Últimos itens adicionados do Acervo: Laboratório Nacional de Energia e Geologia

O Laboratório Nacional de Energia e Geologia (LNEG) é uma instituição de I&D orientada para responder às necessidades da sociedade e das empresas. Apostando numa investigação sustentável e para a sustentabilidade através da geração do conhecimento em Portugal.

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‣ Prevenção de resíduos numa perspetiva de minimização de custos dos desperdícios: estudo de caso numa empresa de curtumes

Nogueira, C. A.; Silva, Nuno; Oliveira, Paula C.
Fonte: Publindústria Publicador: Publindústria
Tipo: Artigo de Revista Científica
Publicado em //2015 Português
A prevenção de resíduos é uma das ferramentas de ecoeficiência dos processos industriais. No âmbito do projeto PRERESI, desenvolveram-se metodologias de abordagem à prevenção na ótica do “zero de resíduos”, privilegiando a contabilização dos desperdícios por operação unitária e as perdas económicas a eles associadas. A hierarquização das operações por relevância permite identificar oportunidades de intervenção para obter melhorias, nomeadamente diminuindo desperdícios e potenciando benefícios económicos. Este artigo descreve sucintamente a aplicação desta metodologia a uma empresa do setor dos curtumes.

‣ The influence of the textural properties of activated carbons on acetaminophen adsorption at different temperatures

Galhetas, M.; Andrade, Marta A.; Mestre, A. S.; Kangni-foli, Ekoé; Brito, Maria J. Villa de; Pinto, Moisés L.; Lopes, M. Helena; Carvalho, A. P.
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
Publicado em //2015 Português
The influence of temperature (20–40 °C) on the acetaminophen adsorption onto activated carbons with different textures was studied. Different temperature dependences, not explained by kinetic effects, were observed for carbons with different micropore size distribution patterns: adsorption capacity increased for pine gasification residues (Pi-fa) derived carbons and decreased for sisal based materials. No significant variation was seen for carbon CP. The species identified by 1H NMR spectroscopy on the back-extraction solution proved that during the adsorption process exist the conditions required to promote the formation of acetaminophen oligomers which have constrained access to the narrow microporosity. The rotation energy of the dihedral angle between monomers (estimated by electronic DFT methods) showed that conformations in the planar form are less stable than the non-planar conformation (energy barrier of 70 and 23 kJ mol-1), but have critical dimensions similar to the monomer and can access most of the micropore volume. The enthalpy change of the overall process showed that the energy gain of the system (endothermic) for Pi-fa samples (˜40 kJ mol-1) was enough to allow a change in the dimer, or even a larger oligomer...

‣ New dual-stage pH control fed-batch cultivation strategy for the improvement of lipids and carotenoids production by the red yeast Rhodosporidium toruloides NCYC 921

Dias, Carla; Sousa, Sofia; Caldeira, João; Reis, Alberto; Silva, Teresa Lopes da
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2015 Português
The optimal medium pH to produce biomass and fatty acids by the red yeast Rhodosporidium toruloides NCYC 921 is 4.0, and to produce carotenoids is 5.0. Based on this difference, a dual-stage pH control fed-batch cultivation strategy for the enhancement of lipids and carotenoids production by this yeast was studied. The results showed that when the yeast growth phase was conducted at pH 4.0, and the products accumulation phase was conducted at pH 5.0, biomass, total fatty acid and total carotenoid productivities were significantly improved comparing with the yeast fed batch cultivations carried out at fixed medium pH (4 or 5). Under dual-stage pH control conditions, the biomass, carotenoids and lipids productivities attained 2.35 g/L h, 0.29 g/L h and 0.40 g/L h, respectively. It was also observed that the oxygen played a major role in the yeast carotenoid production.

‣ Synthesis of new azole phosphonate precursors for fuel cells proton exchange membranes

Teixeira, Fátima C.; Rangel, C. M.; Teixeira, A. P. S.
Fonte: Wiley Publicador: Wiley
Tipo: Artigo de Revista Científica
Publicado em //2015 Português
Herein we present the synthesis and characterization of new phosphonate-, bisphosphonate- and hydroxybisphosphonatebenzimidazole derivatives substituted at the N-1 position and new regioisomers phosphonate-, bisphosphonate-, and hydroxybisphosphonatebenzotriazole derivatives substituted at N-1 or N-2 positions. The compounds were characterized by NMR and IR spectroscopies, and mass spectrometry (low and high resolution) allowing the assignment of their structure, including the identification of regioisomers. These new azole monomers will be precursors for a mesoporous silica host to produce novel membrane materials with high proton conductivity for intermediate temperature proton exchange membrane fuel cells.

