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Browsing Ciências e Tecnologia / Sciences and Technology by Sustainable Development Goals (SDG) "07:Energias Renováveis e Acessíveis"
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- Adipates as new phase change material: seeking for a low temperature energy storage systemPublication . Sequeira, Maria Carolina; Nogueira, Bernardo A.; Caetano, Fernando J. P.; Diogo, Herminio; Fareleira, João M. N. A.; Fausto, RuiThe recent and endless increasing need for energy is requiring imperative and efficient solutions. Renewable energies are an effective solution, but they are also intermittent, which often leads to a gap between the availability of energy and its demand. Therefore, energy storage becomes crucial for improving the efficiency by reducing the mismatch between demand and supply thus offering better management capabilities. The use of phase change materials (PCMs) became an attractive technology, especially for active cooling systems. In particular, eutectic systems can be designed for each application, allowing significant energy savings, which is very relevant in what concerns economic and environmental sustainability [1]. Equilibrium studies and their phase diagrams are crucial to characterize the behavior of these systems, particularly for new PCMs [2]. This work aims the characterization of a selected type of binary system composed by di-n-alkyl adipates that can be used for energy storage at low temperatures, starting by the construction of solid-liquid phase diagram based on Differential Scanning Calorimetry (DSC) and Raman Spectroscopy results. The studied system is a binary mixture of diethyl and dibutyl adipates and reveals to behave as a eutectic system at low temperatures, possessing also polymorphism, therefore presenting a relatively complex phase diagram. The eutectic point was found around -33ºC and the polymorphism transition, being characteristic of the dibutyl adipate, occurs at around -36ºC for the overall phase diagram. Raman spectroscopy was fundamental concerning the construction of the phase diagram, enabling to identify the different solid and liquid phases of the system. This work provides new phase equilibrium data, which, to the knowledge of the authors, are the first in the literature, concerning these compounds. The studied binary system has promising characteristics for low temperature energy storage. It is also demonstrated how solid-liquid-phase equilibrium studies are the key to select the most appropriate phase change material for a specific thermal energy storage (TES) application.
- Challenges ahead for sustainable cities: an urban form and transport system reviewPublication . Medina Monteiro, João Pedro; Sousa, Nuno; Coutinho-Rodrigues, João; Natividade-Jesus, EduardoThis article reviews the critical issues surrounding the development of sustainable urban environments, focusing on the impact of transport and urban form on energy consumption and greenhouse gas emissions. The aim is to provide an overview of the state-of-the-art on the subject and to unravel what directions the literature suggests for sustainable urban planning. Current research and practices are synthesized, highlighting the interdependence of urban design and transportation systems in achieving sustainability goals. Important dimensions and practices of city planning and transport policies are explored, including urban form, urban sprawl, mixed land use, densification and infill, and urban public spaces, and how these directly influence transport dynamics, including modal choices and energy consumption. Innovative approaches in urban planning, such as transit-oriented development, and technological advancements, such as electric mobility, are also examined and their potential roles in sustainable urban transport. The conclusion underscores the urgency of adopting holistic and adaptable strategies to foster sustainable urban environments, calling for concerted efforts from policymakers, urban planners, and communities. Awareness of the conclusions can help municipal decision-makers in planning their cities for a sustainable future. Finally, the authors analyze important directions for future research and practical applications towards developing cities that are environmentally sound, socially equitable, and economically viable.
- Correction: Di-Alkyl Adipates as new phase change material for low temperature energy storagePublication . Nogueira, Bernardo A.; Diogo, Hermínio P.; Fausto, Rui; Caetano, Fernando J. P.; Fareleira, João; Sequeira, Maria CarolinaThe following is a correction to the supplementary information of the paper titled “Di-Alkyl Adipates as new phase change material for low temperature energy storage” by Maria C.M. Sequeira, Bernardo A. Nogueira, Fernando J.P. Caetano, Hermínio P. Diogo, João M.N.A. Fareleira, Rui Fausto that appeared in International Journal of Thermophysics 44:165 (2023). https://doi.org/10.1007/s10765-023-03274-3
- Di-Alkyl adipates as new phase change material for low temperature energy storagePublication . Sequeira, Maria Carolina; Nogueira, Bernardo A.; Caetano, Fernando J. P.; Diogo, Herminio; Fareleira, João M. N. A.; Fausto, RuiThis work is a contribution to the thermal characterization of a selected binary system of two di-n-alkyl adipates that can be used as phase change material for thermal energy storage at low temperatures. The construction of the solid–liquid phase diagram using differential scanning calorimetry (DSC), complemented with Raman Spectroscopy studies for the system composed by diethyl and dibutyl adipates is presented. The solidus and liquidus equilibrium temperatures were determined by DSC for the pure components and 30 binary mixtures at selected molar compositions were used to construct the corresponding solid–liquid phase diagram. The binary system of diethyl and dibutyl adipates presents eutectic behaviour at low temperatures. The eutectic temperature was found at 240.46 K, and the eutectic composition was determined to occur at the molar fraction xdibutyl = 0.46. Additionally, the system shows a polymorphic transition, characteristic of dibutyl adipate, occurring at ca. 238 K, confirmed by optical microscopy. To the best of our knowledge, no reference to the phase diagram of the present system could be found in the literature. Raman spectroscopy was essential to complement the construction of the phase equilibrium diagram, enabling the identification of the solid and liquid phases of the system. Finally, the liquidus curve of the phase diagram was also successfully predicted using a suitable fitting equation, being the root mean square deviation of the data from the correlation equal to 0.54 K. In addition, this fitting operation enabled a correct prediction of the eutectic composition of the system.
