With many advantages, modular multilevel convert (MMC) has been extensively used in high and medium voltage power transmission projects. The thermal performance and reliability of components in MMC are key issues in system operation. However, in the current research on the reliability of MMC components, there are few methods to improve service lifetime expectancy of the components. This paper proposes a balance control algorithm, based on the cumulative fatigue damage of components, feedback to the control terminal for allocating the sub-module (SM) operating state and generating trigger pulses. Finally, the effectiveness of the proposed algorithm is verified and discussed in case studies. It is found that this algorithm is able to improve the aging degree of components in the meanwhile, the improvement in MMC reliability comes at the cost of slightly increasing capacitor voltage fluctuations and total harmonic distortion (THD). Due to the limitation of capacitor thermal performance, S... [more]

The energy consumption of an electric vehicle is primarily due to the traction subsystem and the comfort subsystem. For a regular trip, the traction energy can be relatively constant but the comfort energy has variation depending on seasonal temperatures. In order to plan the annual charging operation of an eco-campus, a simulation tool is developed for an accurate determination of the consumption of an electric vehicle throughout year. The developed model has been validated by comparison with experimental measurement of a real vehicle on a real driving cycle. Different commuting trips are analyzed over a complete year. For the considered city in France (Lille), the comfort energy consumption has an overconsumption up to 33% in winter due to heating, and only 15% in summer due to air conditioning. The urban commuting driving cycle is more affected by the comfort subsystem than extra-urban trips.

Since the beginning of the nuclear industry, graphite has been widely used as a moderator and reflector of neutrons in nuclear power reactors. Some reactors are relatively old and have already been shut down. As a result, a large amount of irradiated graphite has been generated. Although several thousand papers in the International Nuclear Information Service (INIS) database have discussed the management of radioactive waste containing graphite, knowledge of this problem is not common. The aim of the paper is to present the current status of the methods used in different countries to manage graphite-containing radioactive waste. Attention has been paid to the methods of handling spent TRISO fuel after its discharge from high-temperature gas-cooled reactors (HTGR) reactors.

Most organic dyes synthesized for dye-sensitized solar cells (DSC) use a single linker group to bind to the metal oxide photo-anode. Here we describe the synthesis and testing of two new triphenylamine dyes containing either two carboxylic acids 5-[2-(4-diphenylamino-phenyl)-vinyl]-isophthalic acid (10) or two cyanoacrylic acids (2Z, 2′Z)-3, 3′-(5-((E)-4-(diphenylamino) styryl)-1, 3-phenylene) bis (2-cyanoacrylic acid) (8) as linker groups. Full characterization data are reported for these dyes and their synthetic intermediates. DSC devices have been prepared from these new dyes either by passive or fast dyeing and the dyes have also been tested in co-sensitized DSC devices leading to a PCE (η = 5.4%) for the double cyanoacrylate linker dye (8) co-sensitized with D149. The dye:TiO2 surface interactions and dye excitations are interpreted using three modelling methods: density functional theory (at 0 K); molecular dynamics (at 298 K); time dependent density functional theory. The modell... [more]

The safety of electric vehicles (EVs) has aroused widespread concern and attention. As the core component of an EV, the power battery directly affects the performance and safety. In order to improve the safety of power batteries, the internal failure mechanism and behavior characteristics of internal short circuit (ISC) and thermal runaway (TR) in extreme cases need to be tested and studied. The safety of lithium ion batteries (LIBs) has become a research hotspot for many scholars. With unreasonable misuse or abuse of lithium ion batteries, it is easy to cause internal short circuits, resulting in thermal runaway, which poses a great threat to the safety of the whole vehicle. This comprehensive review aims to describe the research progress of safety testing methods and technologies of lithium ion batteries under conditions of mechanical, electrical, and thermal abuse, and presents existing problems and future research directions.

Analysis of natural fractures is essential for understanding the heterogeneity of basement reservoirs with carbonate rocks since natural fractures significantly control key attributes such as porosity and permeability. Based on the observations and analyses of outcrops, cores, borehole image logs, and thin sections from the Mesoproterozoic to Lower Paleozoic in the Jizhong Sub-Basin, natural fractures are found to be abundant in genetic types (tectonic, pressure-solution, and dissolution) in these reservoirs. Tectonic fractures are dominant in such reservoirs, and lithology, mechanical stratigraphy, and faults are major influencing factors for the development of fractures. Dolostones with higher dolomite content are more likely to have tectonic fractures than limestones with higher calcite content. Most tectonic fractures are developed inside mechanical units and terminate at the unit interface at nearly perpendicular or high angles. Also, where a thinner mechanical unit is observed, t... [more]

