Considered as promising candidates of composing eutectic chloride molten salts for high temperature energy storage and transfer, NaCl-KCl-CaCl2 and NaCl-CaCl2 systems are formulated into proper to satisfy the property requirement for heat storage and transfer. The thermal properties of the eutectic molten salts liquid such as melting points, specific heat capacity, density, viscosity and thermal stability were measured by DSC, Archimedes, rotation and mass loss curves under isothermal conditions methods. The results shown out, with appropriate operating temperature, lager heat capacity, acceptable viscosity and good thermal stability, NaCl-KCl-CaCl2 and NaCl-CaCl2 systems are the excellent high temperature heat storage and transfer materials under 850℃.
Large-scale centralized charging of electric vehicles is likely to cause congestion phenomena such as line overload and voltage drop. A scheduling optimization scheduling strategy for distribution network congestion management considering electric vehicles charging load is proposed. Establish a multi-objective optimization model of three stakeholders including grid center, electric vehicle aggregator and electric vehicle user, and design the objective function according to their actual operating conditions. The non-dominated sorting genetic algorithm-II (NSGA-II) is used to solve the Pareto non-dominated solution set, and the Topsis method is used to determine the optimal solution. The case analysis part of the article proves that the proposed strategy can eliminate congestion by comparing the response results before and after optimization. The cost-benefit analysis proves that the strategy can reduce the running cost and increase the profit to some extent.
Large-scale wind farm has become an important factor affecting the transient stability of power system. In view of the lack of theoretical research on the transient power angle stability of multi-machine system connected with wind farm, this paper proposes a method to analyze the transient power angle stability of multi-machine system with doubly-fed induction generator (DFIG) based wind farm. By modifying and contracting the bus voltage matrix, thus the influence of wind farm on the mutual synchronization between synchronous generators is quantified to the variation of electrical distance between synchronous generators. Furtherly, according to the extended equal area criteria, the relation between the equivalent mechanical power of the system and wind farm’s power output or access position is derived, and finally the influence regularity of wind farm access location on transient stability of practical multi-machine power system is revealed, which provides a theoretical guidance for the scientific configuration of wind farm considering the LVRT scheme and access location synthetically. In simulation, the variation of electrical distances between synchronous generator nodes caused by different DFIG location is analyzed, and the power angle variation in the cases of two LVRT schemes of DFIG at different grid connection point are simulated and compared to verify the validity of proposed method.
Sustainable urban energy system is an important support and driving force for the high-quality development of urban economy and society. In the context of addressing climate change and energy transformation, this paper summarizes the stylized facts of urban and energy system evolution. A sustainable urban energy system analysis framework is proposed to analyze the logical framework of the energy system from the physical, information, and value layers. Further, this paper proposes a comprehensive indicator system for quantitatively evaluating the degree of coordination between urban development and energy systems, and provides a method for assessing the comprehensive benefits of sustainable urban energy systems.
In the context of a high proportion of renewable energy and multi-energy load access to energy system, the stochastic characteristics of energy supply side and load side need to be considered. In this paper, a district integrated heat and power system (DIHPS) model including wind turbine, photovoltaic, CHP, HP and gas boiler is established. Based on the chance-constrained programming model of DIHPS, this paper studies the changes of electric power and mass flow of energy network in DIHPS under stochastic conditions, and the changes of expansion schemes when energy stations connected. The results show that considering the randomness of energy supply side and load side, the expansion cost of power lines and thermal pipelines can be effectively reduced.
The air of high humidity and high sea spray aerosol (SSA) on islands or costal area always leads to the serious equipment corrosion and affects the living comfort of residents. Conventionally, the dehumidification and SSA reduction processes are separated and always consume precious electricity power and expendable materials. To simplified the procedure and reduce the energy consumption, this paper proposed a novel liquid‐ desiccant dehumidification system combined with sea spray aerosol removal. Based on the characteristics of liquid‐desiccant dehumidification and phase transitions of the ternary solution system, the combined system can be driven by the waste heat source of 70 oC. The proposed system was simulated by the thermodynamic equilibrium model and the optimization of design parameter are presented. The results showed that the humidity ratio of the supply air can be reduced by 8.24 g/kg(dry air). The COP of this novel system is around 0.446 and its exergy efficiency can reach 12.96%. Besides, the crystallization experiment is conducted to verify the feasibility of the NaCl separation process. This study provides a new method to simultaneously remove moisture and sea spray aerosol by using low‐ temperature waste heat.