One of the most important measures taken in reducing the impact of climate change resulting from global warming is the production of energy from clean and renewable resources. Hydroelectric power plants are leading renewable energy sources. In this study, the effects of climate change on hydroelectric power plants, a renewable energy source, have been investigated. Dogancay I and II Hydroelectric Power Plants, which are built on the Sakarya River located in the Sakarya basin of Turkey, was selected as a study area. Moreover, the monthly average energy, runoff, and efficiency parameters of hydroelectric power plants and the monthly average precipitation, temperature, and humidity physical parameters of the Sakarya province, which is a working area, were considered. The length of time-series data is 48 months (2015−2018). Analysis of the data was performed with the innovative polygon trend analysis (IPTA) method, which is one of the newest trend analysis methods. When the studies in the... [more]

In this paper, the 3-D squeezing flow of viscous incompressible fluid between two parallel plates rotating at the same rate is investigated. The flow is observed under the influence of the varying magnetic field. The flow phenomena are modeled by utilizing the basic governing equations, i.e., equation of continuity, coupled Navier Stokes, and Magnetic Field equations. Using appropriate similarity transformations, the resultant partial differential equations are then transformed into a system of ordinary differential equations. The computational technique is developed via the Homotopy Analysis Method (HAM) to obtain the solution of transformed systems of ordinary differential equations. The influence of several engineering fluid parameters, such as squeeze Reynolds number, magnetic field strength parameter, and magnetic Reynolds number, on velocity and magnetic field components, are observed from different graphs. It has been investigated that by increasing the squeeze Reynolds number,... [more]

Globally, around half a million tonnes of spent nuclear fuel (SNF) will be in dry or wet storage by around 2050. Continued storage is not sustainable and this SNF must eventually either be disposed (the open nuclear fuel cycle) or recycled (the closed fuel cycle). Many international studies have addressed the advantages and disadvantages of these options which can be considered now in the framework of sustainable development and the three pillars of: economic, environmental and societal impacts. To inform this debate, a detailed survey of the available literature related to economic assessments of closed and open cycles has been undertaken—this complements an earlier review on environmental impacts. Results of economic assessments showing how the management of spent fuels in the open and closed cycles impacts the costs of the nuclear fuel cycle, are usually presented in terms of the levelised cost of electricity (LCOE). It is clear that the costs of the back end of the fuel cycle are a... [more]

Flexible supercapacitors are highly demanding due to their wearability, washability, lightweight property and rollability. In this paper, a comprehensive review on flexible supercapacitors based on conductive polymers such as polypyrrole (PPy), polyaniline (PANI) and poly(3,4-ethylenedioxtthiophne)-polystyrene sulfonate (PEDOT:PSS). Methods of enhancing the conductivity of PEDOT:PSS polymer using various composites and chemical solutions have been reviewed in detail. Furthermore, supercapacitors based on carbonized banana peels and methods of activation have been discussed in point. This review covers the up-to-date progress achieved in conductive polymer-based materials for supercapacitor electrodes. The effect of various composites with PEDOT:PSS have been discussed. The review result indicated that flexible, stretchable, lightweight, washable, and disposable wearable electronics based on banana peel and conductive polymers are highly demanding.

The economic crisis caused by the COVID-19 pandemic reinforces the problem of rising electricity prices, which mainly affects countries that are forced to pay ever-higher CO₂ emission allowance fees (e.g., Poland). In the light of signals confirming the need for intensive development of the wind energy market in the Baltic Sea region, the authors consider the need to examine this issue concerning Poland and the Baltic States (i.e., Lithuania, Latvia and Estonia) as extremely important and demanding. The development of the RES market is currently an absolute necessity. The immediate neighbourhood and similar general social and economic conditions of Poland and the Baltic States enable factual comparisons, reinforcing the rationale for choosing the adopted research area. The main objective of the study was to assess the development of the wind energy market in Poland in the background of the Baltic Sea bordering countries in the era of the COVID-19 pandemic, in order to try to answer the... [more]

Liquid often exists in the accumulator of the rotary compressor during the process of startup or defrost of air-conditioning systems. Too much liquid entering the compressor cylinder would result in excessive pressure caused by the liquid compression, which is a great threat to the compressor. The liquid return through the liquid-return hole is the key to ensure the stable operation of the compressor. In this paper, the liquid-return characteristics in the liquid-return holes of the accumulator, including the mass-flow rate, liquid velocity and pressure difference between the liquid-return holes, during the startup process of the R290 rotary compressor are numerically investigated. The numerical simulation using the fluent volume of fluid (VOF) method was experimentally validated with the error of 1.55%. The comparison of liquid-return characteristics using different refrigerants is conducted. Effects of refrigerant solubility in the oil, refrigerant/oil-mixture type, liquid-return-hol... [more]

