Repositório RCAAP

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Road traffic is one of the transportation sectors with faster growth and also one of the most important emitters of greenhouse gases (GHGs). In this work, an analysis of the environmental benefits resulting from the introduction of hydrogen on road transport in Portugal is made. Impact is analyzed mainly looking at the pollutant emissions provided by road transport at the point of use. Emissions associated to road transport have been estimated using the software COPERT (version 4), since it provides a detailed methodology for each specific pollutant related to the vehicle fleet of a region or country, as well as the driving conditions and fuel consumption. Passenger cars, light duty vehicles and public transport buses are the vehicles categories in which the hydrogen technology is foreseen. The hydrogen penetration rates (moderate and high) are extracted from the European Project HYWAYS. Two trends are then considered, which give penetration rates of 40.0 % and 74.5 % in 2050 for the moderate and high scenarios respectively.

The direct methanol fuel cell (DMFC) with proton exchange membrane (PEM) as electrolyte and liquid methanol/water as the energy carrier is a promising power source for micro and various portable electronic devices (mobile phones, PDA’s, laptops and multimedia equipment). However a number of issues need to be resolved before DMFC can be commercially viable such as the methanol crossover and water crossover which must be minimised in portable DMFC’s. In the present work, a detailed experimental study on the performance of an «in-house» developed DMFC with 25cm2 of active membrane area, working near ambient conditions (ambient temperature and pressure) is described. Tailored MEAS (membrane electrode assemblies), with different structures and combinations of gas diffusion layers (GDL), were designed and tested in order to select optimal working conditions at relatively high methanol concentration levels without sacrificing performance. The experimental polarization curves were successfully compared with the predictions of a steady state, one-dimensional model accounting for coupled heat and mass transfer, along with the electrochemical reactions occurring in the DMFC recently developed by the same authors. The influence of the anode gas diffusion layer media, the membrane thickness and the MEA properties on the cell performance is explained under the light of the predicted methanol crossover rate across the membrane

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Groundwater fluxes can be highly variable in both space and time, which is a factor of uncertainty in groundwater flow modelling. This project aims to implement appropriate techniques to assess spatio-temporally groundwater recharge and thus improve the reliability and forecasting capabilities of groundwater flow models. The methodology is composed of the following steps:(i) design of field specific data acquisition schema to capture the spatial variability; (ii) intensive hydrological data monitoring to obtain the temporal variability of fluxes; (iii) development of a spatio-temporal recharge assessment protocol for its dynamic integration with numerical groundwater flow model. The recharge model is developed as a lumped parameter approach and requires a set of soil and aquifer parameters that can be obtained by standard field work and laboratory measurements. The developed procedures are tested on the Pisoes catchment of the semi-arid zone of Alentejo province (Portugal). As the lateral heterogeneity of the clayey topsoil was considered crucial for the reliability of the recharge model, field data acquisition focused on:(i) apparent electrical conductivity measurements, using the GeonicsTM ground conductivity meter EM-31, to derive topsoil thickness and extrapolate it through kriging with external drift using high resolution multispectral images as auxiliary maps; (ii) drilling and augering, which allowed soil profiling observations and depth-sampling to determine vadose zone hydraulic properties in laboratory. Monitoring at strategic locations of the catchment provided the driving forces (rainfall and potential evapotranspiration) and the state variables (soil moisture and hydraulic heads) of the system. Data integration determined the depth-wise discretization of the vadose zone and its parameterization. The developed recharge model (pyEARTH-2D) solves the water balance in the topsoil layer through linear relations between fluxes and soil moisture. pyEARTH-2D is coupled with flow model MODFLOW and its calibration is done against transient groundwater hydraulic heads. First results showed improvements of the groundwater flow model solution in the Pisoes catchment. Further work in this research direction will focus on developing the dynamic link involving simultaneous calibration of pyEARTH-2D and groundwater flow model MODFLOW through the PEST parameter estimation algorithm.

In this work, H2 production by a strain of Enterobacter aerogenes using as substrate pure glycerol and glycerol-containing biodiesel wastes was compared. The effect of physico-chemical parameters such as temperature, initial substrate and biomass concentrations on the bio-hydrogen production efficiency was investigated. The influence of the simultaneous removal of gases produced was also evaluated The results obtained showed that a decrease of the process temperature of 37 to 30 ºC leads to both, an increase of the bio-hydrogen production rate and a decrease of the equilibrium time of the process. Furthermore, it was also observed that using 10 g/dm3 of pure glycerol or biodiesel wastes containing the same concentration of glycerol as substrate lead to very similar bio-hydrogen production yields (2.5dm3 H2/dm3 fermentation medium). This proves that the performance of the strain of E. aerogenes used was not influenced by the presence of other components than glycerol in biodiesel residues, at least for the biodiesel wastes concentration studied. Simultaneous removal of gaseous phase (mainly H2 and CO2), with its production, shows to be very efficient leading to an increase of the value of the H2/CO2 volumetric ratio, in the headspace, from 2 to 8, which is very promising regarding costs involved in the technologies for purification of H2 produced.

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The introduction of the “Energy Performance Building Directive” (EPBD) [1] and consequently the new National Building Regulation [2] in the Member States (MS) lead to a totally new legal situation concerning, requirements and procedures on the building sector. Under the scope of an EU project called Keep Cool, a survey was undertaken in order to review the energy efficiency criteria, in the national building codes, concerning summer comfort or mechanical cooling system in order to elaborate recommendations towards a sustainable summer comfort. This paper presents the results of this survey [3] carried out under the participate countries (7 countries), and the main goals were the following to update the information regarding the new national building regulations to have a first insight regarding the requirements and summer calculations adopted in each country and to identify the positive and the negative aspects of the different regulations and selection of the best practice examples, in order to draw up recommendations for introducing sustainable summer comfort measures into future national building codes. A comparative analysis has started with some very precise answers and had permitted to carry out a comparative analysis between some national building codes. A review was undertaken concerning envelope constructive solutions (opaque and transparent), thermal mass, ventilation rates and the corresponding values limits.

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Nesta tese, abordamos a aula do ensino médio e sua relação com a cultura juvenil, com o intuito de descrever, analisar e interpretar o significado da aula como espaço de produção do conhecimento e formação cultural dos jovens. Partimos do pressuposto de que a cultura juvenil não é considerada elemento fundante na maioria das escolas públicas do ensino médio no estado de Pernambuco. Nesse sentido, realizamos uma pesquisa qualitativa de cunho etnográfico, na qual recorremos a entrevistas semiestruturadas, questionário, observação, caderno de campo, análise documental e fotografias cujos dados coletados revelaram que a cultura é defendida como modos de vida e os fenômenos estudados representam um corpus de significados. Nessa teia de relações, fomos tecendo o caminho da inovação pedagógica vinculado ao conceito mais geral de cultura. Ao final da pesquisa, chegamos à conclusão de que a cultura pode ser a porta de acesso para a inovação das práticas pedagógicas nas escolas, onde alunos e professores assumem parcerias para a formação cidadã.

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