12,516 research outputs found

    Experimental tests to recover the photovoltaic power by battery system

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    The uncertainty and variability of the Renewable Energy Sources (RES) power plants within the power grid is an open issue. The present study focuses on the use of batteries to overcome the limitations associated with the photovoltaic inverter operation, trying to maximize the global energy produced. A set of switches, was placed between a few photovoltaic modules and a commercial inverter, capable to change configuration of the plant dynamically. Such system stores the power that the inverter is not able to let into the grid inside batteries. At the base of this optimization, there is the achievement of two main configurations in which the batteries and the photovoltaic modules are electrically connected in an appropriate manner as a function of inverter efficiency and thus solar radiation. A control board and the relative program, to change the configuration, was designed and implemented, based on the value of the measured radiation, current, batteries voltage, and calculated inverter efficiency. Finally from the cost and impact analysis we can say that, today the technology of lithium batteries, for this application, is still too expensive in comparison with lead-acid batteries

    Hydrogen vs. Battery in the long-term operation. A comparative between energy management strategies for hybrid renewable microgrids

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    The growth of the world’s energy demand over recent decades in relation to energy intensity and demography is clear. At the same time, the use of renewable energy sources is pursued to address decarbonization targets, but the stochasticity of renewable energy systems produces an increasing need for management systems to supply such energy volume while guaranteeing, at the same time, the security and reliability of the microgrids. Locally distributed energy storage systems (ESS) may provide the capacity to temporarily decouple production and demand. In this sense, the most implemented ESS in local energy districts are small–medium-scale electrochemical batteries. However, hydrogen systems are viable for storing larger energy quantities thanks to its intrinsic high mass-energy density. To match generation, demand and storage, energy management systems (EMSs) become crucial. This paper compares two strategies for an energy management system based on hydrogen-priority vs. battery-priority for the operation of a hybrid renewable microgrid. The overall performance of the two mentioned strategies is compared in the long-term operation via a set of evaluation parameters defined by the unmet load, storage efficiency, operating hours and cumulative energy. The results show that the hydrogen-priority strategy allows the microgrid to be led towards island operation because it saves a higher amount of energy, while the battery-priority strategy reduces the energy efficiency in the storage round trip. The main contribution of this work lies in the demonstration that conventional EMS for microgrids’ operation based on battery-priority strategy should turn into hydrogen-priority to keep the reliability and independence of the microgrid in the long-term operation

    Cultivating diversity and food quality. Proceedings of Diversifood EU Forum, Brussels, 11 April 2018

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    To tackle this issue, Diversifood team organised a forum with policy makers and stakeholders on the 11th of April 2018, in Brussels. Diversifood’s aim is to share results and key lessons including new approaches for the management of cultivated biodiversity, for plant breeding for sustainable farming systems, and new relationships among actors of food systems. In the afternoon, there was time for discussion, knowledge sharing, collecting feedback and extending current policies to include cultivating diversity and food quality (for FP9, CAP 2020, The outputs of this workshop will feed Diversifood’s final recommendations. The forum was kindly hosted by the European Committee of the Regions (Rue Belliard/Belliardstraat 101, 1040 Brussels)

    The m−m-dissimilarity map and representation theory of SLmSL_m

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    We give another proof that mm-dissimilarity vectors of weighted trees are points on the tropical Grassmanian, as conjectured by Cools, and proved by Giraldo in response to a question of Sturmfels and Pachter. We accomplish this by relating mm-dissimilarity vectors to the representation theory of SLm.SL_m.Comment: 11 pages, 8 figure

    Studies on the biological effects of ozone: 8. Effects on the total antioxidant status and on interleukin-8 production.

