• Energy Research
• Closed Access close
• Restricted close
• DE close
• CA close
• BE close
• Aurora Universities Network close

Abstract This paper deals with the control of the series FACTS (Flexible AC Transmission Systems) devices for the coordination between their transient stability controller and POD (Power Oscillation Damping) controller in multi-machine power systems. The design aspects and their implementation in form of fuzzy-logic coordination controller are presented. Furthermore, ANFIS (Adaptive Neuro-Fuzzy Inference System) is employed for the training of the proposed fuzzy-logic controller. The local signals of the FACTS devices are applied to achieve the coordination objectives. Digital simulations of multi-machine power system subjected to a wide variety of disturbances validate the efficiency of this approach. The proposed control scheme is not only robust, but also simple and easy to be realized in power systems.

Abstract District heating dynamic models arise as an alternative approach to in-situ experimental investigations. The main advantage of dynamic modeling and simulation is the possibility to avoid technical and operational risks that might occur during in-situ experimental investigations (e.g. heat demand is not met, damages in the energy systems etc.). Within this study, the authors present two models for an existing district heating system in Cottbus, Germany. One model is developed using the tool EBSILON Professional, while the other one is developed using the Simscape toolbox for physical modeling in Matlab/Simulink. The models were experimentally validated against measured data from the considered district heating system. The results show that the Simscape model has a better fit and better response than the EBSILON model. Yet, some discrepancies were found between the measured and the simulated data and, therefore, the uncertainties of the models were addressed. A comparative study between both tools is presented. The EBSILON models permit only unidirectional flow, whereas the Simscape toolbox permits reverse flow. Nevertheless, the EBSILON model outperforms the Simscape model in computation time. In addition, this study presents an approach for dynamic thermo-hydraulic modeling of district heating networks. This approach is utilized to examine the role of district heating networks as heat storage as an optimization configuration. The numerical results show less start-ups for additional heat sources. Yet, higher heat losses from the network are observed due to the installation of unburied pipelines.

Abstract The cathodic electrodeposition of paint on metals proceeds under the influence of an alkalization of the diffusion layer, which is caused by the cathodic reduction of water to yield hydrogen. Three independent electrochemical methods, namely the rotating cone electrode at constant current density, chronopotentiometry and cyclic voltammetry, both at stationary electrodes in stagnant electrolytes, were employed to study the influence of cathodic corrosion of aluminium. It generates initially aluminate as a corrosion product. It was found that the tendency for electrocoagulation is strongly enhanced at Al surfaces in comparison to steel. This is attributed to a higher efficiency due to the in situ formation of intensively dispersed aluminium-oxidhydrate through hydrolysis of the aluminate anions. Thus, the electrocoagulation process is not only an acid/base-reaction with the macro-ions: p - NR 2 H + + A 1 O 2 − → p - NR 2 ↓ + AlOOH ↓, but the presence of AlOOH nuclei improves the formation of a new polymer phase.

AbstractSizing by sifting with screens. Viewed physically, screening comprises superposition of segregation, diffusion, and passage through the screen. Frictional and cohesive forces have to be overcome and the coarse feed material transported over the screen, primarlily by circular, elliptical, or linear vibration. The specific screening performance and the sharpness of separation prove to be a measure for the quality of screening. There are three uses for screening: protective screening with mean particle size Dm ≪ mesh w with a simultaneous wish for high screen performance; classification with Dm ≈ w with a desire for greater sharpness of separation; and dust removal with Dm ≫ w and the problem of deagglomeration, i. e. separation of fines from the screened material. The maximum screen performance can be calculated for the coarse range; it is attainable with most screening machines. A problem encountered in the medium to fine size range is prevention of blinding of the screening machine and deagglomeration of sieved material, with attrition phenomena deserving attention. A range of machines is available: casting, planar, tumble, agitator screening machines are available, as are those with deforming screens, those utilizing centrifugal forces, and, as the latest addition, flow screening. New developments concentrate on fine screening, e. g. screening machines with direct activation of the screen fabric, tumble screening machines, combinations of mechanical and pneumatic screening extending through to pure flow screening. Plastic screens made of polyurethane are of advantage for wet screening; they exhibit greatly reduced wear. Safety requirements are met by silenced and explosion‐proof‐screening machines.

