ES - Comunicações em actas de encontros científicos internacionais
Permanent URI for this collection
Browse
Browsing ES - Comunicações em actas de encontros científicos internacionais by Title
Now showing 1 - 10 of 34
Results Per Page
Sort Options
- Accelerated aging tests for solar absorber coatingsPublication . Cunha Diamantino, Teresa; Gonçalves, Rita; Páscoa, Soraia; Alves, Isabel Nascimento; Chambino, Teresa; Ferreira, Cristina; Carvalho, Maria JoãoABSTRACT: The need of a higher role of solar energy within the energy mix in the coming decades obliges the systems to increase their performance and reliability. It is demanded that the solar absorbers, as the key component of solar thermal systems, should be low cost with high efficiency for extended lifetimes under different kinds of environments. Commercially, there are two different types of solutions as selective solar absorbers coatings: coatings obtained by physical vapor deposition (PVD) and by paint coatings (PC). These coatings present different physical and chemical characteristics. Therefore, it is important to know how these coatings degrade over time in different environments. Results obtained with two different PVD coatings and three PC, under different accelerated aging tests, are presented. The aging tests performed included different environmental stress corrosion conditions: temperature, humidity, chlorides, sulphur dioxide and nitrogen oxides. Cyclic variation of corrosion promoting gases (sulfur dioxide and nitrogen dioxide), higher humidity, salt spraying and drying seem to be an aging test that reflects the different environments where the solar thermal collectors are exposed. In addition to the contaminants, drying / wetting cycles also play an important role in degradation mechanisms of absorber coatings.
- Aging of elastomeric components of a solar thermal collector under solar radiationPublication . Ferreira, Cristina; Ritto, G.; Cidade, M. T.; Carvalho, Maria João; Cunha Diamantino, TeresaABSTRACT: Elastomeric components play important functions in solar thermal collectors (STC’s) as sealings, fittings or absorbers, being important that they maintain their performance along STC lifetime. However, stress factors such as high temperatures and high levels of solar radiation, as exist in southern Europe countries, can affect the properties of those components. A testing programme for the assessment of elastomeric materials of such components is detailed in international standards (ISO 9808 and ISO 9553), which already considers the effect of heating.
- Arrefecimento exsicante-evaporativo assistido por energia solar: Resultados obtidos com a UTA instalada no DER/INETIPublication . Macau, J.; Ferreira, Pedro; Rodrigues, R.; Mendes, J. FarinhaO Departamento de Energias Renováveis do INETI tem em funcionamento, desde 1999 uma UTA - Unidade de Tratamento de Ar que foi instalada no âmbito de um projecto Europeu (CODEC Project) para demonstração da tecnologia exsicante-evaporativa assistida por energia solar. Recentemente foram introduzidas alterações na configuração da UTA, como seja a introdução de um humidificador na secção de admissão de ar com a subsequente modificação do esquema de controlo, desde o Verão de 2008, para, sem sacrificar as condições de conforto, limitar o tempo de funcionamento da bomba de calor que dá apoio ao sistema quando em modo de arrefecimento. Para além da descrição dos componentes principais, modos de operação e alterações introduzidas, neste trabalho são apresentados e analisados os resultados obtidos nesta nova fase de funcionamento da UTA, depois da introdução daquelas modificações, para concluir acerca do interesse da solução adoptada.
- Assessment of durability of solar absorbers : performance criterionPublication . Páscoa, Soraia; Carvalho, Maria João; Cunha Diamantino, TeresaABSTRACT: Solar fraction, Fs, defined as the ratio between the delivered energy from a solar domestic hot water (DHW) system and the load (thermal energy necessary to satisfy domestic water heating needs), is widely accepted as performance indicator for this type of systems. Considering solar absorptance αs and thermal emittance εt as the most relevant characteristics of solar absorbers, the relation between the depreciation of these optical properties and depreciation of Fs was used by Hollands et al (1992) to define a performance criterion (PC) for assessment of long-term behavior and service life of selective solar absorbers. The PC was established mainly for solar DHW systems working with solar fractions lower than 50%. In this work, systems working with solar fractions higher than 50%, in climates of south of Europe, are considered and the suitability of solar fraction as performance indicator to develop an adequate PC is studied. As a first step simulations of thermal performance of systems using an in-house software were performed for a reduction of 5% and 10% of Fs. In ISO 22975-3, solar fraction Fs degradation must be lower than 5% to guarantee 25 years of service life for DHW system. The results showed that the parameters obtained to define the PC were incoherent considering solar fractions higher than 50%. In a second step, supplied energy was considered as performance indicator and using similar methodology as Hollands et al (1992), but using as performance indicator energy supplied by the solar system, the PC for systems working with solar fractions higher than 50%, in climates of south of Europe, was establish. The results showed that this is not significantly different from the PC considered in ISO 22975-3.
