In this paper, various modern power engines developed by the American, Japanese, and European automobile industries will be compared. Specific data, including the efficiency, emission rate of nitrogen oxides (NOx), fuel consumption, and electronic vehicle technology, will be developed. Since the first invention of the automobile engine in the late 19th century, companies came up with unique innovations, including its structure, control systems, and additional mechanical installations to improve efficiency and reduce emissions. Numerous companies, including Ford, Toyota, and Mercedes-Benz, compete in the automobile industry to improve their engine’s efficiency and emission rates to create a clean environment. In addition, each country has its regulations on emission rates and automobile structure. Therefore, to meet these regulations, the structure and the system of the engines vary between companies in different countries. A variety of variable valve timing (VVT) systems, which is a me... [more]

Most of the traditional PID tuning methods are heuristic in nature. The heuristic approach-based tuned PID controllers show only nominal performance. In addition, in the case of a digital redesign approach, mapping of the heuristically-designed continuous-time PID controllers into discrete-time PID controllers and in case of the direct digital design approach, mapping of the continuous-time plant (forward converter) into the discrete-time plant, results in frequency distortion (or warping). Besides this, nonlinear elements such as ADC and DAC, and delay in the digital control loop deteriorate the control performance. There is a need to tune conventionally-designed digital controllers to enhance performance. This paper proposes optimized discrete-time PID controllers for a forward DC−DC converter operating in continuous conduction mode (CCM). The considered conventional digital PID controllers designed on the basis of the digital redesign and direct digital approaches are tuned by one o... [more]

The environmental safety of a car is currently one of the most important indicators of vehicle competitiveness and quality in the consumer market. Currently, assessment of the ecological properties of vehicles is based on various criteria. In the case of combustion-powered cars, most attention is usually paid to the values characterizing their use, and in terms of environmental assessment, pollutant emissions, and operational fuel consumption are key factors. The current article considers the possibility of using the life cycle assessment (LCA) method to analyze the ecological properties of a passenger car during its operation. A simplified LCA method for vehicles, which, in strictly defined cases, can be used for the analysis of environmental impact and assessment of the energy analysis related to its operation, is presented. For this purpose, a vehicle life cycle model is developed. Data on the operation of 33 passenger cars from different manufacturers with similar operational chara... [more]

The control and improvement of energy-environmental quality in buildings are responsible for almost 40% of the emissions related to energy and processes, and are essential to achieve the commitment of the Paris Agreement and the Sustainable Development Goals (SDGs) United Nations (UN). This paper provides a support tool to planners and administrators of the territory for the identification of interventions aimed at the energy requalification of the existing Italian building heritage, mainly for residential use. The purpose of this tool is to reduce energy consumption by intervening on the building envelope with specific solutions that are identified through a matrix resulting from the study. In the first part of the study, an analysis was carried out on various factors such as the existing residential building, the building and construction types and the materials of the envelope typical of each construction period, which are critical for energy efficiency issues. In the second part of... [more]

The production of wood pellets has grown considerably in the last decades. Besides woody biomass, other feedstocks can be used for pellet production. Among these, miscanthus presents some advantages because, even if specifically cultivated, it requires low inputs such as fertilisers and pesticides and shows high biomass yield (up to 28 tons of dry matter ha−1 in Europe). Even if in the last years some studies evaluated the environmental impact of woody pellet production, there is no information about the environmental performances of miscanthus pellet production. In this study, the environmental impact of miscanthus pellet was evaluated using the Life Cycle Assessment approach with a cradle-to plant gate perspective. Primary data were collected in a small-medium size pelletizing plant located in Northern Italy where miscanthus is cultivated to be directly processed. The results highlight how the miscanthus pellet shows lower environmental impact compared to woody pellet, mainly due to... [more]

An in-situ method is proposed for monitoring and estimating the power degradation of mc-Si photovoltaic (PV) modules undergoing thermo-mechanical degradation tests that primarily manifest through cell cracking, such as mechanical load tests, thermal cycling and humidity freeze tests. The method is based on in-situ measurement of the module’s dark current-voltage (I-V) characteristic curve during the stress test, as well as initial and final module flash testing on a Sun simulator. The method uses superposition of the dark I-V curve with final flash test module short-circuit current to account for shunt and junction recombination losses, as well as series resistance estimation from the in-situ measured dark I-Vs and final flash test measurements. The method is developed based on mc-Si standard modules undergoing several stages of thermo-mechanical stress testing and degradation, for which we investigate the impact of the degradation on the modules light I-V curve parameters, and equival... [more]

