930 resultados para Energy Harvesting, Convertitori di potenza, Maximum Power Point Tracking, Applicazioni low power
Resumo:
Young trees transplanted from nursery into open field require a minimum amount of soil moisture to successfully root in their new location, especially in dry-climate areas. One possibility is to obtain the required water from air moisture. This can be achieved by reducing the temperature of a surface below the air dew point temperature, inducing water vapor condensation on the surface. The temperature of a surface can be reduced by applying the thermoelectric effect, with Peltier modules powered by electricity. Here, we present a system that generates electricity with a solar photovoltaic module, stores it in a battery, and finally, uses the electricity at the moment in which air humidity and temperature are optimal to maximize water condensation while minimizing energy consumption. Also, a method to reduce the evaporation of the condensed water is proposed. The objective of the system is to sustain young plants in drier periods, rather than exclusively irrigating young plants to boost their growth.
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Helium Brayton cycles have been studied as power cycles for both fission and fusion reactors obtaining high thermal efficiency. This paper studies several technological schemes of helium Brayton cycles applied for the HiPER reactor proposal. Since HiPER integrates technologies available at short term, its working conditions results in a very low maximum temperature of the energy sources, something that limits the thermal performance of the cycle. The aim of this work is to analyze the potential of the helium Brayton cycles as power cycles for HiPER. Several helium Brayton cycle configurations have been investigated with the purpose of raising the cycle thermal efficiency under the working conditions of HiPER. The effects of inter-cooling and reheating have specifically been studied. Sensitivity analyses of the key cycle parameters and component performances on the maximum thermal efficiency have also been carried out. The addition of several inter-cooling stages in a helium Brayton cycle has allowed obtaining a maximum thermal efficiency of over 36%, and the inclusion of a reheating process may also yield an added increase of nearly 1 percentage point to reach 37%. These results confirm that helium Brayton cycles are to be considered among the power cycle candidates for HiPER.
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The objective of this paper is to provide performance metrics for small-signal stability assessment of a given system architecture. The stability margins are stated utilizing a concept of maximum peak criteria (MPC) derived from the behavior of an impedance-based sensitivity function. For each minor-loop gain defined at every system interface, a single number to state the robustness of stability is provided based on the computed maximum value of the corresponding sensitivity function. In order to compare various power-architecture solutions in terms of stability, a parameter providing an overall measure of the whole system stability is required. The selected figure of merit is geometric average of each maximum peak value within the system. It provides a meaningful metrics for system comparisons: the best system in terms of robust stability is the one that minimizes this index. In addition, the largest peak value within the system interfaces is given thus detecting the weakest point of the system in terms of robustness.
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Patterns in sequences of amino acid hydrophobic free energies predict secondary structures in proteins. In protein folding, matches in hydrophobic free energy statistical wavelengths appear to contribute to selective aggregation of secondary structures in hydrophobic zippers. In a similar setting, the use of Fourier analysis to characterize the dominant statistical wavelengths of peptide ligands and receptor proteins hydrophobic modes to predict such matches has been limited by the aliasing and end effects of short peptide lengths, as well as the broad-band, mode multiplicity of many of their frequency (power) spectra. In addition, the sequence locations of the matching modes are lost in this transformation. We make new use of three techniques to address these difficulties: (i) eigenfunction construction from the linear decomposition of the lagged covariance matrices of the ligands and receptors as hydrophobic free energy sequences; (ii) maximum entropy, complex poles power spectra, which select the dominant modes of the hydrophobic free energy sequences or their eigenfunctions; and (iii) discrete, best bases, trigonometric wavelet transformations, which confirm the dominant spectral frequencies of the eigenfunctions and locate them as (absolute valued) moduli in the peptide or receptor sequence. The leading eigenfunction of the covariance matrix of a transmembrane receptor sequence locates the same transmembrane segments seen in n-block-averaged hydropathy plots while leaving the remaining hydrophobic modes unsmoothed and available for further analyses as secondary eigenfunctions. In these receptor eigenfunctions, we find a set of statistical wavelength matches between peptide ligands and their G-protein and tyrosine kinase coupled receptors, ranging across examples from 13.10 amino acids in acid fibroblast growth factor to 2.18 residues in corticotropin releasing factor. We find that the wavelet-located receptor modes in the extracellular loops are compatible with studies of receptor chimeric exchanges and point mutations. A nonbinding corticotropin-releasing factor receptor mutant is shown to have lost the signatory mode common to the normal receptor and its ligand. Hydrophobic free energy eigenfunctions and their transformations offer new quantitative physical homologies in database searches for peptide-receptor matches.
