The axial-flux permanent magnet (AFPM) machines with yokeless and segmented armature (YASA) topology are suitable for in-wheel traction systems due to the high power density and efficiency. To guarantee the reliable operation of the YASA machines, an accurate thermal analysis should be undertaken in detail during the electrical machine design phase. The technical contribution of this paper is to establish a detailed thermal analysis model of the YASA machine by the lumped parameter thermal network (LPTN) method. Compared with the computational fluid dynamics (CFD) method and the finite element (FE) method, the LPTN method can obtain an accurate temperature distribution with low time consumption. Firstly, the LPTN model of each component of the YASA machine is constructed with technical details. Secondly, the losses of the YASA machine are obtained by the electromagnetic FE analysis. Then, the temperature distribution of the machine can be calculated by the LPTN model and loss informati... [more]

A proton exchange membrane fuel cell (PEMFC) system requires an adequate hydrogen supply and circulation to achieve its expected performance and operating life. An ejector-based hydrogen circulation system can reduce the operating and maintenance costs, noise, and parasitic power consumption by eliminating the recirculation pump. However, the ejector’s hydrogen entrainment capability, restricted by its geometric parameters and flow control variability, can only operate properly within a relatively narrow range of fuel cell output power. This research introduced the optimal design and operation control methods of a dual-ejector hydrogen supply/circulation system to support the full range of PEMFC system operations. The technique was demonstrated on a 70 kW PEMFC stack with an effective hydrogen entrainment ratio covering 8% to 100% of its output power. The optimal geometry design ensured each ejector covered a specific output power range with maximized entrainment capability. Furthermor... [more]

High precision short-term photovoltaic (PV) power prediction can reduce the damage associated with large-scale photovoltaic grid-connection to the power system. In this paper, a combination deep learning forecasting method based on variational mode decomposition (VMD), a fast correlation-based filter (FCBF) and bidirectional long short-term memory (BiLSTM) network is developed to minimize PV power forecasting error. In this model, VMD is used to extract the trend feature of PV power, then FCBF is adopted to select the optimal input-set to reduce the forecasting error caused by the redundant feature. Finally, the input-set is put into the BiLSTM network for training and testing. The performance of this model is tested by a case study using the public data-set provided by a PV station in Australia. Comparisons with common short-term PV power forecasting models are also presented. The results show that under the processing of trend feature extraction and feature selection, the proposed me... [more]

The harvesting and hauling operations of bioenergy feedstock is an important area in biofuel production. Production costs can be minimized by maintaining optimal machinery units for these operations. The objective of this study is to design an optimal harvesting unit for bioenergy refinery and estimate harvesting and hauling costs of energy cane. A biorefinery with the annual capacity of processing twenty-five million imp. gallons of ethanol were considered. Given the efficiency of harvesting, a two-row soldier system was considered. Considering the year-round supply of energy cane to the refinery, the optimal machinery unit was designed, and the combined operation costs were derived. The average estimated ownership, repair, labor and fuel and lubricant costs of biomass harvest unit were calculated to be $0.50, $0.54, $1.78 and $1.51/mt, respectively. The costs distribution generated showed harvesting and hauling costs could range between $5.47−$9.23/mt of energy cane. The methodology... [more]

Thermal power plants, TPP, are one of the main players in the phosphoric acid and fertilizer production value chain. The control of power plant assets involves considerable complexity and is subject to several constraints, affecting the asset’s reliability and, most importantly, plant operators’ safety. The main focus of this paper is to investigate the potential of an agent-based digital twin architecture for collaborative prognostic of power plants. Based on the ISO 13374:2015 scheme for smart condition monitoring, the proposed architecture consists of a collaborative prognostics system governed by several smart DT agents connected to both physical and virtual environments. In order to apprehend the potential of the developed agent-based architecture, experiments on the architecture are conducted in a real industrial environment. We show throughout the paper that our proposed architecture is robust and reproduces TPP static and dynamic behavior and can contribute to the smart monitor... [more]

The karst landscape is widespread in the southern region of China. As a result of underground mining activities, the original stress equilibrium is disrupted, causing the redistribution of stress in the overlying rock layer, inducing the longitudinal fracture of mining to expand and penetrate upwards, resulting in the rupture and destabilization of the karst cave roof, thus triggering a series of engineering problems such as karst cave collapse, landslide, the discontinuous deformation of the ground surface, and soil erosion. In order to study the evolutionary characteristics of buried rock fissures in shallow coal seam mining under the karst landform, taking the shallow coal seam with the typical karst cave development landform in Guizhou as the engineering background, based on the similarity simulation experiment and fractal theory, the evolution law of buried rock fissures and network fractal characteristics under the disturbance of the karst landform mining are analyzed. The resear... [more]

