This study is aimed at a succinct review of practical impacts of grid integration of renewable energy systems on effectiveness of power networks, as well as often employed state-of-the-art solution strategies. The renewable energy resources focused on include solar energy, wind energy, biomass energy and geothermal energy, as well as renewable hydrogen/fuel cells, which, although not classified purely as renewable resources, are a famous energy carrier vital for future energy sustainability. Although several world energy outlooks have suggested that the renewable resources available worldwide are sufficient to satisfy global energy needs in multiples of thousands, the different challenges often associated with practical exploitation have made this assertion an illusion to date. Thus, more research efforts are required to synthesize the nature of these challenges as well as viable solution strategies, hence, the need for this review study. First, brief overviews are provided for each of... [more]

The estimation of lithium ion capacity fade and impedance rise on real application is always a challenging work due to the associated complexity. This work envisages the study of the battery charging profile indicators (CPI) to estimate battery health indicators (capacity and resistance, BHI), for high energy density lithium-ion batteries. Different incremental capacity (IC) parameters of the charging profile will be studied and compared to the battery capacity and resistance, in order to identify the data with the best correlation. In this sense, the constant voltage (CV) step duration, the magnitudes of the IC curve peaks, and the position of these peaks will be studied. Additionally, the behaviour of the IC curve will be modeled to determine if there is any correlation between the IC model parameters and the capacity and resistance. Results show that the developed IC parameter calculation and the correlation strategy are able to evaluate the SOH with less than 1% mean error for capa... [more]

No valid fluid theory exists for power extraction from unpressurized confined flow. The absence of a valid model to determine baseline uniform power extraction in confined flows creates difficulties in characterizing the coefficient of power. Currently, the primary body of research has been limited to Diffuser Augmented Wind Turbines (DAWTs) and passive fluid accelerators. Fluid power is proportional to the cube of velocity; therefore, passive acceleration is a promising path to effective renewable energy. Hypothetical models and experiments for passive accelerators yield low ideal power limits and poor performance, respectively. We show that these results derive from the misapplication of Betz’s Law and lack of a general theory for confined flow extraction. Experimental performance is due to the low efficiency of DAWTs and prior hypotheses exhibit high predictive error and continuity violations. A fluid model that accurately predicts available data and new experimental data, showing d... [more]

Improving the eco-efficiency of food systems is one of the major global challenges faced by the modern world. Short food supply chains (SFSCs) are commonly regarded to be less harmful to the environment, among various reasons, due to their organizational distribution and thus the shortened physical distance between primary producers and final consumers. In this paper, we empirically test this hypothesis, by assessing and comparing the environmental impacts of short and long food supply chains. Based on the Life Cycle Assessment (LCA) approach, we calculate eco-efficiency indicators for nine types of food distribution chains. The analysis is performed on a sample of 428 short and long food supply chains from six European countries. Our results indicate that, on average, long food supply chains may generate less negative environmental impacts than short chains (in terms of fossil fuel energy consumption, pollution, and GHG emissions) per kg of a given product. The values of eco-efficienc... [more]

This paper deals with the pyrolysis conversion of synthetic waste materials into noble fuels, i.e., heating oils, gasoline, diesel, and carbon. The following article presents the principle and use of pyrolysis conversion of waste tires and plastics. The core of the paper is the determination of energy properties of noble fuels obtained from pyrolysis conversion and the possibility of their real use in industry. The aim of this paper is a technical-economic evaluation of the use of waste pyrolysis in practice in the Slovak Republic. Unlike various methods of waste management, there are also more efficient methods, which primarily have a positive effect on the ecology of our Earth and at the same time can be effectively used for the production of alternative fuels. One of these methods is the pyrolysis conversion of synthetic waste materials into noble fuels. It is an ecological, waste-free, economical, and economical disposal of waste with a full recovery of its energy and material comp... [more]

