Fabrication and characterization of phase change material-SiO2 nanocomposite for thermal energy storage in buildings

Fabrication and characterization of phase change material-SiO2 nanocomposite for thermal energy storage in buildings

Journal of Energy Storage 27 (2020) 101168 Contents lists available at ScienceDirect Journal of Energy Storage journal homepage: www.elsevier.com/lo...

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Journal of Energy Storage 27 (2020) 101168

Contents lists available at ScienceDirect

Journal of Energy Storage journal homepage: www.elsevier.com/locate/est

Fabrication and characterization of phase change material-SiO2 nanocomposite for thermal energy storage in buildings Samira Golestani Ranjbara, Ghodratollah Roudinia, Farahnaz Barahuieb, a b


Department of Materials Engineering, Faculty of Engineering, University of Sistan and Baluchestan, Zahedan, Iran Faculty of Industry & Mining (Khash), University of Sistan and Baluchestan, Zahedan, Iran



Keywords: Phase change material Nanocomposite Thermal properties SiO2 nanoparticle Thermal energy storage

Phase change materials (PCMs), which can absorb or release large latent heat over a defined temperature range while the phase transition occurs, have achieved huge attention due to the environmental concerns and energy crisis. In recent years, phase change material nanocomposites are extensively used in thermal energy storage and energy management. Here, a shape-stabilised PCM nanocomposite, consisting n-hetadecane as a PCM and SiO2 nanoparticles as a supportive material was successfully prepared using an impregnation method with different mass fraction of PCM. The formation of n-heptadecane-SiO2 nanocomposite was approved using X-ray diffraction, FTIR spectroscopy, and SEM studies. The melting and freezing latent heats of the nanocomposite reached 123.8 and 120.9 J/g, respectively, and the mass loading percentage of n-hetadecane in the nanocomposite which was estimated using DSC was about 54.6 wt.%. The resulting nanocomposite possessed excellent thermal cycling reliability and its thermal conductivity was also improved compared to pure n-heptadecane. Additionally, Gypsum composite board containing n-hetadecane-SiO2 nanocomposite showed acceptable temperature control performance compared to ordinary gypsum board and hence, the obtained nanocomposite can be suitable for storing thermal energy and indoor temperature regulation in the buildings.

1. Introduction Energy is an essential requirement for the economic growth and development of any country. High global energy demand and concern about the fossil fuels depletion, besides environmental impacts of these fuels consumption headed to the huge attention to conserve energy [1,2]. The utilization of latent heat of phase change materials (PCMs) for energy storage is considered one of the most promising and useful techniques for increasing energy efficiency and energy saving [3,4]. PCMs are characterized by storage and release of large amounts of thermal energy during phase transition processes at a certain temperature and high density of latent heat [5–7]. However, two major drawbacks of PCMs are low thermal conductivity and large volume change during their phase change processes which cause leakage of PCM, limit their practical applications in thermal energy storage [8,9]. The shape-stabilization is an effective strategy to prevent the leakage and enhance the energy storage capacity of PCM. Hence, selecting an appropriate inorganic carrier matrix for PCMs is a promising idea to enhance their performance. Various supporting materials including polymers [10,11], carbon materials [1,12], diatomite [13], metal oxide

nanoparticles [14,15] have been used to overcome these challenges. Amongst these, SiO2 nanoparticles as a vital inorganic amorphous material are promising as a supporting material for PCMs owing to its great thermal stability, flame-retardant feature, suitable thermal conductivity, non-toxicity, outstanding compatibility with construction materials, and excellent mechanical properties [16]. A review of the previous researches indicates that there has no report on the n-heptadecane-SiO2 nanocomposite fabrication and evaluation as a thermal energy storage material. Thus, in this paper, we used n-heptadecane as a PCM with wide range of mass fractions and SiO2 nanoparticle as a supportive material to form n-heptadecane – SiO2 nanocomposite through impregnation method (Fig. 1). The morphology and structural investigations of the nanocomposite were performed by XRD, FTIR and SEM techniques. Thermal storage capacity of the nanocomposite was searched using DSC analysis and thermal cycling test was made to study the thermal reliability and reusability of the nanocomposite. The thermo-regulating performances of the PCM nanocomposite in gypsum was also measured and evaluated by developing the small test room to simulate a building.

