Research paperAluminum and silicon based phase change materials for high capacity thermal energy storage
Introduction
Replacement of fossil fuels by renewable energy sources especially solar energy is a clear solution for the future of energy. With the decreased cost of photovoltaic (PV) and concentrated solar power (CSP) for electricity generation, the challenge of energy storage becomes more important due to the unavailability of sunlight at night time. Energy storage not only reduces the mismatch between the supply and the demand, but also improves the performance and reliability of energy systems, hence plays a crucial role in the future energy needs [1], [2]. For PV, batteries can be used for energy storage, however it is very expensive. In recent years, great attention has been drawn to CSP [3], in which the storage of thermal energy is much cheaper than electrical energy storage.
For thermal energy storage, either sensible heat or latent heat of the storage materials is of great interest. Sensible heat normally requires a large volume of heat storage material due to its relatively low thermal capacity plus another drawback that the heat exchange is not at a constant temperature. Phase change materials (PCMs) usually provide a large amount of heat due to phase change between different states during charging and discharging at a constant phase changing temperature [4], [5], [6], [7], [8], [9], [10], [11]. Among all the heat storage materials, up to now, salts are often used for this purpose due to the low cost and abundance in nature. However, the rather low thermal conductivity of salt can drastically decrease the efficiency of heat storage and extraction [9], [11]. Therefore, much effort has been devoted to improve the thermal conductivity of salt PCMs by utilizing a fin tube configuration, adding metal materials, etc. [12], [13], [14], [15], which, however, lead to significant weight and cost increasing. Besides, corrosion is also an important issue when inorganic salts are used as PCMs, particularly under the condition of high working temperatures.
Compared with other PCMs used in latent heat thermal energy storage method, metallic PCMs display high potential in high energy density TES systems because of their good thermal, physical and chemical properties [16]. Several studies have been reported on the thermophysical properties of different metals and alloys as PCMs [17], [18], [19], [20], [21]. It was reported that the large latent heat on a mass or volume basis were obtained in binary and ternary alloys with abundant elements Al, Cu, Mg, Si, and Zn [22], but not all of the metallic materials are suitable as PCMs for use in TES systems because of some drawbacks of physical and chemical properties such as high vapor pressure, short-term chemical stability, and fire hazard.
Considering the good performance of Al and Si based compositions: suitable phase change temperatures, high solid–liquid latent heat densities, and good thermal reliabilities, eutectic Al–Si alloy was mostly investigated as PCM in medium temperature TES systems over the past few decades [16], [23]. However, the syntheses and properties of none eutectic Al and Si compositions were seldom reported. For applications requiring temperature higher than 580 °C such as concentrated solar systems [24], eutectic Al–Si alloy is not suitable. Hence, it is very urgent to develop new Al and Si based PCMs with higher temperature suitable for solar TES systems by changing the ratio of Al/Si or adding new elements.
In this paper, six kinds of Al and Si based materials, which can be used in three different working temperature ranges due to their melting points, were prepared by arc-melting as medium to high temperature PCMs. The important physical properties of the materials including the melting temperature, the latent heat of the solid–liquid phase transition, and the temperature-dependent thermal conductivity of the compositions were investigated in details.
