In this paper, a novel two-phase linear hybrid reluctance actuator with the double-sided segmented stator, made of laminated U cores, and an interior mover with permanent magnets is proposed. The permanent magnets are disposed of in a way that increases the thrust force of a double-sided linear switched reluctance actuator of the same size. To achieve this objective, each phase of the actuator is powered by a single H-bridge inverter. To reduce the detent force, the upper and the lower stator were shifted. Finite element analysis was used to demonstrate that the proposed actuator has a high force density with low detent force. In addition, a comparative study between the proposed linear hybrid reluctance actuator, linear switched reluctance, and linear permanent magnet actuators of the same size was performed. Finally, experimental tests carried out in a prototype confirmed the goals of the proposed actuator.

GaN-based power semiconductors exhibit small on-resistance and high dv/dt of the switch characteristics, thereby enabling the construction of high-efficiency, high-density semiconductor systems with fast switching and low power loss characteristics and miniaturization of passive devices. However, owing to the characteristics of GaN devices that result in them being significantly faster than other devices, the accuracy of the switching transient response significantly affects the noise or inductance in the device. Therefore, securing sufficient sensor bandwidth is considerably important for accurate current measurement in GaN-based devices. Conversely, the current sensor in the form of a non-insulated coil must secure sufficient bandwidth and overcome the tradeoff relationship with measurement sensitivity; moreover, the sensor configuration must be applicable to various power semiconductor types. This study proposes a current sensor model that applies the principle of the printed circui... [more]

The objective of this study is to investigate the performance characteristics of a small-sized R600a household refrigeration system that adopts a condenser outlet split (COS) ejector cycle under various operating and ejector geometry conditions. The coefficient of performance and pressure lifting ratio of the COS ejector cycle were analyzed and measured by varying the entrainment ratio, compressor speed, and nozzle exit position. The optimum nozzle exit position in the COS ejector cycle adopted to achieve the maximum cycle performance was proposed as a function of the compressor speed and entrainment ratio. The optimum nozzle exit position was 0 mm when the entrainment ratio and compressor speed were low, and it increased as the entrainment ratio and compressor speed increased owing to the associated internal pressure drop in the suction section.

A two-dimensional axisymmetric thermal-fluid-solid coupled mathematical model of a contact mechanical seal is established. The finite difference method is used to solve the control equations for the fluid pressure and temperature of the seal end face, and the finite element method is used to determine the thermal deformation state of the seal. The seal’s performance at different working speeds was studied and verified by experiments. The results show that under the combined actions of thermal and mechanical deformations, the seal end face forms a convergent leakage gap from the outer diameter to the inner diameter. The minimum film thickness is observed on the inner diameter side of the seal end face, and the highest end face temperature coincides with this location. With increasing working speed, the contact force at the inner diameter side increases, the temperature difference between the inner diameter and the outer diameter of the end face increases, and the leakage rate correspond... [more]

Many agricultural waste residues are generated in Southeast Asia while some areas in the region still do not have electricity. This study explores the potential effective utilization of agricultural residues in Southeast Asia to generate power. Firstly, visualization of the potential for energy generation was completed using a geographic information system (GIS). Secondly, a comparison of effectiveness was completed between the torrefaction and hydrothermal treatment of low-grade agricultural residues as pretreatment techniques for the modification of agricultural residues. In this study, the feasibility of utilizing rice residues was analyzed (i.e., rice husks, which are produced in large quantities in Southeast Asia) to determine their suitability for pretreatment as feedstock for power plants. This was assessed experimentally by focusing on the pyrolytic characteristics of the husks and the rate of ash change both before and after treatment, while the subsequent implications on tran... [more]

This paper analyzes a resonant inductive wireless power transfer link using a single transmitter and multiple receivers. The link is described as an (N+1)−port network and the problem of efficiency maximization is formulated as a generalized eigenvalue problem. It is shown that the desired solution can be derived through simple algebraic operations on the impedance matrix of the link. The analytical expressions of the loads and the generator impedances that maximize the efficiency are derived and discussed. It is demonstrated that the maximum realizable efficiency of the link does not depend on the coupling among the receivers that can be always compensated. Circuital simulation results validating the presented theory are reported and discussed.

