Energy flow control of nanofluid-based direct absorption solar collectors with functional optical coatings for efficient solar harvesting

Abstract

The nanofluid-based direct absorption solar collector (NDASC) ensures that solar radiation passing through the tube wall is directly absorbed by the nanofluid, reducing thermal resistance in the energy transfer process. However, further exploration is required to suppress the outward thermal losses from the nanofluid at high temperatures. Herein, this paper proposes a novel NDASC in which the outer surface of the collector tube is covered with functional coatings and a three-dimensional computational fluid dynamics model is established to study the energy flow distributions on the collector within the temperature range of 400–600 K. When the nanofluid’s absorption coefficient reaches 80 m⁻¹, the NDASC shows the optimal thermal performance, and the NDASC with local Sn-In₂O₃ coating achieves a 7.8% improvement in thermal efficiency at 400 K compared to the original NDASC. Furthermore, hybrid coatings with SnIn₂O₃/WTi-Al₂O₃ are explored, and the optimal coverage angles are determined. The NDASC with such coatings shows a 10.22%–17.9% increase in thermal efficiency compared to the original NDASC and a 7.6%–19.5% increase compared to the traditional surface-type solar collectors, demonstrating the effectiveness of the proposed energy flow control strategy for DASCs.

Keywords

direct absorption solar collector / nanofluid / functional optical coatings / energy flow control

References

[1] OmeizaL A, AbidM, SubramanianY, et al.. Limitations and challenges of heat transfer enhancement techniques in solar thermal collectors: A review [J]. Journal of Central South University, 2023, 30(11): 3538-3574.

[2] SheikholeslamiM, KhaliliZ. Enhancing photovoltaic solar panel performance with integration of PCM-based spectral filter and self-cleaning coating [J]. Journal of Building Engineering, 2024, 94110019.

[3] TarahomiM, RashidiS, HormoziF, et al.. Performance improvement in stepped solar still modified by sponge layer [J]. Journal of Central South University, 2024, 31(6): 1973-1982.

[4] WangX-y, ZhangC, ZhangC-c, et al.. A comprehensive updated research progress of key technologies of linear concentrated solar power from material to application [J]. Solar Energy Materials and Solar Cells, 2025, 285113492.

[5] SheikholeslamiM, KhaliliZ. Simulation of a photovoltaic panel with a novel cooling duct using ternary nanofluid and integrated with a thermoelectric generator [J]. Journal of the Taiwan Institute of Chemical Engineers, 2025, 170105982.

[6] Shokrgozar AbbasiA, KhanA N. Improving performance of flat plate solar collector using nanofluid water/zinc oxide [J]. Journal of Central South University, 2021, 28(11): 3391-3403.

[7] BiglarianH, SharfabadiM M, AlizadehM, et al.. Performance investigation of solar thermal collector with auxiliary heater for space heating [J]. Journal of Central South University, 2021, 28(11): 3466-3476.

[8] FarhanaK, MahamudeA S F, KadirgamaK. Numerical study of solar tray with noble Mxene nanofluids [J]. Journal of Central South University, 2023, 30(11): 3656-3669.

[9] AraiN, ItayaY, HasataniM. Development of a “volume heat-trap” type solar collector using a fine-particle semitransparent liquid suspension (FPSS) as a heat vehicle and heat storage medium Unsteady, one-dimensional heat transfer in a horizontal FPSS layer heated by thermal radiation [J]. Solar Energy, 1984, 32(1): 49-56.

[10] MinardiJ E, ChuangH N. Performance of a “black” liquid flat-plate solar collector [J]. Solar Energy, 1975, 17(3): 179-183.

[11] MohammadiM. Environmental influences on thermal performance of direct absorption solar collector filled with nanofluid [J]. Solar Energy Materials and Solar Cells, 2025, 282113409.

[12] XingL-z, LiX-k, WangR-p, et al.. Fe₃O₄/Au@SiO₂ nanocomposites with recyclable and wide spectral photo-thermal conversion for a direct absorption solar collector [J]. Renewable Energy, 2024, 235121269.

[13] KhullarV, TyagiH, PhelanP E, et al.. Solar energy harvesting using nanofluids-based concentrating solar collector [J]. Journal of Nanotechnology in Engineering and Medicine, 2012, 33031003.

[14] OtanicarT P, PhelanP E, PrasherR S, et al.. Nanofluid-based direct absorption solar collector [J]. Journal of Renewable and Sustainable Energy, 2010, 23033102.

[15] Bretado De Los RiosM S, Rivera-SolorioC I, García-CuéllarA J. Thermal performance of a parabolic trough linear collector using Al₂O₃/H₂O nanofluids [J]. Renewable Energy, 2018, 122: 665-673.

