This experimental study was carried out based on the nanotechnology approach to enhance the efficacy of engine oil. Atomic and surface structures of graphene oxide (GO) nanoparticles were investigated by using a field emission scanning electron microscope and X-ray diffraction. The nano lubricant was produced by using a two-step method. The stability of nano lubricant was analyzed through dynamic light scattering. Various properties such as thermal conductivity, dynamic viscosity, flash point, cloud point and freezing point were investigated and the results were compared with the base oil (Oil- SAE-50). The results show that the thermal conductivity of nano lubricant was improved compared to the base fluid. This increase was correlated with progressing temperature. The dynamic viscosity was increased by variations in the volume fraction and reached its highest value of 36% compared to the base oil. The cloud point and freezing point are critical factors for oils, especially in cold sea... [more]

The introduction of pervasive telecommunication devices, in the scope of smart grids (SGs), has accentuated interest in the distribution network, which integrates a huge portion of new grid applications. High impact low probability (HILP) events, such as natural hazards, manmade errors, and cyber-attacks, as well as the inherent fragility of the distribution grid have propelled the development of effective resilience tools and methods for the power distribution network (PDN) to avoid catastrophic infrastructural and economical losses. Multiple resilience evaluation frameworks are proposed in the literature in order to assist distribution system operators (DSOs) in managing their networks when faced with exogenous threats. We conduct detailed analysis of existing quantitative resilience studies in both electric and telecommunication domains of a PDN, focusing on event type, metrics, temporal phases, uncertainty, and critical load. Our work adopts the standpoint of a DSO, whose target is... [more]

This article presents the development, simulation and validation of the uncertainty cost functions for a commercial building with climate-dependent controllable loads, located in Florida, USA. For its development, statistical data on the energy consumption of the building in 2016 were used, along with the deployment of kernel density estimator to characterize its probabilistic behavior. For validation of the uncertainty cost functions, the Monte-Carlo simulation method was used to make comparisons between the analytical results and the results obtained by the method. The cost functions found differential errors of less than 1%, compared to the Monte-Carlo simulation method. With this, there is an analytical approach to the uncertainty costs of the building that can be used in the development of optimal energy dispatches, as well as a complementary method for the probabilistic characterization of the stochastic behavior of agents in the electricity sector.

The ecological and economic context determine the management goals of a modern enterprise, which are in line with the growing concern about the well-being of society caused by the effects of enterprises’ activities that are particularly harmful to the environment. This increases the need to search for new tools that will have the capacity to generate information supporting the decision-making process in the area of enterprise management in terms of ecological, economic, and social goals. For these reasons, synthetic measures of development were constructed on the basis of the set of diagnostic variables describing various aspects of sustainable development in the case. Based on the environmental synthetic indicators, it has been possible to point out the Polish voivodeships, in which enterprises that are particularly harmful to the environment were able to reduce the emissions of dust and gaseous pollutants in the 2005−2019 period. These changes were often accompanied by an increase in... [more]

Optimal design of regional integrated energy systems (RIES) offers great potential for better managing energy sources, lower costs and reducing environmental impact. To capture the transition process from fossil fuel to renewable energy, a flexible RIES, including the traditional energy system (TES) based on the coal and biomass based distributed energy system (BDES), was designed to meet a regional multiple energy demand. In this paper, we analyze multiple scenarios based on a new rural community in Dalian (China) to capture the relationship among the energy supply cost, increased share of biomass, system configuration transformation, and renewable subsidy according to regional CO2 emission abatement control targets. A mixed integer linear programming (MILP) model was developed to find the optimal solutions. The results indicated that a 40.58% increase in the share of biomass in the RIES was the most cost-effective way as compared to the separate TES and BDES. Based on the RIES with m... [more]

In terms of fuel resource, hydropower possesses a prominent advantage over any other large power plants which burn fossil fuels to generate electricity. Moreover, due to the abundance in resource availability (as a domestic source in small streams and rivers), small hydropower (SHP) plants are showing prominence all over the world. SHP plants have led to improved access to electricity usage in under-developed and developing nations, thereby contributing to sustainable development goals and social empowerment. SHP, as a technology, is regarded as the largest density renewable resource with high adaptability, and low investment costs. The primary objective of the paper is to study and analyze recent developments in SHP technologies with reporting statistical figures in terms of installed capacity and MW potential in several parts of the world. Methodologies adopted by researchers to conduct techno-economic analysis of SHP projects are reviewed. Various costs involved in conducting pre-fe... [more]

