A three-dimensional (3D) fibrous structure with a high active surface and conductive pathway proved to be an excellent anode current collector for rechargeable zinc−air batteries (ZABs). Herein, a cost-effective and highly stable zinc (Zn) electrode, based on Zn electrodeposited on iron fibers (Zn/IF), is duly examined. Electrochemical characteristics of the proposed electrode are seen to compete with a conventional zinc/nickel foam (Zn/NF) electrode, implying that it can be a suitable alternative for use in ZABs. Results show that the Zn/IF electrode exhibits an almost similar trend as Zn/NF in cyclic voltammetry (CV). Moreover, by using a Zn/IF electrode, electrochemical impedance spectroscopy (EIS) demonstrates lower charge transfer resistance. In the application of a rechargeable ZAB, the fibrous Zn/IF electrode exhibits a high coulombic efficiency (CE) of 78%, close to the conventional Zn/NF (80%), with almost similar capacity and lower charge transfer resistance, after 200 charge... [more]

Photovoltaic Solar Energy (PSE) sector has sparked great interest from governments over the last decade towards diminution of world’s dependency to fossil fuels, greenhouse gas emissions reduction and global warming mitigation. Photovoltaic solar energy also holds a significant role in the transition to sustainable energy systems. These systems and their optimal exploitation require an effective supply chain management system, such as design of the network, collection, storage, or transportation of this energy resource, without disregarding a country’s certain socio-economic and political conditions. In Brazil, the adoption of photovoltaic solar energy has been motivated not only by the energy matrix diversification but also from the shortages, problems, and barriers that the Brazilian energy sector has faced, lately. However, PSE development is affected by various factors with high uncertainty, such as political, social, economic, and environmental, that include critical operational s... [more]

This study investigated the adaptations of traditional dwellings to the complex regional microclimate in southern Zhejiang, China. Typical traditional dwellings in a village in the foothills and a village on the mid-slopes of Zhejiang’s alpine region were selected to study traditional construction strategies for climate responsiveness and the comfort level of indoor environments during the very humid plum rain season in early summer. Fundamental analysis of the climate and architecture, a response analysis of the dwelling form, an occupants’ comfort satisfaction survey, and field measurements of indoor and outdoor thermal environmental parameters were performed. The traditional dwellings and their design strategies for various regional environmental factors were explored from the perspective of (1) regional climate-adaptive strategies, (2) the thermal, airflow, lighting, and acoustic qualities of the indoor environment, and (3) the occupants’ indoor environment satisfaction. The result... [more]

Monitoring of the state of charge of the thermal energy storage component in solar thermal systems for space heating and/or cooling in residential buildings is a key element from the overall system control strategy point of view. According to the literature, there is not a unique method for determining the state of charge of a thermal energy storage system that could generally be applied in any system. This contribution firstly provides a classification of the state-of-the-art of available techniques for the determination of the state of charge, and secondly, it presents an experimental analysis of different methods based on established sensor technologies, namely temperature, mass flow rates, and pressure measurements, tested using a lab-scale heat exchanger filled with a commercial phase change material for cooling applications. The results indicate that, depending on the expected accuracy and available instrumentation, each of the methods studied here can be used in the present appl... [more]

This study aimed to analyze the systematic risks of wind energy investments. Within this framework, E7 countries are included in the scope of the examination. A large literature review was carried out and 12 different systematic risk factors that could exist in wind energy investments were identified. The analysis process of the study consisted of two different stages. First, the specified risk criteria were weighted with the help of the interval type 2 (IT2) fuzzy decision-making trial and evaluation laboratory (DEMATEL) method. Second, E7 countries were ranked according to the risk management effectiveness in wind energy investments. In this process, the IT2 fuzzy Vlsekriterijumska Optimizacija I Kompromisno Resenje (VIKOR) approach was taken into consideration. The findings show that volatility in exchange rates and interest rates were the most important risks in wind energy investments. In addition, it was determined that China and Indonesia were the most successful countries in ma... [more]

To investigate the oscillation problems in power systems with modular multilevel converters (MMCs), a disturbance-state model of the MMC under P/Q control mode is established based on the harmonic state-space (HSS) method. Firstly, the basic structure of the MMC with P/Q control is presented, including the circuit structure and the controller structure. Next, the dynamic characteristics of each module in the MMC are described with the time-domain state-space model or the s-domain transfer function. The complete controller structure is considered, including the P/Q outer-loop controller, the inner-loop control, the phase-locked loop (PLL), the circulating current suppression control (CCSC) and the control delay. On the basis, the disturbance-state HSS model of the MMC and its corresponding steady-state condition are established by the HSS method. Lastly, the case studies are performed to verify the accuracy of the proposed model, based on an MMC based test system in PSCAD/EMTDC. Moreove... [more]

