Hybrid vehicles are now more common in response to increasing global warming. The hybridization of energy sources and energy storage units enables improving the sustainability, reliability, and robustness of power systems. To reach the objective of zero emissions, a proton exchange membrane hydrogen fuel-cell was utilized as an energy source. The aim of this research was to create an accurate optimal sizing procedure for determining the nominal rating of the necessary sources. We modeled the fuel cell and the battery pack using data from real experimental results to create the generic database. Then, we added data on the mission profile, system constraints, and the minimization target function. The mission profile was then analyzed by the sizing algorithm to determine optional minimum and maximum fuel cell ratings. Analyzing the optional solutions using the vehicle real time energy management system controller resulted in a set of solutions for each available rated fuel cell, and the o... [more]

The dynamic yaw motion of the wind turbine will affect the overall aerodynamic performance of the impeller and the corresponding wake flow, but the current research on this issue is inadequate. Thus, it is very necessary to study the complicated near-wake aerodynamic behaviors during the yaw process and the closely related blade aerodynamic characteristics. This work utilized the multi-relaxation time lattice Boltzmann (MRT-LBM) model to investigate the integral aerodynamic performance characteristics of the specified impeller and the dynamic changes in the near wake under a sine yawing process, in which the normalized result is adopted to facilitate data comparison and understanding. Moreover, considering the complexity of the wake flows, the large eddy simulation (LES) and wall-adapting local eddy-viscosity (WALE) model are also used in this investigation. The related results indicate that the degree of stability of tip spiral wake in the dynamic yaw condition is inversely related to... [more]

Surge tanks (STs) are important facilities for ensuring the safety of hydropower stations. Reducing the ST size under the premise of ensuring stable mass oscillations within the ST is the main issue. First, according to the basic equations of the mass oscillation for a hydropower station with an ST, a novel expression of the critical stability section of an ST is deduced considering the velocity head and throttle loss. Then, the sensitivity of each influencing factor of the proposed stability criterion is analyzed. Ultimately, through the simulation of small oscillation transients in two case studies, the water level oscillations (WLOs) in an ST based on three stability criteria are compared. The results show that a 20% smaller ST in a hydropower station may result in 10.4% larger oscillations and a 60% smaller ST in a pumped storage power station may result in 14.3% larger oscillations. Compared with the Thoma criterion and the Chinese specification criterion, the stability criterion... [more]

With the growing interest in geothermal energy as a renewable and sustainable energy source, nowadays engineers and researchers are facing technological and environmental challenges during geothermal wells’ operation or energy recovery improvement by optimizing surface installations. One of the major problems encountered is the degassing of geothermal brines which are often loaded with dissolved gases, resulting in technical problems (scale formation, corrosion, reduced process efficiency, etc.) and environmental problems through the possible emission of greenhouse gases (CO2, CH4 and water vapor) into the atmosphere. In this work, a method to predict, from readily available information such as temperature and GLR, the bubble point pressure of geothermal fluids as well as the GHG emission rate depending on the surface conditions is presented. This method is based on an extended version of the Soreide and Whitson model with new parameters optimized on the solubility data of several gase... [more]

This paper examines the performance of conical sections (concentrator and diffuser) to improve the energy-recovery prospects of small-scale wind turbines. Detailed simulation studies of the conical sections with convergence angle viz., concentrator, and divergence angle viz., diffuser were conducted using ANSYS Fluent® software. Using simulation data, a trend analysis was conducted, and the empirical equations were derived for calculating the velocity variation and power variation in terms of the convergence/divergence angles. Working prototype models with optimum angles were fabricated for both the diffuser and concentrator. These models were then augmented with a wind turbine coupled with a 100 W, 24 V DC generator and tested to validate the simulation results. Upon analyzing the simulation data, it was found that a maximum velocity variation of 23.3% was achieved at an angle of 4.5° for the diffuser, whereas a maximum power variation of 65.1% was achieved at an angle of 3.6° for the... [more]

The full utilization of broadband solar irradiance is becoming increasingly useful for applications such as long-term space missions, wherein power generation from external sources and regenerative life support systems are essential. Luminescent solar concentrators (LSCs) can be designed to separate sunlight into photosynthetically active radiation (PAR) and non-PAR to simultaneously provide for algae cultivation and electric power generation. However, the efficiency of LSCs suffers from high emission losses. In this work, we show that by shaping the LSC in the form of an elliptic array, rather than the conventional planar configuration, emission losses can be drastically reduced to the point that they are almost eliminated. Numerical results, considering the combined effects of emission, transmission and surface scattering losses show the optical efficiency of the elliptic array LSC is 63%, whereas, in comparison, the optical efficiency for conventional planar LSCs is 47.2%. Further,... [more]

