The Water Cooled Lithium Lead (WCLL) breeding blanket is one of the driver blanket concepts under development for the European Demonstration Reactor (DEMO). The majority of the blanket volume is occupied by flowing PbLi at eutectic composition. This liquid metal flow is subdued to high fluxes of particles coming from the plasma which are translated into a high non-homogeneous heat volumetric source inside the fluid. The heat is removed from the PbLi thanks to several water tubes immersed in the metal. The dynamics of the PbLi is heavily affected by the heat source and by the position of the tubes. Moreover, the conducting fluid is electrically coupled with the intense magnetic field used for the plasma confinement. As a result, the PbLi flow is strongly affected by the Magnetohydrodynamics (MHD) forces. In the WCLL, the MHD and convective interactions are expected to be comparable. Therefore, the PbLi dynamics and consequently the heat transfer between the liquid metal and the water co... [more]

The performance gap, defined as the difference between the measured and the calculated performance of energy-efficient buildings, has long been identified as a major issue in the building domain. The present study aims to better understand the performance gap in high-energy performance buildings in Switzerland, in an ex-post evaluation. For an energy-efficient building, the measured heating demand, collected through a four-year measurement campaign was compared to the calculated one and the results showed that the latter underestimates the real heating demand by a factor of two. As a way to reduce the performance gap, a probabilistic framework was proposed so that the different uncertainties of the model could be considered. By comparing the mean of the probabilistic heating demand to the measured one, it was shown that the performance gap was between 20−30% for the examined period. Through a sensitivity analysis, the active air flow and the shading factor were identified as the most i... [more]

Since conventional lightning protection measures do not effectively extinguish subsequent arcs of electrical frequency after the passage of lightning, it is impossible to prevent lightning-related accidents on the distribution lines. To solve this problem, a 10 kV multi-chamber arc-quenching arrester (MCAA) applicable to transmission lines of different voltage levels is developed. In order to research the arc-quenching characteristics of the MCAA, COMSOL software was used to simulate and analyze the high-speed airflow coupled arc process. Under the action of a strong airflow at high speed, the arc is segmented, the temperature of the arc falls sharply, and eventually, the arc is extinguished. In the simulation process, the conductivity of the arc and the clouds of change of air speed were achieved. It may be concluded that arc segmentation time and airflow generation time are at a subtle level. Meanwhile, an experimental circuit was established to conduct the arc-quenching experiment.... [more]

The impeller backside cavity (IBC) is a unique structure of centrifugal compressor in compressed air energy storage (CAES) systems, which affects the aerodynamic performance of centrifugal compressor, and the angle change of the downstream coupled adjustable vaned diffusers (AVDs) will affect the flow field inside the cavity and compressor performance. This paper relies on the closed test facility of the high-power intercooling compressor to measure static pressure and static temperature at different radii on the static wall of the IBC. The coupling relationship between the IBC and compressor under variable operating conditions is analyzed, and the influence of AVDs on the internal flow in IBC is studied. The results show that static pressure and static temperature rise along the direction of increasing radius, but static temperature drops near the coupling between the impeller outlet and the cavity inlet. Under AVDs’ design angle, static pressure and static temperature at each point,... [more]

The aim of this study is to highlight the need for sustainable urban development by reviewing the different Indicator Systems (SI) and contrasting them with those factors that have had a correlation in the spread of the virus in order to detect its deficiencies. This research carries out an urban diagnosis and analyzes the influence of these factors in order to detect deficiencies and propose a new IS adapted to current needs. Lastly, the new SI is validated through its practical application in one of the Autonomous Communities most affected by the pandemic in Spain. It is concluded that most of the factors causing a worse incidence of the virus are hardly evaluated by the existing IS. The practical analysis shows that there are deficiencies in urban design, resulting in poor environmental quality and urban morphology.

This review presents the current state of the knowledge regarding the use of radioactive sources to generate photonic light in scintillators as converters of ionizing radiation to electricity in photovoltaic cells. The possibility of using the phenomenon of the excitation of light photons in the scintillation materials during the interaction with particles and photons of ionizing radiation was analyzed in detail. The light photons obtained in such a way can generate an electric charge in photovoltaic cells. The whole process can be named as a nuclear cell (nuclear battery). Theoretically, the use of such physical phenomena seems to be an ideal practical solution to meet the energy needs of the modern world. However, there are many physical and technical problems that limit its widespread use in practical applications. In an ideal system, the ionizing radiation sources can emit the radiation for billions of years, and the energy of particles and photons from the radiation can be convert... [more]

