Browsing by Subject "Ionanofluids"

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    Open Access
    Innovative application of graphene nanoplatelet-based ionanofluids as heat transfer fluid in hybrid photovoltaic-thermal solar collectors
    (Nature, 2025) Moulefera, I.; Delgado Marín, J. J.; Cascales, A.; Montalbán, M. G.; Alarcón, M.; Víllora Cano, Gloria; Ingeniería Química; Facultad de Química
    The ongoing pursuit of efficient solar thermal energy systems has driven significant interest in the development of advanced nanofluids, particularly those utilizing carbon-based nanostructures such as graphene nanoplatelets (GNP) and carbon nanotubes (CNTs). These materials, when dispersed in base fluids like water or ionic liquids, have gained attention for their tunable thermophysical properties, including thermal conductivity, viscosity, and specific heat capacity. This has positioned them as promising candidates for enhancing the thermal performance of solar collectors. However, literature examining direct experimental comparisons between the thermophysical behavior of GNP-based and CNT-based nanofluids, particularly in both water and ionic liquid media, remains sparse. Similarly, studies evaluating how such nanofluids affect the overall efficiency of solar collectors are limited and fragmented. This study investigates, for the first time, the application of GNP-based ionanofluids (INFs) in commercial hybrid photovoltaic-thermal (PVT) solar collectors. INFs were prepared using GNP and 1-ethyl-3-methylimidazolium acetate ([Emim] Ac) ionic liquid. Their thermophysical properties, including density, viscosity, thermal conductivity, and specific heat capacity, were comprehensively characterized. Long-term stability was also assessed to ensure consistent performance over time. Comparative tests with water and pure ionic liquid as base fluids revealed that INFs exhibited a significantly higher temperature rise within the collector, attributed to their lower specific heat capacity. This resulted in an exergy efficiency improvement of over 5% compared to the ionic liquid alone, underscoring the potential of INFs as advanced heat transfer fluids for high-temperature solar systems. These findings highlight the novelty of using GNP-based INFs in solar applications and pave the way for future research in optimizing nanofluid compositions for renewable energy systems.
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    Publication
    Open Access
    Study of Ionanofluids Behavior in PVT Solar Collectors: Determination of Thermal Fields and Characteristic Length by Means of HEATT® Platform
    (MDPI, 2024-11) Alarcón García, Mariano; Luna Abad, Juan Pedro; Seco Nicolás, Manuel; Moulefera, I.; Víllora Cano, Gloria; Ingeniería Química
    Solar electric and solar thermal energies are often considered as part of the solution to the current energy emergency. The pipes of flat plate solar devices are normally heated by their upper surfaces giving rise to an asymmetric temperature field in the bulk of the fluid, which influences the heat transfer process. In the present work, a study of the characteristic length of tubes, or most efficient distance at which heat transfer occurs, in flat photovoltaic-thermal (PVT) hybrid solar devices has been carried out using three heat transfer fluids: water, [Emim]Ac ionic liquid and ionanofluid of graphene nanoparticles suspended in the former ionic liquid. The mean objective of the study was to know whether the heat transfer occurs in optimal conditions. Experimental measurements have been made on a commercial PVT device, and numerical simulations have been performed using the HEATT® platform to determine the characteristic length of the process. The tests conducted showed a clear improvement in the temperature jump of the fluid inside the collector when INF is used compared to water and ionic liquid and even a higher overall energy efficiency. Electricity generation is not greatly affected by the fluid used, although it is slightly higher when water is used. Slower fluid velocities are recommended if high fluid outlet temperatures are the goal of the application, but this penalizes the overall thermal energy production. The characteristic process length is not typically achieved in parallel tube PVT collectors with ordinary flow rates, which would require a speed, and consequently, a flow rate, about 10 times lower, which penalizes the performance (up to four times), although it increases the fluid outlet temperature by 234%, which can be very interesting in certain applications. Ionanofluids may in the medium term become an alternative to water in flat plates or vacuum solar collectors for applications with temperatures close to or above 100 °C, when their costs will hopefully fall. The results and methodology developed in this work are applicable to solar thermal collectors other than PVT collectors.