Scientists develop efficient selective solar absorber
US Scientists have developed a new technique for fabricating a highly efficient selective solar absorber (SSA) at a lower cost than existing methods. The research team created the 'dip-and-dry' process, which creates solar-absorbing nanoparticles of copper by dipping strips of zinc into a solution containing copper ions. This is less expensive and hazardous than existing manufacturing methods, such as vacuum deposition or electroplating, and has the potential to be scalable. The SSAs created also showed significantly higher absorption rates at all angles than existing designs, making them better at capturing sunlight throughout the day.

New York, NY—August 28, 2017—Researchers led by Yuan Yang , assistant professor of materials science and engineering at Columbia Engineering , along with colleagues at the Department of Chemistry at Columbia University, and Stanford University have developed a new, scalable, and low-cost “dip and dry” method for fabricating a highly efficient selective solar absorber (SSA) that can harness and convert sunlight to heat for use in a wide range of energy-related applications, from heating water and generating steam to residential heating.

The team’s method is outlined in a new paper, “Scalable, ‘Dip-and-dry’ Fabrication of a Wide-Angle Plasmonic Selective Absorber for High-efficiency Solar-thermal Energy Conversion,” published in Advanced Materials on August 28. The authors determined that the plasmonic-nanoparticle-coated foils created by their method perform as well or better than existing SSAs and maintain high efficiency throughout the day, regardless of the angle of the sun, due to the wide-angle design. They propose that the simple, inexpensive, and environmentally friendly process provides an appealing alternative to current SSA fabrication methods. “We saw an unmet need for a facile, inexpensive, and sustainable method for fabricating high-performance SSAs,” said Yuan Yang. “We were pleased that our relatively simple process produced SSAs that performed on par with commercial SSAs and designs reported in other research. To our knowledge, this is the first time a plasmonic SSA has been made using such a process, and the scalability and cost of this approach brings us closer to making solar energy a practical reality for more people.”

Harvesting sunlight for renewable energy remains a primary objective for scientists. Solar-thermal converters, which can absorb light across the entire solar spectrum and convert it to heat at remarkably high efficiencies, offer a highly promising pathway for solar-energy harvesting. However, attaining high-efficiency solar-thermal conversion at low cost remains a challenge. As a surface component of solar-thermal converters, SSAs are ideal because they have contrasting optical properties for solar and thermal radiation. They are very black across all colors of sunlight (from UV to visible to near infrared light) and can therefore absorb almost all the light and become very hot. However, unlike common black surfaces, they are metallic, i.e. non-emissive, when it comes to thermal radiation (mid- to far-infrared light). Heat is therefore not lost as radiation and can be used, for example, to heat water or generate steam. Most SSAs are made using more sophisticated, energy-expensive, or hazardous manufacturing processes such as vacuum deposition or electroplating. This increases both the environmental footprint and cost while limiting their accessibility. As a basis for manufacturing SSAs, the dip-and-dry process is an attractive option, as it yields SSAs that are highly efficient, while bypassing the costs and environmental hazards associated with other approaches.