The sustainable development of an organisation requires a holistic approach to the evaluation of an enterprise’s goals and activities. The essential means enabling an organisation to achieve goals are business processes. Properly managed, business processes are a source of revenue and become an implementation of business strategy. The critical elements in process management in an enterprise are process monitoring and control. It is therefore essential to identify the Key Performance Indicators (KPIs) that are relevant to the analysed processes. Process monitoring can be performed at various levels of management, as well as from different perspectives: operational, financial, security, or maintenance. Some of the indicators known from other fields (such as personnel management, finance, or lean manufacturing) can be used in mining. However, the operational mining processes require a definition of specific indicators, especially in the context of increasing the productivity of mining mac... [more]

Computationally modelling a nuclear reactor startup core for a benchmark against the existing models is highly desirable for an independent assessment informing nuclear engineers and energy policymakers. For the first time, this work presents a startup core model of the UK’s first Evolutionary Pressurised Water Reactor (EPR) based on Monte Carlo simulations of particle collisions using Serpent 2, a state-of-the-art continuous-energy Monte Carlo reactor physics burnup code. Coupling between neutronics and thermal-hydraulic conditions with the fuel depletion is incorporated into the multi-dimensional branches, obtaining the thermal flux and fission reaction rate (power) distributions radially and axially from the three dimensional (3D) single assembly level to a 3D full core. Shannon entropy is quantified to characterise the convergence behaviour of the fission source distribution, with 3 billion neutron histories tracked by parallel computing. Source biasing is applied for the variance... [more]

This article proposes a holistic codesign optimization framework (COF) to simultaneously optimize a power conversion stage and a controller stage using a dual-loop control scheme for multiphase SiC-based DC/DC converters. In this study, the power conversion stage adopts a non-isolated interleaved boost converter (IBC). Besides, the dual-loop control scheme uses type-III controllers for both inner- and outer- loops to regulate the output voltage of the IBC and tackle its non-minimum phase issue. Based on the converter architecture, a multi-objective optimization (MOO) problem including four objective functions (OFs) is properly formulated for the COF. To this end, total input current ripple, total weight of inductors and total power losses are selected as three OFs for the power conversion stage whilst one OF called integral of time-weighted absolute error is considered for the controller stage. The OFs are expressed in analytical forms. To solve the MOO problem, the COF utilizes a non-... [more]

The dielectric strength and gel time of epoxy composites vary with the mixing ratio of epoxy resin, hardener, additives, filler, etc., and especially the gel time affects the productivity and economics of ultra-high-voltage (UHV) equipment. However, previous studies focused only on the dielectric strength of epoxy composites for the reliability of UHV equipment. Therefore, a study considering both the dielectric strength and gel time of the epoxy composite is required. In this paper, the characteristics of the gel time and dielectric strength of the epoxy micro-composites according to the mixing ratio of silica (SiO2) and alumina (Al2O3) micro-fillers without changing the mixing ratio of epoxy resin and hardener are analyzed. Experimental results show that the gel time decreased and the dielectric strength increased as the mixing ratio of the SiO2 micro-filler increased. Therefore, it is concluded that the gel time can be controlled by changing the mixing ratio of micro-fillers without... [more]

The problem of diminishing resources on our plant is now getting due attention from the governments as well as scientists around the world. The transition from a linear economy to a circular economy (CE) is now among the top priorities. This article discusses the implementation of the circular economy paradigm in Poland through the analysis of the existing and planned mechanisms, and actions taken by the Polish government which can be replicated by other young European countries. Further, the article discusses the direction of change and projected measures planned by the Polish government to improve the quality of municipal solid waste management. In this context, profitability analysis is carried out for two methods of waste processing (incineration and torrefaction) intended for small municipalities and settlements in which district heating and trading of generated electricity are not feasible. The results of the analysis shows that torrefaction is clearly a more desirable waste proc... [more]

The present study develops a novel optimization method for designing a Stirling engine by combining a variable-step simplified conjugate gradient method (VSCGM) and a neural network training algorithm. As compared with existing gradient-based methods, like the conjugate gradient method (CGM) and simplified conjugate gradient method (SCGM), the VSCGM method is a further modified version presented in this study which allows the convergence speed to be greatly accelerated while the form of the objective function can still be defined flexibly. Through the automatic adjustment of the variable step size, the optimal design is reached more efficiently and accurately. Therefore, the VSCGM appears to be a potential and alternative tool in a variety of engineering applications. In this study, optimization of a low-temperature-differential gamma-type Stirling engine was attempted as a test case. The optimizer was trained by the neural network algorithm based on the training data provided from thr... [more]

Green roofs have a thermal insulating effect known since ancient times. In the building sector, green roofs represent a sustainable passive solution to obtain energy savings, both during winter and summer. Moreover, they are a natural barrier against noise pollution, reducing sound reflections, and they contribute to clean air and biodiversity in urban areas. In this research, a roof-lawn system was studied through a long experimental campaign. Heat-flow meters, air and surface temperature sensors were used in two buildings characterized by different surrounding conditions, geometries and orientations. In both case studies, the thermal behaviors of the roof-lawn system were compared with the conventional roofs. In addition, a dynamic simulation model was created in order to quantify the effect of this green system on the heating and cooling energy demands. The roof-lawn showed a high thermal inertia, with no overheating during summer, and a high insulating capacity, involving energy sa... [more]

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.