Latent heat storage systems are a promising technology for storing and providing thermal energy with low volume, mass and cost requirements, especially when operated at high temperatures. Metallic phase change materials are particularly advantageous for high thermal input and output, which is especially important for mobile applications. When designing a storage system, it is essential to have precise knowledge about the potential storage capacity. However, the system’s storage capacity is typically calculated from material properties determined at lab scale, although systemic boundary conditions can have a considerable influence. Systemic influences can result from thermal and reactive interfaces or from the storage design. In order to consider these influences, we propose three calorimetric procedures to thermally analyse high-temperature metallic latent energy storage systems at an application scale. We examined the procedures in a transient simulation environment, monitoring the st... [more]

This paper presents a multi-objective optimal rotor design for an interior permanent magnet synchronous motor (IPMSM) based on finite element analysis. Due to the importance of torque characteristic in electromagnetic design of IPMSMs, the main efforts of this study are focused on finding a proper trade-off for its torque profile challenges. In this regard, in order to attain high average torque and low torque ripple, the influence of several key factors, such as the permanent magnet (PM) arrangements, PM positions and PM sizes, are examined. Subsequently, according to the outcomes of the performed sensitivity analysis, the appropriate variation interval of the parameters as well as their initial values is determined. Employing such a deterministic optimization algorithm, which does not need large sample points, minimizes the finite element computational cost and leads to accelerate the convergence process. The two-dimensional finite element model (FEM) of an IPMSM is used to perform a... [more]

Dynamic growth of photovoltaic capacity in Poland encourages many entities to invest in photovoltaic systems. However, in the case of buildings with low roof-bearing capacity it can be problematic or even impossible to mount conventional PV modules due to their relatively high weight. Hence, the use of lightweight PV modules is a potential solution. In this paper four different prototype silicon lightweight modules of novel structure manufactured by the Xdisc S.A have been investigated in terms of their electrical and thermal features. The measurements showed that all prototypes have efficiency exceeding 19.5% and power in range of 214 to 242 Wp at standard test conditions. Their area density is about 3.5 kg/m2 which is typical for lightweight modules. In turn, the Power-to-Weight Ratio exceeds 40 W/kg threshold and in one case reaches almost 58 W/kg. Thanks to the measurements, the prototypes could be modelled in PVsyst (PVsyst SA, Satigny, Switzerland). The performed simulations of a... [more]

The article presents results of research on an adjustable check valve. In particular, the article deals with improvement of flow characteristics and reduction in pressure losses of an existing valve design. The subject of the research was the valve body in the form of a steel block intended for mounting a typical cartridge valve insert. Two variants of the valve body were analysed: a standard one, which is currently in production, and the proposed new solution, in which the geometry was modified based on the results of CFD simulations. The main research task was to properly shape and arrange holes and flow channels inside the body, between the cartridge valve and the connecting plate. Using CFD analyses, a solution for minimising the flow resistance was sought and then the method of modifying flow channels geometry was developed. The CFD simulation results showed a significant reduction in pressure loss, up to 40%. The obtained simulation results were verified on a test bench using a p... [more]

Lithium-ion (Li-ion) batteries play a substantial role in portable consumer electronics, electric vehicles and large power energy storage systems. For Li-ion batteries, developing an optimal charging algorithm that simultaneously takes rises in charging time and charging temperature into account is essential. In this paper, a model predictive control-based charging algorithm is proposed. This study uses the Thevenin equivalent circuit battery and transforms it into the state-space equation to develop the model predictive controller. The usage of such models in the battery optimal control context has an edge due to its low computational cost, enabling the realization of the proposed technique using a low-cost Digital Signal Processor (DSP). Compared with the widely employed constant current-constant voltage charging method, the proposed charging technique can improve the charging time and the average temperature by 3.25% and 0.76%, respectively.

Southeast Asia contains significant natural geothermal resources. However, the mechanism for generating geothermal anomalies by the crust−mantle structure still needs to define. In this study, we focused on Guangdong Province, China. We conducted three magnetotelluric profiles to interpret the crust and upper mantle structure beneath the Guangdong Province and its geothermal implications. Based on data analysis results, a two-dimension inversion was conducted on the dataset. The inversion model revealed that there is a presence of upwelling channels, and some channels are connected with shallow crustal fault zone; the thickness of crust and lithosphere in Guangdong Province is relatively thin. Such a special crust and upper mantle structure form high surface heat flow. Merged with previous research, our results imply that massive Late Mesozoic granites, which contain high radioactive heat generating elements, are distributed on the surface and underground of Guangdong Province. Based o... [more]

This work presents a review of the main topologies of switched capacitors (SCs) used in DC-DC power conversion. Initially, the basic configurations are analyzed, that is, voltage doubler, series-parallel, Dickson, Fibonacci, and ladder. Some aspects regarding the choice of semiconductors and capacitors used in the circuits are addressed, as well their impact on the converter behavior. The operation of the structures in terms of full charge, partial charge, and no charge conditions is investigated. It is worth mentioning that these aspects directly influence the converter design and performance in terms of efficiency. Since voltage regulation is an inherent difficulty with SC converters, some control methods are presented for this purpose. Finally, some practical applications and the possibility of designing DC-DC converters for higher power levels are analyzed.

