Oil pipeline construction and operation in mountainous areas have increased in southwestern China, with oil consumption increasing. Such liquid pipelines laid in mountainous areas continuously undulate along the terrain, resulting in many large elevation difference pipe segments. Serious gas block problems often occur during the commissioning process of these pipelines due to the gas/air accumulation at the high point of the pipe, which causes pipeline overpressure and vibration, and even safety accidents such as bursting pipes. To solve this problem, the gas−liquid replacement model and its numerical solution are established with consideration of the initial gas accumulation formation and the gas segment compression processes in a U-shaped pipe during the initial start-up operation. Additionally, considering the interactions of the gas-phase transfer in the continuous U-shaped pipe, and the influence of the length, inclination angle, and backpressure on the air vent process, the gas m... [more]

The demand for heating in cold regions drives up carbon emissions every year. In order to achieve China’s carbon neutrality target by 2060, CO2 emissions in the cold regions must be reduced. In this paper, using Design Builder software, a simulation model of residential buildings in severe cold regions was created, and the most appropriate parameter design scheme for carbon emission reduction of residential buildings in severe cold regions was derived by simulating the experimental data of the original parameter design scheme and the changed parameter design scheme, as well as the calculation of carbon dioxide emission reduction rate. In order to make the comparison of the results easier, no change was made in the selection of the changed scheme for the external insulation material, foamed polystyrene panels. The results show that the most suitable parameter scheme for houses in severe cold regions is 85 mm thick foamed polystyrene panels for exterior walls, 200 mm thick foamed polysty... [more]

As electric vehicles have become increasingly popular in recent years, battery swapping technology has been promoted as an alternative to the time-consuming battery charging process. Nevertheless, battery swapping is held back by the trade-off between the additional battery investment and the short service time for users. In this paper, we developed simulation models to analyze the economics of battery swapping systems. In particular, we collected real data from eight battery swapping stations Guangzhou, China for the analysis. The results show that the service levels of the stations are reduced significantly as the number of users increases. On the other hand, economies of scale exists when implementing the battery swapping system. As the number of users increases, to maintain the same level of service level, the cost of the batteries shared by each user decreases. The analysis also suggests that, given the scale of potential users for an area, the marginal utility of increasing the n... [more]

This paper aims to determine cost optimality between heating, ventilation and air conditioning (HVAC) systems operating with air to water heat pumps (AWHP) and water to water heat pumps (WWHP). The analysis is performed for a certain number of heat pump units with fixed and variable capacity made by four manufacturers available on European market. Simulations are performed in Trnsys software. The results show that heat pump partial load efficiency should not be neglected in analysis of application while the difference in energy consumption and costs can be up to 17%. The requirement for performing analysis on a wider range of units is indicated, especially when heat pump systems with different sources are considered. HVAC system with AWHP units with capacity control is a cost optimal solution for case study nursery building operating on the Croatian coast. The application of the photovoltaic (PV) array sized to cover nonrenewable part of electricity consumed in HVAC system has a return... [more]

The pollution caused by gas flaring is hazardous to the health of flora, fauna, and humans settled around the flaring site. Gas flaring also incurs economic loss as natural gas, an energy source, is wasted in flares. Furthermore, the unreliable electrical infrastructure is a roadblock for oil and gas companies attempting to achieve their production targets. This paper presents a framework to design hybrid energy systems (HES) which utilize the gas flare waste along with the locally available renewable energy sources to generate electricity. A novel dispatch strategy to suit the requirements of the oil and gas fields has been used for real-time simulations and optimization of the HES. As a test case, six different hybrid energy configurations, modelled for two gas flaring sites, Lakwa and Geleky in Assam—India, were analyzed and compared on the basis of economic and environmental factors. The best suitable configuration comprised 2000 kW solar photovoltaic (PV) panel sets, one 200 kW ga... [more]

The aim of this paper is to analyze the heat distribution in the high-current electrical contact under the action of an assumed current of 3000 A using mathematical modeling and simulation. Electrical contacts that carry high currents are an essential component of many electric devices. In transmission and distribution systems, the electrical contacts are of particular importance because they must withstand adverse weather conditions that decrease their effectiveness. Therefore, it is essential to detect any rise in temperature of the electrical contact to ensure efficient and reliable energy transmission. For this paper, simulations of the temperature field in direct electrical contact were carried out in ANSYS and discussed. During the simulation, a high-current electric contact was exposed to 3000 A current and the change of the adverse effects of contaminated contact layers affected temperature field. According to the results, electric contact in good condition (represented by impu... [more]