The widespread adoption of electric vehicles (EVs) has entailed the need for the parking lot operators to satisfy the charging and discharging requirements of all the EV owners during their parking duration. Meanwhile, the operational constraints of the power grids limit the amount of simultaneous charging and discharging of all EVs. This affects the EV owner’s quality of experience (QoE) and thereby reducing the quality of performance (QoP) for the parking lot operators. The QoE represents a certain percentage of the EV battery required for its next trip distance; whereas, the QoP refers to the ratio of EVs with satisfied QoE to the total number of EVs during the operational hours of the parking lot. This paper proposes a two-stage fuzzy logic inference based algorithm (TSFLIA) to schedule the charging and discharging operations of EVs in such a way that maximizes the QoP for the parking lot operators under the operational constraints of the power grid. The first stage fuzzy inference... [more]

Gradual changes in energy and mobility systems in recent decades have triggered new and significant policy challenges [...]

The subject of this paper is gains selection of an extended induction machine speed observer. A high number of gains makes manual gains selection difficult and due to nonlinear equations of the observer, well-known methods of gains selection for linear systems cannot be applied. A method based on genetic algorithms has been proposed instead. Such an approach requires multiple fitness function calls; therefore, using a quality index based on simulations makes gains selection a time-consuming process. To find a fitness function that evaluates, in a short time, quality indices based on poles placement have been proposed. As the observer is nonlinear, equations describing the observer dynamics have been linearized. The relationship between poles placement and real dynamic properties has been shown. A series of studies has been performed to investigate the influence of the operating point of the machine on the dynamics of the observer. It has been proven that rotor speed has a significant i... [more]

This paper examines the effectiveness of implementing carbon taxes to reduce carbon dioxide emissions from transport. Using the system Generalized Method of Moments estimator, we utilize cross-country analysis for the first time to study the impact of carbon taxes on the composition of petrol versus diesel passenger cars sold in 17 countries over the period 2013−2017. The results suggest that increasing carbon taxes affects consumer behavior, causing a significant shift from petrol to diesel fuel vehicles, controlling for factors such as the price of passenger cars, fuel price, interest rates, income level, population density, inflation, and vehicle stock.

In recent years, photovoltaic (PV) systems have emerged as economical solutions for irrigation systems in rural areas. However, they are characterized by low voltage output and less reliable configurations. To address this issue in this paper, a promising inverter configuration called Impedance (Z)-source inverter (ZSI) is designed and implemented to obtain high voltage output with single-stage power conversion, particularly suitable for irrigation application. An improved and efficient modulation scheme and design specifications of the network parameters are derived. Additionally, a suitable fault-tolerant strategy is developed and implemented to improve reliability and efficiency. It incorporates an additional redundant leg with an improved control strategy to facilitate the fault-tolerant operation. The proposed fault-tolerant circuit is designed to handle switch failures of the inverter modules due to the open-circuit and short-circuit faults. The relevant simulation and experiment... [more]

Wind energy has been widely used in renewable energy systems. A probabilistic prediction that can provide uncertainty information is the key to solving this problem. In this paper, a short-term direct probabilistic prediction model of wind power is proposed. First, the initial data set is preprocessed by a box plot and gray correlation analysis. Then, a generalized method is proposed to calculate the natural gradient and the improved natural gradient boosting (NGBoost) model is proposed based on this method. Finally, blending fusion is used in order to enhance the learning effect of improved NGBoost. The model is validated with the help of measured data from Dalian Tuoshan wind farm in China. The results show that under the specified confidence, compared with the single NGBoost metamodel and other short-term direct probability prediction models, the model proposed in this paper can reduce the forecast area coverage probability while ensuring a higher average width of prediction interva... [more]

Demand Response (DR) plays a vital role in a smart grid, helping consumers plan their usage patterns and optimize electricity consumption and also reduce harmonic pollution in a distribution grid without compromising on their needs. The first step of DR is the disaggregation of loads and identifying them individually. The literature suggests that this is accomplished through electric features. Present-day households are using modern power electronic-based nonlinear loads such as LED (Light Emitting Diode) lamps, electronic regulators and digital controllers to reduce the electricity consumption. Furthermore, usage of SMPS (Switched-Mode Power Supply) for computing and mobile phone chargers is increasing in every home. These nonlinear loads, while reducing electricity consumption, also introduce harmonic pollution into the distribution grid. This article presents a deterministic approach to the non-intrusive identification of load patterns using percentage Total Harmonic Distortion (THD... [more]