Automotive thermoelectric generators (ATEGs) are devices used to harvest waste energy from the exhaust gases of internal combustion engines. An ATEG is essentially formed by three main elements: (1) heat absorber in contact with exhaust gases; (2) thermoelectric modules that directly convert heat into electricity; (3) heat sink to increase the heat transfer through the system. Thermoelectric modules (TEM) are commonly based on small-scale commercial units, with tenths of them needed to assemble a full ATEG device. Thus, several thermal and electrical connections between TEMs can be implemented. Previous studies focused on the implications on the output power. Here, we investigated the effects of using different module connections on the energy efficiency and on the electrical outputs (voltage and current). The study was carried out numerically with ATEGs that used from 4 to 100 individual TEMs. Series, parallel and square connections were investigated under two different engine operati... [more]

The characterization of pyrolysis oil obtained from mixed waste plastics and its utilization in a compression ignition engine were investigated. The chemical compositions and physicochemical properties of distilled waste plastic oil (WPO) and crude waste plastic oil (CWPO) were analyzed. The experiment was conducted with a variable compression ratio diesel engine at various loads and compression ratios to evaluate combustion characteristics, exhaust emissions, and engine performance. The experimental results show that CWPO contains the highest percentage of carbon atoms in the C4−C11 group, while WPO contains the highest percentage of carbon atoms in the C12−C20 group, similar to the main compositions of diesel fuel. According to the preliminary study in chemical compositions and physicochemical properties, WPO and diesel fuel were selected for the engine test at different compression ratios of 16, 17, and 18 and different engine operating loads of 25%, 50%, and 75% of maximum engine t... [more]

In alignment with the European Union’s legislation, Greece submitted its final 10-year National Energy and Climate Plan (NECP) in December 2019, setting more ambitious energy and climate targets than those originally proposed in the draft version of the document. Apart from higher penetration of renewable energy sources (RES), the final NECP projects also zero carbon use in power generation till 2030. Although decarbonization has long been regarded beneficial for economies that base their energy production on coal, as it is the case with Greece, the macroeconomic and societal ramifications of faster transitions to carbon-free economies remain highly unexplored. Under this context, in this paper, we soft-link energy models, namely Times-Greece and Primes, with a macroeconomic model, namely Global Trade Analysis Project (GTAP), to measure the effects of the final and draft NECPs on the Greek economy and evaluate the impact of higher decarbonization speeds. We find that the faster transit... [more]

The field of electric vehicle charging load modelling has been growing rapidly in the last decade. In light of the Paris Agreement, it is crucial to keep encouraging better modelling techniques for successful electric vehicle adoption. Additionally, numerous papers highlight the lack of charging station data available in order to build models that are consistent with reality. In this context, the purpose of this article is threefold. First, to provide the reader with an overview of the open datasets available and ready to be used in order to foster reproducible research in the field. Second, to review electric vehicle charging load models with their strengths and weaknesses. Third, to provide suggestions on matching the models reviewed to six datasets found in this research that have not previously been explored in the literature. The open data search covered more than 860 repositories and yielded around 60 datasets that are relevant for modelling electric vehicle charging load. These... [more]

Superconductor technology has recently attracted increasing attention in power-generation- and electrical-propulsion-related domains, as it provides a solution to the limited power density seen by the core component, electrical machines. Superconducting machines, characterized by both high power density and high efficiency, can effectively reduce the size and mass compared to conventional machine designs. This opens the way to large-scale purely electrical applications, e.g., all-electrical aircrafts. The alternating current (AC) loss of superconductors caused by time-varying transport currents or magnetic fields (or both) has impaired the efficiency and reliability of superconducting machines, bringing severe challenges to the cryogenic systems, too. Although much research has been conducted in terms of the qualitative and quantitative analysis of AC loss and its reduction methods, AC loss remains a crucial problem for the design of highly efficient superconducting machines, especiall... [more]

Energy sustainability constitutes an important goal for development, as declared at the global and the European levels. Some conditions decisive for energy performance, as suggested by the Environmental Kuznets Curve (EKC) hypothesis, may be specified by the sectoral structure of production, as industries vary in the intensity of energy consumption. Nevertheless, sustainability is not automatically induced along with economic development and it is important to identify its determinants. The aim of the study is to empirically verify whether the sectoral structure of an economy differentiates energy sustainability within 28 European Union member states (the EU-28). To fulfil the task, a static approach was adopted and such taxonomic methods as the Ward agglomeration method and linear ordering based on the Hellwig synthetic measure were used. The hypothesis concerning the essential role of structural features in energy achievements was verified by a one-way analysis of variance. Our resul... [more]

