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Energies, Volume 14, Issue 16

2021 August-2 - 501 articles

Cover Story: Commercial two-stage servovalves and direct-drive servovalves are extensively used in industry and aeronautical applications, given the excellent dynamic response of the former and the simplicity of construction of the latter. Despite this, these valves have some drawbacks that are still unresolved, such as the high complexity and internal leakage of pilot stages of two-stage servovalves as well as the large weight of the linear force motors of direct-drive servovalves. The use of piezoelectric actuators can be instrumental in solving these issues, in addition to further improving the dynamic response of these valves. This paper is a comprehensive review of novel servovalve architectures that exploit piezoelectric actuation, showing the potential of some to be used by manufacturers as future high-performance designs. View this paper
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Articles (501)

  • Article
  • Open Access
13 Citations
3,587 Views
12 Pages

Power Enhancement of a PV Module Using Different Types of Phase Change Materials

  • Ali Shaito,
  • Mohammad Hammoud,
  • Fadel Kawtharani,
  • Ali Kawtharani and
  • Hilal Reda

23 August 2021

Photovoltaic (PV) systems are well-known systems that convert solar energy into electrical energy. Increases in operating temperature induce a drop in conversion efficiency and, thus, in the output power produced by the panel. This paper investigates...

  • Article
  • Open Access
192 Citations
12,635 Views
21 Pages

23 August 2021

In the last few years, several countries have accomplished their determined renewable energy targets to achieve their future energy requirements with the foremost aim to encourage sustainable growth with reduced emissions, mainly through the implemen...

  • Article
  • Open Access
15 Citations
3,728 Views
18 Pages

Energy Efficiency and Decarbonization in the Context of Macroeconomic Stabilization

  • Anna Misztal,
  • Magdalena Kowalska,
  • Anita Fajczak-Kowalska and
  • Otakar Strunecky

23 August 2021

Decarbonization is an activity aimed at reducing greenhouse gas emissions to limit climate change and global warming. Ensuring macroeconomic stabilization is the basis for ecological action. The question is whether macroeconomic stabilization helps c...

  • Article
  • Open Access
18 Citations
5,782 Views
26 Pages

23 August 2021

This work presents a comparison study of the CFD modeling with two different turbulence modeling approaches viz. unsteady RANS and LES, on a full-scale model of the (New) MEXICO rotor wind turbine. The main emphasis of the paper is on the rotor and w...

  • Article
  • Open Access
10 Citations
2,751 Views
23 Pages

23 August 2021

Vertical axis turbines, which extract kinetic energy from currents, can produce electricity independently from a current’s direction. Hence, this type of turbines raises interest for harvesting energy from tidal currents, where flow changes direction...

  • Article
  • Open Access
14 Citations
2,515 Views
16 Pages

23 August 2021

The article deals with the problem of the effects of using a wooden church on thermal and humidity conditions forming inside. Religious services in the studied site were provided several times a year. The building was not used in the remaining time....

  • Article
  • Open Access
1 Citations
3,732 Views
17 Pages

Hydrodynamic Modeling of Oil–Water Stratified Smooth Two-Phase Turbulent Flow in Horizontal Circular Pipes

  • Qi Kang,
  • Jiapeng Gu,
  • Xueyu Qi,
  • Ting Wu,
  • Shengjie Wang,
  • Sihang Chen,
  • Wei Wang and
  • Jing Gong

23 August 2021

In the petrochemical industry, multiphase flow, including oil–water two-phase stratified laminar flow, is more common and can be easily obtained through mathematical analysis. However, there is limited mathematical analytical model for the simulation...

  • Review
  • Open Access
33 Citations
5,105 Views
25 Pages

Towards Optimal Management in Microgrids: An Overview

  • Álex Omar Topa Gavilema,
  • José Domingo Álvarez,
  • José Luis Torres Moreno and
  • Manuel Pérez García

23 August 2021

A microgrid is a set of decentralized loads and electricity sources, mainly renewable. It can operate connected to and synchronized with a traditional wide-area synchronous grid, i.e., a macrogrid, but can also be disconnected to operate in “island m...

