The School of Electrical and Electronic Engineering at Nanyang Technological University (NTU) in Singapore has developed a smart window which can darken or brighten without the need for electricity.
Smart windows that are currently available either require an external power source to change their light transmission properties (for example, at Morgan Library in Colorado as reported earlier this month) or use permanent tinting which are unable to brighten at night.
The unique NTU solution is self-tinting and does away with the external power source. In fact, it is also able to store energy to act as a rechargeable battery and has enough power to light low-powered devices such as LEDs.
New technology turns the window a cool blue tint in daylight, which cuts light penetration in half. It then reverts to clear glass at night or when required during the day.
“Our new smart electrochromic window is bi-functional; it is also a transparent battery,” explained NTU professor Sun Xiaowei, who led the breakthrough technology. “It charges up and turns blue when there is oxygen present in the electrolyte – in other words, it breathes.”
The electrolyte used is in liquid form and serves as a sandwich filling between two glass sheets coated with indium tin oxide, which is commonly used as transparent conductive coatings for TVs.
A layer of pigment called Prussian Blue coats one glass sheet, while the other is connected to a thin strip of aluminium foil. It is the pigment which gives the glass its tint when fully charged.
Typical electrical cables create a circuit between the two sheets. When this circuit is broken, a chemical reaction is triggered between the pigment and the dissolved oxygen in the electrolyte which turns the glass blue. When the electrical circuit is closed to discharge the battery the tint reverts to colourless glass.
Sunlight penetration is a major contributory factor to both cooling and lighting costs. This technology intelligently adjusts the amount of sunlight coming into buildings without any environmental compromises.
“Our technology is very attractive as a zero-sum consumption smart window. Buildings owners and even common households can reap energy savings right from the outset and over the long term. Developers who are looking at constructing environmentally-friendly green buildings will find our technology attractive for their building plans,” said Sun.
Other innovations Sun has been involved in include various solar technologies, glass-free 3D technologies, next-generation lightings and displays.
The innovation is currently being refined and the NTU research team is now looking for industry partners to help commercialise the technology.