Die vorliegende Studie untersucht Einflusse von acht psychographischen Merkmalen privater Stromkunden auf deren Bereitschaft, Strom aus regenerativen Energiequellen (= Okostrom) nachzufragen. Empirische Grundlage der Arbeit ist eine standardisierte telefonische Befragung von 267 Privatkunden eines Energieversorgers in Deutschland. Die Ergebnisse von mul tivariaten Partial Least Squares Zusammenhangsanalysen deuten generell auf signifikant positive Effekte der allgemeinen Befurwortung von Umweltschutz und der positiven Bewertung eines Okostrombezugs durch Gruppen im personlichen Umfeld von Kunden auf deren Bereitschaft, Okostrom nachzufragen, hin. Speziell bei Kunden mit einem jahrlichen Stromver brauch bis zu 3.000 kWh beeinflusst zudem die Preisgewichtung bei Energiebezugsentscheidungen und die Uberzeugung, dass der eigene Stromversorger auch gesellschaftliches Engagement zeigt, deren Nachfragebereitschaft signifikant positiv. Die Absicht, Okostrom nachzufragen, wird hingegen bei Privatkunden mit einem jahrlichen Stromverbrauch von mindestens 3.900 kWh speziell durch die wahrgenommene Unterschiedlichkeit der Angebote von Energieversorgern beeinflusst. Aus den empirischen Erkenntnissen werden Anregungen fur das Okostrom-Marketing von Energieversorgern und die Kundenverhaltensforschung abgeleitet.

This paper investigates the thermal and fluid dynamic effects of a cold air jet generated by a Ranque-Hilsch vortex tube on the cutting tool of a milling machine. A simulation model that predicts the temperature field and the displacements of the tool due to the thermal effects was developed. Such a model can help to correct machining errors and improve cutting accuracy of air-cooled milling machines. Experimental results validated the model. Eventually, the post-processing of the computational fluid dynamics (CFD) data has been conducted in virtual reality.

In wetlands, a distinct zonation of plant species composition occurs along moisture gradients, due to differential flooding tolerance of the species involved. However, "flooding" comprises two important, distinct stressors (soil oxygen demand [SOD] and partial submergence) that affect plant survival and growth. To investigate how these two flooding stressors affect plant performance, we executed a factorial experiment (water depth x SOD) for six plant species of nutrient-rich and nutrient-poor conditions, occurring along a moisture gradient in Dutch dune slacks. Physiological, growth, and biomass responses to changed oxygen availability were quantified for all species. The responses were consistent with field zonation, but the two stressors affected species differently. Increased SOD increased root oxygen deprivation, as indicated by either raised porosity or increased alcohol dehydrogenase (ADH) activity in roots of flood-intolerant species (Calamagrostis epigejos and Carex arenaria). While SOD affected root functioning, partial submergence tended more to reduce photosynthesis (as shown both by gas exchange and 13C assimilation), leaf dark respiration, 13C partitioning from shoots to roots, and growth of these species. These processes were especially affected if the root oxygen supply was depleted by a combination of flooding and increased SOD. In contrast, the most flood-tolerant species (Juncus subnodulosus and Typha latifolia) were unaffected by any treatment and maintained high internal oxygen concentrations at the shoot : root junction and low root ADH activity in all treatments. For these species, the internal oxygen transport capacity was well in excess of what was needed to maintain aerobic metabolism across all treatments, although there was some evidence for effects of SOD on their nitrogen partitioning (as indicated by 865N values) and photosynthesis. Two species intermediate in flooding tolerance (Carex nigra and Schoenus nigricans) responded more idiosyncratically, with different parameters responding to different treatments. These results show that partial submergence and soil flooding are two very different stressors to which species respond in different ways, and that their effects on physiology, survival, and growth are interactive. Understanding species zonation with water regimes can be improved by a better appreciation of how these factors affect plant metabolism independently and interactively.

Bioelectrochemical systems (BESs) are hybrid systems using electroactive bacteria and solid electrodes, which serve as electron donor or acceptor for microorganisms. When forming a biofilm on the electrode, bacteria secrete extracellular polymeric substances (EPSs). However, EPS excretion of electroactive biofilms in BES has been rarely studied so far. Consequently, the aim of this study is to develop a routine including the electrochemical cultivation, biofilm harvesting, fractionation, and biochemical analysis of the EPS secreted by Geobacter sulfurreducens under electroactive conditions. G. sulfurreducens was cultivated in microbial fuel cell mode on graphite-based electrodes polarized to +400 mV versus Ag/AgCl for 8 d. A maximum current density of 172 ± 29 μA cm-2 was reached after 7 d. The EPS secreted from the biofilms were harvested and fractioned into soluble, loosely bound, and tightly bound EPS and biochemically analyzed. Electroactive cultures secreted significantly more EPSs compared to cells grown under standard heterotrophic conditions (fumarate respiration). With 116 pg per cell, the highest amount of EPSs was measured for the soluble EPS fraction of G. sulfurreducens using anodic respiration, followed by the tightly bound (18 pg cell-1) and loosely bound (11 pg cell-1) fractions of the EPS. Proteins were found to dominate all EPS fractions of the biofilms grown under electrochemical conditions. To the best of the authors' knowledge, these experiments are the first approach toward a complete analysis of the main EPS components of G. sulfurreducens under anode-respiring conditions.