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The National Renewable Energy Laboratory (NREL), under an ARRA CSP Award, is extending previous work on nanoscale phase change materials to develop materials with technologically relevant temperature ranges and encapsulation structures.


This project seeks to increase thermal storage densities by at least a factor of three over the current state-of-the-art in order to achieve the SunShot goals. NREL is investigating quantum confinement effects on thermal conductivity in nanowires and core-shell structures for thermoelectric applications. It has been demonstrated that it is energetically favorable for C60 and metals to enter the interior of tubes. Reduction in melting point with decreasing particle size has been observed with tin, copper, and other metals in the nanoscale range. Unusual phase behavior and crystal structures have also been observed in carbon and metal oxide nanotubes filled with metals. Interesting phase transition behavior has also been observed in metal/metal oxide core-shell nanoparticles.


The effect of moving to nanoparticle or nanoscale structures on latent heat (phase change) thermal storage is not known. However, there are a number of studies that suggest that nanoscale confinement may lead to dramatic changes in the accessibility of latent heat. Furthermore, nanostructures also have the potential to overcome the heat transfer limitations that are encountered in conventional solid/solid or solid/liquid phase change systems in which the reduced thermal conductivity of the solid layer at the heat transfer interface reduces efficiency.

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