In this study, we present the wind distributions from a long-term offshore met mast and a novel approach based on the measure−correlate−predict (MCP) method from short-term onshore-wind-turbine data. The annual energy production (AEP) and capacity factors (CFs) of one onshore and four offshore wind-turbine generators (WTG) available on the market are evaluated on the basis of wind-distribution analysis from both the real met mast and the MCP method. Here, we also consider the power loss from a 4-month light detection and ranging (LiDAR) power-curve test on an onshore turbine to enhance the accuracy of further AEP and CF evaluations. The achieved Weibull distributions could efficiently represent the probability distribution of wind-speed variation, mean wind speed (MWS), and both the scale and shape parameters of Weibull distribution in Taiwan sites. The power-loss effect is also considered when calculating the AEPs and CFs of different WTGs. Successful offshore wind development require... [more]

Recently, issues related to the effects (benefit or harm) of processing nuclear waste and its further use as fuel have been increasingly often raised in the scientific discussion. In this regard, the research aims to investigate issues related to the assessment of the economic potential of nuclear waste use, as well as the cooperation between states in the context of the reduction of risks associated with nuclear waste storage and processing. The research methodology is based on an integrated approach, including statistical, factor analysis, and the proposed system of performance indicators for managing spent nuclear fuel use. The research was carried out on the basis of materials from Russia and the EU countries. In the course of the study, a model of cooperation between states has been developed (based on the example of technologies and methods of processing nuclear waste used in the EU and Russia) according to the nuclear waste (spent nuclear fuel) management algorithm. The model co... [more]

The combined operation of hybrid wind power and a battery energy storage system can be used to convert cheap valley energy to expensive peak energy, thus improving the economic benefits of wind farms. Considering the peak−valley electricity price, an optimization model of the economic benefits of a combined wind−storage system was developed. A charging/discharging strategy of the battery storage system was proposed to maximize the economic benefits of the combined wind−storage system based on the forecast wind power. The maximal economic benefits were obtained based on scenario analysis, taking into account the wind-power forecast error, and costs associated with the loss of battery life, battery operation, and maintenance. Case simulation results highlight the effectiveness of the proposed model. The results show that the hybrid wind−storage system is not only able to convert cheap electricity in the valley period into expensive electricity in the peak period, thus resulting in higher... [more]

South Africa has about 2.5 million households without electricity access, most of which are located in rural areas and urban informal settlements. The nexus of energy poverty and gender is at play in the affected communities, as women and girls are culturally stereotyped with the task of collecting unclean fuels (e.g., firewood) and using these for their households’ energy demands. Therefore, this study prioritized rural women and girls as respondents in the provinces most affected by gendered energy poverty (GEP) in the country. The study was carried out in selected rural unelectrified areas of Limpopo, Mpumalanga, and KwaZulu-Natal provinces using structured interviews. The study revealed that GEP in the rural areas has exposed women and girls living there to security concerns, health hazards, premature death, domestic fire accidents, time poverty, income poverty, illiteracy, drudgery in households and farm tasks, etc., at different levels of severity. It also showed the effects of p... [more]

This paper proposes a three-phase isolated flyback inverter (IFBI) for single-stage grid-tied solar PV applications, considering a simple sinusoidal pulse-width modulation (SPWM) scheme. The proposed single-stage inverter employs a reduced passive elements count by considering three input-parallel output-differential (IPOD) flyback converter modules. Additionally, a single small size LC-input low-pass filter is utilized at the input paralleling point for ripple-free input current operation, which is essential in grid-connected renewable energy applications. In addition, a mathematical model of the IFBI is presented to confirm the existence of its low-order harmonic components. A simple PI controller-based control scheme, considering only two loops and five sensors, is used to control the proposed grid-tied IFBI. Continuous modulation scheme (CMS) combined with SPWM is used to diminish the low-frequency harmonic components. Moreover, a simple selective harmonic elimination (SHE) loop is... [more]

