To further implement decentralized renewable energy resources, blockchain based peer-to-peer (P2P) energy trading is gaining attention and its architecture has been proposed with virtual demonstrations. In this paper, to further socially implement this concept, a blockchain based peer to peer energy trading system which could coordinate with energy control hardware was constructed, and a demonstration experiment was conducted. Previous work focused on virtually matching energy supply and demand via blockchain P2P energy markets, and our work pushes this forward by demonstrating the possibility of actual energy flow control. In this demonstration, Plug-in Hybrid Electrical Vehicles(PHEVs) and Home Energy Management Systems(HEMS) actually used in daily life were controlled in coordination with the blockchain system. In construction, the need of a multi-tagged continuous market was found and proposed. In the demonstration experiment, the proposed blockchain market and hardware control int... [more]

With the rapidly evolving mobile technologies, the number of cellular base stations (BSs) has significantly increased to meet the explosive demand for mobile services and applications. In turn, this has significantly increased the capital and operational expenses, due to the increased electricity prices and energy consumption. To generate electricity, power plants mainly rely on fossil fuels, which are non-renewable energy resources. As a result, CO2 emissions also increase, which adversely affect health and environment. For wireless access technologies and cellular networks, BSs are the largest power consumer, and the network energy consumption is mainly dominated by the network infrastructure, which makes the telecommunications sector liable for energy consumption as well as CO2 emissions around the globe. Alternatively, solar energy is considered as an eco-friendly and economically attractive solution, due to its cost-effectiveness and sustainability. In this paper, the potentials o... [more]

As a result of lightning strikes, pollution, and ice, overhead distribution wires might be short-circuited and trip. As a result, researchers have developed a new lightning protection composite insulator. There is still a need to test its pollution and icing performance. Based on the finite element and field test method, this paper studies the electric field distribution and AC (Alternating Current) breakdown characteristics of polluted novel lightning protection insulators under icing conditions. Firstly, the finite element calculated results show that this novel insulator’s electric field distribution is different from that of a conventional insulator. The locations with sizeable electric fields are located in the insulation section, and the electric field in the arrester section is tiny. In addition, when the insulator surface is covered with ice, there is an increase in the electric field along the surface and pin electrodes. Compared with the dry conditions, when there is an ice l... [more]

Different fluid compositions have been considered as heat transfer fluids (HTF) for concentrating solar power (CSP) applications. In linear focusing CSP systems synthetic oils are prevalently employed; more recently, the use of molten salt mixtures in linear focusing CSP systems has been proposed too. This paper presents a comparative assessment of thermal oils and five four nitrate/nitrite mixtures, among the ones mostly employed or proposed so far for CSP applications. The typical medium-size CSP plant (50 MWe) operating with synthetic oil as HTF and the “solar salt” as TES was considered as a benchmark. In the first part of the paper, physical properties and operation ranges of different HTFs are reviewed; corrosion and environmental issues are highlighted too. Besides an extensive review of HTFs based on data available from the open literature, the authors report their own obtained experimental data needed to thoroughly compare different solutions. In the second part of the paper,... [more]

Slow steaming is an operational measure in ocean-going vessels sailing at slow speeds. It can help climate mitigation efforts by cutting down marine fuel consumption and consequently reducing CO2 and other Greenhouse Gas Emissions (GHG). Due to climate change both the European Union (EU) and the International Maritime Organization (IMO) are analysing the inclusion of international shipping in the EU Emissions Trading System (ETS) in the near future or alternatively implementing a carbon tax. The paper proposes a methodology to decide the optimal speed of a vessel taking into account its characteristics and the factors that determine its economic results. The calculated cash flow can be used in valuation models. The methodology is applied for a case study for any container ship in a range from 2000 to 20,000 Twenty-foot Equivalent Units (TEU) on a leg of a round trip from Shanghai to Rotterdam. We calculate how speed reduction, CO2 emissions and ship owner’s earnings per year may vary b... [more]

The solidification process in a multi-tube latent heat energy system is affected by the natural convection and the arrangement of heat exchanger tubes, which changes the buoyancy effect as well. In the current work, the effect of the arrangement of the tubes in a multi-tube heat exchanger was examined during the solidification process with the focus on the natural convection effects inside the phase change material (PCM). The behavior of the system was numerically analyzed using liquid fraction and energy released, as well as temperature, velocity and streamline profiles for different studied cases. The arrangement of the tubes, considering seven pipes in the symmetrical condition, are assumed at different positions in the system, including uniform distribution of the tubes as well as non-uniform distribution, i.e., tubes concentrated at the bottom, middle and the top of the PCM shell. The model was first validated compared with previous experimental work from the literature. The resul... [more]