- Avaliação de desempenho de protótipo de secador solar passivo para tratamento de efluente de processo de dessalinização por destilação multi-efeitoPublication . Mendes, J. Farinha; Horta, Pedro; Collares-Pereira, M.; Korovessis, N.O projecto AQUASOL-Enhanced Zero Discharge Seawater Desalination using Hybrid Solar Technology (EVK1-CT2001-00102) teve como principais objectivos a melhoria do desempenho económico e a minimização dos impactes ambientais associados a um processo de dessalinização por Destilação Multi-Efeito (MED)(Blanco et al, 2002). No âmbito do projecto, decorre o estudo de um secador solar passivo utilizado no tratamento do efluente produzido no processo de dessalinização, salmoura, através da sua concentração e/ou através da produção directa de sal a partir do efluente. Nesta etapa adicional do processo de dessalinização foi considerada não só a maior concentração do efluente relativamente à concentração da água marinha utilizada no processo MED, mas também a sua possível integração numa salina tradicional, com o potencial de substituir etapas intermédias da evaporação com vantagem face ao processo convencional de produção de sal marinho. Após um estudo das especificidades da produção de sal em Salinas tradicionais e do processo de evaporação de uma camada de salmoura, a construção e avaliação de cinco configurações distintas de um protótipo preliminar de secador solar passivo, permitiu o desenho final de um secador para a recuperação de sal a partir do efluente do processo MED (Collares Pereira et al, 2004), construido numa salina industrial na ilha de Lesvos (Grécia) (Collares Pereira et al, 2005). Neste artigo serão apresentados os primeiros resultados de operação do protótipo, bem como uma avaliação inicial do seu desempenho.
- Cork wastes as energy sourcesPublication . Gil, Luís; Marques, Isabel PaulaThis work shows the possibility of using cork wastes form cork processing for energy production. In cork processing operations an important waste is produced, cork powder, the main waste of the cork industry, which is estimated to reach over 30000 tons/year. There are various types of cork powders with higher calorific values ranging from 4,000-7,000 Kcal/kg. This powder is commonly burned to produce steam or heat used in the factories themselves, given the high energy content of this material. As an example, a cork company of a large industrial group that produces cork products for construction meets 60% of its energy needs using waste cork. Cork boiling wastewater (CBW) is an aqueous and complex effluent of the cork industry which is produced during the boiling of the cork planks. CBW contains organic materials such as phenolic. This boiling wastewater has no utility, being a serious environmental hazard. Anaerobic digestion is a promising technology for the treatment of organic effluents and for the simultaneous recovery of its energetic potential through methane production. Its application to cork effluents was studied. An anaerobic assay was conducted. The resultant methane potentials were 0.126 - 0.142 m3 CH4 kg-1 COD. The calculated total volume of CBW produced yearly in Portugal is 30 374 m3. As 1 m3 of CBW (6,5 COD kg m-3) in cogeneration can produce in average 1,72 kWh of electric energy and 3,73 kWh of thermal energy, the total CBW volume produced in Portugal in one year corresponds to a total energy value of 165 400 kWh.
- Cork wastes treatment and biogas productionPublication . Gil, Luís; Marques, Isabel PaulaCork industry is an important economic and social sector in the western Mediterranean region. Portugal is the producer and processing leader of this sector. The cork processing industry gives rise to several effluents that must be treated and valorised. This work is a part of a study that aims to develop an integrated process in order to maximize the valorization of the different wastes/effluents of the cork processing sector taking in count the biorefinery concept. The main objective of the present work is to conduct a survey of all operations involve in the cork processing and identify the possible effluents which may be treated and valorise by anaerobic digestion for energy production.
- EU-SOLARIS: The European Research Infrastructure Consortium for CSP TechnologiesPublication . Martinez, Diego; Blanco Galvez, Julian; Zarza, Eduardo; Sánchez-Moreno, Ricardo; Bataille, Francoise; Flamant, Gilles; Georgiou, Marios; Richter, Christoph; Blanco, Manuel; Cardoso, João P.; Horta, Pedro; Canavarro, DiogoABSTRACT: After many years of fruitful collaboration in the field of research infrastructures (RIs) for concentrated solar power/solar thermal energy applications, several European countries decided to apply to the European Commission to go a step forward and create a European Research Infrastructure Consortium (ERIC), a new legal form of association which poses a number of advantages in the endeavour for a further development of this technology in Europe at all levels. This new consortium, EU-SOLARIS ERIC, is likely to be legally implemented in October 2022, after a long negotiation and evaluation process, where the support of the respective Governmental research agencies of the countries involved has been crucial. EU-SOLARIS ERIC will be a legal entity and its main goal will be the improvement of the interoperability, accessibility and quality of services provided by the existing European research infrastructures to the CSP/STE research communities and industrial stakeholders. Although the current Members of the EU-SOLARIS consortium are Germany, France, Cyprus and Spain (Statutory Seat at Plataforma Solar de Almeria, Spain), plus Portugal as an Observer, it is open to any other country willing to participate as Member or Observer.
- 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.
- Experimental study of a double-diffusive system: application to solar pondsPublication . Tavares, Célia; Coelho, João M. P.; Alves, D. Castro; Abreu, Manuel A.; Joyce, A; Fernandes, E. C.A salt gradient solar pond is an artificial device used to collect and store solar thermal energy. A non-convective zone, in the middle of the solar pond, reduces thermal losses and allows a significant rise of temperature in the saltier lower zone where the solar thermal energy is stored. The non-convective zone, also named gradient zone, is characterized by a salinity gradient that increase the density with depth promoting the stability of this layer. The absorption of solar radiation in the pond creates a destabilizing temperature gradient in the non-convective zone that contradicts the density gradient. The different molecular diffusivities of heat and salt and the opposing effects on the vertical density distribution of the two gradients can lead to double-diffusive convection phenomena. In this context, a double-diffusive system has been studied experimentally in laboratory by heating a stratified salt layer from below. The instabilities caused by the destabilizing temperature gradients lead to the formation of convective zones separated from purely diffusive zone by thin interfaces. The main goals of this work are the study of the evolution of the double-diffusive layer and the analysis of the behaviour of the diffusive interface near conditions for which instabilities appear.