Flat glass is an integral component of many solar energy technologies, including solar thermal collectors, photovoltaic modules and Concentrated Solar Power plants. Although the solar energy market for flat glass is relatively small in volume compared to the building and automotive markets, it is fast expending due to the increasing demand for renewable energy. It is also a market of high added-value glass products and a strong driver for innovations.

Glass in solar energy applications plays an active role in ensuring efficient and effective solar energy conversion. Glass is designed to optimise solar energy conversion while providing long term protection against external conditions. Extra clear glass, with low iron oxide content is typically used in solar applications. Either float or patterned, low iron glass may be coated with an anti-reflecting coating to further increase performance. Glass may also be toughened to increase strength and durability. Coatings on glass can also play a functional role in solar energy conversion. For example, transparent conductive coating can be used as an electrical contact in some photovoltaic technologies allowing the light through to the photovoltaic material while conducting the general electricity out of the modules.

Glass in Solar Thermal Application

Solar thermal collectors are intended to collect heat - as opposed to photovoltaic panels which convert sunlight into electrical power. The collected solar heat can be used to supply hot water or heat exchangers, for domestic or industrial applications.

There are various kinds of solar thermal collectors but most require a flat glass cover, or glazing, which serves not only to protect the panel while letting the sunlight through but also to prevent cooling of the panel from exposure to cold air.

Glass in Photovoltaic Applications

Photovoltaic technologies are used to convert solar energy directly into electricity. There are many different technologies available to suit various requirements, from domestic systems to utility scale. Photovoltaic panels come in various shapes and colors offering flexibility for design integration and building integrated applications (BIPV).

The most common photovoltaic technology is based on crystalline silicon solar cells. In this application glass acts as a protective outer layer, while transmitting the solar light to the photovoltaic cells interconnected underneath.

Other photovoltaic technologies include thin film photovoltaics where solar cells are deposited as a sequence of thin films on glass. In these technologies, transparent conductive coated glass can be used as the front glass upon which the films are grown. The conductive coating not only allows light through to the photoactive films, but also conducts the generated electricity out of the modules.

Glass and mirrors in Concentrated Solar Power Systems

Concentrated Solar Power (CSP) systems are used to produce electricity from the sun at utility scale. These systems are mainly used in regions with high levels of solar irradiance. CSP systems use lenses or mirrors to concentrate a large amount of sunlight onto a central receiver, thereby producing electricity either by concentrating the sunlight onto a high performance photovoltaic cell or by heating a transfer fluid to supply heat to a conventional thermodynamic power plant. For CSP systems, extra clear glass and mirrored glass are used to redirect accurately the maximum amounts of light towards the focal point.