One common technique employed in control system design to minimize system model complexity is model order reduction. However, controllers designed by using a reduced-order model have the potential to cause the closed-loop system to become unstable when applied to the original full-order system. Additionally, system performance improvement techniques such as disturbance observers produce unpredictable outcomes when augmented with reduced-order model-based controllers. In particular, the closed-loop system stability is compromised when a large value of observer gain is employed. In this paper, a boundary condition for the controller and observer design parameters in which the closed-loop system stability is maintained is proposed for a reduced-order proportional-integral observer compensated reduced-order model-based controller. The boundary condition was obtained by performing the stability analysis of the closed-loop system using the root locus method and the Routh-Hurwitz criterion. B... [more]

The analysis of porosity and pore structure of shale rocks has received special attention in the last decades as unconventional reservoir hydrocarbons have become a larger parcel of the oil and gas market. A variety of techniques are available to provide a satisfactory description of these porous media. Some techniques are based on saturating the porous rock with a fluid to probe the pore structure. In this sense, gases have played an important role in porosity and pore structure characterization, particularly for the analysis of pore size and shapes and storage or intake capacity. In this review, we discuss the use of various gases, with emphasis on N2 and CO2, for characterization of shale pore architecture. We describe the state of the art on the related inversion methods for processing the corresponding isotherms and the procedure to obtain surface area and pore-size distribution. The state of the art is based on the collation of publications in the last 10 years. Limitations of th... [more]

The purpose of the research was to identify the factors determining the improvement of the sustainable energy management strategy in the process of building lasting value for stakeholders, identifying key activities supporting the process of improving the sustainable energy management strategy, and analyzing the degree of use of environmental indicators by organizations in Poland. In the research process, to achieve the assumed research goals, it was decided to use the following research methods: The “Delphic Method” and the CAWI method (Computer-Assisted Web Interview). The research was carried out on a sample of 102 organizations in Poland. The study identifies goals for the sustainable development of the organization, activities supporting the process of sustainable energy management, and indicators in the field of energy management. The key factors for the improvement of energy management strategies have been identified, including implementation of modern technologies, reduction of... [more]

Competition on the local and global market forces enterprises to implement modern solutions and adapt to technological changes. Applying modern solutions allows an increase in the quality of the product and reduces production costs. The acoustic sensor, as a relatively cheap solution, allows signals to be obtained which, after appropriate processing, can be used to develop an automatic control of the longwall shearer, together with the recognition of the type of shale. This paper presents an introductory research, the goal of which has been to check whether acoustic signals carry useful information on what kind of material−shale or coal−is being cut by the cutting head of a longwall shearer. For this purpose, the fast Fourier transform and short-time Fourier transform functions implemented in MatLab were used. The results of the analysis are presented in the form of three-dimensional graphs and spectrograms. To sum up, the research carried out so far justifies the need for continuation... [more]

This paper presents issues in the field of theory, construction, calculations, as well as the design of effervescent-swirl atomizers. The results of experimental studies of spraying liquids with different physico-chemical properties for this type of atomizers are discussed. Effervescent-swirl atomization is a complex process and its mechanism is not fully understood. Therefore, the purpose of the manuscript is the complexity of the atomization process and its mechanism as well as the influence of individual parameters on its efficiency were thoroughly analyzed. The analyzed parameters include: atomizer design, outlet shape, gas and liquid flow rate, injection pressure, physicochemical properties of the atomized liquid, pressure drop, outflow coefficient, spray angle, quantitative droplet distributions, and average droplet diameter. Moreover, in the work, on the basis of the literature review, the results of the research related to, inter alia, the phenomenon of air core formation and t... [more]

The optimal state of charge (SoC) balancing control for series-connected lithium-ion battery cells is presented in this paper. A modified SoC balancing circuit for two adjacent cells, based on the principle of a bidirectional Cuk converter, is proposed. The optimal SoC balancing problem is established to minimize the SoC differences of cells and the energy loss subject to constraints of the normal SoC operating range, the balancing current, and current of cells. This optimization problem is solved using the sequential quadratic programming algorithm to determine the optimal duties of PWM signals applied to the SoC balancing circuits. An algorithm for the selection of the initial points for the optimal problem-solving process is proposed. It is applied in cases where the cost function has no decreasing part. Experimental tests are conducted for seven series-connected Samsung cells. The optimal SoC balancing control and SoC estimation algorithms are coded in MATLAB and embedded in LabVIE... [more]

The development of internal combustion engines is currently based around the ideas of downsizing and rightsizing. These trends, however, are not very widespread in vehicles with hybrid drive systems. Nevertheless, the authors analyzed the performance indicators of hybrid drives in downsized vehicles. Two generations of a vehicle model, equipped with hybrid drive systems, were used in the analysis in which not only the design of the internal combustion engine was changed, but also other hybrid drive systems (including the transmission, electric motors and high-voltage batteries). The paper analyzes the energy flow in two hybrid vehicles of different generations during tests in real road driving conditions in accordance with the requirements of the RDE (real driving emissions) tests. The authors have confirmed that newer vehicle designs extend the vehicle range by 38% in the electric mode under the conditions of road traffic (68% in the urban conditions). The application of a combustion... [more]

