At present, the penetration of wind-driven electric generators or wind power plants (WPPs) in electric power systems is getting more and more extensive. To evaluate the steady state performances of such power systems, developing a valid WPP model is therefore necessary. This paper proposes a new method in modeling the most popular type of WPP, i.e., DFIG (doubly fed induction generator)-based WPP, to be used in power system steady state load flow analysis. The proposed model is simple and derived based on the formulas that calculate turbine mechanical power and DFIG power. The main contribution of the paper is that, in contrast to the previous models where the DFIG power factor has been assumed to be constant at unity, the constant voltage model proposed in this paper allows the power factor to vary in order to keep the voltage at the desired value. Another important contribution is that the proposed model can be implemented in both sub-synchronous and super-synchronous conditions (it... [more]

Fabrication tolerances, as well as uncertainties of other kinds, e.g., concerning material parameters or operating conditions, are detrimental to the performance of microwave circuits. Mitigating their impact requires accounting for possible parameter deviations already at the design stage. This involves optimization of appropriately defined statistical figures of merit such as yield. Although important, robust (or tolerance-aware) design is an intricate endeavor because manufacturing inaccuracies are normally described using probability distributions, and their quantification has to be based on statistical analysis. The major bottleneck here is high computational cost: for reliability reasons, miniaturized microwave components are evaluated using full-wave electromagnetic (EM) models, whereas conventionally utilized analysis methods (e.g., Monte Carlo simulation) are associated with massive circuit evaluations. A practical approach that allows for circumventing the aforementioned obst... [more]

This paper presents research on the development of pyrotechnic compositions producing an acoustic effect. These types of compositions are used in firecrackers to imitate a cannon shot—they are most frequently used during military exercises. The research was based on a mathematical model of an experiment. For environmental reasons, the replacement of the harmful oxidant Ba(NO3)2 by KClO4 and NH4ClO4 was modelled. The compositions were tested for reliability and evaluated in terms of friction sensitivity and burning rate. This allowed for the verification of the effectiveness of the modelling carried out. Optimum compositions were selected for further research.

This work investigates loss model sets based on empirical loss correlations for subsonic centrifugal compressors. These loss models in combination with off-design performance prediction algorithms make up an essential tool in predicting off-design behaviour of turbomachines. This is important since turbomachines rarely work under design conditions. This study employs an off-design performance prediction algorithm based on an iterative process from Galvas. Modelling of ten different loss mechanisms and physical phenomena is involved in this approach and is thoroughly described in this work. Geometries of two subsonic compressors were reconstructed and used in the evaluation of individual loss correlations in order to obtain a suitable loss model. Results of these variations are compared to experimental data. In addition, 4608 loss model sets were created by taking all possible combinations of individual loss estimations from which three promising candidates were selected for further inv... [more]

Due to their weak nature, such as low inertia, offshore energy hubs are prone to unprecedented fast dynamic phenomena. This can lead to undesired instability problems. Recent literature, with main focus on onshore systems, suggests that electrolysers could be an attractive option to support wind generators in the mitigation of balancing problems. This paper presents an Electromagnetic Transient (EMT) model for real-time simulation based study of the dynamics of active power and voltage responses of offshore hubs due to wind speed fluctuations. The purpose of this study was to ascertain the ability of an electrolyser to support an offshore energy hub under different scenarios and with different locations of the electrolyser. Two locations of Proton Exchange Membrane (PEM) electrolysers were considered: centralised (at the AC common bus of the hub) or distributed (at the DC link of the wind turbines). Numerical simulations conducted in RSCAD® on a 2 GW offshore hub with 4 × 500 MW wind p... [more]

This study evaluates the effects of pooling heat demands in a district for the purpose of upscaling heat production units by means of energy, exergy, economic, exergoeconomic, and environmental indicators, as well as the sensitivity to investment and fuel costs. The following production systems to satisfy the heat demands (domestic hot water production and space heating) of a mixed district composed of office (80%), residential (15%), and commercial (5%) buildings are considered: gas- and biomass-fired boilers, electric boilers and heat pumps (grid-powered or photovoltaic -powered), and solar thermal collectors. For comparison, three system sizing approaches are examined: at building scale, at sector scale (residential, office, and commerce), or at district scale. For the configurations studied, the upscaling benefits were up to 5% higher efficiency (energy and exergy), there was lower levelized cost of heat for all systems (between 20% and 54%), up to 55% lower exergy destruction cost... [more]

