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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‣ Saccharomyces cerevisiae and Dekkera bruxellensis interactions in alcoholic fermentations: growth and 4-ethylphenol production

Coutinho, Rute; Branco, Patrícia; Monteiro, Margarida; Malfeito-Ferreira, M.; Albergaria, Helena
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 yeast Dekkera/Brettanomyces bruxellensis can cause enormous economic losses both in wine industry and fuel-ethanol processes due to production of phenolic off-flavour compounds and low ethanol productivities. In winemaking this microbial hazard is usually tackled by the use of chemical preservatives such as sulphur dioxide. In spite of this, D. bruxellensis strains are frequently found in wines at low levels (ca 103 cells/ml) where they can metabolise residual sugars producing phenolic off-flavours compounds, such as 4-ethyl phenol. In the present work we investigated S. cerevisiae and D. bruxellensis interactions during alcoholic fermentations and evaluated the effectiveness of antimicrobial peptides secreted by S. cerevisiae to prevent growth of the main wine spoilage yeast and the production of 4-ethylphenol. Several fermentations were performed with single cultures of D. bruxellensis and mixed cultures of S. cerevisiae and D. bruxellensis, both in synthetic grape juice (SGJ) and grape must. Yeast growth (culturability and viability) and fermentation performance (i.e. sugars consumption, ethanol and 4-ethylphenol production) of those fermentations was accessed by different methods, namely by florescence in situ hybridization and flow cytometry. Results showed that S. cerevisiae significantly reduced the growth of D. bruxellensis and the production of 4-ethylphenol both in SGJ and grape must fermentations performed with mixed cultures. Moreover...

‣ Interactions between Saccharomyces cerevisiae and Hanseniaspora guilliermondii: cell-cell contact mechanism

Branco, Patrícia; Kemsawasd, Varongsiri; Arneborg, Nils; Albergaria, Helena
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 Português
Several studies have shown that the early death of non-Saccharomyces during wine fermentations are due to yeast-yeast interactions induced by Saccharomyces cerevisiae (Sc) through different mechanisms such as growth arrest mediated by a cell-cell contact mechanism (Nissen et al. 2003) and death mediated by killer-like toxins (Pérez-Nevado et al 2006; Albergaria et al. 2010). Besides, previous work also showed that death of non-Saccharomyces in co-cultivation with Sc is always triggered at the end of exponential growth phase (Pérez-Nevado et al 2006). In order to investigate the role of cell-cell contact in the early death of non-Saccharomyces, we performed assays in which Sc cells pre-grown at enological growth conditions for 12 and 48 h, respectively, were in direct contact with Hanseniaspora guilliermondii (Hg) cells at high cellular density (107-108 cells/ml) in a carbon-free medium. As a negative control we performed similar assays in which Sc and Hg cells were separated by a dialysis tube (pore cut-off of 1000 kDa) and as a positive control a single Hg culture. Results showed that Hg cell density decreased by 2 orders of magnitude (i.e. from 108-106 cells/ml) in contact with 48 h-grown Sc cells, while its viability remained unchanged (108cfu/ml) in the presence of 12 h-grown Sc cells. Moreover...

‣ Applications of PCMs

Solé, Cristian; Kalagirou, Soteris; Navarro, Lidia; Gracia, Alvaro de; McCormack, Sarah; Hasan, Ahmad; Aelenei, Laura; Ostry, Milan; Georgiev, Aleksandar; Popov, Rumen; Bottarelli, Michele; Griffiths, Philip; O'Brien, Vicent
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Parte de Livro
Publicado em //2013 Português
This section will consider a number of applications of phase change materials. The work was compiled as part of the applications working group of TU0802. This chapter is a précis of the work which can be read in detail in the deliverables published by the COST action.

‣ Contribution of energy storage for large-scale integration of variable generation

Estanqueiro, Ana; Ardal, Atle Rygg; O'Dwyer, Ciara; Flynn, Damian; Huertas-Hernando, Daniel; Lew, Debra; Gomez-Lázaro, E.; Carlini, Enrico M.; Solvang, Eivind; Ela, Erik; Kiviluoma, J.; Rodrigues, L.; Amelin, Mikael
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2012 Português
The amount of wind power and other timevariable non-dispatchable renewable energy sources (VRES) such as photovoltaics (PV) is rapidly increasing in the world. Several power systems in Europe are already facing a very high penetration from variable renewables which is posing concerns on the operational stability limits that are being surpassed for extreme RES generation conditions. Most transmission system operators are defining VRES limits of penetration, thus, requiring the renewable energy excess to be curtailed, exported or stored. Energy storage may play a relevant role in maximizing the long term penetration of VRES if used as a technical mean to regulate the daily, weekly and annual profiles of variable generation (VG). This paper reviews the storage technologies that are available and may be used on a power system scale and performs a cost/benefit analysis discussing their advantages and disadvantages for the integration of fastgrowing renewables, such as wind power and PV.

