• Energy Research

Thermal performance of SS-PCM composites, simulating building envelope conditions, is difficult to asset with traditional laboratory equipment. However, in this work, the evaluation of three SS-PCM based on eutectic fatty acid mixtures of capric-myristic (CA/MA), lauric-myristic (LA/MA) and palmitic-stearic (PA/SA) was accomplished by a testing setup that allows to test samples in steady-state and dynamic conditions. Moreover, a SS-PCM-based acrylic plaster was evaluated as a fiber cement siding finish. The obtained values were used to calculate the thermal transmittance (U-value), heat storage capacity, and thermal inertia parameters under a simulated diurnal cycle. Results showed that the use of phase change materials in powder form increase thermal lag between 148% and 180% and present a decrement factor <0.2. Furthermore, building envelopes as fiber cement siding with a SS-PCM-based acrylic plaster coating decreased 20.8% the indoor temperature, increase 67.26% the thermal lag and decrease 9% of the decrement factor. The authors are pleased to acknowledge the financial assistance of the “Ministerio de Ciencia, Tecnología e Innovación-MINCIENCIAS” through the PhD grant 758-2016-Contract 036–2016, Universidad de Antioquia and Sumicol S.A.S. The work is partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31—MCIU/AEI/FEDER, UE) and by the Ministerio de Ciencia, Innovación y Universidades—Agencia Estatal de Investigación (AEI) (RED2018-102431-T). This work is partially supported by ICREA under the ICREA Academia programme. Dr. Cabeza would like to thank the Catalan Government for the quality accreditation given to her research group GREiA (2017 SGR 1537). GREiA is a certified agent TECNIO in the category of technology developers from the Government of Catalonia.

Abstract Ceramic insulators used in power transmission lines were coated with titanium dioxide films with the aim of reducing atmospheric soiling accumulation over its surface. Properties as adhesion, thickness, roughness and phase composition of films were evaluated. Contac angle was also measured. Dry-flashover and leakage current electrical tests were carried out in coated and un-coated insulators to evaluate the influence of titanium dioxide film in electrical properties. The in-service behavior of coated and un-coated insulators installed in power transmission towers were evaluated in two sites with different soiling source. Surface characterization of insulators before and after field exposition was performed by Micro-Raman Spectroscopy. The coatings exhibited self-cleaning properties and electrical properties of insulators were not affected. After 5 months of exposure in the energized power line, a decrease in the surface soiling was observed in Balsillas (organic soiling). Nevertheless, in Calera (inorganic soiling) self-cleaning effect was not observed.

Abstract Several characterization techniques were used to identify and quantify the mineralogical phases of a Colombian mineral that could be used as a suitable porous support for shape-stabilized phase change materials (SS-PCMs). The mineral was calcined in a laboratory box furnace at 600 °C, 900 °C and 1100 °C. The phase evolution and microstructure were investigated by X-ray fluorescence (XRF), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Through the Rietveld refinement method the phases were quantified. The results showed that the mineral was composed of 19.75% kaolinite, 11.88% quartz, 10.75% illite, and 40.00% diatomite. Preliminary SS-PCMs were produced through vacuum assisted impregnation. Lauric-myristic acid binary eutectic was prepared and then incorporated at 25 wt.% (SS-LAMA25), 35 wt.% (SS-LAMA35), and 40 wt.% (SS-LAMA40) into the raw mineral. The leakage obtained for the composites was between 0.1% and 4.9%. Differential scanning calorimetry (DSC) showed a latent heat of fusion of 29.63 kJ/kg, 51.57 kJ/kg and 56.59 kJ/kg, and phase change temperatures of 35.39 °C, 36.35 °C and 36.17 °C, for the SS-LAMA25, SS-LAMA35 and SS-LAMA40, respectively.

Abstract In the development of renewable energies, thermal energy storage (TES) has become a key opportunity to relieve to some extent the increase in energy demand and supply. The past two decades have seen increasingly advances in the field of phase change materials (PCM) as latent heat storage systems, being one concern their containment when using solid to liquid PCM. The purpose of this paper is to review the state-of-the-art of shape-stabilization (SS-PCM) and encapsulation (CS-PCM) of organic PCMs for low thermal applications (