Applied Mechanics and Materials Vols. 448-453

Abstract: This paper designs a grouping energy management strategy to reduce the influence of wind power fluctuations on the power system. To improve operational technicality and economy of energy storage stations, this paper designs a grouping energy management strategy with SOC correction. According to physical constrains of battery energy storage systems, technical and economic evaluation index of energy storage stations are established. Reasonable limit bands to an energy storage station installed 5MW×2h can balance the output power of a wind farm installed 49.3MW achieved through example analysis. Then the energy management strategy designed is proved to be able to control the change range of the battery SOC and distribute control tasks efficaciously, improving operational technicality and economy of the station effectively. This research provides a theoretical reference to design of energy management strategies for energy storage stations installed small at wind farms.

Abstract: During long-time charge-discharge cycling, the capacity of the vanadium redox flow battery (VRFB) will reduce gradually. To recognize the capacity loss condition in the time of the operation process, a method for classification of the capacity loss degree based on Probabilistic Neural Network (PNN) is presented. The network inputs are the value of the voltage per second and the average power of the cell stack in any two minutes of the circulation. The network will give out three classes in form of three numbers to classify the capacity loss degree into different levels. The network is trained and validated by experimental data and the results show that the network is suitable for the classification problem of VRFB capacity loss and the method is useful to determine whether the capacity is sufficient and when to restore the cell capacity in real time.

Abstract: This paper proposes a new power electronic transformer (PET) to be used for distribution system, which is composed of the three-stage power circuits. The input stage uses Modular Multilevel Converter (MMC) to reduce the voltage stress rating of components, meanwhile, the harmonic components in the current will be deduced significantly, to make DC capacitor voltage of MMC rectifier balance, a control method is proposed. The isolation stage use a middle-frequency transformer to realize voltage conversion and isolation of the low-voltage side from the high-voltage side. In the third-stage, a inverter outputs the desired voltage and power to the load. The simulation results are presented to show the validity of the proposed PET system.

Abstract: LNG can provide plenty of cold energy when it is used as the fuel. The cold energy can be recovered and utilized in vehicle refrigeration. The basic principles of LNG refrigerated truck and the design of cold recovery system were described. In order to research the cooling performance of LNG refrigerated truck, a simulation model was established. The effects of the glycol inlet temperature, the glycol and natural gas flow rates, wind speed and the system pressure on the cooling capacity and air outlet temperature were analyzed. The results show that ethylene glycol flow is an important factor on system performance and LNG cold energy recovery is suitable for the refrigerated truck.

Abstract: The effect of air volume supplied by top mechanical ventilation on multi-span greenhouse temperature field is studied with different ambient temperatures through CFD numerical simulation. The cooling effects of different mechanical ventilation volumes are compared in the same ambient temperature conditions such as summer calm and high illumination. Thus, the best supply air volume is found to provide a theoretical support for mounting ventilator at multi-span greenhouse top for cooling. Results show that a smaller mechanical ventilation volume can meet the cooling requirements when temperature is lower outside greenhouse. However, single mechanical ventilation has been unable to meet the cooling requirement when ambient temperature is too high outside greenhouse.

Abstract: Focus on the unfavorable effects of initial operation to the performance of ground heat exchangers, a three-dimensional CFD simulation of full-scale ground heat exchanger under dynamic load was established to investigate the heat transfer performance of a 120-meter vertical U-Tube ground heat exchanger under different initial operating time. The results show that initial operation has influence on the performance of ground heat exchangers.

Abstract: The flywheel energy storage technology is a kind of method that converts electrical energy into kinetic energy in store. The flywheel energy storage system (FESS) is usually used for renewable energy system such as wind turbine generator system (WTGS) to adjust the quality of output power. Droop control is a kind of control technology to regulate the active power and reactive power in micro-grid. In this paper, we introduced a method to combine the droop control with FESS and designed the control topology. The droop control method was applied to control the part of inverter in FESS. By controlling the output frequency and the voltage amplitude of WTGS-FESS system, we can regulate the output of the inverter as a promotion in smoother active power and reactive power.

Abstract: The article makes analysis of the latest research situation and development tendency of several typical enhanced heat transfer tubes, such as spirally corrugated tube, transversely-ridged tube, corrugated tube and converging-diverging tube, as well as comparing their enhanced diathermancy respectively. Therefore, the author’s research will have positive effect on energy utilization efficiency.

Abstract: Applications of non-thermal plasma in methane catalysis combustion have attracted a lot of attentions in recent years due to its outstanding and unique properties. We summarized two kinds of hybrid systems of plasma and catalysts for methane combustion reaction and compared these two figurations. Results prove that combining non-thermal plasma and catalysts has an excellent performance for methane total oxidation compared with single ones.

Abstract: Catalytic combustion technology can effectively reduce the temperature of the combustion reaction and significantly inhibit the formation of NOx. Perovskites catalyst materials have high stability, varied chemical composition, and low cost etc. A combination of catalytic combustion technology and perovskite catalyst materials has great significance for energy industry and environment protection. However, improving lower temperature catalytic activity and high temperature thermostability performance of perovskite catalyst is still major problem. Some researchers have improved the activity and stability of perovskite catalysts for methane combustion by different preparation methods. The structure and preparation methods of perovskite-type oxide catalysts are presented.