Water hyacinth (WH) is an invasive aquatic macrophyte that dominates freshwater bodies across the world. However, due to its rapid growth rate and wide-spread global presence, WH could offer great potential as a biomass feedstock, including for bioenergy generation. This study compares different integration strategies of hydrothermal carbonisation (HTC) and anaerobic digestion (AD) using WH, across a range of temperatures. These include (i) hydrochar combustion and process water digestion, (ii) hydrochar digestion, (iii) slurry digestion. HTC reactions were conducted at 150 °C, 200 °C, and 250 °C. Separation of hydrochars for combustion and process waters for digestion offers the most energetically-feasible valorisation route. However, hydrochars produced from WH display slagging and fouling tendencies; limiting their use in large-scale combustion. AD of WH slurry produced at 150 °C appears to be energetically-feasible and has the potential to also be a viable integration strategy betw... [more]

Wine lees have a great potential to obtain clean energy in the form of biogas through anaerobic digestion due to their high organic load. However, wine lees are a complex substrate and may likely give rise to instabilities leading to failure of the biological process. This work analysed the digestion of wine lees using two different approaches. First, electro-oxidation was applied as pre-treatment using boron-doped diamond-based electrodes. The voltage was 25 V and different treatment times were tested (ranging from 0.08 to 1.5 h) at 25 °C. Anaerobic digestion of wine lees was evaluated in batch tests to investigate the effect of electro-oxidation on biogas yield. Electro-oxidation exhibited a significant positive effect on biogas production increasing its value up to 330 L kg−1 of volatile solids after 1.5 h of treatment, compared to 180 L kg−1 of volatile solids measured from raw wine lees. As a second approach, the addition of biochar to the anaerobic digestion of wine lees was inve... [more]

To validate the potentials of unequal-length section-varied geometry in developing a orthoplanar spring-based piezoelectric vibration energy harvester (PVEH), a modified spring with quad-trapezoidal-leg configuration is designed, analyzed, and fabricated. A basic quad-trapezoidal-leg orthoplanar spring (QTOPS) is theoretically analyzed, and the structural effective stress and eigenfrequency are formulated to determine the main dimension parameters. Then, an improved QTOPS with additional intermediations is constructed and simulated. Porotypes with different leg geometries and mass configurations are fabricated and tested. The results of QTOPS and a conventional rectangular-shaped spring are compared. It is verified that the proposed approach provides the structure with an enlarged effective stress and lower resonant frequency, which makes it more suitable to construct a high-performance PVEH than the orthoplanar spring with equal-length or rectangular legs.

A passive regulation system for the water content has been developed and evaluated for a proton exchange membrane fuel cell. It is of particular relevance for micro-fuel cells, whose volume, weight and extra-consumption of fuel and power for subsidiary components must be kept to a minimum. This solution consists of a self-regulating humidity system implemented at the anode chamber that allows free water exchange with the environment through the surface of a gas-tight membrane. The micro-fuel cell, which is designed according to the patent WO2015025070A1, has been assembled and operated under completely passive conditions. The behavior of the anode humidity regulation system has been analyzed externally and in situ. The external part of the anode, where the humidity exchange with the environment takes place, has been isolated in a closed chamber and a hygrometer has been used to register the relative humidity in the zone near to the water exchange film. The results obtained from the ope... [more]

In a bid to respond to the challenges being faced in the installation of flywheel-based electric energy storage systems (EESSs) in customer-side facilities, namely high safety, high energy/power densities and low cost, research work towards the development of a novel, one-body, laminated-rotor flywheel, based on a switched reluctance machine (OBOLAR-Fly SR machine) is presented, where the laminated rotor provides both the energy storage and motor/generator functions. The one-body architecture improves compactness and robustness. Besides, the rotor’s laminated body ensures inherently high safety. From the design perspective, the rotor’s dual purpose causes the traditional electrical machines design aspects, such as power development, cooling, losses, torque ripple, etc., to clash with the typical requirements of a flywheel, namely in-vacuum operation and moment of inertia. This results in six main trade-offs to be addressed during the design process: rotor material, speed ratio, number... [more]

