Rice uses nanoparticles to push solar to a new frontier

Researchers at Rice University have passed a new frontier in solar energy, using nanoparticles to create steam within seconds, before the water reaches the boiling point.

The process could be used to sterilize medical instruments and process waste in the developing world, said Naomi Halas, director of the Laboratory for Nanophotonics at Rice.

It could also be used to desalinate seawater or in other industrial processes, or even ramped up to produce electricity, she said.

Halas, a chemist, was the lead scientist on the solar steam project; the details were published online this week in the American Chemical Society’s journal ACS Nano.

“What’s unique about this technology is you can develop it into relatively small footprint sources of energy, off-grid,” Halas said.

Steam is one of society’s oldest technologies, the power source behind the Industrial Revolution. Merging it with nanoparticles, a decidedly 21st century technology, could help to solve some of the thorniest problems facing the developing world, Halas said.

She said a conversation with Rebecca Richards-Kortum, chair of the department of bioengineering at Rice and a force behind the university’s push to create technologies to address health and social problems in the developing world, gave her new insight into ways the technology could be used.

“It was a transformative conversation about the needs in the Third World,” Halas said.

The project differs from conventional  photovoltaic solar panels in a number of ways.

For one thing, Halas said it is far more efficient, with an overall energy efficiency of 24 percent, compared to a top efficiency of 12 percent to 15 percent for conventional solar panels.

The process works by submerging light-capturing nanoparticles into water. When exposed to sunlight, they heat up and vaporize the water to create steam.

“It takes a lot of energy to heat water,” Halas said. “You think about making pasta, making tea,
you don’t get steam until you heat a large volume of water to the boiling point. We’re short-cutting that by putting nanoparticles in water to generate steam directly.”

She said a variety of nanoparticles would work. In conjunction with Rice graduate student Oara Neumann, Halas designed a particle activated by both visible sunlight and shorter wavelengths that humans can’t see.

“The key thing is they have to absorb light across the solar spectrum,” she said. “They have to be black.”

One of Halas’ earlier creations, gold nanoshells, is being studied in several clinical trials for cancer treatment.

The solar project was supported in part by grants from the Bill and Melinda Gates Foundation and the Welch Foundation.

Halas said work to move the project into the field is under way. “This is not something that’s 20 years away,” she said.


About The Author

Jeannie Kever joined the Houston Chronicle's energy team in September 2012. A native of West Texas, she has been at the Houston Chronicle since 1997, working in the features department for 10 years before moving to the city desk, where she reported on higher education, the 2010 Census and health care before moving to the business desk. She previously worked at the Sarasota (Florida) Herald-Tribune, the San Antonio Light, the Longview (Washington) Daily News, the El Paso Times and the San Angelo Standard Times.