Abstract
Solid-phase thermophysical properties of solar salt (a mixture of NaNO3 and KNO3) influence the performance of sensible heat and latent heat thermal energy storage systems. Solar salt’s lower thermal conductivity imparts kinetic limitation during the discharge cycle and hence its thermal conductivity needs to be enhanced. This work is aimed at studying the influence of MWCNT incorporation on the improvement of solid-phase thermophysical properties of solar salt. Accordingly, experiments were carried out to study the influence of method of MWCNT-solar salt preparation, MWCNT concentration and temperature on solid-phase specific heat and thermal conductivity. Our results reveal that 0.5 wt% MWCNT-solar salt composite prepared by ultrasonication and milling for an appropriate time lead to 18.3% enhancement in the solid-phase thermal conductivity and 18% enhancement in the solid-phase specific heat. In addition, the total energy storage capacity over the temperature range of 50–270 °C (including solid–liquid phase change) is amplified by 11.5%. These results augur well for deployment of the MWCNT-solar salt composite in the thermal energy storage system as a storage medium.
Research highlights
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MWCNT-solar salt composites prepared and characterized.
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Solid-phase thermal conductivity and specific heat enhanced with addition of MWCNT.
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α-KNO3–β-KNO3 transition affected by addition of MWCNT @ 0.5 wt%.
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Thermal conductivity enhancement influenced by reduced α-KNO3–β-KNO3 transition.
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Solar salt nanoparticles in composites augment solid-phase specific heat.
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Abbreviations
- MWCNT:
-
Multi-walled carbon nanotube
- PW:
-
Peta watt
- LHTES:
-
Latent heat thermal energy storage
- PCM:
-
Phase change material
- TES:
-
Thermal energy storage
- ρ:
-
Density (kg m−3)
- α:
-
Alpha phase
- β:
-
Beta phase
- γ:
-
Gamma phase
- \(\emptyset\) :
-
Volume fraction
- Cp :
-
Specific heat (J g−1 K−1)
- dT:
-
Temperature range
- nf:
-
Nanofluid
- np:
-
Nanoparticle
- bf:
-
Bulkfluid
- comp:
-
MWCNT-solar salt composite
- ss:
-
Solar salt
References
Andreu-Cabedo P, Mondragon R, Hernandez L et al (2014) Increment of specific heat capacity of solar salt with SiO2 nanoparticles. Nanoscale Res Lett 9:582. https://doi.org/10.1186/1556-276X-9-582
Awad A, Burns A, Waleed M et al (2018) Latent and sensible energy storage enhancement of nano-nitrate molten salt. Sol Energy 172:191–197. https://doi.org/10.1016/j.solener.2018.04.012
Buongiorno J (2006) Convective transport in nanofluids. J Heat Transf 128:240. https://doi.org/10.1115/1.2150834
Cáceres G, Montané M, Nasirov S, O’Ryan R (2016) Review of thermal materials for CSP plants and LCOE evaluation for performance improvement using chilean strategic minerals: lithium salts and copper foams. Sustainability 8:106. https://doi.org/10.3390/su8020106
Chieruzzi M, Cerritelli GF, Miliozzi A, Kenny JM (2013) Effect of nanoparticles on heat capacity of nanofluids based on molten salts as PCM for thermal energy storage. Nanoscale Res Lett 8:1–9. https://doi.org/10.1186/1556-276X-8-448
Chieruzzi M, Miliozzi A, Crescenzi T et al (2015) A new phase change material based on potassium nitrate with silica and alumina nanoparticles for thermal energy storage. Nanoscale Res Lett. https://doi.org/10.1186/s11671-015-0984-2
