Green Building huset

Published on September 28th, 2012 | by Amy Brown


Putting atoms to work

With rapidly growing cities commanding a larger share of the world’s energy demand, buildings need to become more energy efficient. Swedish company ChromoGenics has developed a “smart” window technology that lets in the light without burning up the electricity bills.

We like light-filled offices, particularly in the Nordic countries with their long, dark winters. But windows are also energy guzzlers, trapping heat that must be cooled with space- and energy-consuming air conditioning. As much as 30 to 40 percent of the world’s energy is used in buildings, mainly for heating, cooling, lighting, ventilation and appliances.

Finding a way to control the inflow of light and solar energy through windows, has been the pursuit of Professor Claes Göran Granqvist, a founder of ChromoGenics AB and a professor of solid state and materials physics at the renowned Ångström Laboratory at Uppsala University in Sweden, for decades. It led him in the early 1990s to electrochromic materials, which have an ability to change their optical properties when a voltage is applied across them.

“Think of a battery, with an anode, a cathode and an electrolyte,” Granqvist explains. “With the right materials, you can have anodes that change color or go from dark to transparent when you charge or discharge a battery. Our idea was to use this kind of battery across an entire window, to make it ‘switchable,’ to regulate the amount of light coming in.”

Electrochromics has become a key green technology for producing energy savings in the built environment while maintaining indoor comfort and generating financial benefits. Chromo-Genics is one of its leading proponents, named a Global Cleantech 100 company by Guardian News and Media and Cleantech Group LLC in 2009.

The company is about to move from development to production. In March, ChromoGenics raised sek 31 million after passing a milestone with new ConverLight electrochromic foil in roll-to-roll production. ChromoGenics pioneered a solution for producing electrochromic foil in rolls, which gives distinct manufacturing advantages at higher volumes, since the lightweight foil permits a more flexible business model that simplifies the specification and manufacture of smart windows.

“We built the functionality directly into a plastic form, produced in big rolls and laminated so it can be put into windows anywhere in the world,” says Granqvist.

“I think there will be other applications of this technology beyond office buildings,” he adds. “Eventually it will be applied also in domestic buildings and in cars, to control overheating and glare, and by darkening the windows, also a deterrent against theft.”

“We think of this as an enabling technology,” says Granqvist. “It makes it possible to do a lot of things that were not possible before. Our goal in the coming years is to create a well functioning and affordable technology that contributes to the need for a more energy-efficient world.”

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