Abstract
Today's architecture uses large glazings (windows and glass facades) to obtain good indoors-outdoors contact and day-lighting. However glazings offer challenges and often lead to excessive solar energy inflow and thereby a need for energy-demanding space cooling. This paper summarizes recent work on thermochromic (TC) materials intended for energy-efficient buildings and outlines how vanadium-dioxide-based thin films and nanoparticle composites can be used in TC glazings which admit more solar energy below a comfort temperature than above this temperature, so that the cooling need is diminished, while the transmittance of visible light remains high. We also report on some very recent work on TC light scattering.
Highlights
The carbon dioxide content in the earth’s atmosphere keeps rising dramatically and has gone from ~315 ppm at the end of the 1950s to ~400 ppm in 2016; the rate of increase has almost tripled during this period of time [1]
We consider three challenges [37]: (i) the change between semiconducting and metallic-like states occurs at ~68 °C which clearly is too high for buildings, (ii) according to figure 2, Tlum is as small as ~40%, which is too low for most practical glazings
Item (ii) implies that the nanoparticle composite is efficient for lowering the transmittance of solar energy whereas the luminous properties are not strongly influenced
Summary
The carbon dioxide content in the earth’s atmosphere keeps rising dramatically and has gone from ~315 ppm at the end of the 1950s to ~400 ppm in 2016; the rate of increase has almost tripled during this period of time [1]. VO2 changes between a low-temperature (τ < τc) phase with semiconducting properties and high infrared (λ > 0.7 μm) transmittance as a thin film and a high-temperature (τ > τc) phase with metallic like properties and infrared reflectance.
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