Jet fish pumps are efficient hydraulic machinery for fish transportation. Yet, the complex flow phenomenon in it is the major potential risk for damage to fish. The dangerous flow phenomena for fish, such as radial pressure gradient and exposure strain rate, are usually controlled by the structural parameters of jet fish pumps. Therefore, the injury rate of fish can be theoretically decreased by the structural optimization design of jet fish pumps. However, there is a complex nonlinear relation between flow phenomena and key structural parameters. To solve this problem, the present paper established a complex mapping between flow phenomena and structural parameters, based on computational fluid dynamics and a back-propagation neural network. According to this mapping, an NSGA-II multi-objective genetic algorithm was used to optimize the structure of jet fish pumps. The results showed that the optimized jet fish pumps could reduce the internal radial pressure gradient, exposure strain r... [more]

The growing population of cities means that they face many new challenges in improving their economic, social and environmental efficiency. These themes are relevant to the increasingly popular worldwide concept of smart cities. A smart city is a city that is friendly to people and the environment, in which people live better, safer, and healthier. From the point of view of management sciences, they are a result of creative development and the implementation of various solutions that should involve various stakeholders. The quality of life of city residents is largely influenced by logistics solutions, including the movement of both people and cargo in the city. This issue is directly relevant to the aim of this article, which is to try to determine the degree of cooperation between the city and city logistics stakeholders in the context of identifying gaps in the inclusion of logistics areas in the strategies of Polish cities. Both the role of stakeholders in actively shaping city str... [more]

This study evaluates the energy efficiency of pressure shock damping in a hydraulic lifting and leveling (HLL) module of a mobile robotic bricklaying system (RBS). The HLL module includes a servohydraulic actuator (SHA) and a hydraulic shock damper (HSD). The proposed adjustable HSD consists of a hydraulic accumulator circuit (HAC) and proportional damping valve. The frequency characteristics of the impedance and damping efficiency indices were used to evaluate the effectiveness of HSD damping. The dynamic responses of the SHA with and without HSD were analyzed based on a nonlinear state-space model. To control the damping of the pressure shock in the SHA-HSD system, a linear quadratic Gaussian (LQG) controller that follows two measurement signals was implemented. The LQG controller was adapted to the specific dynamic requirements of the SHA-HSD control system and nature of the RBS shock loads. The effectiveness of the LQG controller was evaluated during RBS operation under laboratory... [more]

The use of air conditioning in buildings to provide a comfortable environment accounts for up to 75% of the electricity consumed in Kuwait for the hot season from April through to the end of October. The widespread adoption of air conditioning systems in buildings has resulted in an increased demand for electricity. This has led to an increased peak load demand that has resulted in a larger carbon footprint and placed the electricity grid under significant strain. Heat-driven air conditioning systems that use solar energy are now emerging as alternatives to electricity-driven conventional refrigerated air conditioners. These systems are more energy-efficient, with lower carbon emissions while also ensuring better indoor air quality and comfort when optimally designed. Among the heat-driven air conditioning systems, the desiccant cooling system is among the systems with the most potential. This paper presents a numerical investigation of the design optimization of solar desiccant coolin... [more]

The growing demand for renewable energies and the application of sustainable and economically viable biorefinery processes have increased the study and application of lignocellulosic biomass. However, due to lignocellulosic biomass recalcitrance hindering its efficient utilization, the pretreatment in the biorefinery is an essential stage for success in the process. Therefore, Deep Eutectic Solvent (DES) has emerged as a promising green pretreatment. During this study, the effect of choline chloride [ChCl]:glycerol and [ChCl]:urea on sugarcane bagasse and brewery bagasse is evaluated. Results have demonstrated that using [ChCl]:glycerol in SCB reduced about 80% and 15% for acid-soluble lignin and Klason lignin, respectively, and improved efficiency on saccharification yields, achieving conversions of 60, 80, and 100% for glucan, xylan, and arabinan, correspondingly. In the case of BSG saccharification yields, about 65% and 98% are attained for glucan and xylan, respectively, when [ChCl... [more]

The standalone microgrids with renewable energy resources (RERs) such as a photovoltaic (PV) system and fast changing loads face major challenges in terms of reliability and power management due to a lack of inherent inertial support from RERs and their intermittent nature. Thus, energy storage technologies such as battery energy storage (BES) are typically used to mitigate the power fluctuations and maintain a power balance in the system. This paper presents a model predictive control (MPC) based power management strategy (PMS) for such standalone PV/battery systems. The proposed method is equipped with an autoregressive integrated moving average (ARIMA) prediction method to forecast the load and environmental parameters. The proposed controller has the capabilities of (1) effective power management, (2) minimization of transients during disturbances, and (3) automatic switching of the operation of the PV between the maximum power point tracking (MPPT) mode and power-curtailed mode th... [more]

