Black paint that stays cool could make NZ millions

Designing black surfaces that keep cool in the sun could boost New Zealand's paint exports by more than $200 million, within only five years of being introduced. Photo / 123RF

Roasting dashboards and steering wheels, feet-scorching asphalt, burning leather sofas and sun-warped electronics - the colour black isn't something that pairs well with our summer heat.

That's of course because a black surface absorbs the most sunlight, transforming it into heat that our bodies can keenly sense on warm afternoons, while over-heating and damaging the object itself.

But what if we could create black surfaces that kept cool in the sun?

It's a challenge scientists are now tackling in a new innovation that could boost New Zealand's paint exports by more than $200 million within only five years of being introduced.

The project's goal is to engineer novel composite materials that reflect most of the invisible near infrared radiation - while somehow preserving the optical impression of blackness.

Recent technologies have formulated "cool black" surfaces by increasing total solar reflectance of incoming radiation from 5 per cent to up to 20 per cent, GNS Science nanoelectronics researcher Dr Vivian Fang said.

While impressive, that still wasn't enough to make them last as long as white surfaces.

"We will develop a true cool black pigment, distinct in its ability to reflect the vast majority of solar radiation."

Earlier experiments by Fang and colleagues had revealed how optical properties were controlled by a combination of particle size, shape and composition.

In a study awarded a million-dollar Government grant, her team would take that work further by designing and making a cool black pigment with an incredibly high solar reflection value.

"We can create novel composites with decorated nano to micro-scale structures, which are visually dark, yet reflect the near infrared wavelength," Fang said.

"By using the team's expertise in physics, physical chemistry and optics, we will answer the paradoxical question: can black surfaces strongly reflect infrared radiation and be cool?"

The coatings would be designed in a rapid, low-cost, and non-chemical way, and with strong near infrared reflectance - making them ideal for mass manufacture.

"We envision new high-tech manufacturers producing cool black pigments for direct export and sale to New Zealand's paint manufacturers.

"A cool black paint would increase New Zealand's paint exports by over $200 million within five years of introduction, with the pigment itself likely achieving higher earnings."

The global roof coating market was expected to reach nearly $2 billion in value by 2022 - and there was further potential to use the technology in novel colour-changing iridescent and fire-resistant paints.

It could also boost the lifetime of building materials by half, while slashing energy costs for cooling, lowering greenhouse gas emissions, and helping to preserve whakairo, or Maori carvings.

"Our research will enable a new industry in New Zealand to fabricate these materials, and manufacture and sell these materials to meet the future demand for cool black surfaces," Fang said.

"Companies including high-value manufacturers, investors and Maori-owned businesses in New Zealand will benefit from this work as being partners in the supply chain."