With increase in global warming, use of active cooling and heating devices are continuously increasing to maintain interior temperature of built environment, greenhouses and cars. To reduce the consumption of tremendous amount of energy on cooling and heating devices we need an improved control of transparent features (i.e. windows). In this respect, smart window which is capable for reflecting solar infrared energy without interfering with the visible light would be very attractive.
Most of the technologies developed so far are to control the visible light. These technologies block visual contact to the outside world which cause negative effects on human health. An appealing method to selectively control infrared transmission is via utilizing the reflection properties of cholesteric liquid crystals. In our research, we have fabricated a smart window which is capable of reflecting different amount of solar infrared energy depending on the specific climate conditions. The reflection bandwidth can be tuned from 120 nm to 1100 nm in the infrared region without interfering with the visible solar radiations. Calculations reveal that between 8% and 45% of incident solar infrared light can be reflected with a single cell. Simulation studies predicted that more than 12% of the energy spent on heating, cooling and lighting in the built environment can be saved by using the fabricated smart window compared to standard double glazing window.
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