ALBERT

Description: Spent carbon anode (SCA) is a dangerous solid waste that is continuously discharged from the aluminum electrolysis industry and has a large number of valuable resources and a high risk of environmental pollution. Its safe disposal and resource utilization have become a resource and environmental problem that must be solved urgently. Current methods for SCA disposal include flotation, vacuum metallurgy, physical activation, roasting, bubbling fluidized bed combustion, alkali fusion, alkali leaching, and chemical leaching combined with high temperature graphitization. In this paper, the material composition, resource properties, and environmental risks of SCA are discussed. Working principle, treatment process, advantages and disadvantages of the above methods are also briefly described and compared. Results showed that flotation is the safest disposal and comprehensive utilization technology that is suitable for characteristics of SCA raw materials and has the most large-scale application potential. In addition, characteristics of SCA recovery products are correlated to the recycling of aluminum reduction cells. This technology can alleviate the shortage of high-quality petroleum coke resources in China’s carbon material industry and the high cost of raw materials in aluminum electrolysis industry.

Description: The time and annealing temperature for the film crystallization in perovskite solar cells (PSCs) is critical and is at the stake of device optimization. It governs the crystallization process, the film’s morphorlogy and texture and the level of non-radiative defects, which in whole control the power conversion efficiency (PCE). However, deciphering each of these parameters in the device cell characteristics remains not totally clear. In this work, we led a holistic study considering temperature and time for the MAPbI3 crystallization as a free parameter to study how the latter is impacting on the film’s characteristics and how the device figure of merit is affected. The results suggest that the crystallinity level of the grains plays an important role in the photo-current value whereas the morphology and PbI2 impurities resulting from the onset of thermal decomposition of MAPbI3 penalizes the cell photovoltage and the fill factor values. Based on this study, it is highlighted that flash high temperature annealing is beneficial to limit out-of-plane substrate grain boundaries, resulting in a device exhibiting 18.8% power conversion efficiency compared to 18.0% when more standard post-annealing procedure is employed.

Description: Small-scale natural gas liquefaction processes have several clear advantages, particularly in the exploitation of ‘unconventional’ natural gas (NG) from sources such as difficult-to-access and offshore gas fields. Moreover, conventional liquefaction processes have a number of disadvantages such as high energy consumption, large cooling loads required in the refrigeration cycle, and non-uniform matching of cold and hot flows in liquified natural gas (LNG) heat exchanger (HE). The main objective of this study was to optimize the most commonly used mixed refrigerant process. The liquefaction performance of the optimized process was analyzed and the influence of gas parameters on the power consumption, exergy loss, freezing mixture circulation, and cooling water load were investigated. The results show that compressor power consumption can be reduced by 29.8%, the cooling water load can be reduced by 21.3%, and the system exergy efficiency can be increased by 41% with the optimized process. Furthermore, throttling and compression of the freezing mixture were increased during the refrigeration stage. It can be concluded that reducing the feed gas temperature and increasing the feed gas pressure can reduce the total power consumption, exergy loss, freezing mixture circulation, and cooling water load, which can significantly improve liquefaction performance.

Description: In the process of continuously advancing urbanization, the energy efficiency of the construction industry, as a pillar industry of the national economy, has attracted much attention. The imbalance of regional economic development, the difference of regional resource endowment, and the incomplete energy infrastructure in some areas lead to the prominent problem of energy poverty in China. Based on the panel data of 30 provinces and cities from 2008 to 2017, this paper calculates the energy poverty index and the energy efficiency of the construction industry. Using OLS, Tobit, Probit, and other estimation methods, this paper analyzes the internal relationship between energy poverty and the energy efficiency of the construction industry, the mediating role of energy consumption structure, and the moderating effect of technological level and marketization degree. The results show the following: There is a negative correlation between energy poverty and the energy efficiency of the construction industry (Husnain, ENERG POLICY, 2021, 157). The energy consumption structure plays a partial mediating role in the impact of energy poverty on the energy efficiency of the construction industry (Li, CHEM ENG J, 2021, 408). It means that energy poverty inhibits the optimization of the energy consumption structure, and through this process, it also inhibits the improvement of the energy efficiency of the construction industry. The technological level and the degree of marketization play a moderating role in the main effect, which can weaken and strengthen the negative impact of energy poverty on the energy efficiency of the construction industry (Gajdzik, ENERGIES, 2021, 14).