The rotation speed of water at the inlet of the low hump outlet conduit has a great effect on its hydraulic performance. Therefore, the influence of different inlet water rotation speeds on hydraulic loss and flow pattern of low hump outlet conduit is studied in this paper. By solving RANS equations and the RNG k-ε turbulence model, the hydraulic loss and 3D flow field of the low hump outlet conduit were calculated under different inlet water rotation speeds. To verify the numerical results, the model tests of low hump outlet conduit with different guide vanes were conducted. The results show that along with the growth of inlet water rotation speed, the hydraulic loss of outlet conduit will firstly decrease by degrees and then increase dramatically, the vortex location moves from the whole bottom of the descent segment to the right bottom of descent segment and the vortex area becomes smaller, the flow pattern of the whole conduit is improved obviously. The hydraulic loss and flow fiel... [more]

In this study, we considered a bridging strategy between qualitative and quantitative research with the aim of achieving complementarity. A pilot case study using the Sheffield Elicitation Framework “SHELF” to estimate appropriate inputs for a quantitative energy systems model (based on a qualitative energy future scenario) was used to gain insights. Of novelty are the ethnographic insights of an example translation procedure as well as the methodological approach of the translation procedure itself. This paper reports the findings from this exercise concerning the practicalities of applying such a technique and the observations from the expert elicitation process itself. Based on this pilot, we make two recommendations. The first is the importance of devising a strategy in projects, and research programmes, where bridging between qualitative and quantitative research activities would be most effective. The second is that observations of discussions during the expert elicitation proces... [more]

Photovoltaic power generation has high variability and uncertainty because it is affected by uncertain factors such as weather conditions. Therefore, probabilistic forecasting is useful for optimal operation and risk hedging in power systems with large amounts of photovoltaic power generation. However, deterministic forecasting is the mainstay of photovoltaic generation forecasting; there are few studies on probabilistic forecasting and feature selection from weather or time-oriented features in such forecasting. In this study, prediction intervals were generated by the lower upper bound estimation (LUBE) using neural networks with two outputs to make probabilistic modeling for predictions. The objective was to improve prediction interval coverage probability (PICP), mean prediction interval width (MPIW), continuous ranked probability score (CRPS), and loss, which is the integration of PICP and MPIW, by removing unnecessary features through feature selection. When features with high ga... [more]

Quantitative characterisation through mineral liberation analysis is required for effective minerals processing in areas such as mineral deposits, tailings and reservoirs in industries for resources, environment and materials science. Current practices in mineral liberation analysis are based on 2D representations, leading to systematic errors in the extrapolation to 3D volumetric properties. The rapid development of X-ray microcomputed tomography (μCT) opens new opportunities for 3D analysis of features such as particle- and grain-size characterisation, determination of particle densities and shape factors, estimation of mineral associations, and liberation and locking. To date, no simple non-destructive method exists for 3D mineral liberation analysis. We present a new development based on combining μCT with micro-X-ray fluorescence (μXRF) using deep learning. We demonstrate successful semi-automated multimodal analysis of a crystalline magmatic rock by obtaining 2D μXRF mineral maps... [more]

The horizontal-axis ocean current turbine under investigation is a three-blade rotor that uses the flow of water to rotate its blade. The mechanical energy of a turbine is converted into electrical energy using a generator. The horizontal-axis ocean current turbine provides a nongrid robust and sustainable power source. In this study, the blade design is optimized to achieve higher efficiency, as the blade design of the hydrokinetic turbine has a considerable effect on its output efficiency. All the simulations of this turbine are performed on ANSYS software, based on the Reynolds Averaged Navier−Stokes (RANS) equations. Three-dimensional (CFD) simulations are then performed to evaluate the performance of the rotor at a steady state. To examine the turbine’s efficiency, the inner diameter of the rotor is varied in all three cases. The attained result concludes that the highest Cm value is about 0.24 J at a tip-speed ratio (TSR) of 0.8 at a constant speed of 0.7 m/s. From 1 TSR onward,... [more]

Based on a coupled finite element method (FEM) and computational fluid dynamics (CFD) model, the structural deformation and performance of a proton exchange membrane fuel cell (PEMFC) under different membrane water contents are studied. The water absorption behavior of the membrane is investigated experimentally to obtain its expansion coefficient with water content, and the Young’s modulus of the membrane and catalyst (CL) are obtained through a tensile experiment. The simulation results show that the deformation of the membrane increases with water content, and membrane swelling under the channel is larger than that under the rib, forming a surface bump under the channel. The structural changes caused by the membrane water content have little effect on the performance of PEMFC in the low-current density range; while its influence is significant in the medium- and high-current density range. A medium membrane water content value of 12 achieves the best fuel cell performance due to the... [more]

The present review deals with water applications in sub and supercritical conditions with a focus on supercritical water oxidation process (SCWO) as an example of high temperature and pressure technologies. It starts by presenting the advantages of water properties near and beyond the critical point and the major applications exploiting them. Then, it presents a review on SCWO from the description of the process, the reaction mechanism and kinetics to reactor design and modeling. It also presents the main problems and difficulties that delay the SCWO industrial application, and summarizes the main efforts and research to overcome them for a safe, efficient and economic process.

