Two experimental simulations of underground coal gasification (UCG) processes, using large bulk samples of lignites, were conducted in a surface laboratory setup. Two different lignite samples were used for the oxygen-blown experiments, i.e., “Velenje” meta-lignite (Slovenia) and “Oltenia” ortho-lignite (Romania). The average moisture content of the samples was 31.6wt.% and 45.6wt.% for the Velenje and Oltenia samples, respectively. The main aim of the study was to assess the suitability of the tested lignites for the underground coal gasification process. The gas composition and its production rates, as well as the temperatures in the artificial seams, were continuously monitored during the experiments. The average calorific value of gas produced during the Velenje lignite experiment (6.4 MJ/Nm3) was much higher compared to the result obtained for the experiment with Oltenia lignite (4.8 MJ/Nm3). The Velenje lignite test was also characterized by significantly higher energy efficiency... [more]

An intelligent control strategy is proposed in this paper which suggests the Optimum Power Quality Enhancement (OPQE) of grid-connected hybrid power systems with solar photovoltaic, wind turbines, and battery storage. Unified Power Quality Conditioner with Active and Reactive power (UPQC-PQ) is designed with Atom Search Optimization (ASO) based Fractional-order Proportional Integral Derivative (FOPID) controller in the proposed Hybrid Renewable Energy Sources (HRES) system. The main aim is to regulate voltage while reducing power loss and reducing Total Harmonic Distortion (THD). UPQC-PQ is used to mitigate the Power Quality (PQ) problems such as sag, swell, interruptions, real power, reactive power and THD reductions related to voltage/current by using ASO based FOPID controller. The developed technique is demonstrated in various modes: simultaneous to improve PQ reinforcement and RES power injection, PRES > 0, PRES = 0. The results are then compared to those obtained using previous l... [more]

These days, various national and international research organizations are working on the development of low NOx combustors. The present work describes the experimental and numerical characterization of flow dynamics and combustion characteristics in a rectangular burner. A ring-needle type plasma actuator was developed and driven by a high voltage nanosecond pulsed generator under atmospheric conditions. Smoke flow visualizations and Proper Orthogonal Decomposition (POD) were carried out to identify the relevant flow structures. Electrical characterization of the non-reactive flow was carried out to predict the electrical power and the optimum value of the reduced electric field (EN), which is useful for the implementation of a numerical model for the study of plasma-assisted ignition. A detailed plasma kinetic mechanism integrated with all excited species was considered and validated with experimental studies. Numerical modeling of plasma ignition has been performed by coupling ZDPlas... [more]

Process planning in manufacturing today focuses on optimizing the conflicting targets of cost, quality, and time. Due to increasing social awareness and subsequent governmental regulation, environmental impact becomes a fourth major aspect. Eventually, sustainability in manufacturing ensures future competitiveness. In this paper, a framework for the planning of sustainable manufacturing is proposed. It is based on the abstraction and generalization of manufacturing resources and part descriptions, which are matched and ranked using a multi-criteria decision analysis method. Manufacturing resources provide values for cost, quality, time and environmental impacts, which multiply with their usage within a manufacturing task for a specific part. The framework is validated with a detailed modeling of a laser machine as a resource revealing benefits and optimization potential of the underlying data model. Finally, the framework is applied to a use case of a flange part with two different man... [more]

Entrepreneurs have long been convinced about the power and possibilities of the Internet. Nowadays, the Internet is an integral tool for the functioning of a company, not only as an alternative distribution channel, but also as a channel of information and communication flow, a means of interaction with the environment. The increasing use of the Internet, and especially of social media, made it possible to escalate the activity of various social groups in various areas of the company’s activity, including innovation, leading to the development of crowdsourcing. Crowdsourcing has redefined the existing production rules and ways of using labor resources. Its potential lies in openness, partnership, resource sharing and global action. There are already many studies on crowdsourcing and innovation, but little attention is paid to the relationship between crowdsourcing and the determinants of innovation activity. Thus, the aim of this research is examining whether the use of crowdsourcing w... [more]

