scholarly journals A Review on Shape-Stabilized Phase Change Materials for Latent Energy Storage in Buildings

2020 ◽  
Vol 12 (22) ◽  
pp. 9481
Author(s):  
Monika Gandhi ◽  
Ashok Kumar ◽  
Rajasekar Elangovan ◽  
Chandan Swaroop Meena ◽  
Kishor S. Kulkarni ◽  
...  

Many countries in the Global South have hot and dry climates with large diurnal temperature variations, which leads to large demand for space cooling—which is likely to increase with climate change. A common approach to dampen the indoor temperature fluctuations and thus reduce cooling energy demand is the use of thermal mass. However, the use of lightweight structures in many cities (e.g., high-rise structures, or for earthquake protection) precludes the use of traditional forms of thermal mass. Therefore, phase change materials (PCMs) are being widely developed as thermal energy storage systems for building applications. However, challenges such as leakage of PCMs in liquid state and their low thermal conductivity, still limit their applications in buildings. In this paper, we review the potential of Form or Shape-Stabilized Phase Change Materials (SSPCMs), which are developed by incorporating the PCM into a supporting matrix to prevent leakage in liquid state whilst improving thermal conductivity. We review different methods of preparation and the resultant thermal properties and chemical stability. We find good evidence in the literature for SSPCMs to reduce PCM leakage in liquid state, dampen indoor temperature fluctuations, and potentially alleviate peak energy demand by shifting peak loads to off-peak periods.

Author(s):  
D. Zhou ◽  
C. Y. Zhao

Phase change materials (PCMs) have been widely used for thermal energy storage systems due to their capability of storing and releasing large amounts of energy with a small volume and a moderate temperature variation. Most PCMs suffer the common problem of low thermal conductivity, being around 0.2 and 0.5 for paraffin and inorganic salts, respectively, which prolongs the charging and discharging period. In an attempt to improve the thermal conductivity of phase change materials, the graphite or metallic matrix is often embedded within PCMs to enhance the heat transfer. This paper presents an experimental study on heat transfer characteristics of PCMs embedded with open-celled metal foams. In this study both paraffin wax and calcium chloride hexahydrate are employed as the heat storage media. The transient heat transfer behavior is measured. Compared to the results of pure PCMs samples, the investigation shows that the additions of metal foams can double the overall heat transfer rate during the melting process. The results of calcium chloride hexahydrate are also compared with those of paraffin wax.


2019 ◽  
Vol 141 (5) ◽  
Author(s):  
S. Arunachalam

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.


Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3280
Author(s):  
Hong Gun Kim ◽  
Yong-Sun Kim ◽  
Lee Ku Kwac ◽  
Mira Park ◽  
Hye Kyoung Shin

This study researches the effect of phase change materials (PCMs) containing carbonized rice husks (CRHs) in wood plastic composites (WPCs) as roof finishing materials on roof-surface and indoor temperatures. A cool roof miniature model was prepared, and measurements were taken using three fixed temperatures of 30 to 32 °C, 35 to 37 °C, and 40 to 42 °C. Sodium sulfate decahydrate (Na2SO4·10H2O) and paraffin wax were selected as the PCMs. CRHs were used as additives to improve the thermal conductivities of the PCMs. At lower fixed temperatures such as 30 to 32 °C and 35 to 37 °C, the rates of increase of the surface temperatures of roofs containing CRHs with Na2SO4·10H2O, and paraffin wax, were observed to gradually decrease compared to those of the roofs without PCMs. The indoor temperatures for the above-mentioned PCMs containing CRHs were maintained to be lower than those of the indoors without PCMs. Additionally, as the CRH content in the PCM increased, the rates of increase of the roof-surface and indoor temperatures decreased due to a faster roof heat absorption by PCMs through the improved thermal conductivity of CRHs. However, under higher artificial temperatures such as 40 to 42 °C, Na2SO4·10H2O with CRHs exhibited no effect due to being out of latent heat range of Na2SO4·H2O. For paraffin wax, as CRH content increased, their roof- surface and indoor temperatures decreased. Especially, the surface temperature of the roof containing paraffin contained 5 wt.% CRHs reduced by 11 °C, and its indoor temperature dropped to 26.4 °C. The thermal conductivity of PCM was enhanced by the addition of CRHs. A suitable PCM selection in each location can result in the reduction of the roof-surface and indoor temperatures.


2015 ◽  
Vol 3 (16) ◽  
pp. 8526-8536 ◽  
Author(s):  
Tingting Qian ◽  
Jinhong Li ◽  
Xin Min ◽  
Weimin Guan ◽  
Yong Deng ◽  
...  

The thermal conductivity was 0.82 W m−1 K−1 for 7.2% AgNPs in PEG/diatomite, which was enhanced by 127% compared to PEG/diatomite.


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