A thermodynamic journey: unlocking cold thermal energy storage with phase equilibrium studies

Sequeira, Maria Carolina; Nikitin, Timur; Caetano, Fernando J. P.; Diogo, Herminio; Fareleira, João; Fausto, Rui

http://hdl.handle.net/10400.2/20804

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Authors

Sequeira, Maria Carolina

Nikitin, Timur

Caetano, Fernando J. P.

Diogo, Herminio

Fareleira, João

Fausto, Rui

Abstract(s)

As 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.

Keywords

sustainable energy thermal energy storage (TES) phase change materials (PCM) n-alkane systems

URI

http://hdl.handle.net/10400.2/20804

Citation

M. C. M. Sequeira, T. Nikitin, F.J.P. Caetano, H.P. Diogo, J.M.N.A. Fareleira, R. Fausto, A Thermodynamic Journey: Unlocking Cold Thermal Energy Storage with Phase Equilibrium Studies, [Oral Communication] CQE Days 2025, Lisboa, 12-13 maio de 2025. (OC7). https://sites.google.com/view/cqedays2025/home