Computer-based monitoring platform for renewable energy systems: Four experimental application cases using NI LabVIEW

Sustainability and responsible environmental behaviour constitute a vital premise in the development of the humankind. In fact, during last decades, the global energetic scenario is evolving towards a scheme with increasing relevance of Renewable Energy Sources (RES) like photovoltaic, wind, biomass and hydrogen. Furthermore, hydrogen is an energy carrier which constitutes a mean for long-term energy storage. The integration of hydrogen with local RES contributes to distributed power generation and early introduction of hydrogen economy. Intermittent nature of many of RES, for instance solar and wind sources, impose the development of a management and control strategy to overcome this drawback. This strategy is responsible of providing a reliable, stable and efficient operation of the system. To implement such strategy, a monitoring system is required.The present paper aims to contribute to experimentally validate LabVIEW as valuable tool to develop monitoring platforms in the field of RES-based facilities. To this aim, a set of real systems successfully monitored is exposed.Programa Operativo FEDER de Extremadura 2014-2020) through the grant “Ayuda a Grupos de Investigación” (ref. GR15178) of Junta de Extremadura

Magnetic exchange mechanism for electronic gap opening in graphene

We show within a local self-consistent mean-field treatment that a random distribution of magnetic adatoms can open a robust gap in the electronic spectrum of graphene. The electronic gap results from the interplay between the nature of the graphene sublattice structure and the exchange interaction between adatoms.The size of the gap depends on the strength of the exchange interaction between carriers and localized spins and can be controlled by both temperature and external magnetic field. Furthermore, we show that an external magnetic field creates an imbalance of spin-up and spin-down carriers at the Fermi level, making doped graphene suitable for spin injection and other spintronic applications.Comment: 5 pages, 5 figure

Analysis of long-term statistical data of cobalt flows in the EU

Long-term statistical data was explored, acquired, processed, and analysed in order to assess the historical domestic production and international trade of a number of cobalt-containing commodities in the EU. Different data sources were examined for data, such as the British Geological Survey (BGS), the US Geological Survey (USGS), and the Eurostat and UN Comtrade (UNC) databases, considering all EU-member states before and after they joined the EU. For the international trade, hidden flows related to data gaps such as data reported in monetary value or recorded as “special category” were identified and included in the analysis. In addition, data from the Finnish customs database (ULJAS) was used to complement flows reported by Eurostat and UNC. From UNC, data was obtained considering the member states as reporters or as partners of the trade, due to internal differences of the database. Based on the acquired data the domestic production and international trade of the commodities were reconstructed for the timeframes 1938–2018 and 1988–2018, respectively. Next to the analysis of the trend of the production and trade of the different commodities, the importance of including hidden flows was revealed, where hidden flows represented more than 50% of the flow of a year in some cases. In addition, it was identified that even from reliable data sources, strong differences (more than 100% in some cases) can be found in the reported data, which is crucial to consider when utilizing the data in research

Atom laser dynamics in a tight-waveguide

We study the transient dynamics that arise during the formation of an atom laser beam in a tight waveguide. During the time evolution the density profile develops a series of wiggles which are related to the diffraction in time phenomenon. The apodization of matter waves, which relies on the use of smooth aperture functions, allows to suppress such oscillations in a time interval, after which there is a revival of the diffraction in time. The revival time scale is directly related to the inverse of the harmonic trap frequency for the atom reservoir.Comment: 6 pages, 5 figures, to be published in the Proceedings of the 395th WE-Heraeus Seminar on "Time Dependent Phenomena in Quantum Mechanics ", organized by T. Kramer and M. Kleber (Blaubeuren, Germany, September 2007

Efeito da rocha ultramáfica alcalina sobre a composição química e produtividade da alfafa cultivada em Argissolo Amarelo distrófico.

Com o objetivo de avaliar a eficiência da rocha ultramáfica alcalina na fertilidade do solo, estado nutricional e produção de matéria seca da alfafa, foi conduzido em vasos com Argissolo Amarelo distrófico um experimento em delineamento inteiramente casualizado, em parcelas subdivididas, com três repetições. Os tratamentos foram constituídos por quatro doses (0, 100, 150 e 300 mg/kg de K), oriundas da rocha ultramáfica alcalina (K20 = 3,44%, PN = 50%, CaO = 13,22%, MgO = 16,88%, P2O5 = 1,40%, SiO2 = 35,57% e pH = 8,8) com duas granulometrias (0,3 e 2,0 mm) e um tratamento adicional com KCl (150 mg/kg - 60% de Ká-dois-O), as subparcelas foram constituídas por cinco épocas de corte com intervalo de 30 dias. Os resultados demonstraram incremento na produção de matéria seca com aplicação ultramáfica, entretanto, inferior ao obtido com KCl. Houve aumento nos teores de P disponível e K, Ca e Mg trocável no solo, porém esse efeito refletiu positivamente somente nos teores foliares de P e K, provavelmente, devido ao efeito de inibição