Christensen A, Norby P, Hanson JC, Shimada S (1996) Phase transition of KNO3 monitored by synchrotron X-ray powder diffraction. J Appl Crystallogr 29:265–269. https://doi.org/10.1107/S0021889895015664
Dudda B, Shin D (2013) Effect of nanoparticle dispersion on specific heat capacity of a binary nitrate salt eutectic for concentrated solar power applications. Int J Therm Sci 69:37–42. https://doi.org/10.1016/j.ijthermalsci.2013.02.003
González-Roubaud E, Pérez-Osorio D, Prieto C (2017) Review of commercial thermal energy storage in concentrated solar power plants: steam vs. molten salts. Renew Sustain Energy Rev 80:133–148. https://doi.org/10.1016/j.rser.2017.05.084
Guo Q, Wang T (2015) Study on preparation and thermal properties of sodium nitrate/silica composite as shape-stabilized phase change material. Thermochim Acta 613:66–70. https://doi.org/10.1016/J.TCA.2015.05.023
Hamdy E, Ebrahim S, Abulfotuh F, Soliman M (2017) Effect of multi-walled carbon nanotubes on thermal properties of nitrate molten salts. Proc 2016 Int Renew Sustain Energy Conf IRSEC 2016 317–320. https://doi.org/10.1109/irsec.2016.7983997
Hu Y, He Y, Zhang Z, Wen D (2017) Effect of Al2O3 nanoparticle dispersion on the specific heat capacity of a eutectic binary nitrate salt for solar power applications. Energy Convers Manag 142:366–373. https://doi.org/10.1016/j.enconman.2017.03.062
Khanafer K, Tavakkoli F, Vafai K, AlAmiri A (2015) A critical investigation of the anomalous behavior of molten salt-based nanofluids. Int Commun Heat Mass Transf 69:51–58. https://doi.org/10.1016/j.icheatmasstransfer.2015.10.002
Kibria MA, Anisur MR, Mahfuz MH et al (2015) A review on thermophysical properties of nanoparticle dispersed phase change materials. Energy Convers Manag 95:69–89. https://doi.org/10.1016/J.ENCONMAN.2015.02.028
Kim H, Jo B (2018) Anomalous increase in specific heat of binary molten salt-based graphite nanofluids for thermal energy storage. Appl Sci 8:1305. https://doi.org/10.3390/app8081305
Kingson Solomon Jeevaraj. A PM (2015) Synthesis and characterization of multi walled carbon nanotube nanofluids. Shodhganga: A Reservoir of Indian Theses. http://hdl.handle.net/10603/119268
Lachheb M, Adili A, Albouchi F et al (2016) Thermal properties improvement of Lithium nitrate/Graphite composite phase change materials. Appl Therm Eng 102:922–931. https://doi.org/10.1016/j.applthermaleng.2016.03.167
Lasfargues M, Bell A, Ding Y (2016) In situ production of titanium dioxide nanoparticles in molten salt phase for thermal energy storage and heat-transfer fluid applications. J Nanoparticle Res 18:150. https://doi.org/10.1007/s11051-016-3460-8
Lasfargues M, Geng Q, Cao H, Ding Y (2015) Mechanical dispersion of nanoparticles and its effect on the specific heat capacity of impure binary nitrate salt mixtures. Nanomaterials 5:1136–1146. https://doi.org/10.3390/nano5031136
Leijon M, Skoglund A, Waters R et al (2010) On the physics of power, energy and economics of renewable electric energy sources—Part I. Renew Energy 35:1729–1734. https://doi.org/10.1016/j.renene.2009.10.030
Luo Y, Du X, Awad A, Wen D (2017) Thermal energy storage enhancement of a binary molten salt via in-situ produced nanoparticles. Int J Heat Mass Transf 104:658–664. https://doi.org/10.1016/j.ijheatmasstransfer.2016.09.004
Malhotra T (2001) Solar energy in India. Refocus 2:20–22. https://doi.org/10.1016/S1471-0846(01)80044-5
Mohamed SA, Al-Sulaiman FA, Ibrahim NI et al (2017) A review on current status and challenges of inorganic phase change materials for thermal energy storage systems. Renew Sustain Energy Rev 70:1072–1089. https://doi.org/10.1016/j.rser.2016.12.012