‣ Regulation of the wind power production: contribution of the electric vehicles and other energy storage systems

Mateus, C. B.; Estanqueiro, Ana
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2012 Português
The increase in penetration of variable renewable energy sources (RES) introduced additional difficulties regarding the management of the Portuguese Power System. This is mainly due to the high temporal variability and low controllability, characteristics of these kinds of sources. There is a real need to reduce the impact of non-dispatchable RES sources; maximizing their penetration and minimizing curtailment. This is especially true for the wind power and run-of-the-river hudro (ROR); as it appears beneficial to combine their variable production with added capacity of energy storage and demand side management; thereby increasing the flexibility of the power system as a whole. This paper aims to assess the excess wind generation (and other non-dispatchable sources); this for periods of production's excess in a 2020 timeframe, and assuming different weather scenarios. The adjustment of wind power generation (WPG) profile to the load prfile is also addressed; the result is computed in the form of the value of the energy temporally deferred, using Pumped Hydro Storage (PHS) power plants as well as electric Vehicles (EVs)

‣ Assessment of PV and wind microgeneration's impact in the power quality of low and medium voltage distribution networks

Bonifácio, Paulo; Viana, Susana; Rodrigues, L.; Estanqueiro, Ana
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2012 Português
Electric power systems face an ever-growing penetration (PV) and other microgeneration as well as non-linear loads such as electric vehicles. This is a common link between these : the extensive use of power electronics converters. These devices are a source of medium-to-high frequency harmonic distortion and their impact on the local distribution grid must be carefully assessed in order to evaluation possible network unbalances, demaging power line resonance conditions, transformer core saturation and overhearing.

‣ Assessment of PV and wind microgeneration's impact in the power quality of low and medium voltage distribution networks

Bonifácio, Paulo; Rodrigues, L.; Viana, Susana; Estanqueiro, Ana
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2012 Português

‣ Transmission planning for wind energy in the United States and Europe: status and prospects

Smith, J. Charles; Osborn, D.; Zavaldi, R.; Lasher, W.; Gomez-Lázaro, E.; Estanqueiro, Ana; Trotscher, Thomas; Tande, J.; Korpas, M.; Van Hulle, Frans; Holttinen, Hannele; Orths, Antje; Burke, Daniel; O'Malley, Mark; Dobschinski, J.; Rawn, B.; Gibescu, M
Fonte: John Wiley & Sons Publicador: John Wiley & Sons
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
This paper provides an overview ofmajor transmission planning activities related to wind integration studies in the United States and Europe. Transmission planning for energy resources is different from planning for capacity resources. Those differences are explained, and illustrated with examples from several regions of the United States and Europe. Transmission planning for wind is becoming an iterative process consisting of generation expansion planning, economic-based transmission planning, system reliability analysis, and wind integration studies. A brief look at the policy environment in which this activity is taking place is provided. A set of coherent and collaborative transmission planning, siting, and permitting policies and cost allocation method must be developed to achieve the intended objectives. The scale of transmission development envisioned for this purpose will require unprecedented cooperation across multiple jurisdictional boundaries.

‣ Experience and challenges with short-term balancing in european systems with large share of wind power

Soder, Lennart; Abildgaard, Hans; Estanqueiro, Ana; Hamon, Camile; Holttinen, Hannele; Lannoye, E.; Gomez-Lázaro, E.; O'Malley, Mark; Zimmermann, Uwe
Fonte: IEEE - Institute of Electrical and Electronics Engineers Publicador: IEEE - Institute of Electrical and Electronics Engineers
Tipo: Artigo de Revista Científica
Publicado em //2012 Português
The amount of wind power in the world is quickly increasing. The background for this development is improved technology, decreased costs for the units, and increased concern regarding environmental problems of competing technologies such as fossil fuels. Some areas are starting to experience very high penetration levels of wind and there have been many instances when wind power has exceeded 50% of the electrical energy production in some balancing areas. The aims of this paper are to show the increased need for balancing, caused by wind power in the minutes to hourly time scale, and to show how this balancing has been performed in some systems when the wind share was higher than 50%. Experience has shown that this is possible, but that there are some challenges that have to be solved as the amount of wind power increases.

