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Researchers at the University of the Basque Country (EHU) have demonstrated groundbreaking results in the field of renewable energy, showing that newly developed nanomaterials – like nanoneedles – can absorb up to 99.5 percent of sunlight. EHU’s Thermophysical Properties of Materials research group collaborated with the University of California, San Diego (UCSD) to test copper cobaltate nanoneedles coated with zinc oxide. The results revealed superior optical and thermal performance compared to traditional materials like carbon nanotubes and black silicon. These results could pave the way for more efficient and durable solar tower systems, a cornerstone of next-generation renewable energy infrastructure. A leap beyond carbon nanotubes Concentrated solar power plants work by using hundreds of mirrors to direct sunlight onto a receiver tower that absorbs and stores heat energy. To achieve maximum efficiency, the absorbing materials on these towers must be “ultrablack” – capable of trapping nearly all incoming light while withstanding extreme heat and humidity. Vertically aligned carbon nanotubes have been the gold standard in light absorption, capable of trapping around 99 percent of sunlight. However, they degrade quickly under high temperatures and moisture, thus limiting their use in concentrated solar power (CSP) plants. “Carbon nanotubes are not stable at high temperatures and in the presence of high humidity. So they need to be coated with more resistant materials and that reduces their optimization,” explained Dr Iñigo González de Arrieta, lead researcher at EHU. “Carbon nanotubes absorb about 99 percent of the light, but they cannot be used on solar towers,” he continued. The tests revealed that copper cobaltate nanoneedles can overcome these limitations. They not only remain stable under extreme conditions but also deliver higher light absorption rates, particularly when coated with zinc oxide. Driving the future of renewable energy In contrast to conventional photovoltaic systems, CSP technology can store solar heat as thermal energy. It generates electricity even when the sun isn’t shining. This is achieved by heating molten salts, which retain energy efficiently and can later release it to power turbines. Despite its promise, CSP has historically been more expensive and complex than PV technology. An international collaboration The research, conducted at one of the few high-temperature labs in Europe capable of such measurements, is part of an international effort involving UCSD’s Dr. Renkun Chen, who is collaborating with the U.S. Department of Energy to test these nanoneedles on operational solar towers. Though in early stages, these studies mark a significant improvement toward materials that can make solar towers cleaner, more efficient, and more reliable. In Spain, CSP currently contributes approximately 5 percent of the country’s national energy generation, but experts believe that percentage could rise sharply as new materials like these are adopted. González de Arrieta emphasized the importance of developing new coatings with better light-absorbing properties for solar towers. He added that in the future, researchers may also investigate coating the nanoneedles with materials that enhance their conductivity.