Corresponding author. E-mail address: [email protected] (F. Barahuie).

https://doi.org/10.1016/j.est.2019.101168 Received 10 October 2019; Received in revised form 29 November 2019; Accepted 17 December 2019 2352-152X/ © 2019 Elsevier Ltd. All rights reserved.

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Fig. 1. Schematic description of n-heptadecane-SiO2 nanocomposite synthesis.

2. Materials and methods

mixing 0, 1, 4, and 8 wt.% of A5 nanocomposite, 45 wt.% of water, and gypsum powder. A homogenous slurry was obtained by continues mixing with vigorous agitation for at least 4 min and then was poured into a mould (100 × 100 × 20 mm) to dry at room temperature for at least 24 h. The moulded samples were then taken down and air dried and used for further analysis.

2.1. Materials Absolute ethanol was supplied from R&M Chemicals (UK). SiO2 nanoparticle (20–30 nm) was obtained from US Research Nanomaterials, Inc, while n-heptadecane (C17H36, molecular weight 240.475 g/mol) was acquired from Merck (Germany).

2.4. Testing of thermal storage and temperature control performance

2.2. Fabrication of PCM-SiO2 nanocomposite

The evaluation of thermal energy storage and temperature control performance of A5 nanocomposite in the building materials was determined using a designed small test room (Fig. 2). The test room with internal dimensions of 100 mm × 100 mm × 100 mm was sealed with polystyrene boards, which function as an insulation. In order to compare the heat storage effects, the ordinary gypsum board as a control and the gypsum composite boards containing 1, 4, and 8 wt.% of A5 nanocomposite were used as the top boards of the room, respectively. A 500 W halogen tungsten lamp as the heat source was placed above the top board of the test room at the distance of 25 cm. During light irradiation, the outside wall temperature of the top board was controlled to reach a temperature of 40 ± 2 °C. Prior to the test, the respective temperatures of the outside wall, the inside wall, and the indoor test room were similar to the temperature of the environment (17 ± 2 °C) and throughout the test the ambient temperature was maintained at 17 ± 2 °C. Four thermocouples linked to a data logger were inserted in the outside wallboard, inside wallboard, in the centre of the test room and environment to record the temperature variations at all four points. When the lamp was switched on, the indoor temperature variation of the small test room started to be recorded. The lamp radiation was applied to the room for around 2 h and the recording of the indoor room temperature variation continued until the indoor test room cooled to room temperature.

The synthesis of n-heptadecane- SiO2 nanocomposite was done through impregnation technique. The melted n-heptadecane was dissolved in absolute ethanol. Around 0.5 g, SiO2 nanoparticles were also dispersed in absolute ethanol and then dissolved n-heptadecane was slowly added into the SiO2 nanoparticles solution and the mixture was stirred at 600 rpm for 4 h. The white powder was obtained after drying in an oven at 60 ℃ overnight. The amount of n-heptadecane in the nanocomposite was varied from 0.2 to 1 g and the obtained n-heptadecane- SiO2 nanocomposites are referred to as A1, A2, A3, A4 and A5 nanocomposite, respectively. Table 1 indicates the compositions of the nanocomposites. 2.3. Preparation of A5 nanocomposite-gypsum composite The A5 nanocomposite-gypsum composite boards were produced by Table 1 N-heptadecane and SiO2 nanoparticles compositions used for the preparation of the n-heptadecane-SiO2 nanocomposites. Nanocomposite


N-heptadecane (g)

SiO2 nanoparticles (g)

