Not far from Aydil’s lab, Professor Jane Davidson (mechanical engineering) is working on another type of solar research that focuses on solar thermal energy.
Davidson began her work on solar energy in 1986 at Colorado State University, and over the past five years has been able to focus almost exclusively on solar. She is, she said, “fortunate that in the course of my career the subject has become popular. I have a real passion for it scientifically but also because of the role solar can play in creating a more environment-friendly world.”
Currently that passion is channeled into two main areas of solar thermal research. In collaboration with several other Institute of Technology faculty—professors Susan Mantell and Francis Kulacki (both mechanical engineering) and Lorraine Francis (chemical engineering and materials science)—she is developing ways to produce lower-cost solar heating systems manufactured of plastic rather than of copper and glass. She and the other faculty are also addressing the scientific challenges to implementation. They are developing improved storage systems and methods to reduce scaling on the polymer surfaces of solar units. In addition, the team is working to determine the long-term durability of different kinds of polymers when exposed to hot, chlorinated water.
Davidson’s second project takes her to the cutting edge of solar research: using solar heat to produce hydrogen from water.
“The Holy Grail would be if you could split water directly, using solar energy to separate the oxygen from the hydrogen,” she said. But because of a number of reasons, this way of producing fuel isn’t feasible. So she and Aldo Steinfeld (Ph.D. ME ’89), a University alumnus and current professor at the Swiss Federal Institute of Technology, are working on a two-step water-splitting cycle using a solar reactor or furnace—an instrument that captures and concentrates solar energy, generating temperatures as high as 2500 degrees Celsius—to separate zinc oxide into zinc and oxygen.
The second step in the process, which is the focus of her research, involves hydrolysis: exposing the zinc to steam produces hydrogen and metal oxide, which is then recycled into the solar reactor to begin the two-steps all over again. The net reaction is water splitting—a “totally green” process.
“The problem with the second step—the reaction of zinc and water—is that zinc quickly forms a zinc oxide layer that protects it from further hydrolysis. That’s why zinc is used as a coating on iron and steel to protect against corrosion,” she explains. Once that layer is formed, the rate of hydrogen production slows down.
Her answer to this dilemma is to use zinc nanoparticles in the second stage of the process. To that end, she and her research team have constructed a reactor that evaporates zinc in order to form zinc nanoparticles while simultaneously hydrolygizing the particles. The result? The researchers can retrieve almost all the potential hydrogen.
That’s the good news. But there’s still much work to be done. “We’ve achieved excellent results for conversion efficiency,” Davidson said, “But what we’re finding is that most of the hydrogen is being produced not from the nano aerosol but from zinc that has been deposited on the reactor walls. The recuperation of zinc oxide for recycling into the solar reactor is still something we’re working on.” Only when that puzzle is solved will the process become economically feasible.
Still, Davidson remains hopeful of the future, especially since, as she explains, “We have unique capabilities here at the Institute of Technology, with such a strong focus on energy and nanoscience.
“We’ll be able to do it,” she declares. “It’s just a matter of time.
