A smart solar window capable of producing electricity and, at the same time, regulating the quantity of solar radiation entering a building.
A group of Chinese scientists has developed a new one intelligent photovoltaic windowcapable of generating electricity and calibrating the amount of solar radiation that penetrates a building.
The system was presented in the article “Assessing the energy efficiency and grid friendliness of smart photovoltaic windows incorporating crystalline silicon cells and electrochromic film,” published in Applied Energy. The research was conducted by scientists from Hunan University and the Key Laboratory for Building Safety and Energy Efficiency of China’s Ministry of Education.
The study proposed an integrated window with control strategies to simultaneously improve the energy efficiency of buildings and the electricity grid. The results revealed that, compared to conventional low-e windows, the smart window with the heat flow control strategy managed to achieve significant reductions, including those related to the overlighting ratio and annual net energy consumption.
The system uses crystalline silicon cells and a film called electrochromic. This device, called photoelectrochromic, has a dual function: on the one hand, it transforms sunlight into electricity, and on the other, it allows you to adjust the level of transparency of the window. In this way, it helps control how much solar radiation enters the building. The window is made up of 5 layers containing the device and sealed between the transparent and low-e glass layers.
When no voltage is applied, the electrochromic (EC) film is in a state of transparency and the visible transmittance is maximum. However, when voltage is applied, the lithium ions in the accumulation layer move towards the electrochromic layer, which thus begins to colour. The higher the voltage applied, the darker the film becomes, reducing the transmittance of visible light.
This structure was designed using a program called Window and then simulated with building-specific software called EnergyPlus. A building 50 meters long, 4.6 meters deep and 2.7 meters high was hypothesized, with 77% of the walls occupied by windows. The simulations were done for the hottest period, from May to October, in four Chinese cities: Fuzhou, Xiamen, Hong Kong and Haikou. The smart window has been shown to improve energy efficiency and interior comfort compared to traditional windows by adapting to both sunlight and heat passing through the structure. The smart window, with the heat flow control strategy, also showed an overall average performance improvement of 55.5%.