A1 A2 A3 A4 A5

0.4 0.8 1.2 1.6 2

0.2 0.4 0.6 0.8 1

0.5 0.5 0.5 0.5 0.5

2.5. Characterization The 2








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Fig. 2. Schematic of devices for the thermal performance evaluation of A5 nanocomposite-gypsum composite boards.

nanocomposite-gypsum composite were studied using a EM3900M scanning electron microscope (SEM). X-ray patterns of SiO2 nanoparticle and n-heptadecane- SiO2 nanocomposites were gained using powder X-ray diffraction (Shimadzu XRD-6000). A scanning range was 10–60˚ (2Ɵ) with a scanning rate of 4 degree/min. Thermal properties, such as melting temperature, crystallization temperature and enthalpy (latent heat) of A5 nanocomposite were measured using a DSC (differential scanning calorimeter 822e, METTLER TOLEDO) equipped with a refrigerated cooling system. The measurements were performed at a heating rate of 10 °C/min, at −20 °C to 70 °C for heating cycle stage and 70 °C to −20 °C for cooling cycle stage under a constant nitrogen atmosphere at a flow rate of 60 mL/min. Fourier transform infrared (FT-IR) spectra of SiO2 nanoparticle and n-heptadecane- SiO2 nanocomposites were recorded over the range of 400–4000 cm−1 on a PerkinElmer 1752 Spectrophotometer (Waltham, MA, USA) using the KBr disc method with a 1% sample in 200 mg of spectroscopic-grade KBr, with the pellets made by pressing at 10 t.

3. Results and discussion 3.1. Powder X-ray diffraction Fig. 3 exhibits the XRD pattern of SiO2 nanoparticle (A), and nheptadecane-SiO2 nanocomposites with different weight percentages of n-heptadecane, A1-A5 (B-F). The XRD pattern of SiO2 nanoparticle (Fig. 3A) demonstrates an amorphous structure with a broad peak at 2θ = =15–27◦ [16,17]. It can be seen from the XRD pattern of A5 nanocomposite (Fig. 3F) that the presence of n-heptadecane was reflected by the observation of two peaks at 2Ɵ = 21.2 and 22.9° [18], while the diffraction peak of SiO2 nanoparticle in the nanocomposite was appeared at 2Ɵ = =15–27◦. This result specifies the structure of nheptadecane and SiO2 nanoparticle were not changed in the nanocomposite and there was only physical interaction yet no chemical reaction between n-heptadecane and SiO2 nanoparticles. However, the crystalline structure of n-heptadecane was not observed in the XRD

Fig. 3. Powder X-ray diffraction pattern of SiO2 nanoparticles (A), n-heptadecane-SiO2 nanocomposites with different weight percentages of n-heptadecane A1–A5 (B–F).

patterns of A1–A4 nanocomposites (Fig. 3B–E) and this may be attributed to the small fraction of n-heptadecane into the SiO2 nanoparticles framework.


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Fig. 5. DSC curves of A5 nanocomposite and A5 nanocomposite-gypsum composite.

be clearly seen from Fig. 5 that, A5 nanocomposite has obvious exothermic and endothermic behaviours during heating and cooling periods, indicating its reversible thermal storage and release capacities. Melting and freezing temperatures and latent heat for the melting and crystallization processes of A5 nanocomposite are shown in Table 2. As observed from Fig. 5, the melting temperature and latent heat of A5 nanocomposite are 25.6 °C and 123.8 J/g and reach to 28.0 °C and 79.7 J/g in the A5 nanocomposite-gypsum composite, and the DSC curve of A5 nanocomposite-gypsum composite has a lower intensity than the DSC curve of A5 nanocomposite. This can be due to the gypsum presence as an impurity in the A5 nanocomposite-gypsum composite. The encapsulation efficiency of n-heptadecane in the A5 nanocomposite can be calculated based on the enthalpy of pure n-heptadecane and A5 nanocomposite using the following equation:

Fig. 4. Fourier transform infrared spectra of SiO2 nanoparticle (A), and nheptadecane-SiO2 nanocomposites with different weight percentages of nheptadecane, A1–A5 (B–F).