The Reduced Asymmetric Neutral Point Clamped converter topology for unipolar driven, multiphase switched reluctance machines is proposed in this paper. This topology shares similarities with the conventional NPC and Asymmetric-NPC topologies, however it is unique in that the components for the capacitor string and outer semiconductor switches are shared among all the phases for a reduced component count. Some switching state combinations are not possible during commutation overlap between motor phases, resulting in minor torque transients during regenerative braking. A custom modulation scheme is implemented with fixed frequency, phase-shifted carrier waveforms that allow for automatic balancing of the neutral point voltage and interleaved switching of the semiconductor switches. A simple torque observer control architecture is used with minor adjustments for arbitrating torque contribution priorities between phases during handover.

As a key component to ensure the safety and stability of the surface-mounted permanent magnet motor rotor, stress research on the sleeve has long been a subject that has attracted researchers. Fiber-reinforced composite materials have the characteristics of high specific strength, high specific modulus, and low eddy current loss. The use of a fiber-reinforced composite material sleeve that can effectively reduce the thickness of the sleeve and structural weight, and can improve the power density of the motor is an inevitable trend of the development of high-performance permanent magnet motors. This paper summarizes the matching of fibers and resins of composite materials to the sleeve: the stress design criteria, stress calculation method, and stress influencing factors of the composite sleeve; two typical stress-forming methods of the composite sleeve; and the preloading effect of the sleeve, strength, and rotor prototype performance testing. This paper focuses on the application of t... [more]

This paper discusses the proper selection and interpretation of aggregated control performance indices values mirroring the quality of electrical energy generation by a turbine-generator set cooperating with a power system. Typically, a set of basic/classical and individual indices is used in energy engineering to ensure the mirroring feature and is related to voltage, frequency and active or reactive power deviations from their nominal values desired in the power system. In this paper, aggregated indices based on the sum of weighted integral indices are proposed, verified and built based on the well-known indices originating from control theory. These include an integral of the squared error (ISE) and an integral of the squared error multiplied by time (ITSE), applicable whenever an in-depth analysis and evaluation of various control strategies of the generation system is to be performed. In the reported research, the computer simulation tests verified their effectiveness in assessing... [more]

The use of renewable energy sources, such as wind, photovoltaics (PV), and hydropower, to supply facility agriculture may effectively mitigate food and environmental pollution problems and ensure continuity of the energy supply. The operating conditions of a hybrid system are complex, so the operating strategy is very important for system configuration and scheduling purposes. In the current study, first, a hybrid wind/PV/small-hydropower/facility-agricultural system was constructed. Then, the chaotic particle swarm method was applied to optimize hybrid system operation, and a scheduling strategy of the hybrid system was proposed. Finally, combined with an example, according to wind and PV power output and load curves, supply-to-load curves for wind, PV, and small hydropower were obtained. The operational strategy proposed in this study maximizes the utilization of wind and solar resources and rationally allocates hydropower resources. The aforementioned operational strategy provides a... [more]

Insulators are an important part of transmission lines; failure may threaten the operation of these transmission lines. For insulator defect detection, an optical image detection method based on deep learning and morphological detection is proposed. First of all, the Faster RCNN is used to locate the insulator and extract its target image from the detection image. In the second place, a segmentation method of insulator image is proposed to remove the background of the target image. In order to simplify insulator defect detection, an insulator shape transformation method is proposed to unify all types of insulator detection. Finally, a mathematical model is established in the binary image to describe the defect of the insulator. Experiments show that our proposed Faster RCNN can accurately detect the insulators in the image. Its AP is as high as 0.9175, and its Recall rate is as high as 0.98, which is higher than the common insulator recognition algorithm. The accuracy of the proposed d... [more]

Consumers are always influenced by external information before making decisions to purchase energy-saving electric appliances. However, the effects of different information sources are overlooked by previous studies. As a kind of green and safe appliance, the Heat Pump Water Heater (HPWH) is expected to be popular in the Chinese market. This study, based on an investigation in eastern China, will reveal the attitudes of potential consumers to HPWHs and verify the effects of different information sources. The results show that official information (Information from enterprises and governments) can arouse consumers’ positive attitudes toward HPWHs, yet can significantly reduce perceived usefulness among consumers, while unofficial information (Information from relatives and friends) negatively affects their attitudes. Although HPWHs are billed as energy-saving and eco-friendly appliances, consumers can obtain different information from online or offline interpersonal communications to ob... [more]

