Effect of the in situ synthesis of nano-ZnO on the specific heat capacity of solar salt

doi:10.19799/j.cnki.2095-4239.2019.0297

Abstract

Abstract:

Solar salt as a heat storage material with optimum thermal properties has promising application prospects with respect to the thermal power and heat storage of solar energy. By enhancing the specific heat capacity of solar salt, it is possible to considerably improve the thermal storage capacity. In this study, nano-ZnO flakes were synthesized in situ in solar salt via the hydrothermal method, and granular ZnO was synthesized in situ in solar salt via the combustion method. XRD, EDS, FE-SEM, TEM, and DSC were used to study the effect of nano-ZnO on the structure and properties of solar salt. Results show that the size of ZnO nanosheets is between 50 and 200 nm, the size of ZnO nanoparticles is between 30 and 200 nm, and nano-ZnO has good dispersibility in salt. When the weight content of ZnO nanoflakes in solar salt was 1%, the specific heat of the solid and liquid of modified solar salt reached 2.09 and 1.78 J·(g·℃)^-1, which denote an increase of 71.3% and 38.0%, respectively. When the ZnO nanoparticle weight content in solar salt was 0.75%, the solid and liquid specific heat of modified solar salt reached 2.22 and 1.88 J·(g·℃)^-1, which denote an increase of 82.0% and 45.7%, respectively. The addition of granular ZnO has a better specific heat capacity enhancement effect on solar salt than that of ZnO nanoflakes.

Key words: Solar salt, ZnO nanosheets, ZnO nanoparticles, in-situ method, specific heat capacity

CLC Number:

TK 11

XIONG Feng, CHENG Xiaomin, LI Yuanyuan, DAI Pei, WANG Xiuli, ZHONG Hao. Effect of the in situ synthesis of nano-ZnO on the specific heat capacity of solar salt[J]. Energy Storage Science and Technology, 2020, 9(2): 440-447.

Figures/Tables 14

Table 1

Fig.1

Table 2

Fig.2

Fig.3

Fig.4

Fig.5

Fig.6

Fig.7

Fig.8

Table 3

Fig.9

Fig. 10

Table 4

References 22

1	KENISARIN M , MAHKAMOV K . Solar energy storage using phase change materials [J]. Renewable and Sustainable Energy Reviews, 2007, 11(9): 1913-1965.
2	谢望平, 汪南, 朱冬生, 等 . 相变材料强化传热研究进展[J]. 化工进展, 2008, 27(2): 190-195.
	XIE Wangping , WANG Nan , ZHU Dongsheng , et al . Review of heat transfer enhancement of the PCMs[J]. Chemical Industry and Engineering Progress, 2008, 27(2): 190-195.
3	葛志伟, 叶锋 . 中高温储热材料的研究现状与展望[J]. 储能科学与技术, 2012, 1(2): 89-102.
	GE Zhiwei , YE Feng , LasfarguesMATHIEU, et al . Recent progress and prospective of medium and high temperatures thermal energy storage materials[J]. Energy Storage Science and Technology, 2012, 1(2): 89-102.
4	BAUER T , PFLEGER N , BREIDENBACH N , et al . Material aspects of Solar salt for sensible heat storage[J]. Applied Energy, 2013, 111(11): 1114-1119
5	JOURABIAN M , FARHADI M , SEDIGHI K . On the expedited melting of phase change material (PCM) through dispersion of nanoparticles in the thermal storage unit[J]. Computers & Mathematics with Applications, 2014, 67(7): 1358-1372.
6	陈虎, 吴玉庭, 鹿院卫, 等 . 熔盐纳米流体的研究进展[J]. 储能科学与技术, 2018, 7(1): 48-55.
	CHEN Hu , WU Yuting , LU Yuanwei , MA Chongfang . A review on molten salt-based nanofluids: Recent developments[J]. Energy Storage Science and Technology, 2018, 7(1): 48-55.
7	MONDRAGóNROSA, JULIáJ .ENRIQUE, CABEDO L, et al . On the relationship between the specific heat enhancement of salt-based nanofluids and the ionic exchange capacity of nanoparticles[J]. Scientific Reports, 2018, 8(1): 1-12.
8	ERCOLE D , MANCA O , VAFAI K . An investigation of thermal characteristics of eutectic molten salt-based nanofluids[J]. International Communications in Heat and Mass Transfer, 2017, 87(7): 98-104.
9	DUDDA B , SHIN D . Effect of nanoparticle dispersion on specific heat capacity of a binary nitrate salt eutectic for concentrated solar power applications[J]. International Journal of Thermal Sciences, 2013, 69(7): 37-42.
10	TENG T P , YU C C . Characteristics of phase-change materials containing oxide nano-additives for thermal storage[J]. Nanoscale Research Letters, 2012, 7(1): 1-10.
11	MATHIEU L , QIAO G , HUI C , et al . Mechanical dispersion of nanoparticles and its effect on the specific heat capacity of impure binary nitrate salt mixtures[J]. Nanomaterials, 2015, 5(3): 1136-1146.
12	ZHU Peining , WU Yongzhi , REDDY M V , et al . TiO2 nanoparticles synthesized by the molten salt method as a dual functional material for dye-sensitized solar cells[J]. RSC Advances, 2012, 2(12): 5123-5126.
13	JO B, BANERJEE D . Enhanced specific heat capacity of molten salt-based nanomaterials: Effects of nanoparticle dispersion and solvent material[J]. Acta Materialia, 2014, 75(8): 80-91.
14	LASFARGUES M , BELL A , DING Y . In situ production of titanium dioxide nanoparticles in molten salt phase for thermal energy storage and heat-transfer fluid applications[J]. Journal of Nanoparticle Research, 2016, 18(6): 150-160.
15	HUANG Yi , CHENG Xiaomin , LI Yuanyuan , et al . Effect of sol-gel combustion synthesis of nanoparticles on thermal properties of KNO3-NaNO3[J]. Solar Energy Materials and Solar Cells, 2018, 188(9): 190-201.
16	HUANG Y , CHENG X , LI Y , et al . Effect of in-situ synthesized nano-MgO on thermal properties of NaNO3-KNO3[J]. Solar Energy, 2018, 160(1): 208-215.
17	冷光辉, 蓝志鹏, 葛志伟, 等 . 储热材料研究进展[J]. 储能科学与技术, 2015, 4(2): 119-130.
	LENG Guanghui , LAN Zhipeng , GE Zhiwei , et al . Recent progress in thermal energy storage materials[J]. Energy Storage Science and Technology, 2015, 4(2): 119-130.
18	ZHAO X , LOU F , LI M , et al . Sol-gel-based hydrothermal method for the synthesis of 3D flower-like ZnO microstructures composed of nanosheets for photocatalytic applications[J]. Ceramics International, 2014, 40(4): 5507-5514.
19	KhateebaIrshad, Khan Muhammad Tahir, AdilMurtaza . Synthesis and characterization of transition-metals-doped ZnO nanoparticles by sol-gel auto-combustion method[J]. Physica B Condensed Matter, 2018, 543(8): 1-6.
20	MATHIEU L , GRAHAM S , MUHAMMAD A , et al . In situ production of copper oxide nanoparticles in a binary molten salt for concentrated solar power plant applications[J]. Materials, 2017, 10(5): 537-546.
21	LUO Y , DU X , AWAD A , et al . Thermal energy storage enhancement of a binary molten salt via in-situ produced nanoparticles[J]. International Journal of Heat and Mass Transfer, 2017, 104: 658-664.
22	DUDDA B , SHIN D . Effect of nanoparticle dispersion on specific heat capacity of a binary nitrate salt eutectic for concentrated solar power applications[J]. International Journal of Thermal Sciences, 2013, 69: 37-42.