[16] MotamediM, JiaG-b, YaoY, et al.. Nanopatterned indium tin oxide as a selective coating for solar thermal applications [J]. Renewable Energy, 2023, 210: 386-396.

[17] SinghN, KhullarV. Efficient volumetric absorption solar thermal platforms employing thermally stable - solar selective nanofluids engineered from used engine oil [J]. Scientific Reports, 2019, 9110541.

[18] SinghN, KhullarV. On-Sun testing of volumetric absorption based concentrating solar collector employing carbon soot nanoparticles laden fluid [J]. Sustainable Energy Technologies and Assessments, 2020, 42100868.

[19] LiQ-y, ZhengC, MesgariS, et al.. Experimental and numerical investigation of volumetric versus surface solar absorbers for a concentrated solar thermal collector [J]. Solar Energy, 2016, 136: 349-364.

[20] Ait-SadiH, BekhitiD, HemmoucheL, et al.. Advanced coatings and structures for enhancing concentrating solar power efficiency [J]. Renewable and Sustainable Energy Reviews, 2025, 211115270.

[21] KhullarV, TyagiH, OtanicarT P, et al.. Solar selective volumetric receivers for harnessing solar thermal energy [J]. Journal of Heat Transfer, 2018, 1406062702.

[22] SinghN, KhullarV. Experimental and theoretical investigation into effectiveness of ZnO based transparent heat mirror covers in mitigating thermal losses in volumetric absorption based solar thermal systems [J]. Solar Energy, 2023, 253: 439-452.

[23] CyulinyanaM C, FerrerP. Heat efficiency of a solar trough receiver with a hot mirror compared to a selective coating [J]. South African Journal of Science, 2011, 107(11/12): 1-7.

[24] D’AlessandroC, De MaioD, MustoM, et al.. Performance analysis of evacuated solar thermal panels with an infrared mirror [J]. Applied Energy, 2021, 288116603.

[25] QinC-y, KimJ B, LeeB J. Performance analysis of a direct-absorption parabolic-trough solar collector using plasmonic nanofluids [J]. Renewable Energy, 2019, 143: 24-33.

[26] ChandraY P, SinghA, MohapatraS K, et al.. Numerical optimization and convective thermal loss analysis of improved solar parabolic trough collector receiver system with one sided thermal insulation [J]. Solar Energy, 2017, 148: 36-48.

[27] BellosE, TzivanidisC. Investigation of a star flow insert in a parabolic trough solar collector [J]. Applied Energy, 2018, 224: 86-102.

[28] BellosE, TzivanidisC, AntonopoulosK A, et al.. Thermal enhancement of solar parabolic trough collectors by using nanofluids and converging-diverging absorber tube [J]. Renewable Energy, 2016, 94: 213-222.

[29] SongX-w, DongG-b, GaoF-y, et al.. A numerical study of parabolic trough receiver with nonuniform heat flux and helical screw-tape inserts [J]. Energy, 2014, 77: 771-782.

[30] HeY-l, XiaoJ, ChengZ-d, et al.. A MCRT and FVM coupled simulation method for energy conversion process in parabolic trough solar collector [J]. Renewable Energy, 2011, 36(3): 976-985.

[31] ZouB, DongJ-k, YaoY, et al.. A detailed study on the optical performance of parabolic trough solar collectors with Monte Carlo Ray Tracing method based on theoretical analysis [J]. Solar Energy, 2017, 147: 189-201.

[32] LeeR, KimJ B, QinC-y, et al.. Synthesis of Therminol-based plasmonic nanofluids with core/shell nanoparticles and characterization of their absorption/scattering coefficients [J]. Solar Energy Materials and Solar Cells, 2020, 209110442.

[33] WanM-h, XuB, ShiL, et al.. Self-assembled Au-CQDs nanofluids with excellent solar absorption and medium – high temperature stability for solar energy harvesting [J]. Journal of Colloid and Interface Science, 2024, 672: 765-775.

[34] WanM-h, XuB, ShiL, et al.. The dynamic stability of silicone oil-based MWCNT nanofluids under high-temperature, high-flux irradiation, and shear-flow conditions [J]. Powder Technology, 2023, 424118508.

[35] WangX-y, GaoJ-h, HuH-b, et al.. High-temperature tolerance in WTi-Al₂O₃ cermet-based solar selective absorbing coatings with low thermal emissivity [J]. Nano Energy, 2017, 37: 232-241.

RIGHTS & PERMISSIONS

Central South University