‣ Memórias do carvão : Jornadas Internacionais : resumos

Brandão, José Manuel
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Livro
Publicado em //2014 Português
Resumos das comunicações apresentadas nas jornadas realizadas na Batalha - Porto de Mós, de 11 a 13 de Setembro de 2014

‣ Energy storage for wind integration: hydropower and other contributions

Estanqueiro, Ana; Ardal, Atle Rygg; O'Dwyer, Ciara; Flynn, Damian; Huertas-Hernando, Daniel; Lew, Debra; Gomez-Lázaro, E.; Ela, Erik; Revuelta, Javier; Kiviluoma, J.; Rodrigues, L.; Amelin, Mikael; Holttinen, Hannele
Fonte: IEEE - Institute of Electrical and Electronics Engineers Publicador: IEEE - Institute of Electrical and Electronics Engineers
Tipo: Conferência ou Objeto de Conferência
Publicado em //2012 Português
The amount of wind power and other timevariable non-dispatchable renewable energy sources (RES) is rapidly increasing in the world. A few power systems are already facing very high penetrations from variable renewables which can surpass the systems’ consumption during no-load periods, requiring the energy excess to be curtailed, exported or stored. The limitations of electric energy storage naturally lead to the selection of the well-known form of storing potential energy in reservoirs of reversible hydropower stations, although other technologies such as heat storage are also being used successfully. This paper reviews the storage technologies that are available and may be used on a power system scale and compares their advantages and disadvantages for the integration of fast-growing renewables, such as wind power, with a special focus on the role of pumped hydro storage.

‣ Design and operation of power systems with large amounts of wind power, IEA collaboration

Holttinen, Hannele; Meibom, Peter; Ensslin, Cornel; Hofmann, Lutz; McCann, John; Pierik, Jan; Tande, John O.; Hagstrom, Espen; Estanqueiro, Ana; Amaris, Hortensia; Soder, Lennart; Strbac, Goran; Parsons, Brian
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2006 Português
New R&D collaboration on 'Design and Operation of Power Systems with Large Amounts of Wind Power Production' has been formed in IEA Wind. The R&D task will collect and share information on the experience gained and the studies made on power system impacts of wind power, and review methodologies, tools and data used. This paper outlines the power system impacts of wind power, the national studies published and on-going and describes the goals of the international collaboration. There are dozens of studies made and ongoing related to cost of wind integration, however, the results are not easy to compare. An in-depth review of the studies is needed to draw conclusions on the range of integration costs for wind power. State-of-the art review process will seek for reasons behind the wide range of results for costs of wind integration-definitions for wind penetration, reserves and costs; different power system and load characteristics and operational rules; underlying assumptions on variability of wind etc.

‣ Design and operation of power systems with large amounts of wind power, first results of IEA collaboration

Holttinen, Hannele; Meibom, Peter; Orths, Antje; Hulle, Frans van; Ensslin, Cornel; Hofmann, Lutz; McCann, John; Pierik, Jan; Tande, John O.; Estanqueiro, Ana; Soder, Lennart; Strbac, Goran; Parsons, Brian; Smith, J. Charles; Lemstrom, Bettina
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2006 Português
An international forum exchange of knowledge of power systems impacts of wind power has been formed under the IEA Implementing Agreement on Wind Energy. The task 'Design and Operation of Power Systems with Large Amounts of Wind Power Production' will analyse existing case studies from different power systems. There is a multitude of studies made and ongoing related to cost of wind integration. However, the results are not easy to compare. This paper summarises the results from 10 countries and outlines the sudies made at European Wind Energy Association and the European system operators UCTE and ETSO. A more in-depth review of the studies is needed to draw conclusions on the range of integration costs for wind power. State-of-the art review process will seek for reasons behind the wide range of results for costs of wind integration-definitions for wind penetration, reserves and costs; different power system and load characteristics and operational rules; underlying assumptions on variability of wind etc.

