Electrochromic glass – which instantly glazes or shades at the flick of an electrical switch – has proved popular in a range of applications where the control of light and heat is important. But the physical nature of the glass and the costs involved limit the opportunities open to this technology. An EU-funded project has applied these 'smart glass' principles to a flexible film which opens up a whole new world of green, low-cost and commercially viable possibilities.
‘Electrochromic’ (EC) glass is part of a new generation of technologies called switchable glazing or 'smart' glass. Essentially, the term refers to glass which changes light transmittance when voltage is applied. Running a small DC current through the glass causes a reaction to occur in electrochromic and ion-storage layers which leads to a reversible colour change, switching from transparent to tinted and back again.
The process allows for varying levels of light penetration, providing a choice of shades rather than clear and blacked-out. Electrochromic glass does not require a constant stream of electricity. Once the initial tint has been achieved, no more power is needed.
Today, the technology is used predominately to control the amount of light and heat transmission in buildings and can be applied to reduce heating and air-conditioning costs as well as increasing comfort by reducing glare.
The technology behind electrochromic glass holds great potential for commercial applications although the production process and the weight of the actual glass can limit its application. With this in mind, the EU-funded Innoshade project set out to produce alternative, low-cost electrochromic shading technology which would be cheaper to produce and provide more opportunities for commercial applications while delivering lower energy consumption and faster response times.
The project targeted the development of products in three specific areas with commercial appeal: ophthalmic lenses, domestic appliances, and aircraft and vehicle applications.
“While upscaling EC technology has been done before, this is only true for glass windows employing expensive ‘sputter technology’ (depositing electrochromic and ion-storage layers in vacuo over large areas),” says Dr Uwe Posset, the project coordinator at the Fraunhofer ISC’s Centre for Applied Electrochemistry in Wuerzburg, Germany. “Innoshade has developed mechanically flexible, low-cost EC films that could be put on to any surface and used in applications where glass windows are not viable for weight reasons, such as in aircraft.”
The project team developed the film with additional environmental benefits and sustainable development properties in mind, such as reduced mounting space and weight, reduction of heat loss in appliances, and retrofitting.
“According to our life-cycle assessment studies, there is considerable energy-saving potential in a number of applications,” says Dr Posset. “We have seen verifiable savings of energy needed for air-conditioning in vehicles; there is no need for mechanical shades in aircraft cabins which leads to high weight savings compared to glass-based smart windows, while increasing comfort for the passengers at the same time; and we’ve recorded substantial reduction of heat loss and heat penetration in appliances.”
The resulting EC film developed by the project represents a breakthrough in smart-shading technology by overcoming common limitations of state-of-the-art electrochromic devices. The film allows for retrofitting (not possible with previous technologies); it provides lightweight, flexible and impact resistant EC films in contrast to traditional heavy, rigid and fragile EC glass elements; and the costs involved are anticipated to be reduced – €200/m2 for dimmable film compared to €1000/m2 for conventional smart-window technology. Pilot lines for the production of the films have been put in place and are ready to be used in follow-up activities.
Innoshade’s strong links with industrial partners – the project consortium includes five small and medium-sized enterprises and four multinational global players – is expected to prove invaluable when the technology moves from the laboratory to the market place in the future.
Project acronym: Innoshade
Participants: Germany (Coordinator), Czech Republic, Spain, Italy, Slovenia, The Netherlands, Portugal, Israel, Canada, France, Turkey