Failure behavior of pillars in deep mines is affected by various cyclic loads that cause initial pre-damage. Pillars will be further damaged and developed in the long-term compressive stress until they are destroyed. To reveal the strength characteristics and crack damage fracture laws after rock pre-damage, uniaxial compression tests were carried out on granite specimens damaged by cyclic loading using the digital speckle correlation method. The experimental results indicate that the mechanical properties of pre-damaged specimens show large damage differences for different cycles. The damage variable of the pre-damaged specimens increases with the increase of cycle number and confining pressure. The damage of specimens is primarily due to the strength weakening effect caused by cycle numbers, and the confining pressure restriction effect is not obvious. The evolution laws of uniaxial compression damage propagation in the pre-damaged specimens show differences and obvious localization... [more]

Energy carried by engine exhaust pulses is critical to the performance of a turbine or any other exhaust energy recovery system. Enthalpy and exergy are commonly used concepts to describe the energy transport by the flow based on the first and second laws of thermodynamics. However, in order to investigate the crank-angle-resolved exhaust flow enthalpy and exergy, the significance of the flow parameters (pressure, velocity, and temperature) and their demand for high resolution need to be ascertained. In this study, local and global sensitivity analyses were performed on a one-dimensional (1D) heavy-duty diesel engine model to quantify the significance of each flow parameter in the determination of exhaust enthalpy and exergy. The effects of parameter sweeps were analyzed by local sensitivity, and Sobol indices from the global sensitivity showed the correlations between each flow parameter and the computed enthalpy and exergy. The analysis indicated that when considering the specific en... [more]

Many public social housing building stocks were constructed before the introduction of national thermal regulations, and, as a result, in some situations, energy poverty conditioning during severe winter seasons results in little to no heating habits involving active systems in order to improve building thermal performances. Besides rigorous summer seasons, climate change predictions also indicate rigorous winter seasons will occur that will prevail in some Iberia Peninsula locations, worsening this scenario for this Southern European region. Among others, understanding the extension of discomfort in social housing buildings during heating seasons is therefore essential so as to perceive the suitability of the building stock to deal with present and future climate scenarios. Thus, this article presents a thermal comfort assessment during a winter season period applied to two social housing dwellings located in Covilhã, Portugal, inhabited by elderly residents, under realistic heating h... [more]

Estimation and correct determination of vitrinite equivalent reflectance in rock is crucial for the assessment of the source rock in both conventional and unconventional hydrocarbon deposits. These parameters can be determined in laboratories on rock samples. Laboratory measurements provide only point information. However, the use of well logs could overcome discontinuities in the data and provide parameters throughout a study interval. Attention has been paid to the estimation of TOC based on well logs. Vitrinite equivalent reflectance estimation is less well discussed and most papers reported cases with high TOC content in analyzed deposits. In this paper, the estimation of improved Ro is presented using a calculated maturity indicator with well logs. As the organic matter content is not high, additional steps were required for the calculation. To improve the quality of the fit and to find similar intervals, the data were grouped using cluster and neural network analysis. The next st... [more]

Usage of phase change materials’ (PCMs) latent heat has been investigated as a promising method for thermal energy storage applications. However, one of the most common disadvantages of using latent heat thermal energy storage (LHTES) is the low thermal conductivity of PCMs. This issue affects the rate of energy storage (charging/discharging) in PCMs. Many researchers have proposed different methods to cope with this problem in thermal energy storage. In this paper, a tubular heat pipe as a super heat conductor to increase the charging/discharging rate was investigated. The temperature of PCM, liquid fraction observations, and charging and discharging rates are reported. Heat pipe effectiveness was defined and used to quantify the relative performance of heat pipe-assisted PCM storage systems. Both experimental and numerical investigations were performed to determine the efficiency of the system in thermal storage enhancement. The proposed system in the charging/discharging process sig... [more]

Results of tests into the energy-efficiency of belt conveyor transportation systems indicate that the energy consumption of their drive mechanisms can be limited by lowering the main resistances in the conveyor. The main component of these resistances is represented by belt indentation rolling resistance. Limiting its value will allow a reduction in the amount of energy consumed by the drive mechanisms. This article presents a test rig which enables uncomplicated evaluations of such rolling resistances. It also presents the results of comparative tests performed for five steel-cord conveyor belts. The tests involved a standard belt, a refurbished belt and three energy-saving belts. As temperature significantly influences the values of belt indentation rolling resistance, the tests were performed in both positive and negative temperatures. The results indicate that when compared with the standard belt, the refurbished and the energy-efficient belts generate higher and lower indentation... [more]

Axial slot casing treatment is a common method to extend the stall margin of a compressor. Based on the mechanism of unsteady flow control, this paper redesigns axial slots with large circumferential interval and small opening area. To test the effect of this axial slot structure, unsteady numerical simulations were carried out with different slot areas and circumferential intervals. The results show that this novel axial slot casing treatment can significantly improve compressor stall margin. Meanwhile, compared with the traditional axial slot, the efficiency loss is greatly reduced. The flow field analysis shows that the new axial slot structure proposed in this paper can suppress the development of tip leakage vortex and unsteadiness in the tip region at the near stall condition through decreasing the tip loading periodically. Moreover, we find that the slot area is proportional to the improvement of stability margin. Under the same slot area, an excessive number of slots is not con... [more]

