Arnold Rafael Martínez Guarín

To determine whether phase change materials (PCMs) available on the market have potential for thermal energy storage (TES) systems, it is essential to understand their thermophysical properties. However, conventional characterization methods can be costly because they require specialized equipment and rigorous experimental protocols. This research contributes to the generation of technical and scientific knowledge in the field of PCMs through the economical characterization methods available in the literature. PCMs available in the Colombian market were characterized using the T-History and T-Melting (CHF) methods to determine the melting point (Tm), enthalpy of fusion (Hm), thermal conductivity (K), and solid (Cps) and liquid (Cpl) heat capacities. The experiments were validated by comparison using the international paraffins RUBITHERM® RT45 and RT55 as references. Additionally, the analysis of Hm, Cps, and Cpl was performed using Differential Scanning Calorimetry (DSC) to evaluate the standard deviations between the two proposed methods and the results obtained from DSC and the values established in the technical datasheet of the international paraffins. The results of the T-History method showed error percentages of Hm: 1.14%, Tmi: 3.79%, and Cpl: 16.62%. However, the estimation of Cps was challenging because of the difficulty in accurately assessing the area differences when the reference, environment, and sample had very close temperatures. For the CHF method, Tmi: 13.45%, Tmf: 1.00%, Cps: 19.54%, Hm: 2.44%, and K: 9.34%. In this case, the calculation of Cpl was difficult because of the heat losses in the testing module. The thermal properties of Colombian PCMs were successfully determined, achieving significant progress in the national state-of-the-art industry. Moreover, these PCMs have potential for thermal energy storage, showing characteristics comparable to those of other commercially available PCMs for this purpose.

Introducción: la generación de energía por medio de fuentes renovables ha ganado importancia en los campos de investigación debido a los efectos adversos que generan los combustibles fósiles sobre el ambiente, en este contexto, generación de energía por medio de biomasa presenta grandes ventajas debido a su alto potencial y bajo costo. Objetivo: El objetivo fue evaluar la operación de un equipo de refrigeración por absorción de calor usando energía solar fotovoltaica y biogás como fuentes de energías renovables. Metodología: Se realizó una caracterización energética de las fuentes implementadas considerando medidas de radiación solar en la ciudad de Montería y El poder Calorífico del biogás. Así mismo, se realizaron pruebas en el equipo disponiendo en su interior 1 litro de agua. Finalmente se calculó el coeficiente de operación. Resultados: los resultados obtenidos muestran que la operación del equipo es de 8 horas aproximadamente, La composición química del biogás entregó 58% de metano y 42% de dióxido de carbono, alcanzando un poder calorífico de 23.05 MJ/kg. Por ultimo los coeficientes de operación obtenidos fueron de 0.58; 0.08; 0.27 y 0.07 para energía eléctrica, GLP, energía solar y biogás respectivamente. Conclusiones: Existe un potencial energético importante en cuanto a la implementación de la Energía solar y biogás para este tipo de procesos de generación de frío, cumpliendo así con el objetivo principal del proyecto, Comprobando así que si es posible implementar las energías renovables en el sistema de refrigeración por absorción.

The growing interest in developing applications for the storage of thermal energy (TES) is highly linked to the knowledge of the properties of the materials that will be used for that purpose. Likewise, the validity of representing processes through numerical simulations will depend on the accuracy of the thermal properties of the materials. The most relevant properties in the characterization of phase change materials (PCM) are the phase change enthalpy, thermal conductivity, heat capacity and density. Differential scanning calorimetry (DSC) is the most widely used technique for determining thermophysical properties. However, several unconventional methods have been proposed in the literature, mainly due to overcome the limitations of DSC, namely, the small sample required which is unsuitable for studying inhomogeneous materials. This paper presents the characterization of two commercial paraffins commonly used in TES applications, using methods such as T-history and T-melting, which were selected due to their simplicity, high reproducibility, and low cost of implementation. In order to evaluate the reliability of the methods, values calculated with the proposed alternative methods are compared with the results obtained by DSC measurements and with the manufacturer’s technical datasheet. Results obtained show that these non-conventional techniques can be used for the accurate estimation of selected thermal properties. A detailed discussion of the advantage and disadvantage of each method is given.