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•Particle heating receivers (PHRs) allow high temperatures for CSP applications•Novel PHR design uses wire mesh screens to increase thermodynamic performance•Lab scale flow tests of ...PHR design variant were performed•A discrete element method model and a finite volume model were also developed•The discrete element model produces better predictions of experimental mass flux
A proposed design for a concentrating solar power (CSP) receiver uses granular material – such as sand – as the heat transfer and energy storage medium. Early designs of particle heating receivers (PHR) utilize a falling curtain of particles which directly absorbs the concentrated solar radiation. However, falling curtain receivers have several disadvantages including significant heat and particle losses and short residence time within the irradiation zone. One design proposal which overcomes these challenges is the so called “impeded flow PHR design”, in which the particles flow over, around, or through a series of obstacles in the flow path. This reduces the average velocity of the particles, thereby increasing their residence time in the irradiation zone of the receiver. It also reduces heat and particle losses from the receiver. However, granular flows through complex structures are not well understood, rendering a priori design of impeded flow PHR geometries difficult. To better understand these flows, lab scale models of a PHR design variant using horizontal wire mesh screens have been constructed, allowing granular flows through the receiver geometry to be experimentally analyzed. In addition, two different numerical modeling approaches – the discrete element method (DEM) model, and a two-fluid computational fluid dynamics (CFD) model – have been developed to model the flow of particles through the specified receiver geometry. The results of the DEM model are in reasonable agreement with the experimental data with respect to mass flux, and better matches the experimental data than the CFD model. A companion paper presents parametric studies to assess the sensitivity of model predictions to various design and modeling parameters (Sandlin and Abdel-Khalik, 2017).
•Numerical models of a novel particle heating receiver have been developed.•Discrete element method model tracks individual particles.•Computational fluid dynamics model treats granular flow as fluid ...flow.•Parametric studies show sensitivity of mass flux on input parameters.
Numerical methods are increasingly being used to study granular flow phenomena, given the difficulty in extracting data from physical studies. Two common methods are the discrete element method (DEM), and a two fluid computational fluid dynamics (CFD) method. A companion paper (Sandlin and Abdel-Khalik, 2018) compared a DEM model and a CFD model of a granular flow through horizontal wire mesh screens, with experimental data. The aim of this study is to assess the sensitivity of both models to various input parameters. The results of this investigation will guide future modelers of particle heating receivers and other flowing particulate systems in selecting the appropriate modeling options and parameters to enhance the models ability to predict the actual particulate flow characteristics. For the DEM model, it was found that the granular material properties, especially the values for normal and rolling friction, had the largest impact on simulation results. For the CFD model, it was found that the constitutive relationships for frictional pressure, viscosity, and the treatment of physical boundary conditions had the largest impact on simulation outcomes. In addition, both numerical models exhibit a non-monotonic relationship between mass flux and the granular coefficient of restitution, and show reduced mass flux when using a simulation domain with offset wire meshes. The influence of other material properties and sub-modeling options is less pronounced. Methods of obtaining appropriate material properties and sub-modeling options are discussed.
Qualitative comparison of experimental results, discrete element method results, and twin fluid method results for a square tube configuration of a proposed particle heating receiver design for use ...in concentrated solar power applications. Particles flow around and through sections of square tubes. Holes are in the faces at regular intervals, allowing for controllable particle distribution and mixing through the irradiated zone. Display omitted
•Particle heating receivers (PHRs) allow high temperatures for CSP applications.•Novel PHR design uses perforated square tubes for physical robustness.•Lab scale flow tests of PHR design variant were performed.•A discrete element method model and a finite volume model were also developed.•The discrete element model produces better predictions of experimental mass flux.