There are currently trends in the world to transfer and adapt traditional solutions to contemporary needs. This applies, inter alia, to mobile shelters used by nomadic peoples. The article is devoted to the research on the quality of internal air in the yurt and the possibilities of its adaptation to high contemporary quality and environmental requirements, while maintaining its characteristic sustainable values. The tested traditional Mongolian yurt was moved from the dry and cold climate of the Asian steppe to the temperate climate of Central Europe and has been significantly modified. The outer shell materials have been changed, replacing natural materials with modern tight insulating foils. The wood-fired stove has been replaced with an electric heater and the roof opening has been firmly closed. All of these modifications resulted in far-reaching changes in the quality of the internal environment in the yurt. The conducted measurements and simulations of CO2 concentration in the m... [more]

With the increase of combustion temperatures, the thermal radiation effect for hot components in the new generation of aero-engines has become a key factor in the combustion process, cooling structure design, and thermal protection. A radiation loading system can be used as an external heat source to simulate the real thermal environment of hot components in aero-engines. Total receiving power, as well as 3-D heat flux distribution, should better coincide with real conditions. With the aid of freeform optics and the feedback optimization method, the current study develops a concentrating-type radiation heating system fit for the leading-edge surface of a C3X turbine vane. A xenon lamp combined with a freeform reflector was optimized for controllable heat flux. A design method in the area of illumination engineering was innovatively extended for the current model. Considering the effect of polar angular radiative flux distribution of a xenon lamp, a Monte Carlo ray tracing (MCRT) method... [more]

Electrical faults can lead to transient and dynamic excitations of the electromagnetic generator torque in wind turbines. The fast changes in the generator torque lead to load oscillations and rapid changes in the speed of rotation. The combination of dynamic load reversals and changing rotational speeds can be detrimental to gearbox components. This paper shows, via simulation, that the smearing risk increases due to the electrical faults for cylindrical roller bearings on the high speed shaft of a wind turbine research nacelle. A grid fault was examined for the research nacelle with a doubly fed induction generator concept. Furthermore, a converter fault was analyzed for the full size converter concept. Both wind turbine grid connection concepts used the same mechanical drive train. Thus, the mechanical component loading was comparable. During the grid fault, the risk of smearing increased momentarily by a maximum of around 1.8 times. During the converter fault, the risk of smearing... [more]

Mining in underground plants is associated with high risk. Improving work safety and increasing the productivity of longwall systems in the mining industry is a problem considering many criteria. Safety aspects concern both the crew and the machinery. The KOMAG Institute of Mining Technology designed and manufactured a geometry monitoring system based on inclinometers that meet the requirements of the ATEX directive. Monitoring of the roof support geometry is used for the prevention of loss of roof stability: roof fall or/and cave-in. The system was tested on a real object in real conditions.

An efficient wireless power transfer (WPT) system is proposed using two self-resonant coils with a high-quality factor (Q-factor) over medium distance via an adaptive impedance matching network using ferrite core transformers. An equivalent circuit of the proposed WPT system is presented, and the system is analyzed based on circuit theory. The design and characterization methods for the transformer are also provided. Using the equivalent circuit, the appropriate relation between turn ratio and optimal impedance matching conditions for maximum power transfer efficiency is derived. The optimal impedance matching conditions for maximum power transfer efficiency according to distance are satisfied simply by changing the turn ratio of the transformers. The proposed WPT system maintains effective power transfer efficiency with little Q-factor degradation because of the ferrite core transformer. The proposed system is verified through experiments at 257 kHz. Two WPT systems with coupling effi... [more]

The sulfur-iodine (SI) cycle holds great promise as an alternative large-scale process for converting water into hydrogen without CO2 emissions. A major issue regarding the long-term stability and activity of the catalysts is their poor sulfur deactivation resistance in the HI feeding process. In this work, the effect of Ru addition for enhancing the activity and sulfur resistance of SiO2-supported Ni catalysts in the HI decomposition reaction has been investigated. The presence of H2SO4 molecules in the HI results in severe sulfur deactivation of the Ru-free Ni/SiO2 catalysts by blocking the active sites. However, Ni−Ru/SiO2 catalysts show higher catalytic activity without sulfur-poisoning by 25% and exhibit more superior catalytic performance than the Ru-free catalyst. The addition of Ru to the Ni/SiO2 catalyst promotes the stability and activity of the catalysts. The experimental trends in activity and sulfur tolerance are consistent with the theoretical modeling, with the catalytic... [more]

The paper studies the problem of assessing the vehicle energy efficiency on the streets of urban road network. As a result of morphological analysis of the system “Vehicle—Traffic flow—Road—Traffic Environment” 18 significant morphological attributes of its functional elements, that affect the energy efficiency of vehicles, were identified. Each attribute is characterized by 3−6 implementation variants, which are evaluated by the relevant quantitative or qualitative parameters. The energy efficiency of vehicles is determined by the criteria of their energy consumption considering the vehicle category, type of energy unit, mode of vehicle movement and adjustment factors—road, climatic and others. The input parameters values of the system in the process of traffic flow on the linear fragments of streets and road networks of the cities of Ukraine and Poland were measured. The set of independent system parameters is determined by applying the Farrar-Glober method based on statistical estim... [more]

