Conservation through voltage reduction (CVR) aims to reduce the peak load and energy savings in electric power systems and is being deployed at various utilities. The effectiveness of the CVR program depends on the load characteristics, i.e., the sensitivity of the load to voltage variation, and voltage regulation device settings. In the current literature, there is a lack of discussion on the CVR factor calculation using different measurements, and there is a lack of method for active power loss estimation using substation measurements. This paper provides insights into CVR factor calculation based on the measurements captured at the substation and those at the load location. This paper also proposes a new method based on curve fitting and artificial neural network to estimate the active power loss using input active power, input reactive power and input voltage at the substation. The CVR comparison study conducted in this paper helps in understanding the factors affecting CVR factor... [more]

Saving energy while maintaining a high-quality internal environment is an increasingly important scientific and technological challenge in the building sector. This paper presents the results from a long-term study on thermal comfort in a passive house situated in the south of Poland. The building was constructed in 2010 with the use of prefabricated, lightweight technology. The main energy source is a ground source heat pump which powers the floor heating and DHW. The building is also equipped with a mechanical ventilation system with heat recovery and a ground source heat exchanger. A lightweight building structure which has active systems with limited capabilities (especially for cooling) is a combination which increases the difficulty of maintaining a proper inner environmental condition. Extensive experimental investigations on hygrothermal performance and energy use have been carried out in the building for several years. The measurement results, such as inner air temperature and... [more]

Classical thermal rectification arises from the contact between two dissimilar bulk materials, each with a thermal conductivity (k) with a different temperature dependence. Here, we study thermal rectification in a Si(1−x)Ge alloy with a spatial dependence on the atomic composition. Rectification factors (R = kmax/kmin) of up to 3.41 were found. We also demonstrate the suitability of such an alloy for logic gates using a thermal AND gate as an example by controlling the thermal conductivity profile via the alloy composition. This system is readily extendable to other alloys, since it only depends on the effective thermal conductivity. These thermal devices are inherently advantageous alternatives to their electric counterparts, as they may be able to take advantage of otherwise undesired waste heat in the surroundings. Furthermore, the demonstration of logic operations is a step towards thermal computation.

A grid-connected inverter’s stability is easily influenced by the system’s internal and external characteristics, especially when the grid-connected inverter is connected to the grid by an LCL filter, which complicates the system design and operating conditions. To handle the problem of disturbance in the high-order grid-connected system of the inverter, a linear active disturbance rejection control (LADRC) strategy based on LCCL (which divides the capacitor of the LCL filter into two halves in a specified proportion) is proposed in this paper. First, the system is reduced from third order to first order by using the split capacitor control method, which solves the difficulties of complicated LCL grid-connected inverter controller design and easy resonance. Meanwhile, the internal and external disturbances of the inverter system are treated as generalized disturbances. Then, the LADRC control is used to adjust the closed-loop system’s parameters, which enhances the quality of the grid... [more]

Recent innovations in HVDC extruded cable systems require the development of reliable and safe cable accessories. Cable accessories are made of several insulating materials and contain several interfaces. Interfaces made of different materials can cause electric field distortion and localized enhancement of the field. In addition, the internal temperature profiles of accessories differ depending on load conditions or installation environments, which may lead to an increase in or loss of interfacial pressure due to changes in the mechanical properties of materials. The loss of interfacial pressure degrades the contact state between materials. The micro voids formed due to pressure loss can cause partial discharge and tree, which in turn can lead to reduced lifespan and failure of the cable system. Therefore, it is necessary to study the electrical and mechanical characteristics of cable accessories considering various transient states. However, there is a limit to experimentally analyzi... [more]

The paper is a continuation of the research works of the authors. The aim of it is identifying the electromagnetic environment in which the control equipment of the short-circuit test stand operates. Exceptional attention was devoted to the issues related to the operation of the time-phase controller system. Measurements and identification of the electromagnetic environment were carried out on a specific short-circuit test stand, where short-circuit currents are generated by the medium-voltage (MV) short-circuit transformers. Short circuit tests are always preceded by powering the MV side of the test transformer by unloading the low-voltage (LV) side. Thereafter, the controller must wait for the release of the operator to start the test. Sometimes an electromagnetically disturbed controller starts the test without release. Such situation is undesired and can be destructive for the tested objects. Identification of the transient fields during the powering of the test transformer is indi... [more]