Railway power transmission lines (RPTL) are power lines that provide nontraction power supply for railways, such as communications and signals along the railway. With the advancement of technology, power cables are being used more and more widely. Operational experience has shown that during the operation of power cables, abnormal heat is often caused by fault factors such as poor joint crimping and severe partial discharge caused by insulation defects, leading to cable burns in extreme cases. Distributed temperature sensors (DTS), a kind of spatial continuous temperature sensor using sensing optical fiber, can measure the temperature along the cable and are expected to realize on-line monitoring and positioning of cable heating faults. This paper first builds a finite element model of the cable under various faults to calculate the distribution characteristics of the temperature field of the faulty cable. Then the results are verified through experiments with the external sensing fibe... [more]

Contrary to the extensive amount of research on large wind turbines, substantial analyses of small wind turbines are still rare. In the present study, the wind energy potential of three locations in Poland is analyzed using real wind data from a five-year period and the parameters of the selected turbine model. Appropriate simulations are performed to assess the energy efficiency of the analyzed investments at a coastal, foothill, or lowland site. According to the results, the most favorable location for a small wind turbine is the coastal site (wind zone I). The payback time at this location is approximately 13 years, whereas the payback times at the other two analyzed are more than 3 times longer. The payback periods for the latter locations significantly exceed the estimated lifetime of the wind turbine, ruling out their economic viability. The cost of electricity generation varies greatly, from 0.16 EUR/kWh at the coastal location to 0.71 EUR/kWh at the lowland location. These resu... [more]

User’s choices of conical picks currently involve specifying their material and geometric parameters (functional requirements), incorporating the place and conditions of their work (operational requirements). The selection is usually made based on solely one criterion, which is the price. Thus, at the stage of both purchase and operation, the quality of picks, as well as their matching for a specific machine, are not assessed. The problem of defining whether the producer has fulfilled the user’s requirements arises only when the user questions the picks’ quality. Analysis of this problem has resulted in developing assumptions, concepts and research procedures based on the cutting process requirements. The procedure allows conducting tests to determine the geometric parameters of a pick, the type of material of the pick body and WC-Co insert, as well as the pick wear rate (intensity). The C2 index describes the wear rate (intensity)—the smaller its value, the slower the pick’s wear. Lab... [more]

For a deep understanding of the airflow in an environment of historic wooden trusses, it is necessary to analyze the object using simulation methods. To calculate the amount of air passing through the structural openings (components) using dynamic simulation, multi-zone network models based on the simplicity of modeling the individual zones are suitable. For a more detailed analysis of airflow and temperature distribution within one space, a computational fluid dynamics (CFD) simulation model was performed. The air volume through openings and surface temperatures was adopted from the multi-zone airflow network model. By using this simulation technique during a sunny summer day four characteristic states of air movement were simulated in the attic: more intense flow at noon and at midnight caused by a large temperature difference between air and surrounding surfaces and, subsequently, less intense flow when the air was mixed up effectively. The temperature distribution in the cross-sect... [more]

The article deals with the competitiveness of regions in the face of climate change. The aim was to present the concept of measuring the Regional Climate Change Competitiveness Index. We used a comparative and logical analysis of the concept of regional competitiveness and heuristic conceptual methods to construct the index and measurement scale. The structure of the index includes six broad sub-indexes: Basic, Natural, Efficiency, Innovation, Sectoral, Social, and 89 indicators. A practical application of the model was presented for the Mazowieckie province in Poland. This allowed the region’s performance in the context of climate change to be presented, and regional weaknesses in the process of adaptation to climate change to be identified. The conclusions of the research confirm the possibility of applying the Regional Climate Change Competitiveness Index in the economic analysis and strategic planning. The presented model constitutes one of the earliest tools for the evaluation of... [more]