- Energia nuclear em Portugal: não, obrigado?Publication . Pires, Maria Eliana Santos; Sousa, NunoAs alterações climáticas, marcadamente visíveis, principais responsáveis pela degradação do nosso planeta, são um facto inegável. Largamente impulsionadas pelo boom energético, assente na queima desenfreada de combustíveis fósseis, desde meados do século passado e que se perspetiva cada vez mais acelerado. A premência da mudança de paradigma reúne consenso mundial. Portugal ao apostar nas energias renováveis trilha caminho tentando alcançar a neutralidade carbónica. Pese embora o esforço, as intermitências climatéricas, assoladas de elevada imprevisibilidade, comprometem, claramente este objetivo. Sendo, por isso, desejável e necessário adotar um mix energético que colmate as crescentes necessidades energéticas, onde a energia nuclear, preterida em Portugal, poderá assumir papel fundamental, contribuindo, na atualidade, com uma décima parte da energia elétrica produzida a nível mundial. Neste trabalho, após breve enquadramento teórico da energia nuclear, aplicou-se uma metodologia que visa perceber a atitude face ao nuclear de uma amostra populacional específica, nomeadamente os estudantes da Licenciatura em Ciências do Ambiente (LCA) da Universidade Aberta. Para tal, aplicou-se um questionário global, exceto no reporte à unidade curricular Novas Energias da LCA, onde o assunto foi debatido com alguma profundidade, lecionada aos participantes. No entanto, o reduzido âmbito populacional traduziu-se numa pequena quantidade de dados coletados, repercutindo-se numa dificuldade na identificação de tendências com validade estatística. A análise foi efetuada com o recurso, maioritariamente, às técnicas de regressão. Foi possível identificar, apenas, oito tendências com significado estatístico. Contudo, fica preparado um questionário que possa ser traduzido, futuramente, para toda a população portuguesa.
- Entre Nós : energia nuclearPublication . Universidade Aberta; Mexia, José; Almeida, VítorPara nos falar da Energia Nuclear, convidámos José Carvalho Soares, professor catedrático do Departamento de Física da Faculdade de Ciências da Universidade de Lisboa.
- Introdução à programação: procedimentosPublication . Coelho, JoséIntroduz-se o conceito de procedimento em programação, o que é e porque é importante. Mostra-se como criar e utilizar um procedimento na linguagem C. Introduz-se a passagem de variáveis por referência para um procedimento, e declaração de variáveis globais e variáveis estáticas. Termina-se com alguns erros de qualidade de código.
- Introdução à programação: vetoresPublication . Coelho, JoséIntroduz-se o conceito de vetor em programação, o que é e porque é necessário. Mostra-se como criar e utilizar um vetor na linguagem C. Introduz-se o conceito de string, formas de inicializar vetores, e matrizes na linguagem C. Termina-se com alguns erros de qualidade de código.
- Low temperature energy storage PCM systems: phase equilibrium studiesPublication . Sequeira, Maria Carolina; Nogueira, Bernardo A.; Caetano, Fernando J. P.; Diogo, Herminio; Fareleira, João M. N. A.; Fausto, Rui
- Low temperature thermal energy storage: insights into odd-even n-alkane systemPublication . Sequeira, Maria Carolina; Nogueira, Bernardo; Nikitin, Timur; Caetano, Fernando J. P.; Diogo, Herminio; Fausto, Rui; Fareleira, João M. N. A.