This study presents the modeling of wood chips pyrolysis, considering the initial moisture content and taking into account the near-parallelepiped geometry of common wood chips, which is not available among the simulated shapes of wood in the literature. The goal is to extend the research and generate useful data on how different varieties of shapes and initial moisture contents influence wood chips pyrolysis. The effects of temperature and thickness variation on the pressure of volatile products, core temperature, and densities of pyrolysis products were studied. The model was validated with the mass fraction of experimental data obtained from beechwood chips with a density of 700 kg/m3 and thickness of 10 mm−30 mm at 973.15 K−1273.15 K. The mean absolute error (MAE) and mean relative error (MRE) values were, respectively, 0.066 and 10.376% at 973.15 K, and 0.065 and 22.632% at 1273.15 K. High temperature favored the rate of biocharcoal production from the surface to the core, though... [more]

Infeasible solutions or negative expected values of future climate information are undesired problems if climate policies are adopted under Cost-Effectiveness Analysis (CEA) to reach uncertain temperature targets. Cost-Risk Analysis (CRA) was developed to resolve these issues. It allows for a trade-off between expected welfare losses of mitigation and avoided risk of transgressing a climate target with a certain probability of compliance (Safety). Some of the significant contributions of this paper are: (i) It updates the Probabilistic Integrated model of Climate and the Economy (PRICE) as a probabilistic version of the latest version of the Dynamic Integrated Climate-Economy model (DICE) 2016, and it extends the model to run welfare-maximizing decision analytic frameworks readily. (ii) It highlights that the standard method of applying CRA (Old CRA) leads to an extra welfare cost. (iii) It proposes revised instruction on how to use CRA. (iv) It simulates and compares welfare-maximizin... [more]

This study presents applications of artificial neural networks and nonlinear optimization techniques for fault location in transmission lines using simulated data in an electromagnetic transient program and actual data occurring in transmission lines. The localization is performed by a modular structure of 4 neural networks and by the minimization of objective functions descriptive of the problem, defined according to the parameters of the line and the type of short circuit, submitted to the methods Quasi-Newton, Ellipsoidal, and Real Polarized Genetic Algorithm. The results obtained are compared statistically with those of a classical analytical method. The analysis of the variance of location errors presented by the methods revealed, with 5% significance, statistical evidence that allowed the conclusion that the type of method used affects fault location indication. In simulated scenarios, minor errors were obtained with the neural network and larger with the analytical method. For f... [more]

Currently, the primary method for determining the object coordinates is positioning using Global Navigation Satellite Systems (GNSS) supported by Inertial Navigation Systems (INS). The main goal of this solution is to ensure high positioning availability, particularly when access to satellite signals is limited (in tunnels, areas with densely concentrated buildings and in forest areas). The aim of this article is to determine whether the GNSS/INS system supported by the RTK receiver is suitable for the implementation of selected geodetic and construction tasks in railway engineering, such as determining the place and extent of rail track deformations (1 cm (p = 0.95)), the process of a rapid stocktaking of existing rail tracks (3 cm (p = 0.95)) and for design and construction works (10 cm (p = 0.95)), as well as what the impact of various terrain obstacles have on the obtained positioning accuracy of the tested system. During the research, one INS was used, the Ekinox2-U by the SBG Sys... [more]

Buildings play a significant role in terms of energy consumption and polluting emissions production across Europe and this huge contribution to consumption and environmental impact becomes even more alarming when attention is switched from single buildings to entire urban systems. Although great efforts have been made to support energy efficiency investments, distrust and suspicion are shared attitudes among private investors (and stakeholders in general) towards large-scale implementation of these kinds of projects. Within this framework, on-bill schemes were implemented in the United States more than 30 years ago. In particular, on-bill energy efficiency is a method of financing energy efficiency improvements that uses the utility bill as the repayment vehicle. A detailed analysis of on-bill schemes is currently addressed by the H2020 RenOnBill project, which focuses on these schemes to enhance and support large-scale investments for energy efficiency and deep residential stock renov... [more]

The main aim of this review is to present the current state of the research and applications of superconductivity and plasma technologies in the field of energy and environmental protection. An additional goal is to attract the attention of specialists, university students and readers interested in the state of energy and the natural environment and in how to protect them and ensure their sustainable development. Modern energy systems and the natural environment do not develop in a sustainable manner, thus providing future generations with access to energy that is generated from renewable sources and that does not degrade the natural environment. Most of the energy technologies used today are based on non-renewable sources. Power contained in fuel is irretrievably lost, and the quality of the energy is lowered. It is accompanied by the emissions of fossil fuel combustion products into the atmosphere, which pollutes the natural environment. Environmental problems, such as the production... [more]

