The progressive use of renewable energy sources to ensure a continuous and abundant energy supply is the significant target towards a sustainable and secure energy system. Previously, the countries that had relied on fossil fuel as a dominating energy source are now endorsing energy system transition towards renewable energy sources. In this study, a comparative assessment of the energy problems of South Asian countries is summarized. Nevertheless, there are many similarities and differences in the electricity supply system of these countries. Long-term planning for renewable energy development is suggested for a diverse population and dispersed geographical location considering all the significant challenges. However, appropriate schemes are imperative for integrating significant renewable energy sources. This study introduces a foresight plan of the electricity model according to the demand and supply balance for extensive technical analysis. The EnergyPLAN modeling tool was employed... [more]

The efficient recovery of low temperature waste heat, representing from 25% up to 55% of the energy losses in industrial processes, still remains a challenge and even Organic Rankine Cycles (ORCs) experience a strong efficiency decay in such a low temperature operating range (T < 150 °C). In similar heat transfer processes, several nanofluids have been proposed as a solution for increasing heat transfer efficiency, but they produced only moderate enhancements of the heat transfer efficiency in comparison with pure fluids. This paper aims at numerically assessing the potential gain in efficiency deriving from the application of an unconventional type of nanoparticles, the metal-organic heat carriers (MOHCs), in the ORC field. In comparison with standard nanoparticles, these MOHCs make it possible to extract additional heat from the endothermic enthalpy of desorption, with a theoretically high potential for boosting the heat transfer capacity of ORC systems. In this paper a numerical... [more]

The shift from an industrial to a post-industrial economic system encourages an alternative to the globalized food chains—short food supply chain initiatives, which come alongside the servitization concept and are often discussed in the context of sustainability. However, short food supply chain literature is mainly focused on the aspects typical of the industrial economic system and neglects new important business drivers arising in the post-industrial era. This research aims to discuss the evolution of short food supply chain theory and practice in the context of three paradigm innovations that emerged in the post-industrial economic system and suggest new paths for sustainable agri-food system building. All three paradigm innovations are closely related to each other, but each changes a certain dimension of the mental model concerning the food production and delivery system. The article examines the organizational model of the alternative local food market in Lithuania that has been... [more]

The hazards caused by gas explosion are mainly due to high temperatures and shock waves. It is of great practical significance to explore a device that can restrain these two hazards at the same time. Through the establishment of the gas explosion calculation model, a numerical analysis of the flame propagation in the three types of pipelines, including the empty pipe, the single metal foam pipe, and the high-temperature heat pipe metal foam composite structure, was carried out. The numerical results are compared with the relevant experimental results. The accuracy, rationality, and accuracy of the calculation model is verified. The research results show that that the gas explosion flame propagation develops fastest and accelerates in the empty pipe, followed by a single metal foam pipe. The gas explosion flame in the pipe with the high-temperature heat pipe metal foam composite structure develops the slowest. The composite structure composed of the high-temperature heat pipe and metal... [more]

As an important component of vehicle design and energy conservation, electric vehicle dynamics simulation is essential, especially under complicated testing conditions. The current commercial vehicle simulation software is mostly used for fuel vehicle dynamics simulation, which lacks accurate electric powertrain parts and open sources. To address this problem, this paper proposes an open-source and flexible vehicle dynamics simulation platform that includes 27 degrees of freedom (DOFs) based on Simulink, which can compatibly support both traditional vehicle dynamics simulations and electric vehicle dynamics simulations. In addition, the platform can support module customization, which is convenient for researchers. Although this platform still needs some iterations to reach industrial and commercial standards, it can already achieve parameter consistency under the stability demands in general scenarios. We believe this work should receive research attention and participation to provide... [more]

A three-dimensional numerical investigation of turbulent heat transfer and fluid flow characteristics of the new heat exchanger and self-support of a rectangular converging-diverging (SS-RCD) tube bundle heat exchanger with different inserts was performed. The values of the Reynolds number varied from 27,900 to 41,900. The baseline case (without an insert) was compared with two enhanced configurations: one circular hole in the baffle plate (one-circle case) and a rectangular hole in the baffle plate (one-rectangle case). Compared with the baseline case, the airside Nusselt number (Nu) of the enhanced cases improved by 39.6~48.0% and 36.2~40.2% and had an associated friction factor (f) penalty increase of 53.9−66.7% and 60.7−77.8%, respectively. The baseline case was compared with three enhanced configurations: one-circle case, two-circle case, and three-circle case baffle plate. Compared with the baseline case, Nu of the enhanced cases improved by 39.6−48.0%, 36.2−45.4%, and 35.0−44.2%... [more]