In Saudi Arabia, residential buildings are one of the major contributors to total energy consumption. Even though there are abundant natural resources, it is somewhat difficult to apply them to building designs, as design variables, due to slow progress and private issues in Saudi Arabia. Thus, the present study demonstrated the development of sustainable residential building design by examining the daylighting and energy performance with design variables. Focusing on the daylighting system, the design variables were chosen, including window-to-wall ratios (WWR), external shading devices, and types of glazing. The illuminance level by these design variables in a building was evaluated by using daylight metrics, such as spatial daylight autonomy and annual sunlight exposure. Moreover, the building energy consumption with these design variables was analyzed by using energy simulation. As a result, the daylighting was improved with the increase in WWRs and the tinted double glazing, while... [more]

An axial flow fan, which is applied for ventilation in underground spaces such as tunnels, features a medium−large size, and most of the blades go through the casting process in consideration of mass production and cost. In the casting process, post-work related to roughness treatment is essential, and this is a final operation to determine the thickness profile of an airfoil which is designed from the empirical equation. In this study, the effect of the thickness profile of an airfoil on the performance and aerodynamic characteristics of the axial fan was examined through numerical analysis with the commercial code, ANSYS CFX. In order to conduct the sensitivity analysis on the effect of the maximum thickness position for each span on the performance at the design flow rate, the design of experiments (DOE) method was applied with a full factorial design as an additional attempt. The energy loss near the shroud span was confirmed with a quantified value for the tip leakage flow (TLF) r... [more]

The demand for carbon capture is increasing over time due to rising CO2 levels in the atmosphere. Even though fossil emission could be decreased or even eliminated, there is a need to start removing CO2 from the atmosphere. The removed CO2 could be either stored permanently to a reservoir (CCS, Carbon Capture and Storage) or utilized as a raw material in a long-lasting product (CCU, Carbon Capture and Utilization). The capture of CO2 could be done by direct air capture, or capturing CO2 from biogenic sources. Amine absorption is the state-of-the-art method to capture CO2, but it has some drawbacks: toxicity, high heat demand, and sorbent sensitivity towards impurities such as sulfur compounds and degradation in cyclic operation. Another potential solvent for CO2 could be water, which is easily available and safe to use in many applications. The problem with water is the poorer solubility of CO2, compared with amines, which leads to larger required flow rates. This study analyzed the te... [more]

Steady-state, harmonics, and transient analysis of a power system by using a detailed simulation model is essential to microgrid operation before the installation of new power facilities, because the microgrid, which is a small-scale independent power grid consisting of distributed resources and an energy storage system, has no choice but to include many inverters consisting of switching devices. Accordingly, in the case of an accident in a microgrid system, various power system simulation tools must be used to calculate the fault current for grid protection components. Specifically, Modelling using Power System Computer Aided Design (PSCAD)/Electro-Magnetic Transient Design and Control (EMTDC) can perform detailed modeling of switching devices into each inverter, and Electrical Transient Analyzer Program (ETAP) can design protection relays. From this perspective, this study designed whole protection components in a microgrid system, including the capacity of switching devices for faul... [more]

In Wireless Sensor Networks (WSNs), server clusters, and other systems requiring secure transmission, the overhead of data encryption and transmission is often not negligible. Unfortunately, a conflict exists between security and efficiency in processing data. Therefore, this paper proposes a strategy to overcome this conflict, called Client-Aware Negotiation for Secure and Efficient Data Transmission (CAN-SEAT). This strategy allows a client with different security transmission requirements to use the appropriate data security transmission without modifying the client. Two methods are designed for different clients. The first method is based on two-way authentication and renegotiation. After handshakes, the appropriate data security transmission scheme is selected according to the client requirements. Another method is based on redirection, which can be applied when the client does not support two-way authentication or renegotiation. For the characteristics of different architecture,... [more]

