Direct torque control (DTC) is widely used in a permanent-magnet synchronous motor (PMSM), but it has its own shortcomings caused by high torque ripple. Deadbeat-direct torque and flux control (DB-DTFC) is a new torque and flux method compared with DTC. However, the traditional DB-DTFC is often based on rotor-flux-oriented control. The reference voltage of the stator is computed in a rotor-flux-oriented coordinate system, and the solution involves solving quadratic equations, which will increase the burden of computational processing. To improve the computation of the reference voltages and the control performance, this paper proposes a new DB-DTFC algorithm and introduces its basic principles. First, the proposed DB-DTFC algorithm uses the forward Euler equation to solve the reference voltage in a stator-flux-oriented coordinate system. Second, the discrete mathematical model is used to predict the next control current to achieve deadbeat control. Third, the structural model of the pr... [more]

Worldwide, around 998 million tons of agricultural waste are generated yearly, including livestock wastes, which create several critical environmental issues if not properly treated. In this study, a Geographical Information System (GIS)-based model to locate and quantify both the yearly amount of livestock waste, i.e., sheep wool, and the territorial distribution of sheep farms, was carried out and applied within the selected study area. The aim was to identify those territorial areas most suitable for localizing new shared wool collection centers to sustainably manage the reuse of this waste as potential green building material. Data related to both sheep farms and sheep number and the related sheep shared wool (SSW) yearly production were acquired and applied in GIS. By GIS-based model results, two collection centers have been identified within the provinces of Agrigento and Enna. Then, to develop a sustainable reuse in terms of reducing environmental impact due to the SSW logistics... [more]

Lignin pellets were produced using a single pellet system as well as a laboratory-scale pellet mill. The feedstock used in this work was lignin isolated from poplar wood (Populus tremuloides) using a direct saccharification process. An investigation was performed on the influence of the initial moisture content on the dimensions, impact and water resistance, fines content, mechanical durability, calorific value, and ash content, and, finally, the ultimate analysis was performed. These properties were then compared to pellets made from softwood bark using the same pelletization unit. Lignin pellets were then manufactured using four different types of additives (corn oil, citric acid, glycerol, and d-xylose) and ultimately, they were stored in two different conditions prior being tested. In general, manufacturing pellets that were entirely made of lignin generated samples with an overall higher hydrophobicity and higher calorific value. However, the ash and sulfur content of the lignin p... [more]

The aim of the paper is to analyze how regulatory design and its framework’s topics, other than macroeconomic factors, might impact green innovation by taking into consideration a brand-new renewable source of energy that is becoming more and more important in recent years: hydrogen and fuel cell patenting activities. Such activities have been used as a proxy for green technological change in a panel data of 52 countries over a 6-year period. A series of sectorial, energy regulation, and macroeconomic variables were tested to assess their impact on that technological frontier of green energy transition policy. As might have been expected, the empirical analysis carried out with the model that was prefigured confirms significant evidence of lock-in effects on fossil fuel policies. The model confirms, however, another evidence: countries already investing in renewables might be willing to invest in hydrogen projects. A sort of reinforcement to the further development of green sustainable... [more]

Most small−medium-sized turbine studies have focused on presenting new design methods and corresponding performance improvements rather than detailed dynamic investigations. This paper presents comprehensive dynamic investigations of a straight and a swept-back blade for a 100 kW turbine by performing modal analysis, dynamic load analysis, and flutter analysis. The considered load cases include steady wind and operational conditions under normal and extreme turbulence. Modal results show that although both blades have similar natural frequencies, their mode shapes are quite different due to the couplings in flapwise-torsion directions introduced by the back-swept geometry. This coupling alters the aeroelastic response of the blade, which results in different loads in the operational conditions. The load analysis results show that the blade damage equivalent fatigue loads for the swept blade are much lower (up to 29% for the flapwise bending moment and 31% for the edgewise bending momen... [more]