The low energy efficiency and excessive power of electric motors of large-scale vibrating machines for processing bulk materials motivated a new design of the inertial drive. This drive consists of one motor and two coaxial unbalanced masses, whose rotational frequencies are related in the ratio 2:1. This approach allows for a generation of the excitation force with variable amplitude and frequency, which changes depending on the inertial characteristics and shaft rotation frequency and does not relate to the phase difference of the unbalanced masses. Because of this, the symmetry axis of the resulting vector hodograph can be changed. The spectral composition of the exciting force up to 200 Hz contains higher harmonics, the energy share of which is 25.4% from the 2nd harmonic and 14.1% from the 3rd and higher harmonics that correspondingly improves bulk material treatment in comparison to single-frequency vibrators. The finite element model is used for checking the strength capacity of... [more]

The heatwaves that have affected our civilization in recent years pose a serious threat to the environment as well as the proper functioning of our bodies. Schools are facilities with specific microclimatic requirements. Thermal conditions in educational buildings are decisive for the stimulation and efficiency of the learning process, as well as the interaction of students. Based on the measurements of thermal comfort carried out in the school building, with the energy standard of a passive building, it can be observed that in schools with very low energy consumption, the problem of interior overheating may occur in the summer months. In this paper, an attempt was made to search for alternative passive measures allowing for the required indoor microclimate conditions to be obtained. Such solutions are in line with the spirit of the European energy policy and sustainable development. A model of the school under study was created using the Design Builder simulation program. The role of... [more]

The rapid urbanization in Northwest China highlights the mismatch of increasing energy demand and limited local energy supply. Nevertheless, the remote areas in Northwest China are abundant with rich solar energy resources and land space resource. Therefore, establishing a distributed solar energy system (DSES) is a feasible solution to the energy supply problem in remote Northwest China. Due to the strong fluctuations in the availability of solar energy, operation strategies based on fixed parameters may not ensure optimal operation of DSESs. In this study, dynamic operation strategies that allocate surplus power from photovoltaic panels according to variable ratios were developed in both grid-connected and off-grid scenarios, a joint optimization model for optimizing the design and operation of a DSES was established based on the dynamic operation strategies, and a DSES of a residential building in Shaanxi Province was used as a case study. The analysis results indicate that: (1) The... [more]

Concerns about the efficiency of Heating, Ventilating, and Air Conditioning systems, including Air Handling Units (AHUs), started in the last century due to the energy crisis. Thenceforth, important improvements on the AHUs performance have emerged. Among the various improvements, the control of the AHUs and the redesign of the fans are the most important ones. Although, with increasingly demanding energy efficiency requirements, other constructive solutions must be investigated. Therefore, the objective of this work is to investigate, using a computational fluid dynamics (CFD) tool, the fluid flow inside an AHU and to analyze different constructive solutions in order to improve the AHU performance. The numerical model provided a reasonable agreement with the experimental results in terms of air flow rate, despite the assumed simplifications. Regarding the constructive solution concept, the CFD results for the two different flow control units (FCUs) showed improvements in terms of fan... [more]

This paper presents the performance evaluation of a stator modular ring permanent-magnet generator to be embedded in a shrouded wind turbine. That is done to increase the power conversion for the same turbine area when compared to more conventional ones. An adapted structure allows the assembling of the prototype, aiming to verify its performance under controlled conditions. Aiming to verify the accuracy of an analytical subdomain model for a large diameter machine, the evaluation compares the results obtained by the electromagnetic finite element method and experimental measurements. The results of the components of the air-gap flux density, back EMF and electromagnetic torque obtained by the proposed analytical model and finite-element method are in good agreement with the experimental measurements. The experimental measurements of the iron loss and copper loss show that the prototype efficiency can reach 90% approximately.

Maize forms the basis of Mexican food. As a result, approximately six million tons of corncob are produced each year, which represents an environmental issue, as well as a potential feedstock for biogas production. This research aimed to analyze the taxonomic and functional shift in the microbiome of the fermenters using a whole metagenome shotgun approach. Two strategies were used to understand the microbial community at the beginning and the end of anaerobic digestion: (i) phylogenetic analysis to infer the presence and coverage of clade-specific markers to assign taxonomy and (ii) the recovery of the individual genomes from the samples using the binning of the assembled scaffolds. The results showed that anaerobic digestion brought some noticeable changes and the main microbial community was composed of Corynebacterium variable, Desulfovibrio desulfuricans, Vibrio furnissii, Shewanella spp., Actinoplanes spp., Pseudoxanthomonas spp., Saccharomonospora azurea, Agromyces spp., Serinic... [more]

