Thermochromic smart window using inorganic VO₂

Professor Chan Park
Department of Materials Science and Engineering 
Seoul National University, Seoul, Republic of Korea

Abstract

Windows can be a large source of energy loss in buildings. About 30% of a home's heating energy is lost through windows. In summer when cooling is needed, about 76% of sunlight that falls on standard double-pane windows enters to become heat. Considering the total energy used for heating and cooling in buildings in USA, the amount of energy loss through the windows and its effect on the energy bill can be significant. The energy-efficient design and energy-saving technologies, such as low-emissivity (low-e) glass and smart windows, of the buildings are becoming ever more important in reducing energy consumption and promoting sustainability.

There are several types of smart windows, each of which uses a different mechanism to control the amount of light and heat that passes through the window. The most common types of smart windows include electrochromic windows, suspended particle devices (SPD) windows, thermochromic windows, photochromic windows, liquid crystal windows. Each of these smart window technologies has its own advantages and disadvantages, and the most suitable technology depends on the specific application and performance requirements.

A thermochromic smart window is a type of window that changes visible light/IR transmittance in response to changes in temperature. If the transmittance can be adjusted to be high at low temperature (e.g. winter) and low at high temperature (e.g. summer), and if the temperature at which the change of transmittance takes place can be adjusted to room temperature, smaller amount of energy will be needed for heating in winter and for cooling in summer without consuming any extra energy (such is the case for certain types of smart windows). 

Different types of smart windows will be introduced and compared. Current status of the development of thermochromic smart window and issues of VO₂-based thermochromic smart window will be presented together with recent results. A brief introduction to the Department of Materials Science and Engineering, Seoul National University will be given before the presentation on smart windows.

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