  • Article
  • Open Access
19 Citations
3,111 Views
18 Pages

23 August 2021

The fuel qualities of several biodiesels containing highly saturated, mono, and poly unsaturated fatty acids, as well as their combustion and exhaust emission characteristics, were studied. Six biodiesel samples were divided into two groups based on...

  • Article
  • Open Access
6 Citations
2,790 Views
21 Pages

Bumpless Transfer of Uncertain Switched System and Its Application to Turbofan Engines

  • Penghui Sun,
  • Xi Wang,
  • Shubo Yang,
  • Bei Yang,
  • Huairong Chen and
  • Bin Wang

23 August 2021

Nonlinear control problems in turbofan engines are challenging. No single nonlinear controller can achieve desired control effects in a full flight envelope, but in the case of multiple controllers, there exist problems in the bumpless transfer betwe...

  • Article
  • Open Access
29 Citations
4,289 Views
26 Pages

Solar-Based DG Allocation Using Harris Hawks Optimization While Considering Practical Aspects

  • Suprava Chakraborty,
  • Sumit Verma,
  • Aprajita Salgotra,
  • Rajvikram Madurai Elavarasan,
  • Devaraj Elangovan and
  • Lucian Mihet-Popa

23 August 2021

The restructuring of power systems and the ever-increasing demand for electricity have given rise to congestion in power networks. The use of distributed generators (DGs) may play a significant role in tackling such issues. DGs may be integrated with...

  • Article
  • Open Access
9 Citations
2,294 Views
13 Pages

Innovative Techniques in Underground Mining for the Prevention of Gas Dynamic Phenomena

  • Martina-Inmaculada Álvarez-Fernández,
  • María-Belén Prendes-Gero,
  • Juan-Carlos Peñas-Espinosa and
  • Celestino González-Nicieza

23 August 2021

In the last decades, rigorous research has been carried out with the end of understanding the gas dynamic phenomenon and although different preventive techniques have been employed, even today there are numerous accidents even with the loss of life....

  • Review
  • Open Access
40 Citations
8,579 Views
26 Pages

Review of Wind Turbine Icing Modelling Approaches

  • Fahed Martini,
  • Leidy Tatiana Contreras Montoya and
  • Adrian Ilinca

23 August 2021

When operating in cold climates, wind turbines are vulnerable to ice accretion. The main impact of icing on wind turbines is the power losses due to geometric deformation of the iced airfoils of the blades. Significant energy losses during the wind f...

  • Article
  • Open Access
27 Citations
4,519 Views
26 Pages

23 August 2021

Urban heat island (UHI) effects significantly impact building energy. Traditional UHI investigation methods are often incapable of providing the high spatial density of observations required to distinguish small-scale temperature differences in the U...

  • Article
  • Open Access
28 Citations
3,216 Views
10 Pages

Risk Management Scenarios for Investment Program Delays in the Polish Power Industry

  • Stanisław Tokarski,
  • Małgorzata Magdziarczyk and
  • Adam Smoliński

23 August 2021

The introduction of the Green Deal in 2019 by the European Commission poses a significant challenge for EU member states whose power generation is based primarily on fossil fuels. In Poland, nearly 80% of the electricity is produced from fossil fuels...

  • Article
  • Open Access
10 Citations
3,401 Views
19 Pages

Experimental Assessment of the Performance and Emissions of a Spark-Ignition Engine Using Waste-Derived Biofuels as Additives

  • Joaquim Costa,
  • Jorge Martins,
  • Tiago Arantes,
  • Margarida Gonçalves,
  • Luis Durão and
  • Francisco P. Brito

23 August 2021

The use of biofuels for spark ignition engines is proposed to diversify fuel sources and reduce fossil fuel consumption, optimize engine performance, and reduce pollutant emissions. Additionally, when these biofuels are produced from low-grade wastes...

  • Article
  • Open Access
3 Citations
2,246 Views
13 Pages

23 August 2021

The flexible excitation system (FES) is a kind of novel excitation system with two channels for damping control. Besides the basic functions of traditional excitation systems, flexible excitation systems can provide reactive power support for the ter...