Green intellectual capital (GIC) is a distinctive intangible asset that may assist organizations in pursuing sustainable development strategies. In Polish organizations, interest in this new concept is low. Analysis of the literature showed a lack of research regarding the implementation of GIC practices or their impacts on the sustainable development of organizations in Polish enterprises. In order to fill the detected research gap, the study covered 150 randomly selected Polish enterprises. The purpose of the research was to determine the impact of activities fostering GIC on the environmental development of companies in Poland and to identify major practices supporting GIC development. In addition, the author attempted to establish a correlation between the impact of individual practices oriented at GIC formation and their practical implementations in the analyzed enterprises. The first stage of the analysis focused on identification of activities leading to the accumulation of GIC... [more]

This paper proposes a scheduling method of dual ESSs (Energy Storage Systems) for the purpose of reducing the peak load when there are sudden loads or generation changes during the on-peak time. The first ESS is scheduled once a day based on a day-ahead load prediction, and the second ESS is scheduled every 15 min during on-peak time based on a short-term load prediction by LSTM (Long Short-Term Memory). Special attention is paid to training the LSTM for the short-term load prediction by using the augmented past load data which is generated by adding possible uncertainties to the past load and temperature data. Based on the load forecast, optimization problems for the scheduling are formulated. The proposed scheduling method is validated using load and temperature data from a real building. In other words, when the proposed method is applied to the real building energy data in the case study, it not only shaves the peak load during on-peak time interval effectively but also results in... [more]

Wind energy is among the fastest-growing electric energy resources worldwide. As the electric power generated by wind turbines (WTs) varies, the WT-connected bus voltage fluctuates. This paper presents a study on implementing a swarm-based proportional and integral (PI) controller for GTO-STATCOM voltage regulator to mitigate the voltage fluctuation caused by the output variations of an offshore wind farm. The proposed swarm-based algorithm for the PI controller is Harris Hawks Optimization (HHO). Simulation results obtained by the HHO algorithm are compared with three other swarm-based algorithms and show that STATCOM with HHO-based PI controller can effectively regulate the WT-connected bus voltage under different wind power output conditions. It shows that the STATCOM compensation performance of the proposed algorithm is superior to that of the compared solutions in maintaining the stable WT-connected bus voltage.

Lignocellulosic biomass is both low cost and abundant, and unlike energy crops, can escape associated ethical dilemmas such as arable land use and food security issues. However, their usage as raw material in a biorefinery implies an inherent upstream pretreatment step to access compounds of interest derived from lignocellulosic biomass. Importantly, the efficiency of this step is determinant for the downstream processes, and while many pretreatment methods have been explored, extrusion is both a very flexible and promising technology. Extrusion is well-known in both the polymer and pharmaceutical industries and has been used since the 18th century. However, as a pretreatment method for lignocellulosic biomass, extrusion is relatively new. The first use for this purpose dates back to the 1990s. Extrusion enjoys a high degree of flexibility due to the many available parameters, but an understanding of extrusion requires a knowledge of these parameters and the different relationships bet... [more]

Castor bean (Ricinus communis L.) is a promising industrial crop suitable for cultivation in marginal conditions in the Mediterranean area, but the mechanical harvesting of the seeds is still usually performed manually. In this manuscript, the authors present a preliminary test to assess the effectiveness of equipping a combine harvester with a sunflower header to mechanically harvest castor beans. Machinery performance, seed loss from impact (ISL) and cleaning systems (CSL), and seed cleaning were evaluated and compared with the results obtained from the same combine harvester equipped with a cereal header. According to the results, no statistically significant difference in CSL was found. Values ranged from 162. 41 kg dry matter (DM) ha−1 in the cereal header to 145.56 kg DM ha−1 in the sunflower header, corresponding, respectively, to 8% w/w and 7% w/w of the potential seed yield (PSY). Using the sunflower header significantly lowered ISL (158.16 kg DM ha−1, i.e., 8% w/w of PSY) in... [more]

