Solar technology is beginning to heat up, thanks to researchers at Rice’s Laboratory for Nanophotonics (LANP). Scientists have developed a method of solar thermal heating that generates steam at the nanoparticle level. The new “solar steam” process is so efficient that vapor can be created from icy cold water. In addition to electricity generation, the new technique also has applications in water purification and sanitation.
A team of scientists at Rice’s Laboratory for Nanophotonics (LANP) led by Naomi Halas have taken solar thermal from large-scale heating down to the nano level. Published in the online journal ACS Nano earlier this month, the researchers detailed their groundbreaking work. “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.” said Halas. “We’re not changing any of the laws of thermodynamics,” she said. “We’re just boiling water in a radically different way.”
Solar steam technology has a rate of efficiency of around 24 percent, in contrast to conventional solar cells at 15 percent. The process is so effective that steam can be generated from near freezing water. In a demonstration, a tube of light-activated nanoparticles was submerged in a bath of ice water. The engineered particles are sensitive to a wide spectrum of light, including wavelengths that humans cannot see. Using a lens to intensify the sunlight into the tube, researchers were able to generate steam quickly from nearly arctic temperatures. Incredibly, the footprint of the technology is small, as it does not require large mirrors or panels, and the steam created is non-toxic.
Those living in developing countries may be the first to benefit from solar steam, particularly in relation to sanitation and water purification. Rice engineering students have already created a solar-powered autoclave that is able to sterilize medical equipment in areas that lack electricity. Halas has won a grant from the Bill and Melinda Gates Foundation to create a small scale sanitation system that can be used in places without a sewer infrastructure or generators. Other possible uses could include hybrid air-conditioning and heating systems that operate on steam during the day and electrical power at night. The Rice team is also in the process of working on water distillation experiments, and have so far found solar steam has been two and a half more times efficient than current methods.