Natural gas processing requires the removal of acidic gases and dehydration using absorption, mainly conducted in tri-ethylene glycol (TEG). The dehydration process is accompanied by the emission of volatile organic compounds, including BTEX. In our previous work, multi-objective optimization was undertaken to determine the optimal operating conditions in terms of the process parameters that can mitigate BTEX emission using data-driven metamodeling and metaheuristic optimization. Data obtained from a process simulation conducted using the ProMax® process simulator were used to develop a metamodel with machine learning techniques to reduce the computational time of the iterations in a robust process simulation. The metamodels were created using limited samples and some underlying phenomena must therefore be excluded. This introduces the so-called metamodeling uncertainty. Thus, the performance of the resulting optimized process variables may be compromised by the lack of adequately acco... [more]

A tubular reactor based on the disk and doughnut concept was designed as an engineering solution for biogas upgrading via CO2 methanation. CFD (Computational Fluid Dynamics) benchmarks agreed well with experimental and empirical (correlation) data, giving a maximum error of 8.5% and 20% for the chemical reaction and heat transfer models, respectively. Likewise, hot spot position was accurately predicted, with a 5% error. The methodology was used to investigate the effect of two commercially available coolants (thermal oil and molten salts) on overall reactor performance through a parametric study involving four coolant flow rates. Although molten salts did show higher heat transfer coefficients at lower coolant rates, 82% superior, it also increases, by five times, the pumping power. A critical coolant flow rate (3.5 m3/h) was found, which allows both a stable thermal operation and optimum pumping energy consumption. The adopted coolant flow range remains critical to guarantee thermal... [more]

Determining the spatial position of wind turbines is the initial and most important phase in the development of a wind farm project. In this sensitive phase, all potential problems that may arise in the later stages of project development should be prevented by means of spatial and urban planning instruments. This makes it possible to achieve maximum use of the potential of wind in a particular space and, thus, fulfil the technical and economic requirements of the project while respecting the goals of environmental protection in that same area, through preventive protection. Therefore, it is essential, even at the earliest planning and development stage of a wind farm project, for the requirements that are important for optimal spatial solutions to be balanced. In this process, strategic environmental assessment (SEA) is a support to the planning process and an invaluable instrument for finding optimal spatial solutions for the possible key spatial impacts of wind power with regard to... [more]

This contribution focuses on utilizing blended biofuels of rapeseed oil and methanol with diesel. Rapeseed is one of the most cultivated energy crops in Europe, and its purpose in the blends is to increase the bio-content in test fuels. The purpose of methanol in the blends is to increase bio-content and compensate for the higher viscosity of the rapeseed oil. As methanol is almost insoluble in diesel and rapeseed oil, iso-butanol is used as a co-solvent. The fuel blends were tested in volumetric concentrations of diesel/rapeseed oil/methanol/iso-butanol 60/30/5/5, 50/30/10/10, and 50/10/20/20. Diesel was used as a reference. The measurements were performed on a turbocharged diesel engine Zetor 1204, loaded using the power-takeoff shaft of the Zetor Forterra 8641 tractor. In this paper, the effect of the blended fuels on performance parameters, engine efficiency, production of soot particles, and regulated and unregulated emissions are monitored and analyzed. It was found that engine p... [more]

Regarding the modern power smart grid, distribution consumers and prosumers are highly concerned about power quality (PQ). In fact, they would prefer to pay higher prices for a reliable and good quality power supply. Unfortunately, utility operators still aim for reliability alone, ignoring the quality of supply voltage and current. There are no clear guidelines for monitoring, penalizing, or implementing PQ-based tariff schemes in LV distribution systems. In addition, the implementation of a PQ-based tariff requires a real-time measuring mechanism at the user end, which is very expensive and difficult to understand for a domestic consumer. This paper presents a novel, low-cost, efficient, and user-friendly smart PQ meter to overcome these issues and limitations. It is essentially a PQ analyzer with energy metering functionality, which implements a novel PQ-based tariff scheme that penalizes consumers violating the PQ limits and provides incentives for a good PQ profile. It measures as... [more]

The most recent research confirms that airborne transmission may be the dominant mode of SARS-CoV-2 virus spread in the interior spaces of buildings. Consequently, based on some prescriptions that implemented natural ventilation during face-to-face lessons in a university centre, an experimental characterization of several complementary options aimed at reinforcing the prevention and safety of the occupants was carried out. The action protocol adopted was based on the combination of mandatory natural ventilation, a maximum contribution of outdoor air supply in the air conditioning system, and the use of filtering devices located inside the classroom. All the strategies were incorporated concomitantly with necessary compliance with the basic conditions of social distance, occupation, use of masks and guidelines for use and cleaning within educational buildings. The suitability of this protocol was further evaluated throughout the teaching day with students and teachers by measuring the... [more]

