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Diaz-Gonzalez F.,Catalonia Institute for Energy Research IREC | Sumper A.,Catalonia Institute for Energy Research IREC | Sumper A.,Polytechnic University of Catalonia | Gomis-Bellmunt O.,Catalonia Institute for Energy Research IREC | And 2 more authors.
Renewable and Sustainable Energy Reviews | Year: 2012

Due to the stochastic nature of wind, electric power generated by wind turbines is highly erratic and may affect both the power quality and the planning of power systems. Energy Storage Systems (ESSs) may play an important role in wind power applications by controlling wind power plant output and providing ancillary services to the power system and therefore, enabling an increased penetration of wind power in the system. This article deals with the review of several energy storage technologies for wind power applications. The main objectives of the article are the introduction of the operating principles, as well as the presentation of the main characteristics of energy storage technologies suitable for stationary applications, and the definition and discussion of potential ESS applications in wind power, according to an extensive literature review. © 2012 Elsevier Ltd. All rights reserved.


Bianchi F.D.,Catalonia Institute for Energy Research IREC | Sanchez Pena R.S.,Buenos Aires Institute of Technology
Automatica | Year: 2011

Here, a methodology is presented which considers the interpolation of linear time-invariant (LTI) controllers designed for different operating points of a nonlinear system in order to produce a gain-scheduled controller. Guarantees of closed-loop quadratic stability and performance at intermediate interpolation points are presented in terms of a set of linear matrix inequalities (LMIs). The proposed interpolation scheme can be applied in cases where the system must remain at the operating points most of the time and the transitions from one point to another rarely occur, e.g., chemical processes, satellites. © 2010 Elsevier Ltd. All rights reserved.


Depoorter V.,Catalonia Institute for Energy Research IREC | Oro E.,Catalonia Institute for Energy Research IREC | Salom J.,Catalonia Institute for Energy Research IREC
Applied Energy | Year: 2015

The massive data centre energy consumption has motivated significant efforts to use energy efficiency strategies and the implementation of renewable energy sources that reduce their operational costs and environmental impact. Considering that the potential of many of these measures is often closely linked to the climate conditions, the location of data centres can have a major impact on their energy demand. Moreover, from a holistic approach, differences among regions become even more important when accounting for the electricity attributes from the grid. To assess these differences this work compares by the use of energy indicators the behaviour of a data centre located at different representative emplacements in Europe. To do so, a dynamic energy model which incorporates free cooling strategy and photovoltaic energy is developed. The paper concludes by suggesting that future data centre developments could consider site selection as a new strategy to limit the environmental impact attributable to this sector. © 2014 Elsevier Ltd.


Morante J.R.,Catalonia Institute for Energy Research IREC | Morante J.R.,University of Barcelona
Nanotechnology | Year: 2013

Insight into chemical to electrical transduction mechanisms taking place at the surface of a single metal oxide nanowire is reported due to its outstanding importance for determining the characteristics of resistive solid state gas sensors. The surface chemical reaction kinetics is discussed considering competitiveness phenomena among different active sites and gas species on the nanowire taken as a metal oxide monocrystal at the nanoscale level. Experimental results for different representative gas molecules are shown to determine and understand sensor selectivity. The reported gas species are carbon monoxide and water vapour as general reference molecules, and ethanol and ammonia species as special references for gas-solid interactions, respectively, on acid and basic sites. Kinetic properties are proposed as particular signatures for each of the possible surface chemical reactions, allowing their identification and distinction. Likewise, features such as thermal inertia limitation and effects of the molecular and monoatomic absorbed oxygen are also estimated considering operation working modes based on nanowire self-heating. Furthermore, the applicability of a surface electrical field on a one-dimensional metal oxide nanostructure to enhance the surface ionization of the absorbed molecules is also reviewed as a new type of metal oxide based nanosensor for achieving improved selectivity. © 2013 IOP Publishing Ltd.


