Electrochromic glass

Imagine buildings constructed entirely in glass. Now imagine the summer heat, then the wintry cold. Unpleasant conditions – especially at height, when windows can’t safely be opened – are a bane for designers.

This may be about to change. Designers and inventors have long strived to create glass that is reactive to environmental phenomena – particularly solar gain. The latest generation of dynamic glass could finally realise this goal.

Delivering daylight has been central to building design for centuries. Glass brings solar gain and often uncomfortable glare. An example is the shimmering glass towers of Las Vegas. They are finished with acres of glass and rely on face-sealed systems, air conditioning units and the use of tinted, reflective, permanently applied solar films in order to mitigate against the harsh desert climate.

‘Dynamic’ or ‘smart’ glazing has been in development for decades. The idea is to provide more flexibility by eliminating blinds, shades, air conditioning and solar films. Key to ‘smart’ glass is that it automatically changes its tint depending upon the surrounding natural light level. San Francisco’s W Hotel recently installed a pilot featuring new ‘smart,’ or electrochromic, window glass that responds to light intensity and which can be wirelessly controlled. Glass manufacturer Corning has picked this up for development with View, a local start-up.

View’s electrochromic glass changes its opacity under different electrical conditions, allowing for control of solar gain, glare and warmth. The technology consists of a dual-pane window containing a transparent, conductive oxide film which sandwiches an ion storage layer, an electrolyte and an electrochromic layer. A low voltage applied to the oxide pushes ions from the storage through the electrolyte to hit the electrochromic layer. This makes the electrochrome absorb or reflect light, which changes the material’s darkness, tinting the window. Reversing the voltage sends the ions back to the storage layer and the window brightens, allowing in more light.

The windows are wired to each other and connect to a central wi-fi control. The technology can be applied to panes of glass over 5m across and includes both programmable controls and a GPS system which predicts sun angles and intensity throughout the day.

The best news is the energy statistics: using the glass reduces energy consumption by 20 % and peak HVAC loads by 25 %. Primary applications will likely be exterior glazing, but the system is promising for ships, planes and cars too.