New plasma technology creates 'smart' windows

Windows that efficiently conserve energy by responding to light, heat and other environmental factors may soon become a reality thanks to a team of environmentally aware, plasma surface engineering experts at the University of Sydney.

The rise of energy consumption in recent decades has led to an increasing demand for renewable energy and energy-saving systems. In response to this growing worldwide need, researchers have developed a more efficient and effective smart window that can block the flow of light and heat as required.

The study, which was led by Dr Behnam Akhavan from The Applied Plasma and Surface Engineering Research Group, focused on responding to the rise of energy consumption by using thin plasma fabricated coatings which were applied to glass windows.

The new technology consists of electrochromic coatings made of transparent materials that darken in colour with the application of a small electrical voltage.

Produced for the first time using a new plasma sputtering technology, the coatings are made up of a layer of silver that is approximately 10,000 times thinner than the width of human hair, placed in between two nano-thin layers of tungsten oxide.

Known as the fourth state of matter, plasma is created by adding energy to gas. Plasma is used most commonly in fluorescent light bulbs, neon signs and some television and computer screens.

“We showed for the first time that a new method of tungsten oxide deposition, known as HiPIMS, produces multifunctional coatings composed of only 3 layers for applications in smart windows” explained Dr Akhavan.

“Reducing the number of layers in the coating structure has significant implications for the manufacturing of smart windows, as it simplifies the process distinctly and reduces the cost of the final product.”

The plasma deposited material is applied to glass which can then be programmed to varying transparencies that change depending on the season. The glass responds to the environment by allowing more sunlight to enter a building on cold days, while minimising the in-flow of light on hot, summer days.

“Our findings open up the possibility of fabricating a new generation of materials that are transparent, conductive, and electrochromic.”

Double and triple glazing windows have long been a popular way of insulating against the cold in Europe and North America, however window insulation has traditionally been less popular in Australia.

On average, Australians spend $4.6 billion keeping cool each year, with heating and cooling making up almost fifty percent of energy costs in Australia, both of which have a negative environmental impact.

Previous smart windows coatings were limited to electrically conductive materials. The coatings developed by Dr Akhavan’s team can instead be used to convert any transparent material, including commercial glass and flexible polymers, to one which can change transparency when prompted by an electric signal. The process is carried out at room temperature and produces almost zero waste.

Dr Akhavan hopes the new technology will decrease dependency on air conditioning and other methods of electrical heating and cooling, so as to decrease Australians’ carbon footprint and environmental damage wrought by the burning of fossil fuels.

“To minimise the impact of climate change, we must invest in sustainable development by applying premium building materials which can insulate against the weather, whilst reducing our dependence on electricity.” he concluded.

The new study was published in ACS Applied Materials and Interfaces.”


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