UK Feed-in Tariffs created a vibrant business ecosystem for the deployment of decentralised renewable energy technologies while constituting a regressive tax and increasing inequality. Business model innovation spurred by their withdrawal is providing valuable lessons for progressive policy design. Using the case study of solar PV deployment on multi-occupancy social housing, this paper reveals policy, business and organisational challenges that need to be overcome to address fuel poverty and reduce inequality. Suitable ‘export’ and ‘local’ business models were identified through a workshop and subsequently evaluated through qualitative thematic interview analysis. The ‘local’ model compares favourably in terms of production costs and benefits for fuel poor tenants but unfavourably in terms of transaction costs. Both models are considered equally susceptible to changes in policy. Their success hinges upon third party intermediaries, peer-to-peer learning and a supportive policy environ... [more]

In the last decade, mainly due to political incentives towards energy efficiency, the share of lamps with power electronic interfaces, like Compact Fluorescent Lamps (CFL) and Light Emitting Diode (LED) lamps, has significantly increased in the residential sector. Their massive use might have a substantial impact on harmonic currents and, consequently, on the current flowing in the neutral conductor. This paper analyzes the impact of modern energy-efficient lighting technologies on the neutral conductor current by using a synthetic Low Voltage residential grid. Different load scenarios reflecting the transition from incandescent lamps, via CFL, to LED lamps are compared concerning the neutral conductor current at different points in the network. The inherent randomness related to the use of lighting devices by each residential customer is considered employing a Monte Carlo simulation. Obtained results show that the use of CFL has a greater impact on the neutral conductor current of Low... [more]

The building sector is an energy-consuming sector, and the development of zero-energy buildings (ZEBs) is necessary to address this. A ZEB’s active components include a system that utilizes renewable energy. There is a heat-pump system using geothermal energy. The system is available regardless of weather conditions and time, and it has attracted attention as a high-performance energy system due to its stability and efficiency. However, initial investment costs are higher than other renewable energy sources. To solve this problem, design optimization for the capacity of geothermal heat-pump systems should be performed. In this study, a capacity optimization design of a geothermal heat-pump system was carried out according to building load pattern, and emphasis was placed on cost aspects. Building load patterns were modeled into hospitals, schools, and apartments, and, as a result of optimization, the total cost over 20 years in all building load patterns was reduced.

Rain falling from the sky is viewed as a clean energy source with a great potential, owing to the large amount of it and its zero pollution nature, the fact that it has scattered raindrops, and its characteristic rainfall concentration that promotes extensive research on harvesting and utilization. Here, we introduce a new approach to harvest rainwater on rooftops called the Rain-Power Utilization System, which is composed of an initial rainwater disposal system and multistage energy conversion system. Initial rainwater is discharged into a split-flow pipe due to its poor quality and impurities. Additionally, clean rainwater is accumulated in a storage pipe until the water level reaches a specified height, triggering siphonage for energy conversion. The same process is repeated in other storage pipes connected in series. Function relations among physical and dimension parameters have been established for further studies. A kind of simplified optimization algorithm has been proposed con... [more]

The RSS has been widely used in directional drilling. In order to enhance wellpath control accuracy and efficiency of the static push-the-bit RSS, a powerful BUR prediction method is reconstructed by coupling a rotary steerable bottom-hole assembly (RSBHA) mechanical model and a drill bit−rock interaction model. This article showed that when establishing the RSBHA mechanical model by using the continuous beam column method, the steering rib should be treated as an eccentric stabilizer to consider the contact effect between the steering rib and wellbore wall. For the beam column containing the flexible sub and between two stabilizers, it should be rearranged into three beam columns, and the lower and upper steps of the flexible sub should be considered as virtual supports. The equilibrium tendency method (ETM) to predict the BUR can enhance wellpath prediction accuracy than those of traditional methods. Under 3D conditions, the total drilling tendency angle should be denoted by inclinat... [more]