  • Article
  • Open Access
33 Citations
7,406 Views
14 Pages

23 August 2021

Railway transit forms the backbone of sustainable transportation systems, which are necessary to limit the effects of global warming. In this paper, the authors seek to determine whether there is a statistically significant difference in energy consu...

  • Article
  • Open Access
12 Citations
3,466 Views
14 Pages

23 August 2021

The management of the power transformer population is a complex process, as the grid companies operate thousands of devices. For this issue, the health index method can be applied to facilitate asset management. The algorithm can be used not only in...

  • Article
  • Open Access
11 Citations
2,449 Views
14 Pages

23 August 2021

The quantitative evaluation of cluster wind power output volatility and source-load timing matching is vital to the planning and operation of the future power system dominated by new energy. However, the existing volatility evaluation methods of clus...

  • Article
  • Open Access
5 Citations
3,521 Views
32 Pages

23 August 2021

A control technique combining pulse width modulation (PWM) and pulse amplitude modulation (PAM) is presented herein to reduce the output voltage ripple of the converter as little as possible. Such a converter requires a two-stage cascaded structure....

  • Article
  • Open Access
1 Citations
2,934 Views
21 Pages

23 August 2021

The fracturing technique is widely used in many fields. Fracture has a greater impact on the movement of fluids in formations. Knowing information about a fracture is key to judging its effect, but detailed information about complex fracture networks...

  • Article
  • Open Access
32 Citations
2,762 Views
20 Pages

22 August 2021

The energy transition is accompanied by developing a digital decentralized low-carbon energy infrastructure with renewable-based generating plants as its main elements. In 2020, 15 photovoltaic power plants (PVPs) with an installed capacity of 364 MW...

  • Article
  • Open Access
2 Citations
2,086 Views
26 Pages

22 August 2021

The filtered mass density function (FMDF) model has been employed for large-eddy simulations (LES) of compressible high-speed turbulent mixing and reacting flows. However, the mixing model remains a pressing challenge for FMDF methods, especially for...

  • Article
  • Open Access
10 Citations
3,202 Views
24 Pages

22 August 2021

In this paper, the authors discuss the problem of the influence of the level of electrification in African countries on their sustainable development. The first aim of the article is to determine the relationship between changes in the electrificatio...

  • Article
  • Open Access
3 Citations
2,751 Views
12 Pages

22 August 2021

In the present study, we provide useful data related to one of the most promising materials in thin-film solar cell technologies: Cu2ZnSnS4 (CZTS) kesterite structures. Sol-gel spin coating and chemical bath deposition methods were used to fabricate...

  • Article
  • Open Access
7 Citations
2,816 Views
23 Pages

Influence of Continuous Provision of Synthetic Inertia on the Mechanical Loads of a Wind Turbine

  • Arne Gloe,
  • Clemens Jauch,
  • Bogdan Craciun,
  • Arvid Zanter and
  • Jörg Winkelmann

22 August 2021

In many electrical grids, the share of renewable energy generation increases. As these generators are typically connected to the grid via inverters, the level of grid inertia decreases. Such grids may therefore suffer from high rates of change of fre...

  • Article
  • Open Access
13 Citations
2,796 Views
27 Pages

22 August 2021

The large-scale interconnection of the power grid has brought great benefits to social development, but simultaneously, the frequency of large-scale fault accidents caused by extreme weather is also rocketing. The power grid is regarded as a represen...

  • Article
  • Open Access
9 Citations
3,558 Views
23 Pages

22 August 2021

Magnetic beamforming techniques can enhance the power transfer efficiency using focused magnetic fields by the multiple transmitters to the receivers. However, the intra-couplings that cause power leakage and phase distortion among the arrayed coils...

  • Article
  • Open Access
3 Citations
2,518 Views
21 Pages

22 August 2021

A DC converter with the benefits of reverse power capability, less switching loss and wide voltage operation is presented and implemented for wide input voltage applications such as fuel cell energy, photovoltaic (PV) system and DC wind power. Two fu...