Section snippets
Preparation of materials
Six compositions of 87.8Al-12.2Si, 80Al–20Si, 70Al–30Si, 60Al–40Si, 45Al–40Si–15Fe, and 17Al–53Si–30Ni were prepared by arc-melting. Al (shot, 99.999%, Alfa Aesar), Si (bulk, 99.9999%, Alfa Aesar), Fe (particle, 99.98%, Alfa Aesar), and Ni (chunk, 99.95%, Alfa Aesar) were weighed according to the designed ratio. In order to ensure a homogeneous composition, each sample was melted for five times by arc-melting. The whole arc-melting process was conducted under the protection of argon gas. Before
Thermal properties of Al and Si based compositions
Fig. 1 shows the thermal behavior with melting temperature and latent heat of six compositions measured by DSC. From the curves, the melting point and latent heat can be obtained. Obviously, the PCMs absorb thermal energy during the melting process, all the compositions display sharp peaks and solid–liquid latent heats are higher than 450 J g−1, which is much higher than the typical value of about 300 J g−1 of the commonly used salts such as 56NaCl–44MgCl2 (mol.%) at 430 °C [25]. As shown in
Discussion
Six materials with different Al and Si compositions were studied as high temperature PCMs. The amount of heat stored in these materials depends on the composition of materials. The storage heat of Al–Si compositions increases with Si concentration because of the very high latent heat of Si. According to theoretical predictions [26], the latent heat of a material largely depends on the molar fraction of the elements, and the latent heat of pure Al and pure Si are about 397 and 1788 J g−1,
Conclusions
In this study, four binary Al–Si materials with different Al and Si ratios and two ternary materials with Fe or Ni added were studied as medium to high temperature PCMs for thermal energy storage applications. The results indicated that these Al and Si based materials are potentially good candidates for TES applications. The studied four binary materials: 87.8Al-12.2Si, 80Al–20Si, 70Al–30Si, 60Al–40Si, have heat storage capacity of ∼499, ∼553, ∼644, and ∼721 J g−1 with the same final melting
Acknowledgements
This work is supported by ARPA-E's HEATS program (Award Number: DE–AR000018, managed by Dr. Ravi Prasher and Dr. James Klausner) and the Open Research Subject of Key Laboratory of Special Materials and Preparation Technology of Sichuan Province (Award Number: szjj2015-087).
References (28)
- et al.
Review on thermal energy storage with phase change materials and applications materials and applications
Renew. Sustain. Energy Rev.
(2009) - et al.
Review on thermal energy storage with phase change: materials, heat transfer analysis and applications
Appl. Therm. Eng.
(2003) - et al.
Screening of high melting point phase change materials (PCM) in solar thermal concentrating technology based on CLFR
Sol. Energy
(2005) - et al.
Cascaded latent heat storage for parabolic trough solar power plants
Sol. Energy
(2007) - et al.
Heat transfer characteristics of thermal energy storage system using PCM capsules: a review
Renew. Sust. Energy Rev.
(2008) - et al.
Thermal conductivity enhancement of phase change materials for thermal energy storage: a review
Renew. Sust. Energy Rev.
(2011) - et al.
Experimental study of the characteristics of solidification of stearic acid in an annulus and its thermal conductivity enhancement
Energy Conv. Manag.
(2005) - et al.
Heat transfer enhancement of high temperature thermal energy storage using metal foams and expanded graphite
Sol. Energy Mater. Sol. C
(2011) - et al.
Experimental investigations on heat transfer in phase change materials (PCMs) embedded in porous materials
Appl. Therm. Eng.
(2011) - et al.
Thermal reliability test of Al-34%Mg-6%Zn alloy as latent heat storage material and corrosion of metal with respect to thermal cycling
Energy Convers. Manag.
(2007)
Experimental research on a kind of novel high temperature phase change storage heater
Energy Convers. Manag.
A review of solar collectors and thermal energy storage in solar thermal applications
Appl. Energy
High-temperature phase change materials for thermal energy storage
Renew. Sustain. Energy Rev.
Solar Thermal Energy Storage
Cited by (89)
Microencapsulation of Al-Si-Fe alloys for high-temperature thermal storage with excellent thermal cycling performance
2024, Chemical Engineering JournalNear zero thermal performance loss of Al-Si microcapsules with fibers network embedded Al<inf>2</inf>O<inf>3</inf>/AlN shell
2024, Journal of Materials Science and TechnologyEfficiency boost and financial analysis of the thermophotovoltaic power system by photonic potential
2024, Energy Conversion and ManagementHigh temperature oxidation properties of Al-Cu-Si alloys for latent heat energy storage
2023, Energy and Built Environment
- 1
These authors contributed equally to this work.