Transmitter antenna arrays are typically coupled to several RF chains, which imposes stringent requirements on the linearization of each power amplifier (PA) present in the system. For this and other reasons discussed in this work, Over-the-air (OTA) linearization methods are considered to linearize transmitter antenna arrays in 5G scenarios. However, several factors need to be considered when applying OTA linearization methods. In this paper, an extended critical review of validated OTA linearization methods is presented. The main goal is to point out and discuss the most prominent methods, in order to determine which one is the most suitable for a specific application. In particular, analysis for each method is performed and, subsequently, their benefits and the disadvantages are systematically discussed. This is sought to fill-in a gap in the scientific literarure and, thus, to help radio-frequency engineers in the implementation of OTA digital pre-distortion (DPD) techniques for mu... [more]

The increasingly restrictive limits on exhaust emissions of automotive internal combustion engines imposed in recent years are pushing OEMs to seek new solutions to improve powertrain efficiency. Despite the increase in electric and hybrid powertrains, the turbocharging technique is still one of the most adopted solution in automotive internal combustion engines to achieve good efficiency with high specific power levels. Nowadays, turbocharged downsized engines are the most common solution to lower CO2 emissions. Pulse turbocharging is the most common boosting layout in automotive applications as the best response in terms of time-to-boost and exhaust energy extraction. In a high-fractionated engine with four or more cylinders, a twin entry turbine can be adopted to maximize pulse turbocharging benefits and avoid interaction in the discharge phase of the cylinders. The disadvantages of the twin entry turbine are mainly due to the complexity of the exhaust piping line and the high amoun... [more]

This article addresses current problems of risk analysis and probabilistic modelling for functional safety management in the life cycle of safety-related systems. Two main stages in the lifecycle of these systems are distinguished, namely the design and operation. The risk analysis and probabilistic modelling differ in these stages in view of available knowledge and data. Due to the complexity and uncertainty involved, both qualitative and quantitative information can be useful in risk analysis and probabilistic modelling. Some methodological aspects of the functional safety assessment are outlined that include modelling of dependent failures or cybersecurity and verifying the safety integrity level (SIL) under uncertainty. It is illustrated how the assumptions in the process of risk analysis and probabilistic modelling influence results obtained and, therefore, potentially the decisions taken in functional safety management. Programmable control and safety systems play an important ro... [more]

Turbulent jet ignition technology can significantly improve lean combustion stability and suppress engine knocking. However, the narrow jet channel between the pre-chamber and the main chamber leads to some difficulties in heat exchange, which significantly affects combustion performance and mechanical component lifetime. To clarify the effect of temperature conditions on combustion evolutions of turbulent jet ignition, direct numerical simulations with detailed chemical kinetics were employed under engine-relevant conditions. The flame propagation in the pre-chamber and the early-stage turbulent jet ignition in the main chamber were investigated. The results show that depending on temperature conditions, two types of flame configuration can be identified in the main chamber, i.e., the normal turbulent jet flame propagation and the spherical flame propagation, and the latter is closely associated with pressure wave disturbance. Under low-temperature conditions, the cold jet stoichiomet... [more]

Miniature gas turbines (MGT) are an important part of the production of electric energy in distributed systems. Due to the growing requirements for lower emissions and the increasing prices of hydrocarbon fuels, it is becoming more and more important to enhance the efficiency and improve the quality of the combustion process in gas turbines. One way to reduce NOx emissions is to add water to the fuel in the form of a water-based emulsion (FWE). This article presents the research results and the analysis of the impact of the use of FWE on CO and NOx emissions as well as on fuel consumption in MGT GTM-120. Experimental tests and numerical calculations were carried out using standard fuel (DF) and FWE with water content from 3% to 12%. It was found that the use of FWE leads to a reduction in NOx and CO emissions and reduction in the consumption of basic fuel. The maximum reduction in emissions by 12.32% and 35.16% for CO and NOx, respectively, and a reduction in fuel consumption by 5.46%... [more]

Anaerobic digestion with corn straw faces the problems of difficult degradation, long fermentation time and acid accumulation in the high concentration of feedstocks. In order to speed up the process of methane production, corn straw treated with sodium hydroxide was used in thermophilic (50 °C) anaerobic digestion, and the effects of biochar addition on the performance of methane production and the microbial community were analyzed. The results showed that the cumulative methane production of all treatment groups reached over 75% of the theoretical methane yield in 7 days and the addition of 4% biochar increased the cumulative methane production by 6.75% compared to the control group. The addition of biochar also decreased the number of biogas and methane production peaks from 2 to 1, and had a positive effect on shortening the digestion start-up period and reducing the fluctuation of biogas production during the digestion process. The addition of 4% biochar increased the abundance of... [more]

