Harmonic modeling of low-voltage networks with many devices requires simple but accurate models. This paper investigates the advantages and drawbacks of such models to predict the current harmonics created by single-phase full-bridge rectifiers. An overview is given of the methods, limiting the focus to harmonic analysis. The error of each method, compared to an accurate numerical simulation model, is quantified in frequency and time domain considering realistic input scenarios, including background voltage distortion and different system impedances. The results of the comparison are used to discuss the applicability of the models depending on the harmonic studies scale and the required level of detail. It is concluded that all models have their applicability, but also limitations. From the simplest and fastest model, which does not require a numerical solution, to the more accurate one that allows discontinuous conduction mode to be included, the trade-off involves accuracy and comput... [more]

In order to have a sustainable economic and social development, it is important to balance economic growth and ecological environmental damage. In this article, we used the resampling model under the triangular distribution to evaluate energy efficiency, because the input/output value may have measurement errors, time lag factors, arbitrariness, and other problems, causing their own DMU to change. After these factors were taken into consideration, the resampled input/output was estimated because a super-SBM efficiency value was placed in the confidence interval. From the past-present data, for the estimated data change, the time weight was provided according to the Lucas series, and the super-SBM was time-weighted. We applied this model to a dataset of G20 economies from 2010 to 2014. To the best of our knowledge, very few studies have applied the DEA method with resampling to analyze energy efficiency. Thus, our study contributes to the methodologies for energy efficiency evaluation.... [more]

In the European Union, the building sector accounts for more than 40% of final energy consumption, contributing to the deterioration of the quality of the environment. Among the various solutions that aim to reduce the negative environmental impact caused by the operation of buildings, solar hot water systems (SHW) are popular. The choice of a SHW system is associated with the comfort of use and the access to low-cost energy. The design guidelines include the technical parameters for system operation such as materials, dimensions, sizing and operation temperatures. However, the legitimacy of choosing a particular solution and the available technical parameters are key issues. In the presented study, a multi-criteria analysis was proposed as a basis for the proper selection of system parameters, e.g., collector type, solar tank volume. A model of the SHW system was used to calculate the possible solutions, ensuring the same comfort of usage for several design options. The analyzed model... [more]

Measurements of the dynamic load of conveyor belts of identical strengths were used to evaluate and compare the data for belts with and without a support system. The goal was to identify the effects of the support system in terms of a relative amount of impact energy absorbed by a conveyor belt. A dynamic model was designed based on selected parameters of the impact process. Damage to conveyor belts, caused by the absorption of impact energy, was evaluated using the applied methods of mathematical statistics.

CO2 reutilization processes contribute to the mitigation of CO2 as a potent greenhouse gas (GHG) through reusing and converting it into economically valuable chemical products including methanol, dimethyl ether, and methane. Solar thermochemical conversion and photochemical and electrochemical CO2 reduction processes are emerging technologies in which solar energy is utilized to provide the energy required for the endothermic dissociation of CO2. Owing to the surface-dependent nature of these technologies, their performance is significantly reliant on the solid reactant/catalyst accessible surface area. Solid porous structures either entirely made from the catalyst or used as a support for coating the catalyst/solid reactants can increase the number of active reaction sites and, thus, the kinetics of CO2 reutilization reactions. This paper reviews the principles and application of porous materials for CO2 reutilization pathways in solar thermochemical, photochemical, and electrochemica... [more]

In this paper, the authors present an overview of biomass gasification modeling approaches with the aim of evaluating their effectiveness as a modeling tool for the design and optimization of polygeneration plants based on biomass gasification. In fact, the necessity to build plant operating maps for efficiency optimization requires a significant number of simulations, and non-stoichiometry equilibrium models may allow fast computations thanks to their relative simplicity. The main objective consists of the assessment of thermodynamic equilibrium models performance as a function of biomass type and composition to better understand in which conditions of practical interest such models can be applied with acceptable reliability. To this aim, the authors developed two equilibrium models using both a commercial software (referred as Aspen model) and a simulation tool implemented in a non-commercial script (referred as analytical model). To assess their advantages and disadvantages, the two... [more]

This study empirically examines the effect of economic development on carbon emissions and revisits the environmental Kuznets curve in Suzhou, China. The study made use of the Gross Domestic Product Per Capita (GDPPC) of Suzhou, China as an indicator of economic development as it depicts the entire developmental ecosystem that indicates the level of production activities and total energy consumption. Bearing this in mind, the authors postulate that economic development directly increases carbon emissions through industrial and domestic consumptions. For this purpose, linear and non-linear approaches to cointegration are applied. The study finds the existence of an inverted U-shape relationship between economic development and carbon emission in the long run. Trade openness and industrial share are positively contributing to increasing carbon emissions. Energy use shows a positive sign but an insignificant association with carbon emissions. The study concludes that carbon emissions in S... [more]

