Metallic Composites Phase-Change Materials for High-Temperature Thermal Energy Storage

2013 ◽  
Author(s):  
Xiaobo Li ◽  
Hengzhi Wang ◽  
Hui Wang ◽  
Sohae Kim ◽  
Keivan Esfarjani ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Phase Change Materials ◽  
Metallic Alloys ◽  
Heat Of Fusion ◽  
Latent Heat Of Fusion ◽  
High Latent Heat

Inorganic materials and organic salts are usually used as phase change materials (PCMs) for thermal energy storage. Some of these materials have high latent heat of fusion; however one major drawback of these materials is the low thermal conductivity, which limits the rate of charging and discharging process. In this paper, we studied metallic alloys (eutectic alloys or alloys with a narrow melting temperature range) as phase-change materials, which have both high thermal conductivity and high latent heat of fusion. A formula was presented from entropy change to predict the latent heat of fusion of metallic alloys. We found that the latent heat of fusion of alloys can be expressed from three different contributions: the latent heat from each element, the sensible heat, and the mixing entropy. From the theory we also showed that latent heat of fusion could be greatly increased by maximizing the entropy of mixing, which can be realized by introduce more elements in the alloys, i.e., form ternary alloys by adding elements to binary alloys. This idea is demonstrated by the synthesis and measurement of the binary alloy 87.8Al-12.2Si (at%) and ternary alloy 45Al-40Si-15Fe (at%). The metallic alloy is synthesized by hot pressing method. The latent heat of fusion of 45Al-40Si-15Fe (at%) is about 865 kJ/kg with melting temperature from 830 °C to 890 °C from the differential scanning calorimetry (DSC) measurement, comparing with 554.9 kJ/kg and 578.3 °C for the binary alloy 87.8Al-12.2Si (at%). From the binary to the ternary alloy, the contribution to the latent heat from mixing entropy increases by 17%.

Latent Heat Storage: Container Geometry, Enhancement Techniques, and Applications—A Review

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
S. Arunachalam
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Heat Exchangers ◽  
Phase Change Materials ◽  
Heat Storage ◽  
Low Thermal Conductivity

Energy storage helps in waste management, environmental protection, saving of fossil fuels, cost effectiveness, and sustainable growth. Phase change material (PCM) is a substance which undergoes simultaneous melting and solidification at certain temperature and pressure and can thereby absorb and release thermal energy. Phase change materials are also called thermal batteries which have the ability to store large amount of heat at fixed temperature. Effective integration of the latent heat thermal energy storage system with solar thermal collectors depends on heat storage materials and heat exchangers. The practical limitation of the latent heat thermal energy system for successful implementation in various applications is mainly from its low thermal conductivity. Low thermal conductivity leads to low heat transfer coefficient, and thereby, the phase change process is prolonged which signifies the requirement of heat transfer enhancement techniques. Typically, for salt hydrates and organic PCMs, the thermal conductivity range varies between 0.4–0.7 W/m K and 0.15–0.3 W/m K which increases the thermal resistance within phase change materials during operation, seriously affecting efficiency and thermal response. This paper reviews the different geometry of commercial heat exchangers that can be used to address the problem of low thermal conductivity, like use of fins, additives with high thermal conductivity materials like metal strips, microencapsulated PCM, composite PCM, porous metals, porous metal foam matrix, carbon nanofibers and nanotubes, etc. Finally, different solar thermal applications and potential PCMs for low-temperature thermal energy storage were also discussed.

Latent Heat of Fusion and Melting Temperature of Molten Salt Based Carbon Nanotube Suspensions Used as Phase Change Materials

2015 ◽  
Author(s):  
Pau Gimenez-Gavarrell ◽  
Vincent D. Romanin ◽  
Sonia Fereres
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Melting Temperature ◽  
Latent Heat ◽  
Base Fluid ◽  
Phase Change Materials ◽  
Heat Of Fusion ◽  
Latent Heat Of Fusion ◽  
Base Materials ◽  
Nanoparticle Suspensions

Thermal Energy Storage (TES) can improve the efficient and economical use of available resources associated with renewable energies. The choice of Phase Change Materials (PCM) for TES applications is particularly attractive, since PCMs provide high energy storage densities, low costs, and allow energy storage at constant temperatures during the melting/solidification process. However, most commonly used PCMs have low thermal conductivity values, typically less than 1 W/mK. This leads to insufficient heat exchange rates in many applications, where power is as important as the amount of energy stored. Previous studies have shown that adding nanoparticles to molten salts can enhance the thermal conductivity and heat capacity, thus improving performance in TES systems. This study analyzes how adding nanoparticles to ionic liquids/solids affects the latent heat of fusion and melting temperature, critical characteristics of many thermal management systems. An important aspect of nanoparticle suspension preparation is the synthesis method, both from the point of view of scalability and effect on thermophysical properties. Several nanoparticle suspensions are synthesized with carbon nanotubes (CNT) and salt or ionic liquid base materials, using different synthesis methods and sonication times. The melting point and latent heat of fusion are measured for the base materials and nanoparticle suspensions using a Differential Scanning Calorimeter (DSC). The change in latent heat and melting temperature of the nanofluid with respect to the base fluid is shown to be present but not substantial. Possible explanations for the modification of thermal properties with respect to the base fluid are discussed.

