Economic dispatch optimization and power management are the main concerns for a microgrid (MG). They are always studied and are considered to achieve an efficient operation of the MG by simplifying the control process and decreasing losses. The integration of a small-scale wind turbine (SSWD) into a direct current (DC) MG has an impact on its power and energy management. Excess power produced by renewable energy sources (RESs) is one of the problems that face the reliability of the MG and should be resolved. For this reason, a supervisory system is suggested to manage the excess of power. During the supervision process, some criteria, such as the physical limits and tariffs of the components are taken into account. Then, the suggested power management strategy aims to achieve an instantaneous power balance considering a rule-based power and depends on the above-mentioned criteria. To better meet the power balance, it is necessary to explore the constraints related to the control and su... [more]

This article focuses on developing both statistical and machine learning approaches for forecasting hourly electricity demand in Ontario. The novelties of this study include (i) identifying essential factors that have a significant effect on electricity consumption, (ii) the execution of a Bayesian optimization algorithm (BOA) to optimize the model hyperparameters, (iii) hybridizing the BOA with the seasonal autoregressive integrated moving average with exogenous inputs (SARIMAX) and nonlinear autoregressive networks with exogenous input (NARX) for modeling separately short-term electricity demand for the first time, (iv) comparing the model’s performance using several performance indicators and computing efficiency, and (v) validation of the model performance using unseen data. Six features (viz., snow depth, cloud cover, precipitation, temperature, irradiance toa, and irradiance surface) were found to be significant. The Mean Absolute Percentage Error (MAPE) of five consecutive weekd... [more]

To reduce the device number per unit level of the existing nine-level inverters, a topology of single-phase transformerless nine-level inverter was proposed. The proposed topology consists of only 10 switching devices and 4 capacitors. Firstly, the working principle of the proposed topology was analyzed in detail, and the comparison with conventional nine-level topologies in terms of device switching loss and conduction loss was presented. Then, combined with one-dimensional space vector modulation, a floating capacitor voltage estimation method was presented by the analysis of the operation mode before the arrival of redundant switching state. On this basis, a floating capacitor voltage sensorless control scheme was proposed, to achieve the balance of the floating capacitor voltages. Finally, simulations and experiments verified the effectiveness and correctness of the proposed topology and floating capacitor voltage sensorless control method.

Gallium nitride high-electron-mobility transistor (GaN HEMT) is a key enabling technology for obtaining high-efficient and compact power electronic systems. At the design stage of a power converter, the proper modelling of the GaN HEMT is essential to benefit from their good features and to account for the limits of the current technology. Circuit models of power MOSFETs have been deeply investigated by academia and industry for a long time. These models are able to emulate the datasheet information, and they are usually provided by device manufacturers as netlists that can be simulated in any kind of SPICE-like software. This paper firstly highlights the similarities and differences between MOSFETs and GaN HEMTs at the datasheet level. According to this analysis, the features of MOSFET circuit models that can be adopted for GaN HEMT modelling are discussed. This task has been accomplished by overviewing the literature on MOSFETs circuit models as well as analysing manufacturers netlis... [more]

In recent years, efficient modeling and forecasting of electricity prices became highly important for all the market participants for developing bidding strategies and making investment decisions. However, as electricity prices exhibit specific features, such as periods of high volatility, seasonal patterns, calendar effects, nonlinearity, etc., their accurate forecasting is challenging. This study proposes a functional forecasting method for the accurate forecasting of electricity prices. A functional autoregressive model of order P is suggested for short-term price forecasting in the electricity markets. The applicability of the model is improved with the help of functional final prediction error (FFPE), through which the model dimensionality and lag structure were selected automatically. An application of the suggested algorithm was evaluated on the Italian electricity market (IPEX). The out-of-sample forecasted results indicate that the proposed method performs relatively better th... [more]

