This is the fourth in this series of “Lessons Learned and Yet to be Learned” on topics related to glass strength.(1-3) In this paper we pick up the topic of stronger glass products from our earlier publication(2) and expand to discussing commercial technologies. Included in this discussion are a brief historical perspective of the initial technologies and update to newer technologies with the aim to obtain faster production rates that focus on lightweight glass products and a sustainable future with respect to resource conservation, reduced energy consumption and reduced CO2 emissions. Also included are glass products which focus on safety mostly and less on overall strength.

The primary objective of this study is to explore the relationship between the composition, structure, and thermal characteristics of M-Al-Si-O-N glasses, with M representing sodium (Na), magnesium (Mg), or calcium (Ca). The glasses were prepared by melting in a quartz crucible at 1650 °C and AlN precursor (powder) was utilized as a nitrogen source. The measured thermal properties studied were glass transition temperature (Tg), crystallization temperature (Tc), glass stability, viscosity, and thermal expansion coefficient (α). The findings indicate that increasing the aluminum content leads to higher glass transition, crystallization temperatures, and viscosities. In contrast, fragility values increase with the Al contents, while modifier elements and silicon content influence thermal expansion coefficient values. FTIR analysis revealed that in all glasses, the dominant IR bands are attributed to the presence of Q2 and Q3 silicate units. The effect of Al is observed as a progressive polymerization of the silicate network resulting from the glass-forming role of Al2O3. In most samples, the Q4 silicate mode was also observed, strongly related to the high Al content. Overall, the study shows that the complexity of composition-property correlations where the structural changes affect the properties of Mg/Ca-based oxynitride glasses has potential implications for their use in various technological fields.

Glass materials are an essential component in solar energy applications which comprise, e.g., photovoltaics, solar thermal collectors, greenhouses, and algae reactors, by acting as a protective and light transmitting barrier [1, 2]. Adding functionalities and optimizing the glass and coatings in an intelligent way creates opportunities to enhance the properties of the cover glass material for its use. 

Glass as a cover material for solar energy applications constitutes a significant part of the costs and a major part of the weight. However, glass is an important component for efficient light capture and protection to the environment. The R&D of cover glass for solar energy applications have so far received limited attention even though it is an important material for our future sustainable development and will likely require an increase of the flat glass production in the future. Recent research efforts have provided knowledge of which properties that needs to be optimized - balancing efficiency, service lifetime and cost. The challenges of cover glass for different solar energy applications differs somewhat but all have in common the efficient solar light capture and protection to the environment. Thus, the know-how can be used in several different industrial sectors. The fundamentals of cover glasses for solar energy applications as well as previous and on-going project concepts will be presented. This includes i) state-of-the-art of cover materials for greenhouses [2], ii) results on optimization of cover glass for photovoltaics [3, 4], iii) initial results on how to provide both anti-reflective and anti-soiling properties, iv) results on broadband antireflective coatings for solar thermal energy [5], and v) other promising concepts. At last, will some perspective of matters for further research be presented.

[1] J. Deubener, et al., Glasses for solar energy conversion systems. Journal of the European Ceramic Society, 2009. 29(7): p. 1203-1210. DOI: http://dx.doi.org/10.1016/j.jeurceramsoc.2008.08.009.

[2] M. Teitel, et al., Greenhouse and screenhouse cover materials: literature review and industry perspective. Acta Horticulturae, 2018. 1227: p. 31-44. DOI: https://doi.org/10.17660/ActaHortic.2018.1227.4.

[3] B.L. Allsopp, et al., Towards improved cover glasses for photovoltaic devices. Progress in Photovoltaics: Research and Applications, 2020. 28(11): p. 1187-1206. DOI: https://doi.org/10.1002/pip.3334.

[4] P. Sundberg, et al., Simultaneous chemical vapor deposition and thermal strengthening of glass. Thin Solid Films, 2019. 669: p. 487-493. DOI: https://doi.org/10.1016/j.tsf.2018.11.028.

[5] E. Zäll, et al., Aerosol-based deposition of broadband antireflective silica coating with closed mesoporous structure. Solar Energy Materials and Solar Cells, 2023. 250: p. 112078. DOI: https://doi.org/10.1016/j.solmat.2022.112078.

