HOUSTON, Texas — Researchers at Rice University have found a method of turning water directly into steam using nanotechnology. With some help from the Bill and Melinda Gates foundation, they have devised a practical application that can sterilize water.
The technology, which is featured in the Proceedings for the National Academy of Science Early Edition makes use of nanoparticles (microscopic particles with at least one dimension less than 100 nanometers).
These particular nanoparticles are based on a previous model created by lead researcher, Namoi Halas. Halas had previously engineered a particular nanoparticle referred to as nanoshells, which are now being tested as a treatment in cancer trials.
For this project, the study took advantage of graduate student Oara Neumann’s variant of the nanoshells, which she engineered to be sensitive to a broad spectrum of light. When exposed to sunlight and placed in water, the nanoshells heat up so quickly they immediately vaporize the water — converting it to steam.
According to Halas, “[The particle] makes steam directly from sunlight. That means the steam forms immediately, even before the water boils.”
During tests in the lab, the pressure created by the steam was enough to kill living microbes, spores and viruses. In fact, the heat and pressure were so great that even the most heat-resistant microbes were killed.
Moreover, the nanoshells technology is terribly efficient. In tests, the particles had an overall energy efficiency of 24%. By contrast, standard photovoltaic solar panels typically have energy efficiency ratings right around 15%.
According to Neumann this is a high degree of efficiency, an important fact since they needed to meet certain requirements for their project funders — the Bill and Melinda Gates Foundation. The requirement given to them explained that the particles needed to be developed in an application which could handle the waste of a family of four with just two treatments per week. Their tests proved that the particles appeared to be able to do just that.
The importance of this project cannot be overstated. While many water projects often focus on more glamorous aspects of water safety, such as drinking water, this project focuses on treating and sanitizing waste.
As Halas puts it, “Sanitation technology isn’t glamorous, but it’s a matter of life and death for 2.5 billion people. For this to really work, you need a technology that can be completely off-grid, that’s not that large, that functions relatively quickly, is easy to handle and doesn’t have dangerous components. Our Solar Steam system has all of that, and it’s the only technology we’ve seen that can completely sterilize waste. I can’t wait to see how it performs in the field.”
The team is currently attempting to begin field trials with Sanivation, a sanitation company in Kenya. If they can make Solar Steam work in practice, this will be another application of nanotechnology helping to fight poverty in developing countries.