‣ Dynamic models of wind farms for power system studies: status by IEA Wind R&D Annex 21

Tande, John O.; Muljadi, Eduard; Carlson, Ola; Pierik, Jan; Estanqueiro, Ana; Sorensen, Poul; O'Malley, Mark; Mullane, Alan; Anaya-Lara, Olimpo; Lemstrom, Bettina
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2004 Português
Dynamic models of wind farms for power system studies are at present not a standard feature of many software tools, but are being developed by research institutes, universities and commercial entities. Accurate dynamic wind farm models are critical; hence model validation is a key issue and taken up by IEA Wind R&D Annex 21. This international working group includes participants from nine countries, and has since start-up in 2002 developed a systematic approach for model benchmark testing. This paper present this methodology, including example benchmark test results, but also gives an overview of the various wind farm models now being available from both Annex partners and external entities.

‣ Nato SfS Project Po-Mistral: Status of the experimental validation phase

Castro, Rui; Estanqueiro, Ana; Saraiva, J. A. Gil; Gomes, Luís; Jesus, J.M. Ferreira
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //1996 Português

‣ A wind park grid integration model for power quality assessment

Estanqueiro, Ana; Jesus, J.M. Ferreira; Saraiva, J. A. Gil
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //1996 Português

‣ Projecto NATO SfS Po-MISTRAL: Estado actual de desenvolvimento 

Castro, Rui; Estanqueiro, Ana; Saraiva, J. A. Gil; Gomes, Luís; Oliveira, Luis; Jesus, J.M. Ferreira
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //1996 Português

‣ Including a wind energy conversion system model in electromagnetic transients program

Reis, Francisco A.G.S; Estanqueiro, Ana; Castro, Rui; Jesus, J.M. Ferreira
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //1995 Português
Due to the increasing penetration of wind energy, it is necessary to posses design tools that are able to simulate the impact of these installation in distribution grids. Electromagnetic transients programs are suited to deal with these problems, but a detailed wind energy converter model which is able to carry the transient behaviour of this system is also required. In this paper, an interface between two available software package, EMTP and INDUSAT, containing the digital implementation of these features, is presented. This tool will enable the assessment of the influence that both voltage flickering and power oscillations may have in the performance of distribution networks in face of dispersed wind production. A simple case-study is discussed and the main conclusions are commented.

‣ The development and application of a model for power output in a wind park

Estanqueiro, Ana; Aguiar, Ricardo; Saraiva, J. A. Gil; Castro, Rui; Jesus, J.M. Ferreira
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //1993 Português

‣ WEC'S unsteady power output simulation

Estanqueiro, Ana; Jesus, J.M. Ferreira; Saraiva, J. A. Gil
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //1993 Português
A numerical method for the simulation of horizontal axis wind turbines (HAWT) was developed. Time-variable wind velocity, and induction generators in steady and transient states, conneted to the utility grid (SEE) were considered.

‣ Synthesis and characterization of new benzimidazole phosphonates for hybrid materials for cell application

Teixeira, Fátima C.; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 Português
Fuel cells are electrochemical devices that convert the chemical energy stored in a fuel, directly and efficiently into electrical energy and are a promising and clean alternative to traditional energy fuels [1]. The roton-exchange membrane fuel cells (PEMFCs) are considered a promising type of electrochemical device for power generation. The proton exchange membrane (PEM) is a key part for the operation of PEMFC. Usually, the proton exchange membranes are made of organic polymers containing acidic functionalities (ex. Nafion®), but the proton transport properties of these membranes strongly depend on their water content and, consequently, limit their operation temperatures up to 90ºC. These limitations have fostered the interest in research and development of new alternative membranes [1]. Phosphonic acids are considered to be promising proton carriers due to their good proton donating and accepting properties, furthermore they present better thermal stabilities than sulfonic acids [2]. This work reports on the synthesis and characterization of a series of mono-, bis- and trisbenzimidazole phosphonates derivatives, prepared from the new diaminebenzene diphosphonate, by cyclization with diferents reagents. These benzimidazole phosphonates derivatives were prepared by a new strategy which involves nickel-catalyzed Arbuzov reaction of 4...

‣ Influence of the electrolyte on the electrochemical performance of a polyimide material for electrodes in rechargeable batteries

Furtado, Olívia; Paiva, T. I.; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 Português
The charge storage on organic polymers has led to increasing application of these new materials such as active electrodes in rechargeable batteries [1, 2]. Taking advantage of the redox properties of aromatic polyimide imide group [3], which allows it to be electrochemically oxidized and reduced reversibly, we will present the advances made on the electrochemical studies carried out with a polyimide derivative electrode material towards the constitution of a new battery. Previous studies by the authors with a poliimide derivative [4]using cyclic voltammetry have shown their significant redox capacity to be applied as an alternative material for energy storage in rechargeable batteries. Furthermore, the use of polyimide is considered safe owing to this type of polymer not being flammable and having an excellent thermal stability and high mechanical strength. Since the polyimide is hydrolyzable, its use can be considered environmentally favorable. Attempts to use composite poliimides through solvent blending methodologies lead to poor dispersion of the polymer in the composite mixture. In situ polymerization techniques were well succeed with added incorporation of carbon fibre with the poliimide precursor. Research is in progress with studies with different electrolytes and polyimide composite in order to ensure an efficient lithium ion exchange and obtain batteries with satisfying energy performance. Advances made will be presented herein.

