This study analyses the Ukrainian energy system in the context of the Paris Agreement and the need for the world to limit global warming to 1.5 °C. Despite ~84% of greenhouse gas emissions in Ukraine being energy- and process-related, there is very limited academic literature analysing long-term development of the Ukrainian energy system. This study utilises the TIMES-Ukraine model of the whole Ukrainian energy system to address this knowledge gap and to analyse how the energy system may develop until 2050, taking into current and future policies. The results show the development of the Ukrainian energy system based on energy efficiency improvements, electrification and renewable energy. The share of renewables in electricity production is predicted to reach between 45% and 57% in 2050 in the main scenarios with moderate emission reduction ambitions and ~80% in the ambitious alternative scenarios. The cost-optimal solution includes reduction of space heating demand in buildings by 20%... [more]

Economic Dispatch (ED) problems have been solved using single-objective optimization for so long, as Grid System Operators (GSOs) previously only focused on minimizing the total production cost. In modern power systems, GSOs require not only optimizing the total production cost but also, at the same time, optimizing other important objectives, such as the total emissions of the greenhouse gasses, total system loss and voltage stability. This requires a suitable multi-objective optimization approach in ensuring the ED solution produced is satisfying all the objectives. This paper presents a new multi-objective optimization technique termed Multi-Objective Immune-Commensal-Evolutionary Programming (MOICEP) for minimizing the total production cost and total system loss via integrated Economic Dispatch and Distributed Generation installation (ED-DG). This involved the application of a weighted-sum multi-objective approach that combined with an optimization technique called Immune-Commensal... [more]

Companies working on semiconductors must currently assure the customers of not only the performance of the semiconductor device per se, but also its performance when it is implemented in a real board, therefore including the role of parasitic effects. It is therefore very important to evaluate, especially during the design phase, not only the single device, but the complete board and their mutual interactions. This consideration opens a new area of investigation in the field of electronic systems engineering. In the current literature, the problem of a software evaluation of parasitic dynamics and electromagnetic effects on printed boards is addressed from the point of view of researchers. Moreover, it is fundamental to have a complete view of the various tools that could be usefully adopted from the perspective of manufacturers. This is the main motivation of this technical note, which performs a comparative analysis of the most prominent software tools for printed circuit boards’ (PC... [more]

Serious environmental concerns call for revolutionary solutions to cope with the harmful effects of the conventional energy landscape. Therefore, residential and commercial customers require cleaner and more reliable energy sources as they become more dependent on energy for daily and critical needs. In this case, transitioning to a cleaner energy economy is of paramount importance for both the environment and the utilities as well as the end-users. The desired transformation will require the deployment of massive amounts of clean energy sources. Many of these resources, such as solar photovoltaic (PV), provide electricity in the form of direct current (DC) that enables the return of DC grids to the electric power arena. The electric system has slowly transitioned to DC, mainly on the demand side. In recent years, modern electronic devices, lighting systems, and an increased number of appliances (≈22% of the residential and commercial loads) have adopted DC systems. Studies suggest tha... [more]

We propose three idealized hydraulic fracture geometries (“fracture scenarios”) likely to occur in shale oil reservoirs characterized by high pore pressure and low differential in situ stresses. We integrate these geometries into a commercial reservoir simulator (CMG-IMEX) and examine their effect on reservoir fluids production. Our first, reference fracture scenario includes only vertical, planar hydraulic fractures. The second scenario has stimulated vertical natural fractures oriented perpendicularly to the vertical hydraulic fractures. The third fracture scenario has stimulated horizontal bedding planes intersecting the vertical hydraulic fractures. This last scenario may occur in mudrock plays characterized by high pore pressure and transitional strike-slip to reverse faulting stress regimes. We demonstrate that the vertical and planar fractures are an oversimplification of the hydraulic fracture geometry in anisotropic shale plays. They fail to represent the stimulated volume geo... [more]

A hybrid H2−air kinetic scheme of 11 species and 15 reactions is developed, which is capable of simulating the high-temperature air reaction flows and H2−O2 combustion flows respectively or simultaneously. Based on the Gupta scheme, the mole fraction varying with a Mach number at specific conditions is analyzed, and the weakly-ionized 7-species 7-reaction scheme is selected. The effect of nitrogenous species on the H2−O2 combustion is analyzed by a zero-dimensional simulation of steady-state and unsteady-state combustion under specified conditions, and the selected dominant nitrogenous reaction N + OH = NO + H is distinguished by the production rate of the nitrogenous species. The thermodynamic properties are verified by comparison using the NIST−JANAF database. The reaction rate coefficients of the dominant reaction of the hybrid kinetic scheme distinguished by a sensitivity analysis are corrected. The proposed kinetic scheme is validated by a zero-dimensional calculation of the ignit... [more]

