NREL close to unveiling cost-effective smart windows

Sara Ver-Bruggen - 11 Apr 2011

Researchers at the US government lab make progress on solution-based processing techniques that can enable windows and glazing to conserve energy in buildings.

While glazing able to tint and lighten dynamically could help save energy use in buildings, commercial availability of such smart window technology is limited.

This could be set to change as researchers at the US National Renewable Energy Laboratory (NREL) are proving the feasibility of producing smart windows cost-effectively.

Electrochromic films or coatings for smart window applications can be darkened or lightened electronically with small voltages of electricity, to enable a building through its windows and glazing to control daylight, solar heat gain and also minimise heat loss from the building interior out through the glass.

Typically electrochromic materials based on metal oxide materials in multilayer devices are processed by sputtering, a high-temperature process done in a vacuum chamber that makes production of electrochromic glass expensive.

Buildings

The NREL researchers have investigated more cost-effective production options. One is a flexible film that could have promising potential in the retrofit building market and the other is a process for fabricating the electrochromic layer within float glass production, a process widely used in the manufacture of glass for the building and automotive markets.

Several solution-based processing methods can be used to fabricate electrochromic layers. These include chemical baths, sol-gels and spray coating. The NREL research team is close to finalising details on its progress in developing alternative methods for more cost-effective production of electrochromic devices over large-area glass substrates.

According to NREL smart windows exploiting electrochromics could save over 4% of annual energy use in the US and has estimated that electrochromic window technology will not be cost-effective for residential applications, until a price point of $20/ft² is achieved. Current EC window costs are at $50-100/ft²
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