‣ Impacts of large amounts of wind power on design and operation of power systems, results of IEA collaboration

Holttinen, Hannele; Meibom, Peter; Orths, Antje; Lange, Bernhard; O'Malley, Mark; Tande, John O.; Estanqueiro, Ana; Gomez, Emilio; Soder, Lennart; Strabac, Goran; Smith, J. Charles; Van Hulle, Frans
Fonte: John Wiley & Sons Publicador: John Wiley & Sons
Tipo: Artigo de Revista Científica
Publicado em //2011 Português
There are dozens of studies made and ongoing related to wind integration. However, the results are not easy to compare. IEA WIND R&D Task 25 on ‘Design and Operation of Power Systems with Large Amounts of Wind Power’ collects and shares information on wind generation impacts on power systems, with analyses and guidelines on methodologies. In the state-of-the-art report (October, 2007), and the fi nal report of the 3 years period (July, 2009) the most relevant wind power grid integration studies have been analysed especially regarding methodologies and input data. Several issues that impact on the amount of wind power that can be integrated have been identifi ed. Large balancing areas and aggregation benefi ts of wide areas help in reducing the variability and forecast errors of wind power as well as help in pooling more cost effective balancing resources. System operation and functioning electricity markets at less than day-ahead time scales help reduce forecast errors of wind power. Transmission is the key to aggregation benefi ts, electricity markets and larger balancing areas. Best practices in wind integration studies are described. There is also benefi t when adding wind power to power systems: it reduces the total operating costs and emissions as wind replaces fossil fuels and this should be highlighted more in future studies.

‣ Design and operation of power systems with large amounts of wind power : Final report, Phase one 2006-08, IEA WIND Task 25

Holttinen, Hannele; Meibom, Peter; Orths, Antje; Van Hulle, Frans; Lange, Bernhard; O'Malley, Mark; Smith, J. Charles; Estanqueiro, Ana; Ricardo, João; Ummels, Bart C.; Gomez, Emilio; Matos, M.; Soder, Lennart; Shakoor, Anser; Strbac, Goran; Tande, John
Fonte: VTT Publicador: VTT
Tipo: Livro
Publicado em //2009 Português
There are already several power systems coping with large amounts of wind power. High penetration of wind power has impacts that have to be managed through proper plant interconnection, integration, transmission planning, and system and market operations. This report is a summary of case studies addressing concerns about the impact of wind power s variability and uncertainty on power system reliability and costs. The case studies summarized in this report are not easy to compare due to different methodology and data used, as well as different assumptions on the interconnection capacity available. Integration costs of wind power need to be compared to something, like the production costs or market value of wind power, or integration cost of other production forms. There is also benefit when adding wind power to power systems: it reduces the total operating costs and emissions as wind replaces fossil fuels. Several issues that impact on the amount of wind power that can be integrated have been identified. Large balancing areas and aggregation benefits of large areas help in reducing the variability and forecast errors of wind power as well as help in pooling more cost effective balancing resources. System operation and working electricity markets at less than day-ahead time scales help reduce forecast errors of wind power. Transmission is the key to aggregation benefits...

‣ Design and operation of power systems with large amounts of wind power: State of the art report

Holttinen, Hannele; Lemstrom, Bettina; Meibom, Peter; Bindner, Henrik; Orths, Antje; Van Hulle, Frans; Ensslin, Cornel; Tiedemann, Albrecht; Hofmann, Lutz; Winter, Wilhelm; Tuohy, Aidan; O'Malley, Mark; Smith, Paul; Pierik, Jan; Tande, John O.; Estanqueir
Fonte: VTT Publicador: VTT
Tipo: Livro
Publicado em //2007 Português
High penetration of wind power has impacts that have to be managed through proper plant interconnection, integration, transmission planning, and system and market operations. This report is a summary of case studies addressing concerns about the impact of wind powers variability and uncertainty on power system reliability and costs. The case studies summarized in this report are not easy to compare due to different methodology and data used, as well as different assumptions on the interconnection capacity available. Integration costs of wind power need to be compared to something, like the production costs or market value of wind power, or integration cost of other production forms. There is also benefit when adding wind power to power systems: it reduces the total operating costs and emissions as wind replaces fossil fuels. Several issues that impact on the amount of wind power that can be integrated have been identified. Large balancing areas and aggregation benefits of large areas help in reducing the variability and forecast errors of wind power as well as help in pooling more cost effective balancing resources. System operation and working electricity markets at less than day-ahead time scales help reduce forecast errors of wind power. Transmission is the key to aggregation benefits...

