Windows are a key component in a building's design, but they are also the least energy- efficient part. According to a 2009 report by the United Nations, buildings account for 40 percent of global energy usage, and windows are responsible for half of that energy consumption. If conventional windows are used to better block sunlight passing into a building, they need expensive coatings. Even so, they can not adjust the indoor temperature effectively.
Scientists at the Nanyang Technological University, Singapore (NTU) have developed a smart liquid window panel that can help. By creating a mixture of micro-hydrogel (水凝胶), water, and a stabilizer, they found that it can effectively reduce energy consumption in a variety of climates. Thanks to the hydrogel, the mixture becomes hard-to-see- through when exposed to heat, thus blocking sunlight, and, when cool, it returns to its original clear state. The high heat capacity of water allows a large amount of heat energy to be stored instead of getting transferred through the glass and into the building during the hot daytime when office buildings mainly operate. The heat will then be gradually cooled and released at night when the staff are off duty.
As a proof of concept, the scientists conducted outdoor tests in hot (Singapore, Guangzhou) and cold (Beijing) environments. The Singapore test revealed that the smart liquid window had a lower temperature (50℃) during the hottest time of the day (noon) compared to a normal glass window (84℃), The Beijing tests showed that the room using the smart liquid window consumed 11 percent less energy to maintain the same temperature compared to the room with a normal glass window. They also measured when the highest value of stored heat energy of the day occurred. This "temperature peak" in the normal glass window was 2 pm, and in the smart liquid window was shifted to 3 pm. If this temperature peak shift leads to a shift in the time when a building needs to draw on electrical power to cool or warm the building, it should result in lower energy charges for users. The research team is seeking ways to cut down the cost of producing the smart window and so far, they have found several industry partners to commercialize it.