This study analyzes the household energy needs of the indigenous community of San Francisco Pichátaro, Michoacán, Mexico, and the use of Pinus spp. wood residues for the production of briquettes. The energy and emission performances of wood briquettes were evaluated on the field and in the laboratory. On-field surveys and measurements show that most users combine the use of fuelwood and LPG for cooking and heating water, and 65% of people use fuelwood daily (40% of houses consumed more than 39 kg per week). The use of biomass waste is an energy option in rural communities and contributes to reducing firewood consumption and mitigating GHGs. Briquettes gasification to heat water reduces 74% of GHG emissions, increases the thermal efficiency by 30%, and reduces pollutant emissions of CO, CH4, and PM2.5, NMHC, EC, and OC by 50% to 75% compared to a three-stone fire. The use of briquettes on the Patsari stove showed energy savings of 12% and a 36% reduction in CO2e compared to the “U” type... [more]

This article concerns the method of material consumption assessment of the cylinder-piston group of diesel engines in the biodiesel environment. The obtained experimental dependences of the wear coefficients on the example of the tribounit cylinder liner and the piston ring can be used to forecast the resource use during operation under specific conditions of the engine and the environment as a whole. The article systematizes the types of biofuels, depending on the type of raw materials from which they were made, taking into account the process and application. The physical and chemical aspects of the catalysts used for biofuels were indicated. The applied experimental methods for tribological wear of the piston-cylinder pair were analyzed. B70 biodiesel was used in the research, i.e., 70% mineral diesel oil and 30% methyl esters of rapeseed oil. Experimental tribotechnical studies of the influence of biofuels on the behavior of various materials have shown that when using this type of... [more]

The Tuscaloosa Marine Shale (TMS) is a versatile Late Cretaceous shale formation present in central and SE Louisiana and SW Mississippi, which drew attention because of the various roles played within the Tuscaloosa Group. In this paper, it is debated whether the Tuscaloosa Marine Shale can act as a source, reservoir, or seal all throughout the shale play or only in certain areas. Well log and core data from Adams County, Mississippi, are compared to data from East Feliciana Parish in Louisiana. Conclusions were drawn based on the results of well log analysis, X-ray Diffraction (XRD), porosity−permeability measurements, programmed pyrolysis, and fracture analysis. It was shown that the Tuscaloosa Marine Shale interval in SE Louisiana consists of important amounts of calcite, exhibits multiple natural fractures, has porosity values as high as 9.3%, and shows a TOC content of up to 2.8 wt%. On the other hand, samples from a well at the Cranfield field, MS, are characterized by considerab... [more]

Electrochemical impedance spectroscopy (EIS) can provide information about the internal state of fuel cells, which makes EIS an important tool for fuel cell fault diagnosis. However, high cost, large volume, and poor scalability are limitations of existing EIS measurement equipment. In this study, a multi-channel online fuel cell EIS measurement device was designed. In this device, based on multi-phase interleaved Boost topology and average current control, an excitation source, which can output 1~500 Hz, 10 A sinusoidal excitation current was designed and verified by model simulation. Then, based on the quadrature vector digital lock-in amplifier (DLIA) algorithm, an impedance measuring module that can achieve precise online impedance measurement and calculation was designed. A prototype was then built for the experiment. According to the experiment test, the amplitude error of the excitation source is less than 1.8%, and the frequency error is less than 0.3%. Compared with the refere... [more]

To move the world toward a more sustainable energy future, it is crucial to use the limited hydrocarbon geological resources efficiently and to develop technologies that facilitate this. More rational management of petroleum reservoirs and underground gas storage can be obtained by optimizing well control. This paper presents a novel approach to optimal well control based on the combination of optimal control theory, innovative artificial intelligence methods, and numerical reservoir simulations. In the developed algorithm, well control is based on an auto-adaptive parameterized decision tree. Its parameters are optimized by state-of-the-art machine learning, which uses previous results to determine favorable parameters. During optimization, a numerical reservoir simulator is applied to compute the objective function. The developed solution enables full automation of the wells for optimal control. An exemplary application of the developed solution to optimize underground storage of gas... [more]