Explainable Artificial Intelligence (XAI) methods demonstrate internal representation of data hidden within neural network trained weights. That information, presented in a form readable to humans, could be remarkably useful during model development and validation. Among others, gradient-based methods such as Grad-CAM are broadly used in an image processing domain. On the other hand, the autonomous vehicle sensor suite consists of auxiliary devices such as radars and LiDARs, for which existing XAI methods do not apply directly. In this article, we present our adaptation approach to utilize Grad-CAM visualization for LiDAR pointcloud specific object detection architectures used in automotive perception systems. We try to solve data and network architecture compatibility problems and answer the question whether Grad-CAM methods could be used with LiDAR sensor data efficiently. We showcase successful results of our method and all the benefits that come with a Grad-CAM XAI application to a... [more]

Subsea connectors are of a critical part for the sealing of subsea production systems. The working environment makes cracks initiate easily on subsea connector sealing rings. In order to ensure the safety and reliability of the sealing rings, it is necessary to study the crack’s influence on them. In this study, the main parameters that may influence stress intensity factors at crack tip are discussed. The sealing requirements of the subsea connector metal sealing rings were conducted. A finite element model was established to obtain the maximum equivalent stress and maximum equivalent plastic strain of crack-free sealing ring. Meanwhile, the influence of crack depths, crack positions, and crack angles on the sealing performance in preload and operating states was simulated through changing XFEM crack’s parameters in ABAQUS software, as well as their influence on stress intensity factors at the crack tip. The research shows that although the cracks have little effect on the sealing per... [more]

To address the huge market of renovation of multi-apartment buildings, minimal-invasive decentral serial-renovation solutions are required. One major challenge in the design of decentral heat pumps is to find the optimal balance between, on one hand, compactness and pleasant design, and on the other hand, efficiency and minimal sound emissions. A comprehensive holistic design and optimization process for the development of decentral heat pumps, from the component level, to the system level, and up to the building level, is developed. A novel façade-integrated speed-controlled exhaust air to supply air heat pump combined with a mechanical ventilation system with heat recovery and recirculation air was developed and simulated in a reference flat. Compared to a traditional supply air heat pump without recirculation, it shows only slight performance improvement, but allows significantly better thermal comfort and control, independently from the hygienic air flow rate and from the heating a... [more]

A variety of mathematical models are available to estimate the thermal performance of buildings. Nevertheless, mathematical models predict the thermal performance of buildings that might differ from the actual performance. The hot box is a widely-used test apparatus to assess the actual thermal performance of various building envelope components (walls, roofs, windows) in the laboratory. This paper presents the process of designing, constructing, and calibrating a unique small-scale hot box apparatus. Despite its smaller metering area (1.0 m × 1.0 m), this apparatus met the key requirements (below ±0.25 °C fluctuations in chambers’ air temperature, and below 2.0% variation from the point-to-point temperature in reference to the temperature difference across the specimen) as prescribed in the ASTM C1363 and ISO 8990 standards. The walls of this apparatus are uniquely constructed using vacuum insulation panels or VIPs. The efficient and novel use of VIPs and workmanship during the constr... [more]

In today’s socio-economic context where environmental protection and sustainable development are equally important, how renewable energy enterprises can achieve sustainable development has become a topic of academic interest in recent years. This paper investigates the link between sustainable growth (SG) of renewable energy firms, resource endowment (RE), and environmental regulatory (ERs) issues through a fixed-effects model and a GMM model. Through empirical analysis, it was found that economical environmental regulations have the greatest positive impact on sustainable growth, followed by legal environmental regulations and supervised environmental regulations. Resource endowment is positively related to sustainable growth for non-state-owned renewable energy enterprises, but the negative impact on sustainable growth reflects the effect the of “resource curse”. In addition, resource endowment has a negative moderating effect on environmental regulations and sustainable growth. Thus... [more]

Different types of distributed generation (DG) units based on renewable and non-renewable energy sources can create a local energy system in microgrids. The widespread penetration of distributed energy resources (DERs) has affected many power system issues, such as the control and operation of these networks. For the optimal operation of microgrids, optimal energy planning and management in the new space governing the distribution system requires extensive research and analysis. Getting acquainted with the latest research about the evaluation of the problems and challenges in the design of control systems plays an important role in providing a guidance map for researchers to find the recent challenges and propose new solutions. This paper tried to list the challenges of distributed generation sources for MG applications, opportunities, and solutions. These challenges are reported in hierarchical control strategies and power-sharing categories. Therefore, Model Predictive Control (MPC)-... [more]