The potential for increased energy utilisation and reduced carbon footprint has been investigated for the industrial park Mo Industri Park (MIP), located at Mo i Rana, Norway. Process data has been gathered to quantify the energy flows between industrial clients. The energy flows have been visualised quantitatively in Sankey diagrams, while the quality of the available energy is presented in the form of a grand composite curve. High temperature flue gas from ferrosilicon (FeSi) production at Elkem Rana represent the largest heat source available for utilisation. A theoretical assessment of potential applications for this energy is presented and includes: (1) electricity production; (2) local biocarbon production, where surplus heat is utilised for drying of wood chips; (3) post combustion carbon capture, where surplus heat is utilised for solvent regeneration. The results indicate that increasing the current energy recovery from 400 GWh to >640 GWh is realistic. The increase in energy... [more]

Exploitation of renewable energy sources for power generation has been more and more important in recent years. This results from the economic issues and the measures taken to ensure the energy security. The aim of this research was to determine the significance of renewable energy sources (RES) in the energy mix of Poland, and to elicit the opinions and the level of knowledge of the society on the use and development of non-conventional energy. The article also presents advantages and disadvantages of types of RES, the obstacles which hinder the progress of green energy in Poland, and the proposed measures to expand the share of the RES in the overall energy mix. The research relied on the statistical data gathered by Statistics Poland. The opinions of respondents were elicited through a diagnostic survey based on a questionnaire. The research has demonstrated that the respondents support the development of RES in Poland. However, they also maintain that the purchase and installation... [more]

This article presents a methodology for optimizing the operation of parallel pumping stations in an open-channel water transfer system. A mathematical model was established for the minimum power with constraints on water level, flow rate and pump unit performance, and related factors. In the objective function, energy consumption of relevant equipment or facilities, such as main pump units, power transmission and transformation equipment, and auxiliary equipment, was considered comprehensively. The model was decomposed to two layers for solving. In the first layer, by using discharge distribution ratio as a variable, the flow rate and water level of the two water channels could be determined by employing the dichotomy approach (DA), and were calculated according to the principle of energy conservation, considering energy loss caused by hydraulic leakage and evaporation losses. In the second layer, the number of running pumps and the flow rate of a single pump were obtained by simulated... [more]

The paper presented the analysis of heat consumption for heating in multi-family residential buildings before and after thermal retrofitting. The analysis involved four groups of buildings, i.e., 43 buildings in total, located in various localities, belonging to one weather station. The predicted level of energy savings resulting from thermal retrofitting was achieved from the energy audits. The actual heat consumption, following the calculation into so-called external standard conditions, was obtained based on the readouts from heat-meters. For each building, the values of heat consumption over the periods of 6−10 years were read. The performance measurements involved the periods before, during, and after thermal retrofitting. The following statistical tests were used for data analysis: Wilcoxon−Mann−Whitney, Shapiro−Wilk, Bartlett, ANOVA, Kruskal−Wallis, Dunn and Holm post-hoc. The performed analyses showed that the mean value of energy savings predicted by audits reached 38.5% when... [more]

This paper presents a compensation method for unbalanced voltage through active and reactive power control by utilizing a smart inverter that improves the voltage unbalance index and detects an unbalanced state of voltage magnitude and phase, and thus enhances power quality by minimizing the voltage imbalance. First of all, this paper presents an analysis of a mathematical approach, which demonstrates that the conventional voltage unbalanced factor (VUF) using the symmetrical component cannot correctly detect the imbalanced state from index equations; and by only minimizing the VUF value, it cannot establish a balanced condition for an unbalanced state of the voltage profile. This paper further discusses that intermittent photovoltaic (PV) output power and diversified load demand lead to an unexpected voltage imbalance. Therefore, considering the complexity of unbalanced voltage conditions, a specific load and an PV profile were extracted from big data and applied to the distribution s... [more]

In rock mass disturbed by mining activity, distortions in the stress balance may lead to seismic energy being emitted in reactivated seismogenic structures. One way of increasing the imaging resolution of these seismically active structures is through relocation, which itself can be achieved using the cloud collapsing method. This method partially eliminates perturbations in the location of seismic energy sources concerning the actual positions of these sources. It enables events to be grouped into spatially ordered structures that may correspond to actual tectonic structures, such as fractures, fissures, or faults. We present the results of applying the collapsing method in mining seismology using a cloud of located events recorded during mining activity at one of the coalfaces in the Bobrek hard coal mine. The relocation procedure was applied to all the foci of events recorded during mining activity on face 3/503 between April 2009 and July 2010. In the relocated point cloud, two typ... [more]

