Rice Uni Scientists Develop Nanoparticles That Let Off Some Steam

Researchers at Rice University have come up with a new solar solution that could be applied as sanitation and water purification solutions in countries where potable water remains a luxury for many. Using nanoparticles to convert solar energy into steam, the method is said to be so effective it was captured on video producing steam from icy cold water. The technology was developed at Rice's Laboratory for Nanophotonics (LANP).

When submerged in water and exposed to sunlight, the light-capturing nanoparticles heat up so quickly they instantly vaporize water and create steam. One of the breakthroughs here is the level of efficiency; that is, the percentage of solar light that is converted into energy. While photovoltaic solar panels currently average an efficiency of 15 percent, the solar steam technology reaches an overall rate of 24 percent, although its initial intended use is not electricity generation.

"This is about a lot more than electricity," said LANP Director Naomi Halas, the lead scientist on the project. "With this technology, we are beginning to think about solar thermal power in a completely different way." She added the system's overall energy efficiency can probably be increased as the technology is refined.

Halas and Rice graduate student Oara Neumann Neumann set out to design a particle that would interact with the widest possible spectrum of sunlight energy. Their new nanoparticles are activated by both visible sunlight and shorter wavelengths that humans cannot see.

Steam is one of the world's most-used industrial fluids, generating about 90 percent of the world's electricity and is also used to sterilize medical waste and surgical instruments, to prepare food and to purify water. Most industrial steam is produced in large boilers. Halas said solar steam's efficiency could allow steam to become economical on a much smaller scale.

People in developing countries will be among the first to see the benefits of solar steam. Rice engineering undergraduates have already created a solar steam-powered autoclave that's capable of sterilizing medical and dental instruments at clinics that lack electricity. Halas also won a Grand Challenges grant from the Bill and Melinda Gates Foundation to create an ultra-small-scale system for treating human waste in areas without sewer systems or electricity.

Another potential use could be in powering hybrid air-conditioning and heating systems that run off of sunlight during the day and electricity at night. Halas and her team have also conducted distillation experiments and found that solar steam is about two-and-a-half times more efficient than existing distillation columns.

Details of the method were published online in ACS Nano on November 19.

Image credit: Rice University