Abello S.,Catalonia Institute for Energy Research IREC | Montane D.,Catalonia Institute for Energy Research IREC | Montane D.,Rovira i Virgili University
ChemSusChem | Year: 2011

The continuous increase in oil prices together with an increase in carbon dioxide concentration in the atmosphere has prompted an increased interest in the production of liquid fuels from non-petroleum sources to ensure the continuation of our worldwide demands while maximizing CO 2 utilization. In this sense, the Fischer-Tropsch (FT) technology provides a feasible option to render high value-added hydrocarbons. Alternative sources, such as biomass or coal, offer a real possibility to realize these purposes by making use of H 2-deficient or CO 2-rich syngas feeds. The management of such feeds ideally relies on the use of iron catalysts, which exhibit the unique ability to adjust the H 2/CO molar ratio to an optimum value for hydrocarbon synthesis through the water-gas-shift reaction. Taking advantage of the emerging attention to hybrid FT-synthesis catalysts based on cobalt and their associated benefits, an overview of the current state of literature in the field of iron-based multifunctional catalysts is presented. Of particular interest is the use of zeolites in combination with a FT catalyst in a one-stage operation, herein named multifunctional, which offer key opportunities in the modification of desired product distributions and selectivity, to eventually overcome the quality limitations of the fuels prepared under intrinsic FT conditions. This review focuses on promising research activities addressing the conversion of syngas to liquid fuels mediated by iron-based multifunctional materials, highlights their preparation and properties, and discusses their implication and challenges in the area of carbon utilization through H 2/CO(+CO 2) mixtures. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Shavel A.,University of Barcelona | Arbiol J.,Catalan Institution for Research and Advanced Studies | Cabot A.,University of Barcelona | Cabot A.,Catalonia Institute for Energy Research IREC
Journal of the American Chemical Society | Year: 2010

A successful synthesis of Cu2ZnxSnySe 1+ x +2 y (CZTSe) nanoparticles is presented. Nearly monodisperse and highly faceted CZTSe nanoparticles were prepared through reaction of metal amino complexes with saturated solutions of selenium in trioctylphosphine at high temperature. High-resolution transmission electron microscopy and X-ray diffraction analysis showed the prepared nanocrystals to have the tetragonal Cu2ZnSnSe4 crystallographic structure. Nanoscale-resolved electron energy loss spectroscopy images showed the presence of the four elements in each individual nanocrystal. Further analyses of the particles chemical composition showed the nanocrystals to be consistently Zn- and Sn-poor. © 2010 American Chemical Society.


Abello S.,Catalonia Institute for Energy Research IREC | Bolshak E.,Rovira i Virgili University | Montane D.,Catalonia Institute for Energy Research IREC
Applied Catalysis A: General | Year: 2013

Nickel-iron mixed oxides derived from reevesite, a hydrotalcite-type compound, were tested in steam reforming of ethanol for hydrogen production. The influence of iron content (Ni/Fe ranging from 3 to 1) and the calcination temperature of the catalyst precursor (773 and 1073 K) on the catalytic performance were investigated. Both parameters were essential to optimize the reforming performance. Increasing the amount of iron in the reevesite precursors affected both the chemical and activity properties of the derived mixed oxide catalysts. Iron displays a positive role in nickel-based catalysts due to the enhancement of catalytic activity and hydrogen selectivity induced by the improved dispersion of nickel and the alleviation in carbon deposition. The calcination temperature led to variations in phase composition consisting of Ni(Fe)Ox solid solution and NiFe2O4, which affected the final size and dispersion of nickel species formed during the reaction. The best catalyst, with a Ni/Fe ratio of 1 and calcined at 773 K, rendered high and stable hydrogen and carbon dioxide selectivity of up to ca. 60% and 40%, respectively, low methane content, and consisted of a Ni(Fe)O x + NiFe2O4 mixture with high surface area and small Ni0 crystallites. A higher percentage of crystalline NiFe 2O4 attained at high calcination temperature (1073 K) associated with a lower carbon deposition resistance and probably Ni0 sintering brings about lower activity and fast deactivation. The improved performance over catalysts calcined at lower temperature and with lower Ni/Fe ratio is motivated by the effect of iron on the structural and electronic properties of the mixed oxides, thus inducing a slow formation of metallic nickel particles and coke deposits. Features like high surface area, higher iron content, lower reducibility of nickel species and small nickel crystallite size well dispersed on the surface of the catalyst with high iron content lead to a higher activity in ethanol dehydrogenation, acetaldehyde decarbonylation and reforming, and WGS. © 2012 Elsevier B.V.


