Every moment, approximately 89,000 terawatts of solar energy strike the Earth's atmosphere, presenting an incredible opportunity for harnessing renewable energy. However, current solar technologies are akin to attempting to collect a torrent of water with a leaky bucket.
Solar radiation encompasses a variety of wavelengths: around 3 to 5 percent is ultraviolet, 40 to 45 percent is visible light, and a substantial 50 to 55 percent falls within the infrared spectrum. Conventional photovoltaic cells, commonly seen on rooftops, effectively convert visible light and a fraction of near-infrared light into electricity, but they fail to capture the abundant heat-rich infrared energy.
Researchers in South Korea, however, are addressing this challenge with innovative solutions.
The Infrared Challenge
Efforts to harness the lost infrared energy have led to the development of extensive mirror arrays and solar-thermal collectors, which can absorb both visible and infrared light to generate heat. Yet, these systems often struggle with efficiency due to subpar surface coatings that do not achieve complete absorption.
While engineered nanomaterials, including gold and silver nanoparticles, have been explored, they typically absorb only visible wavelengths, leaving the energy-dense infrared spectrum largely unutilized. To combat climate change and optimize energy production, a new material capable of harnessing the entire solar spectrum is essential.
Introducing the "plasmonic supraball." This innovative approach involves thousands of gold nanoparticles that self-assemble into microscopic clusters known as supraballs.
A Photon Trap
Researchers at the KU-KIST Graduate School of Converging Science and Technology have developed a technique to create these supraballs, which fundamentally alter the interaction of gold with light. When sunlight strikes these structures, the outer layer captures visible and ultraviolet rays, while the dense core traps longer near-infrared waves. This process effectively transforms light into heat.
Enhanced Efficiency and Simplified Production
The efficiency of these supraball films is remarkable, absorbing roughly 89 to 90 percent of the solar spectrum. This is a significant improvement over traditional gold nanoparticle films, which achieve about 45 percent absorption.
To assess their practicality, the researchers applied the supraball solution to a commercial thermoelectric generator (TEG), which converts heat into electricity. The resulting film produced approximately 2.4 times more electrical power compared to standard nanoparticle coatings.
What sets this technology apart is its ease of manufacturing. Unlike traditional methods requiring costly vacuum chambers and trained personnel, the supraball solution can be simply dripped onto surfaces and dried at room temperature. This affordability allows for easy application to various thermal-based solar systems.
"Our plasmonic supraballs provide a straightforward method for capturing the complete solar spectrum," states researcher Seungwoo Lee. "This coating technology has the potential to significantly reduce barriers for high-efficiency solar-thermal and photothermal systems in practical energy applications."
This plug-and-play upgrade could revolutionize the renewable energy landscape, demonstrating that substantial improvements can be achieved without overhauling existing infrastructure.