A proposed design for a concentrating solar power (CSP) receiver uses a granular material - such as sand - as the heat transfer and energy storage medium. Early designs of particle heating receivers (PHR) utilize a falling curtain of particles which directly absorbs the concentrated solar radiation. However, falling curtain receivers have several disadvantages, including significant heat and particle losses, and a short residence time within the irradiation zone. One design proposal which overcomes these challenges is the so called “impeded flow PHR design”, in which the particles flow over, around, or through a series of obstacles in the flow path. This reduces the average velocity of the particles, thereby increasing residence time in the irradiation zone of the receiver. It also reduces heat and particle losses from the receiver. However, granular flows through complex structures are not well understood, rendering a priori design of impeded flow PHR geometries difficult. To better understand these flows, lab scale models of a PHR design variant using a perforated square lattice at an oblique angle have been constructed, allowing granular flows through the receiver geometry to be experimentally analyzed. In addition, two different numerical modeling approaches - the discrete element method (DEM) model, and a two-fluid computational fluid dynamics (CFD) model - have been developed to model the flow of particles through the specified receiver geometry. The results of the DEM model are in reasonable agreement with the experimental data with respect to mass flux, and better matches the experimental data than the CFD model.
Integrated on-board battery chargers (OBCs) have been recently introduced as an optimal/elegant solution to increase electric vehicle (EV) market penetration as well as minimize overall EV cost. ...Unlike conventional off-board and on-board battery chargers, integrated OBCs exploit the existing propulsion equipment for battery charging without extra bulky components and/or dedicated infrastructure. OBCs are broadly categorized into three-phase and single-phase types with unidirectional or bidirectional power flow. This paper starts with surveying the main topologies introduced in the recent literature employing either induction or permanent magnet motors to realize fully integrated slow (single-phase) and fast (three-phase) on-board EV battery charging systems, with emphasis on topologies that entail no or minimum hardware reconfiguration. Although, permanent magnet (PM) motors with conventional double-layer distributed winding layouts have been deployed in most commercial EV motors, the non-overlapped fractional slot concentrated winding (FSCW) has been the prevailing choice in the most recent permanent magnet motor designs due to its outstanding operational merits. Hence, a thorough investigation of the impact different FSCW stator winding designs have on machine performance under the charging process is presented in this paper. To this end, the induced magnet losses, which represent a challenging demerit of the FSCW, have been used to compare different topologies under both propulsion and charging operation modes. Based on the introduced comparative study, the optimal slot/pole combinations that correspond to the best compromise under both operational modes have been highlighted.
This study proposes an isolated on-board integrated battery charger using an interior permanent magnet (IPM) machine with a nine-slot/eight-pole combination or its multiples, and equipped with a ...non-overlapped fractional slot concentrated winding. The proposed winding layout comprises three three-phase winding sets that are connected in such a way as to provide six motor terminals. Hence, a six-phase or two three-phase converters will be required for propulsion. Under motoring mode, the machine can be effectively regarded as a six-phase machine, which provides a high fault-tolerant capability, and allows for a ‘limp home’ mode of operation. Additionally, all magneto motive force subharmonics are eliminated, which significantly reduces the induced rotor eddy current losses, when compared with a conventional three-phase motor having the same slot/pole combination. In battery charging mode, the winding is reconfigured, so that the machine is considered as a three-phase to six-phase rotating transformer. A 40 kW IPM machine is designed and simulated under different modes of operation using two-dimensional finite element analysis to validate the proposed concept. A small-scale prototype machine is also used for experimental validation.
In electric drive applications that are based on high-speed induction motors (IMs) with an extended speed range, stator winding pole-changing is a possible technique to avoid oversizing the driving ...motor. The electronic pole changing employed in multiphase IMs has gained recent interest because it avoids physical winding reconfiguration. The effective number of poles of the air gap flux distribution can be electronically altered by simply changing the applied current sequence to a multiphase stator. The main problem associated with this technique is the significant increase in machine magnetising current with the increase in effective pole number when conventional multiphase distributed windings are employed. This study proposes a new fractional-slot concentrated winding layout with a special stator connection suitable for pole-amplitude modulated IMs that offers a 2:1 pole ratio while maintaining equal magnetising current for both winding pole pairs. Moreover, constant power operation can be achieved for a speed range of over 4 pu. The main concept is discussed and verified through simulations and experimentally. The machine mathematical model and the required vector space decomposition-based controller are also presented.
