Researchers have designed a new type of hybrid smart window that combines different approaches to effectively manage both heat and light control.
Smart windows are widely seen as an important part of the journey towards energy efficiency and carbon neutrality.
As cities continue to expand, buildings account for around 30% to 40% of global energy demand – more than either the energy-hungry transport or industrial sectors.
Much of this energy goes on heating, cooling and ventilation systems and windows present a significant problem.
They are generally required to make buildings comfortable for human use but allow heat to escape the building in winter and enter in summer, leading to increased usage of heating and air conditioning systems.
Smart windows help to manage these exchanges by altering their properties depending on the conditions and requirements.
Typically, this involves electrochromic (EC) processes, which respond to the application of electricity to trigger molecular changes.
These changes are increasingly effective at managing either heat or light, but current solutions are limited at managing visible light and heat via infrared radiation at the same time.
Hybrid device uses a combination of materials and approaches
The new hybrid approach, detailed in the Journal of Photonics for Energy, involves combining liquid crystals (LCs) and nanoporous microparticles (NMPs).
These two materials in combination allow smart windows to control visible light and infrared radiation equally effectively.
A small concentration of the NMPs was added to nematic LCs.
The result is a thin device that is able to rapidly change its transparency to visible light and infrared radiation.
Another enhancement involves a surface coating of vanadium dioxide (VO2) metamaterial – a synthetic structure with properties that are not possible to achieve conventionally with the constituent materials.
An ultrashort pulsed laser is used to form the VO2 film, helping the smart window to adjust its transparency in response to either temperature or electric voltage.
The VO2 surface aligns the LCs in a pattern that improves their functionality and also improves the window’s ability to block infrared radiation, helping to keep heat in during the winter and out during the summer.
The addition of the NMPs improves the response speed and reduces the amount of material needed, helping to make the smart window a thin, high-speed and energy-efficient solution.
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