The essence of the research was to model the actual energy storage system obtained from photoelectric conversion in a phase change accumulator operating in a foil tunnel. The scope of the work covered the construction of four partial models, i.e., electricity yield from solar radiation conversion for three types of photovoltaic cells (mono- and polycrystalline and CIGS), energy storage in a PCM battery, heat losses in a PCM battery and energy collection from photoelectric conversion in PCM battery. Their construction was based on modelling methods selected on the basis of literature review and previous analyses, i.e., artificial neural networks (ANN), random forest (RF), enhanced regression trees (BRT), MARSplines (MARS), standard multiple regression (SMR), standard C&RT regression trees (CRT), exhaustive CHAID for regression (CHAID). Based on the analysis of the error values (APE, MAPE, ΔESR), the best quality models were selected and used in the further part of the work. Based on the... [more]

In this paper, a novel extended permanent magnet synchronous motor model is presented that incorporates a quadratic flux-current function to represent the polarity-dependent saliency. The proposed model enables the design of sensorless polarity detection algorithms required by the initial position detection of permanent magnet synchronous motors. The novelty of the model is that it integrates the polarity-dependent saliency into the traditional machine model and introduces a new machine parameter, the polarity-dependent saliency coefficient, to specify the Hessian matrix of the flux-current function. A measurement method is presented for determination of the elements of the Hessian and the polarity-dependent saliency coefficient. The solution of the model is given for high-frequency sinusoidal pulsating voltage injection. Experimental results show that the proposed extended model accurately predicts the amplitudes and phases of the second harmonics of the motor currents, which are the... [more]

Modeling of hysteresis loops may be useful for the designers of magnetic circuits in electric machines. The present paper focuses on the possibility to apply the Harrison model to describe hysteresis loops of grain-oriented electrical steel subject to compressive stress. The model extension is achieved by introduction of an additional term into the equation that describes irreversible magnetization process. The extension term does not include a product of stress and magnetization, as could be anticipated from Sablik’s theory, applicable, e.g., to the Jiles−Atherton model. The present contribution points out the fundamental differences between the two aforementioned modeling approaches, which are based on different philosophies despite some apparent similarities. The modeling results are in a qualitative agreement with the experimental results obtained from a single sheet tester for a representative commercially available grain-oriented electrical steel grade 0.27 mm thick.

Hydropower depends on the elevation head and water flow of a river. However, other factors must be considered, such as the risk associated with surface processes and environmental factors. The study aims to analyze a landscape’s dynamics and locate potential sites for small-scale hydropower systems (<10 MW) using a geographic information system, the curve number method, and the TopoToolbox with a digital elevation model and available spatial datasets. Across Bohol Island in the central Philippines, the study found 94 potential sites with hydraulic heads ranging from 20−62.4 m, river discharges between 0.02 to 9.71 m3/s, and a total hydropower capacity of 13.595 MW. The river profile analysis classified the sites to five levels of risk to geo-hazards, with three-fourths of the sites being at ‘high’ to ‘very high’ risk levels while more than 50% of the total power can be generated in ‘low’ risk areas. Land-use and population constraints reduced the sites to 25 and the hydropower capac... [more]

The aim of this study was to check whether the data recorded by a bicycle computer paired with typical measurement sensors can be useful for a scientific evaluation of the cyclist−bicycle anthropotechnical system, including electric bicycles. The problem arose when the authors searched for methods to assess the energy efficiency of electric bicycles and intelligent power management systems provided by the assistance system, in accordance with the current needs of the bicycle user. This can be of great importance in the efficient use of electric bicycles and their batteries, in the event that they are rented in public access systems. This article focuses primarily on data on bicycle speed, calculated by the GPS module or obtained from speed sensors, as well as data from the cadence sensor, power measurement, pedaling technique and heart rate. An attempt was made to evaluate the correctness and consistency of the data recorded by the computer through various types of comparatives analyse... [more]

Several techniques for cooling mass concrete structures were developed in order to increase structural integrity and reduce the influence of cement hydration, which sometimes causes cracking in concrete structures, negatively affecting their durability. This research focuses on cooling system design, initial investment, and the influence of different refrigerants on cooling system performance aims in producing higher quality massive concrete. Cooling aggregates in massive concrete structures such as desert dams can be performed by employing cooled air from an air conditioning duct system or chilled water. The experimental study illustrates the relationship between the coefficient of performance COP, the evaporator temperature, cooling capacity, and refrigerant mass flow rate as a function of the evaporator temperature, cooling capacity, and refrigerant mass flow rate. The findings of the experiments were utilized to verify a numerical model developed utilizing engineering equation solv... [more]

