Photographs of a 100cm2 electrochromic window in the clear and tinted states. The electrochromic films of the window were prepared by photodeposition method.A team from the University of British Columbia have devised a new approach to making self-tinting “smart” windows that is both straightforward and cheap compared to current production methods. The development could give a boost to the adoption of such energy-saving technology, as smart windows help conserve the energy from buildings by dynamically controlling heat and light from the sun to fit its requirements.
Standard windows are known to lose a third of all energy used to heat, ventilate and air condition a building, so technology that works to reduce such energy waste in an economical way is to be welcomed. Although smart windows until now have been much more expensive to manufacture, this technique allows them to be made without the need for high temperatures or sophisticated vacuum equipment, potentially bringing the cost right down.
The researchers specialize in producing functional films and coatings, usually made of a very thin layer of metals and metal oxides, for energy conversion and storage technologies. As detailed in the journal Chem [Cheng et al. Chem (2018) DOI: 10.1016/j.chempr.2017.12.030], their approach to producing glass materials that can change color in response to electricity builds on a technique involving the deposit of a liquid solution containing a metal ion onto glass, before using ultraviolet light to change it into a film that coats the glass. This film is transparent but becomes blue on electricity passing through it, producing the active component needed.
“Our goal is to use our low-cost methods to make full size electrochromic windows that can perform at least as well as the expensive materials currently used in industry”Curtis Berlinguette
They had previously shown a method for accessing active metal oxide layers using solution-based techniques that can be scaled up, and have built on this with electrochromic windows due to the potential energy savings involved. As project leader Wei Cheng said, “Our technique creates a uniform dynamic coating without the need for special instrumentation. Another advantage of our method is that it is compatible with many different metals and is scalable.”
The approach is applicable to a number of different materials that are not usually accessible with low temperature techniques, which means they can test other materials or combinations of materials, and could lead to better electrochromic properties than those currently on offer. As researcher Curtis Berlinguette points out, “Our goal is to use our low-cost methods to make full size electrochromic windows that can perform at least as well as the expensive materials currently used in industry”.
They now hope to fine-tune the dynamic properties of the materials to help improve performance, and demonstrate that these smart windows will last as long as standard commercial windows by improving their stability so they can continue to change color for many years, as well as to introduce more neutral tinting shades.