  • Article
  • Open Access
12 Citations
2,783 Views
15 Pages

Effect of Cleaning the Annular Space on the Adhesion of the Cement Sheath to the Rock

  • Marcin Kremieniewski,
  • Sławomir Błaż,
  • Stanisław Stryczek,
  • Rafał Wiśniowski and
  • Andrzej Gonet

22 August 2021

Drilling boreholes in gas zones and in zones with the possibility of migration or gas exhalation requires a high index of well tightness. An important parameter determining the effectiveness of sealing the annular space is the adhesion of the cement...

  • Article
  • Open Access
6 Citations
3,293 Views
14 Pages

Estimation of Heat Loss Coefficient and Thermal Demands of In-Use Building by Capturing Thermal Inertia Using LSTM Neural Networks

  • Martín Pensado-Mariño,
  • Lara Febrero-Garrido,
  • Estibaliz Pérez-Iribarren,
  • Pablo Eguía Oller and
  • Enrique Granada-Álvarez

22 August 2021

Accurate forecasting of a building thermal performance can help to optimize its energy consumption. In addition, obtaining the Heat Loss Coefficient (HLC) allows characterizing the thermal envelope of the building under conditions of use. The aim of...

  • Article
  • Open Access
9 Citations
3,511 Views
16 Pages

22 August 2021

The electronic oxygen regulator (EOR) is a new type of aviation oxygen equipment which uses electronic servo control technology to control breathing gas pressure. In this paper, the control method of EOR was studied, and the dynamic model of the avia...

  • Article
  • Open Access
11 Citations
3,660 Views
26 Pages

22 August 2021

Six supplementary cementitious materials (SCMs) were identified to be incorporated in concrete exposed to high-temperature cycling conditions within the thermal energy storage literature. The selected SCMs are bauxite, chamotte, ground granulated bla...

  • Article
  • Open Access
41 Citations
9,161 Views
22 Pages

22 August 2021

Smart cities are an extremely important, multi-faceted subject, both in terms of their practical aspects and in terms of research. This is expressed, among other things, in the multitude of approaches to this concept. These approaches differ based on...

  • Article
  • Open Access
3 Citations
2,425 Views
15 Pages

22 August 2021

This study evaluates temperatures measured at district heating (DH) valves in manholes and their usability for non-destructively assessing the thermal performance of buried DH pipes. The study was conducted as a field test in which part of a DH netwo...

  • Article
  • Open Access
14 Citations
3,904 Views
11 Pages

Small-Scaled Production of Blue Hydrogen with Reduced Carbon Footprint

  • Yuriy Zagashvili,
  • Aleksey Kuzmin,
  • George Buslaev and
  • Valentin Morenov

22 August 2021

This article reviews a method of hydrogen production based on partial non-catalytic oxidation of natural gas in an original synthesis gas generator. The working principles of the unit are similar to those of liquid-propellant rocket engines. This pap...

  • Article
  • Open Access
28 Citations
3,942 Views
19 Pages

Instability Control of Roadway Surrounding Rock in Close-Distance Coal Seam Groups under Repeated Mining

  • Yu Xiong,
  • Dezhong Kong,
  • Zhanbo Cheng,
  • Zhijie Wen,
  • Zhenqian Ma,
  • Guiyi Wu and
  • Yong Liu

22 August 2021

In order to solve the problems of roadway stability and easy instability under repeated mining of close-distance coal seam groups, the mechanism and control technology of surrounding rock instability under repeated mining were studied via indoor test...

  • Article
  • Open Access
14 Citations
8,005 Views
25 Pages

21 August 2021

The participation of central banks in the fight against climate change has recently been advanced in several academic articles and policy papers. Since the emerging consensus is that climate change poses financial risks, the envisaged green central b...

  • Article
  • Open Access
13 Citations
2,508 Views
15 Pages

21 August 2021

One of the methods of converting thermal energy into electricity is the use of thermoelectric generators (TEG). The method can be used in low-temperature waste heat conversion systems from industrial installations, but its serious limitation is the l...