Description: In this paper, a numerical model based on the mass flow rate of seal leakage is presented, and a 3D numerical method of a multistage axial compressor with good engineering practicability is established. Validation consists of modeling a nine-stage axial compressor in all operating rotation speeds and calculating results of the performance characteristic curves in good agreement with test data. Comparisons are made against different cases of seal leakage mass flow rate for analyzing the impact of increasing seal leakage on the aerodynamic performance of the multistage axial compressor. The results indicate that the performance of the nine-stage axial compressor is degenerated faster and faster with seal leakage increasing in all operating working points, and the degeneration of performance of this compressor can be evaluated by the relationships of main performance parameters with the mass flow rate of seal leakage. Comparisons of flow distribution in the compressor for different cases of seal leakage also show that stators located in front stages of the multistage axial compressor are affected more seriously by the increasing seal leakage, and it can be confirmed that relatively larger flow losses in front stages bring significant impact on the decay of aerodynamic performance of a multistage axial compressor.

Description: Electrification of transportation using electric vehicles has a large potential to reduce transport related emissions but could potentially cause issues in generation and distribution of electricity. This study uses GPS measured driving patterns from conventional gasoline and diesel cars in western Sweden and Seattle, United States, to estimate and analyze expected charging coincidence assuming these driving patterns were the same for electric vehicles. The results show that the electric vehicle charging power demand in western Sweden and Seattle is 50–183% higher compared to studies that were relying on national household travel surveys in Sweden and United States. The after-coincidence charging power demand from GPS measured driving behavior converges at 1.8 kW or lower for Sweden and at 2.1 kW or lower for the United States The results show that nominal charging power has the largest impact on after-coincidence charging power demand, followed by the vehicle’s electricity consumption and lastly the charging location. We also find that the reduction in charging demand, when charging is moved in time, is largest for few vehicles and reduces as the number of vehicles increase. Our results are important when analyzing the impact from large scale introduction of electric vehicles on electricity distribution and generation.

Description: The trip probability of transmission line under lightning stroke is rapidly increasing under complex weather conditions when large-scale renewable energy is intergrated with modern power grid. Line arrester plays a critical role in reducing lightning damage and economic losses, in which DC reference voltage is a critical parameter to evaluate line arresters. Hence, a set of on-site DC test system of transmission line arresters is developed to realize the DC reference voltage test in this article. The output DC voltage of the test system is continuously adjustable (0–200 kV), while its rated power and the maximum output current are set to 400 W and 2 mA, respectively. Furthermore, the system is powered by a lithium battery instead of a 220/380 V AC energy source. It employs split design and integrating assembly on-site that reduces the total weight by 36.7%, which considerably decreases the demand for the space of test site. Besides, the weights of control cabinet, multiplying cylinder, and energy source are reduced by 60, 54.55, and 33.33%, respectively. Meanwhile, the Bluetooth remote control module is used to effectively ensure the safety of test personnel. This system accomplishes DC reference voltage tests without removing line arresters on site, which can effectively enhance maintenance efficiency and economic benefits.

Description: In order to deeply explore the transient stability mechanism of the AC/DC hybrid system, this paper analyzes the rotor angle stability of the two-area AC/DC hybrid system. The system is analyzed after subjecting it to large disturbances in the AC system and for different operating conditions, qualitatively and quantitatively. The influence of factors, such as the AC operating point of the system and the proportion of DC transmission power, have been considered for improving the rotor motion equation. Subsequently, the transient characteristics of the hybrid system are analyzed after being subjected to disturbances. The power angle stability margin index is obtained, based on which the transient characteristics after DC blocking are analyzed, and the coordinated control strategy with the least control cost is proposed. The results are verified using the two-area AC/DC parallel transmission system network model. The study provides the reference for ensuring the security and stability of the hybrid AC/DC power grid.

Description: The intending island service restoration method is one of the core technologies of self-healing control for smart distribution systems, which aims to maximize the restoration of the out-of-service loads in the out-of-service area without faults quickly. For this reason, a topology-weighted directional traversal intending island recovery method considering the uncertainty of distributed generation sources is proposed. First, divide the network level of the power-loss feeder and calculate the interval power flow of the feeder before the fault, and obtain the power flow direction when the active and reactive power of the faulted branch is the smallest so as to determine whether the distributed generation supply in the non-faulty power-loss area can restore all load power supply. If not, to determine the island recovery plan, continue to compare the distributed generation supply and the load capacity at all levels, and give priority to recovering loads with higher importance levels and smaller network levels. The traversal of the topological authority and direction effectively reduces the island recovery time and can make full use of the distributed generation output to maximize the recovery of the non-faulty power-loss area. Taking the PG&E 69-node system as an example and using the BFGS trust region algorithm to calculate the island power flow without unbalanced nodes for verification, the results show that this method consumes less time and can restore more load power supply than the existing island recovery method, which verifies the method’s effectiveness and reasonability.