This paper is devoted to investigating the effects of high-speed elongation of arcs inside ultra-fast switches (ucontact≈ 5−80 m/s), through a 2-D time-dependent model, in Cartesian coordinates. Two air arcs in series, one between a stationary anode and a moving cathode and the other between a stationary cathode and a moving anode in the arc chamber, are considered. A variable speed experimental setup through a Thomson drive actuator is designed to support this study. A computational fluid dynamics (CFD) equations system is solved for fluid velocity, pressure, temperature, and electric potential, as well as the magnetic vector potential. Electron emission mechanisms on the contact surface and induced current density due to magnetic field changes are also considered to describe the arc root formation, arc bending, lengthening, and calculating the arc current density, as well as the contact temperatures, in a better way. Data processing techniques are utilized to derive instantaneous cor... [more]

Recently, extensive studies have focused on exploring a variety of silicon (Si) nanostructures among which Si quantum dots (Si QDs) may be applied in all Si tandem solar cells (TSCs) for the time to come. By virtue of its size tunability, the optical bandgap of Si QDs is capable of matching solar spectra in a broad range and thus improving spectral response. In the present work, size-controllable Si QDs are successfully obtained through the formation of Si QDs/SiC multilayers (MLs). According to the optical absorption measurement, the bandgap of Si QDs/SiC MLs shows a red shift to the region of long wavelength when the size of dots increases, well conforming to quantum confinement effect (QCE). Additionally, heterojunction solar cells (HSCs) based on Si QDs/SiC MLs of various sizes are presented and studied, which demonstrates the strong dependence of photovoltaic performance on the size of Si QDs. The measurement of external quantum efficiency (EQE) reveals the contribution of Si QDs... [more]

In micro-grid systems, wind turbines are essential power generation sources. The direct-driven surface-mounted permanent-magnet synchronous generators (SMPMSGs) in variable-speed wind generation systems (VS-WGSs) are promising due to their high efficiency/power density and the avoidance of using a gearbox, i.e., regular maintenance and noise are averted. Usually, the main goal of the control system for SMPMSGs is to extract the maximum available power from the wind turbine. To do so, the rotor position/speed of the SMPMSG must be known. Those signals are obtained by the help of an incremental encoder or speed transducer. However, the system reliability is remarkably reduced due to the high failure rate of these mechanical sensors. To avoid this problem, this paper presents a model reference adaptive system with finite-set (MRAS-FS) observer for encoderless control of SMPMSGs in VS-WGSs. The motif of the presented MRAS-FS observer is taken from the direct-model predictive control (DMPC)... [more]

The paper contains a simplified energy and exergy analysis of pumps and pipelines system integrated with Thermal Energy Storage (TES). The analysis was performed for a combined heat and power plant (CHP) supplying heat to the District Heating System (DHS). The energy and exergy efficiency for the Block Part of the Siekierki CHP Plant in Warsaw was estimated. CHP Plant Siekierki is the largest CHP plant in Poland and the second largest in Europe. The energy and exergy analysis was executed for the three different values of ambient temperature. It is according to operation of the plant in different seasons: winter season (the lowest ambient temperature Tex = −20 °C, i.e., design point conditions), the intermediate season (average ambient temperature Tex = 1 °C), and summer (average ambient temperature Tex = 15 °C). The presented results of the analysis make it possible to identify the places of the greatest exergy destruction in the pumps and pipelines system with TES, and thus give the... [more]

The interest in turbojet engines was emerging in the past years due to their simplicity. The purpose of this article is to investigate sliding mode control (SMC) for a micro turbojet engine based on an unconventional compound thermodynamic parameter called Turbofan Power Ratio (TPR) and prove its advantage over traditional linear methods and thrust parameters. Based on previous research by the authors, TPR can be applied to single stream turbojet engines as it varies proportionally to thrust, thus it is suitable as control law. The turbojet is modeled by a linear, parameter-varying structure, and variable structure sliding mode control has been selected to control the system, as it offers excellent disturbance rejection and provides robustness against discrepancies between mathematical model and real plant as well. Both model and control system have been created in MATLAB® Simulink®, data from real measurement have been taken to evaluate control system performance. The same assessment... [more]