As international regulations of motor efficiency are strengthened, the line-start synchronous reluctance motor (LS-SynRM) is being studied to improve the efficiency of the electrical motor in industrial applications. However, in industrial applications, the power factor is also an important performance index, but the LS-SynRM has poor power factor due to the saliency characteristic. In this paper, the rotor design of LS-SynRM is performed to improve the efficiency and power factor. First, the barrier design is performed to improve the efficiency and power factor using the response surface method (RSM). Second, the rotor slot design is performed according to the length of bar for synchronization. Lastly, the rib design is performed to satisfy the power factor and the mechanical reliability. The final model through the design process is analyzed using finite element analysis (FEA), and the objective performance is satisfied. To verify the FEA result, the final model is manufactured, and... [more]

This paper provides an analysis of a designed underground station infrastructure for vacuum tube high-speed trains for the planned mega transport hub in Poland. The potential of integrating the infrastructure of the station building with sealed low-pressure tubes system is analyzed. The Solidarity Transport Hub Poland is a planned mega hub to be located in Baranów Municipality, Poland, which is comprised of an airport, an airport city, a road, and railway infrastructure. It is to be integrated with the first route of vactrains in Poland. The aim of this paper is to design a hyperloop station building adequate for the advanced technology of low-pressure high-speed trains. Designing a hyperloop station is not trivial, due to technological aspects which have not been hitherto present in airport or railway planning and design, such as low-pressure zones or airlocks which determine possible passenger paths and evacuation roads. Both the mega airport and Polish hyperloop are in the planning... [more]

Slotted liners are widely used in steam-assisted gravity drainage (SAGD) wells to control sand production and sustain wellbore productivity. The slotted liner can provide desirable performance when appropriately designed. A literature review indicates a limited number of studies that offer design criteria specifically for SAGD wells. Moreover, past criteria seem to neglect some key factors, which may lead to inadequate slot design. This paper proposes a set of graphical design criteria for slotted liners in SAGD production wells, using prepacked sand retention testing (SRT) data. The SRT is designed to incorporate several essential factors that are not present in the past design criteria, such as slot density, steam breakthrough, and particle size distribution (PSD). The proposed design criteria are presented graphically for normal and aggressive conditions, where the aggressive condition accounts for the potential occurrence of the steam breakthrough. It is found that the upper bound... [more]

Thermal performance enhancement in microchannel heat sinks has recently become a challenge due to advancements in modern microelectronics, which demand compatibility with heat sinks able to dissipate ever-increasing amounts of heat. Recent advancements in manufacturing techniques, such as additive manufacturing, have made the modification of the microchannel heat sink geometry possible well beyond the conventional rectangular model to improve the cooling capacity of these devices. One such modification in microchannel geometry includes the introduction of secondary flow channels in the walls between adjacent mainstream microchannels. The present study computationally models secondary flow channels in regular trapezoidal and parallel orientations for fluid circulation through the microchannel walls in a heat sink design. The heat sink is made of silicon wafer, and water is used as the circulating fluid in this study. Continuity, momentum, and energy equations are solved for the fluid fl... [more]

In the era of expensive energy carriers and care for the climate, companies are keen to take action towards bolstering energy efficiency. Businesses often lack data on actual energy consumption to date, are rarely equipped with adequate analytical tools, and do not have the know-how regarding the transition itself. Developing energy efficiency management (EEM) for a given enterprise requires many steps, which ultimately unleash analytical potential and seamlessly integrate the EEM framework with the business model of a given company. This study scrutinizes and formalizes a reference process of pilot EEM implementation that involves external business partners in a multi-facility organization. The process is tailored to the specificity of the company’s operations as well as its technical and management capabilities regarding energy efficiency. The proposed approach, phased in time and involving multiple stakeholders, should be especially useful for practitioners running EEM-related proje... [more]

