Super solar steam

Can water be boiled in a totally new way? Yes, and in the process provide much needed energy to so many industrial processes and sanitation!

Rice University scientists have unveiled a revolutionary new technology that uses nanoparticles to convert solar energy directly into steam. The new "solar steam" method from Rice's Laboratory for Nanophotonics (LANP) is so effective it can even produce steam from icy cold water.

The technology has an overall energy efficiency of 24 percent. Photovoltaic solar panels, by comparison, typically have an overall energy efficiency around 15 percent. However, the inventors of solar steam said they expect the first uses of the new technology will not be for electricity generation but rather for sanitation and water purification in developing countries.

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. 

A solar steam demonstration showed a test tube of water containing light-activated nanoparticles submerged into a bath of ice water. Using a lens to concentrate sunlight onto the near-freezing mixture in the tube, the scientist showed she could create steam from nearly frozen water. 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.

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.

"Solar steam is remarkable because of its efficiency," said Neumann, the lead co-author on the paper. "It does not require acres of mirrors or solar panels. In fact, the footprint can be very small. For example, the light window in our demonstration autoclave was just a few square centimeters."

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, Neumann and colleagues have also conducted distillation experiments and found that solar steam is about two-and-a-half times more efficient than existing distillation columns.

As we go on, wonder what exciting discoveries remain to unfold!