Temporary internal water pressure (IWP) during a construction period fundamentally affects the structural performance of spiral case structures (SCSs) in pumped-storage power plants (PSPPs). However, its actual role is rarely studied. This study focuses on this issue considering the complex construction-to-operation process of SCSs. An ABAQUS-based complete simulation procedure (CSP) is used with contact non-linearity considered. The contact-closing ratio is introduced to quantitively describe the contact status, and different design philosophies for temporary IWP are compared. The results show that the temporary IWP should be no greater than 80% of the minimum static headwater to ensure an overall contact-closing status under normal operating conditions in this study. The findings reveal that the cracking risk of concrete is negatively correlated with temporary IWP, while high temporary IWP is not suggested. Moreover, the stay ring actually shares a certain part of the unbalanced hydr... [more]

How to consider both the influence of weather and wind power in the modeling process of probability distribution of wind power forecast error (WPFE), and to emphasize the application value of conditional modeling, is rarely studied at present. This paper proposes a novel method of conditional probability distribution modeling for WPFE. This method uses a proposed MNSGA-II-Kmeans algorithm to perform multi-objective clustering of multi-dimensional influencing factors (MDIF), including weather and wind power. It can maximize the difference between the probability distributions of each MDIF mode’s WPFE while clustering, thus ensuring the application value of the conditional modeling way. Based on the clustering results, by using the versatile distribution to simulate the probability distribution of WPFE and the support vector machine to realize the recognition of MDIF modes, the specific conditional probability distribution function of WPFE can be provided to stochastic economic dispatch... [more]

The article presents the results of studies concerning raw hemp shives obtained from the Polish crop of industrial hemp as a loose-fill thermal insulation material. The study focuses mainly on the measurements of the pore size distribution, thermal conductivity and air permeability of material. An increase in the value of the thermal conductivity coefficient (0.049−0.052 W/(m·K)) was demonstrated with an increase in the bulk density. The porosity of the individual pieces of shives is 78.7% and the predominant number of pores is in the diameter range of 0.9−3 μm. The paper also presents an example of the use of the tested material as thermal insulation of the wooden frame wall. The heat flow analysis was performed in various wall variants (insulation thickness: 100, 200 and 300 mm and pressure difference 0, 5, 10 and 15 Pa). A clear influence of the variables on the temperature distribution was observed.

Insufficient rainfall in the dry season and scarcity of surface water has resulted in firms’ reliance on groundwater for agriculture in the northern part of Bangladesh. Most irrigation systems in the country are diesel or electric, which raises the cost and demand for energy and pollutes the environment. Utilizing the abundant sunshine and disseminating solar-based irrigation systems is expected to be a fittingly rewarding experience for irrigation purposes. Therefore, this study identifies the factors influencing the adoption of solar irrigation facilities (SIFs) and the impacts of their adoption on irrigation cost, return on investment (ROI), and production costs, using survey data collected from 405 rice farmers of Dinajpur district. The study employed three treatment effect estimators, namely inverse probability weighting (IPW), regression adjustment (RA), and inverse probability weighted regression adjustment (IPWRA), to address the potential selection bias issue. The results reve... [more]

Green façades with an active water regime and the water flowing through the substrate itself are not common. This system reduces the temperatures and incorporates the evapotranspiration, which could be more effective than by the regular green façades. The use of a double-skin façade with a ventilated air cavity can reduce the heat load, but the evapotranspiration can reduce it even more with additional benefits. Green façades could also serve as a key element for reducing the surface temperatures of the insulated metal panels (IMP), which are mostly used as a façade system for production facilities or factories. In this paper, a prototype of a double-skin façade, which consisted of vegetation board from recycled materials and IMP, is tested in a climate chamber to evaluate the function and benefits of such a combination. The outdoor skin is made from board, the surface of which is covered by the rooted succulent plants. Measurement results are represented as a direct comparison of sing... [more]

Colloidal semiconductor nanocrystals have generated tremendous interest because of their solution processability and robust tunability. Among such nanocrystals, the colloidal quantum dot (CQD) draws the most attention for its well-known quantum size effects. In the last decade, applications of CQDs have been booming in electronics and optoelectronics, especially in photovoltaics. Electronically doped semiconductors are critical in the fabrication of solar cells, because carefully designed band structures are able to promote efficient charge extraction. Unlike conventional semiconductors, diffusion and ion implantation technologies are not suitable for doping CQDs. Therefore, researchers have creatively developed alternative doping methods for CQD materials and devices. In order to provide a state-of-the-art summary and comprehensive understanding to this research community, we focused on various doping techniques and their applications for photovoltaics and demystify them from differen... [more]