In the construction industry, it is the material production phase and the use phase of buildings’ life cycles that represent the greatest environmental burden. The presented research focused on wood constructions during their use phase. The primary objective of the research was to determine the amount of CO2 produced during the operation of specific wood constructions in connection with the energy demand for their heating. A correlation analysis of selected parameters revealed a statistically significant correlation between heating medium type and energy demand for heating (p = −0.5773) and between heating medium type and amount of CO2 produced (p = 0.4796). A more detailed analysis showed that, in terms of the average energy demand for heating, the column constructions were the most efficient among the compared construction systems, regardless of the energy standard. Similar findings were obtained for annual CO2 production in connection with the average energy demand for heating. The... [more]

An application of latent heat thermal energy storage systems with phase change materials seems to be unavoidable in the present world. The latent heat thermal energy storage systems allow for storing excessive heat during low demand and then releasing it during peak demand. However, a phase change material is only one of the components of a latent heat thermal energy storage system. The second part of the latent heat thermal energy storage is a heat exchanger that allows heat transfer between a heat transfer fluid and a phase change material. Thus, the main aim of this review paper is to present and systematize knowledge about the heat exchangers used in the latent heat thermal energy storage systems. Furthermore, the operating parameters influencing the phase change time of phase change materials in the heat exchangers, and the possibilities of accelerating the phase change are discussed. Based on the literature reviewed, it is found that the phase change time of phase change material... [more]

Concern for climate change is one of the drivers of new, transitional energy policies oriented towards economic growth and energy security, along with reduced greenhouse gas (GHG) emissions and preservation of biodiversity. Since 2010, the Climate Policy Initiative (CPI) has been publishing annual Global Landscape of Climate Finance reports. According to these reports, US$3660 billion has been spent on global climate change projects over the period 2011−2018. Fifty-five percent of this expenditure has gone to wind and solar energy. According to world energy reports, the contribution of wind and solar to world energy consumption has increased from 0.5% to 3% over this period. Meanwhile, coal, oil, and gas continue to supply 85% of the world’s energy consumption, with hydroelectricity and nuclear providing most of the remainder. With this in mind, we consider the potential engineering challenges and environmental and socioeconomic impacts of the main energy sources (old and new). We find... [more]

This paper evaluates the link between economic growth, renewable energy, tourism arrivals, trade openness, and carbon dioxide emissions in the European Union (EU-28). As an econometric strategy, the research uses panel data. In the first step, we apply the unit root test, and the results demonstrated that the variables used in this study are integrated I (1) in the first difference. In the second step, we apply the Pedroni cointegration test, and Kao Residual cointegration test, and we observe that the variables are cointegrated in the long run. The panel fully modified least squares (FMOLS), panel dynamic least squares (DOLS), and generalized moments system (GMM-System) estimator are considered in this research. The econometric results proved that trade openness and renewable energy decreased climate change and environmental degradation. The empirical study also found a positive effect of economic growth on carbon dioxide emissions. Moreover, tourism arrivals are negatively correlated... [more]

Recent developments, such as smart metering, distributed energy resources, microgrids, and energy storage, have led to an exponential increase in system complexity and have emphasized the need to include customer behavior and social and cultural backgrounds in planning activities. This paper analyzes how emergent behavior in electricity consumption can affect the planning of distribution grids with a smart grid vision. For this, an agent-based model that uses insights from the field of behavioral economics to differentiate four consumer categories (high income, low income, middle class, and early adopters) was used. The model was coupled with a real distribution feeder and customer load curve data, and the results showed that heterogeneity of customer’s preferences, values, and behavior led to very distinct load growth patterns. The results emphasize the relevance of modeling customer’s behavioral aspects in planning increasingly complex power systems.