Multilevel Inverters (MLIs) are widely sought after in medium-voltage applications like electric ships, electric aircraft, and renewable energy integration due to excellent advantages like lower device stress, better power quality, and modularity. However, non-sinusoidal excitations from MLIs pose a serious problem to motor-insulation and lead to their premature breakdown. This paper investigates stress in medium-voltage motor insulation when the stator winding is excited by 3-, 5-, and 7-level multilevel inverter output waveforms. The effect of firing angle on insulation stress is also studied for each of the multilevel inverters. Results show that in addition to the number of output voltage levels, PWM wave shape is a critical factor which affects the insulation stress. Both these factors work together to impact the insulation health. A strong correlation is shown between the increase in the voltage root mean square (RMS) value and increase in dielectric stress when ignoring the dv/d... [more]

This paper investigates the interrelations between stock returns and crude oil prices for European oil-importing/exporting countries. A vector autoregression (VAR) model is applied to estimate the significance of stock market responses to changes in oil prices during the pandemic period 2019−2021. A Granger causality test is applied to find the direction and the intensity of the relation between crude oil and the indices of the European stock markets. The findings of this paper hold with or without the COVID-19 pandemic episode and reveal the interaction between the European stock markets and the crude oil prices. The results indicate that in steady periods, before the COVID-19 outbreak and after the announcement of vaccinations, there is no interdependence between crude oil and stock prices, whereas in high volatility periods, the causality from stock markets to oil prices increases and both oil-exporting and -importing countries are equally influenced. These findings have implication... [more]

Within the context for deep geological disposal (DGD) of high-level radioactive waste (HLW), thermo-hydro-mechanical (THM) coupled numerical modeling has become significantly important for studying the safe disposal of HLW. In this work, a 3D mechanical module is incorporated into the thermal−hydraulic (TH) coupled code TOUGH2, thus forming an integrated THM coupled simulator referred to as TOUGH2Biot. The Galerkin finite element method is used to discretize the space for rock mechanical calculation. The mechanical process is sequentially coupled with the fluid and heat flow processes, which further gives feedback to the flow through stress-dependent hydraulic properties (e.g., porosity and permeability). Based on the available geological data at the Meuse/Haute-Marne Underground Research Laboratory (MHM URL) in France, the improved simulator is used to analyze the coupled THM behaviors of the Callovo-Oxfordian claystone (COx) induced by thermal loading. The anisotropy of material para... [more]

In this article, Cattaneo Christov heat transfer analysis in nanofluid (Ferro Fe3O4 and Aggregation) flow between two parallel rotating disks with different velocities determined. The relaxation time, velocity slip, heat convective boundary condition, and heat generation are also presented. The governing partial differential equation (PDEs) model is converted into a set of nonlinear ordinary differential equations (ODEs) system by similarity variables. The solution is computed of the resulting ODEs system by using the Runge Kutta (Rk) method. Here a decline is noticed in the tangential velocity for nanoparticles (Fe3O4 and Aggregation nanoparticle) for higher values of the porosity parameter (λ1), slip parameter γ1, magnetic parameter (M) and Reynolds number (Rer), while tangential velocity arises for higher values of rotation parameters (ß1). This reduces the temperature field for nanoparticles by higher values of Eckert number (Ec), Prandtl number (Pr), Reynolds number (Rer), porosit... [more]

Based on the energy storage type of hydraulic wind turbines (HWTs) and in view of the unit frequency drop problem under high wind power proportion conditions, this paper proposes a method of primary frequency control under maximum power point tracking (MPPT). HWT power output is affected by wind speed randomness and volatility. In addition, traditional wind turbines do not have inertial adjustment ability, leading to a decrease in the frequency stability of the power system caused by the increase in wind power permeability. In the paper, a hydraulic energy storage system and synchronous generator are combined to carry out primary frequency modulation, and a mathematical model of the hydraulic energy storage system, the hydraulic main transmission system, and the generator active power regulation system after grid connection is established. By analyzing the load changing rules of power systems and frequency fluctuation caused by the power system load after the wind turbine is grid-conne... [more]

Exergy-based methods support the identification of thermodynamic inefficiencies and the discovery of optimization potentials in thermal engineering applications. Although a large variety of simulation software is available in this field, most do not offer an integrated solution for exergy analysis. While there are commercial products on the market with such capabilities, their access for research and educational purposes is limited. The presented open-source software offers an integrated and fully automated exergy analysis tool for thermal conversion processes. In a first step, physical exergy is implemented, and the tool is then applied to three different example plants to highlight its capabilities and validate the implementation: A solar thermal power plant, a supercritical CO2 power cycle, and an air refrigeration cycle. The respective models and the results of the analyses are presented briefly. By providing the results in modern data structures, they are easily accessible and pos... [more]

