling effect is explained in detail. This provides a certain reference for selecting suitable working parameters when the pre-cooling system of the hydrogen refueling station is running and reducing the operating cost of the hydrogen refueling station.

  To power large-scale energy storage systems, sodium-ion batteries (SIBs) must have not only high energy density but also high performance under a low-temperature (LT) environment. P2-type manganese oxides with high specific capacity are promising cathode candidates for SIBs, but their LT applications are limitedly explored. We proposed a P2-type Na0.67Ni0.1Co0.1Mn0.8O2 material with outstanding LT performance prepared through reasonable structure modulation. The material offers an excellent Na+ diffusion coefficient at −20°C, a superior LT discharge capacity of 147.4 mAh g−1 in the Na half-cell system, and outstanding LT full cell performance (energy density of 358.3 W h kg−1). Various characterizations and density functional theory calculations results show that the solid solution reaction and pseudocapacitive feature promote the diffusion and desolvation of Na+ from the bulk electrode to the interface, finally achieving superior electrochemical performance at LT.

  Aiming at the problems of the high rate of abandoning wind and light and power shortage during the grid connection of wind and solar power generation, a grid-connected wind, and solar hydrogen storage (alkaline electrolyzer-hydrogen storage tank-battery-proton exchange membrane fuel cell) coupling was constructed. Based on the system architecture, a grid-connected compensation/acceptance hierarchical control strategy based on wind-solar hydrogen coupling is proposed. In the process of integrating wind and solar power generation into the grid, the upper-level control allocates power to the hydrogen energy storage system reasonably by dispatching the power of the wind-solar power generation, and at the same time ensures that the pressure of the hydrogen storage tank is within the safe range limit, and completes the lower-level control to the inverter in the system. Duty cycle control. According to the randomness of wind and light, the hydrogen energy storage system is divided into three working conditions, namely compensation, balance, and absorption, and five working modes. Realize the wind-solar hydrogen coupling system to compensate/consume grid-connected power in a wide range. The simulation results show that the hydrogen energy storage system compensates 40% of the power shortage and 27.5% of the abandoned wind and solar energy, which effectively solves the problems of power shortage and abandoned wind and solar energy in the process of integrating wind and solar power generation into the grid. Clean energy utilization.