Nitrogen−oxygen sensors are pivotal for NOX emission detection, and they have been designed as key components in vehicles’ exhaust systems. However, severe thermal stress concentrations during thermal cycling in the sensors create knotty structural damage issues, which are inevitable during the frequent start−stop events of the vehicles. Herein, to illustrate the effect of thermal concentration on a sensor’s structure, we simulated the temperature and stress field of a sensor through finite element analysis. The failure modes of the sensor based on the multilayer structure model were analyzed. Our simulation indicated that the thermal deformation and stress of the sensors increased significantly when the heating temperature in the sensors increased from 200 to 800 °C. High stress regions were located at the joint between the layers and the right angle of the air chamber. These results are consistent with the sensor failure locations that were observed by SEM, and the sensor’s failures... [more]

Ultra-high-frequency (UHF) partial discharge (PD) monitoring is gaining popularity because of its advantages over electrical methods for onsite/online applications. One such advantage is the possibility of three-dimensional PD source localization. However, it is necessary to understand the signal propagation and attenuation characteristics in transformers to improve localization. Since transformers are available in a wide range of ratings and geometric sizes, it is necessary to ascertain the similarities and differences in UHF signal characteristics across the different designs. Therefore, in this contribution, the signal attenuation and propagation characteristics of two 300 MVA transformers are analyzed and compared based on experiments. The two transformers have the same rating but different internal structures. It should be noted that the oil is drained out of the transformers for these tests. Additionally, a simulation model of one of the transformers is built and validated based... [more]

The pyrolysis characteristics of oil shale during heat treatment dominate the oil production of kerogen. In this study, the pyrolysis characteristics of oil shale in a laboratory microwave apparatus were investigated based on a novel fully coupled three-dimensional electromagnetic-thermal-chemical-hydraulic model according to the experimental microwave apparatus. By simulating the electric field, temperature distribution, and kerogen decomposition within oil shale subjected to microwave irradiation, several parameters, including waveguide, position, and power, were successfully optimized. The results indicated that the non-uniform temperature distribution was consistent with the distribution of the electric field. Double microwave ports were more effective than single ports in terms of heating rate and temperature uniformity. There was an optimal location where the highest heating efficiency was obtained, which was on the left of the cavity center. When irradiation was conducted over a... [more]

Tailpipe emissions from vehicles consist of CO2 and other greenhouse gases, which contribute immensely to the rise in global temperatures. Green hydrogen produced from the gasification of biomass can reduce the amount of CO2 emissions to zero. This study aims to provide a modelling framework to optimize the production of hydrogen from biomass waste obtained from different cities, for use in the road transport sector in Nigeria. A gasification model with post-treatment shift conversion and CO2 removal by adsorption is proposed. In this study, six cities are simulated based on technical and environmental considerations, using the Aspen Plus software package. The results revealed that Kaduna has the highest hydrogen generation potential of 0.148 million metric tons per year, which could reduce CO2 emissions to 1.60 and 1.524 million metric tons by the displacement of an equivalent volume of gasoline and diesel. This amounts to cost savings of NGN 116 and 161.8 billion for gasoline and die... [more]

Loaders are widely used in the construction of earthworks for construction projects. Due to the large volume and mass of these machines, they have shortcomings such as low driving efficiency and high energy consumption. To address these shortcomings, this work applied eclectic drive technology to a loader’s traction system. A wheel electric drive system with a switched reluctance driver (SRD) was developed. The operating principle and basic structure of the SRD system were analyzed. A new voltage PWM-controlled strategy with dynamic adjustable turn-on and turn-off angles and a single conducting phase in a fixed period was developed. Then, an SRD simulation model was established in MATLAB/Simulink. A simulation of the working condition for the loader was performed. A test bench for the SRD was built and accordingly the transportation and operation conditions were tested. The corresponding speed−time curve of transportation and operation was obtained. Simulation and experiment results sh... [more]

This paper presents a comparative simulation study of the operation of various types of drivers dedicated for use in light-emitting diode (LED)-based light stripes. The study comprises an experimentally verified simulation in view of their influence on harmonic content generation and impact on electric energy quality. The simulation models were optimized in order to precisely reflect the currents and voltage waveforms recorded in the frame of laboratory measurements. The simulation parameters were adjusted in view of harmonic generation analysis and high-frequency (HF) transient presence resulting from circuit principles of operation. Two driver circuit types were analyzed in the framework of the study—a voltage stabilization circuit based on a Zener diode, and a current stabilization integrated circuit (IC) based on an AL8806 chip. The study results entail an analysis executed for light stripes comprising various numbers of LEDs connected to each driver and various numbers of each of... [more]