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A new control algorithm using parallel braking resistor (BR) and serial fault current limiter (FCL) for power system transient stability enhancement is presented in this paper. The proposed control algorithm can prevent transient instability during first swing by immediately taking away the transient energy gained in faulted period. It can also reduce generator oscillation time and efficiently make system back to the post-fault equilibrium. The algorithm is based on a new system energy function based method to choose optimal switching point. The parallel BR and serial FCL resistor can be switched at the calculated optimal point to get the best control result. This method allows optimum dissipation of the transient energy caused by disturbance so to make system back to equilibrium in minimum time. Case studies are given to verify the efficiency and effectiveness of this new control algorithm.
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Various micro-radial compressor configurations were investigated using one-dimensional meanline and computational fluid dynamics (CFD) techniques for use in a micro gas turbine (MGT) domestic combined heat and power (DCHP) application. Blade backsweep, shaft speed, and blade height were varied at a constant pressure ratio. Shaft speeds were limited to 220 000 r/min, to enable the use of a turbocharger bearing platform. Off-design compressor performance was established and used to determine the MGT performance envelope; this in turn was used to assess potential cost and environmental savings in a heat-led DCHP operating scenario within the target market of a detached family home. A low target-stage pressure ratio provided an opportunity to reduce diffusion within the impeller. Critically for DCHP, this produced very regular flow, which improved impeller performance for a wider operating envelope. The best performing impeller was a low-speed, 170 000 r/min, low-backsweep, 15 configuration producing 71.76 per cent stage efficiency at a pressure ratio of 2.20. This produced an MGT design point system efficiency of 14.85 per cent at 993 W, matching prime movers in the latest commercial DCHP units. Cost and CO2 savings were 10.7 per cent and 6.3 per cent, respectively, for annual power demands of 17.4 MWht and 6.1 MWhe compared to a standard condensing boiler (with grid) installation. The maximum cost saving (on design point) was 14.2 per cent for annual power demands of 22.62 MWht and 6.1 MWhe corresponding to an 8.1 per cent CO2 saving. When sizing, maximum savings were found with larger heat demands. When sized, maximum savings could be made by encouraging more electricity export either by reducing household electricity consumption or by increasing machine efficiency.
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Using a well-established analytic nonlinear signal-to-noise ratio noise model we show that there are very simple, fibre independent, amplifier gains which minimize the total energy requirement for amplified systems. Power savings of over 50% are shown to be possible by choosing appropriate amplifier gain and output power.
Resumo:
A tanulmny arra keresi a vlaszt, hogy a megjul alap ramtermelk tmogatsa cskkentleg hathat- e a villamos energia nagykereskedelmi s kiskereskedelmi rra. Ez utbbi tartalmazza a megjulk tmogatsnak sszegt is. Szmos elmleti cikk rmutatott arra, hogy nemcsak a nagykereskedelmi rak, hanem a kiskereskedelmi villamosenergia-rak is cskkenhetnek a drgbb, megjul alap ramtermelk tmogatsa rvn. A tanulmny sorn egy villamosenergia-piacokat szimull modell segtsgvel modellezi a szerz, hogy a klnbz mennyisg szlermvi s fotovoltaikus kapacits tmogatsa hogyan hat a magyarorszgi nagykereskedelmi s kiskereskedelmi rakra. _____ Impact of the Hungarian renewable based power generation on electricity price The aim of this paper is to answer the question whether the support of renewable power generation could decrease the wholesale and retail electricity prices. The latter one includes the support of renewables. Several studies point out that not only the wholesale, but the retail electricity prices could decrease when supporting the more expensive, renewable power generation. A model, which simulates the electricity markets, is used in order to analyse the impact of different level of wind and photo voltaic power generator support fee on Hungarian wholesale and retail electricity prices.
