Nuclear graphite can be used in fission and fusion systems due to its excellent nuclear performance and mechanical properties where the ability of oxidation resistance is usually concerned. Although the excellent performance of new graphite ET-10 was revealed by previous experiments regarding the accident conditions of a fission reactor, further studies are needed to oxidize the graphite under the conditions recommended by the ASTM D7542 standard. A test facility was designed and developed to oxidize the cylindrical specimen with a 10 L/min airflow. According to oxidation rates and microstructures of specimens, the chemical kinetics-controlled regime was determined as 675−750 °C, where the activation energy was obtained as 172.52 kJ/mol. The experiment results revealed the excellent ability of graphite ET-10 for oxidation resistance with lower oxidation rates and longer oxidation times compared with some mainstream graphite. The main reasons are the low contents of some impurities and... [more]

Electromobility is one of the leading trends transforming public transport worldwide. Supported by international organizations, such as the European Union, and national cofounding, public transport operators and local authorities are taking strategic decisions on the direction and scope of the electrification of rolling stock. Most of the electric buses that are being put into operation replace the previously used conventional buses, and consequently, most of the electric buses are operating on existing bus lines. By applying a strategic approach to selecting bus routes for electrification, the advantages of electric vehicles can be maximized. Based on a case study of the Polish city of Gdynia, this paper explores the usefulness of the multi-criteria analysis for selecting the bus lines for electrification. Multi-criteria analysis methods help decision makers to consider and weigh diverse criteria that include, among others, economic, social, technological and environmental aspects. To... [more]

This paper proposes a modified version of the power-based control (MPBC) applied to microgrids (µGs) with multiple points of connection (i.e., utility grid itself or any other neighboring µG). Using the MPBC, single-phase distributed energy resources (DERs) arbitrarily connected between the phases share the amounts of balanced power, while the unbalanced and homopolar power are steered only to the line-to-neutral inverters. The control technique is based on a three-level hierarchical control using narrow bandwidth, low data rate communication that properly coordinates the DERs connected to three-phase four-wire µGs. The MPBC allows the DERs to steer power flow at any of the multiple points of common coupling of a multi-PCC dispatchable µG. The modified control proposed herein is evaluated through simulation results using MATLAB/SIMULINK considering a real urban distribution grid with typical operational elements and conditions. When compared to the original power-based control (PBC), r... [more]

An important trend in today’s economy is to reduce the carbon footprint of organizations, businesses and households. Modern technologies, including ICT solutions, contribute to the reduction of CO2 production. The article focuses on the potential of using the cloud computing model in managing a modern and intelligent city. Modern city offices have an extensive IT infrastructure. With the emergence of new services provided online by the offices, the server infrastructure is also developing. Server rooms together with additional devices are characterized by high demand for electricity. Along with this, significant amounts of CO2 are produced. An alternative is the use of Cloud Computing solutions, which contribute to a significant reduction of the carbon footprint. The paper analyses potential solutions that can be used in city offices. The benefits and positive impact on the environment were highlighted. The empirical research was conducted based on questionnaires received from city off... [more]

The growing interest in the negative environmental impact of overhead power lines of high and extra-high voltage stems from the increasing ecological awareness of societies. Consequently, a number of respective legal restrictions have been issued and actions have been undertaken to reduce this impact, especially in the electric field of the power frequency. The aim of this paper is to analyze the possibilities of reducing the width of electric field influence zones by changing the design parameters of power lines and defining the spatial distribution of its conductors. This analysis was carried out using the developed and experimentally verified models for determining the electric field and audible noise in the power line environment. The computational models were used to analyze the width of the electric field influence zones of 400 kV lines and the noise levels at the borders of these zones. The research focused on single and double circuit 400 kV power lines. It was revealed that a... [more]

With the increasing adoption of distributed energy resources (DERs) such as wind and solar photovoltaics (PV), many distribution networks have changed from passive to active. In turn, this has led to increased technical and operational challenges such as voltage issues and thermal loading in high DER penetration scenarios. These challenges have been further increased by the uncertainties arising from DER allocation. The implication of DER allocation uncertainty in the planning process is far-reaching as it affects critical planning processes, including conductor size selection (CSS). Most reported CSS methods in the literature do not include DER allocation uncertainty modeling as they are mostly deterministic and are set out as optimization problems. The methods, therefore, lack foresight on future loading conditions and cannot be used in a CSS process for feeders with high DER penetration. This paper proposes a novel input−process−output stochastic−probabilistic CSS framework for dist... [more]