This paper presents results of a study that focuses on developing a genetic algorithm (GA) for multi-criteria optimization of orthotropic, energy-efficient cementitious composite sandwich panels (CSP). The current design concept of all commercially produced CSP systems is based on the assumption that such panels are treated as doubly reinforced sections without the consideration of the three-dimensional truss contribution of the orthotropic panel system. This leads to uneconomical design and underestimating both the strength and stiffness of such system. In this study, two of the most common types of commercially produced sandwich were evaluated both numerically and experimentally and results were used as basis for developing a genetic algorithm optimization process using numerical modeling simulations. In order to develop a sandwich panel with high structural performance, design optimization techniques are needed to achieve higher composite action, while maintaining the favorable feat... [more]

The flyback converters are widely used in low power applications. The switch typically requires 600 V breakdown voltage in order to perform large step-down voltage. Thus, slight variation on the switch control can either permanently damage the switch or decrease the efficiency of the power conversion. In order to achieve higher power efficiency, the previous literature suggested operating the flyback converter in the discontinuous current mode (DCM). It is then required to understand the critical conditions of the DCM through analyzing the dynamic behavior and discontinuous current mechanism. This paper started from the current waveform analyses, proceeded to the derivation of zero current switching (ZCS) formulation, and finally reached the necessary conditions for the DCM. The entire DCM operation was divided into three phases that subsequently affect the result of the zero voltage switching (ZVS) and then to the ZCS. The experiment shows a power efficiency of over 96% when the outpu... [more]

This paper investigates the problem of stability in a group of headings driven in high horizontal stress fields in the copper ore mines of the Legnica-Glogow Copper Belt (LGCB). The headings are protected with the roof bolting system. This problem is of high importance due to special safety regulations which apply in mining workings serving as airways and haulageways. The analysis was performed for a group of four headings driven in the geological and mining conditions of the Polkowice-Sieroszowice mine. The stability of the headings was evaluated with the use of Finite Element Method (FEM). The parameters of the rocks used in the numerical modeling have been determined on the basis of the Hoek−Brown classification, with the use of the RocLab 1.0 software. The parameters of the stress field have been identified on the basis of in situ measurements, which were performed in the Polkowice-Sieroszowice mine in 2012. The measurements were carried out with the use of the overcoring method, w... [more]

The aim of the article is to numerically model a two-dimensional multiphase flow based on the volume of fluid method (VOF) in a pulsating heat pipe (PHP). The current state of knowledge regarding the modeling of these devices was studied and summarised. The proposed model is developed within open source software, OpenFOAM, based on the predefined solver called interPhaseChangeFoam. The analyses were carried out in terms of the influence of four different mass transfer models between the phases, proposed by Tanasawa, Lee, Kafeel and Turan, and Xu et al. on the shape and dynamics of the internal flow structures. The numerical models were validated against data obtained from a specially designed experimental setup, consisting of three bends of pulsating heat pipes. The numerical calculations were carried out with ethanol being treated as a working medium and the initial and boundary conditions taken directly from the measurement procedures. The variable input parameter for the model was t... [more]

State-of-the-art Predictive Maintenance (PM) of Electrical Machines (EMs) focuses on employing Artificial Intelligence (AI) methods with well-established measurement and processing techniques while exploring new combinations, to further establish itself a profitable venture in industry. The latest trend in industrial manufacturing and monitoring is the Digital Twin (DT) which is just now being defined and explored, showing promising results in facilitating the realization of the Industry 4.0 concept. While PM efforts closely resemble suggested DT methodologies and would greatly benefit from improved data handling and availability, a lack of combination regarding the two concepts is detected in literature. In addition, the next-generation-Digital-Twin (nexDT) definition is yet ambiguous. Existing DT reviews discuss broader definitions and include citations often irrelevant to PM. This work aims to redefine the nexDT concept by reviewing latest descriptions in broader literature while es... [more]

We demonstrate a working functional prototype of a cooperative perception system that maintains a real-time digital twin of the traffic environment, providing a more accurate and more reliable model than any of the participant subsystems—in this case, smart vehicles and infrastructure stations—would manage individually. The importance of such technology is that it can facilitate a spectrum of new derivative services, including cloud-assisted and cloud-controlled ADAS functions, dynamic map generation with analytics for traffic control and road infrastructure monitoring, a digital framework for operating vehicle testing grounds, logistics facilities, etc. In this paper, we constrain our discussion on the viability of the core concept and implement a system that provides a single service: the live visualization of our digital twin in a 3D simulation, which instantly and reliably matches the state of the real-world environment and showcases the advantages of real-time fusion of sensory da... [more]