Inthamoussou F.A.,National University of La Plata | Pegueroles-Queralt J.,Catalonia Institute for Energy Research IREC | Bianchi F.D.,Catalonia Institute for Energy Research IREC
IEEE Transactions on Energy Conversion | Year: 2013

The proper operation of a microgrid requires storage devices that increase the inertia and avoid instability of the system. This paper presents the control of an energy storage system (ESS) based on supercapacitors in the context of grid-connected microgrids. The ESS is composed of ac/dc and dc/dc converters tied by a dc link. A single sliding mode strategy is proposed to control a bidirectional dc/dc converter, capable of working properly under all operating conditions. The switching devices are commanded by a single sliding function, dynamically shaped by references sent from the microgrid central controller. This feature facilitates the implementation and design of the control law and simplifies the stability analysis over the entire operating range. The effectiveness of the proposed control strategy is illustrated by experimental results. © 1986-2012 IEEE.


Barth S.,Tyndall National Institute | Barth S.,Trinity College Dublin | Hernandez-Ramirez F.,Catalonia Institute for Energy Research IREC | Holmes J.D.,Tyndall National Institute | And 2 more authors.
Progress in Materials Science | Year: 2010

Nanoscale inorganic materials such as quantum dots (0-dimensional) and one-dimensional (1D) structures, such as nanowires, nanobelts and nanotubes, have gained tremendous attention within the last decade. Among the huge variety of 1D nanostructures, semiconducting nanowires have gained particular interest due to their potential applications in optoelectronic and electronic devices. Despite the huge efforts to control and understand the growth mechanisms underlying the formation of these highly anisotropic structures, some fundamental phenomena are still not well understood. For example, high aspect-ratio semiconductors exhibit unexpected growth phenomena, e.g. diameter-dependent and temperature-dependent growth directions, and unusual high doping levels or compositions, which are not known for their macroscopic crystals or thin-film counterparts. This article reviews viable synthetic approaches for growing high aspect-ratio semiconductors from bottom-up techniques, such as crystal structure governed nucleation, metal-promoted vapour phase and solution growth, formation in non-metal seeded gas-phase processes, structure directing templates and electrospinning. In particular new experimental findings and theoretical models relating to the frequently applied vapour-liquid-solid (VLS) growth are highlighted. In addition, the top-down application of controlled chemical etching, using novel masking techniques, is described as a viable approach for generating certain 1D structures. The review highlights the controlled synthesis of semiconducting nanostructures and heterostructures of silicon, germanium, gallium nitride, gallium arsenide, cadmium sulphide, zinc oxide and tin oxide. The alignment of 1D nanostructures will be reviewed briefly. Whilst specific and reliable contact procedures are still a major challenge for the integration of 1D nanostructures as active building blocks, this issue will not be the focus of this paper. However, the promising applications of 1D semiconductors will be highlighted, particularly with reference to surface dependent electronic transduction (gas and biological sensors), energy generation (nanomechanical and photovoltaic) devices, energy storage (lithium storage in battery anodes) as well as nanowire photonics. © 2010 Elsevier Ltd. All rights reserved.


Shavel A.,Catalonia Institute for Energy Research IREC | Cadavid D.,Catalonia Institute for Energy Research IREC | Ibanez M.,University of Barcelona | Carrete A.,Catalonia Institute for Energy Research IREC | And 2 more authors.
Journal of the American Chemical Society | Year: 2012

A procedure for the continuous production of Cu 2ZnSnS 4 (CZTS) nanoparticles with controlled composition is presented. CZTS nanoparticles were prepared through the reaction of the metals' amino complexes with elemental sulfur in a continuous-flow reactor at moderate temperatures (300-330 °C). High-resolution transmission electron microscopy and X-ray diffraction analysis showed the nanocrystals to have a crystallographic structure compatible with that of the kesterite. Chemical characterization of the materials showed the presence of the four elements in each individual nanocrystal. Composition control was achieved by adjusting the solution flow rate through the reactor and the proper choice of the nominal precursor concentration within the flowing solution. Single-particle analysis revealed a composition distribution within each sample, which was optimized at the highest synthesis temperatures used. © 2012 American Chemical Society.

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