SF6/CF4 mixture is considered a potential substitution for SF6 in gas-insulated equipment owing to the considerable insulation and low temperature characteristics of CF4. This paper concerns the substitutability of the mixture on the surface flashover property. Epoxy resin composites for solid insulators are applied since flashover at the insulator interface often occurs and results in severe damage to the safe operation of the equipment. Two kinds of electrode systems are designed to study DC flashover properties with different electric field uniformities. The obtained result shows that the flashover voltage in the 20% SF6/80% CF4 mixture achieved more than 70% of the voltage in SF6 at the same pressure. The mixture shows considerable synergy in the surface flashover process and performed different tendencies with varying gas pressures and contents under different electrode systems due to the influence of surface accumulated charge. Moreover, it is considered that surface charge due t... [more]

This paper describes the simulative approach to calibrate an already extremely highly turbocharged industrial diesel engine for higher low-speed torque. The engine, which is already operating at its cylinder-pressure maximum, is to achieve close to 30 bar effective mean pressure through suitable calibration between the compression ratio, piston-bowl shape and injection strategy. The basic idea of the study is to lower the compression ratio for even higher injection masses and boost pressures, with the resulting disadvantages in the area of emissions and fuel consumption being partially compensated for by optimizations in the areas of piston shape and injection strategy. The simulations primarily involve the use of the 3D CFD software Converge CFD for in-cylinder calibration and a fully predictive 1D full-engine model in GT Suite. The simulations are based on a two-stage turbocharged 1950 cc four-cylinder industrial diesel engine, which is used for validation of the initial simulation.... [more]

The artificial neural network method has been widely applied to the performance prediction of fillers and evaporative coolers, but its application to the dew point indirect evaporative coolers is rare. To fill this research gap, a novel performance prediction model for dew point indirect evaporative cooler based on back propagation neural network was established using Matlab2018. Simulation based on the test date in the moderately humid region of Yulin City (Shaanxi Province, China) finds that: the root mean square error of the evaporation efficiency of the back propagation model is 3.1367, and the r2 is 0.9659, which is within the acceptable error range. However, the relative error of individual data (sample 7) is a little bit large, which is close to 10%. In order to improve the accuracy of the back propagation model, an optimized model based on particle swarm optimization was established. The relative error of the optimized model is generally smaller than that of the BP neural netwo... [more]

We have established a simulation platform for the machine−electro-hydraulic coupling system of the transmission system and the control system to study the root causes of the problems of large shifting impact and slow change of the machine tool transmission system. The dynamic analysis of the gear shift work of the gearbox was carried out, and the main factors affecting its shift instability were studied. With the impact and sliding power as the optimization goals, the shift quality is optimized based on the multi-objective genetic algorithm. Through the shift experiment, it was found that the power interruption phenomenon during the shift process was eliminated after optimization, and the quality of the shift was improved. Simulated planetary row wheel gear meshing force was found in the same gear, and the second planetary row gear meshing force was the largest among the planetary rows. The stress of the node near the top of the tooth is greater than the stress of the node near the nod... [more]

Fault probability rises with an increase in the number of current sensors in multi-phase permanent synchronous motor (PMSM) drives. This paper proposes an improved axis rotation method for fault diagnosis and tolerant control to make the multi-phase PMSM drives against current sensor loss signal and gain faults. This method can effectively diagnose and distinguish faults without selecting a threshold value, and the degree of fault can be further estimated. The proposed method makes current sensor fault diagnosis and tolerant control become an integrated module. The validity and accuracy of the proposed method is verified by different fault diagnoses and tolerant control experiments of a 9 kw nine-phase PMSM drive.

State of charge (SOC) is the most important parameter in battery management systems (BMSs), but since the SOC is not a directly measurable state quantity, it is particularly important to use advanced strategies for accurate SOC estimation. In this paper, we first propose a bidirectional long short-term memory (BiLSTM) neural network, which enhances the comprehensiveness of information by acquiring both forward and reverse battery information compared to the general one-way recurrent neural network (RNN). Then, the parameters of this network are optimized by introducing a Bayesian optimization algorithm to match the data characteristics of lithium batteries with the network topology. Finally, two sets of lithium battery public data sets are used to carry out experiments under different constant temperature and variable temperature environments. The experimental results show that the proposed model can effectively fit the actual measurement curve. Compared with traditional long short-ter... [more]

The last decade has seen an exponential interest in conventional and unconventional energy issues. This trend has also extended to road transport issues and is driven by expectations to minimize fuel and/or energy consumption and negative environmental impact. In the global literature, much attention is focused on the work of autonomous transport, both passenger and trucks, and on the phenomena of platooning. The paper presents original aerodynamic and aeroacoustic tests of heterogeneous vehicle columns. In the work, models of a car, a van and a truck were built, followed by heterogeneous columns with different distances between the vehicles. Computational fluid dynamics (CFD) methods and two turbulence models, k−ω shear stress transport (SST) and large eddy simulation (LES), were used in this study. The study enabled the determination of drag coefficients and lift force. Application of the Ffowcs Williams−Hawkings (FW-H) analogy allowed for the determination of the distributions of so... [more]

