Scientists in China have developed a new "smart" window which doubles as an energy-generating solar cell.

Yanfeng Gao and a team of colleagues from the Chinese Academy of Social Sciences developed the solar cells by leveraging the unique properties of vanadium oxide (VO2), a material which undergoes a reversible phase transition at different temperatures, and is capable of displaying both metallic and insulating properties.

Beneath the critical temperature of 68 degrees Celsius, VO2 is an insulating material which is transparent to infrared light. Above this temperature threshold, however, it becomes metallic and reflects infrared light instead of permitting its passage.

chinese solar cell inventionThis peculiar quality of VO2 enabled the scientists to overcome the challenge of incorporating a solar cell into a window, a feat which requires a material which is transparent yet also capable of efficiently harvesting the sun’s energy.

The scientists installed a VO2 film into the smart windows where it serves two purposes – it disseminates sunlight to photovoltaic cells situated around the glass panels, thus generating power for domestic usage, while also acting as an insulator by regulating the amount of solar energy which can penetrate the indoor environment.

The incorporation of the VO2 film thus enables the windows to save energy as they generate it, marking a major advance upon existing smart windows, which are only capable of regulating the entry of light and heat from the sun.

“This smart window combines energy-saving and generation in one device, and offers potential to intelligently regulate and utilize solar radiation in an efficient manner,” said the scientists in a study published in the journal Scientific Reports.

The development of the smart window follows efforts by the Chinese government heavily promote renewable energy and green engineering, in a bid to tackle the severe environmental problems which the country’s breakneck economic development has brought.

Xie Zhenhua, the vice chairman of China’s National Development and Reform Commission, one of the country’s top decision-making authorities, announced in July that China plans to spend as much as 1.8 trillion yuan (US$294 billion) in the five years through 2015 to tackle climate change.

Beijing has further pledged to reduce carbon emissions per unit of economic output by as much as 45 per cent before the end of the decade compared to 2005 base levels.