3.2. FTIR spectroscopy FTIR spectroscopy is applied to identify the formation of nanocomposite. The FTIR spectrum of SiO2 nanoparticle (A), and n-heptadecane-SiO2 nanocomposites with different weight percentages of nheptadecane, A1–A5 (B–F) are given in Fig. 4. In the FTIR spectrum of SiO2 (Fig. 4A), the characteristic bands at 1072 cm−1, 807 cm−1 and 461 cm−1 are associated to the vibration of SieOeSi [17,19]. The contribution of n-heptadecane to the FTIR spectra of the nanocomposites A1-A5 (Fig. 4B–F) were observed with asymmetrical and symmetrical CeH stretching vibrations of CH3 and CH2 groups at 2956, 2916, and 2849 cm−1 respectively, and bending vibrations of CeH at 1466 and 1380 cm−1. The in plane rocking vibration of CH2 in nheptadecane was at 722 cm−1 [18,20]. The intensity of the FTIR peaks boosted with increasing n-heptadecane content in the nanocomposites. However, The FTIR spectra of nanocomposites (Fig. 4B–F) clearly show that there is no shift in the absorption peaks of SiO2 nanoparticles. The characteristic peaks of SiO2 nanoparticles in the nanocomposites were detected at 1069, 805, and 459 cm−1corresponded to the bending vibration of SieOeSi. In addition, the observed bands at 3434 and 1626 cm−1 was assigned to the stretching and bending vibration of OH group, respectively. In Fig. 4(B–F), nanocomposites show the characteristic absorption peaks of n-heptadecane and SiO2 nanoparticles, and no new characteristic peaks are observed in the FTIR spectra of nanocomposites. It is concluded that n-heptadecane was successfully inserted into the SiO2 nanoparticles framework and there is only physical interaction yet no chemical reaction between n-heptadecane and SiO2 nanoparticles, which is consistent with the XRD result.

N−heptadecane content in nanocomposite (wt.%)=(ΔHnanocomposite /ΔHn − heptadecane) × 100 where ΔHnanocomposite is the enthalpy of melting for the A5 nanocomposite and ΔHn-heptadecane is the enthalpy of melting for the pure nheptadecane. The n-heptadecane content in the A5 nanocomposite was determined to be approximately 54.6 wt.% [20,21]. 3.4. Surface morphology of A5 nanocomposite and A5 nanocompositegypsum composite The surface morphology of A5 nanocomposite and gypsum composite board sample containing 8 wt.% of A5 nanocomposite, observed using a scanning electron microscope, is exhibited in Fig. 6. The A5 nanocomposite (Fig. 6A and B) displays to have nanosize particles with spherical shape. Although, it can also be seen that the particle size of nanocomposites is bigger than the SiO2 nanoparticles (20–30 nm). The result shows that the n-heptadecane has been imbedded into the three dimensional nano-network of SiO2 nanoparticles, which prevents the leakage of n-heptadecane from the nanocomposite during the phase change processes and even at over the melting temperature [22]. Furthermore, SEM was also used to observe the A5 nanocomposite distribution in the gypsum matrix. In this study, a gypsum composite board sample containing 8 wt.% of A5 nanocomposite was chosen for further analysis. Fig. 6C and D indicate that the A5 nanocomposites were dispersed irregularly between the gypsum particles due to the difference in density of the gypsum powder and A5 nanocomposites, and also the properties of the A5 nanocomposites themselves, which tend to stick to one another. Thus, some areas contained higher

3.3. Phase change performance of the A5 nanocomposite DSC analysis was performed in order to assess the heat storage capacity of the A5 nanocomposite which is determined by phase change temperature and phase change enthalpy. Fig. 5 presents the DSC curves of A5 nanocomposite and A5 nanocomposite-gypsum composite. It can 4

