Lightpoet/Adobe Stock
Lightpoet/Adobe Stock

Researchers at the Columbia University School of Engineering—together with with Columbia's Department of Chemistry and Stanford University—have developed a new method for developing selective solar absorbers (SSA), the surface components of solar-thermal converters that trap and convert sunlight to heat. This heat can then be used as energy to heat residential buildings and water, as well as to generate steam.

The simple “dip-and-dry” process, developed by Yuan Yang, assistant professor of materials science and engineering at Columbia University School of Engineering, and his team, is performed by dipping reactive, zinc-coated strips into a solution of ions and copper. The solar-absorbing nanoparticles of copper are then formed on the zinc strips through a galvanic displacement reaction.

In the past, scientists have been challenged with trying to produce highly efficient, solar thermal conversions at low costs. The dip-and-dry process allows SSA's to remain efficient while avoiding environmental hazards and high costs of SSA's produced with traditional methods. Other production methods such as vacuum deposition or electroplating create hazardous waste materials, and require large amounts of energy.

Another issue traditional SSA's run into is the fact that they can only absorb sunlight throughout the day, and are affected by the angle of the sun—which, depending on the time of day, can reduce efficiency. The SSA's developed by Yuan and colleagues performed just as well or better than previously developed SSA's, and maintained efficiency regardless of the position of the sun, through its wide-angle design.

"We saw an unmet need for a facile, inexpensive, and sustainable method for fabricating high-performance SSA's," said Yang to Tech Xplore. "To our knowledge, this is the first time a plasmonic SSA has been made using such a process.” The study was published in Advanced Materials on Aug. 28.