Buildings consume up to 40% of the energy used in the U.S. and the European Union. Of the energy losses from a building, windows are a primary source. To increase energy efficiency, architects and builders have turned to low-e windows. Switchable windows based on electrochromics, however, shows significantly better energy efficiency. Like low-e, electrochromic thin films are normally deposited via DC magnetron sputtering onto glass substrates. Depending on the applications, electrochromic thin films can also be deposited via thermal or electron beam evaporation, or via alternative deposition methods such as sol-gel or electroplating. When compared with an efficient low-e window with the same daylight control system, a switchable electrochromic window shows annual peak cooling load reductions from control of solar heat gains of 19-26% and lighting energy use savings of 48-67% [LBNL "PIER" study for California]. In addition to superior energy efficiency, electrochromic windows offer a number of other advantages including eliminating the need for blinds and shades, and blocking heat and glare while still keeping the view. Despite the clear benefits, some hurdles must still be overcome before electrochromic windows can enjoy widespread applications in the architectural market, as well as the automobile market. Of these hurdles, the most important one is the high production cost. Lots of progress and advances has been made the last few years. Of particular interest are the advances in a new type of switchable electrochromic windows: switchable mirrors. Switchable mirrors change their optical properties reversibly between reflective and transparent states, instead of between absorptive and transparent states. Hydrogen-based and lithium-based switchable mirrors have both been developed. Because switchable mirrors reflect sun light and heat instead of absorbing, they are expected to be cooler, more durable, and more energy efficient. In addition, they are less expensive with much faster deposition rates and less material requirement.
展开▼