Field approaches are employed to develop a mathematical model of a power network section. The facility consists of two electric power subsystems described with ordinary differential equations and presented as concentrated parameter systems connected with a three-phase power supply line, presented as a distributed parameter system. The model of the electric power line is described with partial differential equations. Mathematically, the supply line model is described utilizing a mixed problem with explicitly indefinite boundary conditions. All electromagnetic state equations of the integrated system are introduced in their matrix-vector forms. The equation of the three-phase long supply line is expressed untraditionally as a system of two first-order differential equations as a function of long line voltage. Since the power supply line is part of the integrated system that includes two subsystems, the boundary conditions at the line’s start and end are implicitly defined, avoiding the t... [more]

A thermal network will be presented to model a multi-layer structure consisting of a semiconductor structure, integrated Peltier heat pump and a cooling fin. A criterion will be set up to determine the optimal Peltier current to minimise the chip temperature using the power dissipation as the control parameter. Compared with classical methods, the proposed solution does not show any time delays in response to power changes and is not sensitive to the position of chip temperature sensors. It does not generate chip temperature oscillations. The idea can be applied in each integrated circuit cooled with Peltier heat pumps, e.g., power devices, high-performance processors, high-frequency integrated circuits, etc. The authors present a simple mathematical formula that can be easily implemented in the software of a processor being cooled. As a consequence, the device is able to operate with maximum efficiency assuming required reliability. Theoretical considerations are illustrated by some r... [more]

City buses are one of the main means of public transport in cities. As they move in a limited and densely populated area and are intensively exploited, it is particularly important that they are environmentally friendly. There are many ways to reduce emissions from city buses, including the use of hybrid propulsion. Another way is to use low-emission fuels. This article presents the results of the emission tests of an 18 m articulated city bus with a serial hybrid drive fuelled comparatively by conventional diesel fuel and oxygenated fuel containing 10% v/v of triethylene glycol dimethyl ether (TEGDME). The emission tests were carried out during the actual operation of the bus on a route in Poznań (Poland) and over the SORT cycles. The obtained test results were compared also with the results obtained for a conventional bus. The reduction in emissions of some exhaust components was found when the hybrid bus was fuelled with oxygenated fuel during its actual operation on the bus route.... [more]

This paper conducts an analysis of the aerodynamic influence of different ground and wheel states on the Notchback DrivAer by numerical simulation. The effects of the moving ground and rotating wheels are investigated individually and comprehensively. Experimental data are also included for validation. Through this study, a unique and important low-drag state is observed, in which the vehicle wake near the center region becomes more symmetrical, the pressure on the upper middle base is recovered and the total aerodynamic drag decreases significantly. Furthermore, the formation of this state is determined by the flow rate near the surface of the rear underbody. When the wheels are rotating, the wheel wakes are weakened. On one hand, the drag of wheels and the two sides of the base region is reduced. On the other hand, the boundary layer near the underbody is thinned and the flow near the underbody surface is accelerated, transforming the wake to the low-drag state. Moreover, the moving... [more]

The present paper focuses on nonlinear oscillations of a horizontally supported Jeffcott rotor. An approximate solution to the system of governing equations having quadratic and cubic nonlinearities is obtained in two cases of practical interest: simultaneous and internal resonance. The Optimal Auxiliary Functions Method is employed in this study, and each governing differential equation is reduced to two linear differential equations using the so-called auxiliary functions involving a moderate number of convergence-control parameters. Explicit analytical solutions are obtained for the first time in the literature for the considered practical cases. Numerical validations proved the high accuracy of the proposed analytical solutions, which may be used further in the study of stability and in the design process of some highly performant devices.

E-waste and end-of-life vehicles (ELVs) are fast-growing waste streams in the EU and beyond that require specific collection and treatment activities to avoid environmental pollution and resource depletion fed by the linear economy model. This paper aims to investigate the links between e-waste and ELVs streams and the circular economy approach of the EU. Romania is examined as a relevant case study for the central and eastern European Region regarding: (i) the current e-waste and ELVs management deficiencies and challenges in line with circular economy principles promoted by EU; (ii) analysis of E-waste and ELVs flows data; and (iii) best circular economy initiatives related to e-waste and ELVs in Romania, including the opportunity to create new jobs in treatment activities that the simple operations from the first stages of e-waste recycling can produce locally and regionally in Romania. This work points out the current knowledge gaps and future research directions for these special... [more]

This book contains the successful invited submissions [...]