This paper examines the impact of the effective stresses that develop during depletion of a faulted reservoir. The study is based on finite element modeling using 2D plane strain deformation analysis with pore pressure and elastoplastic deformation of the reservoir and sealing shale layers governed by the Drucker−Prager plasticity model. The mechanical properties and response of the rock formations were derived from triaxial test data for the sandstone reservoirs and correlation functions for the shale layers. A normal fault model and a reverse fault model were built using seismic data and interpretation of field data. The estimated tectonic in-situ stress field was transformed to the plane of the modeled geometry. Sensitivity studies were performed for uncertainties on the values of the initial horizontal stress and for the friction of the fault surfaces. It was found that the stress path during depletion is mainly controlled by the initial lateral stress ratio (LSR). The developed ef... [more]

Various methods can be used to reduce energy consumption in buildings. One of them is the tightening of energy requirements, which, like other methods, cannot result in a worsening of the indoor environmental quality. The article presents a study on the impact of changes in the thermal insulation of the building envelope on the energy demand, heating costs, and emissions. Mathematical models of the dependence of the index of annual usable energy demand for heating (EUH) of a residential house on the thermal transmittance coefficients (Ui) of selected building elements were developed. Values of Ui were adopted at three levels, corresponding to the maximum required values—as approved in Polish law for the periods from 2014, 2017, and 2021. The analyses were conducted for the location of the building in three of the five climate zones of Poland. It turned out that the differences in the energy demand in various locations in Poland amount to 32.6%. The change in Ui in the analyzed period c... [more]

Due to the constant evolution of the electricity markets around the world, new possibilities for contracting electricity are emerging. In Brazil, there are two models available to the consumer: the regulated contracting environment and the free contracting environment. Because of these possibilities for contracting electricity, it is important that consumers know how to migrate from the regulated to the free environment when it is an advantage. This study was conducted following the premises of three techniques: systematic literature review, gray literature review, and expert panel. The following question was asked: What are the determining factors to be considered by the consumer at the moment decision to migrate from the regulated electricity market to the free market? In total, 7 factors were identified and discussed in the literature review. The experts who participated in the study pointed out 3 influential scenarios in this decision making to migrate. The main contribution of thi... [more]

To balance the cost and volume when applying a low output current ripple, the power supply design should be able to eliminate the current ripple under any duty cycle in medium and high switching frequencies, and considerably reduce filter volume to improve power density. A stacked buck converter was eventually selected after reviewing the existing solutions and discussing their advantages and disadvantages. A stacked buck converter is used as a basis to propose the transient response and output current ripple elimination effect, boundary limit control method, and low output ripple dead time modulation method to make individual improvements. The principle, mathematical derivation, small-signal model, and compensator design method of the improvement method are presented in detail. Moreover, simulation results are used to mutually verify the correctness and effectiveness of the improvement method. A stacked buck converter with 330-V input, 50-V output, and 1-kW output power was implemente... [more]

Equivalent power system impedance is an important electrical quantity from many points of view. Areas in which this parameter plays an important role include, in particular: Voltage stability analysis, power quality, or fault condition analysis. Power system impedance estimation in real operation conditions can be performed by one of the non-invasive methods described by different authors. This paper aims to investigate and compare seven different methods for power system impedance estimation based on voltage and current variations measurement. After a brief description of selected methods, these methods were applied for power system impedance estimation in the case of two simple simulation tests and then in the case of three real measured data. Voltage and current changes used for power system impedance estimation in real conditions were measured in high voltage (HV) and medium voltage (MV) substations feeding steel mill with the electric arc furnace (EAF) operation. As the results pr... [more]

Since printed circuit heat exchangers (PCHE) are the largest modules of a supercritical carbon dioxide Brayton cycle, they can considerably affect the whole system’s performance and layout. Straight-channel and zigzag-channel printed circuit heat exchangers have frequently been analyzed in the standalone mode and repeatedly proposed for sCO2−BC. However, the impact of heat exchanger designs with straight and zigzag-channel configurations on the performance of the cycle and its components, i.e., the turbine and compressor, has not been studied. In this context, this study evaluates the effect of different heat exchanger designs with various values of effectiveness (ϵ), inlet Reynolds number (Re), and channel configuration (zigzag and straight channel) on the overall performance of the sCO2−BC and its components. For the design and analysis of PCHEs, an in-house PCHE design and analysis code (PCHE-DAC) was developed in the MATLAB environment. The sCO2−BC performance was evaluated utilizi... [more]

Comprehensive evaluation of shale gas resource, which plays a role in energy system optimization, atmospheric environmental cobenefit, and methane risk, has long been ignored in China. This research aims to fill this gap and conduct a study based on the China-Multi-pollutant Abatement Planning and Long-term benefit Evaluation model to answer the research question, “When considering environmental and climate risks, does the shale gas resource in China exert a negative or positive effect?” Results show that shale gas plays an important role in replacing coal and optimizing the energy structure. Shale gas can also effectively help reduce the key local pollutant emissions. Approximately 84.85 thousand of deaths (persons) and 32.24 billion yuan of economic loss can be avoided in 2030 with the reduction of SO2 and NOx. The methane risk, which has been disregarded in China when evaluating cobenefits, is also considered in this study. The economic loss due to methane leakage is estimated to re... [more]