The construction sector generates large amounts of heterogeneous and dynamic data characterized by their fragmentation throughout the life cycle of a project. Immediate and accurate access to that data is fundamental to the management, decision-making and analysis by construction owners, supervisors, managers, and technicians involved in the different phases of the project life cycle. However, since construction project data are diverse, dispersed, uncorrelated, and difficult to visualize, a reliable basis for decision-making can rarely be established by the management team. Aiming to bridge this gap, a methodology for data management during building construction by means of Data with BIM and Business Intelligence (BI) analysis tools was developed in this study. This methodology works by extracting data from 3D parametric model and integrating it with a BI tool, through which data are visualized and interrelated with the same database, the BIM model. To demonstrate the applicability of... [more]

This paper aims to simulate and evaluate the impacts of increases and decreases in oil price on industrial sectors in China. We develop an oil-economy computable general equilibrium (OE-CGE) model with crude oil as an important factor in production. The transmission mechanism of crude oil price swings to various industrial sectors is described in the model. We calibrate parameters in the model parameters using input-output data. In addition, we simulate the rise and fall of oil prices in the model and assess the impact of crude oil prices on various industrial sectors. The results show that crude oil price changes have the greatest impact on the output and consumption of crude oil and gas extraction products sector, crude oil refined coke products, and processed nuclear fuel products sector. The investment of public utilities sector is the most sensitive to changes in crude oil price. When the price of crude oil changes, its investment drops significantly. Crude oil price stability is... [more]

Due to the inflexibility of cogeneration power plants and the uncertainty of wind power production, the excess power of the distribution network brings challenges to the power grid operation. This paper introduced an improved moth-flame optimization algorithm to meet the challenge of energy complementary dispatching. The proposed algorithm adopts three effective strategies, namely inertia weight, unified initialization, and the spiral position update strategy, which maintains a strong global search ability and a potent compromise between global and local search. The effectiveness of the proposed method was evaluated by benchmark functions. Furthermore, the proposed method was applied to combine heat and power system operation problems and economic dispatch in light load and wind power unpredictability. In order to verify the robustness of the algorithm and solve the complex constraints of power systems under extreme conditions, three different cases had been discussed. The experimental... [more]

The prediction of charging point occupancy enables electric vehicle users to better plan their charging processes and thus promotes the acceptance of electromobility. The study uses Adaptive Charging Network data to investigate a public and a workplace site for predicting individual charging station occupancy as well as overall site occupancy. Predicting individual charging point occupancy is formulated as a classification problem, while predicting total occupancy is formulated as a regression problem. The effects of different feature sets on the predictions are investigated, as well as whether a model trained on data of all charging points per site performs better than one trained on the data of a specific charging point. Reviewed studies so far, however, have failed to compare these two approaches to benchmarks, to use more than one algorithm, or to consider more than one site. Therefore, the following supervised machine-learning algorithms were applied for both tasks: linear and log... [more]

Background. Laws that enable a circular economy (CE) are being enacted globally, but reliable standardized and digitized CE data about products is scarce, and many CE platforms have differing exclusive formats. In response to these challenges, the Ministry of The Economy of Luxembourg launched the Circularity Dataset Standardization Initiative to develop a globalized open-source industry standard to allow the exchange of standardized data throughout the supply cycle, based on these objectives: (a) Provide basic product circularity data about products. (b) Improve circularity data sharing efficiency. (c) Encourage improved product circularity performance. A policy objective was to have the International Organization for Standardization (ISO) voted to create a working group. Methods. A state-of-play analysis was performed concurrently with consultations with industry, auditors, data experts, and data aggregation platforms. Results. Problem statements were generated. Based on those, a sol... [more]