Developing a regional power system to achieve a high level of integration of national systems requires sufficient development of the regional transmission grid. This is possible only with appropriate schemes for the complete cost−benefit analyses, and cost allocation of these transmission investments, which plays a critical role in the selection of the most efficient network investment and the proper assignment of their cost to the national systems. Network reinforcements affect the operation of power systems and, therefore, the externalities of power generation. This paper examines the impacts of integrating local air pollution damage from power production within the benefit assessment and cost allocation of transmission investments. The paper describes the methodology followed and illustrates its application in a real-life case study where a simplified version of a European network is considered. Within this case study, we have assessed the impact of considering the reduction in air... [more]

Compared with conventional silicon (Si)-based Pulse Width Modulation (PWM) rectifiers, PWM rectifiers based on silicon carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) have significant technical advantages and broad application prospects in terms of efficiency and power density, inherited from the high-speed switching feature. However, high-speed switching also induces gate-source voltage interference, which impacts the overall character of the conversion system. This paper considered the impact of gate-source voltage interference on loss, revealing an efficiency optimization for all-SiC PWM rectifiers. Firstly, this paper theoretically investigated the mechanism of improving the conversion system efficiency by using the 4-pin Kelvin packaged SiC MOSFETs. Then, based on the industrial product case study, loss distribution, using different package styles, was quantitatively analyzed. Finally, experiment test results verified the efficiency improvement of the PW... [more]

Smart cities directly rely on a variety of elements, including water, gas, electricity, buildings, services, transportation networks, and others. Lack of properly designed transportation networks may cause different economic and safety concerns. Highway−rail grade crossings are known to be a hazardous point in the transportation network, considering a remarkable number of accidents recorded annually between highway users and trains, and even solely between highway users at highway−rail grade crossings. Hence, safety improvement at highway−rail grade crossings is a challenging issue for smart city authorities, given limitations in monetary resources. In this study, two optimization models are developed for resource allocation among highway−rail grade crossings to minimize the overall hazard and the overall hazard severity, taking into account the available budget limitations. The optimization models are solved by CPLEX to the global optimality. Moreover, some heuristic algorithms are pr... [more]

In this paper, a novel combined radiation-convection floor heating system is shown. This study uses practice-based learning and investigated the thermal performance of a combined radiation-convection floor heating system with a water heat pump system by evaluating the thermal environment and energy consumption in an experimental test. A new method that analyzed the thermal performance of four different controls was developed and applied. The results of the surface temperature distributions demonstrated that Mode 1, which uses only convection, had the lowest floor temperature and was thus considered inappropriate for occupants who sleep on the floor. By contrast, Modes 2, 3, and 4 showed high floor surface temperatures as hot water was supplied to the radiant heating panel. The predicted mean vote (PMV) results suggest that radiant floor heating is not appropriate for intermittent heating. In other words, occupants of single residences who return home at night will experience a long per... [more]

New small-scale experiments are carried out to study the effect of groundwater flow on the thermal performance of water ground heat exchangers for ground source heat pump systems. Four heat exchanger configurations are investigated; single U-tube with circular cross-section (SUC), single U-tube with an oval cross-section (SUO), single U-tube with circular cross-section and single spacer with circular cross-section (SUC + SSC) and single U-tube with an oval cross-section and single spacer with circular cross-section (SUO + SSC). The soil temperature distributions along the horizontal and vertical axis are measured and recorded simultaneously with measuring the electrical energy injected into the fluid, and the borehole wall temperature is measured as well; consequently, the borehole thermal resistance (Rb) is calculated. Moreover, two dimensional and steady-state CFD simulations are validated against the experimental measurements at the groundwater velocity of 1000 m/year with an averag... [more]

Global issues are such that we should assess and manage a variety of risks and uncertainties. Due to increasing world complexity, the development of an adequate and innovative conceptual framework, anchored in the literature, is required. This article contributes to this effort with an approach particularly relevant to decision-makers dealing with threats of different natures, limited heterogeneous information, and experts’ assessments tainted by doubts. Our approach is based on two pillars: 1) An “acuity scale”, based on the probability of the occurrence of an event, its impact and the experts’ degree of doubt; 2) A taxonomy focused on the concepts of risk, uncertainty, gamble and butterfly ambiguity. Accordingly, we present in a second step the major management implications of such approach. Global policy trends (e.g., sustainability transition) put energy sector decision-makers at the forefront of risk and uncertainty management. Consequently, we carry out a case study focused on Sw... [more]