Mohammad MB, Brooks GA, Rhamdhani MA (2017) Thermal analysis of molten ternary lithium-sodium-potassium nitrates. Renew Energy 104:76–87. https://doi.org/10.1016/j.renene.2016.12.015
Muñoz-Sánchez B, Nieto-Maestre J, Iparraguirre-Torres I et al (2018) Molten salt-based nanofluids as efficient heat transfer and storage materials at high temperatures. An overview of the literature. Renew Sustain Energy Rev 82:3924–3945. https://doi.org/10.1016/j.rser.2017.10.080
Myers PD, Alam TE, Kamal R et al (2016) Nitrate salts doped with CuO nanoparticles for thermal energy storage with improved heat transfer. Appl Energy 165:225–233. https://doi.org/10.1016/j.apenergy.2015.11.045
Pfleger N, Bauer T, Martin C et al (2015) Thermal energy storage—overview and specific insight into nitrate salts for sensible and latent heat storage. Beilstein J Nanotechnol 6:1487–1497. https://doi.org/10.3762/bjnano.6.154
Salunkhe PB, D JK (2017) Investigations on latent heat storage materials for solar water and space heating applications. J Energy Storage 12:243–260. https://doi.org/10.1016/j.est.2017.05.008
Shao J, Darkwa J, Kokogiannakis G (2015) Review of phase change emulsions (PCMEs) and their applications in HVAC systems. Energy Build 94:200–217. https://doi.org/10.1016/j.enbuild.2015.03.003
Wei G, Wang G, Xu C et al (2018) Selection principles and thermophysical properties of high temperature phase change materials for thermal energy storage: a review. Renew Sustain Energy Rev 81:1771–1786. https://doi.org/10.1016/j.rser.2017.05.271
Wei X, Yin Y, Qin B et al (2017) Thermal conductivity improvement of liquid nitrate and carbonate salts doped with MgO particles. Energy Procedia 142:407–412. https://doi.org/10.1016/j.egypro.2017.12.064
Wen R, Huang Z, Huang Y et al (2016) Synthesis and characterization of lauric acid/expanded vermiculite as form-stabilized thermal energy storage materials. Energy Build 116:677–683. https://doi.org/10.1016/j.enbuild.2016.01.023
Wu Y, Li J, Wang M et al (2018) Solar salt doped by MWCNTs as a promising high thermal conductivity material for CSP. RSC Adv 8:19251–19260. https://doi.org/10.1039/C8RA03019G
Xie Q, Zhu Q, Li Y (2016) Thermal storage properties of molten nitrate salt-based nanofluids with graphene nanoplatelets. Nanoscale Res Lett 11:1–7. https://doi.org/10.1186/s11671-016-1519-1
Yang DJ, Zhang Q, Chen G et al (2002) Thermal conductivity of multiwalled carbon nanotubes. Phys Rev B 66:165440. https://doi.org/10.1103/PhysRevB.66.165440
Yang L, Xu X (2017) A renovated Hamilton–Crosser model for the effective thermal conductivity of CNTs nanofluids. Int Commun Heat Mass Transf 81:42–50. https://doi.org/10.1016/J.ICHEATMASSTRANSFER.2016.12.010
Zhang P, Ma F, Xiao X (2016) Thermal energy storage and retrieval characteristics of a molten-salt latent heat thermal energy storage system. Appl Energy 173:255–271. https://doi.org/10.1016/j.apenergy.2016.04.012
Acknowledgements
This work was supported by (i) Grant No: EMR/2016/007091, Science & Engineering Research Board, DST, India (ii) Grant No: DST/TM/SERI/FR/152(G), DST, India and (iii) PG Teaching Grants No: SR/NM/PG-16/2007, SR/NM/PG-04/2015 of Nano Mission Council, Department of Science & Technology (DST), India.
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Saranprabhu, M.K., Rajan, K.S. Enhancement of solid-phase thermal conductivity and specific heat of solar salt through addition of MWCNT: new observations and implications for thermal energy storage. Appl Nanosci 9, 2117–2126 (2019). https://doi.org/10.1007/s13204-019-01107-0
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DOI: https://doi.org/10.1007/s13204-019-01107-0