Browsing by Issue Date, starting with "2011"
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- Optimizing the performance of renewable sources using virtual renewable power plantsPublication . Rodrigues, L.; Estanqueiro, AnaThe concept of “Virtual Renewable Power Plants - VRPP” enables several positive factors for the electric integration of Renewable Energy Sources (RES) and enables the optimization of its technical and economic performance by using the natural complementary of renewable resources availability. Moreover, the establishment of synergies between different RES contributes for the smoothing of time based fluctuation of the power delivered by the RES. The present work aims to identify the synergies between wind and photovoltaic (PV) plants, regarding their daily profiles complementarity and resource availability; as well as the technical and economic added value of a VRPP. Results show an increase of 5.3% in the capacity factor and 25% in the revenue when 2 MWp of PV are added to an 8 MW wind farm, and a potential benefit of 48% when adding a storage system of 2 MW (8 MWh), considering all infrastructural capacity limits. Moreover, the combined VRPP daily production profiles have a significantly higher correlation with the average daily load profile (0.82) than WTG (0.41) or PV (0.54) alone.
- Os Scavrarii de VipascaPublication . Pérez Macias, Juan Aurélio; Matos, João Xavier; Martins, Artur
- Impacts of large amounts of wind power on design and operation of power systems, results of IEA collaborationPublication . 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, FransThere 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.
- Requisitos de qualidade em óleos essenciais : a importância das monografias da Farmacopeia Europeia e das normas ISOPublication . Martins, Ana Paula; Nogueira, Teresa; Costa, Maria do Céu; Salgueiro, LígiaOs óleos essenciais são produtos naturais utilizados por diversas indústrias, entre as quais se destacam a indústria alimentar e a indústria farmacêutica. Devido à variabilidade inerente a todos os produtos naturais e também aos crescentes problemas de adulterações, este artigo tem por objectivo divulgar e chamar a atenção da importância das normas internacionais existentes, nomeadamente das monografias da Farmacopeia Europeia e das normas ISO, fazendo simultaneamente uma comparação dos principais requisitos nelas estabelecidos. Só o cumprimento dos requisitos de qualidade e segurança adoptados por este tipo de normas pode garantir que os óleos essenciais utilizados para as mais diversas aplicações tenham a qualidade desejável para o fim a que se destinam e não coloquem problemas de segurança.
- Tintas com incorporação de partículas de cortiça para melhor comportamento térmico e acústicoPublication . Gil, Luís; Marreiros, N.Neste trabalho são referidas novas tintas com incorporação de partículas de cortiça de modo a obter-se um melhor comportamento destas a nível do isolamento térmico e da absorção acústica (reverberação). Estas tintas são obtidas por mistura de tintas correntes para interiores e exteriores de edifícios com partículas de cortiça com diferentes granulometrias e em diferentes proporções. As tintas com cortiça apresentam uma menor condutividade térmica e uma maior absorção acústica (diminuição do eco), conduzindo a um melhor comportamento térmico e acústico quando comparadas com as tintas correntes, contribuindo para uma melhor habitabilidade.
- Environmental management of wastewater treatment plants : the added value of the ecotoxicological approachPublication . Mendonça, E.; Picado, Ana; Cunha, Maria Ana; Catarino, Justina
- Materiais para caldeiras e turbinas de centrais termoeléctricas avançadasPublication . Santos, Dulcínea; Cabrita, Isabel; Gulyurtlu, Ibrahimreduzir a emissão de CO2 para a atmosfera, a qual contribui grandemente para o aquecimento global. Nas centrais termoeléctricas, o aumento da eficiência energética conduz à redução da emissão de CO2. Assim, encontram-se actualmente em desenvolvimento unidades produtoras de energia através da queima de combustíveis fósseis, com elevada eficiência energética, com funcionamento a uma pressão do vapor de cerca de 35 MPa e a uma temperatura do vapor até cerca de 760ºC, com custos de produção de energia relativamente baixos e com poluição inferior. As tecnologias avançadas podem ainda proporcionar captura e sequestro de CO2. Contudo, estas tecnologias avançadas aumentam a severidade das condições de funcionamento, requerendo melhoria das características de resistência à corrosão e mecânicas dos materiais em que são fabricados os equipamentos. Numerosos estudos efectuados em aços e ligas resistentes ao calor têm levado a grande aumento das propriedades dos aços com 9-12 % Cr, dos aços austeníticos e das ligas de níquel. Neste artigo referem-se os principais materiais desenvolvidos ou em desenvolvimento para caldeiras e turbinas de centrais termoeléctricas funcionando em condições ultra-supercríticas e ultra-supercríticas avançadas.
- Ordovician VS. "Cambrian" ichnofossils in the Armorican quartzite of central PortugalPublication . Sá, Artur Abreu; Gutiérrez-Marco, Juan Carlos; Piçarra, José Manuel; García-Bellido, Diego C.; Vaz, Nuno; Aceñolaza, Guillermo Florencio
- European round robin test on solar collectors and solar thermal systemsPublication . Fischer, S.; Carvalho, Maria João; Weißmüller, C.Within the European project QAiST (Quality Assurance in Solar Thermal Heating and Cooling Technology)a Round Robin test on solar collectors and solar thermal systems is carried out in the years 2010 and 2011. For two different collector types, one flat plate collector and one evacuated tubular collector with CPC reflector, thermal performance tests according to EN 12975-2 (EN 12975, 2006) are carried out by 12 different test institutes throughout Europe. The two different solar thermal systems, one thermosiphon system and one system with forced circulation are subject to a thermal performance test according to EN 12976-2 (EN 12976, 2006) and are tested by 9 different test institutes.In order to finish the Round Robin test within two years despite of the high number of participants, the following procedure was applied: Each participant received in the year 2010 samples of the two different collector types and of the two solar thermal system types respectively. After testing, the samples have been sent to the next test institute to be tested within the year 2011. Thus all institutes are testing identical collectors and system types taken out of the same production batch, however each unique collector or system is only tested by two institutes. For the first time Round Robin tests on solar thermal products are evaluated by an independent institute (Institut für Eignungsprüfung) using the acknowledged procedures for the evaluation of proficiency tests.This paper presents some of the midterm results of the Round Robin test in an anonymous and standardised way.
- Monitoring rhodotorula glutinis CCMI 145 stress physiological response during fed-batch fermentations using multi-parameter flow cytometryPublication . Silva, Teresa Lopes da; Feijão, Daniela; Reis, AlbertoMulti-parameter flow cytometry was used to monitor R. glutinis stress response during a fed-batch fermentation, through cell viability, lipid content and intrinsic light scatter. During the yeast fermentation, the proportion of cells with permeabilized membrane (dead cells) increased when nutrients and/or oxygen became limiting. Yeast cells showed a higher injury level when grown under other nutrient limitation than under oxygen limiting conditions, as the dead cells reduced their internal content and size in the former situation, suggesting drastic cells lysis. The maximum yeast lipid content was 8% (w/w) at t=38.3 h. Such low lipid content was attributed to oxygen limitation, which highlights the importance of the oxygen transfer rate when producing lipids from aerobic yeast cultures. Changes in Forward and Side scatter light signals were detected during the yeast growth, which can provide a useful and fast way to identify the yeast growth phase. The multi-parameter approach here reported represents a better control system based at the individual cell level that can be used for optimization of yeast bioprocess performance, and may also be used for quick screening of yeast strains for single cell oil production.