• Energy Research
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The agro-industry of tomato generates three types of residues: ripe rotten tomato (unfit for consumption) (RT), green (unripe) tomato (GT), and tomato branches including leaves and stems (TB). These materials are commonly wasted or used as feed for livestock. Energy production through anaerobic digestion is an alternative way to manage and simultaneously valorise these materials. Initially, the operating conditions of mono anaerobic digestion were investigated using RT. Thus, a design of experiments based on a two-level fractional factorial design with resolution V was performed to determine the factors that affect biochemical methane potential (BMP). The substrate to inoculum ratio (SIR), total volatile solids concentration (VSt), working volume (WV), presence of nutrients (Nu), and the pre-incubation of the inoculum (Inc) were investigated. The results showed that SIR is the most important factor. The maximum BMP for RT was 297 NmLCH4/gVS with SIR = 0.5; tVS = 20 g/L; WV = 20%; no pre-incubation and the presence of nutrients. Using these optimum operating conditions, co-digestion was investigated through a mixture design approach. The substrates RT and GT presented similar BMP values, whereas TB led to a significantly lower BMP. Indeed, when high concentrations of TB were used, a significant decrease in methane production was observed. Nonetheless, the highest BMP was achieved with a mixture of 63% RT + 20% GT + 17% TB, with a production of 324 NmLCH4/gVS, corresponding to a synergetic co-digestion performance index of about 1.20. In general, although the substrate RT generates the highest BMP, the mixture with GT did not impair the methane yield. Overall, the co-digestion of tomato residues must be conducted with SIR close to 0.5 and the content of tomato branches in the reaction mixture should be kept low (up to 20%).

Relatório de Estágio do Mestrado em Gestão apresentado à Faculdade de Economia No âmbito do Mestrado em Gestão da Faculdade de Economia da Universidade de Coimbra, foi elaborado o presente documento que reflete o estágio curricular de 4 meses realizado na EDP-Gestão da Produção. A temática da RSE, escolhida como foco do presente relatório, surge por ter emergido como uma preocupação central a vários dos assuntos abordados durante o estágio e por se considerar um tema central para a empresa EDP, desde logo por fazer parte do Índice de Sustentabilidade Dow Jones. O objetivo do trabalho é o desenvolvimento das principais temáticas da RSE, apresentando-se a evolução conceptual, os principais modelos teóricos e a sistematização das teorias, assim como a abordagem Europeia e Nacional à RSE, a distinção dos conceitos de RSE, Sustentabilidade e Desenvolvimento Sustentável, as vantagens da implementação da RSE e os instrumentos e ferramentas que são utilizados pelas empresas – normas internacionais, relatórios de sustentabilidade, GRI Standards e índices de RSE. Por fim, analisa-se o impacto da RSE nas comunidades locais, recorrendo ao estudo do Relatório de Sustentabilidade da EDP. Pode-se inferir que as práticas de RSE têm um impacto bastante positivo nas comunidades locais, quer ao nível do seu bem-estar quer ao nível do desenvolvimento económico e que o desenvolvimento e investimento em práticas de Responsabilidade Social tem também um retorno positivo para a empresa. A EDP tem um elevado comprometimento com as comunidades locais ao desenvolver um conjunto de programas de investimento social, assumindo a sustentabilidade no seu ADN e contribuindo ativamente e de forma voluntária para os Objetivos de Desenvolvimento Sustentável (ODS). As part of the Master’s degree in Management at the Faculty of Economics of the University of Coimbra, this document was prepared to reflect the curricular internship of 4 months held at EDP-Production Management. The theme of Corporate Social Responsibility (CSR), chosen as the focus of this report, emerged as a central concern to several of the issues addressed during the internship and because it is considered a central theme for the EDP company, since it is part of the Dow Jones Sustainability Index. The aim of the work is the development of the main themes of CSR, presenting the conceptual evolution, the main theoretical models and the systematization of theories, as well as the European and National approach to CSR, the distinction of the concepts of CSR, Sustainability and Sustainable Development, the advantages of the implementation of CSR and the tools that are used by companies – international standards, sustainability reports, GRI Standards and CSR indexes. Finally, the impact of CSR on local communities is analyzed, using the study of EDP’s Sustainability Report. It can be inferred that CSR practices have a very positive impact on local communities, both in terms of their well-being and in terms of economic development and that the development and investment in Social Responsibility practices also have a positive return on the company. EDP has a high commitment to local communities by developing a set of social investment programs, assuming sustainability in its DNA and contributing actively and voluntarily to the Sustainable Development Goals.