Chlorine demand as a disinfectant for water utility impacts on unintended energy consumption from electrolysis manufacture; thus, diminishing the chlorine consumption also reduces the environmental impact and energy consumption. Problems of disinfectant distribution and uniformity in Water Distribution Networks (WDN) are associated with the exponential urban growth and the physical and biochemical difficulties within the network. This study optimizes Chlorine Booster Stations (CBS) location on a network with two main objectives; (1) to deliver minimal Free Residual Chlorine (FRC) throughout all demand nodes according to country regulations, and (2) to reduce day chlorine mass concentration supplied in the system by applying an hour time pattern in CBS, consequently associated economic, energy and environmental impacts complying with regulatory standards. The application is demonstrated on a real-world WDN modeled from Guanajuato, Mexico. The resulting optimal location and disinfectant... [more]

Wheel flat can cause a large impact between the wheel and rail and excites a forced vibration in the locomotive and track structure systems. The working conditions and fatigue life of the motor bearings are significantly affected by the intensified wheel−rail interaction via the transmission path of the gear mesh. In this study, a fatigue life prediction method of the traction motor bearings in a locomotive is proposed. Based on the L−P theory or ISO 281 combined with the Miner linear damage theory and vehicle−track coupled dynamics, the irregular loads induced by the track random irregularity and gear mesh are considered in this proposed method. It can greatly increase the accuracy of predictions compared with the traditional prediction models of a rolling bearing life whose bearing loads are assumed to be constant. The results indicate that the periodic impact forces and larger mesh forces caused by the wheel flat will reduce the fatigue life of the motor bearings, especially when th... [more]

Lightning discharge becomes a serious source of interference and damage for electronic and electrical power systems. Safe and reliable operation of railway traffic control systems requires proper protection against the effects of lightning. However, the current standards on lightning protection, PN-EN/EN/IEC 62305, do not cover railway objects. Moreover, there are no other standards or recommendations dedicated to the railway. The paper is an attempt to apply the procedure of lightning risk management according to PN-EN 62305-2 to select the proper protection measures in railway objects. A case study for the signal box with installed relaying and digital stations of the railway traffic control system is analyzed. The analysis comprises calculations based on the current standard PN-EN 62305-2:2012 but including the issues specific to railway traffic control. The risks of lightning losses have been calculated for two cases: without lightning protection measures and with protection measur... [more]

Several carbon sequestration technologies have been proposed to utilize carbon dioxide (CO2) to produce energy and chemical compounds. However, feasible technologies have not been adopted due to the low efficiency conversion rate and high-energy requirements. Process intensification increases the process productivity and efficiency by combining chemical reactions and separation operations. In this work, we present a model of a chemical-electrochemical cyclical process that can capture carbon dioxide as a bicarbonate salt. The proposed process also produces hydrogen and electrical energy. Carbon capture is enhanced by the reaction at the cathode that displaces the equilibrium into bicarbonate production. Literature data show that the cyclic process can produce stable operation for long times by preserving ionic balance using a suitable ionic membrane that regulates ionic flows between the two half-cells. Numerical simulations have validated the proof of concept. The proposed process cou... [more]

Climate change has a major impact on the urban built environment, both with respect to the heating and cooling energy requirements, but also regarding the higher probability of confronting extreme events such as heatwaves. In parallel, the ongoing urbanization, the urban microclimate and the formation of the urban heat island effect, compounding the ongoing climate change, is also a considerable determinant of the building’s energy behavior and the outdoor thermal environment. To evaluate the magnitude of the complex phenomenon, the current research investigates the effect of climate change and urban heat island on heating and cooling energy needs of an urban building unit in Thessaloniki, Greece. The study comparatively evaluates different tools for the generation of future weather datasets, considering both statistical and dynamical downscaling methods, with the latter involving the use of a regional climate model. Based on the output of the regional climate model, another future wea... [more]