•Preparation of lead-free CuO/Cs2SnCl6-KI perovskite as a novel photocatalyst.•The photoelectrochemical performance of the CuO/Cs2SnCl6-KI was measured for hydrogen production from wastewater.•The ...incident photon-to-current conversion efficiency was 62.34 % under incident light with a monochromatic of 390 nm.
Although lead halide perovskite materials have fascinating properties, the poisonous lead element and poor stability prevent their potential applications as photocatalysts. In this study, novel lead-free inorganic CuO/Cs2SnCl6-KI perovskites are used as efficient photocatalysts for the generation of H2 from wastewater. The chemical composition, morphological, structural, and optical properties were discussed using various techniques. The CuO/Cs2SnCl6-KI multilayers exhibit micro-stones with octahedral and hexagonal morphology, as well as an average particle size of about 2 µm. The band gap is 2.64 eV for CuO/Cs2SnCl6-KI multilayers. The X-ray diffraction data of the Cs2SnCl6 perovskite shows a cubic structure and average crystallite size of about 38.74 nm. Also, the X-ray photoelectron spectrum (XPS) was used to investigate the chemical composition of Cs2SnCl6-KI thin film. The photoelectrochemical (PEC) performance of the CuO/Cs2SnCl6-KI multilayers was evaluated in wastewater. The photocurrent density at −1 V (RHE) was −15.0 mA.cm−2. The incident photon-to-current conversion efficiency was 62.34 % under incident light with a monochromatic of 390 nm. Investigations are also conducted on photostability, thermodynamic characteristics, and electrochemical impedance of CuO/Cs2SnCl6-KI multilayers. As a result, a brand-new perovskite photoelectrode is introduced for the reliable and effective production of H2.
In many applications, interior permanent magnet synchronous machines (IPMSMs) with fractional slot concentrated windings (FSCWs) are considered promising candidates in terms of higher power density ...and efficiency. In addition, employing a multiphase stator winding improves the drive train availability and increases reliability. This study investigates the effect of applying stator shifting to five-phase FSCW winding IPMSMs to suppress the effect of the slot harmonics by doubling the number of slots. In this case, the winding coil pitch will be two, which stands as a compromise between single-tooth and distributed winding topologies. This highly improves the air gap flux distribution, significantly reduces both rotor core and magnet eddy current losses, and increases saliency ratio and reluctance torque component. Moreover, an improved performance under fault conditions, in terms of lower torque ripple, and core and magnet losses, adds to the main advantages of this technique. Various slot/pole combinations suitable for five-phase machines are investigated. A full simulation case study based on two-dimensional finite element analysis is applied to the 20-slot/18-pole stator with single-tooth winding under both healthy and open-circuit phase fault cases.
Six-phase induction machines have mostly shown promise in high-power electric drive applications as well as wind energy conversion systems. Different winding configurations for six-phase stators have ...been published, namely, dual three-phase (D3P), symmetrical six-phase (S6P), and asymmetrical six-phase (A6P) winding layouts. Although a body of research investigating six-phase machines and their control for different six-phase winding arrangements exists, a thorough comparative study between these different arrangements in terms of machine parameters and performance, has not been done so far. This paper employs a 12-phase stator with a configurable terminal box to compare different six-phase configurations by simply reconnecting the stator terminals of the twelve phases in different manners to obtain an equivalent six-terminal stator. This way, the same stator machine dimensions and copper volume will be assumed for all connections. The comparative study focuses on the effect of winding connection on machine parameters of the different subspaces, phase current quality and machine characteristic curves. Experimental validation has been carried out using a 1kW prototype system.
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