Although windows can naturally heat buildings in the cold seasons, during the summer they can easily overheat a building. To help with this problem, Japanese scientists at AIST recently developed a thin film which can make transparent glass turn into mirrors. The use of such a window in buildings or automobiles could reduce the energy consumed by air conditioners by more than 30%. The scientists, Kazuki Yoshimura and Shanhu Bao developed the thin film material. Previous research works have focused on the use of thin films made of magnesium-nickel alloy that behave as switchable mirrors: these, however, all have a yellow tinge in their transparent state.
The switching mechanism in Yoshimura and Bao’s window, is created by altering the gas content between the two glass panes. By introducing a small amount of hydrogen into the atmosphere between the panes, the glass acts as a transparent window. Alternatively, adding a small amount of oxygen with no hydrogen forms a reflecting mirror.