With the current worsening of climate change-associated risks, the transition to low-carbon energy sources has become a global priority. In this context, the advances in the implementation of smart grids, which, in addition to greater efficiency and resilience, also allow greater penetration of renewable distributed energy resources, are becoming increasingly important. However, the necessary investments will be colossal. Many specialists see the process of opening up the electric energy markets as essential to boosting these new technologies. Greater decentralization of the decision-making process can potentially promote greater scalability. However, not all liberalization reforms have led to good results. Several researchers have been evaluating experiences in different countries. Brazil, a country with continental dimensions and peculiar characteristics, already counts with a mostly renewable electric energy generation mix. In recent decades, however, it has become increasingly depe... [more]

The article concerns the investigations of solar cells irradiated by waste light. The measurement method and instruments used are presented. Using this method, the spectra of the light emitted by different light sources are presented and the results of measurements of sensitivity characteristics of the selected solar cell are shown. On the basis of the obtained results of the measurements, a new model of a solar cell dedicated for SPICE is formulated. In this model, an influence of spectrum characteristics of the modeled solar cell on its photocurrent is taken into account. The correctness of this model is verified experimentally for all the considered lighting sources. It is proved that photocurrent is the highest for irradiation using a classical bulb, whereas it is the lowest for a fluorescent lamp.

An improved thermodynamic open Dual cycle is proposed to simulate the working of internal combustion engines. It covers both spark ignition and Diesel types through a sequential heat release. This study proposes a procedure that includes (i) the composition change caused by internal combustion, (ii) the temperature excursions, (iii) the combustion efficiency, (iv) heat and pressure losses, and (v) the intake valve timing, following well-established methodologies. The result leads to simple analytical expressions, valid for portable models, optimization studies, engine transformations, and teaching. The proposed simplified model also provides the working gas properties and the amount of trapped mass in the cylinder resulting from the exhaust and intake processes. This allows us to yield explicit equations for cycle work and efficiency, as well as exhaust temperature for turbocharging. The model covers Atkinson and Miller cycles as particular cases and can include irreversibilities in co... [more]

Nanomaterials with collective optical and magnetic properties are called smart or functional materials and have promising applications in many fields of science and technology. Undoped and Co-doped ZnAl2O4 were prepared using a co-precipitation-assisted hydrothermal method. A systematic investigation was carried out to understand the effects of the Co concentration on the crystalline phase, morphology, and optical and magnetic properties of Co-doped ZnAl2O4. X-ray diffraction confirmed the cubic spinel structure with the Fd3m space group, and there was no impurity phase. X-ray photoelectron spectroscopy of Co-doped ZnAl2O4 confirmed the existence of Zn, Al and O, and the Co in the optimized sample of ZAO-Co-3 confirmed the oxidation state of cobalt as Co2+. Transmission electron microscopy of pure and Co-doped ZnAl2O4 revealed micro-hexagons and nanosheets, respectively. The optical absorption results showed that the bandgap of ZnAl2O4 decreased with increasing Co concentration. The hy... [more]

In many areas in the world, the high voltage (HV) electricity grid is saturated, which makes it difficult to accommodate additional solar photovoltaic (PV) systems connection requests. In this paper, different scenarios to increase the installed PV capacity in a saturated grid are assessed on the basis of the net present value (NPV). The developed scenarios compare an increase of grid capacity, PV system azimuth variation, curtailment, and battery storage. For each scenario the net present value (NPV) is assessed using an optimization model as a function of the overbuild capacity factor, which is defined as the relative amount of PV capacity added beyond the available capacity. The scenarios are applied on a case study of the Netherlands, and the analysis shows that, by optimising curtailment, a PV system’s capacity can be increased to 120% overbuild capacity. For larger overbuild capacity investments in the electricity-grid are preferred when these costs are taken into account. Howeve... [more]

There are trade-offs for each power converter design which are mainly dictated by the switching component and passive component ratings. Recent power electronic devices such as Gallium Nitride (GaN) transistors can improve the application range of power converter topologies with lower conduction and switching losses. These new capabilities brought by the GaN High Electron Mobility Transistors (HEMTs) inevitably changes the feasible operation ranges of power converters. This paper investigates the feasibility of Buck and Boost based bi-directional DC/DC converter which utilizes Quasi-Square-Wave (QSW) Zero Voltage Switching (ZVS) on GaN HEMTs. The proposed converter applies a high-switching frequency at high output power to maximize the power density at the cost of high current ripple with high frequency of operation which requires a design strategy for the passive components. An inductor design methodology is performed to operate at 28 APP with a switching frequency of 450 kHz. In orde... [more]

