Aluminium Nitride Doping for Solar Mirrors Self-Cleaning Coatings

Anna Castaldo,Giuseppe Vitiello,Emilia Gambale

doi:10.3390/en14206668

Abstract

Soiling severely reduces solar mirror performance, requiring dispendious water consumption for cleaning operations and causing an increase in the levelized cost of energy (LCOE). An emerging technology for facing this problem consists of developing transparent self-cleaning coatings, able to be washed with a small amount of water by virtue of the modulation of surficial wetting properties. Nevertheless, the beneficial effects of coatings decrease in the first year, and coated mirrors show even higher soiling than non-coated ones. Moreover, it is important that coating production processes are economically convenient, consistent with the intended reduction of overall costs. The aim of this work is the research and development of a cheap and scalable solution, compatible with mirror fabrication steps and, in such a sense, economically advantageous. It involves the substitution of the alumina last layer of solar mirrors with more hydrophobic, potentially auxetic aluminum compounds, such as nitrides. In particular, 2D inorganic aluminum nitride thin films doped with metals (such as aluminum and silver) and non-metals have been fabricated by means of reactive sputtering deposition and characterized for the purpose of studying their self-cleaning behavior, finding a trade-off between wetting properties, optical clarity, and stability.

Highlights

Concentrating solar power could become the cheapest form of energy production in many regions of the word, with the only problem of maintaining the solar field performance [1]
The most promising is that of coating solar mirror surfaces with self-cleaning layers, which can be hydrophobic, hydrophilic, or photocatalytic thin films, whose washing requires the smallest amount of water, reducing maintenance costs [5]
In order to change solar mirrors’ wettability for the purpose of reducing water consumption and costs in cleaning operations and maintenance (O&M), experimentation on thin-film metamaterial coatings based on aluminum compounds different from oxides was conducted

Summary

Introduction

Concentrating solar power could become the cheapest form of energy production in many regions of the word, with the only problem of maintaining the solar field performance [1]. The areas of the global sunbelt, where concentrated solar power plants are typically located, suffer from high soiling due to dust accumulation, and this reduces the amount of solar energy received (and electricity produced), increasing LCOE [2]. The most promising is that of coating solar mirror surfaces with self-cleaning layers, which can be hydrophobic, hydrophilic, or photocatalytic thin films, whose washing requires the smallest amount of water, reducing maintenance costs [5]. Such a strategy, has to preserve the optical performance of mirrors and this implies the further requirement of UV-Vis-NIR high transmittance of the coatings.

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Conclusion