We present a functional glass coating that embed several functionalities suitable for cover glass applications in solar energy harvesting applications, including omnidirectional anti-reflection, dynamic solar control, and self-cleaning. Yttrium hydride oxide (YHO) and sulphated titania (SO4-TiO2) thin films were deposited on the nanopillar structures using magnetron sputtering methods. Nanopillar terminated glass were achieved by colloidal lithography templating methods on iron free glass, realizing nanopillar structures with dimensions /2. The resulting nanopillar structures exploit Mie scattering for wide angle light collection. The YHO and SO4-TiO2 films block UV light and YHO photo-darkens upon solar light absorption with and reverts to its transparent state in darkness in reproducible manner with colour neutral spectral characters. The results demonstrate possibilities to increase e.g. solar cell device efficiency by smart cover glass materials without adding further control and maintenance solutions.

Solar energy will be a crucial part of the sustainable, fossil free energy production of the future. A majority of this will be produced by solar collectors and photovoltaics. Important for the efficient utilization of the incident solar energy for both technologies are a cover glass with antireflective coatings giving it a high solar transmittance. In the current paper we describe the development of antireflective mesoporous silica coatings on low-iron float glass using the aerosol-based nFOG™ deposition technique. The coatings exhibit a hexagonal and closed pore structure, high smoothness, superhydrophilic properties (contact angle <5°) and consistent thicknesses of approximately 110 nm. This is in line with optimal thickness determined from simulations of the antireflective behavior. Low-iron float glass coated on both sides show a highly reproducible solar weighted transmittance of 95% in the wavelength range 300–2500 nm and an antireflective effect increasing with incident angle. The smoothness, closed pores and low contact angle indicate a high cleanability, which in combination with the high transmittance render a competitive broadband antireflective coating well adapted for solar glass applications.

Solar energy will be a crucial part of the sustainable, fossil free energy production of the future. Amajority of this will be produced by solar collectors and photovoltaics. Important for the efficientutilization of the incident solar energy for both technologies are a cover glass with antireflectivecoatings giving it a high solar transmittance. In the current paper we describe the development ofantireflective mesoporous silica coatings on low-iron float glass using the aerosol-based nFOGTMdeposition technique. The coatings exhibit a hexagonal and closed pore structure, a high smoothness,and consistent thicknesses of approximately 110 nm. This is in line with optimal thicknessesdetermined from simulations of the antireflective behavior. Low-iron float glass coated on both sidesshow a highly reproducible solar weighted transmittance of 95 % in the wavelength range 300-2500nm and an antireflective effect increasing with incident angle. The smoothness and closed poresassociated with high cleanability, as well as high transmittance makes it a competitive broadbandantireflective coating well adapted for solar glass applications.

I ett nyligen avslutat forskningsprojekt har Absolicon Solar Collector tillsammans med RISE Research Institutes of Sweden och Umeå universitet utvecklat en ny toppmodern antireflektiv beläggning som kan göra Absolicons solfångare än mer effektiva. Nu siktar man på ett nytt projekt för att skala upp metoden.

The use of antireflective coatings to increase the transmittance of the cover glass is a central aspect of achieving high efficiencies for solar collectors and photovoltaics alike. Considering an expected lifetime of 20–30 years for solar energy installations, the durability of the antireflective surfaces is essential. Here, a novel antireflective SiO2 coating with a hexagonally ordered closed pore structure, produced with an aerosol-based sol-gel method is benchmarked against two commercial coatings; produced with acid etching and sol-gel roll coating. The optical and mechanical properties together with contact angle characteristics were evaluated before and after various durability tests, including climate chamber tests, outdoor exposure, and abrasion. Compared to the commercial antireflective coatings with open pore structures, the novel coating performed in parity, or better, in all tests. Based on the results of humidity freeze and industrial climate chamber tests, it appears that the coating with closed pore structure has a better ability to prevent water adsorption. Additionally, the closed pore structure of the coating seems to minimize the accumulation of dirt and deposits. The abrasion and cleanability test further confirm the advantages of a closed pore structure, showcasing the coating's mechanical durability. While the coatings exhibit similar hardness and reduced elastic modulus, the closed pore coating proves to be even harder after undergoing the industrial climate chamber test, but also slightly more brittle, as indicated by the probability of crack initiation. In summary the closed pore structure is well suited for tempered and arid climates, making it a truly competitive alternative to existing antireflective coatings.