Ultra-black material for solar thermal power plants absorbs 99.5% of sunlight.

Energy

Technological Innovation Website Editorial Team - October 30, 2025

Idealized view of a solar thermal farm. [Image: SIT/AI Generated]

All black

When you look at a solar thermal power plant , everything seems extreme: A huge field of mirrors captures the sun's heat, directing it toward a tower the size of a 20-story building, where the scorching heat is used to heat a fluid, which is then used to power turbines and generate electricity.

Therefore, it is quite surprising that the efficiency of these clean and renewable energy plants depends on structures so small that they are invisible to the naked eye – in fact, a very powerful microscope is needed to see them.

The goal here is to find the material with the highest possible thermal absorption rate, so that it can capture the maximum amount of heat whenever the sun is shining. In practical terms, it's about producing the blackest possible material so that it absorbs as much of the spectrum as possible without reflecting anything, thus capturing the maximum amount of heat.

"The more we can develop more effective absorbent materials, the more competitive the systems will be and the more opportunities we will open up for this type of energy," comments Professor González de Arrieta, from the University of the Basque Country, in Spain. "We carry out thermo-optical analyses to measure the absorption properties of the samples we receive. Internationally, there are few laboratories dedicated to high-temperature research."

And now the team has found a material that has emerged not only as one of the most efficient ever evaluated, but also exhibits the necessary properties for its practical use in solar thermal power plants.

The entire gigantic structure of the solar thermal farm depends on these nanostructures, invisible to the naked eye. [Image: González de Arrieta et al. - 10.1016/j.solmat.2025.113840]

Better than carbon nanotubes.

The blackest material ever manufactured was made with carbon nanotubes . However, although these tiny tubes are record-breakers in almost every laboratory setting, they are not suitable for all practical applications.

"Carbon nanotubes are not stable at high temperatures and in the presence of high humidity. Therefore, they need to be coated with more resistant materials, which limits their optimization. Carbon nanotubes absorb about 99% of light, but they cannot be used in solar towers," Arrieta explained.

The team then identified another nanostructure, a nanoneedle – these nanoneedles are not hollow like nanotubes – made of a substance called copper _cobaltate ( _CuCo2O4 ).

"They are much more stable at high temperatures and, in addition, the zinc oxide-coated nanoneedles have greater absorption than the nanotubes used until now. The materials currently used in solar towers (black silicon) absorb 95% of the light, which is a lot; however, copper cobalt nanoneedles absorb 99% of the light, and those coated with zinc oxide even more, 99.5%," said Arrieta.

The team expects their material to be quickly taken to real-world operating conditions for testing, promising to significantly increase energy generation even at already installed solar thermal power plants.

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