Cool black surfaces could make NZ millions

Roasting dashboards and steering wheels, feet-scorching asphalt, burning leather sofas and sun-warped electronics — the colour black doesn’t pair well with our summer heat.

A black surface absorbs the most sunlight, transforming it into heat.

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

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

The 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 created “cool black” surfaces by increasing total solar reflectance of incoming radiation from 5 per cent to up to 20 per cent, says Dr Vivian Fang, a GNS Science nanoelectronics researcher.

While impressive, that still wasn’t enough to make them last as long as white surfaces, she said. “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 a very 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 boost the lifetime of building materials by half, while slashing energy costs for cooling and helping 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.”