Fluorescent, coloured-cooling materials could be used for roofing, keeping houses cool in summer and warm in winter, potentially reducing energy consumption for cooling and heating, new research suggests.
It has been recognised for several years now that dark roofs barely reflect any light and absorb solar radiation, meaning they trap a lot of heat during the day, so both house and neighbourhood are hotter. Lighter colours, on the other hand, can reflect around 80 per cent of sunlight during the day and absorb less radiation.
As a consequence, researchers have been exploring the use of ‘PDRC’ (photo-dependent radiative cooling) materials that can cool buildings without relying on energy-intensive air conditioning or heating. These materials are designed to reflect sunlight and emit infrared radiation, which helps to cool the roof surface.
Architectural engineer Hassan Khan and his colleagues at UNSW have now taken this a little further by adding a fluorescent coloured film on top of PDRC materials. The materials are known as ‘passive-coloured radiative coolers’.
In a recent study led by Dr Khan, several colour configurations (using orange, red and green) were revealed to have similar cooling effects to white PDRC materials in hot and dry conditions, while also retaining some warmth in winter.
One of the orange cooler tests in Alice Springs was found to be on par with a PDRC reference sample. Meanwhile, testing in Sydney during winter saw orange, green and red configurations result in temperatures up to 3.8C, 3.6C, and 5.5C hotter than a PDRC.
Dr Khan said fluorescent dyes were added to a synthetic film for the study, but that researchers could develop other forms of the 'super-cool' material.
"Now we are going to bring [coloured super-coolers] into a paint form, and those paints can be applied on any surface," he said, adding that using fluorescent dyes was also cheap, making the technology more scalable.
The results of the study have been published in the peer-reviewed journal Solar Energy Materials and Solar Cells.