In the quest to achieve sustainable pipeline operations and improve pipeline safety, effective corrosion control and improved maintenance paradigms are required. For underground pipelines, external corrosion prevention mechanisms include either a pipeline coating or impressed current cathodic protection (ICCP). For extensive pipeline networks, time-based preventative maintenance of ICCP units can degrade the CP system’s integrity between maintenance intervals since it can result in an undetected loss of CP (forced corrosion) or excessive supply of CP (pipeline wrapping disbondment). A conformance evaluation determines the CP system effectiveness to the CP pipe potentials criteria in the NACE SP0169-2013 CP standard for steel pipelines (as per intervals specified in the 49 CFR Part 192 statute). This paper presents a predictive maintenance framework based on the core function of the ICCP system (i.e., regulating the CP pipe potential according to the NACE SP0169-2013 operating window).... [more]

The further development of electric mobility requires major scientific efforts to obtain reliable data for vehicle and drive development. Practical experience has repeatedly shown that vehicle data sheets do not contain realistic consumption and range figures. Since the fear of low range is a significant obstacle to the acceptance of electric mobility, a reliable database can provide developers with additional insights and create confidence among vehicle users. This study presents a detailed, yet easy-to-implement and modular physical model for both passenger and commercial battery electric vehicles. The model takes consumption-relevant parameters, such as seasonal influences, terrain character, and driving behavior, into account. Without any a posteriori parameter adjustments, an excellent agreement with known field data and other experimental observations is achieved. This validation conveys much credibility to model predictions regarding the real-world impact on energy consumption a... [more]

The reference characteristics of complex permittivity of the transformers insulation solid component were determined for use in the precise diagnostics of the power transformers insulation state. The solid component is a composite of cellulose, insulating oil and water nanoparticles. Measurements were made in the frequency range from 10−4 Hz to 5000 Hz at temperatures from 293.15 to 333.15 K. Uncertainty of temperature measurements was less than ±0.01 K. Pressboard impregnated with insulating oil with a water content of (5.0 ± 0.2) by weight moistened in a manner maximally similar to the moistening process in power transformers was investigated. It was found that there are two stages of changes in permittivity and imaginary permittivity components, occurring for low and high frequency. As the temperature increases, the frequency dependencies of the permittivity and imaginary permittivity component shifts to the higher frequency region. This phenomenon is related to the change of relaxa... [more]

The development of energy from renewable sources is one of the most important aspects of today’s energy industry. The level of this development (production of green energy) is determined by the use of a variety of methods, e.g., the methods of multicriteria and multivariate analysis. The effectiveness of these methods is affected by many factors, and one of them is the appearance of non-typical objects (outliers). This paper investigates the effectiveness of selected methods (TOPSIS, VIKOR, VMCM) in terms of computational robustness to outlier objects. The most effective method in this respect (VMCM) is then applied to study the level of development of renewable energy sources in European countries. The presented research provides the opportunity to carry out a dynamic analysis (for selected base years) of the level of energy generation from diverse renewable sources in reference to the adopted patterns and anti-patterns (European countries). The obtained results are discussed, thus co... [more]

Future office buildings are expected to be integrated with energy intensive, inherently DC components such as photovoltaic panels (PV), electric vehicles (EV), LED lighting, and battery storage. This paper conceptualizes the interconnection of these components through a 750 V DC nanogrid as against a conventional three-phase 400 V AC system. The factors influencing the performance of a DC-based nanogrid are identified and a comparative analysis with respect to a conventional AC nanogrid is presented in terms of efficiency, stability, and protection. It is proved how the minimization of grid energy exchange through power management is a vital system design choice. Secondly, the trade-off between stability, protection, and cost for sizing of the DC buffer capacitors is explored. The transient system response to different fault conditions for both AC and DC nanogrid is investigated. Finally the differences between the two systems in terms of various safety aspects are highlighted.

