Bathymetric surveys performed using small, unmanned vessels are increasingly used in coastal areas and regions difficult to access by hydrographic motorboats. Their geometric dimensions, manoeuvring parameters, low labour intensity, and costs of survey execution have allowed the unmanned survey vessel (USV) to be a commonly recognised surveying platform. It is equipped with a navigation system for positioning, maintaining a course or survey line, determining spatial orientation, and measuring depths. The operation zone of the global navigation satellite system (GNSS) in coastal water regions enables geodetic positioning in land-based surveys and of moving objects, also including, for example, a sounding vessel. Under difficult observational conditions, the positioning is limited by the obscuration of the upper hemisphere, i.e., the visibility of satellites and the reflection from high field buildings. This poses a threat to a small vessel operating at a very short distance from a hydro... [more]

Batteries have been the predominant energy storage system used in electric vehicles. Battery packs have a large number of cells that develop charge, thermal, and capacity imbalances over time, limiting the power, range, and lifetime. Electronic battery management and state of charge (SoC) equalization methods are necessary to mitigate such imbalances. Today, it is possible to find a wide range of battery equalization methods in the literature, but how to decide which of these methods should be applied in practice? This paper compares 24 SoC equalization circuits that are typically found in automotive applications. We employ an analytic hierarchy process (AHP) approach to rank these equalization circuits according to multiple decision criteria (energy efficiency, equalization speed, implementation and control simplicity, hardware size, and total price). We also prepared a survey to collect design preferences from multiple battery balancing experts from around the world in order to bette... [more]

The automotive sector is currently shifting its focus from traditional fossil fuels to electrification. The deployment of a Battery Management System (BMS) unit is the key point to oversee the battery state of the electric vehicle (EV) to ensure safety and performances. The development and assessment of electric vehicle models in turn lays the groundwork of the BMS design as it provides a quick and cheap solution to test battery optimal control logics in a Software-in-the-Loop environment. Despite the various contribution to the literature in battery and vehicle modeling, electric scooters are mostly disregarded together with a reliable estimation of their performance and electric range. The present paper hence aims at filling the gap of knowledge through the development of a numerical model for considering a two-wheeler. The latter model relies on the conservation energy based-longitudinal dynamic approach and is coupled to a Li-Ion Battery second-order RC equivalent circuit model for... [more]

Among the G20 countries, China is the only country to experience an increase in electricity generation from coal-fired thermal power plants from 2019 to 2020. This study aims to develop an analytical framework combining metafrontier data envelopment analysis with the logarithmic mean Divisia index for a detailed decomposition analysis of ‘mass-based’ energy-related CO2 reduction potential through efficiency improvements in coal-fired thermal power plants in China. The results show that inefficiency in power generation can be largely attributed to differences in the location of power plants and the production scale. Moreover, the impact of regional heterogeneity on the changes in power generation efficiency is more notable for the small−medium power plants in the northeast region than the large power plants in the western region in China. However, when focusing on the mass-based CO2 reduction potential associated with the regional heterogeneity, its positive effects in the western regio... [more]

Energy storage for medium- to large-scale applications is an important aspect of balancing demand and supply cycles. Hydropower generation coupled with pumped hydro storage is an old but effective supply/demand buffer that is a function of the availability of a freshwater resource and the ability to construct an elevated water reservoir. This work reviews the technological feasibility of hydropower generation and also pumped hydro storage and its geographical distribution around the world. There is also an emphasis on installations in the Middle East and North Africa (MENA) in terms of available capacity as well as past and future developments and expansions. A discussion is presented on a project taking place in the United Arab Emirates (UAE) in the Hatta region, which has a water reservoir that would be fit for utilization for pumped hydro storage applications. Once the project is commissioned in 2024, it will provide an estimated 2.06 TWh per year, helping the UAE achieve the goal o... [more]

The emissions of vehicles are measured in laboratories with roller-type chassis dynamometers, which simulate road driving resistances. Hub-coupled dynamometers, which are not included in the regulations for emission measurements, are commonly used for research and development purposes, for example, to assess powertrain capabilities, simulate on-road trips, and calibrate the control of individual wheels. As they do not need particular infrastructure and offer a wider range of applications, they could be a more economical alternative, especially if they could also be used for emission measurements for the type approval of vehicles. Nevertheless, the two types have not been directly compared in the literature, and, thus, their equivalency, especially regarding emission measurements, is not known. In this study, the emissions of a diesel and a gasoline plug-in vehicle were compared using the same analytical equipment and by switching only the roller and hub dynamometers. The diesel vehicle... [more]