样品	Zn (CH₃COO) ₂·2H₂O /g	NaOH/g	ZnO纳米片含量/%	太阳盐/g
0^#	0	0	0	2
1^#	0.027	0.025	0.5	2
2^#	0.054	0.049	1	2
3^#	0.081	0.074	1.5	2
4^#	0.111	0.101	2	2

样品	Zn (NO₃)₂ ·6H₂O /g	C₆H₈O₇ ·H₂O /g	ZnO纳米颗粒/%	太阳盐/g
5^#	0.098	0.022	0.5	5
6^#	0.138	0.033	0.75	5
7^#	0.185	0.044	1	5
8^#	0.231	0.055	1.25	5
9^#	0.278	0.066	1.5	5

Sample	比热容 /J·(g·℃)^-1
Sample	固态	液态
0^#	1.22	1.29
1^#	1.78（45.9%）	1.45（12.4%）
2^#	2.09（71.3%）	1.78（38.0%）
3^#	1.84（50.8%）	1.40（8.5%）
4^#	1.76（44.3%）	1.30（0.8%）
5^#	1.68（37.7%）	1.48（14.7%）
6^#	2.20（82.0%）	1.88（45.7%）
7^#	2.03（71.3%）	1.78（40.2%）
8^#	1.60（31.1%）	1.39（7.8%）
9^#	1.58（29.5%）	1.31（1.6%）

Sample	ΔH /kJ·kg^-1	T _M /℃	T _E/℃
0^#	111.9	218.3	247.1
1^#	97.2	203.8	241.3
2^#	88.3	202.1	237.4
3^#	76.3	201.4	237.0
4^#	66.3	200.2	235.6
5^#	106.7	214.1	239.9
6^#	104.2	211.8	236.6
7^#	100.8	215.2	236.1
8^#	93.7	211.4	236.4
9^#	96.5	214.4	233.8

[1]	Pei DAI, Xiaomin CHENG, Yuanyuan LI. Effect of nano-NiO synthesized by sol-gel combustion on the microstructures and thermal properties of solar salt [J]. Energy Storage Science and Technology, 2020, 9(6): 1760-1767.
[2]	Zhao LI, Baorang LI, Liu CUI, Xiaoze DU. Stability of the thermal performances of molten salt-based nanofluid [J]. Energy Storage Science and Technology, 2020, 9(6): 1775-1783.
[3]	MEHVISH Tariq, CHENG Xiaomin, LI yuanyuan, HUANG Yi, LI Ge, WANG Xiuli, ZHU Shilei, WAQAR Khan. Influence of carbon nanotubes and nano-alumina on the thermal performance of nitrate phase change materials for thermal storage [J]. Energy Storage Science and Technology, 2018, 7(S1): 47-53.
[4]	WANG Caixia1, HUANG Yun1, YAO Hua1, YE Feng1, YANG Jun1, DING Yulong2. Review of recent advances in research of nanofluids [J]. Energy Storage Science and Technology, 2017, 6(1): 24-34.