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Ce projet de recherche mene en collaboration industrielle avec St-Jean Photochimie Inc. / PCAS Canada vise le developpement et la caracterisation de derives dipyrromethene pour des applications dans le domaine du photovoltaique. La quete du recoltage des photons se situant dans le proche-infrarouge a ete au centre des modifications structurales explorees afin daugmenter lefficacite de conversion des cellules solaires de type organique et a pigments photosensibles. Trois familles de composes integrant le motif dipyrromethene ont ete synthetisees et caracterisees du point de vue spectroscopique, electrochimique, structural ainsi que par modelisation moleculaire afin detablir des relations structures-proprietes. La premiere famille comporte six azadipyrromethenes au potentiel de coordination tetradentate sur des centres metalliques. Le developpement dune nouvelle voie synthetique asymetrique combinee a lutilisation dune voie symetrique classique ont permis dobtenir lensemble des combinaisons de substituants possibles sur les aryles proximaux incluant les noyaux 2-hydroxyphenyle, 2-methoxyphenyle et 2- pyridyle. La modulation du maximum dabsorption dans le rouge a pu etre faite entre 598 et 619 nm. De meme, la presence de groupements methoxyle ou hydroxyle augmente labsorption dans le violet (~410 nm) tel que demontre par modelisation. La caracterisation electrochimique a montre que les derives tetradentates etaient en general moins stables aux processus redox que leur contre-parti bidentate. La deuxieme famille comporte dix derives BODIPY fusionnes de facon asymetrique en position [b]. Laryle proximal a ete modifie de facon systematique afin de mieux comprendre limpact des substituents riches en electron et de la fusion de cycles aromatiques. De plus, ces derives ont ete mis en relation avec une vaste serie de composes analogues. Les resultats empiriques ont montre que les proprietes optoelectroniques de la plateforme sont regies par le degre de communication electronique entre laryle proximal, le pyrrole sur lequel il est attache et le noyau indolique adjacent a ce dernier. Les maximums dabsorption dans le rouge sont modulables entre 547 et 628 nm et la fluorescence des composes se situe dans le proche- infrarouge. Lun des compose sest revele souhaitable pour une utilisation en photovoltaique ainsi qua titre de sonde a pH. La troisieme famille comporte cinq complexes neutres de RuII bases sur des polypyridines et portant un ligand azadipyrromethene cyclometale. Les composes ont montre une forte absorption de photons dans la region de 600 a 800 nm (rouge a proche- infrarouge) et qui a pu etre etendue au-dela de 1100 nm dans le cas des derives portant un ligand terpyridine. Lanalyse des proprietes optoelectroniques de facon empirique et theorique a montre un impact significatif de la cyclometalation et ouvert la voie pour leur etude en tant que photosensibilisateurs en OPV et en DSSC. La capacite dun des complexes a photo-injecter un electron dans la bande de conduction du semi-conducteur TiO2 a ete demontre en collaboration avec le groupe du Pr Gerald J. Meyer a University of North Carolina at Chapel Hill, premier pas vers une utilisation dans les cellules solaires a pigments photosensibles. La stabilite des complexes en solution sest toutefois averee problematique et des pistes de solutions sont suggerees basees sur les connaissances acquises dans le cadre de cette these.
Resumo:
Scopo del presente lavoro la presentazione del codice di calcolo semplificato adoperato nella sezione Simulatore fotovoltaico presente sul portale www.energia.cnr.it del progetto CNR ENERGY+. Utilizzando i valori reali di radiazione solare misurati dalle stazioni meteorologiche installate presso alcune sedi del CNR il codice, con appropriati algoritmi, generala scomposizione della radiazione sul piano orizzontale e su superfici inclinate e variamente orientate, in modo da pervenire alla potenza prodotta da un ipotetico impianto fotovoltaico posto sullo stesso sito di ubicazione della stazione.