The development of public transport systems is related to the implementation of modern and low-carbon vehicles. Over the last several years, there has been a clear progress in this field. The number of electric buses has increased, and the first solutions in the area of hydrogen fuel cells have been implemented. Unfortunately, the implementation of these technologies is connected with significant financial expenditure. The goal of the article is the analysis of effectiveness of financial investment, consisting in the purchase of 30 new public transport buses (together with the necessary infrastructure−charging stations). The analysis has been performed using the NPV method for the period of 10 years. Discount rate was determined on 4%, as recommended by the European Commission for this type of project. It is based on the case study of the investment project carried out by Metropolis GZM in Poland. The article determines and compares the efficiency ratios for three investment options-pu... [more]

This article presents a carrier-based pulse-width modulation (PWM) template for a 5-level, H bridge-based cascaded multilevel inverter (MLI). The developed control concept generates adequate modulation template for this inverter topology wherein a sinusoidal modulating waveform is modified to fit in a single triangular carrier signal range. With this modulation approach, classical multiplicity and synchronization of the triangular carrier signals criterion for the extension of sinusoidal pulse-width modulation, SPWM, to several cascaded 5-level, H-bridge-based MLI topology are removed. The proposed template can be used on the inverter configuration of any level with no further control modification. Nearly even distribution of switching pulses and equalized individual cascaded cell output power were achieved with the proposed modulation scheme. Three 5-level, H-bridge-based MLI units were cascaded for 1-phase, 13-level inverter operation; simulation and experimental results are adequate... [more]

The thermodynamic properties of fluid mixtures play a crucial role in designing physically meaningful models and robust algorithms for simulating multi-component multi-phase flow in subsurface, which is needed for many subsurface applications. In this context, the equation-of-state-based flash calculation used to predict the equilibrium properties of each phase for a given fluid mixture going through phase splitting is a crucial component, and often a bottleneck, of multi-phase flow simulations. In this paper, a capillarity-wise Thermodynamics-Informed Neural Network is developed for the first time to propose a fast, accurate and robust approach calculating phase equilibrium properties for unconventional reservoirs. The trained model performs well in both phase stability tests and phase splitting calculations in a large range of reservoir conditions, which enables further multi-component multi-phase flow simulations with a strong thermodynamic basis.

This paper aims at assessing the impact of retrofitting an existing, 730 MWe, coal-fired power plant into a biomass-fired combined heat and power (CHP) plant on its energetic and exergetic performances. A comprehensive thermodynamic model of the power plant was developed and validated against field data, resulting in less than 1% deviation between the model and the measurements for the main process parameters. The validated model was then used to predict the behaviour of the biomass CHP after retrofitting. The modelled CHP unit is coupled to a steam-explosion biomass upgrading plant, a biorefinery process, and a high-temperature heat network. 13 scenarios were studied. At constant boiler load, delivering heat to the considered heat clients can increase the total energy efficiency of the plant from 44% (electricity only) to 64%, while the total exergy efficiency decreases from 39% to 35%. A total energy efficiency of 67% could be reached by lowering the network temperature from 120∘C to... [more]

Photoluminescent strips forming a Low Location Lighting (LLL) system are the primary method for marking escape routes on passenger ships. The LLL system can be built as a self-luminous system (powered by electricity) or made as a series of strips made of photoluminescent materials, which glow and indicate the escape route after the loss of basic and emergency lighting. To ensure correct visual guidance, these strips must be installed at specific locations in the passageways and achieve appropriate photometric parameters after a certain time from their activation. The properties of the LLL system depend on the type of luminescent material used, the excitation source, and the exposure parameters. This paper presents the results of laboratory tests on two types of photoluminescent materials used for the construction of LLL systems. We recorded the change in luminance after the loss of excitation and measured the luminance values obtained 10 and 60 min after the loss of excitation under ex... [more]

Chalcopyrite Cu(In,Ga)Se2 (CIGS) solar cells prepared via metal-organic chemical vapor deposition (MOCVD) are one of the candidates for highly advanced photovoltaic devices. This is because of their effectiveness and potential for reducing production costs through large-scale production. However, research on MOCVD-prepared solar cells is progressing slower than that on other types of solar cells, primarily because the preparation of CuInSe2 (CIS)-based films via MOCVD is relatively more sophisticated. In this study, we analyzed CIS solar cells prepared via three-stage MOCVD and processed with relatively simple precursors and techniques. We achieved an energy-conversion efficiency of 7.39% without applying a buffer layer. Instead, we applied a Cu-deficient layer to create a buried pn junction. Ultimately, we demonstrated that the fabrication of fully-MOCVD-processed CIS photovoltaic devices is feasible.