In order to solve the problem of uneven air inlet flow in the guide channel of autoclave, three optimization schemes for the guide plate were proposed. The flow field in the guide channels of autoclave was simulated and analyzed by the realizable k-epsilon turbulence model and dynamic boundary method. The results show that the three optimization schemes have a certain effect on solving the problem of uneven air inlet flow in each guide channel, but some of them also have some negative effects. The integration of the three optimization schemes effectively increases the total air inlet flow of the guide channels; the increase ratio reaches 4.15%, improves the flow-field characteristics at the outlet of the guide channels and greatly reduces the difference in the air inlet flow in the left and right guide channels; the difference ratio drops from 62.61% to 5.37%.

The Austrian Education Energy Initiative ETSIT has been established as a response to the EU Energy Efficiency Directive and the Austrian Energy Efficiency Act. This paper investigates the energy literacy of its young participants, i.e., 6000 primary and secondary school students altogether, on a cognitive, affective and behavioural level, and it compares the putative energy-saving effectiveness of the workshops to that of conventional energy audits.For the current analysis, data from, 640 students who validly answered an online survey shortly after participating in one of the energy education workshops, and 353 students who validly answered the online survey approximately one year after having participated (overall n = 993) were analysed. The results indicate that ETSIT raises students’ energy literacy on a cognitive, affective and behavioural level with about three-quarters of participants claiming they will positively change their energy consumption behaviour in the future as a resul... [more]

One of the most crucial factors for energy transition and the incorporation of renewable energy sources into the existing energy map is citizen engagement. Local energy communities (LECs), which are cooperative-based coalitions aimed at reducing the carbon footprint of the residential building sector, have received increasing attention in the past decade. This is because residential buildings account for almost half of the total energy consumed worldwide. A resounding 75% of it is used for thermal energy consumption, heating and cooling, cooking and bathing. However, the main focus of the literature worldwide is explicitly on electrical LECs, despite the fact that the significant increase in natural gas and oil prices, creates instability in the heating and cooling prices. The scope of this study is to provide an overview of the research field regarding Thermal LECs, using both a thorough literature review as well as bibliometric analysis (VOSviewer software), in order to validate the... [more]

The long-term hydrothermal scheduling (LTHS) problem seeks to obtain an operational policy that optimizes water resource management. The most employed strategy to obtain such a policy is stochastic dual dynamic programming (SDDP). The primary source of uncertainty in predominant hydropower systems is the reservoirs inflow, usually a linear time series model (TSM) based on the order-p periodic autoregressive [PAR(p)] model. Although the linear PAR(p) can represent the seasonality and autocorrelation of the inflow datasets, negative inflows may appear during SDDP iterations, leading to water balance infeasibilities in the LTHS problem. Different from other works, the focus of this paper is not avoiding negative inflows but instead dealing with the negative values that cause infeasibilities. Hence, three strategies are discussed: (i) inclusion of a slack variable penalized in the objective function, (ii) negative inflow truncation to zero, and (iii) optimal inflow truncation, among which... [more]

The potential of bio-electro-jet fuel (BEJF) production with integration into an existing biomass-based combined heat and power (CHP) facility was investigated. The BEJF is produced via Fischer−Tropsch (F−T) synthesis from biogenic CO2 and H2 obtained by water electrolysis. Techno-economic (TEA)- and life. cycle (LCA)- assessments were performed to evaluate the production cost and environmental impact of the BEJF production route. The BEJF mass fraction reached 40% of the total F−T crude produced. A reduction of 78% in heating demands was achieved through energy integration, leading to an increase in the thermal efficiency by up to 39%, based on the F−T crude. The total production cost of BEJF was in the range of EUR 1.6−2.5/liter (EUR 169−250/MWh). The GWP of the BEJF was estimated to be 19 g CO2-eq per MJ BEJF. The reduction potential in GWP in contrast to the fossil jet baseline fuel varied from 44% to more than 86%. The findings of this study underline the potential of BEJF as a re... [more]

A numerical study was carried out to investigate charging and discharging processes of different phase change materials (PCMs) used for thermal storage in an innovative solar collector, targeting domestic hot water (DHW) requirements. The aim was to study PCMs that meet all application requirements, considering their thermal performance in terms of stored and retrieved energy, outlet temperatures, and water flow rate. Work was carried out for three flat-plate solar panels of different sizes. For each panel, a PCM tank with a heat exchanger was attached on the back plate. Simulations were conducted on a 2D domain using the enthalpy−porosity technique. Three paraffin-based PCMs were studied, two (A53, P53) with phase-change temperatures of approximately 53 °C and one of approximately 58 °C (A58H). Results showed that, during charging, A58H can store the most energy and A53 the least (12.30 kWh and 10.54 kWh, respectively, for the biggest unit). However, the biggest unit, A58H, takes the... [more]