The purpose of this paper is a multidimensional assessment of the diversification of economic development in EU countries in the context of the progress in the implementation of the concept of sustainable development in 2014 and 2019. The issues discussed in this article are topical and important, given that the spatial disparity of economic development in the EU has never been so pronounced as it is today. While there is a wealth of studies on economic development in the literature, research on the comprehensive approach to this problem in the relation of sustainable development appears to be rather scarce. The article emphasizes the role of energy in economic growth. Authors used taxonomic measures. They were constructed on the basis of selected methods of multidimensional comparative analysis. By using the Hellwig method and the TOPSIS method, taxonomic measures were constructed, and linear ordering of the EU countries was carried out. In addition, using the so-called threshold meth... [more]

Particulate emission from internal combustion engines is a complex phenomenon that needs to be understood in order to identify its main factors. To this end, it appears necessary to study the impact of unburned gases, called blow-by gases, which are reinjected into the engine intake system. A series of transient tests demonstrate their significant contribution since the particle emissions of spark-ignition engines are 1.5 times higher than those of an engine without blow-by with a standard deviation 1.5 times greater. After analysis, it is found that the decanter is not effective enough to remove completely the oil from the gases. Tests without blow-by gases also have the advantage of having a lower disparity, and therefore of being more repeatable. It appears that the position of the “endgap” formed by the first two rings has a significant impact on the amount of oil transported towards the combustion chamber by the backflow, and consequently on the variation of particle emissions. Fo... [more]

This paper addresses the challenge of minimizing training time for the control of Heating, Ventilation, and Air-conditioning (HVAC) systems with online Reinforcement Learning (RL). This is done by developing a novel approach to Multi-Agent Reinforcement Learning (MARL) to HVAC systems. In this paper, the environment formed by the HVAC system is formulated as a Markov Game (MG) in a general sum setting. The MARL algorithm is designed in a decentralized structure, where only relevant states are shared between agents, and actions are shared in a sequence, which are sensible from a system’s point of view. The simulation environment is a domestic house located in Denmark and designed to resemble an average house. The heat source in the house is an air-to-water heat pump, and the HVAC system is an Underfloor Heating system (UFH). The house is subjected to weather changes from a data set collected in Copenhagen in 2006, spanning the entire year except for June, July, and August, where heat is... [more]

The battery impedance is an important indicator of battery health status. In this paper, a magnetic coupling-based impedance measurement method for electrochemical batteries is proposed. Without affecting the energy injection stage, the designed suppression resistance can minimize the influence of the primary circuit response, and the under-damped oscillation waveform containing the battery impedance information can be directly obtained on the primary inductance. The change of the mutual inductance value within a certain range will not affect the measurement results. Therefore, the measurement system has high stability and robustness. By utilizing the discrete Fourier transform (DFT)-based algorithm to calculate the damped oscillation parameters, the battery impedance is accurately derived from the calculated attenuation coefficient and damped oscillation frequency. The accuracy of this method under different coupling parameters is analyzed and verified by simulation and experiment on... [more]

The aerospace industry is increasingly transitioning from hydraulic and pneumatic drives to power-electronic based drive systems for reduced weight and maintenance. Electromechanical thrust reverse actuation systems (EM-TRAS) are currently being considered as a replacement for mechanical based TRAS for future aircraft. An EM-TRAS consists of one or more power-electronic drives, electrical motors, and gear-trains that extend/retract mechanical members to produce a drag force that decelerates the aircraft upon landing. The use of a single (“central”) power electronic converter to simultaneously control a set of parallel induction machines is a potentially inexpensive and robust method for implementing EM-TRAS. However, because the electrical motors may experience different shaft torques—arising from differences in wind forces and a flexible nacelle—a method to implement rotor position synchronization in central-converter multi-motor (CCMM) architectures is needed. This paper introduces a... [more]

Using Electric Vehicles (EV) as Flexible Resources (FR) to increase surplus Photovoltaic (PV) power utilisation is a well-researched topic. Our previous study showed that EVs are viable as supplementary FRs in large capacity PV power systems, where EVs are likely to gather (i.e., workplaces). However, that study assumed all EVs to have identical arrival and departure times (availability), and battery capacities. As these characteristics may vary between EVs and affect their performance as FRs, this study expands the modelling of EVs to consider a variety of availabilities and battery capacities. To effectively utilise a variety of EVs as FRs, an Optimisation Electric-load Dispatching model is used to formulate priority schemes for charging and discharging the EVs based on their potential to contribute to the power system. The priority schemes are evaluated by simulating the annual operation of the power system both with and without the priority schemes, and comparing results. The power... [more]