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    Ozone (O3) is a controversial gas because, owing to its potent oxidant properties, it exerts damaging effects on the respiratory tract and yet it has been used for four decades as a therapy. While the disinfectant activity of O3 is understandable, it is less clear how other biological effects can be elicited in human blood with practically no toxicity. On the other hand plasma and cells are endowed with a powerful antioxidant system so that a fairly wide range of O3 concentrations between 40 and 80 microg/ml per gram of blood (approximately 0.83-1.66 mM) are effective but not deleterious. After blood ozonation total antioxidant status (TAS) and plasma protein thiol groups (PTG) decrease by 20% and 25%, respectively, while thiobarbituric acid reactive substances (TBARS) increases up to five-fold. The increase of haemolysis is negligible suggesting that the erythrocyte membrane is spared at the expense of other sacrificial substrates. While there is a clear relationship between the ozone dose and IL-8 levels, we have noticed that high TAS and PTG values inhibit the cytokine production. This is in line with the current idea that hydrogen peroxide, as a byproduct of O3 decomposition, acts as a messenger for the cytokine induction

    Use of bremsstrahlung radiation to identify hidden weak beta- sources: feasibility and possible use in radio-guided surgery

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    The recent interest in beta- radionuclides for radio-guided surgery derives from the feature of the beta radiation to release energy in few millimeters of tissue. Such feature can be used to locate residual tumors with a probe located in its immediate vicinity, determining the resection margins with an accuracy of millimeters. The drawback of this technique is that it does not allow to identify tumors hidden in more than few mm of tissue. Conversely, the bremsstrahlung X-rays emitted by the interaction of the beta- radiation with the nuclei of the tissue are relatively penetrating. To complement the beta- probes, we have therefore developed a detector based on cadmium telluride, an X-ray detector with a high quantum efficiency working at room temperature. We measured the secondary emission of bremsstrahlung photons in a target of Polymethylmethacrylate (PMMA) with a density similar to living tissue. The results show that this device allows to detect a 1 ml residual or lymph-node with an activity of 1 kBq hidden under a layer of 10 mm of PMMA with a 3:1 signal to noise, i.e. with a five sigma discrimination in less than 5 s

    ELMB Microcontroller Firmware and SCADA Integration for the LHCb Muon Detector Readout Control System

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    The LHCb system requires high efficiency muon detection into LHC bunch crossing: 95% into a 25 ns time window. To reach such efficiency many parameters of the detector readout apparatus have to be calibrated and adjusted and its channels must be aligned in time. In addition, essential characteristics must be monitored to guarantee a good working condition of the apparatus (to avoid loss of efficiency and to minimize systematic errors). As the number of the muon readout parameters is extremely high (∌700000 registers), a system able to process information in parallel is required: 122000 readout channels will be controlled by about 600 microcontrollers and 6 computers. The complexity of such an apparatus requires the use of a distributed system. For this a Supervisory Control And Data Acquisition (SCADA) based system is being developed to control the entire detector readout equipment. Moreover, a Finite State Machine (FSM) implementation is being developed to integrate the Detector Readout Control (DRC) into the LHC Experiment Control System (ECS)

    EFFECT OF CONSERVATION PRACTICES ON FUNCTIONAL DIVERSITY AND ASSEMBLY OF WEED COMMUNITIES: A DATABASE OF FUNCTIONAL TRAITS

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    The incorporation of conservation agriculture techniques (e.g. reduced tillage and green manures) in organic farming systems brings many benefits to the environment and reduces energy use (Holland, 2004). One of the main drawbacks of the use of reduced tillage is the potential increase in weed infestation and shifts in the weed community composition, sometimes to the benefit of more difficult-to-control species (BĂ rberi, 2002; PeignĂ© et al., 2007; Sans et al., 2011). However, weeds have an important role in maintaining farmland functional biodiversity (BĂ rberi et al, 2010; Caballero et al., 2010), and this should be balanced with their potential negative impact on crop yield and quality. Within the frame of the European project “Reduced tillage and green manures for sustainable cropping systems” (TILMAN-ORG), in 2012 we started a study with the aim of evaluating the effects of conservation agricultural methods on functional attributes of weed communities, taking into account both the potential detrimental effects of weeds on crop growth and yield and the potential ecological services or dis-services. Knowledge on the outcome of positive and negative effects will be useful in the context of evaluating soil conservation practices in organic farming. In this paper we highlight the approach used to build the weed functional traits database, the first step in this study
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