To investigate the impacts of using nano-enhanced phase change materials on the thermal performance of a borehole heat exchanger in the summer season, a three-dimensional numerical model of a borehole heat exchanger is created in the present work. Seven nanoparticles including Cu, CuO, Al2O3, TiO2, SiO2, multi-wall carbon nanotube, and graphene are added to the Paraffin. Considering the highest melting rate and lowest outlet temperature, the selected nano-enhanced phase change material is evaluated in terms of volume fraction (0.05, 0.10, 0.15, 0.20) and then the shape (sphere, brick, cylinder, platelet, blade) of its nanoparticles. Based on the results, the Paraffin containing Cu and SiO2 nanoparticles are found to be the best and worst ones in thermal performance improvement, respectively. Moreover, it is indicated that the increase in the volume fraction of Cu nanoparticles could enhance markedly the melting rate, being 0.20 the most favorable value which increased up to 55% the the... [more]

Electrical energy storage will play a key role in the transition to a low carbon energy network. Liquid air energy storage (LAES) is a thermal−mechanical energy storage technology that converts electricity to thermal energy. This energy is stored in three ways: as latent heat in a tank of liquid air, as warm sensible heat in a hot tank and as cold sensible heat in a packed bed regenerator (PBR), which is the focus of this paper. A PBR was selected because the temperature range (−196 °C to 10 °C) prohibits storage in liquid media, as most fluids will undergo a phase change over a near 200 °C temperature range. A change of phase in the storage media would result in exergy destruction and loss of efficiency of the LAES device. Gravel was selected as the storage media, as (a) many gravels are compatible with cryogenic temperatures and (b) the low cost of the material if it can be used with minimal pre-treatment. PBRs have been extensively studied and modelled such as the work by Schumann,... [more]

In decentralized energy systems, electricity generated and flexibility offered by households can be organized in the form of community energy systems. Business models, which enable this aggregation at the community level, will impact on the involved actors and the electricity market. For the case of Germany, in this paper different aggregation scenarios are analyzed from the perspective of actors and the market. The main components in these scenarios are the Community Energy Storage (CES) technology, the electricity tariff structure, and the aggregation goal. For this evaluation, a bottom-up community energy system model is presented, in which the households and retailer are the key actors. In our model, we distinguish between the households with inflexible electricity load and the flexible households that own a heat pump or Photovoltaic (PV) storage systems. By using a game-theoretic approach and modeling the interaction between the retailer and households as a Stackelberg game, a com... [more]

This study is a preliminary and experimental one to analyze Japan’s energy transitions to mitigate climate change from anticipatory governance aspects. Japan’s energy policy principles have been energy security, environmental considerations, economic efficiency, and safety (3E + S). According to the energy agency, the long-term energy outlook is also drawn up by “ambitious multiple track scenarios” and “multilayered and diversified flexible energy supply-demand structure.” This approach resonates with the aspects of anticipatory governance. It promotes the idea of preparing for multiple future scenarios, including the unthinkable worst case future scenario such as a nuclear accident (foresight), the interactions between the policymakers and the public (engagement), and the reflexive processes of policy innovations with a normative decision for the selection of energy mix (integration). However, this study finds that Japan’s energy policy lacks the aspects of anticipatory governance. It... [more]

Anomaly detection for wind turbine condition monitoring is an active area of research within the wind energy operations and maintenance (O & M) community. In this paper three models were compared for multi-megawatt operational wind turbine SCADA data. The models used for comparison were One-Class Support Vector Machine (OCSVM), Isolation Forest (IF), and Elliptical Envelope (EE). Each of these were compared for the same fault, and tested under various different data configurations. IF and EE have not previously been used for fault detection for wind turbines, and OCSVM has not been used for SCADA data. This paper presents a novel method of condition monitoring that only requires two months of data per turbine. These months were separated by a year, the first being healthy and the second unhealthy. The number of anomalies is compared, with a greater number in the unhealthy month being considered correct. It was found that for accuracy IF and OCSVM had similar performances in both traini... [more]

The main aim of this study is to evaluate the results achieved by implementation of different support policies in form of subsidies for energy efficiency improvements and transition to renewable energy sources. The article compares the energy efficiency measures in district heating systems with other support program. In order to assess the effectiveness of implementation of different renewable energy technologies and energy efficiency projects, the levelized costs of saved energy for different support programs were determined. Authors compared different co-financed projects related to replacement of fossil fuel energy sources in district heating (mainly to biomass) and the installation of new biomass boilers, heat pumps, solar collectors and other local technologies in municipal buildings. Results show that financial support for energy efficiency measures in industrial enterprises and district heating systems has been most cost-effective, mainly due to the low co-financing rate (30%) a... [more]

The paper presents the results of research on liquid flow maldistribution in the shell side of a shell-and-tube heat exchanger (STHE). This phenomenon constitutes the reason for the formation of the velocity reduction area and adversely affects heat transfer and pressure drop. In order to provide details of the liquid distribution in STHE, two visualization methods were utilized. First, computational fluid dynamics (CFD) code coupled with the k-ε model and the laser-based particle image velocimetry (PIV) technique was applied. The tests were carried out for a bundle comprising 37 tubes in an in-line layout with a pitch dz/t = 1.5, placed in a shell with Din = 0.1 m. The STHE liquid feed rates corresponded to Reynolds numbers Rein equal to 16,662, 24,993, and 33,324. The analysis demonstrated that the flow maldistribution in the investigated geometry originates the result of three main streams in the cross-section of the shell side: central stream, oblique stream, and bypass stream. For... [more]