Knowledge of the drying properties of tobacco in high temperatures above 100 °C and its dust are crucial in the design of dryers, both in the optimization of the superheated-steam-drying process and in the correct selection of innovative explosion protection and mitigation systems. In this study, tobacco properties were determined and incorporated into the proposed model of an expanding superheated steam flash dryer. The results obtained from the proposed model were validated by using experimental data yielded during test runs of an industrial scale of a closed-loop expansion dryer on lamina cut tobacco. Moreover, the explosion and fire properties of tobacco dust before and after the superheated steam-drying process at 160, 170, 180, and 190 °C were experimentally investigated, using a 20 L spherical explosion chamber, a hot plate apparatus, a Hartmann tube apparatus, and a Godbert−Greenwald furnace apparatus. The results indicate that the higher the drying temperature, the more likely... [more]

Energy modelling is key in order to face the challenges of energy transition. There is a wide variety of modelling tools, depending on their purpose or study phase. This article summarises their main characteristics and highlights ones that are relevant when it comes to the preliminary design of energy studies at district scale. It introduces OMEGAlpes, a multi-carrier energy modelling tool to support stakeholders in the preliminary design of district-scale energy systems. OMEGAlpes is a Mixed-Integer Linear Programming (MILP) model generation tool for optimisation. It aims at making energy models accessible and understandable through its open-source development and the integration of energy stakeholders and their areas of responsibility into the models. A library of use cases developed with OMEGAlpes is presented and enables the presentation of past, current, and future development with the tool, opening the way for future developments and collaborations.

Modeling the fuel injection process in modern gasoline direct injection engines plays a principal role in characterizing the in−cylinder mixture formation and subsequent combustion process. Flash boiling, which usually occurs when the fuel is injected into an ambient pressure below the saturation pressure of the liquid, is characterized by fast breakup and evaporation rates but could lead to undesired behaviors such as spray collapse, which significantly effects the mixture preparation. Four mono−component fuels have been used in this study with the aim of achieving various flashing behaviors utilizing the Spray G injector from the Engine Combustion Network (ECN). The numerical framework was based on a Lagrangian approach and was first validated for the baseline G1 condition. The model was compared with experimental vapor and liquid penetrations, axial gas velocity, droplet sizes and spray morphology and was then extended to the flash boiling condition for iso−octane, n−heptane, n−hexa... [more]

Virtual simulations and calculations are a key technology for future development methods. A variety of tools and methods for calculating thermal comfort have not gained sufficient acceptance in practice due to their inherent complexity. This article investigates alternative means of determining thermal comfort, namely, the linearization of the equivalent temperature calculation. This enables a wide range of users to evaluate thermal comfort in a fast and easy manner, for example, for energy efficiency simulation. A flow and thermal model were created according to the requirements of DIN EN ISO 14505 to determine heat transfer coefficients under calibration conditions. The model to simulate the equivalent temperature in calibration conditions comprises a geometrically realistic 3D model of a human test person according to the standard. The influence of the turbulence model, as well as the influence of the equivalent temperature on the heat transfer coefficient in calibration conditions,... [more]

A gas condensate reservoir in Northern Croatia was used as an example of a CO2 injection site during natural gas production to test whether the entire process is carbon-negative. To confirm this hypothesis, all three elements of the CO2 life cycle were included: (1) CO2 emitted by combustion of the produced gas from the start of production from the respective field, (2) CO2 that is separated at natural gas processing plant, i.e., the CO2 that was present in the original reservoir gas composition, and (3) the injected CO2 volumes. The selected reservoir is typical of gas-condensate reservoirs in Northern Croatia (and more generally in Drava Basin), as it contains about 50% CO2 (mole). Reservoir simulations of history-matched model showed base case (production without injection) and several cases of CO2 enhanced gas recovery, but with a focus on CO2 storage rather than maximizing hydrocarbon gas production achieved by converting a production well to a CO2 injection well. General findings... [more]

The contemporary striving for increased speed in rail transport, with simultaneous requirements in terms of travel comfort, makes the safety of rail vehicles one of the priorities in the process of passenger rail transport. It is obvious that safety in this case is determined by: the technical condition of the vehicle, the condition of the railway infrastructure and the conditions of cooperation between the railway vehicle and the track. Railway vehicles running safety tests can be carried out on-line, in real operating conditions, and off-line with the use of mathematical models and simulation methods. The on-line research does not assess the impact of the parameter characterizing the track geometry, i.e., rail inclination, on the driving safety, and the deviation of the shape of wheel and rail running surfaces from the nominal dimensions is rarely diagnosed and taken into account in the tests. The considerations in this article are devoted to the discussion of the effects on the safe... [more]

This paper presents a probabilistic framework for updating the structural reliability of offshore wind turbine substructures based on digital twin information. In particular, the information obtained from digital twins is used to quantify and update the uncertainties associated with the structural dynamics and load modeling parameters in fatigue damage accumulation. The updated uncertainties are included in a probabilistic model for fatigue damage accumulation used to update the structural reliability. The updated reliability can be used as input to optimize decision models for operation and maintenance of existing structures and design of new structures. The framework is exemplified based on two numerical case studies with a representative offshore wind turbine and information acquired from previously established digital twins. In this context, the effect of updating soil stiffness and wave loading, which constitute two highly uncertain and sensitive parameters, is investigated. It is... [more]