Abstract The combined production of heat and power (CHP) has been considered the major alternative to traditional systems in terms of energy savings and environmental conservation. Micro-CHP systems are those suitable for a scale that ranges from the thermal demands of public/commercial buildings down to the needs of individual household. The residential market represents the most promising sector for the micro-CHP systems which has the potential to meet a number of energy, social and policy goals. Considering the available technologies, ORC based CHP solutions are recognized as one of the simplest and less likely to raise difficulties to retrofit the current residential heating systems. ORC based CHP systems points to a residential implementation almost with market available components. In fact, two of the most important components, the pump and the condenser, are considered off-the-shelf products while the expander has been adapted from a scroll compressor with success. On the other hand, for the ORC-evaporator there isn’t a ready-to-use component within this power range and the overwhelming majority of the ORC based systems developed by universities or research centers use an indirect way to vaporize the organic fluid which involves the implementation of an intermediate circuit, usually with water or oil, between the heat source and the ORC-evaporator. This intermediate circuit appears to be far from the ideal solution because it increases the thermal inertia, the system complexity and costs. This paper presents the conceptual design and the preliminary characterization results of a special developed heat-exchanger to be incorporated in an ORC cycle and work as an evaporator.

AbstractBuildings thermal performance is influenced by the urban context, such as adjacent buildings shadows, block wind paths, or solar radiation reflection. For this reason, in this paper, an automated procedure is used to generate and optimize buildings’ thermal performance in a closed O-shape urban quarter with ten building blocks to determine the importance of including the surroundings in estimating the buildings’ thermal behavior. The overall shape of the urban quarter is pre-designed, being mainly residential, with several stores in the ground floor and limited to three levels. Each building will have four alternative designs created using a hybrid evolutionary strategy technique that generates building's floor plans according to practitioner's preferences and requirements. Then, a sequential variable optimization procedure coupled with dynamic simulation engine is used to explore the improvement potential of each solution by changing and adding several building elements. The final quarter design is determined by combining the best of all buildings’ solutions from thermal performance criteria.The results demonstrate the influence of urban context in the resulting building's thermal performance. Despite the building's shape is similar in the four solutions, these have significant thermal behavior difference due to their interior organization and position in the urban quarter. A comparison analysis is carried out between all building block designs. The buildings, which have exterior walls with openings facing south, have almost half degree-hours of thermal discomfort due to the combination of large openings and shading overhangs. It is also possible to conclude that generative tools, enhanced with optimization procedures, may help practitioners in designing more energy efficient buildings.

In this paper, we compare Stirling and Ericsson cycles to determine which engine produces greater net work output for various situations. Both cycles are for external heat engines that utilize regenerators, where the difference is the nature of the regeneration process, which is constant volume for Stirling and constant pressure for Ericsson. This difference alters the performance characteristics of the two engines drastically, and our comparison reveals which one produces greater net work output based on the thermodynamic parameters. The net work output equations are derived and analysed for three different scenarios: (i) equal mass and temperature limits; (ii) equal mass and pressure or volume; and (iii) equal temperature and pressure or volume limits. The comparison is performed by calculating when both cycles produce equal net work output and then analysing which one produces greater net work output based on how the parameters are varied. In general, the results demonstrate that Stirling engines produce more net work output at higher pressures and lower volumes, and Ericsson engines produce more net work output at lower pressures and higher volumes. For certain scenarios, threshold values are calculated to illustrate precisely when one cycle produces more net work output than the other. This paper can be used to inform the design of the engines and to determine when a Stirling or Ericsson engine should be selected for a particular application.

Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia In photovoltaic solar systems in buildings, the mismatch between the energy generation and consumption leads to the need to inject energy into the grid, with a negative economic impact. To avoid it, the use of energy storage systems is increasingly important in order to store the surplus energy generation to be used in periods where the generation is lower than the consumption. Therefore, arises the need of intelligent control algorithms which, according to a predefined objective, ensure the correct management not only of the energy storage system, but also of the available solar resource.The main objective of this thesis was to analyse the impact of photovoltaic solar energy generation together with an energy storage system with lithium ion batteries in buildings of the services sector. For that, the building of the Department of Electrical and Computer Engineering of the University of Coimbra, which already has a photovoltaic solar system installed, was used as case study. The sizing of a possible expansion of the current photovoltaic system was done, as well as the sizing of a storage system with the aim to ensure reduction of costs with the purchased electricity. Thus, an intelligent control algorithm was implemented in MATLAB environment with the objective of managing and controlling the storage system to ensure the objectives of maximizing the self-consumption and minimizing costs with energy imported from the grid.Different scenarios were simulated and analysed, and through the analysis of the technical and economic availability it was possible to verify that the developed control strategies were successful, allowing to achieve good results regarding the reduction of the costs with the imported energy from the grid and the maximization of the self-consumption, as well as making the investment in the storage system cost-effective. Nos sistemas solares fotovoltaicos em edifícios o desajuste entre a produção de energia elétrica e o consumo leva à necessidade de injeção de energia na rede, com um impacto económico negativo. Para o evitar, é cada vez mais importante o uso de sistemas de armazenamento, com vista a armazenar a energia gerada em excesso de modo a esta ser utilizada em períodos onde a produção seja inferior ao consumo. Surge assim a necessidade de algoritmos de controlo inteligentes que, de acordo com um objetivo predefinido, assegurem a gestão correta não só do sistema de armazenamento, mas também do recurso solar disponível.O objetivo primordial desta dissertação foi analisar o impacto da geração de energia elétrica solar fotovoltaica em conjunto com um sistema de armazenamento de energia elétrica com baterias de iões de lítio em edifícios do setor dos serviços. Para tal, foi utilizado como objeto de estudo o edifício do Departamento de Engenharia Eletrotécnica e de Computadores da Universidade de Coimbra que conta já com um sistema solar fotovoltaico instalado. Foi realizado o dimensionamento de uma possível expansão do sistema atual, assim como o dimensionamento de um sistema de armazenamento que permita reduzir os custos com a compra de energia elétrica da rede. Assim, foi também implementado em ambiente MATLAB um algoritmo de controlo inteligente com o objetivo de fazer a gestão e controlo do sistema de armazenamento para assegurar os objetivos de maximização do autoconsumo e de minimização dos custos com a energia importada da rede.Foram simulados e analisados diferentes cenários e através da análise da viabilidade técnica e económica realizada foi possível constatar que as estratégias de controlo desenvolvidas foram bem-sucedidas, permitindo alcançar bons resultados relativos à redução dos custos com a importação de energia da rede e maximização do autoconsumo, assim como tornar rentável o investimento no sistema de armazenamento.

City centres are spaces where different economic and cultural values converge as a consequence of their current uses and functions. In the case of Porto (Portugal), more than 20 years after being declared a World Heritage Site by UNESCO (in 1996), tourism has had remarkable effects on its physical, social and economic features. Therefore, Porto—and in particular its city centre—is taken in this article as the object of study. The interest of this space lies in the fact that it has been rapidly transformed from a devalued old area into the centre of an important urban tourism destination on a European level. Based on the spatial and temporal analysis of a set of indicators related to tourism, housing and economic activity, we identify the main threats that this “culture-led regeneration”—much supported by tourism—could have on the cultural values of Porto. Our results show that this process is promoting an excessive use of space by tourism and an overexploitation of cultural values. We conclude with some policy recommendations to support strategies capable of keeping cultural values alive, which we consider sustainable compromises between heritage and modernization.

Biomass fly ash has been studied has a partial cement material, since this material has a positive effect on concrete properties. Even though, some mixes with BFA presents a positive benefit, they need to be economically competitive and present a good environmental performance. So, the analyse and comparison of concrete that uses BFA as raw material substitution in terms of environmental impacts related to the production of conventional concrete. One of the best approaches to develop this type of study is to use the life cycle assessment (LCA) method. This method quantifies both the input flows, such as energy, water and materials, as well as the output flows, such as CO2 emission, solid wastes and liquid wastes. Based both on the abovementioned context and methodological approach, a quantification and comparison of potential environmental impacts resulting from the production of 1 m3 of concrete was made, using different types of binder and quantities of cement substitution.