Electricity companies around the world are constantly seeking ways to provide electricity more safely and efficiently while reducing the negative impact on the environment. Mineral oils have been the most popular transformer insulation, having excellent electrical insulating properties, but have many problems such as high flammability, significant cleaning problems, and are toxic to fish and wildlife. This paper presents an alternative approach to mineral oil: a transformer design that is clean and provides better performance and environmental benefits. A 50 kVA, 34.5/0.4 kV gas insulated distribution transformer was designed and evaluated using the COMSOL Multiphysics environment. R410A was used as insulation material. R410A is a near-azeotropic mixture of difluoromethane (CH2F2, called R-32) and pentafluoro ethane (C2HF5, called R-125), which is used as a refrigerant in air conditioning applications. It has excellent properties including environmentally friendly, no-ozone depletion,... [more]

In this study, ultrasound was used to accelerate two-stage (esterification−transesterification) catalytic synthesis of biodiesel from used cooking oil, which originally had a high acid value (4.35 mg KOH/g). In the first stage, acid-catalyzed esterification reaction conditions were developed with a 9:1 methanol/oil molar ratio, sulfuric acid dosage at 2 wt %, and a reaction temperature of 60 °C. Under ultrasound irradiation for 40 min, the acid value was effectively decreased from 4.35 to 1.67 mg KOH/g, which was decreased to a sufficient level (<2 mg KOH/g) to avoid the saponification problem for the subsequent transesterification reaction. In the following stage, base-catalyzed transesterification reactions were carried out with a 12:1 methanol/oil molar ratio, a sodium hydroxide dosage of 1 wt %, and a reaction temperature of 65 °C. Under ultrasound-assisted transesterification for 40 min, the conversion rate of biodiesel reached 97.05%, which met the requirement of EN 14214 stan... [more]

Natural gas hydrate is an important energy source. Therefore, it is extremely important to provide a clear imaging profile to determine its distribution for energy exploration. In view of the problems existing in conventional migration methods, e.g., the limited imaging angles, we proposed to utilize an amplitude-preserved one-way wave equation migration based on matrix decomposition to deal with primary and multiple waves. With respect to seismic data gathered at the Chilean continental margin, a conventional processing flow to obtain seismic records with a high signal-to-noise ratio is introduced. Then, the imaging results of the conventional and amplitude-preserved one-way wave equation migration methods based on primary waves are compared, to demonstrate the necessity of implementing amplitude-preserving migration. Moreover, a simple two-layer model is imaged by using primary and multiple waves, which proves the superiority of multiple waves in imaging compared with primary waves a... [more]

This paper summarizes and discusses some critical aspects of flying hypersonically. The first is the L/D (lift over drag) ratio determining thrust and that in turn depends on the slenderness Küchemann’s τ parameter. This second parameter is found to depend on the relative importance of wave versus friction drag. Ultimately, all engineering drag is argued to depend on vorticity formed at the expense of the vehicle kinetic energy, thus requiring work by thrust. Different mixing strategies are discussed and shown to depend also on mechanisms forming vorticity when the regime is compressible. Supersonic combustion is briefly analyzed and found, at sufficiently high combustor Mach, to take place locally at constant volume, unlike conventional Brayton cycles.

The state of charge (SOC) prediction for an electric vehicle battery pack is critical to ensure the reliability, efficiency, and life of the battery pack. Various techniques and statistical systems have been proposed in the past to improve the prediction accuracy, reduce complexity, and increase adaptability. Machine learning techniques have been vigorously introduced in recent years, to be incorporated into the existing prediction algorithms, or as a stand-alone system, with a large amount of recorded past data to interpret the battery characteristics, and further predict for the present and future. This paper presents an overview of the machine learning techniques followed by a proposed pre-processing technique employed as the input to the long short-term memory network (LSTM) algorithm. The proposed pre-processing technique is based on the time-based sliding window algorithm (SW) and the Shapley additive explanation theory (SHAP). The proposed technique showed improvement in accurac... [more]