Efforts to increase the power output of wind turbines include Diffuser Augmented Wind Turbines (DAWT) or a shroud for the rotor of a wind turbine. The selected duct has three main components: a nozzle, a diffuser, and a flange. The combined effect of these components results in enriched upstream velocity for the rotor installed in the throat of the duct. To obtain the maximum velocity in the throat of the duct, the optimum angles of the three parts have been analyzed. A code was developed to allow all the numerical steps including changing the geometries, generating the meshes, and setting up the numerical solver simultaneously. Finally, the optimum geometry of the duct has been established that allows a doubling of the flow velocity. The flow characteristics inside the duct have also been analyzed in detail. An H-Darrieus Vertical Axis Wind Turbine (VAWT) has been simulated inside the optimized duct. The results show that the power coefficient of the DAWT can be enhanced up to 2.9 tim... [more]

Opening deeper coal seams requires constructing underground mine roadways in difficult geological conditions. Supporting of such roadways is subjected to a very high load from the rock mass. The types of roof supports used so far do not provide immediate support for the rock mass, which tends to converge the roadway, allowing for a rapid build-up of stresses in the surrounding rock mass. The article presents a new type of frame roadway support. This is a yielding support (consecutive arches are connected in a helical pattern), enabling the successive arches to be provided with initial load-bearing capacity already at the construction stage. The so-called unscrewing of the helix enables the arches to be pressed against the surface of the developed roadway with a controlled force. The introduction discusses the types of yielding roof supports used in the Polish mining industry and indicates their characteristic features. Further along in the article, the assumptions adopted for the const... [more]

Ignition delay times of small alkenes are a valuable constraint for the refinement of the core kinetic mechanism of hydrocarbons used in representing combustion properties of real fuels. Moreover, the chemical reactivity comparison of those small alkenes provides a reference in object-oriented fuel design and logical combustion utilization. In this study, the ignition delay times of C2−C4 alkenes (ethylene, propene and 1-butene) were measured behind reflected shock waves first, with a fixed oxygen concentration (XO2 = 6%) and equivalence ratio (φ = 1.0) at various pressures of 1.2, 4.0 and 16.0 atm, in order to facilitate the comparison. Three chemical-based-Arrhenius-type correlations covering a wide range of temperature, pressure, equivalence ratio, and dilution were proposed. The simplified reaction network for pyrolysis and oxidation of 1-alkenes was depicted relying on the reaction classes of alkenes. Nine generally accepted mechanisms were used to simulate the ignition delay time... [more]

In this paper, primary and secondary emissions in wind power plants are studied by using transfer admittance and current transfer functions between turbines and the public grid. The use of such transfer functions allows harmonic propagation studies without knowledge of the emission from individual turbines or the background voltage distortion. The transfer functions are calculated for one synthetic and one existing wind power plant, and results are discussed. Primary emission, secondary emission from other turbines and secondary emission from the public grid are shown to be of the same order of magnitude. Furthermore, the paper addresses the impact of turbine converter modelling, public grid impedance and the change in the aggregation exponent with frequency on the propagation. All three are shown to have a significant impact and should be considered. The main challenge for future studies is in obtaining relevant models for turbine impedance versus frequency.

This study concerns the use of the critical chain method to schedule the construction of renewable energy facilities. The critical chain method is recognized as a useful project management tool, transforming a stochastic problem of uncertainty in activity durations into a deterministic one. However, this method has some shortcomings. There are no clear principles of grouping non-critical activities into feeding chains. Another ambiguity is sizing the feeding buffers with regard to the topology of the network model and the resulting dependencies between activities, located in different chains. As a result, it is often necessary to arbitrarily adjust the calculated sizes of feeding buffers before inserting them into the schedule. The authors present the new approach to sizing the time buffers in the schedule, enabling a quick assessment of the quality of a given solution variant and finding a solution that best meets the established criteria, conditions, and constraints. The essence of t... [more]