In remote arctic communities, where access to a bulk electrical grid interconnection is not available, the implementation of islanded microgrids has been the most viable way to produce and distribute electricity services to their inhabitants. Historically, these islanded grids have relied primarily on diesel generators or hydropower resources to supply the baseload. However, this practice can result in increased expense due to the high costs associated with fuel transportation and the significant amounts of on-site storage necessary when fuel transportation is unavailable during winter months. In order to mitigate this problem, arctic microgrids have started to transition to a hybrid-source operational mode by incorporating renewable energy sources that are inherently variable in nature, such as wind or solar. Due to their highly stochastic behavior, these hybrid-source islanded microgrids can pose potential issues related to power quality due to introduction of rapid net load fluctuat... [more]

The use of renewable energies, such as Photovoltaic (PV) solar power, is necessary to meet the growing energy consumption. PV solar power generation has intrinsic characteristics related to the climatic variables that cause intermittence during the generation process, promoting instabilities and insecurity in the electrical system. One of the solutions for this problem uses methods for the Prediction of Solar Photovoltaic Power Generation (PSPPG). In this context, the aim of this study is to develop and compare the prediction accuracy of solar irradiance between Artificial Neural Network (ANN) and Long-Term Short Memory (LSTM) network models, from a comprehensive analysis that simultaneously considers two distinct sets of exogenous meteorological input variables and three short-term prediction horizons (1, 15 and 60 min), in a controlled experimental environment. The results indicate that there is a significant difference (p < 0.001) in the prediction accuracy between the ANN and LS... [more]

The paper presents the results of FEM 2D computational studies of a three-phase Direct Current Excited Flux Switching Machine (DCEFSM) electric motor with 15 rotor teeth and 36 stator teeth. The aim of the research was to minimize the cogging torque of the machine by changing the geometry of the rotor teeth and the size of the air gap between the stator and the rotor, with the operating torques unchanged. Computational studies were carried out on the influence of the width of the rotor teeth, the radius of the rounding of their corners, and the size of the air gap on the cogging torque and machine operating torques. The results of the calculations made it possible to select the dimensions of the rotor and the air gap in such a way that the maximum cogging torque was reduced more than six-fold, with the machine operating torques being unchanged. The calculations also showed that it is not possible to increase the value of the operational torques by further changes in the geometry of the... [more]

Glucose, sucrose, D(+)-xylose and α-lactose monohydrate are selected as additives relative to the negative electrolyte of Vanadium Redox Flow Battery (VRFB), with the aim of reducing vanadium permeation and improving electrochemical performance to mitigate capacity decay. The results of a charge−discharge test show that the cell with α-Lactose monohydrate in the negative electrolyte exhibits the best capacity retention. The capacity retention of a single cell employing 1 wt% α-Lactose monohydrate in the negative electrolyte was 71% after 30 cycles, which is 41.5% higher than 29.5% of the control group. Correspondingly, adding α-Lactose monohydrate into the negative electrolyte also significantly inhibits vanadium crossover and water transfer. Furthermore, the effects of additives on the performance of the negative electrolyte are studied by thermal stability experiments, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The stability experiments indicate that th... [more]

This paper presents the integration of shunt capacitors in the radial distribution grids (RDG) with constant and time-varying load consideration for the reduction of power losses and total annual cost, which turns to enhance the voltage profile and annual net savings. To gather the stated goals, three objective functions are formulated with system constraints. To solve this identified problem, a novel optimization technique based on the modification of particle swarm optimization is proposed. The solution methodology is divided into two phases. In phase one, potential candidate buses are nominated using the loss sensitivity factor method and in phase two the proposed technique first selects the optimal buses for the capacitor placement among the potential buses then it decides the optimal sizing of the capacitors as well. To demonstrate the performance in terms of efficiency and strength, the proposed technique is tested on IEEE 15, 33, and 69 bus system for the optimal placement and s... [more]

The current study employs a Granger causality test within a Quantile approach investigating CO2 emission determinants in China. Results show urbanization, financial development and openness to trade are leading determinants of CO2 emissions in China. These results highlight climate change issues while taking advantage of a new methodology to fill a gap in the current literature. Our findings show key implications for PRC government policy related to pollutant reduction policy.

The goal of this study was to examine the interlinkage of renewable energy, technology innovation, human capital, and governance on environment quality by using a panel quantile regression in Asian emerging economies over the period of 1990−2019. The results indicated that higher economic growth, population density, technological innovation in renewable energy, and exploitation of natural resources have significantly raised CO2 emissions in emerging Asia. Furthermore, larger capital, more use of renewable energy, green technology, and human capital development can improve environmental sustainability in Asia. As for governances, proxied by corruption rates, no evidence indicated that it has resulted in more damage, unlike earlier studies have suggested. The findings indicated that the three channels exposed in the Kuznets hypothesis can serve as a reference for proposals for environmental policies (scale of consumption, energy composition, and choice of technologies). There are opportu... [more]