In order to understand in depth that Diesel/Methanol Dual Fuel (DMDF) could gain ultra-low emissions and high thermal efficiency, P-V map and φ-T map were analyzed at full load @1660 r/min. Based on the analysis of P-V map, the reasons for the increase in thermal efficiency at DMDF mode are as follows: First, the effective work of DMDF mode reduced at DMDF mode. Then, methanol evaporated in the intake manifold and cylinder will absorb large amount of heat, which will achieve waste heat recovery; Finally, the energy carried away by the exhaust gases is reduced, which is due to low exhaust temperature.
In DMDF mode, the intersection of φ-T map and NO generation region is obviously reduced, compared with the diesel mode. Meanwhile, φ-T map of DMDF mode is not covered the highest NO generation rate region. This is the reason of achieving ultra-low NOx emissions. The φ-T map of DMDF mode avoids soot generation regions at CA05 and CA50. This is the key to achieve ultra-low soot emissions.
With the continually large-scale exploitation and utilization of renewable energy, China, especially in Western China, has faced serious hydropower, wind power and solar photovoltaic (PV) power curtailment difficulties since 2011. Especially in 2016, the amount of hydropower, wind power and solar PV power curtailment peaked. This paper summarizes the reasons for renewable energy power curtailment from four aspects of energy flow, and emphatically analyses the integrated multi-energy system (IMES) solution to reduce renewable energy curtailment. Statistical results show that these countermeasures achieved success in 2017 and 2018. Then, Longyangxia hydropower-PV integrated multi-energy project is used to prove the feasibility of IMES to reduce renewable energy power curtailment. And the successful case provides reference and guidance for the promotion of IMES in other areas of the nation.
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.
Energy is a complex system affected by multiple factors, accurate energy demand forecasts provide the basis for the formulation and implementation of energy planning. This paper builds a new model and predicts China’s energy consumption. This study drew three main conclusions. First, aco-integration test and Granger causality test can help users discover the relationships between China’s energy demand and its influencing factors. Second, the improved PSO-LSSVR model showed its superiority over other models in terms of forecasting energy demand, which further improved prediction accuracy. Third, the forecasting results indicate that China’s energy demand will peak in 2034, and that the peak is 6.7 billion tonnes of coal equivalent (tce). Based on the forecasting results, the paper offers suggestions related to China’s energy development policy.
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.
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℃.
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.
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.