Simultaneous removal of nitrogen and phosphorous is a recommended practice while treating wastewater. In the present study, control strategies based on proportional-integral (PI), model predictive control (MPC), and fuzzy logic are developed and implemented on a plant-wide wastewater treatment plant. Four combinations of control frameworks are developed in order to reduce the operational cost and improve the effluent quality. As a working platform, a Benchmark simulation model (BSM2-P) is used. A default control framework with PI controllers is used to control nitrate and dissolved oxygen (DO) by manipulating the internal recycle and oxygen mass transfer coefficient (KLa). Hierarchical control topology is proposed in which a lower-level control framework with PI controllers is implemented to DO in the sixth reactor by regulating the KLa of the fifth, sixth, and seventh reactors, and fuzzy and MPC are used at the supervisory level. This supervisory level considers the ammonia in the las... [more]

The rise in energy consumption is largely driven by the growth of population. The supply of energy to meet that demand can be fulfilled by slowly introducing energy from renewable resources. The fluctuating nature of the renewable energy production (i.e., affected by weather such as wind, sun light, etc.), necessitates the increasing demand in developing electricity storage systems. Reliable energy storage system will also play immense roles to support activities related to the internet of things. In the past decades, metal-air batteries have attracted great attention and interest for their high theoretical capacity, environmental friendliness, and their low cost. However, one of the main challenges faced in metal-air batteries is the slow rate of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) that affects the charging and the discharging performance. Various types of nanostructure manganese oxide with high specific surface area and excellent catalytic properties h... [more]

The role of the Internet of Things (IoT) networks and systems in our daily life cannot be underestimated. IoT is among the fastest evolving innovative technologies that are digitizing and interconnecting many domains. Most life-critical and finance-critical systems are now IoT-based. It is, therefore, paramount that the Quality of Service (QoS) of IoTs is guaranteed. Traditionally, IoTs use heuristic, game theory approaches and optimization techniques for QoS guarantee. However, these methods and approaches have challenges whenever the number of users and devices increases or when multicellular situations are considered. Moreover, IoTs receive and generate huge amounts of data that cannot be effectively handled by the traditional methods for QoS assurance, especially in extracting useful features from this data. Deep Learning (DL) approaches have been suggested as a potential candidate in solving and handling the above-mentioned challenges in order to enhance and guarantee QoS in IoT.... [more]

According to the European Union (EU) regulations, EU members are obligated, among others, to improve the energy efficiency in the outdoor lighting sector. One of the ways to consider this fact is to install LED sources in luminaires. Due to the reasonable lighting requirements for the lighting of squares and parks, the cheapest way to modernize lighting is to replace conventional discharge lamps with LED sources in park luminaires. Using nine typical park luminaires, the influence of replacing classic sodium lamps with LED sources on the effect of light pollution and energy efficiency was analyzed. Using data, such as a photometric solid and a relative spectral distribution, simulation calculations were carried out in DIALux software and our own calculation tool to consider this issue. The studies considered 156 LED sources of different spectral distributions and a wide range of color temperatures from 1000 K to 9753 K as well as different color rendering index (CRI) values. The conduc... [more]

In the world, as in Lithuania, there is a costant search for new crops suitable for energy conversion. The coarse-energy crops and their biomass studied for this paper were assessed in a comprehensive manner, i.e., not only their calorific value and ash content but also their ash melting properties and pollutants emitted during the thermochemical conversion. The calorific value of energy crops varies from 17.92 ± 0.32 to 18.50 ± 0.66 MJ kg−1 and decreases in the following order: A. dubia > M. giganteus > C. sativa. Ash content varies from 1.51 ± 0.03 to 3.36 ± 0.23% and decreases in the following order: C. sativa > A. dubia > M. giganteus. The lowest primary ash deformation (648 ± 8 °C) was recorded for C. sativa. Taking into account the specificity of our research and the changes in biomass ash content due to mineral nitrogen fertilization, it has been found that that higher levels of nitrogen fertilizers in the combustion products reduce CO and increase the total CO2 content of the c... [more]

In December 2019, the European Commission unveiled an ambitious project, the European Green Deal, which aims to lead the European Union to climate neutrality by 2050. This is a significant challenge for all EU countries, and especially for Poland. The role of hydrogen in the processes of decarbonization of the economy and transport is being discussed in many countries around the world to find rational solutions to this difficult and complex problem. There is an ongoing discussion about the hydrogen economy, which covers the production of hydrogen, its storage, transport, and conversion to the desired forms of energy, primarily electricity, mechanical energy, and new fuels. The development of the hydrogen economy can significantly support the achievement of climate neutrality. The belief that hydrogen plays an important role in the transformation of the energy sector is widespread. There are many technical and economic challenges, as well as legal and logistical barriers to deal with in... [more]