The high amplitude and steep overvoltage generated by the breaking of the vacuum circuit breaker in the wind farm damages the inter-turn insulation of the transformer. There is a certain difference between the simulation results of the traditional reignition model and the measured overvoltage. It is necessary to improve the simulation model to simulate the overvoltage condition of the transformer more accurately and then select appropriate overvoltage protection measures. In this paper, based on the physical process of dielectric recovery during the opening process of the vacuum circuit breaker, a model of dielectric strength recovery is built to simulate the arc reignition of the vacuum circuit breaker. The model was applied to compare the overvoltage protection effects of RC snubbers, surge arresters, and choke coils. The simulation results show that the overvoltage amplitude and reignition times calculated by the model proposed in this paper are closer to the measured values. Compar... [more]

Non-Technical Losses (NTL) represent a serious concern for electric companies. These losses are responsible for revenue losses, as well as reduced system reliability. Part of the revenue loss is charged to legal consumers, thus, causing social imbalance. NTL methods have been developed in order to reduce the impact in physical distribution systems and legal consumers. These methods can be classified as hardware-based and non-hardware-based. Hardware-based methods need an entirely new system infrastructure to be implemented, resulting in high investment and increased cost for energy companies, thus hampering implementation in poorer nations. With this in mind, this paper performs a review of non-hardware-based NTL detection methods. These methods use distribution systems and consumers’ data to detect abnormal energy consumption. They can be classified as network-based, which use network technical parameters to search for energy losses, data-based methods, which use data science and mach... [more]

As key supporting equipment in coal mining, hydraulic supports are vulnerable to impact pressure from roof movement and deformation. In this paper, a mechanical-hydraulic co-simulation platform for hydraulic supports is established. Moreover, the rationality of the simulation platform is verified. Based on this platform, the rigid-flexible coupling impact dynamics model of hydraulic support is built. Finally, by delaying the opening time of the relief valve, the energy dissipation problem of the relief valve hysteresis effect on the hydraulic support system under the rotary impact is discussed. The results indicate that the rotary load acting on the hydraulic support decreases gradually with the backward movement of the roof rotary position, which causes the peak pressure in the column to decrease (by 69 MPa). The hinge point load of different parts shows different load transfer laws. The hysteresis effect of the relief valve prolongs the energy release time of the system, increasing t... [more]

Biomass as a clean and renewable source of energy has immense potential to aid in solving the energy crisis in the world. In order to accurately predict the fluidization behavior of biomass particles using the Eulerian−Eulerian approach and the kinetic theory for granular flows (KTGF), employing appropriate models that adapt to irregularly shaped particles and can precisely predict the interaction between particles is crucial. In this study, the effects of varying radial distribution functions (RDF), frictional viscosity models (FVM), angles of internal friction (ϕ), and stress blending functions (SBF) on the performance of two-fluid models (TFM) were investigated. Simulation predictions were compared and validated with the previous experiments in the literature on Geldart B biomass particles of walnut shells. When applying sphericity to account for size irregularities of biomass particles, the results of this study demonstrated that predictions of both the Ma−Ahmadi and the Carnahan−S... [more]

A 3D computational fluid dynamics (CFD) model was developed to predict the airflow and heat transfer in half of a pallet layer of tomatoes. The numerical and experimental results were compared, and a good agreement was obtained between both results using the root-mean-square error (RMSE) and absolute relative deviation (ARD) values as criteria. The validated CFD model was then used to minimise the product temperature heterogeneity by optimising the airflow rate and the crate design. A downward flow of the air along the central parts of the crates and an upward flow close to the lateral walls of the crates were observed. Three different total ventilated areas (TVAs) were tested to study their influence on the product temperature uniformity and cooling rate. The MTD and ATD decreased from 6.8 to 3.5 °C and from 1.5 to 0.7 °C, respectively, when the TVA was increased from 11 to 15%.

