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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 The combined production of electricity, heat and cold by a polygeneration system connected to a district heating and cooling network can provide high energy utilization efficiency. The inherent complexity of simultaneous production of different services and the high variability in the energy demand make combined cooling and heating systems performance highly dependent on the operational strategy. In this paper, an operational optimization method based on the moving average of real-time measurements of energy demands and ambient conditions is proposed. Real energy demand data from a district heating and cooling network close to Barcelona, Spain, are used to test the method. A complex polygeneration system is considered, consisting of an internal combustion engine, a double-effect absorption chiller, an electric chiller, a boiler and a cooling tower. A detailed modelling of the system is provided, considering partial load behavior of the components and ambient conditions effects. Results of the real-time optimal management are discussed and compared to traditional operational strategies and to the ideal optimal management achievable with perfectly accurate forecast of energy demands. Moreover, the optimal width of the window adopted for the moving average of real-time data is identified.

Abstract The sustainable indicators are characterized by a low degree of aggregation and a high amount of information. An indicator must show a synthetic representation of a real environmental, by using a value or a parameter, so that they can be easily used by policy makers. It is necessary to connect, therefore, the various systems in an appropriately integrated sustainable system. The indicators need to be aggregated based on the structure of the data. Each indicator must to be defined through a weight with reference to another weighted indicator. In this paper is illustrated the calculation of the assigned weights that uses a procedure based on fuzzy logic and to define a model that allows us to estimate the sustainability of a city. The final result is, therefore, a combination of values assigned by expert opinion for the various criteria, processed using fuzzy logic to obtain a weight with significant objectivity and as it is possible to estimate the sustainability of the city through the weights.

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.

The possibility of artificially inducing activation of MII buffalo oocytes may allow us to evaluate indirectly the quality of oocytes after in vitro maturation. The aim of this work was to compare buffalo embryo development after IVF and after chemical activation by two different agents. A further goal was to evaluate the effects of aging of oocytes on post-parthenogenetic and post-fertilization development. In Experiment 1 cumulus-oocyte complexes (COCs) were recovered from abattoir-derived ovaries and matured in vitro. After IVM the COCs were either fertilized in vitro (positive control) or activated with ethanol and ionomycin, both followed by immediate exposure to 6-diethylaminopurine (6-DMAP) for 4 h. In vitro culture (IVC) was carried out up to the blastocyst stage. In Experiment 2 COCs were matured in vitro for 18, 21, 24, 27 and 30 h before activation was triggered with ethanol, followed by 6-DMAP. In Experiment 3 COCs were fertilized in vitro at 18, 21, 24, 27 and 30 h post-maturation. Ethanol activation gave better results than the IVF control group, with higher cleavage rate (71.4 +/- 7.8 versus 55.8 +/- 5.8, respectively; P < 0.05) and a higher proportion of oocytes developing into morulae-blastocysts (32.6 +/- 6.5 versus 22.9 +/- 7.5, respectively; P < 0.05). Within the activation groups, ethanol supported the highest development in terms of cleavage (71.4 +/- 7.8 versus 59.4 +/- 10.7; P < 0.05) and morulae-blastocysts rate (32.6 +/- 6.5 versus 25.7 +/- 8.3; n.s.). It was also demonstrated that aging negatively affects post-parthenogenetic and post-fertilization development.

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.

Abstract This paper investigates two transition initiatives at the local level – namely the reconversion of the Porto Marghera and Gela refineries into biorefineries for second-generation biofuels. The study aimed at assessing the extent to which the narrative pressures exerted by local actors influenced the perspectives of key stakeholders involved in these transition processes. To this end, a blended methodology was employed, combining discourse analysis with stakeholder analysis and semi-structured interviews. First, stakeholders were grouped into four categories according to the source (national/global) and channel (formal/informal) of pressure. National/informal actors emerged as the most influential group. The discourse analysis identified three dominant storylines representing complementary trajectories defined by national actors operating through informal channels. Finally, semi-structured interviews with key local actors involved in the Porto Marghera and Gela reconversions were used to assess the impact of these storylines in the reconversion processes. Comparison of the two cases revealed fundamental specificities related to their respective cultural, political and socio-economic contexts. While the Porto Marghera reconversion was presented as a consolidated success story (albeit with a number of drawbacks related to the fact that it was still mainly powered by first-generation feedstocks), the Gela case was viewed as a complex and challenging ongoing process with an uncertain outcome.

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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.

Abstract In recent years, distributed energy systems (DESs) have been recognized as a promising option for sustainable development of future energy systems, and their application has increased rapidly with supportive policies and financial incentives. With growing concerns on global warming and depletion of fossil fuels, design optimization of DESs through economic assessments for short-run benefits only is not sufficient, while application of exergy principles can improve the efficiency in energy resource use for long-run sustainability of energy supply. The innovation of this paper is to investigate exergy in DES design to attain rational use of energy resources including renewables by considering energy qualities of supply and demand. By using low-temperature sources for low-quality thermal demand, the waste of high-quality energy can be reduced, and the overall exergy efficiency can be increased. The goal of the design optimization problem is to determine types, numbers and sizes of energy devices in DESs to reduce the total annual cost and increase the overall exergy efficiency. Based on a pre-established DES superstructure with multiple energy devices such as combined heat and power and PV, a multi-objective linear problem is formulated. In modeling of energy devices, the novelty is that the entire available size ranges and the variation of their efficiencies, capital and operation and maintenance costs with sizes are considered. The operation of energy devices is modeled based on previous work on DES operation optimization. By minimizing a weighted sum of the total annual cost and primary exergy input, the problem is solved by branch-and-cut. Numerical results show that the Pareto frontier provides good balancing solutions for planners based on economic and sustainability priorities. The total annual cost and primary exergy input of DESs with optimized configurations are reduced by 21–36% as compared with conventional energy supply systems, where grid power is used for the electricity demand, and gas-fired boilers and electric chillers fed by grid power for thermal demand. A sensitivity analysis is also carried out to analyze the influence of energy prices and energy demand variation on the optimized DES configurations.