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Table 2 Thermal properties of A5 nanocomposite. Sample

Tom (°C)

Tpm (°C)

Tem (°C)

ΔHm (J/g)

Toc (°C)

Tpc (°C)

Tec (°C)

ΔHc (J/g)

A5 nanocomposite









indicated that the PCM composite wallboards can decrease the indoor temperature fluctuation compared to the control test room. For example, Sarabandi et al. [18] reported that the maximum temperature difference for the gypsum boards containing 5 and 10 wt.% of n-heptadecane-activated carbon composite was around 5.0 °C and 9.0 °C, respectively. Khadiran et al. [23] tested the charge and discharge rate of gypsum composite boards containing 0, and 10 wt.% of n-octadecane encapsulated in nano-sized styrene-methyl–methacrylate copolymer shells, and reported that the maximum indoor temperature was reduced by 3.0 °C. Karaipekli and Sari [24] fabricated three different gypsum plasters including capric acid– palmitic acid/pumice, dodecanol/pumice, and n-heptadecane/pumic composites and evaluated their thermal performances. The maximum temperature difference of three different gypsum plasters including capric acid– palmitic acid/pumice, dodecanol/pumice, and n-heptadecane/pumic composites was found to be 0.8 °C, 2.3 °C and 2.1 °C, respectively for 48 min heating time. Sari et al. [25] investigated the thermal performance of cement plasters with and without capric acid- stearic acid eutectic mixture- sepiolite composite. The indoor temperature was raised from 15.5 °C to about 43.0 °C at 105 min compared to the 85 min for cement plaster without PCMs composite (control test room). Shadnia et al. [26] prepared geopolymer-PCM mortar slabs and observed the maximum temperature reduction was about 4.4–5.5 °C. Fang and Zhang [27] evaluated two different gypsum boards containing 20 and 50 wt.% of RT20/montmorilonite composite and found that the maximum temperature difference was 5 °C and 9 °C for the gypsum boards containing 20 and 50 wt.% of RT20/montmorilonite composite, respectively. Sari [28] examined the thermal energy storage and release rate of bentoniteparaffin composite board and discovered the maximum temperature was 2.09 °C lower than the control cell made with bentonite only board. Though, the results of this work are in good agreement with the previous studies. Three gypsum wallboards containing 0, 1, 4, and 8 wt. % of A5 nanocomposite were evaluated and observed 1.0 °C, 3.8 °C and 5.7 °C maximum temperature difference, respectively, for about 2 h heating period.

numbers of A5 nanocomposites than others and there was no uniform distribution of the A5 nanocomposites in the gypsum matrix. In addition, the A5 nanocomposites were very compatible with the gypsum powders during the fabrication of A5 nanocomposite-gypsum composites. 3.5. Thermal conductivity analysis of A5 nanocomposite One of the important parameters which, affects PCM nanocomposite applications is the rate of heat storage (charge) and release (discharge), during melting and freezing processes and it extremely depends on the thermal conductivity of the PCM nanocomposite. A thermal conductivity device (KD-2 Pro) was used to measure thermal conductivity of pure n-heptadecane, and A5 nanocomposite. The test was performed using the hot wire method at temperature 24 ± 2 °C. The measured thermal conductivity for n-heptadecane was around 0.1662 W/m K, and the presence of SiO2 nanoparticles increased thermal conductivity of the A5 nanocomposite to 0.2835 W/m K. These results are consistent with the results in earlier researches which show that the addition of SiO2 nanoparticles into PCM improves its thermal conductivity [3,16]. 3.6. Thermal reliability of A5 nanocomposite The thermal cycling test was done for 500 cycles for A5 nanocomposite and no leakage of n-heptadecane from the nanocomposite was observed during thermal cycling test. The chemical stability of the A5 nanocomposite before and after the thermal cycling test is exhibited in Fig. 7. There was no additional new absorption peaks and significant change in shape and frequency values of the original peaks after 500 thermal cycles. This result shows that the structure of the A5 nanocomposite was not affected by the repeated heating and cooling cycles and the A5 nanocompsite has good reliability and durability in terms of chemical structure. It is evident that the A5 nanocompsite showed a good thermal stability and reliability which is one of the most important factors in its practical applications.