In the effort to combat climate change, the CO2 emissions of the aviation sector must be reduced. The traffic caused by numerous types of ground vehicles on airport aprons currently contributes to those emissions as the vehicles typically operate with combustion engines, which is why an electrification of those vehicles has already begun. While stationary conductive charging of the vehicles is the current standard technology, dynamic wireless charging might be an attractive technological alternative, in particular for airport aprons; however, designing a charging network for an airport apron is a challenging task with important technical and economic aspects. In this paper, we propose a model to characterize the problem, especially for cases of multiple types of vehicles sharing the same charging network, such as passenger buses and baggage vehicles. In a numerical study inspired by real-world airports, we design such charging networks subject to service level constraints and evaluate... [more]

A symmetric single-source 7-level DC-AC converter with voltage gain of 3 and self-voltage balance is presented by combining the Class-D amplifier and the diode-clamped DC-AC converter. There is only one switch is switched for any time in this circuit. As a result, the conversion efficiency can be upgraded significantly as well as the control strategy can be simplified considerably. In the paper, the operation principle and circuit design of this converter are analyzed in detail, and its feasibility and effectiveness are verified by simulation and digital control, respectively.

The decentralization of power generation driven by the rise in the adoption of distributed energy resources paves the way for a new paradigm in grid operations. P2P energy trading is beneficial to the grid as well as the connected peers. A blockchain-based smart contract is well suited to transparently facilitate trades between energy consumers and producers without the services of intermediaries. In this paper, Ethereum-based smart contracts that facilitate double energy auction and spinning reserve trading are developed with Solidity, compiled, and deployed within the Remix IDE. Willing energy sellers/buyers submit offers/bids to a contract that implements the double auction procedure. In order to fulfil energy supply obligations, sellers are also able to purchase spinning reserves via another smart contract. The smart contracts’ effectiveness in performing the auction procedure and making payments is confirmed using an energy/reserve market scenario. The proposed scheme encourages f... [more]

The effect of three kinds of fuels used to supply a diesel engine on its characteristics, fuel consumption, and emissions was studied. The fuels comprised pure diesel, a blend of diesel with 6% of methyl ester of yellow grease in the form of rapeseed oil, and a blend of diesel with methyl ester of brown grease in the form of goose fat. The chromatographic analysis was conducted for these fuels, and the results are presented. Two tests, comprising measurement of fuel consumption and engine emissions, were conducted on a vehicle with a diesel engine operating under zero load and under full load. The engine’s characteristics, including both power and torque versus speed, were determined under full engine load. The results of these tests are presented in this paper. The results indicated that the use of different methyl ester-based biodiesel blends with the same content of diesel to supply the diesel engine resulted in different fuel consumption and emissions of the engine not only in comp... [more]

Due to the population’s growing need for energy and the increasing impact of the phenomena of global warming and climate change on a global level, it becomes imperative to diminish energy consumption worldwide. For this reason, a deeper understanding of factors that encourage energy-saving habits and overall lifestyle is required. This research examined the factors that hold an impact on the adoption of energy-saving habits in Romania. It used eight constructs that were checked to see if they influence the individuals’ intentions to save energy. The research used a quantitative analysis approach, with primary data assembled through a survey of the population from six developed counties in Romania. In order to investigate and assess the data, structural equation modeling (SEM) was used. The results show that environmental awareness, perceived consumer effectiveness and a collectivistic perspective affect individuals in implementing energy-saving habits (in their life) in a significant a... [more]

The increase in the number of new energy sources connected to the grid has made it difficult for power systems to regulate frequencies. Although battery energy storage can alleviate this problem, battery cycle lives are short, so hybrid energy storage is introduced to assist grid frequency modulation. In this paper, a hybrid energy storage system composed of battery energy storage and super-capacitor energy storage systems was studied, and a comprehensive control strategy was proposed. Firstly, by setting the frequency dead zone of the energy storage to be smaller than that of the thermal power unit, the frequent action of the thermal power unit was avoided. Secondly, virtual inertial control and virtual droop control were effectively combined. Then, the state of charge of battery energy storage and super-capacitor energy storage was considered so that they could operate in harmony. Finally, a simulation model was built in MATLAB/SIMULINK, and case studies were conducted to verify the... [more]

Modern ships discharge large amounts of energy into the environment. More specifically, internal combustion engines (ICE) of commercial and passenger ships waste significant amounts of thermal energy at high temperature through their exhaust gases that are discharged to the atmosphere. A practical approach of recovering some amount of this energy is by using thermoelectric generator systems, which can convert thermal into electrical energy, given that there is a significant temperature difference. It is the aim of this work to propose a thermoelectric generator to recover energy from the exhaust gases of marine ICEs. The proposed thermoelectric generator uses the outside surface of the ICE manifold as the hot side of the thermoelectric module, while the cold side is maintained at a low temperature through a heat sink and induced water flow. The goal of this work is to design this thermoelectric generator and identify the configuration that produces the maximum electric power. The analy... [more]