The world is moving towards the generation of electricity with renewable energy sources (RES) due to the deterioration of the green environment and trying to replace non-renewable energy resources. The real-time results are achieved with the help of an arm controller, having good controller efficiency with the Waijung toolbox, compatible with MATLAB using STM32ST-link utility. In this paper, the authors are focused on areas such as easy to implement controller efficiency, and real-time solutions for modified direct-control perturbation & observation (DC-P&O) technique based on 32- bit ARM Cortex microcontroller (STM32F407VGT6) with embedded programming using Waijung blocksets, which offers very expected outcomes of the problem to make the stand-alone system efficient with fast-tracking. The observation setup is tested with a 40-watt photovoltaic (PV) panel with resistive load for achieving its stability. The designed algorithm enhances the efficiency of the controller by 84.48% for the... [more]

According to one definition, Smart City is an administrative unit that uses data and digital technology to improve the decision-making processes and well-being of its inhabitants. Smart Cities use modern, intelligent technologies to forecast future changes, optimize city functions, gain a better understanding of current conditions, and deliver solutions. To make the city smart, multiple connected sensors, smartphones and other IoT devices are needed. As part of the research conducted at the Technical University in Vienna, six key dimensions (categories) of smart cities have been identified and characterized: Smart Economy, Smart Mobility, Smart Environment, Smart People, Smart Living, and Smart Governance. The aim of the paper is to present the concept of the smart cities, the implemented innovative solutions and the issue of electricity saving in Smart Cities. The theoretical considerations were expanded of the presentation of selected smart city projects in Polish cities. The conside... [more]

With an increasing capacity of inverter-based generation and with a 100% renewable energy power system on the horizon, grid forming converters have the potential to become the prevalent control mode in the grid. Thus, the correct performance of these devices is going to be crucial for system stability and security of supply. Most research related to the grid-forming control is focused on normal operating conditions, although significant effort has been devoted to current limitation strategies to ensure Low Voltage Ride Through (LVRT) capability. However, most contributions usually consider only balanced faults. This paper, proposes a new current limiting method based on the well-known threshold virtual impedance (TVI) that keeps the voltage source behaviour associated to the grid forming (GFM) capability, even when the current limit is reached, while reducing the voltage unbalance according to user-defined settings.

In order to get rid of the impact of the global financial crisis and actively respond to global climate change, it has become a common choice for global economic development to develop clean energy such as wind energy, improve energy efficiency and reduce greenhouse gas emissions. With the advantages of simple structure, unnecessary facing the wind direction, and unique appearance, the vertical axis wind turbine (VAWT) attracts extensive attention in the field of small and medium wind turbines. The lift-type VAWT exhibits outstanding aerodynamic characteristics at a high tip speed ratio, while the starting characteristics are generally undesirable at a low wind speed; thus, how to improve the starting characteristics of the lift-type VAWT has always been an important issue. In this paper, a lift-drag combined starter (LDCS) suitable for lift-type VAWT was proposed to optimize the starting characteristics of lift-type VAWT. With semi-elliptical drag blades and lift blades equipped on th... [more]

The presented research concerned the phenomenon of polyelectrolyte changes resulting from modification by applying the ultrasonic field. The main aim of this research was to determine the activation degree of this macromolecular chemical compound and its effect on sewage sludge subjected to conditioning and followed by dewatering. The overall goal was to investigate the potential way of reducing the dosage of chemical compounds prior to sewage sludge conditioning. The polyelectrolyte samples were sonicated with the ultrasonic disintegrator UD-20 coupled with a sandwich concentrator. The power output of the generator was 180 W and the ultrasonic field frequency was 22 kHz. To describe the geometrical characteristics of the separated phases, the following parameters were determined: surface area (AA), perimeter (LA) and non-dimensional coefficient. With reference to the obtained results, the most significant quantitative changes in shape and size of the separated phases were observed for... [more]

Magnetorheological (MR) dampers, used as intelligent semi-active vibration control devices to achieve low energy consumption, fast response, controllability, and other capabilities are generally installed with a variety of sensors on their exterior to ensure that the damping force can be accurately controlled. However, external sensors are often affected by external complications that reduce the reliability of the damper, and the cost of powering the damper coils in remote locations where power is not available can be significantly increased. Based on these problems, a new self-powered MR damper scheme is proposed. The proposed MR damper has both energy-harvesting capabilities and damping controllability, and greatly improves the stability and application range of the device by converting vibration energy into electrical energy to supply the excitation coil. The MR damper can drive the piston rod in a linear reciprocating motion by external excitation, which converts mechanical energy... [more]