This Special Issue contains the successful invited submissions [...]

As the number of users increased over the years, pioneering technologies and solutions in given areas ceased to be sufficient even in terms of performance. Therefore, there was a need for their development or even redesign and redefinition. One of the issues that undoubtedly has a huge impact on the current shape of the global network and the way information is processed in it is the issue of traffic balancing, especially the one in the server infrastructure related to the WWW service, providing users with the possibility of efficient and reliable web browsing. The paper presents a comparative analysis of selected open-source solutions used for traffic balancing in server infrastructures providing WWW service based on selected criteria. The designed architecture of the test environment and the test results of selected tools implementing the traffic-balancing functionality are presented. Methodologies, test plans, and comparison criteria are proposed. A comparative analysis of results b... [more]

Gas injection is one of the prospective methods in the development of unconventional oil reserves. Before implementation in the field, it is necessary to justify the effectiveness of using gas agents in specific object conditions. Experiments of oil displacement on physical models with subsequent numerical modeling can provide the information necessary to justify the feasibility of using gas injection in specific reservoir conditions. This work is devoted to a series of experiments determining the minimum miscibility pressure (MMP) on a slim tube model and the analysis of oil displacement dynamics for various gas compositions, as well as numerical modeling. Displacement experiments were carried out using a recombined oil sample from one of the fields in Western Siberia. The MMP was determined by the classical method of inflection point on the displacement efficiency versus injection pressure curve, which was 34.6 MPa for associated petroleum gas (APG) and 49.9 MPa for methane. The dysn... [more]

Decarbonizing the world economy, before the most damaging effects of climate change become irreversible, requires substantially increasing renewable energy generation in the near future. However, this may be challenging in mature wind energy markets, where many advantageous wind locations are already engaged by older wind farms, potentially generating suboptimal wind harvesting. This research developed a novel method to systematically analyze diverse factors to determine the level of maturity of wind markets and evaluate the adequacy of wind farm repowering at regional and individual levels. The approach was applied to wind markets in the United States (U.S.), in which several states were identified as having diverse levels of maturity. Results obtained from case studies in Texas indicated a consequential number of wind farms that have reached their twenty-year end-of-life term and earlier obsolescence levels. The proposed approach aided in determining wind farms that may benefit from... [more]

The continuous need for systematization and open dissemination of knowledge on Renewable Fuels intended for use in Internal Combustion Engines forms the premise of the presented Special Issue titled “Renewable Fuels for Internal Combustion”. Experts in the field were encouraged to share their latest findings in the form of original research papers, case studies, or short reviews. Works targeting all aspects of the value chain were considered necessary, including the following: (liquid and gaseous) fuel production process, upgrading (catalytic and fractional blending), up to end, valorization in combustion engines (conventional and advanced concepts). Finally, techno-economic analyses aiming to valorize the value chain holistically were warmly encouraged to submit papers in this Special Issue of the Energies Journal. In this book, the reader will find successful submissions that present the latest findings from the discussed research field, encapsulated into nine chapters.

The test study area is the Miocene reservoir of Nam Con Son Basin, offshore Vietnam. In the study we used unsupervised learning to automatically cluster hydraulic flow units (HU) based on flow zone indicators (FZI) in a core plug dataset. Then we applied supervised learning to predict HU by combining core and well log data. We tested several machine learning algorithms. In the first phase, we derived hydraulic flow unit clustering of porosity and permeability of core data using unsupervised machine learning methods such as Ward’s, K mean, Self-Organize Map (SOM) and Fuzzy C mean (FCM). Then we applied supervised machine learning methods including Artificial Neural Networks (ANN), Support Vector Machines (SVM), Boosted Tree (BT) and Random Forest (RF). We combined both core and log data to predict HU logs for the full well section of the wells without core data. We used four wells with six logs (GR, DT, NPHI, LLD, LSS and RHOB) and 578 cores from the Miocene reservoir to train, validate... [more]

Climate change and energy dependence are nowadays critical issues that the world is facing, requiring effective and urgent actions to properly address them in a timely fashion [...]