Refracturing treatment is an economical way to improve the productivity of poorly or damaged fractured horizontal wells in tight reservoirs. Fracture reorientation and fracture face damage may occur during refracturing treatment. At present, there is still no report on the rate decline solution for refractured horizontal wells in tight reservoirs. In this work, by taking a semi-analytical method, traditional rate decline and Blasingame-type rate decline solutions were derived for a refractured horizontal well intercepted by multiple reorientation fractures with fracture face damage in an anisotropic tight reservoir. The accuracy and reliability of the traditional rate decline solution were verified and validated by comparing it with a classic case in the literature and a numerical simulation case. The effects of fracture reorientation and fracture face damage on the rate decline were investigated in depth. These investigations demonstrate that fracture face damage is not conducive to i... [more]

The flyback converter has been widely used in Photovoltaic microinverters, operating either in Discontinuous, Boundary, or Continuous Conduction Mode (DCM, BCM, CCM). The recently proposed hybrid DBCM operation inherits the merits of both DCM and BCM. In this work, the necessary analytical equations describing the converter operation for any given condition under DBCM are derived, and are needed due to the hybrid nature of the modulation strategy during each sinusoidal wave. Based on this analysis, a design optimization sequence used to maximize the weighted efficiency of the inverter under DBCM is then applied. The design procedure is based on a power loss analysis for each converter component and focuses on the appropriate selection of the converter parameters. To achieve this, accurate, fully parameterized loss models of the converter components are implemented. The power loss analysis is then validated by applying the optimization methodology to build an experimental prototype oper... [more]

Free convective heat transfer in the closed gap between concentric semi-hemispheres is quantified by means of a numerical approach based on the volume control method using the SIMPLE algorithm. The average Nusselt number is determined for several configurations obtained by varying the cavity’s aspect ratio between 0.15 and 1.5, while the Rayleigh number varies within the 5.33 × 103−4.50 × 108 range. The results show that the correlations available in the literature dealing with concentric whole spheres cannot be used for the configuration treated here. The new correlation between the Nusselt and Rayleigh numbers proposed in this work can be applied in various engineering sectors, such as in the electronic packaging considered in this present work, buildings, and architecture.

Microgrids are empowered by the advances in renewable energy generation, which enable the microgrids to generate the required energy for supplying their loads and trade the surplus energy to other microgrids or the macrogrid. Microgrids need to optimize the scheduling of their demands and energy levels while trading their surplus with others to minimize the overall cost. This can be affected by various factors such as variations in demand, energy generation, and competition among microgrids due to their dynamic nature. Thus, reaching optimal scheduling is challenging due to the uncertainty caused by the generation/consumption of renewable energy and the complexity of interconnected microgrids and their interplay. Previous works mainly rely on modeling-based approaches and the availability of precise information on microgrid dynamics. This paper addresses the energy trading problem among microgrids by minimizing the cost while uncertainty exists in microgrid generation and demand. To th... [more]

Adsorption cooling technologies driven by low-grade thermal or solar power are used as an energy-efficient alternative to conventional refrigeration and air conditioning systems. Explicit understanding of the adsorption cycles requires precise determination of the performance parameters, replication of the experimental data, and the rigorous study of the adsorption heat transformation method. Hence, the optimum adsorption isotherms model must be identified. Scientists often face difficulties in selecting the suitable isotherm model as there are many models for a particular form of adsorption isotherm. The present study introduces a novel approach for choosing the optimal models for each type of International Union of Pure and Applied Chemistry (IUPAC) classified adsorption isotherm using robust statistical methods. First, the box-and-whisker plots of error identification are employed. Tóth for Type-I(a) and Type-I(b), modified BET for Type-II, GAB for Type-III, Universal for Type-IV(a)... [more]

The purpose of the following paper is to present the author’s experimental field investigations of a jointless railway track subjected to a generated imperfection and analysis of track response to applied static loads. An optical measurement system, Pontos, was used for the static and dynamic analysis of the track’s deflections in 3D. The investigations allow us to recommend a direct application of this system for the non-contact measurement, visualization and analysis of simulated defects in the jointless track, as presented by the author. It is stated that simulation of an effect called the hanging sleeper, a short irregularity in the railway track with the initial parameters provided (a gap and a length of irregularity), is possible. The proposed method, based on the measurement in the loaded track (a static load from the locomotive wheels), allows for a description of the effect of the changing track support condition. Moreover, it also proves its usefulness for the analysis of the... [more]

