A method of strategic evaluation of energy performance of Building Integrated Photovoltaic in the urban context

This paper presents an integrated bottom-up approach aimed at helping those dealing with strategical analysis of installation of Building Integrated Photo Voltaic (BIPV) to estimate the electricity production potential along with the energy needs of urban buildings at the district scale. On the demand side, hourly energy profiles are generated using dynamic building simulation taking into account actual urban morphologies. On the supply side, electricity generated from the system is predicted considering both the direct and indirect components of solar radiation as well as local climate variables. Python-based Algorithm editor Grasshopper is used to interlink four types of modelling and simulation tools as 1) generation of 3-D model, 2) solar radiation analysis, 3) formatting weather files (TMY data set) and 4) dynamic energy demand. The method has been demonstrated for a cluster of 20 buildings located in the Yasar University in Izmir (Turkey), for which it is found the BIPV system could achieve an annual renewable share of 23%, in line with the Renewable Energy Directive target of 20%. Quantitatively-compared demand and supply information at hourly time step shows that only some energy needs can be met by BIPV, so there is a need for an appropriate matching strategy to better exploit the renewable energy potential

Subfoveal choroidal thickness at age 9 years in relation to clinical and perinatal characteristics in the population-based Generation R Study

Purpose: To assess the association between clinical and perinatal characteristics and subfoveal choroidal thickness in 9-year-old children. Methods: The study included data from the population-based Generation R cohort, whose participants underwent cycloplegic refractometry, ocular biometry, height, weight and subfoveal choroidal thickness measurements using a swept-source optical coherence tomography (SS-OCT) instrument. Birth parameters were obtained using medical records. Statistical analyses were performed using multivariate regression models adjusted for age, ethnicity and sex. Results: A total of 1018 children (52.5% girls, 47.5% boys) with a mean age of 9.9 ± 0.3 years and a mean cycloplegic spherical equivalent refraction of 0.80 ± 1.1 D in boys and 0.81 ± 1.4 in girls were eligible for analysis. The subfoveal choroid was 17 μm thicker in girls (298 ± 60.6 μm) than in boys (281 ± 55.0 μm; p < 0.001), a difference of 9.1 μm persisting after adjustment for age, ethnicity and axial length (p = 0.017). Subfoveal choroidal thickness decreased with increasing ocular axial length (−16.2 μm/mm, 95% CI −21.2 to −12.4, p < 0.001) and with increasing myopic refraction (−10.0 μm/D, 95% CI 6.8–13.1; p < 0.001, adjusted for age, ethnicity, axial length and sex) while it increase

Investigation of the Effect of Different Current Loads on the Arc-Erosion Performance of Electrical Contacts

In this study, arc-erosion experiments using contactors were performed under inductive loads for up to 40000 switching operations to investigate the effect of different current loads on the arc-erosion performance of electrical contacts. Determination of the mass loss was performed after every 5000 operations. The arc-eroded surfaces were examined using scanning electron microscopy. The chemical composition near the arc was determined by energy dispersive X-ray spectroscopy. The results show that the contact surfaces are greatly affected by arc-erosion, resulting in mass loss due to material migration and/or evaporation. In addition, the arc-affected zones become bigger with the increase in the number of switching operations, especially at 20 A. However, electrical cleaning improves the contact performance by reducing the contact resistance due to breakdown of the non-conducting oxide films formed between 20000 and 25000 switching operations at 20 A. The stationary contacts experience major erosion, whereas the movable contacts suffered less contact erosion under each current load

Fabrication and Arc-Erosion Behavior of Ag8SnO₂ Electrical Contact Materials under Inductive Loads

In this study, Ag-based SnO₂-reinforced electrical contact materials were produced by powder metallurgy and mechanical alloying techniques. Elemental powder mixture containing 8 wt.% SnO₂ was milled in a high-energy planetary-type ball mill, to achieve homogeneously mixed composite powder, and subsequently pressed in a closed die to obtain green compacts with a cylindrical shape and then sintered under vacuum to obtain composites. Composites were then subjected to electrical wear tests under inductive loads to investigate the arc-erosion performance of electrical contacts. Surface deterioration and mass losses of electrical contacts were also evaluated, as a function of increasing switching number. Characterization of the starting and composite powders, green compacts, composites and arc-originated surface deterioration was carried out using scanning electron microscopy and energy-dispersive X-ray spectroscopy. It was found that powder particle size had decreased with the increasing milling time. Density and hardness values of the composites had increased, whereas porosity had decreased with the increasing sintering temperature. Optimum sintering temperature was determined as 900°C. The arc-affected zones became bigger with the increase of the number of switching operations. Furthermore, comparison between surface morphologies and mass losses of arc-eroded specimens had revealed that the stationary contacts exhibit higher rates of erosion than the movable contacts

Optimization of Mechanical Alloying Parameters of Cu25W Electrical Contact Material

In this study, the effect of mechanical alloying parameters, namely the effect of process control agent, ball-to-powder weight ratio and milling duration, on the synthesis of Cu25W composite powder was investigated. Planetary-type ball milling equipment was used to conduct mechanical alloying experiments. Stearic acid was used as the process control agent in order to establish a balance between cold welding and fracturing. The optimum amount of stearic acid was determined as a function of particle size and milling time at constant speed. By using this optimum amount of process control agent, three different ball-to-powder weight ratio values were also employed, and the effect of ball-to-powder weight ratio on particle size and morphology of Cu25W composite powders was investigated. The microstructural evolution of the milled powders was characterized using scanning electron microscopy and laser diffraction analysis. The test results have shown that the morphology and particle size distribution of the milled powders change significantly depending upon the milling parameters. In addition, higher ball-to-powder weight ratio values tend to lower the milling duration for the same amount of particle size reduction. However, particle size reduction suffers beyond the maximal value of ball-to-powder weight ratio, especially in the later stages of mechanical alloying

The Effect of Milling Speed on Particle Size and Morphology of Cu25W Composite Powder

In this study, the effect of milling speed on particle size and morphology of Cu25W composite powder produced by high-energy ball milling was investigated. For this aim, commercial elemental copper and tungsten powders were milled in a planetary-type ball mill for different milling durations. Ball-to-powder weight ratio was selected as 10:1. Three different milling speeds, namely 200, 300, and 400 rpm were used throughout the tests. In order to avoid agglomeration and to decrease the tendency of cold welding among powder particles, stearic acid in amount of 2 wt.% was used as a process control agent. The morphological and microstructural evolution of the milled powders was evaluated by scanning electron microscopy. In addition, the variation of particle size and powder morphology as a function of milling duration was determined. As a result of this effort, the milling duration was found to have strong effect on the structural evolution of the powder, and the optimum particle size as a function of milling speed was determined