Abstract
The anti-soiling (AS) performance of highly reflective, superhydrophilic (SPH, 0° water contact angle) coated mirrors was characterized and compared with that of superhydrophobic (SP, >165° water contact angle) coated mirrors. A simple one-step nanotextured silica nanoparticle coating on a mirror exhibited SPH properties associated with hydrophilic rough surfaces. Another mirror surface post-functionalized with low-surface-energy ligand molecules displayed SP behavior. Both coated mirrors, with no solar reflectance loss, demonstrated excellent AS performance because the engineered surface roughness reduced the adhesive force of dust particles. The daily degradation in solar reflectance induced by dust accumulation under outdoor field testing demonstrated that the SPH- and SP-coated mirrors, compared with an uncoated mirror, maintained higher solar reflectance, which was associated with the designed self-cleaning behavior and natural cleaning. However, over the long term, dust-moisture cementation - evidenced by organic hard water stains on the mirror - initiated unrecoverable reflectance loss on the SP-coated mirror after 3 months, whereas the SPH-coated mirror maintained higher reflectance for 7.5 months. Considering fabrication costs and maintenance, SPH-coated nanotextured mirrors offer potential benefits for application in solar energy harvesting.
Original language | English |
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Pages (from-to) | 1249-1260 |
Number of pages | 12 |
Journal | Nanoscale Advances |
Volume | 1 |
Issue number | 3 |
DOIs | |
State | Published - 2019 |
Funding
† Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). ‡ Electronic supplementary information (ESI) available. See DOI: 10.1039/c8na00349a This research was conducted at Oak Ridge National Laboratory (ORNL), which is managed by UT Battelle, LLC, for the US Department of Energy (DOE) under contract DE-AC05-00OR22725. The work was sponsored by the Solar Energy Technologies Office within the DOE Office of Energy Efficiency and Renewable Energy. Some of the materials characterization (including SEM and AFM humidity measurement) was conducted at the Center for Nanophase Materials Sciences, which is sponsored by the ORNL Scientic User Facilities Division and the DOE Office of Basic Research Sciences.