Browsing by Author "Monteiro, Joaquim"
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- Aplicação da definição nZEB da REHVA a uma renovação de um edifício de habitação Português.Publication . Monteiro, Joaquim; Castro, OlgaOs edifícios desempenham um papel-chave nas sociedades que estão a tentar atenuar os efeitos das alterações climáticas. Mais de 50% dos edifícios residenciais existentes na UE-25 foram construídos antes de 1970. Assim, estes edifícios são de significativa importância na redução de consumo de energia e emissões de CO2. Os edifícios de balanço de energia (quase) zero (nZEB) são uma solução possível para este problema. Este estudo tem por objetivo analisar a aplicação da metodologia nZEB no retrofitting de uma habitação típica Portuguesa de 1950. Foi demonstrado que a energia primária utilizada pode ser reduzida a um valor muito baixo (11,95 kWh/m2.ano) em comparação com o consumo de referência (69,15 kWh/m2.ano), através da aplicação das melhores técnicas atuais de construção, juntamente com a utilização de energia produzida localmente através de fontes renováveis. O uso de fontes de energia renovável permitiu que este edifício alcançasse um valor de RERp de 89%.
- Application of the nZEB methodology in the retrofitting of a typical Portuguese dwelling from the 60's.Publication . Monteiro, Joaquim; Castro, OlgaBuildings and the whole built environment are in a key role when societies are mitigating climate change and adapting to its consequences. More than 50% of the existing residential buildings in EU-25 were built before 1970. Thus, these buildings are of significant importance in reducing energy consumption and CO2 emissions. The existence of more nearly zero energy buildings (nZEB) is a possible solution for this problem. This study aims to analyze the application of the nZEB methodology in the retrofitting of a typical Portuguese dwelling build in 1950. It was shown that the primary energy used can be reduced to a very low value (11,95 kWhep/m2.y) in comparison with the reference consumption (69,15 kWhep/m2.y), with the application of the best construction techniques together with the use of energy from on-site renewable sources.
- Assessment of an Innovative Way to Store Hydrogen in VehiclesPublication . Baptista, Andresa; Pinho, Carlos; Pinto, Gustavo Filipe; Ribeiro, Leonardo; Monteiro, Joaquim; Santos, TiagoThe use of hydrogen as an alternative to fossil fuels for vehicle propulsion is already a reality. However, due to its physical characteristics, storage is still a challenge. There is an innovative way, presented in this study, to store hydrogen in conventional vehicles propelled by spark-ignition reciprocating engines and fuel cells, using hydrogen as fuel; the storage of hydrogen will be at high pressure within small spheres randomly packed in a tank, like the conventional tank of fuel used nowadays in current vehicles. Therefore, the main purpose of the present study is to assess the performance of this storage system and compare it to others already applied by car manufacturers in their cars. In order to evaluate the performance of this storage system, some parameters were taken into account: The energy stored by volume and stored by weight, hydrogen leakage, and compliance with current standards. This system is safer than conventional storage systems since hydrogen is stored inside small spheres containing small amounts of hydrogen. Besides, its gravimetric energy density (GED) is threefold and the volumetric energy density (VED) is about half when compared with homologous values for conventional systems, and both exceed the targets set by the U.S. Department of Energy. Regarding the leakage of hydrogen, it complies with the European Standards, provided a suitable choice of materials and dimensions is made.
- Assessment of the Use of Solar Desalination Distillers to Produce Fresh Water in Arid AreasPublication . Monteiro, Joaquim; Baptista, Andresa; Pinto, Gustavo Filipe; Ribeiro, Leonardo; Mariano, HélderWater is an important resource for human beings, yet there are inhabited places tormented by the scarcity of it. The present study is concerned with places where, seemingly, the best way to get water is through solar distillers. These places should have, typically, high values of solar irradiation and a lack of human and economic resources to build and operate complex equipment. A set of sites scattered around the world was chosen, and then the presumed productivity and thermal efficiency that solar distillers would have if they were installed at these places was calculated. The mathematical model used with this purpose assumes steady-state operation; the values of mass of water distilled and distiller efficiency were calculated for every hour, but the results presented are annual averages. Then, an economic study was made based on local costs of construction materials for the distillers, the workforce, and the prices of water to predict the payback time of solar distillers. Finally, a study on environmental impact, particularly in terms of greenhouse gas (GHG) emissions, was made to compare reverse osmosis (RO) with solar distillation. For the sites studied, typical values of annual water output are in the range of 414 dm3/m2, for Évora, up to 696 dm3/m2, for Faya Largeau; the minimum efficiency was found for Évora, as 11.5%, and the maximum efficiency was found for Tessalit, as 15.2%. Payback times are very high, regardless of the areas of the globe where solar distillers are implanted. Regarding GHG emissions, solar distillation is preferable to RO.