In the context of the economic situation, international relations, and the consequences of COVID-19, the future competition pattern of crude oil trade is uncertain. In this paper, the crude oil international import competition and export competition networks are based on a complex network model. The link prediction method is used to construct a crude oil competition relationship prediction model. We summarize the evolving characteristics of the competitive landscape of the global crude oil trade from 2000 to 2019 and explore the reasons for the changes. Finally, we forecast the future potential crude oil import and export competition. The results indicate the following. (1) The crude oil import competition center is transferred from Europe and America to the Asia−Pacific region and it may continue to shift to developing regions. (2) At present, the competition among traditional crude oil exporters is the core of crude oil export competition, such as OPEC, Canada, and Russia. The United... [more]

Energy management strategies have a significant impact on the hydrogen economy of fuel cell trucks and the lifetime of battery and fuel cell systems. This contribution presents the design and optimal calibration of an energy management strategy that is adaptive to the battery and ambient temperatures. Indeed, fuel cell trucks face critical operating conditions due to high ambient temperatures or high loads on long uphill roads. However, the presented adaptive energy management strategy shifts the electric loads to the fuel cell system to limit the battery usage, avoiding accelerated degradation due to battery temperature peaks without hindering the hydrogen economy. The strategy design and calibration involves a multi-objective optimization of performance indicators related to hydrogen consumption, fuel cell degradation, battery thermal state, equivalent charge/discharge cycles, and charge control. This work uses AVL CAMEO to systematically vary the adaptive curve parameters to explore... [more]

The increased use of distributed energy resources, especially electrical energy storage systems (EESS), has led to greater flexibility and complexity in power grids, which has led to new challenges in the operation of these systems, with particular emphasis on frequency regulation. To this end, the transmission system operator in Great Britain has designed a control scheme known as Enhanced Frequency Response (EFR) that is especially attractive for its implementation in EESS. This paper proposes a Type-2 fuzzy control system that enables the provision of EFR service from a battery energy storage system in order to improve the state-of-charge (SoC) management while providing EFR service from operating scenarios during working and off-duty days. The performance of the proposed controller is compared with a conventional FLC and PID controllers with similar features. The results showed that in all scenarios, but especially under large frequency deviations, the proposed controller presents... [more]

The Korean government has declared the goal of net-zero-carbon emissions with a focus on renewable energy expansion. However, a high proportion of baseload generators and an increasing proportion of variable renewable energy (VRE) may cause problems in the power system operation owing to the low cycling capability of baseload generators and variability of VRE. To maintain system reliability, the government is planning to construct pumped-storage hydropower (PSH) plants, which can provide flexibility to the system. This study evaluated the operating cost savings obtained by different types of PSH: the adjustable-speed PSH (AS-PSH) and fixed-speed PSH (FS-PSH), based on the duck-curve phenomenon and the increase in spinning reserve requirement. In this study, the reserve-constrained unit commitment was formulated using a mixed-integer-programming considering the operational characteristics of AS-PSH and conventional generators. To consider the duck-shaped net-load environment, the projec... [more]

This paper presents a literature review of recent research on introducing the Industry 4.0 approach to improving energy efficiency, especially in the wood industry. While researchers focus on processes, service, and customer concepts, the effect on energy consumption is less addressed in these studies and applications. This paper focuses on previous works that discuss how to apply Industry 4.0 concepts to energy issues, such as to achieve better efficiency and performance for the industry in general and the wood industry in particular. The complexity of the study requires a multistep development. First, we define each concept separately and the relationships between them. Second, we apply a search algorithm to find related articles with specific terms, and then use the PRISMA method to select the most important ones, eliminating duplicates and excluding articles that do not mention energy efficiency and Industry 4.0 in the manufacturing or wood industry. Third, we explain and categoriz... [more]

Polyoxymethylene dimethyl ethers (PODE), as the most potential oxygenated alternative fuel for diesel engines, is widely investigated. Considering the importance of research on real driving emissions (RDE) and the few studies focus on the emission characteristics of the PODE/diesel blended fuels under real driving conditions, a portable emission measurement system (PEMS) was applied to measure the RDE of a heavy-duty tractor fueled with diesel or PODE/diesel blends. The tests were carried out in accordance with the relevant regulations of the CHINA VI emission standards. The second-by-second data from PEMS and the OBD system were utilized to construct engine transient operating maps. The results indicated that the addition of PODE can still decrease CO and PN emissions significantly under real driving conditions, although the low load conditions are still the areas of high brake specific CO and brake specific PN emissions. The NOx emissions, however, were not reduced as the results of... [more]