Resumo:
Ce projet de recherche mene en collaboration industrielle avec St-Jean Photochimie Inc. / PCAS Canada vise le developpement et la caracterisation de derives dipyrromethene pour des applications dans le domaine du photovoltaique. La quete du recoltage des photons se situant dans le proche-infrarouge a ete au centre des modifications structurales explorees afin daugmenter lefficacite de conversion des cellules solaires de type organique et a pigments photosensibles. Trois familles de composes integrant le motif dipyrromethene ont ete synthetisees et caracterisees du point de vue spectroscopique, electrochimique, structural ainsi que par modelisation moleculaire afin detablir des relations structures-proprietes. La premiere famille comporte six azadipyrromethenes au potentiel de coordination tetradentate sur des centres metalliques. Le developpement dune nouvelle voie synthetique asymetrique combinee a lutilisation dune voie symetrique classique ont permis dobtenir lensemble des combinaisons de substituants possibles sur les aryles proximaux incluant les noyaux 2-hydroxyphenyle, 2-methoxyphenyle et 2- pyridyle. La modulation du maximum dabsorption dans le rouge a pu etre faite entre 598 et 619 nm. De meme, la presence de groupements methoxyle ou hydroxyle augmente labsorption dans le violet (~410 nm) tel que demontre par modelisation. La caracterisation electrochimique a montre que les derives tetradentates etaient en general moins stables aux processus redox que leur contre-parti bidentate. La deuxieme famille comporte dix derives BODIPY fusionnes de facon asymetrique en position [b]. Laryle proximal a ete modifie de facon systematique afin de mieux comprendre limpact des substituents riches en electron et de la fusion de cycles aromatiques. De plus, ces derives ont ete mis en relation avec une vaste serie de composes analogues. Les resultats empiriques ont montre que les proprietes optoelectroniques de la plateforme sont regies par le degre de communication electronique entre laryle proximal, le pyrrole sur lequel il est attache et le noyau indolique adjacent a ce dernier. Les maximums dabsorption dans le rouge sont modulables entre 547 et 628 nm et la fluorescence des composes se situe dans le proche- infrarouge. Lun des compose sest revele souhaitable pour une utilisation en photovoltaique ainsi qua titre de sonde a pH. La troisieme famille comporte cinq complexes neutres de RuII bases sur des polypyridines et portant un ligand azadipyrromethene cyclometale. Les composes ont montre une forte absorption de photons dans la region de 600 a 800 nm (rouge a proche- infrarouge) et qui a pu etre etendue au-dela de 1100 nm dans le cas des derives portant un ligand terpyridine. Lanalyse des proprietes optoelectroniques de facon empirique et theorique a montre un impact significatif de la cyclometalation et ouvert la voie pour leur etude en tant que photosensibilisateurs en OPV et en DSSC. La capacite dun des complexes a photo-injecter un electron dans la bande de conduction du semi-conducteur TiO2 a ete demontre en collaboration avec le groupe du Pr Gerald J. Meyer a University of North Carolina at Chapel Hill, premier pas vers une utilisation dans les cellules solaires a pigments photosensibles. La stabilite des complexes en solution sest toutefois averee problematique et des pistes de solutions sont suggerees basees sur les connaissances acquises dans le cadre de cette these.
Resumo:
The voltage profile of the catenary between traction substations (TSSs) is affected by the trolleybus current intake and by its position with respect to the TSSs: the higher the current requested by the bus and the further the bus from the TSSs, the deeper the voltage drop. When the voltage drops below 500V, the trolleybus is forced to decrease its consumption by reducing its input current. This thesis deals with the analysis of the improvements that the installation of an BESS produces in the operation of a particularly loaded FS of the DC trolleybus network of the city of Bologna. The stationary BESS is charged by the TSSs during off-peak times and delivers the stored energy when the catenary is overloaded alleviating the load on the TSSs and reducing the voltage drops. Only IMC buses are considered in the prospect of a future disposal of all internal combustion engine vehicles. These trolleybuses cause deeper voltage drops because they absorb enough current to power their traction motor and recharge the on board battery. The control of the BESS aims to keep the catenary voltage within the admissible voltage range and makes sure that all physical limitations are met. A model of FS Marconi Trento Trieste is implemented in Simulink environment to simulate its daily operation and compare the behavior of the trolleybus network with and without BESS. From the simulation without BESS, the best location of the energy storage system is deduced, and the battery control is tuned. Furthermore, from the knowledge of the load curve and the battery control trans-characteristic, it is formulated a prediction of the voltage distribution at BESS connection point. The prediction is then compared with the simulation results to validate the Simulink model. The BESS allows to decrease the voltage drops along the catenary, the Joule losses and the current delivered by the TSSs, indicating that the BESS can be a solution to improve the operation of the trolleybus network.