‣ Gold deposition from 1-butyl-1-methyl-pyrrolidinium dicyanamide ionic liquid at open-circuit and under potentiostatic control

Sá, A. I. Correia de; Eugénio, S.; Quaresma, S.; Rangel, C. M.; Vilar, R.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
In this work, the deposition of gold on copper substrates from solutions of HAuCl4.3H2O in 1-butyl-1-methylpyrrolidinium dicyanamide was studied. Deposition was carried out in open-circuit and under potentiostatic control at temperatures from 293 to 353 K, in normal atmosphere, with deposition conditions allowing water from atmospheric absorption up to 0.8 wt.%. Films of gold were obtained by both methods. Deposition at open-circuit occurs by galvanic displacement mechanism. Involvement of Cu+ species in the electrodeposition process was suggested by cyclic voltammetry. Furthermore, copper incorporation in the gold films was confirmed by X-ray diffraction. SEM observation and XRD analysis show that films are nanocrystalline with a globular morphology except for the films formed under potentiostatic control at 353 K, which show a dendritic structure. The size of the crystallites determined by Scherrer's equation varies in the range from 6 to 25 nm.

‣ EIS diagnostics of aged Li-ion batteries

Plancha, Maria João; Luz, Paulo P. da; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 Português
High-power batteries with long cycling life and adequate storage behaviour are needed as energy sources devices for (hybrid) electric vehicles and lithium-ion rechargeable cells are the most promising candidates. In this work, Li-ion cells with a nominal capacity of 10 Ah were studied. Electrochemical impedance spectroscopy (EIS) was used for studying the cycling ageing effect on discharge capacity fade. EIS measurements were conducted in a galvanostatic mode, by means of a Solartron Electrochemical Interface 1286 and a Solartron FRA 1250 controlled by Zplot from Scribner Associates. Scanning frequency ranged from 600 Hz to 0.005 Hz and the ac amplitude was set to 100 mA. An equivalent circuit complex non-linear least squares fitting procedure was used for spectra analyses. Cell charge transfer and film resistances were estimated at several cycle life stages and its evolution on cycle number was analysed. Capacity losses were estimated after 300, 600 and 1200 cycles at C/1 discharge rate and were found to be 5.8, 7.5 and 16.8% of the initial capacity, respectively. EIS data revealed that the major factor responsible for the observed capacity fade was the cell’s charge transfer resistance (Rct) increase following the opposite tendency of the discharge capacity values with cycle number. Very little change can be attributed to film resistances as a result of ageing by cycling. The SEI layer thickness appeared to increase from 0 to 300 cycles remaining almost constant up to 1200 cycles. The effect of a high storage temperature on the performance of the sealed commercial batteries was evaluated by means of discharge capacity measurements and impedance behaviour. The thermal ageing conditions were applied over time and the results were interpreted taking into account the cell’s state of charge (SOC). Before storage at 45 oC...

‣ Characterisation and performance studies of a LiFePO4 cathode material synthesized by microwave heating 

Plancha, Maria João; Paiva, T. I.; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 Português
Lithium iron phosphate with incorporated carbon, LiFePO4-C, was synthesized by the microwave-assisted method. X-ray diffraction analyses showed higher crystallization degrees for samples submitted to higher irradiation times. A particle-agglomerated morphology was associated as revealed by scanning electron microscopy. The electrochemical character-istics of a composite cathode containing the synthesized product were evaluated. The two-phase electrochemical process between FePO4 and LiFePO4 was evidenced in the cycling voltammogram profile and its reversibility and stability were demonstrated. An additional redox reversible reaction was revealed and assigned to another phosphate present in the synthesized product. The charge/discharge performance study indicated a good capacity retention after the initial cy-cles where capacity fading was associated to the resistance of a SEI film that forms and grows on the cathode’s surface. Results obtained by electrochemical impedance analysis before and after cell’s cycling are discussed.