Liquid biowaste represents more than 98% of the total municipal waste streams on wet basis and 4−5% on dry basis. Recent attention has been focused on how to manage it optimally, and several novel technologies are being developed to valorize it. Among the developing alternatives is a technology that operates continuously by integrating a hydrothermal reactor, a gasifier and condenser to recover hydrochar using any produced gases to power the system. This study introduces the “3-step evolution model” in order to simulate the hydrothermal reactor. The model has been developed in a MATLAB/Cantera environment and calculates the outputs as the products of a series of sub-stoichiometric char-gas reactions. Experiments with chicken manure slurry as feedstock were implemented for the validation of the model. Treatment of 32.16 kg/h of chicken manure produces 4.57 kg/h of hydrochar and 3.45 kg/h of syngas. The 3-step evolution model simulated the correct ratio of solid-to-gas, 57−43% (excluding... [more]

Double-diffusive convection plays an important role in many physical phenomena of practical importance. However, the numerical simulation of these phenomena is challenging since fine meshes are often required to capture the flow physics. Hence, several different numerical methods have been employed in the past. This work reports the development and application of an adaptive finite element method for the simulation of these phenomena, thereby avoiding the need for the use of very fine meshes over the whole domain. The weak formulation of the conservation equations for mass, momentum, energy and species concentration is used. The Boussinesq approximation relates the density of the fluid to the temperature and/or the species concentration. A second-order backward difference method is used for time discretization and the Galerkin method is employed for spatial discretization. Both adaptive time step and grid refinement techniques are employed, and the code is parallelized using MPI. Three... [more]

With the wide application of power equipment consisting of high switching frequencies and large current switching devices in the integrated power system on ships, the low-frequency radiation interference caused by the powerful electromagnetic equipment becomes more and more serious. Establishing an equivalent model of radiation interference based on the near-field measurement data is the key to subsequent electromagnetic compatibility design. Due to the large size of the equipment, there will be many measurement points in the near-field measurement area, which leads to long testing times and low modeling efficiency. To solve the above problems, this article first proposes a method of near-field measurement and a modeling method of powerful electromagnetic equipment radiation based on field distribution characteristics. Firstly, the near-field measurement data are obtained by the sparse and uniform sampling of the near-field measurement plane at large sampling intervals. Then, the near-... [more]

Turbulent convective heat-transfer characteristics in a concentric annular channel with both walls heated are theoretically modeled and numerically computed in this article. Generalized algebraic predictive models and equations for heating over a single wall are first reviewed by summarizing the well-known methods in the literature. These methods are then scrutinized according to the most recent investigations such that new viewpoints and corrections are introduced accordingly. Moreover, the application of superposition in temperature is used in the current work instead of the Nusselt number as seen in the literature. The numerical integration method is applied to the generalized equations to obtain the solutions, which are found to be in decent agreement with the direct numerical simulation (DNS) data in the literature. The results in this work also indicate that the wall heat flux density ratio and the annular radius ratio are two key factors that have a great influence on the heat-t... [more]

Given its versatility in drawing power from many sources in the natural world, piezoelectric energy harvesting (PEH) has become increasingly popular. However, its energy harvesting capacities could be enhanced further. Here, a mathematical model that accurately simulates the dynamic behavior and energy harvested can facilitate further improvements in the performance of piezoelectric devices. One of the goals of this study is to create a dependable reduced-order model of a multi-purpose gyroscope. This model will make it possible to compute the harvested voltage and electrical power in a semi-analytical manner. The harvested voltage is often modeled as an average value across the whole electrode surface in piezoelectric devices. We propose a model which provides practical insights toward optimizing the performance of the system by considering a spatially varying electric field across the electrode surface length. Our framework allows investigation of the limits of applicability of the m... [more]

The efficient use of energy is a crucial goal related to the world economy, and efforts are aimed at reducing energy demand for the same quality and quantity of products and services. The drive to improve energy efficiency in the context of technological development, as well as the intensification of industrial and other processes, imposes a constant demand for more efficient heat exchange devices and systems. As devices in which the heat transfer process is crucial, heat exchangers play an essential role in many engineering and other applications. There are several generic techniques for improving the performance of thermal devices, which ultimately manifest through an increase in the heat transfer coefficient as the primary efficiency indicator. These methods include initiating or intensifying the turbulent flow of working fluids, increasing the heat exchange surface by applying specific shapes and additional elements, and using working fluids with improved thermophysical characteris... [more]

Coloured building integrated photovoltaics (BIPVs) may contribute to meeting the decarbonisation targets of European and other countries. Nevertheless, their market uptake has been hindered by a lack of social acceptance, technical issues, and low economic profitability. Being able to assess in advance the influence of the coloured layers on a module’s power generation may help reduce the need for prototyping, thereby allowing optimisation of the product performance by reducing the time and costs of customised manufacturing. Therefore, this review aims at investigating the available literature on models and techniques used for assessing the influence of coloured layers on power generation in customised BIPV products. Existing models in the literature use two main approaches: (i) detailed optical modelling of the layers in the module’s stack, including coloured layers, and (ii) mathematical elaboration of the final product’s measured characteristics. Combining the two approaches can pro... [more]