Desalination using fossil fuels is so far the most common technique for freshwater production worldwide. However, such a technique faces some challenges due to limited fossil fuels, high pollutants in our globe, and its high energy demand. In this study, solutions for such challenges were proposed and investigated. Renewable biofuel blends were introduced and examined as energy/sources for desalination plants and, in turn, reduced dependency on fossil fuels, enhanced pollutants, and recovered energy for desalinations. Eight different blended biofuels in terms of dual and ternary blend approaches were investigated. Results displayed that dual and ternary blends of gasoline/n-butanol, gasoline/isobutanol, gasoline/n-butanol/isobutanol, gasoline/bioethanol/isobutanol, and gasoline/bioethanol/biomethanol were all not highly recommended as energy sources for desalination units due to their low heat recovery (they showed much lower than the gasoline, G, fuel); however, they could provide rea... [more]

Over the past few years, electricity demand has been on the rise. This has resulted in renewable energy resources being used rapidly, considering the shortage as well as the environmental impacts of fossil fuel. A renewable energy source that has become increasingly popular is photovoltaic (PV) energy as it is environmentally friendly. Installing PV modules, however, has to ensure harsh environments including temperature, dust, birds drop, hotspot, and storm. Thus, the phenomena of the non-uniform aging of PV modules has become unavoidable, negatively affecting the performance of PV plants, particularly during the middle and latter duration of their service life. The idea here is to decrease the capital of maintenance and operation costs involved in medium- and large-scale PV power plants and improving the power efficiency. Hence, the present paper generated an offline PV module reconfiguration strategy considering the non-uniform aging PV array to ensure that this effect is mitigated... [more]

This paper considers a non-orthogonal multiple access (NOMA) downlink network, where a hybrid of NOMA and beamforming designs is developed to enhance the channel capacity. We aim to improve the system performance in terms of rate fairness and power consumption. Hence, a multi-objective problem with a joint optimization of user equipment pairing, power control, and quality-of-service requirements is addressed. To efficiently solve the problem, we propose two low-complexity algorithms based on the inner-approximation method, with the first algorithm using the relaxation method and the second one using graph theory. Numerical results are provided to demonstrate the effectiveness of the two proposed algorithms in comparison with the exhaustive search and existing methods.

The boost-flyback converter is a DC-DC step-up power converter with a wide range of technological applications. In this paper, we analyze the boost-flyback dynamics when controlled via a modified Zero-Average-Dynamics control technique, hereby named Zero-Average-Surface (ZAS). While using the ZAS strategy, it is possible to calculate the duty cycle at each PWM cycle that guarantees a desired stable period-1 solution, by forcing the system to evolve in such way that a function that is constructed with strategical combination of the states over the PWM period has a zero average. We show, by means of bifurcation diagrams, that the period-1 orbit coexists with a stable period-2 orbit with a saturated duty cycle. While using linear stability analysis, we demonstrate that the period-1 orbit is stable over a wide range of parameters and it loses stability at high gains and low loads via a period doubling bifurcation. Finally, we show that, under the right choice of parameters, the period-1 or... [more]

We present our new designed concentric Hele-Shaw cell geometry with dynamic similarity to a real field wellbore annulus during primary cementing, and then, the results of displacement flow of Newtonian and yield-stress non-Newtonian fluids in it are described. The displacement stability and efficiency, the effect of back, front, and side boundaries on displacement, bypassing pockets of displaced yield-stress fluid in displacing fluid, and the behavior of pressure gradients in the cell are investigated. Applications of intermediate buoyant particles with different sizes and densities intermediate between those of successively pumped fluids for tracking the interface between the two displaced and displacing fluids are examined. The main idea is to upgrade this concentric Hele-Shaw cell geometry later to an eccentric one and check the possibility of tracking the interface between successive fluids pumped in the cell. Successful results help us track the interface between drilling fluid an... [more]

In this paper, a nonlinear controller is proposed to manage the rotational speed of a full-variable Squirrel Cage Induction Generator wind turbine. This control scheme improves upon tractional vector controllers by removing the need for a rotor flux observer. Additionally, the proposed controller manages the performance through turbulent wind conditions by accounting for unmeasurable wind torque dynamics. This model-based approach utilizes a current-based control in place of traditional voltage-mode control and is validated using a Lyapunov-based stability analysis. The proposed scheme is compared to a linear vector controller through simulation results. These results demonstrate that the proposed controller is far more robust to wind turbulence than traditional control schemes.