The area-proportional baseline method generates phase fraction−temperature curves from heat capacity data of phase change materials. The curves describe the continuous conversion from solid to liquid over an extended temperature range. They are consistent with the apparent heat capacity and enthalpy modeling approach for the numerical solution of heat transfer problems. However, the curves are non-smooth, discrete signals. They are affected by noise in the heat capacity data and should not be used as input to continuous simulation models. This contribution proposes an alternative method based on spline approximation for the generation of consistent and smooth phase fraction−temperature, apparent heat capacity−temperature and enthalpy−temperature curves. Applications are presented for two commercial paraffins from Rubitherm GmbH considering heat capacity data from Differential Scanning Calorimetry and 3-layer-calorimetry. Apparent heat capacity models are validated for melting experimen... [more]

The mechanical power and wake flow field of a 1:40 scale model of the US Department of Energy’s Reference Model 1 (RM1) dual rotor tidal energy converter are characterized in an open-channel flume to evaluate power performance and wake flow recovery. The NACA-63(4)-24 hydrofoil profile in the original RM1 design is replaced with a NACA-4415 profile to minimize the Reynolds dependency of lift and drag characteristics at the test chord Reynolds number. Precise blade angular position and torque measurements were synchronized with three acoustic Doppler velocimeters (ADV) aligned with each rotor centerline and the midpoint between the rotor axes. Flow conditions for each case were controlled to maintain a hub height velocity, uhub= 1.04 ms−1, a flow Reynolds number, ReD= 4.4 × 105, and a blade chord length Reynolds number, Rec= 3.1 × 105. Performance was measured for a range of tip-speed ratios by varying rotor angular velocity. Peak power coefficients, CP= 0.48 (right rotor) and CP= 0.43... [more]

State Estimation (SE) is one of the essential tasks to monitor and control the smart power grid. This paper presents a method to estimate the state variables combining the measurement of power demand at each bus with the data collected from a limited number of Phasor Measurement Units (PMUs). Although PMU data are usually assumed to be perfectly synchronized with the Coordinated Universal Time (UTC), this work explicitly considers the presence of time-synchronization errors due, for instance, to the actual performance of GPS receivers and the limited stability of the internal oscillator. The proposed algorithm is a recursive Kalman filter which not only estimates the state variables of the power system, but also the frequency deviations causing clock offsets which eventually affect the timestamps of the measures returned by different PMUs. The proposed solution was tested and compared with alternative approaches using both synthetic data applied to the IEEE 123 bus distribution feeder... [more]

We present simulations of turbulent detached flows using the commercial lattice Boltzmann solver XFlow (by Dassault Systemes). XFlow’s lattice Boltzmann formulation together with an efficient octree mesh generator reduce substantially the cost of generating complex meshes for industrial flows. In this work, we challenge these meshes and quantify the accuracy of the solver for detached turbulent flows. The good performance of XFlow when combined with a Large-Eddy Simulation turbulence model is demonstrated for different industrial benchmarks and validated using experimental data or fine numerical simulations. We select five test cases: the Backward-facing step the Goldschmied Body the HLPW-2 (2nd High-Lift Prediction Workshop) full aircraft geometry, a NACA0012 under dynamic stall conditions and a parametric study of leading edge tubercles to improve stall behavior on a 3D wing.

Growing consciousness of the threat posed by man-made climate change has spurred government institutions, industry, and science to find clean fuels to power economic activity. Fuel cells powered by hydrogen are one of the steps in gaining clean energy. To improve the efficiency of the fuel cell, the hybrid solutions are required. This article shows a new approach to the design and control of a hybrid energy storage system for portable applications. The methodology allows us to optimize the desired physical parameters of the elements (weight or size) in order to withstand the connected load power demand. Such an approach allows us to minimize weight, which is essential in portable systems. The methodology was proven by building a technology demonstrator. The measurements of physical objects verified the electrical parameters received during simulation and allowed a lower weight of the system, compared to the system based only on Li-ion batteries.

Potential-induced degradation (PID) of photovoltaic (PV) cells is one of the most severe types of degradation, where the output power losses in solar cells may even exceed 30%. In this article, we present the development of a suitable anti-reflection coating (ARC) structure of solar cells to mitigate the PID effect using a SiO2 ARC layer. Our PID testing experiments show that the proposed ARC layer can improve the durability and reliability of the solar cell, where the maximum drop in efficiency was equal to 0.69% after 96 h of PID testing using an applied voltage of 1000 V and temperature setting at 85 °C. In addition, we observed that the maximum losses in the current density are equal to 0.8 mA/cm2, compared with 4.5 mA/cm2 current density loss without using the SiO2 ARC layer.

