Ambiente e Sustentabilidade | Comunicações em congressos, conferências e seminários / Communications in congresses, conferences and seminars
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Percorrer Ambiente e Sustentabilidade | Comunicações em congressos, conferências e seminários / Communications in congresses, conferences and seminars por Domínios Científicos e Tecnológicos (FOS) "Engenharia e Tecnologia::Engenharia Química"
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- Enhancing low-temperature thermal energy storage with next-generation PCMsPublication . Sequeira, Maria Carolina; Nogueira, Bernardo; Nikitin, Timur; Diogo, Herminio; Caetano, Fernando J. P.; Fareleira, João; Fausto, RuiThe communication reports the potential use of PCM, n-alkanes and n-alkyl adipates, at low temperatures (between -80 ºC and -20 ºC) for different applications in the cold chain logistics such as the transport of medicines. For the phase equilibrium studies, of the different mixtures, techniques as differential Scanning Calorimetry (DSC), Hot-stage Polarized Microscopy and Raman Spectroscopy were used.
- A thermodynamic journey: unlocking cold thermal energy storage with phase equilibrium studiesPublication . Sequeira, Maria Carolina; Nikitin, Timur; Caetano, Fernando J. P.; Diogo, Herminio; Fareleira, João; Fausto, RuiAs the urgent demand for sustainable energy solutions increase, thermal energy storage (TES) systems have become crucial in improving energy efficiency and ensuring supply-demand balance1. In low-temperature sectors such as refrigeration, cold-chain logistics, and medical applications, phase change materials (PCM) are particularly valuable due to their high latent heat capacity and reversible phase transitions1,2. However, finding PCM that are not only efficient and reliable, but also environmentally safe, remains a challenge. Over the last few years, our research has focused on phase equilibrium studies of potential organic PCM, providing valuable experimental data and thermodynamic insights for designing low-temperature TES systems. This work began with the study of binary systems of di-n-alkyl adipates, specifically diethyl/dibutyl adipates, which revealed eutectic behaviour with a eutectic point at -33 ºC. Expanding on this, we investigated n-alkane systems, including n-octane/n-decane and n-decane/n-dodecane, both of which exhibited eutectic transitions at sub-zero temperatures. Recently, efforts focused on n-alkanes, namely n-nonane/n-decane and n-nonane/n-undecane, paying special attention to odd–even carbon chain effects on the phase diagrams. These studies uncovered new low-temperature PCM potential candidates and clarified phase change behaviours for this kind of systems. The latest work on adipates, particularly dimethyl and dipropyl, revealed a eutectic behaviour near -20 ºC, showing great suitability as low-temperature PCM. Those studies significantly expand the database of viable PCM, enhancing our understanding of low-temperature phase behaviour. This work brings together four years of contributions to the rapidly advancing field of sustainable low-temperature TES, offering both practical and theoretical insights.
- A thermodynamic journey: unlocking cold thermal energy storage with phase equilibrium studiesPublication . Sequeira, Maria Carolina; Nikitin, Timur; Caetano, Fernando J. P.; Diogo, Herminio; Fareleira, João; Fausto, RuiAs the urgent demand for sustainable energy solutions increase, thermal energy storage (TES) systems have become crucial in improving energy efficiency and ensuring supply-demand balance. For low-temperature areas such as refrigeration, cold-chain logistics, and specific medical applications, phase change materials (PCM) are particularly valuable due to their high latent heat capacity and reversible phase transitions. However, finding PCM that are not only efficient and reliable, but also environmentally safe, remains a challenge. In this work we present the work done with several adipates and alkanes towards their use as PCM for low-temperature thermal energy storage.
- Tuning thermal performance: the role of molecular asymmetry in di-n-alkyl adipates for efficient low-temperature thermal energy storagePublication . Sequeira, Maria Carolina; Nikitin, Timur; Caetano, Fernando J. P.; Diogo, Herminio; Fareleira, João; Fausto, RuiThe development of efficient and sustainable thermal energy storage (TES) systems is crucial for improving energy efficiency in various applications, especially at low temperatures, such as cryogenic cooling, cold storage, logistics and transportation. Phase change materials (PCM) play a key role in TES, as they allow the storage and release of significant amounts of latent heat during phase transitions. In this context, our research group has been working on new materials, particularly binary systems, with potential application as PCM for efficient low-temperature TES1. As a result, di-n-alkyl adipates have recently emerged as promising candidates due to their favorable thermal properties, chemical stability, and phase change behavior2. Our previous work2 focused on the binary system of diethyl and dibutyl adipates, highlighted the potential of adipates as low-temperature PCM, motivating further research into their solid-liquid phase change behavior and structure-property relationships. Building upon this initial study, we have expanded our research into a broader range of di-n-alkyl adipates. One of the key aspects of our current research is the identification of eutectic compositions within adipate-based binary systems. Eutectic mixtures are particularly attractive as PCM enabling tunable phase transition temperatures to match specific TES requirements. Through the careful combination of results obtained from Differential Scanning Calorimetry (DSC), Hot-Stage Microscopy (HSM), and Raman Spectroscopy, a detailed phase diagram was methodically crafted to highlight the intricate eutectic behavior of these systems, identifying compositions that optimize thermal performance. In this study, the interplay between alkyl chain length and thermal behavior, particularly the influence of odd–even effects in binary systems is also approached. By selecting mixtures that combine odd-odd, even-odd or even-even substituent arrangements, we have explored how molecular asymmetry impacts solid-liquid phase change behavior. Our results reveal distinct trends, demonstrating how subtle structural variations can be leveraged to fine-tune the thermophysical properties of these materials. Our findings contribute to the growing field of organic PCM, demonstrating that di-n-alkyl adipates are viable candidates for low-temperature TES applications. By elucidating their phase change behavior, we provide a foundation for the innovative development of next-generation thermal storage materials, paving the way for more advanced and efficient solutions.