Studying and analyzing the challenges that the renewable energy sector faces can help evaluate the risks and improve the planning. This research is done by considering the challenges in the implementation of sustainable generation of electricity through RESs in India, based on factors, including technical, financial, involvement, support, and others. The triangular fuzzy number (TFN) method, based on fuzzy logic concept, is used to analyze the challenges in this study. In general, TFN comprises of three numbers, likewise Gaussian fuzzy numbers, trapezoidal fuzzy numbers also exist. The classified sets of numbers are denotations to decision-makers’ perspective or a choice towards the criterion preference. Although alternatives are many to design a fuzzy set depending on elements count, the TFNs are the ones considered as actual representations of a fuzzy number. On the other hand, cases the Gaussian or trapezoidal, are manifestations of fuzzy intervals. Another argument is that the memb... [more]

Conditions that prevail during harsh winters and hot summers pose a serious challenge for machine designers building devices suitable for operation in extreme weather. It is essential for the designers and the users to define the principles and conditions for the safe operation of machines and devices with hydraulic drive in low ambient temperatures. Bearing in mind the above, the author tested the hydraulic motors in thermal shock conditions (cold motors were fed with a hot working medium). This enterprise required the design and construction of a specialized stand for testing hydraulic motors, including satellite motors, in thermal shock conditions. The stand was equipped with the apparatus and a system for measuring the temperature of the moving parts of the satellite motor. The experimental tests were conducted in the laboratory of the Faculty of Mechanical Engineering and Ship Technology at Gdańsk University of Technology. The paper presents the results of tests of a correctly and... [more]

In the paper, we report our research on the improvement of thermal efficiency of refrigerated trailers by modification of their wall structure by placing a layer of phase change material inside them. The research was carried out in the field of transport, meeting the requirements of all classes provided for in the ATP agreement for refrigerated trailers. As part of the research, we formulated a numerical model of the proposed design of the refrigerator walls, which was subsequently validated by comparing the modeling results with the results of experimental tests carried out on a test bench designed specifically for this purpose. Based on the validated simulation conditions, we formulated the numerical model of a full-scale refrigerated semi-trailer, which was numerically tested under the conditions specified in the ATP Agreement. The results proved that adding a 6 mm layer of the SP-24 phase change material in each of the walls of the cold store allows the temperature inside the trail... [more]

Temperature is considered to be an important indicator that affects the capacity of a lithium ion batteries. Therefore, it is of great significance to study the relationship between the capacity and temperature of lithium ion batteries with different anodes. In this study, the single battery is used as the research object to simulate the temperature environment during the actual use of the power battery, and conduct a charge and discharge comparison test for lithium iron phosphate battery, lithium manganate battery and lithium cobalt oxide battery. In the test of capacity characteristics of lithium ion batteries of three different cathode materials at different temperatures, the optimal operating temperature range of the lithium ion battery is extracted from the discharge efficiencies obtained. According to the research results, the discharge capacity of a lithium ion battery can be approximated by a cubic polynomial of temperature. The optimal operating temperature of lithium ion batt... [more]

The article is devoted to the following issues: boiling of fluid in the cooling jacket of the engine cylinder head; agents that influenced the thermal conductivity coefficient of nanofluids; behavior of nanoparticles and devices with nanoparticles in the engine’s cylinder head cooling system. The permissible temperature level of internal combustion engines is ensured by intensification of heat transfer in cooling systems due to the change of coolants with “light” and “heavy” nanoparticles. It was established that the introduction of “light” nanoparticles of aluminum oxide Al2O3 Al2O3 into the water in a mass concentration of 0.75% led to an increase in its thermal conductivity coefficient by 60% compared to the base fluid at a coolant temperature of 90 °C, which corresponds to the operating temperature of the engine cooling systems. At the indicated temperature, the base fluid has a thermal conductivity coefficient of 0.545 Wm2×°C W/(m °C), for nanofluid with Al2O3 particles its v... [more]

