A nanoparticle-based coating developed at the University of California San Diego can convert more than 90 percent of captured sunlight into usable heat, a leap that could transform solar-thermal systems used in desalination, industrial steam production, and power generation. The material, described in a peer-reviewed paper published in the journal Nano Energy and announced by the UCSD Jacobs School of Engineering, absorbs light across a far wider spectrum than conventional coatings, which typically capture only a fraction of available solar energy.
As of May 2026, the coating remains at the laboratory stage, and no outdoor field-trial data have been published. But the performance gap it demonstrates over existing materials has drawn attention from energy researchers looking for ways to make solar heat competitive with fossil-fuel-fired industrial processes.
How the coating works
Conventional solar-thermal surfaces are often dark, flat films designed to soak up sunlight. They work, but they leave a lot of energy on the table. Shorter and longer wavelengths at the edges of the solar spectrum tend to bounce off or pass through, and heat re-radiates back into the environment before it can be captured.
The UCSD team took a different approach. According to the peer-reviewed paper distributed through EurekAlert, the absorber is built from a composite of metal and ceramic nanoparticles arranged in a three-dimensional architecture rather than a flat layer. That structure acts like a series of tiny light traps: photons that would skip off a flat surface instead bounce between nanoparticles, getting absorbed at each interaction. The design also suppresses re-radiation, one of the main ways solar-thermal systems lose collected energy.
The result, measured under laboratory conditions, is absorption of more than 90 percent of incident sunlight across a broad spectral range. For comparison, many commercial selective absorber coatings operate in the 80 to 85 percent range under ideal conditions, according to performance data compiled by the International Energy Agency’s Solar Heating and Cooling Programme.
The project was funded through the U.S. Department of Energy’s SunShot initiative, now administered under the Solar Energy Technologies Office (SETO), which aims to make solar energy cost-competitive without subsidies. The research drew on expertise from UCSD’s departments of nanoengineering, bioengineering, and computer science, as well as its Center for Global Sustainability, a cross-departmental structure that signals ambitions beyond the lab bench.
A second study points in the same direction
The UCSD work is not an isolated result. A separate line of research, reported in January 2026 and published in ACS Applied Materials & Interfaces, tested gold nanoparticle clusters called “supraballs” as coatings for thermoelectric generators, devices that convert temperature differences directly into electricity.
Under an LED solar simulator, a supraball-coated generator achieved roughly 89 percent average solar absorption. A conventional film made from individual gold nanoparticles, tested under the same conditions, managed only about 45 percent. The near-doubling of absorption reinforces the core principle behind the UCSD coating: arranging nanoparticles into three-dimensional clusters traps wavelengths that flat films miss.
The two studies target different end uses. The UCSD material is designed for solar-thermal systems that produce heat directly, useful for desalination plants, food processing, or generating steam for industrial operations. The supraball coating is paired with a thermoelectric generator to produce electricity. But both demonstrate that nanostructured surfaces can capture dramatically more sunlight than their flat-film predecessors.
What still needs to happen before this reaches a rooftop
Strong lab numbers are a starting point, not a finish line. Several practical hurdles stand between these coatings and commercial deployment.
Outdoor durability. Nanoparticle coatings can degrade under sustained high temperatures, humidity, dust, and salt exposure. Neither study has published results from thermal cycling, long-duration outdoor operation, or accelerated weathering tests. A coating on a desalination plant in the Persian Gulf or a solar field in the Mojave Desert would face conditions far harsher than a climate-controlled lab.
Real-sun performance. The supraball study used an LED solar simulator, which provides consistent, repeatable illumination but does not replicate the shifting angles, cloud cover, and spectral variation of natural sunlight across seasons. The UCSD paper’s 90 percent figure was also measured under controlled conditions. Until both materials are tested outdoors over extended periods, the published absorption numbers should be treated as best-case benchmarks.
Manufacturing scale. Both coatings depend on precisely controlled nanoparticle sizes and arrangements. Scaling from centimeter-scale test samples to the square meters needed for an industrial absorber panel introduces risks of defects, non-uniformity, and batch-to-batch variation. Neither research group has published details on whether their fabrication methods can plug into existing coating production lines or would require specialized, capital-intensive equipment.
Cost. No cost-per-square-meter estimates appear in the available research summaries. For solar-thermal systems to compete with natural gas or other fossil fuels for industrial heat, the absorber coating must be not only efficient but affordable to manufacture, install, and maintain over a 20-to-25-year system lifetime.
Why solar-thermal efficiency matters now
Photovoltaic panels, which convert sunlight directly into electricity, have dominated the solar industry’s growth story for the past decade. But a large share of global energy demand is not for electricity at all. Industrial heat, used in everything from chemical manufacturing to cement production, accounts for roughly two-thirds of industrial energy consumption, according to the International Energy Agency. Most of that heat still comes from burning fossil fuels.
Solar-thermal technology offers a direct path to decarbonizing some of those processes: concentrate sunlight, capture it as heat, and pipe it where it is needed. The bottleneck has been efficiency. When absorber surfaces lose 15 to 20 percent of incoming sunlight to reflection or re-radiation, the economics tilt back toward gas burners. A coating that pushes absorption above 90 percent narrows that gap considerably.
Desalination is another sector watching closely. Thermal desalination plants, common in the Middle East and North Africa, require enormous amounts of heat to evaporate and condense seawater. More efficient solar absorbers could reduce the fossil-fuel input those plants depend on, lowering both operating costs and carbon emissions.
Where the research stands as of spring 2026
The UCSD nanoparticle absorber and the gold supraball coating both represent genuine advances in solar absorption, backed by peer-reviewed data and, in the UCSD case, federal research funding. The 90 percent and 89 percent figures are credible as laboratory measurements and mark a clear step beyond the performance of conventional flat-film coatings.
What they are not, at least not yet, is proof that these materials will survive years on a sun-baked rooftop, roll off a factory line at competitive prices, or deliver the same numbers under real skies. Independent replication, long-term field trials, and transparent cost analyses are the next milestones that will determine whether this research becomes a commercial product or remains a promising data point in the literature.
For industries that burn fossil fuels to generate heat, the stakes are high enough to keep watching.
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*This article was researched with the help of AI, with human editors creating the final content.