Electrical insulation is an integral part of power components. The aging of electrical insulation is an undeniable fact that limits the operational lifetime of power components. Apart from regular aging, abnormal stresses and the development of defects are real threats because of their contribution in accelerating the aging rate and thereby leading to a premature failure of the power components. Over the decades, various studies have been carried out to understand the aging behavior of electrical insulation mainly considering electrical and thermal stresses. Similarly, a number of mathematical (aging) models have been developed based on the theoretical and experimental investigations and evidences. However, a dependable formulation of the models that can provide more practical estimation of the insulation degradation profile has not been achieved yet. This paper presents a comprehensive review of the aging models considering single and multistress conditions. Further, the paper discuss... [more]

The effects of biochar on different horticultural crops (lettuce, tomato, sweet pepper, and radish) were evaluated in the Mediterranean climate. Biochar was produced by pyrolysis of Pinus pinaster wood chips at 550 °C and used at 1 (B1) and 2 (B2) kg/m2 application rates on six 3.5 m2 plots in each treatment, with two control plots (B0). No fertilizer was used. Treatment B1 led to a significant increase (p < 0.01) of 35.4%, 98.1%, 28.4%, and 35.2% in the mean fresh weight of radishes, lettuce, tomatoes, and sweet peppers, respectively. Treatment B2 resulted in an improvement of 70.7% in radishes, 126.1% in lettuce, 38.4% in tomatoes, and 95.0% in sweet peppers (p < 0.01). Significant differences between treatments B1 and B2 were observed in the radish, tomato, and sweet pepper crops but not in lettuce. The profitability of biochar application to these crops was studied by considering a biochar price of 800 EUR/t and applying a CO2 fixation subsidy, assuming the updated February 2... [more]

Solar energy is prevalent in many applications, therefore, the reliability of solar energy systems has become an important topic for research communities and industry. High reliability and fault-tolerant capability are particularly vital for the solar energy systems that are mission-critical and/or inaccessible to affordable maintenance. In order to enhance the reliability of a grid-tied PV system, a fault-tolerant Photovoltaic (PV) inverter, termed Integrated Fault-Tolerant PV Inverter (IFTPVI), is proposed in this paper. The IFTPVI is based on the Highly Efficient and Reliable Inverter Concept (HERIC) and H5 inverters that are both popular and commercialized transformerless inverters in grid-tied PV applications. The IFTPVI can tolerate both open-circuit (OC) and short-circuit (SC) faults while maintaining the same voltage and current levels. The system description, reliability analysis, simulation in Matlab/Simulink 2018, and experimental results are provided to verify the feasibili... [more]

We have proposed a fruitful design principle targeting a concentration ratio (CR) >1000× for a typical high concentrating photovoltaics (HCPV) system, on account of a two-concentrator system + homogenizer. The principle of a primary dual-lens concentrator unit, completely analogous basic optics seen in the superposition compound eyes, is a trend not hitherto reported for solar concentrators to our knowledge. Such a concentrator unit, consisting of two aspherical lenses, can be applied to minify the sunlight and reveal useful effects. We underline that, at this stage, the CR can be attained by two orders of magnitude simply by varying the radius ratio of such two lenses known from the optics side. The output beam is spatially minimized and nearly parallel, exactly as occurs in the superposition compound eye. In our scheme, thanks to such an array of dual-lens design, a sequence of equidistant focal points is formed. The secondary concentrator consists of a multi-reflective channel, whic... [more]

Perfluorosulfonic acid (PFSA) polymer is considered as a proton exchange membrane material with great potential. Nevertheless, excessive water absorption caused by abundant sulfonic acid groups makes PFSA have low dimensional stabilities. In order to improve the dimensional stability of PFSA membranes, nanofibers are introduced into PFSA membranes. However, because nanofibers lack proton conducting groups, it usually reduces the proton conductivities of PFSA membranes. It is a challenge to improve dimensional stabilities while maintaining high proton conductivities. Due to the structural designability, covalent organic frameworks (COFs) with proton conductive groups are chosen to improve the overall performance of PFSA membranes. Herein, COFs synthesized in situ on three-dimensional PAN nanofibers were introduced into PFSA to prepare PFSA@PAN/TpPa-SO3H sandwiched membranes. The PFSA@PAN/TpPa-SO3H-5 composite membrane exhibited outstanding proton conductivity, which reached 260.81 mS·cm... [more]