The rapid increase in the number of online resources and academic articles has created great challenges for researchers and practitioners to efficiently grasp the status quo of building energy-related research. Rather than relying on manual inspections, advanced data analytics (such as text mining) can be used to enhance the efficiency and effectiveness in literature reviews. This article proposes a text mining-based approach for the automatic identification of major research trends in the field of building energy management. In total, 5712 articles (from 1972 to 2019) are analyzed. The word2vec model is used to optimize the latent Dirichlet allocation (LDA) results, and social networks are adopted to visualize the inter-topic relationships. The results are presented using the Gephi visualization platform. Based on inter-topic relevance and topic evolutions, in-depth analysis has been conducted to reveal research trends and hot topics in the field of building energy management. The res... [more]

Current work presents an optical setup, its calibration and reference process and the first results from single particle emissivity measurements of pulverized biomass and coal fuel particles. In contrast to earlier attempts, the setup offers the possibility of emissivity measurements during the whole particle burn-off. A laser ignites a single particle, placed in the center of the setup. Two photomultipliers observe the emitted particle radiation in the visible range (550 nm and 700 nm) for temperature calculation, using two-color pyrometry. An InSb-detector records the emitted particle radiation between 2.4 µm and 5.5 µm, which is later used to calculate particle emissivity in this range. The conclusion of multiple particle measurements lead to decreasing particle emissivity with increasing temperature. For coal particles the emissivity decreases from 0.45 at 2300 K to 0.03 at 3400 K. Biomass char shows a similar trend with a decrease from 0.18 (2100 K) to 0.03 (2900 K).

Alkaloids, typical nitrogen compounds, were found to be abundant in tobacco waste. The recovery of alkaloids from tobacco waste for biological pesticides could reduce the use of traditional chemical pesticides and avoid the pollution of farmland by the leaching of alkaloids from tobacco waste. Considering the fact that alkaloids can easily volatilize, thermal treatment is expected to be a potential technology to achieve the release and recovery of alkaloids from tobacco waste. For better understanding of conversion behavior of nitrogen-containing compounds in tobacco waste during thermal treatment, purge/trap-GC/MS (gas chromatography mass spectrometry), PY-GC/MS (pyrolysis-gas chromatography mass spectrometry), and fixed-bed/ATD-GC/MS (auto-thermal desorption gas chromatography mass spectrometry) were adopted to detect the ingredients and concentration of nitrogen-containing compounds in tobacco waste and/or volatiles. The results of purge/trap-GC/MS showed that nitrogen-containing co... [more]

To address the increased use of lighting energy in the building sector, research on the use of light shelves has been increasing. Previous studies have focused on applying operating techniques to improve daylighting performance, which reduces the economic efficiency of light shelves and the building energy savings. This study proposes the use of prism sheets to improve the performance of light shelves, a concept which was validated by evaluating the performance related to saving building energy and improving indoor light uniformity through a full-scale testbed. This study used an external light shelf with no prism sheet, a window with a prism sheet applied, and a window with both an external light shelf and prism sheet applied as Case 1, Case 2, and Case 3, respectively, and analyzed the illuminance distribution and lighting energy consumption required to maintain the optimal indoor illumination for each case. This study also derived the optimal specifications for each case to save bui... [more]

As an important part of a micro-compressed air energy storage system, the scroll expander directly affects the efficiency of the whole energy storage system. The effects of resistance on the efficiency of scroll expander caused by inlet structure and size are discussed with theory analysis and experimental methods in this paper. Micro-compressed air energy storage system has aroused widespread attention because of its pollution-free, high flexibility, in the community, remote areas power supply. Comprehensive experimental work with the selections of different size and structure of the air inlet of the scroll expander was performed with the cutting angle of air inlet chamber of the scroll expander. The results of the experiments are discussed on how exergy efficiency and inlet flow of the scroll expander were affected resulting from the cutting angles dissected. The results show that a maximum value exists for exergy efficiency of the scroll expander. Therefore, the exergy efficiency of... [more]

Solid biofuels have the potential of making a major contribution to achieving the objectives of the Paris Climate Agreement if they are used more extensively for covering the heat demand of the industry and the trade, commerce, and service (TCS) sector. To unlock this potential, a holistic analysis of the supply chain from producer to end customer was performed, involving consultants, planners, and financial institutions. The focus is on the deployment of larger biomass heating boilers (with heat loads spanning several 100 kW to several MW). The study identifies the most important barriers for expanding the use of solid biofuels for heat in the German TCS sector as well as in the industry sector. Nine sets of measures were identified for overcoming the most critical barriers, among others, by drawing on best practice approaches and solutions from other German and European contexts. Based on these measures, political recommendations were derived to shape the regulatory framework conditi... [more]