The monitoring of the performance of heat treatment equipment has been the subject of a number of studies. This paper proposes and explores a new study on the models—and the monitoring thereof—for predicting the energy intensity of low-pressure carburisation processes using the DeepCaseMaster Evolution soaking furnace. For research purposes, 18 carburising experiments were performed with different carbon layers, at different input parameters, such as the number of cycles, time, temperature and average carburising pressure. Based on the research experiments conducted and statistical analysis, the influence of individual parameters on the energy consumption of the pump and heating systems was determined. Moreover, the models were verified on real data of low-pressure carburising processes. The innovativeness of the proposed solution is a combination of two areas: (1) defining and measurement of the parameters of the low-pressure carburising process; and (2) predicting the energy consumpt... [more]

Advanced Driver Assistance System (ADAS) represents a collection of vehicle-based intelligent safety systems. One in particular, Traffic Sign Recognition System (TSRS), is designed to detect and interpret roadside information in the form of signage. Even though TSRS has been on the market for more than a decade now, the available ones differ in hardware and software solutions they use, as well as in quantity and typology of signs they recognize. The aim of this study is to determine whether differences between detection and readability accuracy of market-ready TSRS exist and to what extent, as well as how different levels of “graphical changes” on the signs affect their accuracy. For this purpose, signs (“speed limit” and “prohibition of overtaking”) were placed on a test field and 17 vehicles from 14 different car brands underwent testing. Overall, the results showed that sign detection and readability by TSRS differ between car brands and that even small changes in the design of sign... [more]

The recent advancements achieved in the development of a fluid-to-fluid similarity theory for heat transfer with fluids at supercritical pressures are summarised. The prime mover for the development of the theory was the interest in the development of Supercritical Water nuclear Reactors (SCWRs) in the frame of research being developed worldwide; however, the theory is general and can be applied to any system involving fluids at a supercritical pressure. The steps involved in the development of the rationale at the basis of the theory are discussed and presented in a synthetic form, highlighting the relevance of the results achieved so far and separately published elsewhere, with the aim to provide a complete overview of the potential involved in the application of the theory. The adopted rationale, completely different from the ones in the previous literature on the subject, was based on a specific definition of similarity, aiming to achieve, as much as possible, similar distributions... [more]

In this investigation, six groups of cemented coal gangue-fly ash backfill (CGFB) samples with varying amounts of kaolin (0, 10, 20, 30, 40, and 50%) instead of cement are prepared, and their mechanical properties are analyzed using uniaxial compression, acoustic emission, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The uniaxial compressive strength, peak strain, and elastic modulus of CGFB samples decreased with the kaolin content. The average uniaxial compressive strength, elastic modulus, and peak strain of CGFB samples with 10% amount of kaolin are close to that of CGFB samples with no kaolin. The contribution of kaolin hydration to the strength of CGFB sample is lower than that of cement hydration, and the hydration products such as ettringite and calcium-silicate-hydrate gel decrease, thereby reducing strength, which mainly plays a role in filling pores. The contents of kaolin affect the failure characteristics of CGFB samples, wh... [more]

In recent decades, there has been a positive trend in world politics in the field of promoting territories’ sustainable development. At the same time, one of the most relevant areas is to promote the transition to renewable energy sources (RES), which correspond to one of the UN’s goals—Sustainable Development Goal 7 (SDG 7) “Ensuring universal access to affordable, reliable, sustainable and modern energy sources for all”. This article is devoted to the study of the renewable energy sources’ impact on the sustainable development of the Russian Arctic zone. The authors chose the level of carbon dioxide (CO2) emissions as an indicator reflecting the impact of RES on sustainable development, since this factor is one of the main factors for assessing trends in the activities of countries aimed at achieving progress on most of the Sustainable Development Goals of territories. The hypothesis of the relationship between the use of renewable energy sources and the achievement of progress on th... [more]