In the European Green Deal and the Climate Act, the European Union has committed itself to achieving climate neutrality by 2050. This goal is to be achieved by joint efforts of all economic sectors, including forestry and its downstream sectors. One way to attain this goal is the effective and sustainable use of forest biomass for energy production. This article aims to quantify the potential of forest biomass resources for the production of electrical and thermal energy based on official departmental statistics, the current legal framework for forestry and the environment, and research results in the context of an extreme change in the raw material base due to the ongoing calamity caused by the spread of insect pests in the Czech Republic. This extreme can classify as a significant risk to the security of the energy supply from renewable sources in the event of oversizing new installed energy production from renewable sources. Based on data and calculations, an overall annual volume o... [more]

As a result of conducted air quality policy, including recent legal regulations (the local anti-smog resolution), the number of individual solid fuel heating devices in Cracow (Poland) gradually decreased. Reports on air quality in the city indicate that the concentration of pollutants in Cracow’s air shows a downward trend. However, a similar tendency in terms of improving air quality is also observed in the entire voivodeship, where, as a result of analogous although less radical measures, the number of individual solid fuel heating devices is also decreasing. The paper discusses the impact of legal regulations in Cracow on the improvement of air quality in the context of changes taking place in nearby cities. Trends in changes in PM10 and BaP (PM10) concentrations are analyzed. The rate of decline of the analyzed pollutants concentrations is estimated with the use of nonparametric linear regression. Analysis showed that the rate of decline in the average annual concentrations of PM1... [more]

Voltage sag is one of the most significant power quality problems in the industry and has a significant impact on induction motor safety and stability. This paper analyzes the characteristics of voltage dips in power systems and induction motors with a special emphasis on balanced dips with the help of virtual grids (regenerative grid simulator), as per IEC 61000-4-11. Three phase induction motors with 3.3 kW, 16 A coupled to a DC generator with 3.7 kW, and 7.8 A rated are considered for the test analysis. This paper aids in the development of an induction motor to achieve improved precision by taking different voltage sags into account. The experimental results benefit the design modifications of induction motors at industrial and other commercial levels of consumers regarding major power quality issues and the behavior of the induction motors. A proposed modification employing ANSYS is provided to further examine the precise performance of induction motors during sag events.

Catalytic hydropyrolysis via the introduction of external hydrogen into catalytic pyrolysis process using hydrodeoxygenation catalysts is one of the major approaches of bio-oil upgrading. In this study, hydrodeoxygenation of acetone over Mo/HZSM-5 and HZSM-5 were investigated with focus on the influence of hydrogen pressure and catalyst deactivation. It is found that doped MoO3 could prolong the catalyst activity due to the suppression of coke formation. The influence of hydrogen pressure on catalytic HDO of acetone was further studied. Hydrogen pressure of 30 bar effectively prolonged catalyst activity while decreased the coke deposition over catalyst. The coke formation over the HZSM-5 and Mo/HZSM-5 under 30 bar hydrogen pressure decreased 66% and 83%, respectively, compared to that under atmospheric hydrogen pressure. Compared to the test with the HZSM-5, 35% higher yield of aliphatics and 60% lower coke were obtained from the Mo/HZSM-5 under 30 bar hydrogen pressure. Characterizati... [more]

The aim of this article was to investigate the possible relationship between energy production and GDP growth. This problem is of a crucial importance because as a numerous studies show, it is difficult to give an unambiguous answer to the question of whether there is a relationship between GDP and energy production and what direction it takes if it exists, i.e., whether energy production drives GDP growth or GDP growth drives energy production. The research conducted by the authors used data on hourly power production in MWh/h averaged over a whole day, which were converted into total quarterly production. The data were divided in terms of the type of energy into conventional, renewable, other and total. Next, the correlation coefficient was calculated for proper data sets in order to determine whether there was a correlation between the variables. The main conclusion from the study is the fact that a correlation measured with the Pearson correlation coefficient is not reflected in th... [more]

In a broad sense, all materials with a biological origin can be called biomass, which includes those materials that have been obtained from the direct conversion of solar energy, such as plants and crops, their residues, the materials obtained from their industrial transformation as well as subproducts and residues and the organic fraction of the municipal solid wastes [...]