As more economies are transitioning away from fossil fuels for their electricity production and towards greener alternatives, many socioeconomic implications of this shift remain actively debated. The present paper attempts to assess the economic impact of investments in renewable energy sources (RESs) for Greece and whether the broader effects of this transition can offset the negative impact that will occur due to the targeted phase-out of lignite plants by 2028, which constitute the predominant power source for Greece. Our methodological approach builds on input−output analysis and the creation of composite RES industries for the estimation of the net effects of a series of monetary shocks that correspond to Greece’s phase-out investment plan, utilizing the most recent national input−output tables and satellite structural business statistics. We focus on the structural effects of these shocks on a series of socioeconomic indicators, including GDP, employment, wages, government incom... [more]

Achieving electrification in an island considering less emission and levelized energy cost is a challenging goal on developing islands such as Kalpeni Island. This work exhibits the techno-economic assessment of a standalone hybrid system to generate power to Kalpeni Island, India through sensitivity and optimization analysis using HOMER software. Various system configurations like solar/DG, wind/DG, solar/wind/DG, and solar/wind are analyzed based on cost and electrical parameters. Based on the optimization results, the best hybrid system is chosen for Kalpeni Island considering different solar tracking methods. Then, multi-year and sensitivity analysis are performed to analyze the effect of load growth, rising diesel price, rising battery minimum SOC, rising PVS derating, rising photovoltaic cell temperature, and changing inverter and rectifier efficiency. The system operated with a solar photovoltaic system (PVS) and diesel generator (DG) with a tracking system on a vertical axis (T... [more]

Gas and oil pipelines are widely used to supply customers. They are often laid in parallel with high voltage power lines, sharing right of way. When the pipeline is located near overhead high-voltage power, corrosion caused by induced voltages from AC power lines can occur in utility pipelines. Therefore, the calculation of induced voltage is always required for both interference and maintenance workers as well as pipeline facility safety. For parallel distribution lines, the calculation method for the induced voltage is not suitable due to the excessive error caused by using the screening factors of the neutral current. For a more practical analysis of the induced voltage, a new analysis is needed using the actual neutral current and which also considers the overhead ground conductor and the neutral conductor. This paper analyzed the induced voltage from a parallel distribution system using Carson’s formula and vector analysis. Simulation analysis results are verified by separate Elec... [more]

An increasing emphasis on energy storage has resulted in a surge of R&D efforts into producing catalyst materials for the hydrogen evolution reaction (HER) with emphasis on decreasing the usage of platinum group metals (PGMs). Alkaline water electrolysis holds promise for satisfying future energy storage demands, however the intrinsic potential of this technology is impeded by sluggish reaction kinetics. Here, we summarize the latest efforts within alkaline HER electrocatalyst design, where these efforts are divided between three catalyst design strategies inspired by the three prevailing theories describing the pH-dependence of the HER activity. Modifying the electronic structure of a host through codoping and creating specific sites for hydrogen/hydroxide adsorption stand out as promising strategies. However, with the vast amount of possible combinations, emphasis on screening parameters is important. The authors predict that creating a codoped catalyst using the first strategy by sc... [more]

One of the main threats to ecological safety is the increased emissions of greenhouse gases. Promoting the purchase of electric vehicles and increasing their share among all cars in a given country can be considered as activities reducing the emissions of CO2 into the atmosphere. Based on Environmental Performance Index, in 2021, Poland is in 37th place among the most climate-friendly countries in the world, and 30th among similar countries in Europe. The aim of the article was to model the prices of electric vehicles as one of the elements of promoting climate security in Poland. For the purposes of the study, an analysis of data from electric vehicle sales advertisements on one of the Polish automotive services was carried out. Moreover, on this basis, the most important factors influencing the price of the vehicle were analyzed. For this purpose, forecasting models were built based on neural networks and selected models of decision trees based on the CART algorithm, boosted trees, a... [more]

Access to energy, including electricity, determines countries’ socio-economic development. The growing demand for electricity translates into environmental problems. Energy is therefore a crucial element of the European Union’s sustainable development strategy. This article aims to present the changes taking place in the electricity market in Poland considering the goals of the energy policy until 2040. This is the basis for the determination of the scale of processes taking place in the Polish energy sector from two perspectives, i.e., the production of electricity considering its level and energy carriers used, and the consumption of electricity in households depending on their location (rural vs. urban areas). The research was conducted at the regional level (NUTS 2 until 2017) in Poland. Secondary data from the Central Statistical Office (GUS) contained in the Local Data Bank were used, along with information from the European Commission and Eurostat websites. Results of the study... [more]