Voltages of electric double-layer capacitor (EDLC) modules vary rather wider than traditional secondary batteries. Although EDLCs should desirably be cycled in a voltage range as wide as possible to achieve a high energy utilization ratio, the wide voltage variation of EDLC modules impairs the performance of DC−DC converters. To address such issues, previous works reported series-parallel reconfiguration techniques, which are roughly divided into balance- and unbalance-shift circuits. However, conventional balance-shift circuits are not applicable to modules comprising odd number cells, impairing modularity. Unbalance-shift circuits, on the other hand, unavoidably cause cell voltage imbalance that reduces energy utilization ratio. This paper proposes a novel series-parallel reconfigurable EDLC module with cell voltage equalization capability. The proposed reconfigurable EDLC module is applicable to any number of cells, realizing good modularity. Furthermore, all cells in the proposed m... [more]

When developing a sustainability plan in a complex and heavily urbanized territory, one of the most relevant options available is installing rooftop photovoltaic (PV) panels. Thus, it is essential to determine the amount of available surface and the potential impact of such installations on the energy and emission budget of the area. Instead of processing remotely sensed imagery, which is a long process and does not allow considering the buildings’ ownership, this study develops an approach based on a cluster analysis of the urban/morphological characteristics of the municipalities. Once a clear group diversification is obtained, the roof surface of the center of gravity of each cluster is extrapolated to all similar settlements. This, together with the information of local solar irradiation, allowed us to compute each cluster’s potential solar energy production and its capability to respond to the local energy demand, a key parameter to decide about the possibility of a local smart el... [more]

Power generation units based on the bio-syngas system face two main challenges due to (i) the possible temporary shortage of primary sources and (ii) the engine power derating associated with the use of low-energy density fuels in combustion engines. In both cases, an external input fuel is provided. Hence, complementing syngas with traditional fuels, like natural gas, becomes a necessity. In this work, an experimental methodology is proposed, aiming at the quantification of the impact of the use of both natural gas and syngas in spark ignition (SI) engines on performance and emissions. The main research questions focus on investigating brake thermal efficiency (BTE), power derating, and pollutant emission (NOx, CO, THC, CO2) formation, offering quantitative findings that present the basis for engine optimization procedures. Experimental measurements were performed on a Toyota 4Y-E engine (a 4-cylinders, 4-stroke spark ignition engine) at partial load (10 kW) under different syngas ene... [more]

When designing the cement slurry for casing string cementing in geothermal boreholes, the appropriate thermal conductivity is selected. In the zone of geothermal water, where thermal energy is collected, cement slurry is used, from which the cement sheath has high thermal conductivity. On the other hand, the remaining part of the opening is sealed with slurry, from which the cement sheath will reduce thermal energy losses through appropriate thermal insulation. Cement slurry with appropriate thermal insulation includes light insulating materials. However, the use of such additives is very problematic as they are fractionated due to their low density. Therefore, measures should be taken to prevent fractionation of the cement slurry for sealing geothermal boreholes. This article presents the results of research on fractionation of cement slurries for sealing geothermal boreholes. 12 slurries were used for the tests. Six of them are based on class A cement, and six based on class G cement... [more]

This paper proposes a novel model predictive current control scheme for two-stage matrix converter. The switching frequency is kept constant by fixing the switching instant. The control strategy achieves to control source reactive power in the input side and output currents in the output side. In addition, the advantage of the proposed strategy compared with conventional model predictive control is firstly proved using the principle of vector synthesis and the law of sines in the vector distribution area. Moreover, a zero-current switching sequence is proposed and implemented to insure zero-current switching operations and reduce the switching losses. Furthermore, in order to suppress the input filter resonance, which is easier to be inspired by the model predictive control, compared with traditional control strategies, an innovative active damping technique is proposed and implemented. Finally, both simulation and experiment are implemented to verify the performance of the proposed st... [more]