This paper presents an algorithm for finding the optimal control for a current controller that operates as a part of a control system of a shunt active power filter. The algorithm is based upon the Karush−Kuhn−Tucker conditions for finding an optimal value where control signal is limited and constraints create a cube. The explicit solution of the Karush−Kuhn−Tucker problem is presented and simplified calculations are given to lower calculation complexity. The presented Karush−Kuhn−Tucker algorithm is compared with a classical PI controller. It is given the algorithm for finding the optimal parameters of the PI controller and the behavior of the PI controller is compared with the presented algorithm. Attention has been paid to the saturation of controllers in commutation states of load currents, which has a negative impact on the final performance of the controllers and the controlled shunt active power filter. The paper also presents the software and hardware platforms applied to run t... [more]

An overlap auxiliary ventilation system is very often used for driving roadways in methane-rich coal seams. An overlap zone between the outlets of the forcing duct ends with a whirl flow air-duct (WFAD) and the exhaust duct ends with a dust scrubber that is created by applying the overlap system. This study examines the distribution of methane concentrations at various distances in the overlap zone. Maintaining a long overlap zone could increase the advance of the face. Therefore, the impact of overlap zone length on the methane concentration distribution, in and beyond the overlap zone, is investigated. The evaluation of methane concentrations is performed utilizing a well-established computational fluid dynamics (CFD) approach. The mathematical model of methane emissions into the roadway is adopted. Moreover, the CFD model is validated. A vortex of the return air, caused by the free airstream flowing out of the dust scrubber, is found. This air vortex is responsible for higher methan... [more]

The efficiency and power density improvement of power switching converters play a crucial role in energy conversion. In the field of motor control, this requires an increase in the converter switching frequency together with a reduction in the switching legs’ dead time. This target turns out to be complex when using pure silicon switch technologies. Gallium Nitride (GaN) devices have appeared in the switching device arena in recent years and feature much more favorable static and dynamic characteristics compared to pure silicon devices. In the field of motion control, there is a growing use of GaN devices, especially in low voltage applications. This paper provides guidelines for designers on the optimal use of GaN FETs in motor control applications, identifying the advantages and discussing the main issues. In this work, primarily an experimental evaluation of GaN FETs in a low voltage electrical drive is carried out. The experimental investigation is obtained through two different ex... [more]

Due to increasing concern over global warming, the penetration of renewable energy in power systems is increasing day by day. Gencos that traditionally focused only on maximizing their profit in the competitive market are now also focusing on operation with the minimum pollution level. The paper proposes a multiobjective model capable of finding a set of trade-off solutions for the joint optimization problem, considering the cost of reserve and curtailment of power from renewable sources. Managing a hybrid power system is a challenging task due to its stochastic nature mixed with the objective function and complex practical constraints associated with it. A novel metaheuristic Equilibrium Optimizer (EO) algorithm incepted in the year 2020 utilizes the concept of control volume and mass balance for finding equilibrium state is proposed here for computing the optimal schedule and impact of renewable energy integration on profit and emission for different optimization objectives. In this... [more]

Eco-certification schemes are usually launched with various incentives provided by local governments to facilitate green building development and building energy retrofits. A number of barriers to building energy retrofitting have been identified in previous literature, while the barriers to the eco-certification of existing buildings are under-researched. Drawing on a set of building data retrievable from the BEAM Society and other sources, we carried out an analysis and found the building energy retrofitting, as well as the certification process, were unwelcomed in multi-owned residential buildings. The identified shortfall is put forward from the perspectives of transaction cost theory and agency theory. The findings reveal that high transaction costs incurred during negotiations and coordination among a large number of co-owners within a typical apartment building can outweigh the benefits of retrofitting and eco-certification. Besides, the remuneration structure of third-party pro... [more]

As Canadian crude bitumen production from oil sands has increased in recent decades, the nation’s oil and gas industry has become a significant contributor to national greenhouse gas emissions. Canada has developed carbon emission reduction targets to meet its Nationally Determined Contributions and Mid-Century Strategy goals. A detailed profile of energy consumption pathways in the oil sands industry is necessary to identify potential areas of improvement and to monitor progress toward meeting emissions reduction targets. Much of the existing literature for oil sands modeling provides input assumptions with different technological boundaries. For a set of oil sands extraction and upgrading technologies, this study first reviews the literature and then quantifies energy input requirements, CO2 emissions, and operating costs for a set of consistent technological boundaries and energy units. Summary results refer to requirements and costs at the production facility, excluding transportat... [more]

The intermittent nature of renewable sources, such as solar and wind, leads to the need for a hybrid renewable energy system (HRES) that can provide uninterrupted and reliable energy to a remote and off-grid location with the use of a biogas generator and battery. In the present study, conventional PV panels have been integrated with phase change material (PCM) for power enhancement. In addition, various configurations (i. PV-Wind-Battery system, ii. PV-PCM-Wind-Battery, iii. PV-Wind-Biogas-Battery and iv. PV-PCM-Wind-Biogas-Battery) have been compared for the hot and humid climatic location of Chennai, India. Optimization has been carried out to minimize the cost of energy and the net present cost has also been computed. It has been found that the integration of PCM with the PV-Wind-Biogas-Battery-based off-grid system results in savings of USD 0.22 million in terms of net present cost and reduces the cost of energy from USD 0.099/kWh to USD 0.094/kWh. Similarly, for another off-grid... [more]