- Biodiesel Production Systems: Operation, Process Control and TroubleshootingPublication . Caetano, Nídia; Ribeiro, Vera; Ribeiro, Leonardo; Baptista, Andresa; Monteiro, JoaquimBiodiesel is a renewable fuel, produced from waste cooking oils, animal fats, vegetable and algae oils. Its use is intended to replace diesel in conventional diesel engines, causing lower polluting emissions. To produce biodiesel, certain details must be carefully considered, namely feedstock composition, reaction parameters, process conditions, process equipment, purification processes, analysis of biodiesel properties, troubleshooting and storage. In what concerns feedstock composition, parameters such as acidity, insolubles, moisture, phospholipids, sulphur, polymerized triglycerides, impurities, etc., must be determined to decide about the pretreatment steps (washing, degumming, filtration, bleaching, deodorization, among others) to be implemented, and the need for esterification prior to transesterification. In what concerns the selection of process equipment some questions arise, namely the materials, heating methods and thermal insulation to use, alternatives to enhance the reaction, need for neutralization and process control system. The purification process includes biodiesel purification, methanol recovery and glycerine valorisation. The excess methanol must be recovered from biodiesel and glycerine by distillation and reused in the process while glycerine can be further purified and sold for application from the chemical to the pharmaceutical industry. The quality of biodiesel must be certified by the analyses performed according to the standards (e.g. EN 14214, ASTM D6751). Troubleshooting is needed in biodiesel production during start-up and under steady production of a facility; problems may arise regarding quality and appearance of biodiesel, reaction conditions, methanol removal, stirring in reactors, glycerine and biodiesel separation, as well as excess of water and other feedstock impurities. Biodiesel can be stored for up to 6 months; its storage poses challenges concerning degradation by contact with air and light, which cause oxidation. Some additives could extend the lifespan of biodiesel by increasing oxidation stability; other technique is the fractionation to remove the undesired fatty acid methyl ester (FAME).
- Comparison of contaminant removal effectiveness and air change efficiency as indicator of air diffusion quality.Publication . Monteiro, Joaquim; Castro, OlgaThe ventilation efficiency concept is an attempt to quantify a parameter that can easily distinguish the different options for air diffusion in the building spaces. Thirteen strategies of air diffusion were measured in a test chamber through the application of the tracer gas method, with the objective to validate the calculation by Computational fluid dynamics (CFD). Were compared the Air Change Efficiency (ACE) and the Contaminant Removal Effectiveness (CRE), the two indicators most internationally accepted. The main results from this work shows that the values of the numerical simulations are in good agreement with experimental measurements and also, that the solutions to be adopted for maximizing the ventilation efficiency should be the schemes that operate with low speeds of supply air and small differences between supply air temperature and the room temperature.
- Experimental study on the impact of using a fan coil in the evaluation of contaminant removal effectiveness of common air diffusion strategiesPublication . Monteiro, Joaquim; Bathelt, Amadeusz; Castro, OlgaThe aim of this study is to investigate the differences in ventilation efficiency owing to an air supply position and air exhaust locations of an air distribution system in combination with a fan coil. Ten strategies of air diffusion strategies were performed in a test chamber applying the tracer gas techniques. All experiments were performed with a presence of the fan coil. For all the ten strategies 9 rph provided by a fan coil was investigated. Three strategies were studied with other renovations rates (6, 7 and 8 rph). For 3 strategies influence of different position of CO2 probes on the final results was checked. The main conclusions of this work are as follows: if the renovation rate is over 7 rph, the contaminants and temperature vertical distributions are destroyed due to mixing of the air; if fan coil provides renovations over 7 rph, the efficiency for every strategy approaches 1; placement of temperature and contaminant probes has an influence on the result of the experiment for particular strategies.
- Impact of design options in zero energy building conception: the case of large buildings in PortugalPublication . Lima, Pedro; Monteiro, Joaquim; Castro, OlgaThe new recast of Directive 2010/31/EU in order to implement the new concept NZEB in new buildings, is to be fully respected by all Member States, and is revealed as important measure to promote the reduction of energy consumption of buildings and encouraging the use of renewable energy. In this study, it was tested the applicability of the nearly zero energy building concept to a big size office building and its impact after a 50-years life cycle span.
- Impact of using solar heat pumps for domestic hot water in Portuguese residential buildingsPublication . Monteiro, Joaquim; Castro, OlgaIn recent years, we have seen an improvement of existing facilities in dwellings in Portugal. Within the heat pumps systems, there is a special type known as direct expansion heat pump assisted by Solar Collector (DX-SAHP). It was calculate the SPF indicator for 30 regions of Portugal. It was analyses the potential of reductions of CO2 and primary energy use for the retrofitting of DHW preparation systems. It was found that the performances of this type of equipment are benefiting from the Portuguese climate conditions, especially in the South and in the Autonomous Regions. Best SPF was obtained for Beja. It was found in all regions of the high potential for reducing CO2 emissions and verifying a potential significant reduction of primary energy consumption.
- Influência do clima e do caudal de ar variável em função da demanda para um sistema centralizado tudo-ar.Publication . Almeida, Marco; Monteiro, Joaquim; Castro, OlgaNa perspetiva da melhoria da eficiência energética e da QAI dos edifícios de serviços existentes e que são climatizados com sistemas centralizados do tipo tudo-ar, foi desenvolvida uma aplicação informática que permite simular o comportamento dinâmico de situações reais de funcionamento relativas ao tratamento de ar. Com vista à redução do consumo energético associado à utilização dos sistemas técnicos de climatização, foi desenvolvido um modelo matemático para os diversos processos físicos que ocorrem numa unidade de tratamento de ar, implementado numa aplicação informática e validado o seu funcionamento através de experiências laboratoriais desenvolvidas numa sala de testes de climatização. O presente estudo permitiu determinar a influência das variáveis, clima e caudal de ar insuflado variável em função da demanda, no consumo energético associado às condições de conforto do ambiente interior para a estação de aquecimento. Foi estimado um aumento de 65% de consumo energético para o clima mais rigoroso de Bragança, acompanhado de um menor potencial de redução de consumo energético (6% em termos médios), relativamente aos outros climas. Relativamente à utilização de estratégias de ventilação controlada pela demanda (DCV), estimaram-se que os potenciais de redução de consumo energético máximos poderão atingir valores de 40% e 39% para Faro e Porto, respetivamente, e de 30% para Bragança. A ferramenta informática desenvolvida poderá ser uma ajuda em análises económicas a efetuar, nomeadamente para renovações de edifícios de serviços existentes.