An observatory was established at the Ningtiaota Mine (China) in order to investigate the surface deformation pattern of N00 method workings mining in shallow buried thick coal seams in a windy-sand area. The observatory allows one to measure the coupling between the periodic changes of parameters related to ground subsidence and ground cracks with workings advancement. The data monitored in the field indicate that when the adjacent mining workings are mined below the ground, a sinkhole basin with a larger impact area will be formed. New ground fractures are formed above the mining area to connect with the fractures above the mining face. As a consequence a new pattern of “O” circle distribution beyond the working face is formed, which develops rapidly during the working face recovery. In addition, the dynamic fractures in coal mining are characterized by the phenomenon of self-healing. Our findings will help to protect the surface environment of the mine area during shallow buried hig... [more]

The aim of this study was to determine the role of an installation based on biodrying of municipal waste in a Circular Economy by taking into account the quantitative and qualitative changes in its selectively collected waste stream. As a case study, the Mechanical-Biological municipal waste treatment installation in Olsztyn, Poland, was selected, which is equipped with a separate section for valorizing the selectively collected waste stream. The scope of the work included a complete mass balance of the waste treatment plant, an assessment of the technological efficiency of the municipal waste biodrying installation, and determination of the changes in the main waste from 2016 to 2020. This paper proposes an empirical method for estimating process loss during biodrying and provides many technological results. The average process loss was 23.47%, and on average, 88.9% of the waste produced by biodrying consisted of the Refuse-Derived Fuel fraction. The recovery of commercial assortments... [more]

As the share of power converter-based renewable energy sources (RESs) is high, a microgrid, in islanded mode, is more vulnerable to frequency instability due to (1) sudden power imbalance and (2) low inertia. One of the most common approaches to address this issue is to provide virtual inertia to the system by appropriately controlling the grid-side converter of the RESs. However, the primary frequency controller (PFC) presented in this paper focuses on the fast compensation of power imbalance without adding inertia to the system. The proposed method is based on estimating the real-time power imbalance caused by a disturbance and compensating it using multiple small-scale distributed battery energy storage systems (BESSs). The power imbalance is estimated by observing the initial rate of change of frequency (RoCoF) following a disturbance. Based on the estimated power imbalance and the rating of the BESSs, the reference power for the BESSs is determined. The BESSs are controlled in gri... [more]

To meet the increasing anti-knocking quality demand of boosted spark-ignition engines, fuel additives are considered an effective approach to tailor fuel properties for satisfying the performance requirements. Thus, screening/developing bio-derived fuel additives that are best-suited for advanced spark-ignition engines has become a significant task. 2-Phenylethanol (2-PE) is an attractive candidate that features high research octane number, high octane sensitivity, low vapor pressure, and high energy density. Recognizing that the low temperature autoignition chemistry of 2-PE is not well understood and the need for fundamental experimental data at engine-relevant conditions, rapid compression machine (RCM) experiments are therefore conducted herein to measure ignition delay times (IDTs) of 2-PE in air over a wide range of conditions to fill this fundamental void. These newly acquired IDT data at low-to-intermediated temperatures, equivalence ratios of 0.35−1.5, and compressed pressures... [more]

Water is increasingly taking center stage when it comes to coping with climate change. Especially in urban areas, negative consequences from heavy rainfall events and prolonged dry periods are rising worldwide. In the past, the various tasks of urban water management were performed by different departments that often did not cooperate with each other (water supply, wastewater disposal, green space irrigation, etc.), as the required water supply was not a question of available water volumes. This is already changing with climate change, in some cases even dramatically. More and more, it is necessary to consider how to distribute available water resources in urban areas, especially during dry periods, since wastewater treatment is also becoming more complex and costly. In the future, urban water management will examine water use in terms of its various objectives, and will need to provide alternative water resources for these different purposes (groundwater, river water, storm water, tre... [more]

Water flow forecasts are an essential information for energy production, management and hydropower control. Advanced actions to optimize electricity production can be taken based on predicted information. This work proposes an ensemble strategy using recurrent neural networks to generate a forecast of water flow at Jirau Hydroelectric Power Plant (HPP), installed on the Madeira River in Brazil. The ensemble strategy consists of combining three long short-term memory (LSTM) networks that model the Madeira River and two of its tributaries: Mamoré and Abunã rivers. The historical data from streamflow of the Madeira river and its tributaries are used to validate the ensemble LSTM model, where each time series of river tributaries are modeled separated by LSTM models and the result used as input for another LSTM model in order to forecast the streamflow of the main river. The experimental results present low errors for training and test sets for individual LSTM networks and ensemble model.... [more]