4. Conclusion

3.7. Smart temperature-control properties of A5 nanocomposite in building materials

A novel PCM nanocomposite with improved thermal conductivity and great phase change behaviour, and excellent thermal stability was fabricated based on n-heptadecane core and SiO2 nanoparticles framework. DSC analysis indicated that A5 nanocomposite had an enthalpy of 123.8 and 120.9 J/g for melting and crystallization, respectively, and accelerated thermal cycling test certified that A5 nanocomposite showed a good thermal reliability, even after 500 melting/freezing cycles. In addition, the thermal performance tests of A5 nanocomposite in the building materials revealed that the resulting nanocomposite can keep indoor temperature at comfortable range and the function was enhanced with the increase in the mass ratio of A5 nanocomposite in the gypsum composite boards. Therefore, they can be used as promising building materials for thermal energy storage in the smart buildings.

The evaluation of thermal performance of A5 nanocomposite in gypsum was accomplished by investigating their effects on the indoor temperatures of the small test rooms. Fig. 8 indicates the indoor temperature profiles of the small test rooms with the top boards containing A5 nanocomposite at mass percentages of 0, 1, 4 and 8 wt.%. As seen in the Fig. 8, the temperature increasing rate reduced as the mass percentage of A5 nanocomposite in the top board increased. Therefore, the indoor temperature variation curves decreased from 41.2 °C to 40.2 °C, 37.4 °C and 35.5 °C for the test room when the top board contained 0, 1, 4 and 8 wt.%, respectively. These results imply that A5 nanocompositegypsum composite demonstrated good thermal performance and can be used for the thermal energy storage purposes and temperature control in building applications. 3.8. Comparison of temperature control performance of A5 nanocompositegypsum composite with literature results

CRediT authorship contribution statement Samira Golestani Ranjbar: Formal analysis, Data curation. Ghodratollah Roudini: Conceptualization, Formal analysis, Supervision, Validation. Farahnaz Barahuie: Conceptualization, Formal analysis, Supervision, Validation, Writing - original draft,

Till date many studies have been done to evaluate the temperature control performance of PCM composites in building materials as wallboards or plasterboards of the test room and most of these works 5

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Fig. 7. FTIR spectra of A5 nanocomposite (A) after 1000 thermal cycles (B).

Fig. 8. Indoor temperature variation profiles of the small test rooms where the composite boards contained different mass percentages of A5 nanocomposite.

Writing - review & editing. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Supplementary materials Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.est.2019.101168. References [1] M. He, L. Yang, W. Lin, J. Chen, X. Mao, Z. Ma, Preparation, thermal characterization and examination of phase change materials (PCMs) enhanced by carbonbased nanoparticles for solar thermal energy storage, J. Energy Storage 25 (2019) 100874. [2] Y. Zhao, X. Min, Z. Huang, Y. Liu, X. Wu, M. Fan, Honeycomb-like structured biological porous carbon encapsulating PEG: a shape-stable phase change material with enhanced thermal conductivity for thermal energy storage, Energy Build. 158 (2018) 1049–1062. [3] Y. Zhang, J. Zhang, X. Lia, X. Wu, Preparation of hydrophobic lauric acid/SiO2 shape-stabilized phase change materials for thermal energy storage, J. Energy Storage 21 (2019) 611–617. [4] X. Chen, Y. Zhao, Y. Zhang, A. Lu, X. Li, L. Liu, G. Qin, Z. Fang, J. Zhang, Y. Liu, A

Fig. 6. Scanning electron micrograph of A5 nanocomposite (A and B), and gypsum composite board containing 8 wt.% of A5 nanocomposite (C and D).


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