scholarly journals Si3N4 nanofelts/paraffin composites as novel thermal energy storage architecture

2020 ◽  
Vol 56 (2) ◽  
pp. 1537-1550
Author(s):  
Francesco Valentini ◽  
Andrea Dorigato ◽  
Alessandro Pegoretti ◽  
Michele Tomasi ◽  
Gian D. Sorarù ◽  
...  
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Composite Structures ◽  
Liquid Paraffin ◽  
Stored Energy ◽  
Storage Efficiency ◽  
Novel Material ◽  
Energy Storage Efficiency ◽  
Change Material

Abstract The environmental problems associated with global warming are urging the development of novel systems to manage and reduce the energy consumption. An attractive route to improve the energy efficiency of civil buildings is to store the thermal energy thanks, during heating, to the phase transition of a phase-change material (as paraffin) from the solid to the liquid state and vice versa. The stored energy can be then released under cooling. Herein, we developed a novel material (nanofelt) constituted by Si3N4 nanobelts able to absorb huge amounts of liquid paraffin in the molten state and to act as an efficient shape stabilizer. The nanofelt manufacturing technology is very simple and easy to be scaled-up. The effect of the Si3N4 nanofelts density and microstructure on the paraffin sorption and leakage and on the thermal properties of the resulting composite structures is investigated. It is shown that the produced Si3N4/paraffin composites are able to retain enormous fractions of paraffin (up to 70 wt%) after 44 day of desorption test on absorbent paper towel. The thermal energy storage efficiency measured through calorimetric tests is as high as 77.4% in heating and 80.1% in cooling.

Comprehensive Parametric Analysis and Sensitivity Study of Latent Heat Thermal Energy Storage System in Concentrated Solar Power Plants

2018 ◽  
Author(s):  
Hermes Chirino ◽  
Ben Xu
Keyword(s):  
Energy Storage ◽  
Latent Heat ◽  
Parameter Space ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Parametric Analysis ◽  
Sensitivity Study ◽  
Storage Efficiency ◽  
Concentrated Solar Power ◽  
Energy Storage Efficiency

Compared to Solar Photovoltaics (PV), Concentrated Solar Power (CSP) can store the excess solar thermal energy, extend the power generation at night and cloudy days, and levelize the mismatch between energy demand and supply. To make CSP competitive, Thermal Energy Storage (TES) system filled with phase change material (PCM) is a promising indirect energy storage technique, compared to the TES system using concrete or river rocks. It is of great interests to solar thermal community to apply the latent heat thermal energy storage (LHTES) system for large scale CSP application, because PCMs can store more thermal energy due to the latent heat during the melting/freezing process. Therefore, a comprehensive parametric analysis of LHTES system is necessary in order to improve its systematic performance, since LHTES system has a relatively low energy storage efficiency compared to TES systems using sensible materials. In this study, an 11-dimensionless-parameter space of LHTES system was developed, by considering only the technical constraints (materials properties and operation parameters), instead of economic constraints. Then the parametric analysis was performed based on a 1D enthalpy-based transient model, and the energy storage efficiency was used as the objective function to minimize the number of variables in the parameter space. It was found that Stanton number (St), PCM radius (r), and void fraction (ε) are the three most important ones. The sensitivity study was conducted then based on the three dimensionless-parameter space which will significantly influence the system performance. The results of this study make LHTES system competitive with TES system using sensible materials in terms of energy storage efficiency.

scholarly journals Optimization of Nano-Additive Characteristics to Improve the Efficiency of a Shell and Tube Thermal Energy Storage System Using a Hybrid Procedure: DOE, ANN, MCDM, MOO, and CFD Modeling

Mathematics ◽  
2021 ◽  
Vol 9 (24) ◽  
pp. 3235
Author(s):  
Mohammed Algarni ◽  
Mashhour A. Alazwari ◽  
Mohammad Reza Safaei
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Specific Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Hybrid Procedure ◽  
Stored Energy ◽  
Shell And Tube ◽  
Nano Additives ◽  
Change Material

Using nano-enhanced phase change material (NePCM) rather than pure PCM significantly affects the melting/solidification duration and the stored energy, which are two critical design parameters for latent heat thermal energy storage (LHTES) systems. The present article employs a hybrid procedure based on the design of experiments (DOE), computational fluid dynamics (CFD), artificial neural networks (ANNs), multi-objective optimization (MOO), and multi-criteria decision making (MCDM) to optimize the properties of nano-additives dispersed in a shell and tube LHTES system containing paraffin wax as a phase change material (PCM). Four important properties of nano-additives were considered as optimization variables: volume fraction and thermophysical properties, precisely, specific heat, density, and thermal conductivity. The primary objective was to simultaneously reduce the melting duration and increase the total stored energy. To this end, a five-step hybrid optimization process is presented in this paper. In the first step, the DOE technique is used to design the required simulations for the optimal search of the design space. The second step simulates the melting process through a CFD approach. The third step, which utilizes ANNs, presents polynomial models for objective functions in terms of optimization variables. MOO is used in the fourth step to generate a set of optimal Pareto points. Finally, in the fifth step, selected optimal points with various features are provided using various MCDM methods. The results indicate that nearly 97% of the Pareto points in the considered shell and tube LHTES system had a nano-additive thermal conductivity greater than 180 Wm−1K−1. Furthermore, the density of nano-additives was observed to be greater than 9950 kgm−3 for approximately 86% of the optimal solutions. Additionally, approximately 95% of optimal points had a nano-additive specific heat of greater than 795 Jkg−1K−1.

Numerical Characterization of Anisotropic Heat Sink Composites

2010 ◽  
Vol 654-656 ◽  
pp. 1500-1503 ◽  
Author(s):  
Thomas Fiedler ◽  
Graeme E. Murch ◽  
Timo Bernthaler ◽  
Irina V. Belova
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Heat Sink ◽  
Composite Structures ◽  
Phase Change Materials ◽  
Void Space ◽  
Change Material

This work addresses the numerical analysis of anisotropic composite structures for thermal energy storage and temperature stabilization. The basic idea of heat sink composites is the combination of metallic matrices for fast energy transfer with phase change materials for thermal energy storage. Anisotropic matrices, such as lotus-type structures, allow for increased control of the thermal energy flow, without the necessity of additional thermal insulation. As an example, thermal energy can be directed towards a surface cooled by convection and excess energy is stored in the phase-change material. Computed tomography data of copper lotus-type material is used for the generation of the numerical calculation models. Due to its particular meso-structure, this material is characterised by strongly anisotropic properties. The void space of this cellular metal is filled with the phase-change material paraffin in order to enhance the energy storage capacity. A recently extended Lattice Monte Carlo method is used to evaluate the anisotropic thermal properties of these promising materials.

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