In today’s social, economic, and political reality, it cannot be overlooked that the energy self-sufficiency of municipalities not only optimizes the lives of the inhabitants of the municipality but also, in a broader perspective, the services provided by the municipality. The sustainable development of a municipality will therefore depend on its degree of self-reliance and self-sufficiency. Economic and technological considerations are not sufficient for the municipality to achieve optimal energy independence without normative conditions. The current (2021/2022) trends in electricity prices and in the development of national and international policies and strategies for electricity generation from renewable energy sources also make the change in the energy market structure toward distributed generation. The main objective of this paper is a theoretical analysis of the legal solutions in force in Poland that allow building energy self-sufficiency in municipalities and their adequacy to... [more]

Post-Optimum Sensitivity Analysis (POSA) extends numerical design optimization to provide additional information on how the design and performance would change if various parameters and constraints were varied. POSA is challenging since it typically requires accurate gradients and gradient-based optimization problems that provide Lagrange multipliers. To overcome this problem, this paper introduces a technique to automatically tune gradients with statistical methods and algorithms to calculate the Lagrange multipliers after an optimization. This allows these methods to be applied to problems with noisy gradients or problems solved with gradient-free optimization algorithms. These methods have been applied to swept wind turbine blades. Swept blades can reduce wind turbine loads by twisting out of the wind when the wind speed increases. The methods have shown that introducing design freedom in the sweep, blade root flap-wise bending moments and blade tip deflection has a weaker influence... [more]

This paper presents the results of simulation tests of a unique hybrid-excited permanent magnet machine operating in in different working regimes. The common feature of analyzed machine is a presence of magnetic barriers in the rotor structure. Structurally, this machine combines the advantages of the PMa-SynRM machine (Permanent Magnet-assisted Synchronous Machine) and a wound synchronous machine. The paper presents, among other results, the voltage and torque characteristics as a function of the current in the stator and the additional DC control coil. Selected results of experimental studies are also shown.

Solar energy has found increasing applications in recent years, and the demand will continue to grow as society redirects to a more renewable development path. However, the required high-frequency solar irradiance data are not yet readily available everywhere. There have been endeavors to improve its forecasting in order to facilitate grid integration, such as with photovoltaic power planning. The objective of this study is to develop a hybrid approach to improve the accuracy of solar nowcasting with a lead time of up to one hour. The proposed method utilizes irradiance data from the Copernicus Atmospheric Monitoring Service for four European cities with various cloud conditions. The approach effectively improves the prediction accuracy in all four cities. In the prediction of global horizontal irradiance for Berlin, the reduction in the mean daily error amounts to 2.5 Wh m−2 over the period of a month, and the relative monthly improvement reaches nearly 5% compared with the traditiona... [more]

Selective Harmonics Elimination is a high-efficiency modulation method for multilevel inverters that allows handling very high voltage applications. It eliminates the most significant harmonics and fixes the desired fundamental component. The main issue of these techniques is the complex process to obtain the appropriate switching-angles, being necessary to calculate them offline, meaning that if some disturbances occur, the system will not be compensated. This article proposes a real-time selective harmonic elimination for a single-phase cascaded multilevel inverter. The control strategy maintains constant the fundamental component of the output voltage while removing its third, fifth, and seventh order harmonics. The switching-angles are dynamically adapted to compensate for variations in the input voltage and the load. This is done by obtaining a virtual dynamic system using Groebner basis, an adaptation of the Newton-Raphson method, and implementing a digital PI controller into the... [more]

Recent research reveals that multi-phase motors in electric propulsion systems are highly recommended due to their improved reliability and efficiency over traditional three phase motors. This research presented a comparison of optimal model design of a six phase squirrel cage induction motor (IM) for electric propulsion by using Genetic Algorithm (GA) and Particle Swarm Optimization (PSO). A six phase squirrel cage induction motor is designed and simulated by ANSYS Motor-CAD. In order to find the best fit method, simulation results are compared and applied to the motors for electric propulsion, considering the influence of design upon the motor performance. The six-phase squirrel cage induction motor is more energy efficient, reliable and cost effective for the electric propulsion compared to the conventional three phase motor. In this study, first the initial parameters of the six phase squirrel cage induction motor have been determined and then these parameters have been compared wi... [more]