The restriction on the battery life of sensors is a bottleneck for wireless sensor networks (WSNs). This paper proposes a new feed-forward multi-clustering protocol (FFMCP) to boost the network lifetime. The utilization of fuzzy logic helps to overcome the uncertainties in the value of input parameters. The proposed protocol selects the most suitable cluster heads (CHs) using the multi-clustering method. A multi-clustering technique is defined utilizing the node’s information of the previous round and a fuzzy inference system to decide the CHs. The sensor nodes spend energy due to non-uniform CH distribution and long-distance data transmission by member nodes. The main focus of the proposed protocol is to reduce the member node distance. Our proposal distributes CH nodes uniformly using unequal clustering. The simulation outcome reveals that the proposed algorithm(FFMCP) has better performance in terms of tenth node death (TND), half node death (HND), remaining energy after 800 rounds... [more]

The use of renewable energy sources (RES) has increased exponentially worldwide, as an alternative to the indiscriminate use of fossil fuels and to mitigate their effects on the environment. Cuba is not lagging behind in this development since the government’s plan until 2030 includes the contribution of renewable sources as a fundamental component in the national energy mix. This paper models possible scenarios based on 2019 statistics for achieving a 25% and 100% penetration of renewable sources by 2030 in the Isla de la Juventud’s (an island south of the main island of Cuba) electrical power system (EPS). This modeling is carried out utilizing and open source Excel-based accounting framework Long-range Integrated Development Analysis (LINDA). For this purpose, international and national trends in the use and development of renewable energy sources and the influence of the characteristics of each renewable source (wind, solar, biodiesel, battery storage) were analyzed. The analysis o... [more]

Biomass with a large amount of moisture is well-suited to be processed by supercritical water gasification, SCWG. The precipitation of inorganics, together with char formation and re-polymerization, can cause reactor plugging and stop the process operations. When plugging occurs, sudden injections of relatively large mass quantities take place, influencing the mass flow dynamics significantly in the process. Reactor plugging is a phenomenon very well observed during SCWG of industrial feedstock, which hinders scale-up initiatives, and it is seldom studied with precision in the literature. The present study provides an accurate evaluation of continuous tubular reactor dynamics in the event of sudden injections of water. An interpretation of the results regarding water properties at supercritical conditions contributes to comprehending mass and heat transfer when plugging occurs. Experiments are then compared to SCWG of a biomass sample aiming to give key insights into heat transfer and... [more]

As a consequence of increasing air pollution, the European Commission has decided to introduce special directives laying down the measures to achieve climate and energy neutrality. Renewable energy (RE) sources play an important role in the pursuit of these goals, which has been taken into account in the 2030 Agenda for Sustainable Development. The aim of this article is to describe patterns and trends in the achievements of the energy policy of European Union (EU) countries in the field of renewable energy in sustainable development. The identification of leaders in this field gives the possibility to analyse actions taken by the governments of these countries and the possible implementation of the introduced solutions on the ground of individual Member States at the regional and national levels. At the beginning Main goal of energy policy on the field of renewable energy sources (RES) is to increase production from environmentally friendly sources that is why trends were determined i... [more]

Renewable Energy Sources (RES) have become increasingly desirable worldwide in the fight against global climate change. The sharp decrease in costs of especially wind and solar photovoltaics (PV) have created opportunities to move from dependency on conventional fossil fuel-based electricity production towards renewable energy sources. Renewables experience around 7% (in 2018) annual growth rate in the electricity production globally and the pace is expected to further increase in the near future. Cuba is no exception in this regard, the government has set an ambitious renewable energy target of 24% RES of electricity production by the year 2030. The article analyses renewable energy trajectories in Isla de la Juventud, Cuba, through different future energy scenarios utilizing EnergyPLAN tool. The goal is to identify the best fit and least cost options in transitioning towards 100% electric power systemin Isla de la Juventud, Cuba. The work is divided into analysis of (1) technical pos... [more]

Cogging torque is a critical dilemma in Permanent Magnet Brushless DC (PMBLDC) motors. In medium-low power PMBLDC motors, redundant vibrations and forbidding noises arise as a result of the harmonic magnetic forces created by cogging torque. This paper introduces a simple approach for minimizing cogging torque in PMBLDC motors by applying placement irregularities in rotor magnets. An angle shift in the rotor magnets in surface-mounted PMBLDC motors helps to attain magnet displacement. This displacement imparts an asymmetrical magnet structure to the rotor. Maintaining pole arc to pole pitch ratio (L/τ) of between 0.6 and 0.8, shifting angles from 1° to 8° were considered in order to analyze the effect of the angle shift on the rotor magnets. An analytical expression was also derived for finding the shifting angle with the minimum cogging torque in the PMBLDC motor by using the Virtual Work Method (VWM). The optimization of the shifting angle with minimum cogging torque was investigated... [more]