Currently, there is increasing research interest in harnessing wind energy for power generation by means of non-conventional electrical machines e.g., flux-reversal machines. The flux reversal machine is usually designed using scarce rare−earth permanent magnet material which may be unattractive in terms of machine cost. In this study, an attempt is made to re-design the flux reversal machine with non-rare-earth ferrite permanent magnet for wind energy applications. Because these machines possess high cogging torque, which results in vibration and noise, that are detrimental to the machine performance, especially at low speeds, a novel combined skewed and circumferential rotor pole pairing method is developed. The proposed cogging torque reduction method is implemented in 2-dimensional finite element analysis modeling and comparatively analyzed with other existing stand-alone methods viz., skewing, and rotor pole pairing. The results show that the proposed method led to 94.8% and 71% r... [more]

A lot of autonomous power systems have been designed and operated with different power levels and with special requirements for climatic conditions, availability, operation/maintenance cost, fuel consumption, environmental impacts, etc. In this paper a novel design of an autonomous power system with photovoltaic panels and electrochemical batteries for a shoreline electrode station is analyzed. This station will be constructed on the small island of Stachtoroi for the new high voltage direct current (HVDC) link of Attica−Crete in Greece. The general guidelines of the International Council on Large Electric Systems (CIGRE) and of the International Electrotechnical Committee (IEC) for the power system of lighting and auxiliary loads for these HVDC stations are supplied from the medium voltage or the low voltage distribution network, whereas they do not take into account the criticality of this interconnection, which will practically be the unique power facility of Crete island. The signi... [more]

In this study, the characteristics of the double quench and instantaneous power of a superconducting fault current limiter (SFCL) using two magnetically coupled windings were analyzed. In the proposed model of SFCL, two magnetically coupled windings are wound on the iron core and each winding is connected to one superconducting element. When a fault occurs, the SFCL can limit the fault current by the double quench occurrence of two superconducting elements. In order to analyze the influence of the winding direction on the fault current limiting characteristics of the proposed SFCL, two magnetically coupled windings were designed to allow the same and the reverse directions. From the simulated short circuit experiment, the currents and the voltages of two coupled windings and two superconducting elements were measured and the instantaneous power and the double quench occurrence were analyzed. It was confirmed from the experimental results analysis that the fault current limiting charact... [more]

The current lighting solutions, both in terms of design process and later implementation, are becoming more and more intelligent. It mainly arises from higher opportunities to use information technology (IT) processes for these purposes. Designs cover many aspects, from physiological to including technical. The paper describes the problems faced by any designers while creating, evaluating them, and presenting the final results of their work in a visualisation form. Development of virtual reality (VR) technology and augmented reality, which is now taking place before our eyes, makes us inclined to think how to use this reality in lighting technology. The article presents some examples of applying VR technology in various types of smart lighting designs, for interiors and outdoor objects. The performed computer simulations are compared to reality. Some surveys, in terms of visualization rendering, were carried out. In the article, the current capabilities and main limitations of virtual... [more]

Alternative energy generated from people’s footsteps in a crowded area is sufficient to power smart electronic devices with low consumption. This paper aims to present the development of an energy harvesting floor—called Genpath—using a rotational electromagnetic (EM) technique to generate electricity from human footsteps. The dynamic models of the electro-mechanical systems were developed using MATLAB®/Simulink to predict the energy performances of Genpath and help fine-tune the design parameters. The system in Genpath comprises two main parts: the EM generator and the Power Management and Storage (PMS) circuit. For the EM generator, the conversion mechanism for linear translation to rotation was designed by using the rack-pinion and lead-screw mechanism. Based on the simulation analysis, the averaged energy of the lead-screw model is greater than that of the rack-pinion model. Thus, prototype-II of Genpath with 12-V-DC generator, lead-screw mechanism was recently built. It shows bett... [more]

