Award for Adherent Antireflective Coating on Borosilicate Glass for Solar Collectors

The Braunschweig Chamber of Commerce and Industry (CCI) awards a prize for the "Adherent antireflection coatings on borosilicate glass for solar collectors" project - Technology transfer prize awarded to scientists of the Technical University of Clausthal.

This year, the technology transfer prize of the CCI Braunschweig endowed with 10.000 Euro is awarded to four scientists of the Technical University of Clausthal. The prize is awarded to scientists who managed to successfully transfer scientific results to economy.

Gundula Helsch, Marta Krzyzak, Gerhard Heide & Günther H. Frischat from the "Institut für Nichtmetallische Werkstoffe, Technische Universität Clausthal" are awarded the prize for the project of the "Adherent antireflection coatings on borosilicate glass for solar collectors". The technology was transfered to the SCHOTT group, the worlds technology leader in solar thermal power plants.

A solar thermal power plant in principle works no differently than a conventional steam power plant. However, there is one important difference. No harm is done to the environment by burning coal, oil, natural gas or by splitting uranium to produce steam. It is produced solely by the energy that comes from the sun.

SCHOTT Receivers as Key Components

Since the mid-eighties, nine solar thermal parabolic trough power plants in the Californian desert have been generating solar power with a total output of 354 megawatts (MW). The power plants produce between 14 and 80 MW of power, providing between 10,000 and 56,000 people with energy. A parabolic trough power plant consists of three key components: mirrors, receivers and turbine technology. SCHOTT has already provided high-quality special glass tubing as envelopes for the receivers at the Californian power plants. And in 2004, SCHOTT launched a new receiver of significantly higher quality, which we had developed ourselves. This new receiver, which can be industrially mass-produced, has advanced SCHOTT to the position of technological leader for this key component.

Borosilicate glass tubes as parts of parabolic-trough solar collectors reflect a total of 8 % of the incident sun light, thus reducing greatly the efficiency of solar power installations. It is about a successful development of a porous SiO2-containing antireflective coating of 110 nm thickness, which was applied by a suitable sol-gel dip coating process, increasing the light transmittance by up to 5 %. Previous antireflective coatings did not have sufficient adhesion strength and wiping resistance on borosilicate glass, so that they did not withstand the rough operation in practice. The essential component enhancing the stability of the coating turned out to be H3PO4 which is added to the dipping solution. After baking the sol-gel layers for 1 h at 500 °C both Na and P concentration peaks develop at both sides of the interface, obviously forming Na2O-phosphosilicate glasses, assuring a high long-term stability between glass and layer.

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