Smart Window
Windows not only let light in to cut down an electricity use for lighting, but the light coming through the window also provides heat. However, windows are not something people typically associate with being a cutting edge1 technology. Researchers are now working on new technologies that enable a window to quickly change from clear to dark and anywhere in between with a flip of a switch2.
Yet, windows are the weak link in a building when it comes to energy and temperature control. In the winter, cold air leaks in. When its hot and sunny, sunlight streams in. All of this sunlight carries lots of heat and energy. And all of this extra heat forces people to turn on their air conditioners. Producing blasts of cold air, which can feel so refreshing, actually suck up enormous amounts of electricity in buildings around the world.
Electrochromic windows use electricity to change color. For example, a sheet of glass coated with thin layers of chemical compound such as tungsten oxide works a bit like a battery. Tungsten oxide is clear when an electric charge is applied and dark when the charge is removed, that is, when the amount of voltage is decreased, the window darkens until its completely dark after all electricity is taken away. So applying a voltage determines whether the window looks clear or dark.
词汇：
air conditioner 空调jolt n. v. 震摇，颠簸，晃动
glaze v. 装玻璃，上釉voltage n. 电压
注释：
2. anywhere in between with a flip of a switch：就在开或关的一霎那。
练习：
A) Windows can change from clear to dark to save energy.
C) Windows help to save energy by providing heat.
2. When are windows the weak link in a building?
B) In the hot summer.
D) Both A and B.
A) Windows that are coated.
C) Windows the color of which can be changed.
4. To make electrochromic windows change color, what is applied to the window glass?
B) Tungsten oxide.
D) A voltage.