Environment

Recycled soot coating captures solar heat better than graphene

Recycled soot coating captures...
The team's solar stove, made up of a central container coated in a soot paste to increase solar heat absorption
The team's solar stove, made up of a central container coated in a soot paste to increase solar heat absorption
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The team's solar stove, made up of a central container coated in a soot paste to increase solar heat absorption
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The team's solar stove, made up of a central container coated in a soot paste to increase solar heat absorption

Tackling climate change doesn’t just require efforts like renewable energy – we need to clean up existing processes too. Now, engineers have developed a way to use soot from emissions to improve solar thermal devices, making them not only cheaper to produce but more efficient than using materials like graphene.

Gathering energy from the Sun doesn’t have to just involve photovoltaic solar cells – collecting its heat can also be used to generate electricity, purify water, cook food, or warm buildings. The best materials for absorbing this heat are dark in color, so different forms of carbon are most often used, including graphene or carbon nanotubes – the latter of which is used to make some of the blackest materials on Earth.

The problem is, producing these carbon materials in bulk can be fiddly and expensive. So for the new study, researchers at the University of Houston and Universidad Intercultural Indígena de Michoacán (UIIM) in Mexico have experimented with a far more common carbon form – soot.

A by-product of burning materials like coal, wood and hydrocarbon fuels, soot is an amorphous, impure form of carbon that wreaks havoc on the environment and human health. Collecting it from the point of emission can reduce these negative effects, and using it to improve renewable energy helps close the loop and cut costs.

“There is no energy involved in producing soot because it is an abundant byproduct, and its circular-reutilization can only reduce carbon footprints,” said Francisco Robles-Hernández, corresponding author of the study. “The cost is near-zero, which makes it cost-effective and ideal for solar to heat conversion.”

In the study, the researchers built a prototype solar stove. The device consisted of a mirrored dish that reflected and focused sunlight onto its center, where a container sat. This container was coated in a black solar-absorbing paste made with either soot or other forms of carbon, such as graphene, nanotubes and fullerene, to compare how well they worked.

And sure enough, soot outperformed the other materials in a few key areas. Its solar absorptivity was 96 percent higher than commercial products, its light emission was 85 percent higher, and it was 15 times cheaper. Compared to pristine carbon forms like graphene, soot coatings were up to 1,000 times cheaper.

The researchers say that soot-based heat-absorbing materials could be used for solar stills, heating for water pipes or homes, water purifiers, and industrial drying processes.

The research was published in the journal Carbon.

Source: University of Houston

4 comments
4 comments
EH
Most carbon black for industry is intentionally produced, and has been for centuries: "India ink" (really Chinese) has been colored with soot / carbon black for about 4500 years; tires are colored with carbon black, which greatly improves rubber's properties. Soot as an light absorber is a good idea, but hardly new.
paul314
This seems like a perfect application of the 80/20 rule, only more so. Sure, some super-whizbang tailored nanocoating could get you that last fraction of a percent in absorption, but at what cost? I hope they figure out how to collect their soot from ongoing burning processes, rather than manufacturing it bespoke...
Gordien
Could one use India ink as the door coating? That would make it very easy to coat, and later, to recoat of there is any degradation in use. Now if one can find good and inexpensive reflective materials.
Gordien
Not door coating - for a coating. Sorry.