This work aims to characterize phase change materials (PCM) for thermal energy storage in buildings (thermal comfort). Fatty acids, biobased organic PCM, are attractive candidates for integration into active or passive storage systems for targeted application. Three pure fatty acids (capric, myristic and palmitic acids) and two eutectic mixtures (capric-myristic and capric-palmitic acids) are studied in this paper. Although the main storage properties of pure fatty acids have already been investigated and reported in the literature, the information available on the eutectic mixtures is very limited (only melting temperature and enthalpy). This paper presents a complete experimental characterization of these pure and mixed fatty acids, including measurements of their main thermophysical properties (melting temperature and enthalpy, specific heats and densities in solid and liquid states, thermal conductivity, thermal diffusivity as well as viscosity) and the properties of interest regarding the system integrating the PCM (energy density, volume expansion). The storage performances of the studied mixtures are also compared to those of most commonly used PCM (salt hydrates and paraffins).

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.

This work aims at assessing the applicability of a screening-oriented device dedicated to the establishment of increasingly complex phase diagrams of phase change materials. A thermography-based method has recently been proven to allow the detection of phase transitions of organic materials for multiple samples at a time. The phase transition detection capability of the infrared thermography method is here evaluated for metal systems based on well-referenced materials commonly employed in DSC calibration (pure sample of Gallium and a mixture of Gallium and Indium). The detected transitions are compared to literature data and DSC measurements. All transitions documented in the literature could be retrieved by thermography, and liquidus transitions are validated with DSC measurements. The encouraging nature of the results is discussed, and avenues for improving the method are considered.