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Achieving optically selective coatings of silica fixated carbon nanotubes for solar energy applications
Umeå University, Faculty of Science and Technology, Department of Physics. Absolicon Solar Collector AB, Härnösand, Sweden.
Umeå University, Faculty of Science and Technology, Department of Physics.ORCID iD: 0009-0002-9248-5748
Umeå University, Faculty of Science and Technology, Department of Physics. Absolicon Solar Collector AB, Härnösand, Sweden.
Umeå University, Faculty of Science and Technology, Department of Physics.
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2024 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 278, article id 113202Article in journal (Refereed) Published
Abstract [en]

Solar collectors have the potential for significant climate change mitigation by substituting heat produced with fossil fuels. To achieve this, collectors with highly efficient solar absorbers are essential. Carbon nanotubes are highly absorbing, sustainable, cheap, and thermally stable, making them a promising material for solar absorbers. However, achieving a high solar absorptance and low thermal emittance (solar selectivity), while maintaining good thermal stability and scalability is challenging. Here, we present a selective coating based on multi-walled carbon nanotubes and silica (SiO2). A water-based dispersion enabled by carboxyl functionalization of the carbon nanotubes (CNTF) is spray coated on a stainless steel (SS) substrate and fixated with sol-gel dip coated silica. The SS/CNTF/SiO2 surface exhibits an optical selectivity dependent on CNTF area load and with 0.83 gCNT m−2 a solar absorptance and thermal emittance of 0.94 and 0.40, respectively, is achieved. The coating also demonstrates excellent thermal stability, with an estimated lifetime of >25 years at working temperatures ≤222°C. All together, we show that by using scalable and cheap technology, concurrent with sustainable materials and a simple structural design, we can manufacture a coating that exhibits properties suitable for low-to-mid-temperature applications. Our study highlights the potential of carbon-based solar absorbers.

Place, publisher, year, edition, pages
Elsevier, 2024. Vol. 278, article id 113202
Keywords [en]
Carbon nanotubes, Solar absorber, Solar energy, Solar selective coating, Solar thermal, Spray coating
National Category
Energy Engineering Physical Sciences
Identifiers
URN: urn:nbn:se:umu:diva-230981DOI: 10.1016/j.solmat.2024.113202ISI: 001339004300001Scopus ID: 2-s2.0-85205931081OAI: oai:DiVA.org:umu-230981DiVA, id: diva2:1908602
Funder
Knut and Alice Wallenberg FoundationAvailable from: 2024-10-28 Created: 2024-10-28 Last updated: 2025-04-25Bibliographically approved
In thesis
1. Heating a sustainable future: optical coatings for solar collectors
Open this publication in new window or tab >>Heating a sustainable future: optical coatings for solar collectors
2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Uppvärmning av en hållbar framtid : optiska beläggningar för solfångare
Abstract [en]

The green transition is the great undertaking of our time, and it will require significant ingenuity and change in all areas of society. Most urgently, perhaps, regarding energy, where the demand for transport, electricity and heat must be met by renewables instead of fossil fuels. Solar thermal is one alternative with the potential to contribute substantially to sustainable heat production. To realize this potential, the availability of competitive, sustainable and cost effective optical coatings for solar collectors is a prerequisite. The coatings used today are primarily produced with expensive vacuum-based deposition techniques, transferring a hampering cost to the collectors, which impede the deployment of solar thermal as an energy source. Herein, we show that by leveraging scalable deposition techniques, with elaborate material choices and innovative nanoscale designs, it is possible to produce sustainable coatings that are highly competitive with regards to cost and performance.Using a scalable aerosol-based deposition technique, an antireflective mesoporous silica coating, commonly implemented in advanced solar technologies, is produced with an ordered hexagonal pore structure. The attention to optical thickness and pore structure facilitates a superior performance and an increased durability, making it especially suitable for arid climates. Moreover, we present several methods to achieve solar selectivity for the receiver. We leverage the large potential window of a deep eutectic solvent to facilitate electrodeposition of a texture-based cobalt-chromium coating, making an otherwise unsustainable technique viable today. High selectivity is also achieved by manipulating interference effects in coatings produced through precise control of thermal annealing of steel and ultrasonic spray coating of carbon nanotube composites. Such optical effects are only achieved for selective coatings deposited with more advanced and expensive techniques.Science is an iterative process of small incremental advances, often seemingly insignificant in the moment, which over time accumulate to surprisingly quick change. Here we present examples of sustainable, scalable, durable and cost competitive antireflective and solar selective coatings, thereby hopefully contributing to an accelerated implementation of solar thermal technologies.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2025. p. 64
Keywords
Solar thermal collectors, optical coatings, solar selective coatings, antireflective coatings
National Category
Nanotechnology for Energy Applications
Research subject
Physics; Materials Science; nanomaterials
Identifiers
urn:nbn:se:umu:diva-238174 (URN)978-91-8070-654-4 (ISBN)978-91-8070-655-1 (ISBN)
Public defence
2025-05-23, KB301-Lilla hörsalen, Linnaeus väg 6, 907 36 Umeå, Umeå, 09:00 (English)
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Supervisors
Note

In thesis listed paper "Solar selective carbon nanotube composite coatings on optically tunable undercoating" is in the printed thesis published with title "Towards Solar Selective Carbon Nanotube Composites on Optically Tunable Undercoatings". 

Available from: 2025-04-30 Created: 2025-04-25 Last updated: 2025-04-28Bibliographically approved

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Zäll, ErikSegervald, JonasMahmoodi, HodaPerivoliotis, DimitriosEdman, LudvigWågberg, Thomas

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