The assessment of engineering objects in terms of energy consumption is an important part of sustainable development. Many materials, including those from the energy sector, need to undergo earlier processing, e.g., grinding. Grinding processes still demand a significant amount of energy, whereas current energy assessment methods do not take into account important parameters of the process, which makes it difficult to choose their optimal values. The study presents the analysis, testing, and assessment of mechanical engineering systems in terms of the energy consumption involved in the grinding of biomass intended for energy production purposes. A testing methodology was developed to improve the parameters of multi-disc grinding, including the reduction of energy consumption, power input, product quality improvement, and process efficiency. An original model of integrated energy consumption was developed. Tests were carried out on a five-disc grinder for five programs to assess the pro... [more]

Despite the rapid development of photovoltaic (PV) industry, direct current (DC) fault arc remains a major threat to the safety of PV system and personnel. While extensive research on DC fault arc has been conducted, little attention has been paid to the long-time interactions between the PV system and DC arc. In this paper, a simulation system with an arc model and PV system model is built to overcome the inconvenience of the fault-arc experiments and understand the mechanism of these interactions. For this purpose, the characteristics of the series DC arc in a small grid-connected PV system are first investigated under uniform irradiance. Then, by comparing with different arc models, the Habedank model is selected to simulate the fault arc and a method to determine its parameters under DC arc condition is proposed. The trends of simulated arc waveforms are consistent with the measured data, whose fitting degree in adjusted R-squared is between 0.946 and 0.956. Finally, a phenomenon o... [more]

This study investigates the thermal efficiency of a solar air heater (SAH), when it was mounted on a custom-made support frame, and was operated under different air mass flow rate. This SAH is composed of a transparent polycarbonate cover plate, a felt absorber layer, a perforated aluminium back plate and an aluminium frame. The ambient inlet air of this SAH is heated as it passes through the perforated back plate and over the felt absorber layer. The heated air is blown out through the outlet. Studies of SAHs with a similar design to this SAH were not found in the literature. The experiment was carried out at Massey University, Auckland campus, NZ (36.7° S, 174.7° E). The global horizontal solar irradiance, the ambient temperature and the wind speed were recorded using an on-site weather station. Temperature and velocity of the air at the outlet were measured using a hot wire anemometer. During the experiment, the air mass flow rate was between 0.022 ± 0.001 kg/s and 0.056 ± 0.005 kg/... [more]

The increased rates of urbanization and industrialization of the 20th and 21st centuries have dramatically changed the land use and cover of modern cities, contributing to the degradation of the urban microclimate and the rise of the ambient urban air temperatures. Given the multiple negative energy, environmental and social consequences of urban warming, the present paper summarizes the findings of previous studies, assessing the main causes of the phenomenon along with the key investigation methods involving experimental and computational approaches. There follows a description of the most common mitigations, and adaption strategies towards the attenuation of urban warming are described. The analyzed elements include the addition of green spaces such as trees, grass and green roofs; changes on the albedo of the urban surfaces and water-based techniques, as well as a combination of them. The discussion of the reported findings in the existing literature clearly reflects the impact of... [more]

Electric vehicles (EVs) have attracted growing attention in recent years. However, most existing research has not utilized actual traffic data and has not considered real psychological decision-making of owners in analyzing the charging demand. On this basis, an urban EV fast-charging demand forecasting model based on a data-driven approach and human decision-making behavior is presented in this paper. In this methodology, Didi ride-hailing order trajectory data are firstly taken as the original dataset. Through data mining and fusion technology, the regenerated data and rules of traffic operation are obtained. Then, the single EV model with driving and charging behavior parameters is established. Furthermore, a human behavior decision-making model based on Regret Theory is introduced, which comprises the utility of time consumption and charging cost to plan driving paths and recommend fast-charging stations for vehicles. The rules obtained from data mining together with established mo... [more]

Operational control strategies for the heating system of a single-family house with exhaust air heat pump and photovoltaic system and “smart” utilization of energy storage have been developed and evaluated in a simulation study. The main aim and novelty of this study is to evaluate the impact on the benefit of these advanced control strategies in terms of performance (energy use and economic) for a wide range of boundary conditions (country/climate, occupancy and appliance loads). Short-term weather data and historic price data for the same year as well as stochastic occupancy profiles that include the domestic hot water load are used as boundary for a parametric simulation study for the system modeled in detail in TRNSYS 17. Results show that the control using a forecast of dynamic electricity price leads to greater final energy savings than those due to the control using thermal storage for excess PV production in all of the examined locations except Sweden. The impact on self-consum... [more]

The prediction of electricity generation is one of the most important tasks in the management of modern energy systems. Improving the assertiveness of this prediction can support government agencies, electric companies, and power suppliers in minimizing the electricity cost to the end consumer. In this study, the problem of forecasting the energy demand in the Brazilian Interconnected Power Grid was addressed, by gathering different energy-related datasets taken from public Brazilian agencies into a unified and open database, used to tune three machine learning models. In contrast to several works in the Brazilian context, which provide only annual/monthly load estimations, the learning approaches Random Forest, Gradient Boosting, and Support Vector Machines were trained and optimized as new ensemble-based predictors with parameter tuning to reach accurate daily/monthly forecasts. Moreover, a detailed and in-depth exploration of energy-related data as obtained from the Brazilian power... [more]