Enhanced thermal conductivity of phase change materials with ultrathin-graphite foams for thermal energy storage

2014 ◽  
Vol 7 (3) ◽  
pp. 1185-1192 ◽  
Author(s):  
Hengxing Ji ◽  
Daniel P. Sellan ◽  
Michael T. Pettes ◽  
Xianghua Kong ◽  
Junyi Ji ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Phase Change ◽  
Specific Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Heat Of Fusion ◽  
Change Material ◽  
Enhanced Thermal Conductivity

Embedding continuous ultrathin-graphite foams (UGFs) with volume fractions as low as 0.8–1.2 vol% in a phase change material (PCM) can increase the effective thermal conductivity by up to 18 times, with negligible change in the melting temperature or mass specific heat of fusion.

scholarly journals Development of Binary Eutectic Organic Phase Change Materials for Solar Thermal Energy Storage Systems

2019 ◽  
Vol 9 (2) ◽  
pp. 2207-2210
Keyword(s):  
Energy Storage ◽  
Melting Point ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Solar Thermal ◽  
Heat Of Fusion ◽  
Solar Thermal Energy ◽  
Latent Heat Of Fusion ◽  
High Latent Heat

Solar thermal energy storage unit anchored fatty acids as Phase Change Materials (PCMs) having narrow range of transition temperature and high latent heat of fusion. In this paper, a new novel eutectic PCM was developed by using a fatty acid (acetamide) and non-paraffin organic PCM (acetanilide) for a sharp melting point and high latent heat of fusion. The optimized eutectic PCM may be used for middle temperature range solar thermal energy storage systems. The binary mixture of acetamide and acetanilide at various compositions by mass ratio (wt%) was prepared and optimized experimentally for lowest value of melting point at a eutectic mixture composition of 60 wt% of acetamide and 40 wt% of acetanilide. Eutectic PCM was analyzed by Differential Scanning Calorimetry (DSC) and Field-Emission Scanning Electron Microscopy (FE-SEM). DSC results revealed that optimized eutectic PCM has a sharp melting point of 65.37°C and high latent heat of fusion of 224.67 kJ/kg. Accelerated thermal cycle testing of optimized eutectic PCM was performed for 100 melting and freezing cycles and change in melting temperature and latent heat of fusion was acceptable.

Preperation and Characterization Study of Phase Change Materials for Thermal Energy Storage Applications

2015 ◽  
Vol 787 ◽  
pp. 77-81
Author(s):  
Pasam Bhagyalakshmi ◽  
K. Rajan ◽  
K. Senthil Kumar
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Eutectic Mixture ◽  
High Energy ◽  
Heat Of Fusion ◽  
Differential Scanning Calorimetric

Thermal Energy Storage using phase change materials (PCM) has become an interesting area of energy research because of its high energy storage density, isothermal nature of storage process and small volume changes. In the present work paraffin wax (PW) and Palmitic acids(PA) are chosen as phase change materials and mixed in different proportions(40-60% PW-PA, 50-50% PW-PA and 60-40% PW-PA) to prepare eutectic PCMs. And also paraffin is combined with Copper oxide nano powder to prepare composite PCM. Differential Scanning Calorimetric (DSC) Tests have been conducted to find the latent heat capacity of the above combination of PCMs. The results showed that 40-60%PW-PA eutectic mixture is effective in increasing the latent heat of fusion compared to the other combinations.

scholarly journals Nano-Enhanced Phase Change Materials in Latent Heat Thermal Energy Storage Systems: A Review

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3821
Author(s):  
Kassianne Tofani ◽  
Saeed Tiari
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Storage Systems ◽  
Heat Pipes ◽  
Energy Storage Systems ◽  
Thermal Energy Storage Systems

Latent heat thermal energy storage systems (LHTES) are useful for solar energy storage and many other applications, but there is an issue with phase change materials (PCMs) having low thermal conductivity. This can be enhanced with fins, metal foam, heat pipes, multiple PCMs, and nanoparticles (NPs). This paper reviews nano-enhanced PCM (NePCM) alone and with additional enhancements. Low, middle, and high temperature PCM are classified, and the achievements and limitations of works are assessed. The review is categorized based upon enhancements: solely NPs, NPs and fins, NPs and heat pipes, NPs with highly conductive porous materials, NPs and multiple PCMs, and nano-encapsulated PCMs. Both experimental and numerical methods are considered, focusing on how well NPs enhanced the system. Generally, NPs have been proven to enhance PCM, with some types more effective than others. Middle and high temperatures are lacking compared to low temperature, as well as combined enhancement studies. Al2O3, copper, and carbon are some of the most studied NP materials, and paraffin PCM is the most common by far. Some studies found NPs to be insignificant in comparison to other enhancements, but many others found them to be beneficial. This article also suggests future work for NePCM and LHTES systems.

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