Road freight transport involves many adversities, along with the growing effect of carbon dioxide transmitted by vehicles on the natural environment, greenhouse gas emissions, or extensive energy use. Within the smart mobility concept, the acknowledged management of enterprises’ relationships with customers within their service is profoundly determined by the deployment of compelling Intelligent Transportation Systems (ITSs) applications in forming united cooperation with the customers. The paper proposes selected ITS applications as an advancement of logistics customer service in road freight transport enterprises that is divided into a group of six applications which are critical within the area of vehicle support, improving the energy efficiency of transport and reducing the negative impact of transport on the natural environment, reducing transport time but increasing connectivity and comfort, as well as a group of ten different applications chosen as crucial for general management... [more]

A novel modular Transformerless, Self-balanced, Static Synchronous Series Compensator (TSB-SSSC) capable of delivering ultra-high current, with the objective of dynamically balancing the impedance of the transmission power grid, is proposed. Balancing transmission lines is crucial in power optimization and delivery because it increases the power transfer capability without building new power lines. The transformerless SSSC needs to support and control the line current from a few hundred to several thousand amperes. This paper presents how the ultra-high current architecture of the TSB-SSSC is achieved by operating multiple converters with self-balancing capabilities in parallel. The mechanism of self-balancing is based on the intrinsic physics of the capacitor and is enabled by a passive network of capacitor equalizers that keep the capacitor voltage equal during switching disconnection. The second self-balancing system consists of an inductive component that balances possible differen... [more]

This study investigated the suitability of stone fruit seed as a source of biodiesel for transport. Stone fruit oil (SFO) was extracted from the seed and converted into biodiesel. The biodiesel yield of 95.75% was produced using the alkaline catalysed transesterification process with a methanol-to-oil molar ratio of 6:1, KOH catalyst concentration of 0.5 wt% (weight %), and a reaction temperature of 55 °C for 60 min. The physicochemical properties of the produced biodiesel were determined and found to be the closest match of standard diesel. The engine performance, emissions and combustion behaviour of a four-cylinder diesel engine fuelled with SFO biodiesel blends of 5%, 10% and 20% with diesel, v/v basis, were tested. The testing was performed at 100% engine load with speed ranging from 200 to 2400 rpm. The average brake specific fuel consumption and brake thermal efficiency of SFO blends were found to be 4.7% to 15.4% higher and 3.9% to 11.4% lower than those of diesel, respectively... [more]

Based on the Reynolds time mean N-S equation and standard k-ε turbulence model and using Computational Fluid Dynamics technology, this study aims to integrate the brake pump to carry out numerical simulation. Through the adoption of different arrangements of impending height and spacing, the hydraulic characteristics of the full tubular pump unit are analyzed. The two-dimensional streamline, velocity and pressure distribution, and three-dimensional streamline, axial velocity and vorticity distribution of the front pool of each scheme are displayed. The results show that the recommended pump installation height is 0.8 Dd, the maximum limit value of the pump station design specification; in the dual-pump mode, the recommended pump spacing is 2.00 Ds.

This present research examined the association among carbon emissions, financial development, economic growth, natural resources, and energy usage in GCC nations within the environmental Kuznets curve framework by applying the datasets between 1995 and 2019. It used some empirical approaches, including second-generation unit roots and cointegration methods and method of moments quantile regression (MMQR). We detected a cointegrating interconnection between carbon emissions and financial development, energy usage, economic growth, natural resources, and squared of economic growth in the long term. Furthermore, the findings of the MMQR reveal that economic growth, financial development, energy usage, and natural resources degrade the environment, as well as proving the presence of the EKC hypothesis. Moreover, the results also demonstrated that financial development greatly moderates energy usage in order to attain environmental sustainability. Furthermore, the fixed-effect ordinary leas... [more]

The article concerns the assessment of the energy consumption of inland waterway freight transport on river sections in the context of environmental management. The research question was: Does the choice of the route determine the total energy consumption of inland waterway transport and therefore affect the potential of cargo transport of this mode? The article aims to indicate the directions of energy consumption by inland waterway freight transport depending on the route selection, the volume of transport, and the length of the route. The study was carried out on nine sections of the Odra River in Poland during the years 2015−2020. Statistical and econometric techniques were used, i.e., ANOVA, generalized linear models, Eta coefficients, Lasso and Ridge regularization, and X-average control charts (Six Sigma tool). Based on early warning models, river sections were identified that favor the rationalization of energy consumption in terms of the network. The sensitivity of the energy... [more]