November 19, 2012
Harnessing Power Of The Sun To Produce Steam
[WATCH VIDEO: Creating Solar Steam With Nanoparticles]
Michael Harper for redOrbit.com — Your Universe Online
The details of this new technology have been published in today´s online edition of ACS Nano.
This “solar steam” process converts solar rays into usable energy at an impressive 24% rate of efficiency. By comparison, Rice University researchers say photovoltaic solar panels convert solar rays into energy at a 15% efficiency rate. Though solar steam is capable of using even more of the sun´s power efficiently, the Rice University researchers say they plan to employ this technology in third world countries for sanitation and water purification.
“This is about a lot more than electricity,” explained lead scientist and Director of Rice´s Laboratory for Nanophotonics (LANP), Naomi Halas, in a statement. “With this technology, we are beginning to think about solar thermal power in a completely different way.”
According to Halas, Rice´s solar steam is able to work so efficiently because it works on a much smaller scale. This new process makes use of very tiny nanoparticles which turn the sunlight directly into heat. These nanoparticles are then submerged in water and exposed to sunlight. Once the sun´s rays meet these particles, they begin to heat up so quickly that the surrounding water is turned to steam. As it stands, the solar steam process is very efficient in turning sunlight into steam. Halas predicts, however, that this process will become even more efficient as technology progresses.
“We´re going from heating water on the macro scale to heating it at the nanoscale,” Halas said in the statement. “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.”
According to the study, steam is one of the most used resources in the industrial world, and nearly 90% today´s electricity is generated from it.
Steam is used in a myriad of applications, from sanitizing medical equipment to cooking food and purifying water. It´s applications like these that Halas hopes will benefit from a little solar steam. The process of making steam is easy enough, requiring little more than bringing water to a high enough temperature. However in order to generate enough steam, many facilities require huge boiling tanks and heating elements. Halas said the solar steam will be able to create the right amount of steam on a much smaller scale, another factor which will make rolling out this new process in third world countries even easier.
“Solar steam is remarkable because of its efficiency,” said Oara Neumann, Rice graduate student and co-author of 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.”
Though the technology used to facilitate solar steam may be quite advanced, picking and choosing which wavelengths to interact with, Halas says the basic principles behind solar steam are quite simple.
“We´re not changing any of the laws of thermodynamics,” Halas said. “We´re just boiling water in a radically different way.”