Abstract
Nanoencapsulated phase change materials (nePCMs) are one of the technologies currently under research for energy storage purposes. These nePCMs are composed of a phase change core surrounded by a shell which confines the core material when this one is in liquid phase. One of the problems experimentally encountered when applying thermal cycles to the nePCMs is that their shell fails mechanically and the thermal stresses arising may be one of the causes of this failure. In order to evaluate the impact of the uncertainties of material and geometrical parameters available for nePCMs, the present work presents a probabilistic numerical tool, which combines Monte Carlo techniques and a finite element thermomechanical model with phase change, to study two key magnitudes of nePCMs for energy storage applications of tin and aluminium nePCMs: the maximum Rankine's equivalent stress and the energy density capability. Then, both uncertainty and sensitivity analyses are performed to determine the physical parameters that have the most significant influence on the maximum Rankine's stress, which are found to be the melting temperature and the thermal expansion of the core. Finally, both a deterministic and a probabilistic failure criterion are considered to analyse its influence on the number of predicted failures, specially when dispersion on tensile strength measurements exists as well. Only 1.87% of tin nePCMs are expected to fail mechanically while aluminium ones are not likely to resist.
Highlights
The world demand of energy is estimated to increase by 26% and CO2 associated emissions will continue rising by 10% by the year 2040 with respect to those registered in 2017 (International Energy Agen, 2019)
With regard to the equivalent stress distribution and in agreement with (Forner-Escrig et al, 2020), Rankine’s criterion is used to predict the mechanical failure of the Nanoencapsulated phase change materials (nePCMs), which usually occurs at the shell
Experimental uncertainties are taken into ac count to obtain the mechanical probability of failure and this mechan ical failure is one of the problems experimentally encountered when the nePCMs undergo thermal processes
Summary
The world demand of energy is estimated to increase by 26% and CO2 associated emissions will continue rising by 10% by the year 2040 with respect to those registered in 2017 (International Energy Agen, 2019). In order to reduce the environmental problems, efforts are made by several scientific communities to foster the use of renewable energies, which exploit natural resources –unlimited on a human timescale– without generating polluting emissions. The present work focuses exclusively on solar energy and more precisely, on its application to concentrated solar plants (CSP), since solar energy is the renewable energy presenting the major potential for exploitation of energy (In ternational Energy Agen, 2011). One of the characteristics that makes CSP stand out among other renewable energy technologies is the possibility of incorporating Thermal Energy Storage (TES) systems to mitigate the previously mentioned generation gaps. TES systems appear to be a field of research on its own nowadays for energetic transition towards renewable energies within the context of green policies (Gil et al, 2010; Xu et al, 2015; Akhmetov et al, 2016; Mondragon et al, 2017)
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