Today, biofuels are indispensable in the implementation of fossil fuels replacement processes. This study evaluates ethyl acetate (EA) as a solvent of two straight vegetable oils (SVOs), castor oil (CO), and sunflower oil (SO), in order to obtain EA/SVO double blends that can be used directly as biofuels, or along with fossil diesel (D), in the current compression-ignition (C.I.) engines. The interest of EA as oxygenated additive lies not only in its low price and renewable character, but also in its very attractive properties such as low kinematic viscosity, reasonable energy density, high oxygen content, and rich cold flow properties. Revelant fuel properties of EA/SVO double and D/EA/SVO triple blends have been object of study including kinematic viscosity, pour point (PP), cloud point (CP), calorific value (CV), and cetane number (CN). The suitability of using these blends as fuels has been tested by running them on a diesel engine electric generator, analyzing their effect on engi... [more]

In order to study the axial compression performance of the T-shaped multi-cavity concrete-filled steel tube shear wall, first, three specimens were designed to perform the axial compression test. Then three-dimensional finite element analysis by the ABAQUS software was used to obtain the axial bearing capacity of the shear wall with different parameters. According to the results of the finite element model, the computational diagram in the limit state was obtained. The diagram was simplified into the core concrete in the non-enhanced area that was not constrained by the steel tube and the core concrete in the enhanced area that was uniformly constrained by the steel tube. Finally, a new practical equation for calculating the axial bearing capacity of a multi-cavity concrete-filled steel tubular shear wall was deduced and proposed based on the theory of ultimate equilibrium. The calculation results of the proposed equation were in good agreement with the finite element results, and the... [more]

New technological solutions are required to control the impact of the increasing presence of renewable energy sources connected to the electric grid that are characterized by unpredictable production (i.e., wind and solar energy). Energy storage is becoming essential to stabilize the grid when a mismatch between production and demand occurs. Among the available solutions, Power to Hydrogen (P2H) is one of the most attractive options. However, despite the potential, many barriers currently hinder P2H market development. The literature reports general barriers and strategies to overcome them, but a specific analysis is fundamental to identifying how these barriers concretely arise in national and regional frameworks, since tailored solutions are needed to foster the development of P2H local market. The paper aims to identify and to analyze the existing barriers for P2H market uptake in Italy. The paper shows how several technical, regulatory and economic issues are still unsolved, result... [more]

Large-scale grid integration of renewable energy increases the uncertainty and volatility of power systems, which brings difficulties to output planning and reserve decision-making of power system units. In this paper, we innovatively combined the non-parametric kernel density estimation method and scenario method to describe the uncertainty of renewable energy outputs, and obtained a representative set of renewable energy output scenarios. In addition, we proposed a new method to determine the reserve capacity demand. Further, we derived the quantitative relationship between the reserve demand and the power system reliability index, which was used as the constraint condition of a day-ahead power generation dispatch. Finally, a coordinated dispatching model of power generation and reserve was established, which had the lowest penalty for curtailment of wind power and photovoltaic, as well as the lowest total operating cost for thermal power units, gas power units, and pumped storage po... [more]

Our knowledge of discount rates plays an important role both in the discounted cash flow decision-making process and in the later phases of a project’s lifetime. It is useful than both for management and cash-flow monitoring purposes at operating stages. Investors putting money into power generation projects expect an appropriate rate of return to compensate them for a minimum acceptable real return available in the market (risk-free rate of interest) and the project’s specific risk. Due to its essential nature in the financial and economic evaluation of projects (it is the only parameter that reflects the risk), it is reasonable to assume that investors would also be interested in constituent components of that indicator. The discount rate is one parameter in the discounted cash flow analysis that takes into account the risk of a venture. Further, the previous research in this area has focused mainly on the dimension of this variable, and the structure of this parameter has not been d... [more]