This paper presents a study on the application of a ceramic filter in the biomass gasification process and its efficiency in particulate matter removal from the process gas and flue gas. A significant advantage of this type of filter is its high efficiency in small particle removal (<1 µm). This feature allows us to reach the much lower emissions that are required by the applicable standards. The study was performed using an original biomass gasification installation, where conifer scobs were used as feedstock. The installation, its operation and measurement methodology are described in the article. The study included the analysis of process gas and particulate matter, as well as particulate matter content before and after the filter was applied. The measurements indicate that the efficiency of particulate matter removal reaches 99.1%. The analysis of particulate matter in the process gas allowed us to determine that its content was 18.26%, and additionally it was indicated that it... [more]

The traditional anchoring method of bolts has insufficient control over the surrounding rock of the coal roadway. Based on this background, full-stress anchoring technology of bolts was proposed. Firstly, a mechanical relationship model of a bolt-drawing, anchoring interface was established to obtain the equations of the axial force and obtain shear stress distribution as well as the decreasing-load transfer law of the anchoring section of bolts. Through studying the prestress-loading experimental device of bolts, we found that increasing the initial preload could increase the axial force under the same conditions and the retarded anchoring section could control the axial-force loss of bolts in the middle of the anchoring section. Under the full-stress anchoring mode, the effect of applying a pre-tightening force was better than that of applying a pre-tightening force under traditional anchoring methods. Moreover, FLAC3D (Fast Lagrangian Analysis of Continua 3D; ITASCA (Ita sca Interna... [more]

Forecasting the electricity price and load has been a critical area of concern for researchers over the last two decades. There has been a significant economic impact on producers and consumers. Various techniques and methods of forecasting have been developed. The motivation of this paper is to present a comprehensive review on electricity market price and load forecasting, while observing the scientific approaches and techniques based on wind energy. As a methodology, this review follows the historical and structural development of electricity markets, price, and load forecasting methods, and recent trends in wind energy generation, transmission, and consumption. As wind power prediction depends on wind speed, precipitation, temperature, etc., this may have some inauspicious effects on the market operations. The improvements of the forecasting methods in this market are necessary and attract market participants as well as decision makers. To this end, this research shows the main var... [more]

Sustainability and decarbonisation are buzzwords in today’s economy. The fossil fuel sector has had a great impact on development of many countries and it is interesting how this sector is going to survive in the era of climate neutrality imposed by the European and national decarbonisation policies. PKN Orlen is one of the largest industrial corporations in Poland and Central Europe representing the energy and fossil fuel sector. The article sets out to identify the main areas of PKN Orlen’s strategic plans resulting from the energy transition process in Poland. For this reason, the research question posed in this study is: to what extent and in what direction has Poland’s energy policy influenced the new strategy of PKN Orlen? Poland’s most recent energy policy was adopted in 2021, therefore an attempt to assess the impact of this policy on the strategy of a large player in the fossil fuel sector in such a short time horizon proves the originality of the study. The applied methodolog... [more]

Remuneration policy is an element of company management. Remuneration systems should be flexible and evolutionary. They must consider not only the changes in the external environment but, most of all, the changing needs of the internal environment. In practice, this means aligning the company’s strategy and goals with the remuneration system. What is more, the remuneration policy must be consistent with all personnel substrategies, which should systematically create integrated human capital management. The aim of our research was to determine how employees perceive the appropriate structure of remuneration and how the relationships between the elements that make up the structure of remuneration are perceived. Energy sector employees were selected for the study, dividing the group of respondents by gender, age and level of education. The obtained data were submitted to multivariate correspondence analysis. The analysis of the perception map for the variables of gender, age and education... [more]

A bus seat needs to be designed ergonomically for better seating comfort. The present study is intended to develop a cost-effective ergonomic bus seat design based on seat comfort and safety demands. As part of the proposed seat design procedure, seating comfort analysis, identifying preferred design features, and developing a seat design are included. An analysis of the bus seat back and seat pan profiles was conducted. Based on the results of the comfort analysis, the authors identified the preferred design features of bus seats during the design identification process. An improved bus seat prototype was developed based on selected design features in the design development stage. Seating comfort analyses were used to compare the achieved seat with the reference seat. The seat design developed in the present study may be applicable for various types of bus public transport.

A clear gap was identified in the literature regarding the in-depth evaluation of scaling up thermal energy storage components. To cover such a gap, a new methodological approach was developed and applied to a novel latent thermal energy storage module. The purpose of this paper is to identify some key aspects to be considered when scaling up the module from lab-scale to full-scale using different performance indicators calculated in both charge and discharge. Different normalization methods were applied to allow an appropriate comparison of the results at both scales. As a result of the scaling up, the theoretical energy storage capacity increases by 52% and 145%, the average charging power increases by 21% and 94%, while the average discharging power decreases by 16% but increases by 36% when mass and volume normalization methods are used, respectively. When normalization by the surface area of heat transfer is used, all of the above performance indicators decrease, especially the av... [more]