Phase Diagrams of Fatty Acids as Biosourced Phase Change Materials for Thermal Energy Storage

Abstract

Featured Application: A potential application of this work consists of accelerating the screening step required for the study and selection of promising binary systems of phase change materials for thermal energy storage at medium temperature. Abstract: Thermal energy storage is known as a key element to optimize the use of renewable energies and to improve building performances. Phase change materials (PCMs) derived from wastes or by-products of plant or animal oil origins are low-cost biosourced PCMs and are composed of more than 75% of fatty acids. They present paraffin-like storage properties and melting temperatures ranging from −23 • C to 78 • C. Therefore, they could be appropriate for latent heat storage technologies for building applications. Although already studied, a more detailed exploration of this class of PCMs is still required. In this frame, a screening of fatty acids and of their related binary systems must be performed. The infrared thermography method (IRT), already used for the fast estimation of simple phase diagrams (~2 h), appears to be best suited to achieve this goal. IRT method applicability to the more complex fatty acids phase diagrams is hence studied in this work. A phase diagram comprising more than a hundred data sets was obtained for the palmitic acid-stearic acid binary system. The reliability of the results is assessed by comparison to differential scanning calorimetry (DSC) measurements or results from other standard methods presented in literature and to a solid-liquid equilibrium thermodynamic model.

Fixed Grid Numerical Models for Solidification and Melting of Phase Change Materials (PCMs)

“…However, due to the small thickness, the liquid layer was hardly studied, given the difficulties to observe directly or even to measure such a region. In the growing scenario of PCM literature [5][6][7][138][139][140], further investigation efforts have to be made to clarify the physical phenomena that occur in the liquid layer, as well as to enforce and validate the existing theoretical equations.…”

Applicability of Infrared Thermography for the Detection of Phase Transitions in Metal Alloys

“…The IRT method has first been described by Palomo et al [8] and further developed in several instances [9][10][11]. Figure 1 shows a scheme of its experimental setup.…”

“…An innovative infrared thermography (IRT) method has recently been employed for the rapid screening of organic phase change materials in order to find suitable candidates for a latent heat thermal energy storage application [8][9][10][11]. It enabled the estimation of phase diagrams of fatty acid binary systems in a single short experiment.…”

“…The IRT method has been extensively used and validated for the study of phase transitions of organic materials including systems of sugar alcohols [16], fatty acids [9,10], and fatty alcohols [11]. Given the promising results obtained, it is interesting to investigate its applicability to inorganic materials which could allow the rapid screening of blended PCMs, the development of a large material library, the study of the phase transitions of multicomponent PCMs and the establishment of their phase diagrams.…”

A fast and low-cost dynamic calorimetric method for phase diagram estimation of binary systems

“…The approached phase diagram provided by this method allows rapidly identifying compositions or areas of interest to be precisely investigated with the use of the aforementioned standard methods. The concept and applicability of this method has already been successfully demonstrated for the phase diagram estimation of binary systems of sugar alcohols [5] and fatty acids [6]. Given the promising results provided by the infrared thermography (IRT) method, an extensive assessment of the inluence of experimental parameters is performed in order to identify the coniguration as cheap, accurate and fast as possible.…”