Hydraulic fracturing has been widely used in recent years as a key technology to improve energy mining efficiency in petroleum and geothermal industries. Laboratory hydraulic fracturing experiments recently were completed in six large-scale 300 × 300 × 300 mm rock specimens to better understand this complex process of hydraulic fracturing. When injection flow rate increases from 5 to 30 mL/min. The fracture initiation pressures and breakdown pressures increase, the propagation times and post-fracturing pressures decrease. The fracture geometries are observed and analyzed, mean injection power is proposed and results show that it could be used to roughly estimate the fracture total lengths. Moreover, the fracture permeabilities based on the pressure data are calculated and linearly ascend with the increase of injection flow rates. These results can provide some reasonable advice for implementing hydraulic fracturing reservoir simulations and improving energy production efficiency on app... [more]

In this paper, a co-estimation scheme of the state of charge (SOC) and available capacity is proposed for lithium−ion batteries based on the adaptive model-based algorithm. A three-dimensional response surface (TDRS) in terms of the open circuit voltage, the SOC and the available capacity in the scope of whole lifespan, is constructed to describe the capacity attenuation, and the battery available capacity is identified by a genetic algorithm (GA), together with the parameters related to SOC. The square root cubature Kalman filter (SRCKF) is employed to estimate the SOC with the consideration of capacity degradation. The experimental results demonstrate the effectiveness and feasibility of the co-estimation scheme.

The field of computational fluid dynamics has been rekindled by recent researchers to unleash this powerful tool to predict the ejector design, as well as to analyse and improve its performance. In this paper, CFD simulation was conducted to model a 2-D axisymmetric supersonic ejector using NIST real gas model integrated in ANSYS Fluent to probe the physical insight and consistent with accurate solutions. HFOs (1234ze(E) and 1234yf) were used as working fluids for their promising alternatives, low global warming potential (GWP), and adhering to EU Council regulations. The impact of different operating conditions, performance maps, and the Pareto frontier performance approach were investigated. The expansion ratio of both refrigerants has been accomplished in linear relationship using their critical compression ratio within ±0.30% accuracy. The results show that R1234yf achieved reasonably better overall performance than R1234ze(E). Generally, by increasing the primary flow inlet satura... [more]

One way of handling short-time short-circuits without causing equipment failure is the management of the reclose function integrated into smart switchboard which is described in this article. Due to the cost of the application, the optimal placement of such equipment must be well-planned. During the planning of the placement optimization of a low-voltage electricity network quality, the increase of the consumer supply security must be considered along with the best economic utilization. The research presented in this article aims to introduce a new special decision support methodology calculated with these variables. The management of smart switchboard (SSB) tool installation into low voltage (LV) network was investigated. The selection of the placement nodes is based on the complex investigation of the network characteristics. Investigation is performed by empiric analysis. This method can support the power companies to make the optimal decision. The presented new device can have outs... [more]

This paper aims to investigate the time-varying influences of major crude oil-producing countries on Brent oil prices, with seven-panel data over the observation years of 1998 to 2018. We create seven panels with 36 monthly data for each and estimate the contributions of individual producing countries to oil price changes with a multivariate regression technique of ordinary least squares. Most existing researches have focused on identifying relationships among oil price, market fundamental factors, macroeconomic variables, and geopolitical events in broad perspectives. However, this paper undertakes a longitude/panel analysis of nine oil producers’ influences, with the Organisation for Economic Co-operation and Development (OECD) consumption and the U.S. Dollar Index (USDX) on oil prices in each panel and intends to identify which producers have statistically significant influencing weights on oil prices. We believe that this research contributes to the body of knowledge in better unde... [more]

Active power filters (APFs) are dynamic power electronic devices that suppress harmonics and reactive power. To simplify the detection and extraction of traditional APF harmonics and reactive current, this paper proposes a direct source current control based on a three-phase three-wire shunt APF. The compensation principle and control method of the source current are analyzed systematically. The currents can be controlled without static errors by a proportional-integral (PI) controller in d-q rotating coordinates. Therefore, the compensation accuracy and dynamic performance of the system can be improved by the control strategy. Moreover, considering the grid voltage fluctuations, a droop regulator is proposed to address the impact of DC-link voltages on APF power losses and compensation performance. The regulator is combined with a traditional voltage outer loop PI control to achieve a comprehensive optimization between the power loss and compensation performance of the APF system. Fin... [more]