  • Article
  • Open Access
8 Citations
3,951 Views
22 Pages

21 August 2021

The huge influence of the sampling rate on the performance of the digital PID control of a voltage source inverter (VSI) is revealed. It is shown that an appropriately chosen continuous-time model of a digital controller with the PWM power converter...

  • Article
  • Open Access
2 Citations
3,501 Views
26 Pages

21 August 2021

In this study, we numerically investigated the effects of design parameters, such as the strut geometry or diffusion angle, on the performance of an industrial turbine exhaust diffuser. Turbine exhaust diffusers are commonly used to change the kineti...

  • Article
  • Open Access
29 Citations
5,568 Views
23 Pages

Water, Energy, Food, Waste Nexus: Between Synergy and Trade-Offs in Romania Based on Entrepreneurship and Economic Performance

  • Radu Petrariu,
  • Marius Constantin,
  • Mihai Dinu,
  • Simona Roxana Pătărlăgeanu and
  • Mădălina Elena Deaconu

21 August 2021

Boosting the externalities across the water, energy, food, and waste (WEFW) sectors is challenging, especially considering tightening constraints such as population growth, climate change, resource-intensive lifestyles, increased waste production, sa...

  • Article
  • Open Access
4 Citations
2,842 Views
11 Pages

21 August 2021

The prevention and evaluation of explosions requires suitable standards of measurement. As such, for this study two ignition thresholds, the ignition temperature and the minimum ignition irradiance were selected as the assessment criteria. These igni...

  • Article
  • Open Access
15 Citations
3,718 Views
15 Pages

Use of CO2 to Cure Steel Slag and Gypsum-Based Material

  • Xue Wang,
  • Wen Ni,
  • Jiajie Li,
  • Siqi Zhang,
  • Keqing Li and
  • Wentao Hu

21 August 2021

To improve the utilization of steel slag (SS) in CO2 capture and making building materials, the paper mainly discussed the effects of desulphurization gypsum (DG) and w/s ratio on strength development and CO2 capture capability of high Al content SS....

  • Article
  • Open Access
15 Citations
14,884 Views
22 Pages

Analysis of Changes in Natural Gas Physical Flows for Europe via Ukraine in 2020

  • Filip Božić,
  • Daria Karasalihović Sedlar,
  • Ivan Smajla and
  • Ivana Ivančić

21 August 2021

The main objective of the paper was comparative analyses of natural gas quantities delivered through the existing pipeline capacities in the last decade and new pipeline capacities for the prediction of possible future flows of gas import to Europe....

  • Article
  • Open Access
20 Citations
3,989 Views
16 Pages

Hydrogen Production through Autothermal Reforming of Ethanol: Enhancement of Ni Catalyst Performance via Promotion

  • Ekaterina Matus,
  • Olga Sukhova,
  • Ilyas Ismagilov,
  • Mikhail Kerzhentsev,
  • Olga Stonkus and
  • Zinfer Ismagilov

21 August 2021

Autothermal reforming of bioethanol (ATR of C2H5OH) over promoted Ni/Ce0.8La0.2O1.9 catalysts was studied to develop carbon-neutral technologies for hydrogen production. The regulation of the functional properties of the catalysts was attained by adj...

  • Article
  • Open Access
3 Citations
2,950 Views
19 Pages

21 August 2021

A vibration control concept based on vibration energy conversion and storage with respect to a serial-stiffness-switch system (4S) has previously been proposed. Here, we first present a rotational electromagnetic serial-stiffness-switch system as a n...

  • Article
  • Open Access
4 Citations
2,520 Views
11 Pages

21 August 2021

High energetic efficiency is a major requirement in industrial processes. The poor thermal conductivity of conventional working fluids stands as a limitation for high thermal efficiency in thermal applications. Nanofluids tackle this limitation by th...

  • Article
  • Open Access
14 Citations
3,583 Views
15 Pages

20 August 2021

The objectives of this work are: (a) to present a new system for building heating which is based on underground energy storage, (b) to develop a mathematical model of the system, and (c) to optimise the energy performance of the system. The system in...

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Energies - ISSN 1996-1073