In this review, the concept of a hybrid solar cell system, called all-weather solar cells, a new view on energy harvesting device design, is introduced and described in detail. Additionally, some critical economical, technological, and ecological aspects are discussed. Due to drastic global climate changes, traditional energy harvesting devices relying only on solar energy are becoming less adaptive, hence the need for redesigning photovoltaic systems. In this work, alternative energy harvesting technologies, such as piezoelectric and triboelectric devices, and photoelectron storage, that can be used widely as supporting systems to traditional photovoltaic systems are analysed in detail, based on the available literature. Finally, some examples of all-weather solar cells composed of dye-sensitized solar cells (DSSC) and silicon solar cells, often modified with graphene oxide or phosphors materials, as new perspective trends in nanotechnology are presented. Two types of solar cell trigg... [more]

The integration of the European markets has started with the successful coupling of spot markets (day-ahead and intra-day) and is expected to continue with the coupling of balancing markets. In this paper, the optimization model for the activation of manual frequency restoration reserve (mFRR) is presented. The model incorporates all order types agreed among the European transmission system operators (TSOs) to be included in the Manually Activated Reserves Initiative (MARI) project. Additionally, the model incorporates the buying curve (demand) of mFRR with the possible tolerance band defined by the TSOs, order clearing constraints and the cross-zonal capacity (CZC) constraints, forming a mixed integer linear programming model. The methodology employs two distinct steps: In the first step, an order conversion process is employed for the markets applying the central-scheduling scheme, and in the second step, the mFRR activation process is executed by solving the presented model. The who... [more]

This study investigates the impact behaviour and post-impact performance of polyamide-6 glass fibre reinforced composites, manufactured by thermoplastic resin transfer moulding. Impact test samples were extracted from quasi-isotropic laminates using two different glass fibre sizings, both with a fibre volume fraction of approximately 52%. A previous study showed that one of these sizings enhanced the interfacial strength and Mode I fracture toughness; however, the effects of the sizing on out-of-plane impact is of greater significance in terms of automotive applications. A drop-weight impact tester was used to determine out-of-plane impact performance for both sizings in terms of impact load-induced and energy returned from the striker. High-speed video of the impact response was simultaneously captured. Testing was carried out at three impact energy levels: two sub-penetration and one full penetration. The impact damage area was observed, and the post-damage compression properties of... [more]

The aims of this paper are to develop hybrid energy systems considering biomass energy sources as well as a framework and optimal configuration of hybrid systems of energy for a southern sub-urban area of Bhola district in Bangladesh, named Kukri Mukri island, and analyse the feasibility of the techno-economic prospects of these systems. In this work, electrification for the rural area is analysed for different configurations of the hybrid systems. The estimation of available resources with optimal sizing and analysis of techno-economic aspects is done through HOMER Pro software to satisfy the demand of peak load. Different configurations of hybrid energy systems, including PV/diesel, PV/wind, PV/diesel/wind, PV/wind/diesel/biomass, and wind/diesel, are analysed and compared through optimization of different energy sources in HOMER. The size of the system and components are optimized and designed depending on the net present cost (NPC) and the levelized cost of energy (LCOE). Due to th... [more]

Although traffic crashes are the eighth leading cause of death in the world, and are linked to vehicle and infrastructure-related factors, crash-related fatality rates are much higher in low-income countries. Particularly, the Dominican Republic is the country with the highest accident rate in the whole American continent. Therefore, in the past few years, public agencies have been developing different measures aimed at reducing traffic fatalities, including road safety campaigns. The aim of the present study was to assess the recalling of such campaigns among the Dominican population, which may serve as an additional indicator to evaluate their effectiveness in this and other countries of the region presenting similar traffic safety issues. For this cross-sectional study, a nationwide sample composed of 1260 people (50% males and 50% females) with a mean age of 39.3 years was used. The data were collected through personal interviews. Overall, the recall of traffic safety campaigns was... [more]