This paper describes an interior permanent magnet synchronous motor (IPMSM) based on a new adjustable field method. The proposed PM motor achieved magnetic field control utilizing magnetic saturation. In this paper, a back electromotive force (e.m.f.) measurement test and a load test using the prototype motor were conducted to clarify if the proposed motor had a wide operation range. In the back e.m.f. measurement test, it was confirmed that the proposed motor had a wide magnetic field controllable range of 51.7%. In addition, it was revealed, through the load test, that the proposed motor had a wide operating range, including both low-speed high-torque and high-speed low-torque driving conditions. Moreover, based on electromagnetic field analysis, the magnetic field control performance of the proposed adjustable field method was compared with the conventional field weakening control and other adjustable field methods. As a comparison result, it was verified that the proposed motor had... [more]

In this article, we propose the parameters of a battery that would be suitable for the conceptual design of a small training aircraft. The mass design of the battery is based on the requirements for real training flights performed by students in pilot training. Such a serial hybrid propulsion aircraft could be used in our UNIZA aviation, training and education center for pilot training. Due to socio-political pressures in reducing emissions generated by vehicles, there has also been massive research in the aviation industry in the field of hybrid and electric aircraft propulsion. In the introduction, the article deals with the energy sources used in aircraft propulsion. In hybrid propulsion, a combination of aviation fuel and electricity is used as the energy source. The required total energy must choose a suitable combination of these two energy sources. The biggest drawback of batteries that can be used in hybrid systems is their low energy density. Low energy density means that larg... [more]

The emergence of mass-spectroscopy with inductively-coupled plasma (ICP-MS) made it possible to study the microelement composition of crude oil and its derivatives with the limit of detection (LOD) at the ppt level. We have studied the crudes from West Siberian (Shaimsky, Sredneobsky and Oktyabrsky regions) and Tatarstan Romashinskoye oilfields with the ICP-MS method to detect 50 rare, rare-earth, and other microelements. The elemental composition is reasonably comparable to their concentrations in ultrabasites whereas the contents of most of the elements are low to the limit. On the diagrams of rare-earth elements, one can see the prevalence of light lanthanides and positive europium anomaly. Increased content of platinoids was found in Tatar oils; in some cases, the concentration of ruthenium reaches 0.06 g/t. The study shows that studied crudes have a specific microelement composition. Based on the elevated contents of transit elements and platinoids, a conclusion was made about the... [more]

This paper contributes to the climate policy discussion by focusing on the challenges and opportunities of reaching net zero emissions by 2050 in Italy. To support Italian energy planning, we developed energy roadmaps towards national climate neutrality, consistent with the Paris Agreement objectives and the IPCC goal of limiting the increase in global surface temperature to 1.5 °C. Starting from the Italian framework, these scenarios identify the correlations among the main pillars for the change of the energy paradigm towards net emissions by 2050. The energy scenarios were developed using TIMES-RSE, a partial equilibrium and technology-rich optimization model of the entire Italian energy system. Subsequently, an in-depth analysis was developed with the sMTISIM, a long-term simulator of power system and electricity markets. The results show that, to achieve climate neutrality by 2050, the Italian energy system will have to experience profound transformations on multiple and strongly... [more]

The electricity sector in the 21st century should be associated with renewable energy sources (RES), which the majority of society currently equates with solar photovoltaics, wind power, and hydroelectricity, with this energy being used mainly in households. Households consume only 20% of energy, with the remainder used in various sectors of the national economy. In these sectors, the possibilities of using renewable energy sources should be sought. Many experts express the opinion that myths about renewable energy sources exist only “in our minds and opinions, that we formed years ago”, mainly under pressure from the decreasing number of supporters of conventional energy sources. Currently, we observe much greater possibilities of using renewable energy sources globally, and all forecasts suggest that—by 2050—the economy, transport, and industry may become almost emission-free and rely on RES. Of course, we cannot present renewable energy sources only in terms of superlatives, because... [more]

This paper proposes a step-up DC−DC converter for a power electronic circuit for standalone photovoltaic systems with battery energy storages. The proposed DC−DC converter effectively converts low DC battery voltage into high DC-link voltage. It operates with soft-switching characteristics, which can reduce switching power losses. The proposed converter operates without output voltage feedback, which simplifies its control design. The operation principle of the proposed converter was described, along with the overall system configuration. The experimental results were discussed for the 500-W prototype system using a 12-V lead-acid battery.

We adopt a physics-guided, data-driven method to predict the most likely future production from the largest tight oil and gas deposits in North America, the Permian Basin. We first divide the existing 53,708 horizontal hydrofractured wells into 36 spatiotemporal well cohorts based on different reservoir qualities and completion date intervals. For each cohort, we fit the Generalized Extreme Value (GEV) statistics to the annual production and calculate the means to construct historical well prototypes. Using the physical scaling method, we extrapolate these well prototypes for several more decades. Our hybrid, physico-statistical prototypes are robust enough to history-match the entire production of the Permian mudstone formations. Next, we calculate the infill potential of each sub-region of the Permian and schedule the likely future drilling programs. To evaluate the profitability of each infill scenario, we conduct a robust economic analysis. We estimate that the Permian tight reserv... [more]