In this work, based on the concept of collaborative water−energy development, a multi-scenario system dynamics simulation model of a water−energy coupling system was constructed by using the system dynamics modeling method. The model was composed of four subsystems: society, economic, water resources, and energy. Taking Ningbo City as the research location to run the simulation model, the analysis of the validity of the model showed that the relative error between the historical data and the simulation results of the model was less than 10%, which proved that the model passed the test. In this paper, based on the scenario of business an usual (BAU), three scenarios of water-saving scenario (WSS), energy-saving scenario (ESS), and comprehensive savings (CS, the comprehensive scenario considers water-saving and energy-saving together) were designed, and the simulation indexes in the three scenarios were refined in order to strengthen the control of water-saving policies, improve the effe... [more]

A feature of energy systems (ESs) is the diversity of objects, as well as the variety and manifold of the interconnections between them. A method for monitoring ESs clusters is proposed based on the combined use of a fuzzy cognitive approach and dynamic clustering. A fuzzy cognitive approach allows one to represent the interdependencies between ESs objects in the form of fuzzy impact relations, the analysis results of which are used to substantiate indicators for fuzzy clustering of ESs objects and to analyze the stability of clusters and ESs. Dynamic clustering methods are used to monitor the cluster structure of ESs, namely, to assess the drift of cluster centers, to determine the disappearance or emergence of new clusters, and to unite or separate clusters of ESs.

The subject of this work is the mathematical modelling of a counter-current moving-bed gasifier fuelled by wood-pellets. Two versions of the model have been developed: the one-dimensional (1D) version-solving a set of Ordinary Differential Equations along the gasifier height-and the three-dimensional (3D) version where the balanced equations are solved using Computational Fluid Dynamics. Unique procedures have been developed to provide unconditionally stable solutions and remove difficulties occurring by using conventional numerical methods for modelling counter-current reactors.The procedures reduce the uncertainties introduced by other mathematical approaches, and they open up the possibility of straightforward application to more complex software, including commercial CFD packages. Previous models of Hobbs et al., Di Blasi and Mandl et al. used a correction factor to tune calculated temperatures to measured values. In this work, the factor is not required. Using the 1D model, the Ma... [more]

Capacitive energy extraction based on double layer expansion (CDLE) is a renewable method of harvesting energy from the salinity difference between seawater and freshwater. It is based on the change in properties of the electric double layer (EDL) formed at the electrode surface when the concentration of the solution is changed. Many theoretical models have been developed to describe the structural and thermodynamic properties of the EDL at equilibrium, e.g., the Gouy−Chapman−Stern (GCS), Modified Poisson−Boltzmann−Stern (MPBS), modified Donnan (mD) and improved modified Donnan (i-mD) models. To evaluate the applicability of these models, especially the rationality and the physical interpretation of the parameters that were used in these models, a series of single-pass and full-cycle experiments were performed. The experimental results were compared with the numerical simulations of different EDL models. The analysis suggested that, with optimized parameters, all the EDL models we exam... [more]

The work described in this paper aims to detect and eliminate cyber-attacks in smart grids that disrupt the process of dynamic state estimation. This work makes use of an unsupervised learning method, called hierarchical clustering, in an attempt to create an artificial sensor to detect two different cyber-sabotage cases, known as false data injection and denial-of-service, during the dynamic behavior of the power system. The detection process is conducted by using an unsupervised learning-enhanced approach, and a decision tree regressor is then employed for removing the threat. The dynamic state estimation of the power system is done by Kalman filters, which provide benefits in terms of the speed and accuracy of the process. Measurement devices in utilities and buses are vulnerable to communication interruptions between phasor measurement units and operators, who can be easily manipulated by false data. While Kalman filters are incapable of detecting the majority of such cyber-attacks... [more]

In the last decade, China has sharply tightened the monitoring values for wastewater treatment plants (WWTPs). In some regions with sensitive discharge water bodies, the values (24 h composite sample) must be 1.5 mg/L for NH4-N and 10 mg/L for total nitrogen since 2021. Even with the previously less strict monitoring values, around 50% of the wastewater treatment plants in China were permanently unable to comply with the nitrogen monitoring values. Due to the rapid changes on-site to meet the threshold values and the strong relation to energy-intensive aeration strategies to sufficiently remove nitrogen, WWTPs do not always work energy-efficiently. A Chinese WWTP (450,000 Population equivalents or PE) with upstream denitrification, a tertiary treatment stage for phosphorus removal and disinfection, and aerobic sludge stabilisation was modelled in order to test various concepts for operation optimisation to lower energy consumption while meeting and undercutting effluent requirements. F... [more]