With the world’s energy resources decreasing, ethanol/acetone/ethyl acetate mixed fuel has the potential as a fossil fuel alternative or oxygenated fuel additive. In this work, the burning characteristics of ethanol/acetone/ethyl acetate mixed fuels including 3 pure fuels, 9 binary fuels, and 7 ternary fuels were studied at a temperature of 358 K, the pressure of 1 bar, and the equivalence ratios of 0.7 to 1.4 in the constant volume combustion chamber (CVCC). The burning velocities of the ternary fuels were compared at ϕ = 0.8, 1.0, and 1.4. The results show that the laminar burning velocities of the mixed fuels are affected by the contents of ethanol, acetone, and ethyl acetate. The Markstein length, Markstein number, and burning flux were also analyzed in this paper. Furthermore, a detailed chemical mechanism comprising 506 species and 2809 reactions was reduced to a skeletal mechanism including 98 species and 642 reactions, using the directed relation graph with error propagation (D... [more]

The Lower Paleozoic carbonate reservoir in the Tarim Basin is a hotspot area for deep oil and gas exploration in China. Although the Lower Cambrian of the Bachu Uplift has not encountered industrial oil flow, rich bitumen has been found there. As the most direct trace of petroleum migration, the effective identification of bitumen is the key to studying the hydrocarbon transportation path. In this study, the Adobe Photoshop quantification (PSQ) method is used to identify the bitumen content in the Xiaoerblak Formation in Well Shutan 1, and, combined with the bitumen characteristics of the Shihuiyao section, a high-quality petroleum transverse transport layer is determined. The results indicate the following: (1) In Well Shutan 1, bitumen is mainly concentrated in the middle and upper parts of the Xiaoerblak Formation with high porosity and high permeability. (2) The shale of the Yuertus Formation in the Shihuiyao section has low hydrocarbon generation potential. However, the overlying... [more]

Many countries have adopted the addition of biodiesel to diesel as a way of inserting renewable content into mineral fuel and making a contribution to the environment. The addition of ethanol to the diesel/biodiesel blend to increase the renewable content of the added fuel blend and reduce the percentage of biodiesel could be a strategysince the demand for biodiesel production is high, and this fuel has a high production cost when compared to ethanol. Thus, this study evaluated the performance and the content of NOx, CO and CO2 exhaust gases from a diesel engine fueled with blends of diesel/biodiesel/ethanol: pure B7, B7E3 (B7 with 3% ethanol) and B7E10 (B7 with 10% ethanol). Emissions of fuel blends were evaluated using the engine speed variation and tested at a speed of 1500 rpm under constant load (185 Nm). Assays were performed at engine speeds of 1000, 1100, 1250, 1500 and 1750 rpm and with loads of 10, 25, 50, 75 and 100% of the maximum torque. Through the performance curves, the... [more]

LED lamps have gradually replaced other lighting sources and have become mainstream in the lighting industry. The research on interharmonic sensitivity affecting their lighting quality cannot be ignored. By deconstructing the lamp-eye-brain module in the International Electrotechnical Commission (IEC) flicker model, a luminous flux flicker model without the constraints of a specific light source was proposed. The test system and corresponding analysis method of the interharmonic-luminous flux transfer coefficient in the model were described in detail, and the accuracy of the test results of the system was verified via incandescent lamp heat balance model simulations. Based on the test results, the conversion method of the interharmonic ratio of LED lamps under the flicker limit based on the interharmonic-flicker limit curve of incandescent lamps was deduced. By testing and comparing the differences in interharmonic-flicker limit curves of different driving types of LED lamps, the exper... [more]