The state of health (SOH) is among the most important parameters to be monitored in lithium-ion batteries (LIB) because it is used to know the residual functionality in any condition of aging. The paper focuses on the application of the extended Kalman filter (EKF) for the identification of the parameters of a cell model, which are required for the correct estimation of the SOH of the cell. This article proposes a methodology for tuning the covariance matrices of the EKF by using an optimization process based on genetic algorithms (GA). GAs are able to solve the minimization problems for the non-linear functions, and they are better than other optimization algorithms such as gradient descent to avoid the local minimum. To validate the proposed method, the cell parameters obtained from the EKF are compared with a reference model, in which the parameters have been determined with proven procedures. This comparison is carried out with different cells and in the whole range of the cell’s S... [more]

Atmospheric environmental quality affects the high quality and sustainable development of the economy. The optimisation and upgrading of the industrial system are important to improve the operation efficiency of the economy and society. Firstly, this paper constructs the theoretical analysis framework of coupling and coordination between the atmospheric environment system and the industrial system and analyses the internal mechanism of the interaction and coordinated development of the two systems. Then, it puts forward the combination of the coupling coordination model and the VAR model (Vector autoregressive model) and presents the analysis and evaluation method of the relationship between them from the two perspectives of “static” and “dynamic”. Finally, the empirical study is conducted in Taiyuan, a resource-based city in China. The results show that: (1) The two systems in Taiyuan have an obvious interaction and develop in the direction of benign coupling. (2) The impact of the tw... [more]

Beach-bar reservoirs have been promising hydrocarbon-bearing exploration advances in the Beibuwan Basin, especially in the WZ12-2 area within the Weixinan sag. The sedimentary characteristics, distribution and formation mechanisms of beach-bar sand bodies in Mbr2 (Member 2) of the Paleogene Liushagang Fm. in the WZ12-2 area within the Weixinan sag were analyzed based on well-log, seismic and core data on thin section and heavy mineral data. Mbr2 in the WZ12-2 area comprises a third-order sequence, which consists of three systems tracts (lowstand systems tract, transgressive systems tract and a locally developed highstand systems tract). Thick beach-bar sand bodies are developed in the WZ12-2 area during the lowstand systems tract stage. The formation of sandy beach-bar sand bodies can be divided into five stages. By integrating lithology, mineral composition, sedimentary structures and geophysical characteristics, it can be concluded that the beach-bar sand bodies in the study area wer... [more]

This Editorial summarizes the papers of the Special Issue entitled ‘Advanced Control Techniques for Wind/Solar/Battery Systems’ published in Energies. The Special Issue includes four scientific articles published in 2021 and 2022 in the field of quasi-Z-Source inverter control, photovoltaic energy conversion, battery charge control, wind turbine speed control, and solar irradiance prediction. New scientific achievements with experimental verifications of the achieved results are presented in all articles.

The construction of nanostructured materials for their application in electrochemical processes, e.g., energy storage and conversion, or sensing, has undergone a spectacular development over the last decades as a consequence of their unique properties in comparison to those of their bulk counterparts, e.g., large surface area and facilitated charge/mass transport pathways. This has driven strong research on the optimization of nanostructured materials for the fabrication of electrochemical devices, which demands techniques allowing the assembly of hybrid materials with well-controlled structures and properties. The Layer-by-Layer (LbL) method is well suited for fulfilling the requirements associated with the fabrication of devices for electrochemical applications, enabling the fabrication of nanomaterials with tunable properties that can be exploited as candidates for their application in fuel cells, batteries, electrochromic devices, solar cells, and sensors. This review provides an u... [more]