Abstract
Thermal energy storage offers enormous potential for a wide range of energy technologies. Phase-change materials offer state-of-the-art thermal storage due to high latent heat. However, spontaneous heat loss from thermally charged phase-change materials to cooler surroundings occurs due to the absence of a significant energy barrier for the liquid–solid transition. This prevents control over the thermal storage, and developing effective methods to address this problem has remained an elusive goal. Herein, we report a combination of photo-switching dopants and organic phase-change materials as a way to introduce an activation energy barrier for phase-change materials solidification and to conserve thermal energy in the materials, allowing them to be triggered optically to release their stored latent heat. This approach enables the retention of thermal energy (about 200 J g−1) in the materials for at least 10 h at temperatures lower than the original crystallization point, unlocking opportunities for portable thermal energy storage systems.
Highlights
Thermal energy storage offers enormous potential for a wide range of energy technologies
Phase-change materials (PCMs), such as salt hydrates[1], metal alloys[2], or organics[3], store thermal energy in the form of latent heat, above their phase-transition temperature, which is released via reverse-phase transformation[4]
We prepared a composite of tridecanoic acid, as an example of n-fatty acids with high heat of fusion (177 J g−1), and an azobenzene dopant that is functionalized with a tridecanoic ester group to render high miscibility with the PCM molecules
Summary
Thermal energy storage offers enormous potential for a wide range of energy technologies. We report a combination of photo-switching dopants and organic phase-change materials as a way to introduce an activation energy barrier for phase-change materials solidification and to conserve thermal energy in the materials, allowing them to be triggered optically to release their stored latent heat. We introduce azobenzene dopants into conventional organic PCMs as a way to change the intermolecular dynamics These dopants, possessing activation energy barriers for switching between photoisomers, provide stability to the phase storing thermal energy and triggerabilty for energy release, allowing controllable, high-density energy storage in scalable organic composites. The azobenzene dopants that change conformation upon illumination can be locked in the liquid phase of PCMs by lowering their crystallization temperature (Tc), retaining the thermal energy storage at cooler temperatures
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