The well spacing for the development of tight reservoirs by multi-stage fracturing is continuously narrowed. Consequently, interwell interference during fracturing is more and more serious, accompanied by a host of issues in fracturing design and oil and gas production. However, the mechanism of interwell interference during fracturing is not explicit. The corresponding laws of the connectivity of rough fractures during fracturing, which plays a critical role in interwell interference, are not fully understood. In this study, on the basis of characterizing the roughness of fractures, a laboratory evaluation method for fracture connectivity was established. The connectivity characteristics of rough fractures and factors affecting the fracture connectivity are studied. The time and scale effects of fracture connectivity were discussed and their application in interwell interference was analyzed. The results show that the connectivity performance of rough fractures can be characterized by... [more]

Correlations for the Nusselt number for the fully-developed laminar flow of Carreau fluids through circular pipe subject to a uniform heat flux have been sought. Based on the mathematical expression, the Nusselt number could be obtained by numerical integration. To evaluate the Nusselt number for many conditions, an efficient integration method has been proposed. Using the obtained Nusselt number for different material constants and flow conditions, an improved correlation method has been proposed. The proposed correlation could reduce the maximum error from 3% to 0.9%.

Due to the limited available envelope area, height-constrained buildings integrated with photovoltaics require that more attention be given to the effective use of roofs. Thus, it is crucial to study the energy savings potential of previously neglected semitransparent photovoltaic (STPV) skylights. In this paper, the net energy consumption (NEC) of a room with STPV skylights and energy superiority compared to a reference window were investigated. The energy savings potential was then calculated for five representative cases located in different climate zones and daylight zones, according to the mandatory codes to be implemented in April 2022. Through a global sensitivity analysis, the extent to which each component of the NEC affects the energy savings potential was evaluated. The results indicate that STPV skylights exhibit promising energy savings potential in China. In temperate zones with excellent daylight conditions, an energy savings potential of 0.21 to 2.55 can be achieved, wh... [more]

The recent forecasts regarding the penetration of electric vehicles (EVs) in the transport market and their impact on national electricity distribution grids has presented new challenges in the fields of both of application and research. In this context, vehicle-to-grid (V2G) technology presents itself as an extremely valid solution in terms of application of the “demand side flexibility” paradigm. In this context, the aim of the paper is to analyze from a technical and economical point of view the use of EVs as new flexibility resources to provide network flexibility services in an Italian framework. Within this scope, a methodology for evaluating the flexibility service that a single EV or an EV fleet can offer, and therefore for estimating the EV storage system charge and discharge profile and determining its economic benefit, is proposed. Some numerical results and observations are reported to highlight possible incentive mechanisms for motivating EV end-users to offer flexibility... [more]

Hydrogen refueling stations (HRSs) are critical for the popularity of hydrogen vehicles (fuel cell electric vehicles—FCEVs). However, due to high installation investment and operating costs, the proliferation of HRSs is difficult. This paper studies HRSs with on-site electrolytic production and hydrogen storage devices and proposes an optimization method to minimize the total costs including both installation investment and operating costs (OPT-ISL method). Moreover, to acquire the optimization constraints of hydrogen demand, this paper creatively develops a refueling behavior simulation method for different kinds of FCEVs and proposes a hydrogen-demand estimation model to forecast the demand with hourly intervals for HRS. The Jensen−Shannon divergence is applied to verify the accuracy of the hydrogen-demand estimation. The result: 0.029 is much smaller than that of the estimation method in reference. Based on the estimation results and peak-valley prices of electricity from the grid,... [more]

A multi-fidelity micro combustor design approach is developed for a small-scale combined heat and power CHP system. The approach is characterised by the coupling of the developed preliminary design model using the combined method of 3D high-fidelity modelling and experimental testing. The integrated multi-physics schemes and their underlying interactions are initially provided. During the preliminary design phase, the rapid design exploration is achieved by the coupled reduced-order models, where the details of the combustion chamber layout, flow distributions, and burner geometry are defined as well as basic combustor performance. The high-fidelity modelling approach is then followed to provide insights into detailed flow and emission physics, which explores the effect of design parameters and optimises the design. The combustor is then fabricated and assembled in the MGT test bench. The experimental test is performed and indicates that the designed combustor is successfully implement... [more]

The electricity production opus in South Africa has transformed over the last few years from predominantly coal power generation to a blend of renewable energy generation. The necessity emerges to ascertain whether electrical transformer design philosophies in local manufacturers are contemporary in reference to customer specifications, under increasing penetration of harmonics and distortion as a result of increasing deployment of decentralized power systems. Accurate computation of transformer stray load loss is imperative in localizing the hotspot regions and design of adequate insulation system and consequently cooling system. This loss must also be met by manufacturers based on the customer specifications to avoid penalties. The review of current scientific works affirms the ongoing interest in utilizing the advancement of computational power for painstaking evaluation and management of stray load loss in electric transformers. This article confers overview research, evolution and... [more]