Recent research has focused on shorter pulses, new spectral ranges, higher photon fluxes, and the production of photons with a variety of polarizations. A time-dependent three-dimensional free-electron laser oscillator code was developed for a two-beam free-electron laser system with an elliptically polarized undulator. Characteristics of the interaction of the electron beams and polarized radiation in the XUV region were studied using this code. The code utilized an optical field using the spectral method in the paraxial approximation by a fast Fourier transformation, a Gaussian modal expansion for the optical field, and Newton−Lorentz force equations for particle tracking. As the emittance was increased, the degrees of polarization of the single-beam system with an elliptically polarized undulator and the two-beam system with a planar undulator were decreased significantly compared to those of a two-beam system with an elliptically polarized undulator in the XUV regions. The radiatio... [more]

The safety case for a radioactive waste repository relies heavily on results obtained by numerical models that assess the long-term performance of the engineered and natural barrier systems. Given that important engineering and public policy decisions are based on these models, it is essential that we critically evaluate their abilities and limitations, and thus justify the level of confidence we have in the inferences drawn from the modeling. In this article, we discuss some of the issues surrounding the modeler’s attempts to test, corroborate, confirm, and verify numerical models—a process sometimes referred to as model validation. This wide-ranging topic is approached by first examining its deep roots in the philosophy of science and hypothesis testing. However, the application of these principles to radioactive waste isolation calls for a more pragmatic approach, which has the narrower goal of corroborating site-specific models and their usefulness for a specific purpose. We focus... [more]

A heat pump for simultaneous heating and cooling (HPS) is a refrigeration machine by which the productions of heating and cooling energies are simultaneously valorized. This introductory article presents the uses of heat pump productions under the form of an analysis of thermal demands of different types of buildings and a literature review of real installations and experimental systems, which are the basis of the construction of numerical models. The applications of HPSs are diverse: space heating and cooling, domestic hot water (DHW), hot water for desalination process, etc. Means and methods for improving the performance of refrigeration cycles and the management of heat and cold productions are developed, including modeling and simulation. New refrigeration circuit architectures were designed. A focus is paid on refrigerants. Prototypes combining heating-cooling, heating-cooling-DHW and cooling-desalination have been developed, built and tested to validate the models. Even though a... [more]

Microwave treatment is an emerging technique for biomass tar elimination. The electric and thermal fields of the microwave reactor are the key to high elimination efficiency and energy utilization. In this work, we simulated the electric and thermal fields of a microwave reactor with various parameters including irradiation feed position, microwave power, silicon carbide length and flow velocity. Results show that the irradiation feed position that locates 5 mm vertically to the central plane can obtain the highest electric intensity and silicon carbide temperature (ca. 1100 K) after wave absorbing. Both the electric and thermal fields are strengthened when microwave power is increased. Extending the silicon carbide bed length will decrease the bed temperature and heating rate. A high flow velocity leads to non-uniform temperature distribution of the silicon carbide. For the purpose of achieving a high microwave energy utilization and uniform bed temperature, suitable irradiation feed... [more]

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

This paper presents the case study of provisions of frequency containment reserve (FCR) with a battery electric storage system (BESS). The aim of the case study is the evaluation of the technical possibility to provide FCR in Latvian power systems after all Baltic power systems will synchronize with the Continental Europe Synchronous Area (CESA). To simulate the dynamics of BESS capacity and its state of charge (SOC), authors have developed an algorithm and mathematical model (it can be realized in different calculation programs). The case study calculations verified the model. The algorithm is conditionally divided into two parts—FCR provision and SOC recovery−which in turn is divided into three possible models of BESS state of charge recovery options: (1) overfulfillment—exceeding the specified FCR amount, (2) deadband utilization, and (3) BESS charging or discharging through scheduled transactions in intraday power market. The modelling was performed using historic frequency data of... [more]

This paper proposes the full simulation model for the electrical analysis of all-electric ship (AES) based on a medium voltage DC power system. The AES has become popular both in the commercial and the military areas due to a low emission, a high fuel consumption efficiency, and a wide applicability. In spite of many advantages, it is complex and difficult to construct the whole system with many mechanical and electrical components onboard. Full electrical analysis is essentially required to simplify the design of the AES, a control and optimization of a ship electric system. The proposed full simulation model of the AES includes the mechanical and the electrical elements by using the MATLAB/Simulink. The mechanical elements are comprised of a steam turbine and a hydrodynamic model of a ship which is adopted by an average value model that is based on the characteristic equation of the mechanical system. The electrical elements are developed by full detailed models which consist of gene... [more]