Green transformation at the beginning of the 21st century occupies the top positions in modern society’s sustainability transition research and policy debates due to its multiple propositions of various innovations, addressing the still unsolved issues of rapidly on-going societal and technological changes. Rooting from the general climate change concerns, recently, sustainability transformation has become a special focus in the EU, which is facing new and very concrete demands—to elucidate the evidence-based pathways towards the green transformation with European Green Deal and European Climate Law targets ahead. The main aim of this research is to disclose the pathway towards the green transformation in Lithuania in one of the fast-growing research fields of circular bioeconomy—biogas production from manure and waste. To reach this aim, a hybrid methodology approach was used. Analysis and synthesis of scientific literature, document analysis and structuring, stakeholder mapping, inte... [more]

The complexity and uncertainty of the distribution system are increasing as the connection of distributed power sources using solar or wind energy is rapidly increasing, and digital loads are expanding. As these complexity and uncertainty keep increasing the investment cost for distribution facilities, optimal distribution planning becomes a matter of greater focus. This paper analyzed the existing mid-to-long-term load forecasting method for KEPCO’s distribution planning and proposed a mid- to long-term load forecasting method based on ensemble learning. After selecting optimal input variables required for the load forecasting model through correlation analysis, individual forecasting models were selected, which enabled the derivation of the optimal combination of ensemble load forecast models. This paper additionally offered an improved load forecasting model that considers the characteristics of each distribution line for enhancing the mid- to long-term distribution line load foreca... [more]

Building fabric retrofitting is an important first step in improving building energy efficiency. The United Kingdom’s (UK) housing stock is one of the most inefficient in Europe, and Northern Ireland has the second-highest level of fuel poverty in the UK. This Northern Irish case study developed three fabric retrofit scenarios that estimate potential demand reductions, CO2 emissions removals and retrofit costs. The first scenario reduces domestic demand by 10% and removes 6% of domestic emissions. The second scenario is more ambitious than the first, and results in an 18% reduction in demand and 12% of emissions removed. The third scenario proposes fabric retrofitting to PassivHaus standard and results in a 42% reduction in demand and 27% of emissions removed. Furthermore, retrofit schemes can provide up to approximately 350,000 jobs annually between 2022 and 2050 for the Northern Irish population. This study demonstrates how fabric retrofit scenarios can be streamlined to the unique f... [more]

Ethanol is a promising biofuel that can replace fossil fuel, mitigate greenhouse gas (GHG) emissions, and represent a renewable building block for biochemical production. Ethanol can be produced from various feedstocks. First-generation ethanol is mainly produced from sugar- and starch-containing feedstocks. For second-generation ethanol, lignocellulosic biomass is used as a feedstock. Typically, ethanol production contains four major steps, including the conversion of feedstock, fermentation, ethanol recovery, and ethanol storage. Each feedstock requires different procedures for its conversion to fermentable sugar. Lignocellulosic biomass requires extra pretreatment compared to sugar and starch feedstocks to disrupt the structure and improve enzymatic hydrolysis efficiency. Many pretreatment methods are available such as physical, chemical, physicochemical, and biological methods. However, the greatest concern regarding the pretreatment process is inhibitor formation, which might reta... [more]

This article approaches the optimal solution of energy sustainability based on the use of artificial intelligence (AI). The application of renewable energy sources (RES) and unit commitment (UC) is the basic idea of this concept. Therefore, a new approach to solving the UC problem is introduced. The proposed method has a simple procedure to obtain the popular solutions in an acceptable time interval, by creating a basic model of the schedule of the state of energy units RES. It is obvious that individual consumer units, of an operational nature, take hourly performance values by performing economic evaluations on them in the sense of cost optimization. This is conducted through an artificial intelligence (AI) algorithm by optimizing the dedicated cost function, simulated by annealing. Despite the acceptable solution obtained from these two steps, another shift is proposed, called the TDD process in a given consumer area. This process in the application of AI in the system of selection... [more]