Cellular network operators are actively expanding network coverage and capacity by deploying additional base-stations to provide mobile services to customers in rural areas. The increasing deployment of cellular base-stations has increased the power consumption, energy cost, and associated adverse environmental impact. This paper addresses the feasibility of using renewable energy sources to power off-grid rural 4G/5G cellular base-stations based on Kuwait’s solar irradiance and wind potentials. More importantly, a hybrid renewable energy system will be designed and modeled to meet realistic energy demands of remote base-stations and determine the optimum size of the hybrid system components. Particularly, the hybrid off-grid system may incorporate wind turbines (WTs), photovoltaic (PV) solar panels, converters, a battery bank (BB), and a back-up diesel generator (DG). Two remote cell-sites are considered, namely: (1) Jal-Alayah and (2) Wafra, where the Jal-Alayah cell-site is characte... [more]

This paper focuses on the LiFePO4 (LFP) battery, a classical and one of the safest Li-ion battery technologies. To facilitate and make the cathode manufacture more sustainable, two Kynar® binders (Arkema, France) are investigated which are soluble in solvents with lower boiling points than the usual solvent for the classical PVDF binder. Li-LFP and graphite-Li half cells and graphite-LFP full cells are fabricated and tested in electrochemical impedance spectroscopy, cyclic voltammetry (CV) and galvanostatic charge-discharge cycling. The diffusion coefficients are determined from the CV plots, employing the Rendles-Shevchik equation, for the LFP electrodes with the three investigated binders and the graphite anode, and used as input data in simulations based on the single-particle model. Microstructural and surface composition characterization is performed on the LFP cathodes, pre-cycling and after 25 cycles, revealing the aging effects of SEI formation, loss of active lithium, surface... [more]

The cone-cylindrical pile foundation is a kind of shallow buried foundation, which needs to be open excavated and backfilled during construction. The density of the backfill is closely related to the refreezing process of the backfill. However, there is still a lack of relevant research on the relationship between backfill density and the refreezing process of backfill. The method of model experiment is selected to study the refreezing process of backfill under three backfill soil densities. The controlled density of backfill is 1.83, 1.62 and 1.36 g/cm3, and the times of freeze−thaw cycle is 14, 22 and 39, respectively. The main research findings are as follows: First, the effect of the initial temperature of the backfill on the refreezing is mainly reflected in the first three freeze−thaw cycles; the second is that the higher the density of the backfill, the faster the backfill responds to changes in outside air temperature, and the shorter the freezing time; third, the pile foundati... [more]

The technology of microseismic monitoring, the first step of which is event recognition, provides an effective method for giving early warning of dynamic disasters in coal mines, especially mining water hazards, while signals with a low signal-to-noise ratio (SNR) usually cannot be recognized effectively by systematic methods. This paper proposes a wavelet scattering decomposition (WSD) transform and support vector machine (SVM) algorithm for discriminating events of microseismic signals with a low SNR. Firstly, a method of signal feature extraction based on WSD transform is presented by studying the matrix constructed by the scattering decomposition coefficients. Secondly, the microseismic events intelligent recognition model built by operating a WSD coefficients calculation for the acquired raw vibration signals, shaping a feature vector matrix of them, is outlined. Finally, a comparative analysis of the microseismic events and noise signals in the experiment verifies that the discri... [more]

The landscape shaped by the energy industry is rich in various slender structures, such as smokestacks, cooling towers, and others. It is thus becoming increasingly important to effectively monitor the geometrical condition of all types of such structures. Slender structures are deformed elastically under loads due to wind. A proper analysis of the changes and deformations of such structures requires a continuous ground-based measurement system which allows the movement of the structure to be measured in two horizontal directions, from a significant distance and with a possibly reduced number of stations. For this purpose, two methods were implemented: a linear terrestrial laser scanning method (TLS) and an optical, direct distance measurement method—tachymetry (TCH). The least squares method was used to fit rings on various levels of the structure and then the centers of the rings were identified. The comparison of the identified ring centers enabled the axis of the structure to be me... [more]

The EOSOLAR project was designed to investigate the structure of the atmospheric boundary layer in an equatorial coastal zone, where the discontinuity of surface conditions induces non-stationarity gradients of wind speeds and the development of internal boundary layers. The proposed methodology considers several aspects of the sea−land transition meteorology that are essential for precisely estimating wind−solar energy potential and assessment of structural loads on wind turbines. Infrared (LIDAR) and acoustic (SODAR) ground-based remote sensing instruments and micrometeorological towers were installed in a near-shore equatorial area of northeast Brazil, in order to provide a comprehensive view of meteorological processes. This paper reports a description of the project study area, methodology, and instrumentation used. Details of instruments configurations, a validation of micrometeorology towers, and a comparison between the LIDAR and SODAR are presented. Results of the first field... [more]