The conversion of biomass to olefin by employing gasification has recently gained the attention of the petrochemical sector, and syngas composition is a keystone during the evaluation of process design. Process simulation software is a preferred evaluation tool that employs stoichiometric and kinetic approaches. Despite the available literature, the estimation errors of these simulation methods have scarcely been contrasted. This study compares the errors of stoichiometric and kinetic models by simulating a downdraft steam gasifier in PRO/II. The quantitative examination identifies the model that best predicts the composition of products for the gasification of Japanese wood waste. The simulation adopts reaction mechanisms, flowsheet topology, reactions parameters, and component properties reported in the literature. The results of previous studies are used to validate the models in a comparison of the syngas composition and yield of products. The models are used to reproduce gasificat... [more]

Finding a suitable location is a key factor for long-term investment in wind turbine energy. It includes understanding the area of interest, such as the subsidence of the land. Land subsidence is a gradual decrease in the surface of the Earth due to natural and/or induced causes. It can cause damage, such as settlement problems in the ground near infrastructure including buildings and wind turbines, thus not being a suitable place for long-term investment. Here, we show a case study of land subsidence prediction and assessment of the Atsimo Andrefana region, the great south-western part of Madagascar, using theoretical simulation and satellite images from the Sentinel-1 mission using D-InSAR method. The predicted land subsidence related to the depletion of groundwater reservoirs in the Atsimo Andrefana region is around 12 mm. We found ~5 mm of subsidence related to the growing city of Toliary and with an average subsidence of 124 mm and the highest record of 167 mm in the most southern... [more]

Bag-of-Tasks (BoT) scheduling over cloud computing resources called Cloud Bag-of-Tasks Scheduling (CBS) problem, which is a well-known NP-hard optimization problem. Whale Optimization Algorithm (WOA) is an effective method for CBS problems, which still requires further improvement in exploration ability, solution diversity, convergence speed, and ensuring adequate exploration−exploitation tradeoff to produce superior scheduling solutions. In order to remove WOA limitations, a hybrid oppositional differential evolution-enabled WOA (called h-DEWOA) approach is introduced to tackle CBS problems to minimize workload makespan and energy consumption. The proposed h-DEWOA incorporates chaotic maps, opposition-based learning (OBL), differential evolution (DE), and a fitness-based balancing mechanism into the standard WOA method, resulting in enhanced exploration, faster convergence, and adequate exploration−exploitation tradeoff throughout the algorithm execution. Besides this, an efficient al... [more]

When it comes to covering the growing demand for cooling power worldwide, elastocalorics offer an environmentally friendly alternative to compressor-based cooling technology. The absence of harmful and flammable coolants makes elastocalorics suitable for energy applications such as battery cooling. Initial prototypes of elastocaloric systems, which transport heat by means of thermal conduction or convection, have already been developed. A particularly promising solution is the active elastocaloric heat pipe (AEH), which works with latent heat transfer by the evaporation and condensation of a fluid. This enables a fast and efficient heat transfer in a compression-based elastocaloric cooling system. In this publication, we present a simulation model of the AEH based on MATLAB-Simulink. The model showed very good agreement with the experimental data pertaining to the maximum temperature span and maximum cooling power. Hereby, non-measurable variables such as efficiency and heat fluxes in... [more]

Classification machine learning models require high-quality labeled datasets for training. Among the most useful datasets for photovoltaic array fault detection and diagnosis are module or string current-voltage (IV) curves. Unfortunately, such datasets are rarely collected due to the cost of high fidelity monitoring, and the data that is available is generally not ideal, often consisting of unbalanced classes, noisy data due to environmental conditions, and few samples. In this paper, we propose an alternate approach that utilizes physics-based simulations of string-level IV curves as a fully synthetic training corpus that is independent of the test dataset. In our example, the training corpus consists of baseline (no fault), partial soiling, and cell crack system modes. The training corpus is used to train a 1D convolutional neural network (CNN) for failure classification. The approach is validated by comparing the model’s ability to classify failures detected on a real, measured IV... [more]

The accurate prediction of the falling film characteristics of cryogenic liquids is necessary to ensure good evaporation performance, due to their special physical properties. In this study, the film flow and heat transfer characteristics on four different structures were investigated, and the performance of the cryogenic liquid oxygen was compared with other fluids with higher temperatures, which demonstrates the influence of structures and liquid mediums. The VOF model was used to capture the film surface in the simulation model. The results show that for the four structures, liquids with higher kinematic viscosity tend to have greater film thickness, and the sensible heat transfer coefficients are inversely related to the nominal thermal resistance of falling film flow. Both on the smooth plate and the corrugated plate, the film wettability depends on the kinematic viscosity, rather than the dynamic viscosity, and the effect of kinematic viscosity is greater than that of surface ten... [more]