The characterization of materials, stress and fatigue state monitoring based on the acoustoelastic principle are gaining widespread attention in recent years, mainly due to their advantages such as high sensitivity and non-destructive character. This article presents the application of a non-destructive acoustic method to test the degree of degradation of materials with which the heating boiler is coated. The combustion chamber is covered in materials when the temperature of the process itself increases, and has a very positive effect on fuel combustion. Unfortunately, with the passage of time, such materials undergo gradation. This article describes an innovative measuring system that has been successfully applied to monitor changes in resonance frequency under uniaxial compression in refractory grade material, which by definition is characterized by a high level of heterogeneity with a network of pre-existing cracks. The paper indicates that both stress and elasticity coefficients ha... [more]

It has been proven that to solve the problems that arise in the combinatorial modeling of the prospects for the development of regional renewable energy, an algorithmically simple general combinatorial approach is the most appropriate option. The conceptual express method and corresponding mechanisms of the economic estimation of the efficiency of variants of the formation of regional systems of renewable energy have been suggested. These variants take into account the inflationary factors which serve as a basis of the analysis of investment and innovative projects of renewable energy sources by means of combinatorial modeling methods. To qualitatively analyze the effectiveness of the compared options, the system of existing indicators of the economic efficiency of renewable energy sources at the meso-level has been studied. The system was supplemented by informal and environmental indicators, the need for which is due to the fact that they have a significant impact on renewable energy... [more]

The structure and performance of promoted Ni/Al2O3 with Cu via thermocatalytic decomposition (TCD) of CH4 mixture (2% CH3OH) were studied. Mesoporous Cat-1 and Cat-2 were synthesized by the impregnation method. The corresponding peaks of nickel oxide and copper oxide in the XRD showed the presence of nickel and copper oxides as a mixed alloy in the calcined catalyst. Temperature program reduction (TPR) showed that Cu enhanced the reducibility of the catalyst as the peak of nickel oxide shifted toward a lower temperature due to the interaction strength of the metal particles and support. The impregnation of 10% Cu on Cat-1 drastically improved the catalytic performance and exhibited 68% CH4 conversion, and endured its activity for 6 h compared with Cat-1, which deactivated after 4 h. The investigation of the spent carbon showed that various forms of carbon were obtained as a by-product of TCD, including graphene fiber (GF), carbon nanofiber (CNF), and multi-wall carbon nanofibers (MWCNF... [more]

Mobilizing industry and transforming industrial sectors to a circular economy (CE) is one of the key areas of activities in the European Green Deal (EGD)—the newest strategy of economic growth in European Union (EU). In the CE, the raw materials that can be recovered from various waste streams play a key role, therefore, recommendations for their management were developed, both at the European and national level. In Poland, the raw material recovery sector is one of the strategic sectors (key industries) described in several documents determining the further directions of economic growth in the country. This paper presents the revision of these documents and guidelines for the implementation of the CE in the raw material recovery sector. The scope of the paper also includes a description of the current state of the raw materials recovery sector and its return, supported by the analysis of drivers and barriers in its further development. In previous years, a dynamic development of the r... [more]

The issue of energy behaviour among Polish consumers, and especially the motives and attitudes they manifest, is relatively under-researched. This article attempts to identify individual attitudes and beliefs of energy consumers using the example of the residents of the province of Silesia (Poland). The authors conducted the expert segmentation of respondents in terms of their motivation for saving energy, based on the results of their proprietary survey. The second stage of the study involved using a classification model that allowed for the characterisation of the obtained groups. Psychological and financial factors were of greatest significance, which is confirmed by the results of other studies. Nonetheless, the obtained results explicitly indicate the specificity of the region, which requires transformation towards a low-emission economy. Despite the initial stage of changes both in the awareness of the consumers and the public interventions of the authorities, it should be emphas... [more]

It is a fact that electric vehicles (EVs) are beneficial for climate protection. However, the current challenge is to decide on whether to reuse an EV battery or to recycle it after its first use. This paper theoretically investigates these areas i.e., recycle and reuse. It was found that there are several commercially used recycling processes and also some are under research to regain maximum possible materials and quantity. The concept of reusing (second life) of the battery is promising because, at the end of the first life, batteries from EVs can be used in several applications such as storing energy generated from renewable sources to support the government grid. However, the cost and life-cycle analysis (LCA) demonstrated that there are several aspects involved in battery reuse applications. Henceforth, one LCA generalised method cannot provide an optimal approach for all cases. It is important to have a detailed study on each of the battery reusing applications. Until then, it i... [more]