Solar Thermal Energy

High-transmission glass for solar engineering based on structured, inorganic anti-reflection coatings

The project's aim is to develop and implement the technology for a coating method for production of anti-reflection coatings on float glass. These inorganic coatings reduce reflection loss on glass surfaces and can thus increase the efficiency of solar thermal and photovoltaic systems.

Summary

In many optical applications, the reflection of light on glass surfaces has a detrimental effect on the transmission of radiation energy. At a thickness of 4 mm, conventional flat glass incurs roughly 8% reflection loss, for example. In special cases, this is remedied through anti-reflection coatings based on interference effects – a solution that is heavily dependent on wavelengths and angles and is also expensive.

An alternative is presented by the sol-gel method used to produce fine, porous SiO2 surface structures with the help of viscous substrate material. The produced anti-reflection coatings facilitate an increase in high-energy radiation transmission and an extension of the absorbed wavelength spectrum while being easy and cheap to produce. The method is thus particularly suitable for optimising the performance of solar modules.

The project partners' task is to develop a high-performance sol and to transfer the findings on applying abrasion-proof anti-reflection coatings to high-quality float glass from the laboratory scale to industrial production.

Results:

  • By combining alcoholic and aqueous sol, the resultant hybrid sol allowed development of a system that largely meets the criteria for a marketable product (abrasion-proof, weather-resistant, solar transmission > 95%). Service life has yet to be improved.
  • Industrial-scale synthesis of the sols was successfully implemented at a pilot plant.
  • While the known porous coatings sinter at 600°C, sinter effects do not occur on the new sols until temperatures of 900°C or 1,100°C are reached.
  • This method can thus be used to apply anti-reflection coatings to glass with only minor structuring (e.g. float glass).
  • Removal of occurring corrosion layers requires a polishing and cleaning step.

More Project Information

Project number: 0329800

Project period: 1998 - 2001

Project region: Germany (Bavaria, Hesse)

Project contact:

Frau Dr. Kursawe

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Source: German National Library of Science and Technology Hannover (TIB)