9/19/2013 If you have any questions about the College of Engineering, or other story ideas, contact Mike Koon, writer/editor, Engineering Communications Office, University of Illinois at Urbana-Champaign, 217/244-1256.
Written by If you have any questions about the College of Engineering, or other story ideas, contact Mike Koon, writer/editor, Engineering Communications Office, University of Illinois at Urbana-Champaign, 217/244-1256.
While wind and solar are in vogue as alternative means to produce energy, researchers are also discovering energy sources, such as taking waste heat from a nuclear reactor to produce electricity. To develop new materials for these applications, University of Illinois researchers take advantage of high performance computers such as the Illinois Campus Cluster.
“High-performance computers have become essential to research in many disciplines across the Illinois campus, from Big Data applications, to astronomy, biology, and chemistry on through the alphabet to zoology,” explained Chuck Thompson, assistant dean and chief information officer for the College of Engineering. “The Illinois Campus Cluster program is a campus-wide resource that helps meet this need for research computing cycles.”
“Thanks to this computational power (our algorithm tools and capabilities) increase, there are so many exciting things that we can do now in materials design that even five years ago were not accessible,” explained Elif Ertekin, an assistant professor of mechanical science and engineering (MechSE). “In some cases, we’re getting to the point where the fidelity of the computer modeling is actually close enough to reality that you can simulate across a whole spectrum of materials before testing them in an experimental laboratory.”
The genesis of Ertekin’s research also coincided with the addition of the Campus Cluster, which provides a shared research-computing environment.
“It was really key for us that within a couple months of my arrival on campus, we had an up-and-running workhorse computing system that was ready to do the calculations we need to do,” Ertekin added. “The rapidity was a key part of my group being able to establish itself very quickly.”
Applications require high-performance computing
Ertekin is using quantum mechanics based modeling and simulation to optimize the performance of materials for thermal transport. She is exploring whether nanostructured materials can be useful for thermal waste recovery, taking the waste heat that is being exhausted into the atmosphere and instead transforming it into electricity.
“To convert a temperature gradient to an electric current requires some trickery,” she said. “For a material to be a good thermoelectric material, you need a high electrical conductivity, but a low thermal conductivity. Usually these two things don’t go together. You have to trick the material to find ways to reduce the thermal conductivity without affecting the electrical conductivity.”
She is also teaming with fellow MechSE assistant professor Sanjiv Sinha to design interfaces that promote high thermal transport, for advanced cooling applications.
Ertekin also applies computational expertise to advance developments in photovoltaics.
“About 85-90 percent of photovoltaic solar cells on the market are silicon based,” Ertekin reported. “However, there are conceivably thousands of unexplored semiconducting materials that could be cheaper to fabricate, less expensive to refine from the raw, that could reduce the cost by several orders of magnitude. Yet, these alternative materials have only received a small fraction of the research attention that silicon has received.”
Her research group has explored the optical properties of highly doped or “black” silicon in collaboration with Harvard and MIT scientists, who use lasers to introduce a high concentration of defects into the silicon.
“If you do this with the right type of defect and in the right quantities, the light absorption of the silicon increases substantially in the sub-band gap regime,” Ertekin said. “This introduction of defects at this high nonequilibrium concentration significantly affects the optical properties of the material and our computer modeling helps to understand why.”
Last March, she participated in a workshop held at CalTech on accelerating the development of photovoltaic materials. The event brought together researchers from around the world to talk about how to speed up the rates of identification and development of alternative materials for photovoltaics. Later this month, she’ll attend an international conference on defects in semiconductors.
The Ertekin Research Group uses sophisticated computer modeling in a number of collaborations. Currently, Ertekin is collaborating with several Illinois colleagues-- Lane Martin (materials science and engineering, MatSE), Ed Seebauer (chemical and biomolecular engineering), and with several faculty members in Kyushu University in Japan through the International Institute for Carbon Neutral Energy Research (I2CNER) on ways to convert sunlight to chemical energy.
Ertekin said that up until this point, discovering the potential of materials for photocatalytic energy conversion--specifically production of hydrogen by splitting water--has been to a large extent trial-and-error-based. The advent of computational modeling has made it much less of a guessing game.
“Lane Martin’s group members are experts in atomic level synthesis of oxide heterostructures,” Ertekin explained. “We’ve been able to model some of these structures, particularly those integrating titanium dioxide with other exotic oxides, with the goal of improving photo-catalytic performances. We’ve been able to predict how the interface structure between various integrated oxide systems can affect properties such as polarization, which in turn affects the surface chemistry, which finally can the affect the overall rate of conversion of solar energy to water splitting and hydrogen production.”
Ertekin, Martin, Seebauer, and MatSE professor Angus Rocket recently received funding from the College of Engineering's Strategic Research Initiative to pursue research on “Atomic-Scale Design of Oxide Heterojunctions for Energy Conversion.” The award is to “pursue a transformative approach for designing and synthesizing oxide heterojunctions for photocatalytic energy conversion devices.”
Similarly, Ertekin is using electronic structure modeling tools to figure out how to develop metal alloys that are more lightweight, yet stronger, and whose mechanical properties exhibit a higher temperature resistance. Ertekin is using quantum mechanics simulation as well as continuum scale simulation in the hopes of optimizing performance.
In just its second year, Ertekin’s team is already seeing results. First from a validation standpoint, where computational predictions about potential defect properties for oxides, solar cells and other photo catalytic materials have been accurately predicted against results in the lab.
Ertekin indicates that the world is in serious need of these new materials and energy resources sooner than many may realize.
“It took 100 years to optimize the performance of a solar cell to convert solar sunlight to electricity,” she said. “I don’t think we can afford to take another 100 years on some of these other issues as we have in the past. At the end of the day, with the added benefit of computational modeling, we are demonstrating that we can really speed up that process.”