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Solar Technology Boils Water in Radically Different Way

November 21, 2012 By Linda Hardesty

Rice University scientists unveiled a new technology that uses nanoparticles to convert solar energy directly into steam.

The new solar steam method from Rice’s Laboratory for Nanophotonics can even produce steam from icy cold water.

The technology has an overall energy efficiency of 24 percent compared to photovoltaic solar panels, which typically have an overall energy efficiency around 15 percent, according to Rice. And solar steam can have a very small footprint unlike PV systems, which can require acres of solar panels.

The efficiency of solar steam is due to the light-capturing nanoparticles that convert sunlight into heat. When submerged in water and exposed to sunlight, the particles heat up so quickly they instantly vaporize water and create steam. “We’re going from heating water on the macro scale to heating it at the nanoscale,” said LANP Director Naomi Halas, the lead scientist on the project. “Our particles are very small – even smaller than a wavelength of light – which means they have an extremely small surface area to dissipate heat. This intense heating allows us to generate steam locally, right at the surface of the particle, and the idea of generating steam locally is really counterintuitive.”

Steam is one of the world’s most-used industrial fluids. About 90 percent of electricity is produced from steam, and steam 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, and Halas said solar steam’s efficiency could allow steam to become economical on a much smaller scale by boiling water in a radically different way. 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.

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.


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