The in-box LOCA (Loss of Coolant Accident) represents a major safety concern to be addressed in the design of the WCLL-BB (water-cooled lead-lithium breeding blanket). Research activities are ongoing to master the phenomena and processes that occur during the postulated accident, to enhance the predictive capability and reliability of numerical tools, and to validate computer models, codes, and procedures for their applications. Following these objectives, ENEA designed and built the new separate effects test facility LIFUS5/Mod3. Two experimental campaigns (Series D and Series E) were executed by injecting water at high pressure into a pool of PbLi in WCLL-BB-relevant parameter ranges. The obtained experimental data were used to check the capabilities of the RELAP5 system code to reproduce the pressure transient of a water system, to validate the chemical model of PbLi/water reactions implemented in the modified version of SIMMER codes for fusion application, to investigate the dynami... [more]

With increasing concerns regarding environmental sustainability, energy transition has emerged as a vital subtopic in transition studies. Such socio-technical transition requires social learning, which, however, is poorly conceptualized and explained in transition research. This paper overviews transition research on social learning. It attempts to portray how social learning has been studied in the context of energy transition and how research could be advanced. Due to the underdevelopment of the field, this paper employs a narrative review method. The review indicates two clusters of studies, which portray both direct and indirect links concerning the phenomena. The overview reveals that social learning is a force in energy transition and may occur at different levels of analysis, i.e., micro, meso, and macro, as well as different orders of learning. The author proposes to develop the academic research on the topic through quantitative and mixed-methods research as well as contributi... [more]

Heat transfer systems for chemical processes must be designed to be as efficient as possible. As heat transfer is such an energy-intensive stage in many chemical processes, failing to focus on efficiency can push up costs unnecessarily. Many problems involving heat transfer in the presence of a chemically reactive species in the domain of the physical sciences are still unsolved because of their complex mathematical formulations. The same is the case for heat transfer in chemically reactive magnetized Tangent hyperbolic liquids equipped above the permeable domain. Therefore, in this work, a classical remedy for such types of problems is offered by performing Lie symmetry analysis. In particular, non-Newtonian Tangent hyperbolic fluid is considered in three different physical frames, namely, (i) chemically reactive and non-reactive fluids, (ii) magnetized and non-magnetized fluids, and (iii) porous and non-porous media. Heat generation, heat absorption, velocity, and temperature slips a... [more]

With diminishing fossil fuel resources and increasing environmental concerns, large-scale deployment of Renewable Energy Sources (RES) has accelerated the transition towards clean energy systems, leading to significant RES generation share in power systems worldwide. Among different RES, solar PV is receiving major focus as it is most abundant in nature compared to others, complimented by falling prices of PV technology. However, variable, intermittent and non-synchronous nature of PV power generation technology introduces several technical challenges, ranging from short-term issues, such as low inertia, frequency stability, voltage stability and small signal stability, to long-term issues, such as unit commitment and scheduling issues. Therefore, such technical issues often limit the amount of non-synchronous instantaneous power that can be securely accommodated by a grid. In this backdrop, this research work proposes a tool to estimate maximum PV penetration level that a given power... [more]

This study aims to design and optimize an organic Rankine cycle (ORC) and radial inflow turbine to recover waste heat from a polymer exchange membrane (PEM) fuel cell. ORCs can take advantage of low-quality waste heat sources. Developments in this area have seen previously unusable, small waste heat sources become available for exploitation. Hydrogen PEM fuel cells operate at low temperatures (70 °C) and are in used in a range of applications, for example, as a balancing or backup power source in renewable hydrogen plants. The efficiency of an ORC is significantly affected by the source temperature and the efficiency of the expander. In this case, a radial inflow turbine was selected due to the high efficiency in ORCs with high density fluids. Small scale radial inflow turbines are of particular interest for improving the efficiency of small-scale low temperature cycles. Turbines generally have higher efficiency than positive displacement expanders, which are typically used. In this st... [more]

The rigidity of information technology (IT) has been hindering the development of various businesses regarding energy management systems (EMSs) of power networks, although this area has become more diversified, resulting in changes of elements in the systems due to the introduction of renewable energy (RE) and the new energy industry. In order to effectively accommodate these changes, EMSs should be developed in a structure with a standard-based interface, which can secure interoperability between components in the EMS. In previous studies, the common information model (CIM) proposed by IEC TC57 has been utilized for developing EMSs of power networks, but there are gaps between the existing CIM and an information model for the EMSs of carbon-free island microgrids (MGs), which are a newly introduced form of power network covering multiple islands for reducing carbon emissions. This paper proposes a CIM-based software platform for a carbon-free island MG-EMS to efficiently operate the p... [more]