In this paper, a new, state space, fractional order model of a heat transfer in two dimensional plate is addressed. The proposed model derives directly from a two dimensional heat transfer equation. It employes the Caputo operator to express the fractional order differences along time. The spectrum decomposition and stability of the model are analysed. The formulae of impluse and step responses of the model are proved. Theoretical results are verified using experimental data from thermal camera. Comparison model vs experiment shows that the proposed fractional model is more accurate in the sense of MSE cost function than integer order model.

Since microgrids should be able to smoothly operate in two distinct modes—grid-connected and islanded, their fault currents can widely fluctuate depending on the operational mode. When the microgrid is connected to the grid, the highest fault current, by far, is supplied by the utility grid. In this mode, the fault current contribution from distributed energy resources (DERs) is less than 20%. However, when the microgrid switches to the islanded mode, the fault current contribution from the utility grid is lost and DERs are the sole fault current sources. Thus, the overall fault current in the islanded mode is multiple times lower when compared to the grid connected mode. Moreover, most of the DERs are inverter-based, with limited fault currents, which further reduces the overall fault current in the islanded mode. With the rapid rise of the microgrid penetration around the globe, this phenomenon can adversely influence the relay protection, and thus the microgrid fault current needs t... [more]

The links of low power wireless sensor networks are error prone and the transmission on a wireless link is determined probabilistically by the packet reception rate (PRR) of the link. On the other hand, there is a very strict requirement in the end-to-end reliability and delay of sensor data in industrial wireless sensor networks (IWSNs). The existing approaches to provide the end-to-end reliability in IWSNs is retransmitting the packet when failure occurs. These approaches transmit a packet multiple times in successive time slots to provide the required reliability. These approaches, however, can increase the average delay of packets and the number of packets buffered in a queue. This paper proposes a new scheme to estimate the probabilistic amount of packets, called queue level (QL), in the buffer of each node based on the PRRs of the wireless links. This paper also proposes a QL-based centralized scheduling algorithm to assign time slots efficiently in TDMA-based IWSNs. The proposed... [more]

The paper is a comprehensive laboratory comparison study of two galvanic isolated solution off-board battery chargers: (1) Si-based cost-effective case, and (2) SiC-bidirectional ready for vehicle to grid concept case. All circuits are modular, and in both cases the DC/DC converter can be replaced according to the end user requirements (the coupled transformer remains the same and is constructed based on 12xC100 cores to avoid additional choke). In the case of single active bridge, an active RCD snubber is proposed to protect against overvoltage above 1kV in the DC_2 circuit. The dual active bridge is equipped with soft-star modulation using a zero vector to reduce in-rush current in case of no-load operation, while the AC/DC grid connected converter remains bidirectional to assure the highest power quality at the point of common coupling. All tests were made with real second-used batteries, which improves environmental, economic and technical feasibility of such systems for prosumers.... [more]

The possibility for spatial and temporal monitoring of environmental, chemical or thermal processes is of high importance for their better understanding thus control and optimization. Therefore, measurement methods that enable such opportunities might be especially valuable for researchers and process engineers. For this reason, in this paper the novel Electrical Impedance Tomography system is proposed that enables the visualization of the processes in which the electrical conductivity of material is changing. The proposed EIT system is based mostly on general purpose equipment. It consists of three laboratory-grade devices: a signal generator, a switching device and a data acquisition card for voltage measurement. In addition to those devices, the current source was constructed to complete the system. The EIT system was designed to have the ability of sourcing the current of frequency up to 250 kHz. A set of validation experiments were carried out to verify the EIT system accuracy. Th... [more]

A new porous system in power plants allowing the management of the crisis of heat exchange at boiling water in porous structures has been investigated. This study refers to the thermal power plants of electrical power stations and devices for cutting natural and artificial mineral media. Combustion chambers and supersonic nozzles were cooled by different porous structures. The optimum cell sizes of the porous structures were determined and data on the heat transfer capacity for the (critical) heat flow were obtained. A thermal device in the form of a rocket-type burner with a detonation jet showed high efficiency for capillary-porous and flow-through cooling systems. The economic effect per burner is not less than 200−300 dollars, and the coolant consumption is reduced by dozens of times, which is environmentally important. A comparative evaluation of the investigated structures and coatings has advantages over other cooling systems. The integration of mesh structures with capillary-po... [more]