Chromogenic glass speaks to what is chromogenic glass and why use chromogenic glass.
It is glass which can change its optical properties. Thermochromic glass becomes darker when it is warmed by the sun and photochromic glass which becomes darker when exposed to bright light. Both types are potentially valuable as passive devices to reduce cooling loads in buildings.
Chromogenic switchable glazing or “smart windows” have an important role to play in future
glazings. Chromogenic is probably one of the most exciting and complicated topics in the field of
glazing. Over the last few years there has been growing interest in this technology and is expected to continue well into the next century for a variety of products.
The function of a smart window is to control the flow of light and heat into and out of a glazing, according to occupant comfort. Applications include glazings in buildings, vehicles, aircraft, spacecraft and ships. Chromogenic glazing can also regulate lighting and heating levels for energy load management.
The smart window has a considerable energy advantage over that of a conventional bronze window. Energy modeling of electrochromic windows has shown that electrochromic windows can provide significant energy performance over that of conventional double glazed windows. The energy performance of a range of switchable windows is being studied at this time.
There are various physical optical techniques that can be used for chromogenic glazing. The basic property of a chromogenic material is that it exhibits a large change in optical properties upon a change in either electrical field, charge, light intensity, spectral composition, or temperature. The change in optical properties can be in the form of absorptance, reflectance or scattering.
This change can be either totally or partly over the visible and solar spectrum. The two major categories are nonelectrically activated and electrically activated types. The non-electrically activated types include photochrornics, and thermochromics and thermotropics. The most common of the electrically activated types are phase dispersed liquid crystals (PDLC), dispersed particle system (DPS) and electrochromics.