‣ Dye-sensitized 1D anatase TiO2 nanorods for tunable efficient photodetection in the visible range

Parreira, P.; Torres, Erica; Nunes, Clarisse; Carvalho, C. Nunes de; Lavareda, G.; Amaral, A.; Brites, Maria João
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2012 Português
TiO2 films with enhanced photosensitivity were deposited on alkali free glass substrates without intentional substrate heating by pulsed DC magnetron reactive sputtering with an average thickness of about 2 μm. Three dyes, commercial N719 and two new organic dyes were impregnated in order to control the optical spectral selectivity of such films. The type of dye used proved to dramatically influence the device's response to radiation pulses. The practical breakthrough is the use of different dyes according to the region of the electromagnetic spectrum one wants to detect. Devices with photocurrent 6 orders of magnitude higher than the dark current (from ∼2 × 10−12 to 2 × 10−6 A for a 100 V bias) were fabricated with a spectral response within the visible range of the electromagnetic spectrum. In addition, this approach is likely to allow for the fabrication of hybrid photodetectors on cheap heat sensible flexible polymeric substrates.

‣ Detrital zircons from a Late Palaeozoic accretionary complex of SW Iberia (Variscan Belt) : history of crustal growth and recycling at the Rheic convergent margin

Pereira, Manuel Francisco Costa; Drost, K.; Chichorro, Martim; Silva, J. Brandão; Solá, Ana Rita
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /05/2012 Português

‣ Geologia da região de Barrancos : a transversal de Barrancos - Santo Aleixo da Restauração

Piçarra, José Manuel
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /03/2012 Português

‣ New VMS exploration potential to the SE of Neves-Corvo mine, Iberian Pyrite Belt, Portugal

Rosa, Diogo R. N.; Inverno, Carlos; Rosa, Carlos J. P.; Pereira, Zélia; Andersen, T.; Oliveira, José Tomás; Matos, João Xavier
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /05/2012 Português

‣ Iberian Sea surface temperature calibration based in Alkenones paleotemperature index Uk'

Rodrigues, Teresa; Rufino, M.; Santos, C.; Salgueiro, Emília; Abrantes, Fátima; Oliveira, P.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /12/2012 Português

‣ Utilização de metodologias integradas na produção da carta ambiental da cidade da Beira, Moçambique: resultados preliminares

Fernandes, Judite; Batista, Maria João; Ramalho, Elsa Cristina; Quental, Lídia Maria; Dias, Ruben P.; Oliveira, José Tomás; Cune, Grácio; Daudi, Elias X.; Melisse, Dino; Ussene, Ussene; Manhiça, Vítor
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /03/2010 Português

‣ Reservas estratégicas de água subterrânea na região centro, Projecto Images

Melo, Maria Teresa Condesso de; Fernandes, Judite; Midões, Carla; Almeida, Carlos Costa; Amaral, Helena; Gomes, Ana Rita; Madruga, Maria José; Silva, Manuel Marques da; Mendonça, João Lopo
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em /03/2010 Português

‣ Thermal Performance of Residential Buildings withe Large Glazing areas in Lisbon - Modelling and Validation

Tavares, Márcia; Gonçalves, Helder; Bastos, Jorge
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2011 Português
This work aims to demonstrate the parameters of both major and minor influence on the thermal performance of units with large glazing areas, whether with one face or two exposed. The study was developed after a two year monitoring campaign in a group of 23 building apartments (the units have more than 60% of the main façades in glazing. The main goal was to carry out a representative model that can be validated by the experimental results in order develop a set of parametric studies for the Lisbon Climate. Part of the modeling included the development of detailed and simplified geometrical models related to the units selected for the study. Different parametric variations were performed (summer and winter) using the detailed and simplified geometrical models. These took into account the characteristics of each housing unit and the conditions under which they were monitored in summer and winter. The thermal simulation software EnergyPlus (with the calculation model present in this software) was used to simulate all solutions and models. Thus, the study allows not only comparison but also the evaluation and validation of the models.