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The growing market of electrical cars, portable electronics, photovoltaic systems..etc. requires the development of efficient, low-cost, and low environmental impact energy storage devices (ESDs) including batteries and supercapacitors.. Due to their extended charge-discharge cycle, high specific capacitance, and power capabilities supercapacitors are considered among the most attractive ESDs. Over the last decade, research and development in supercapacitor technology have accelerated: thousands of articles have been published in the literature describing the electrochemical properties of the electrode materials and electrolyte in addition to separators and current collectors. Carbon-based supercapacitor electrodes materials have gained increasing attention due to their high specific surface area, good electrical conductivity, and excellent stability in harsh environments, as well as other characteristics. Recently, there has been a surge of interest in activated carbon derived from low-cost abundant sources such as biomass for supercapacitor electrode materials. Also, particular attention was given to a major challenging issue concerning the substitution of organic solutions currently used as electrolytes due to their highest electrochemical stability window even though their high cost, toxicity, and flammability. In this regard, the main objective of this thesis is to investigate the performances of supercapacitors using low cost abundant safe, and low environmental impact materials for electrodes and electrolytes. Several prototypes were constructed and tested using natural resources through optimization of the preparation of appropriate carbon electrodes using agriculture by-products waste or coal (i.e. Argan shell or Anthracite from Jerrada). Such electrodes were tested using several electrolyte formulations (aqueous and water in salt electrolytes) beneficing their non-flammability, lower cost, and environmental impact; the characteristics that provide a promising opportunity to design safer, inexpensive, and environmentally friendly devices compared to organic electrolytes.
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La costante ricerca e lo sviluppo nel campo degli azionamenti e dei motori elettrici hanno portato ad una loro sempre maggiore applicazione ed utilizzo. Tuttavia, la crescente esigenza di sistemi ad alta potenza sempre pi performanti da una parte ha evidenziato i limiti di certe soluzioni, dallaltra laffermarsi di altre. In questi sistemi, infatti, la macchina elettrica trifase non rappresenta pi lunica soluzione possibile: negli ultimi anni si assistito ad una sempre maggiore diffusione di macchine elettriche multifase. Grazie alle maggiori potenzialit che sono in grado di offrire, per quanto alcune di queste siano ancora sconosciute, risultano gi essere una valida alternativa rispetto alla tradizionale controparte trifase. Sicuramente per, fra le varie architetture multifase, quelle multi-trifase (ovvero quelle con un numero di fasi multiplo di tre) rappresentano una soluzione particolarmente vantaggiosa in ambito industriale. Infatti, se impiegate allinterno di architetture multifase, la profonda conoscenza dei tradizionali sistemi trifase consente di ridurre i costi ed i tempi legati alla loro progettazione. In questo elaborato la macchina elettrica multi-trifase analizzata una macchina sincrona esafase con rotore a magneti permanenti superficiali. Questa particolare tipologia di macchina elettrica pu essere modellizzata attraverso due approcci completamente differenti: uno esafase ed uno doppio trifase. Queste possibilit hanno portato molti ricercatori alla ricerca della migliore strategia di controllo per questa macchina. Lobiettivo di questa tesi di effettuare unanalisi comparativa tra tre diverse strategie di controllo applicate alla stessa macchina elettrica multi-trifase, analizzandone la risposta dinamica in diverse condizioni di funzionamento.
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We report the first measurements of the moments--mean (M), variance ((2)), skewness (S), and kurtosis ()--of the net-charge multiplicity distributions at midrapidity in Au+Au collisions at seven energies, ranging from sqrt[sNN]=7.7 to 200 GeV, as a part of the Beam Energy Scan program at RHIC. The moments are related to the thermodynamic susceptibilities of net charge, and are sensitive to the location of the QCD critical point. We compare the products of the moments, (2)/M, S, and (2), with the expectations from Poisson and negative binomial distributions (NBDs). The S values deviate from the Poisson baseline and are close to the NBD baseline, while the (2) values tend to lie between the two. Within the present uncertainties, our data do not show nonmonotonic behavior as a function of collision energy. These measurements provide a valuable tool to extract the freeze-out parameters in heavy-ion collisions by comparing with theoretical models.
