The World's Whitest Paint - A Cool Solution to Global Warming?

As the mercury soars to new heights this week, the world is once again reminded of the urgent need to address the escalating crisis of climate change. Unprecedented heatwaves are not only breaking temperature records worldwide, but they are also breaking our illusions of time - the time to act being now. Addressing these formidable challenges requires innovative solutions, and in this edition of Horizons, we delve into an interesting concept from an unexpected source: the world's whitest paint. 

Developed by Professor Xiulin Ruan and his team at Purdue University in Indiana, the paint boasts an exceptional ability to reflect sunlight and radiate heat into space. According to the scientists, this ultra-white paint can reflect 98.1% of solar radiation while also emitting more heat than it absorbs. In the past, the whitest paints only reflected around 80-90% of sunlight and couldn't cool surfaces below ambient temperatures. This new formulation is a major leap forward, potentially reducing reliance on air conditioning systems, one of the significant contributors to energy consumption and carbon emissions worldwide.

The science behind the paint's high reflectivity lies in its composition. Instead of traditionally used titanium dioxide, the researchers used barium sulphate, a compound that enables more UV radiation to be reflected than its predecessors. By incorporating different sizes of barium sulphate particles in the paint, they also managed to scatter substantially more of the light spectrum from the sun, further enhancing its cooling properties.

With the implications of rising global temperatures, solutions like the whitest paint could play a pivotal role in combating the urban heat island effect - the phenomenon where urban and suburban regions experience higher temperatures than their rural surroundings due to human activities. Applying this super-reflective paint on rooftops and buildings in such areas could help keep them and the surrounding areas cooler.

The paint’s effects have been measured in a range of outdoor conditions. It can keep surfaces circa 10°C less than their surrounding temperature at night and circa 4.5°C less under strong sunlight.

“If you were to use this paint to cover a roof area of about 1,000 square feet, we estimate that you could get a cooling power of 10 kilowatts. That’s more powerful than the central air conditioners used by most houses." - Xiulin Ruan.

In addition, the heat is not significantly transferred to the earth's atmosphere. “We’re not moving heat from the surface to the atmosphere. We’re just dumping it all out into the universe, which is an infinite heat sink,” said Xiangyu Li, who worked on this project as a Ph.D. student in Ruan’s lab. 

Ruan and his team are currently investigating the application of the paint to surfaces other than buildings, such as cars and aeroplanes, as the properties of the paint are further refined for thin and long-life application. 

The paint is not yet commercialised and while promising, it is a mitigation rather than a fundamental solution to climate change. Nevertheless in the years to come, it will likely be significant as part of a broader suite of strategies encompassing policy changes, real emissions reduction and renewable energy generation.

The world's whitest paint offers a shimmer of hope in the vast canvas of climate action.

Until next week,

Derek