This work provides an investigation based on a fast estimation of the degree of unbalance (D.U.%) and the differential leakage factor (σ0) of multiphase electrical machine windings. This analysis is carried out by exploring almost 5000 combinations in terms of number of slots, pole pairs, phases and layers. The variability of the leakage factor is examined for each condition, defining an optimal region for its minimization. As a result, an extended mapping is carried out for both the degree of unbalance and the leakage factor, providing a useful tool during the early design stage of winding configurations for multiphase electric machines, even with slight asymmetries. The results obtained from this investigation are validated through finite element analysis and demonstrate that the differential leakage factor can be significantly reduced by adopting winding configurations with slight asymmetries, which also represent a valuable alternative in the electrical machine design.

In this study, a conceptual design was developed for a lead-bismuth-cooled small modular fast reactor SPARK-NC with natural circulation and load following capabilities. The nominal rated power was set to 10 MWe, and the power can be manipulated from 5 MWe to 10 MWe during the whole core lifetime. The core of the SPARK-NC can be operated for eight effective full power years (EFPYs) without refueling. The core neutronics and thermal-hydraulics design calculations were performed using the SARAX code and the natural circulation capability of the SPARK-NC was investigated by employing the energy conservation equation, pressure drop equation and quasi-static reactivity balance equation. In order to flatten the radial power distribution, three radial zones were constructed by employing different fuel enrichments and fuel pin diameters. To provide an adequate shutdown margin, two independent systems, i.e., a control system and a scram system, were introduced in the core. The control assemblies... [more]

The implementation of a three-dimensional viscous inverse design used for an axial compressor is introduced in this paper. The derivation process of the inverse design algorithm is also described in detail. Moreover, an improved blade update method and a modified relaxation factor are included to enhance the inverse design algorithm. The inverse design is built on an in-house inverse design module coupled with commercial Computational Fluid Dynamic (CFD) software NUMECATM. In contrast to analysis design, the pressure loading and the normal thickness distribution along the blade surfaces are prescribed during the process of inverse design. The numerical methods used to solve the flow field are verified using the experimental data of the transonic fan rotor NASA Rotor 67. A recovery test for the Rotor 67 is carried out to validate the developed three-dimensional inverse design tool. To explore the potential application of the inverse design system, it is then used to improve the aerodyna... [more]

A concentric annular heat pipe heat sink (AHPHS) was proposed and fabricated to investigate its thermal behavior. The present AHPHS consists of two concentric pipes of different diameters, which create vacuumed annular vapor space. The main advantage of the AHPHS as a heat sink is that it can largely increase the heat transfer area for cooling compared to conventional heat pipes. In the current AHPHS, condensation takes place along the whole annular space from the certain heating area as the evaporator section. Therefore, the whole inner space of the AHPHS except the heating area can be considered the condenser. In the present study, AHPHSs of different diameters were fabricated and studied experimentally. Basic studies were carried out with a 50 mm-long stainless steel AHPHS with diameter ratios of 1.1 and 1.3 and the same inner tube diameter of 76 mm. Several experimental parameters such as volume fractions of 10−70%, different air flow velocity, flow configurations, and 10−50 W heat... [more]

Types of tapered piles are widely applied in tank foundation consolidation, but their inherent deficiencies in design and construction limit their further promotion. Vortex compression pile is a novel nodular pile. Compared with the traditional equal-section pile, vortex compression nodular pile is featured by stronger bearing capacity and slighter settlement. In this paper, the model test results showed that vortex compression nodular pile can greatly improve the bearing capacity and reduce the settlement. Through the finite element software ABAQUS analysis the bearing characteristics of equal-section pile foundation and vortex-compression nodular pile foundation were compared. The three-dimensional solid model was established by ABAQUS finite element software. The impact of cushion modulus, cushion thickness, vertical load, pile modulus, soil modulus around the pile on the bearing capacity of the vortex-compression nodular pile foundation were studied.