Despite strong political efforts in Europe, industrial small- and medium-sized enterprises (SMEs) seem to neglect adopting practices for energy efficiency. By taking a cultural perspective, this study investigated what drives the establishment of energy efficiency and corresponding practices in SMEs. Based on 10 ethnographic case studies and a quantitative survey among 500 manufacturing SMEs, the results indicate the importance of everyday employee behavior in achieving energy savings. The studied enterprises value behavior-related measures as similarly important as technical measures. Raising awareness for energy issues within the organization, therefore, constitutes an essential leadership task that is oftentimes perceived as challenging and frustrating. It was concluded that the embedding of energy efficiency in corporate strategy, the use of a broad spectrum of different practices, and the empowerment and involvement of employees serve as major drivers in establishing energy effici... [more]

Shale formations are attractive prospects due to their potential in oil and gas production. Some of the largest shale formations in the mainland US, such as the Tuscaloosa Marine Shale (TMS), have reserves estimated to be around 7 billion barrels. Despite their huge potential, shale formations present major concerns for drilling operators. These prospects have unique challenges because of all their alteration and incompatibility issues with drilling and completion fluids. Most shale formations undergo numerous chemical and physical alterations, making their interaction with the drilling and completion fluid systems very complex to understand. In this study, a high-pressure, high-temperature (HPHT) drilling simulator was used to mimic real time drilling operations to investigate the performance of inhibitive drilling fluid systems in two major shale formations (Eagle Ford Shale and Tuscaloosa Marine Shale). A series of drilling experiments using the drilling simulator and clay swelling... [more]

The main goal of this paper is to prove that bi-objective optimization of high-pressure gas networks ensures grater system efficiency than scalar optimization. The proposed algorithm searches for a trade-off between minimization of the running costs of compressors and maximization of gas networks capacity (security of gas supply to customers). The bi-criteria algorithm was developed using a gradient projection method to solve the nonlinear constrained optimization problem, and a hierarchical vector optimization method. To prove the correctness of the algorithm, three existing networks have been solved. A comparison between the scalar optimization and bi-criteria optimization results confirmed the advantages of the bi-criteria optimization approach.

High transportation costs make energy and food expensive in remote communities worldwide, especially in high-latitude Arctic climates. Past attempts to grow food indoors in these remote areas have proven uneconomical due to the need for expensive imported diesel for heating and electricity. This study aims to determine whether solar photovoltaic (PV) electricity can be used affordably to power container farms integrated with a remote Arctic community microgrid. A mixed-integer linear optimization model (FEWMORE: Food−Energy−Water Microgrid Optimization with Renewable Energy) has been developed to minimize the capital and maintenance costs of installing solar photovoltaics (PV) plus electricity storage and the operational costs of purchasing electricity from the community microgrid to power a container farm. FEWMORE expands upon previous models by simulating demand-side management of container farm loads. Its results are compared with those of another model (HOMER) for a test case. FEWM... [more]

The construction of metro line energy management center (MLEMC) is one of the important parts of metro line, which is the key organization to realize the energy consumption management of the metro operation. To protect the safety of adjacent high-rise buildings during the blasting of subway foundation pit engineering, it is crucial to study the response characteristics of building structures. This paper takes the MLEMC vertical pit blasting project of Wuhan Metro Line 8 as an example. The law of blasting vibration attenuation along the earth’s surface and the vibration velocity response characteristics of the building structure were analyzed by small explosive test. LSDYNA numerical model was established, and the reliability of the model and parameters was verified by experimental data. Combined with the relevant specifications, the maximum charge in single delay was calculated and analyzed. The numerical model of the maximum charge in single was established, and the prediction model o... [more]

In this paper, a superconducting fault current limiting breaker (SFCLB) using flux coupling with a tap changer is suggested and its effective fault current limiting and breaking characteristics due to the winding method using its tap changer are analyzed. The suggested SFCLB using flux coupling, which consists of the SFCLB using flux coupling with a tap changer, mechanical switch and driving coil, can perform the circuit-breaking function without external driving power after the fault current limiting operation. To examine the suggested SFCLB’s operation, the small scale SFCLB using flux coupling was fabricated and alternative current (AC) short-circuit experiments due to the winding method using the tap changer of the SFCLB were executed. From the experimental results, a lower fault current limiting rate and faster breaking time in the case of a SFCLB with a series connection could be obtained compared to one with a parallel connection.