Q: What sparked your interest to pursue a career in science?
Praveen Thallapally: I pursued my career in science because it provides solid evidence on measurable and reproducible results that are accountable for the exploration of new discoveries.
Q: Why did you choose materials chemistry?
PT: My graduate studies were focused on engineering atoms and molecules with pre-designed properties based on the understanding of covalent and non-covalent interactions. Based on this experience, I wanted to broaden my field from molecules to materials that have enormous applications for science and engineering.
Q: What projects are you working on right now?
PT: Right now I am working on three different technologies. The first is funded by ARPA-E and strives to achieve higher efficiency in commercial heating, ventilation, air conditioning and refrigeration systems by developing a new type of adsorption chiller using metal organic heat carriers (MOHC) and select refrigerants. Adsorption chillers use low-grade or waste heat to drive a thermal compressor and the performance is strongly dependent on the adsorption properties - uptake capacity and enthalpy - of the MOHC-refrigerant pair. In this project, the new absorbents are based on MOHCs that are self-assembled with metal clusters and organic building blocks to yield porous MOHCs with tunable binding energy with refrigerants. The tunable sorbents will be designed to have enthalpies of adsorption that are 10% or more below the latent heat of vaporization of the refrigerant. Higher mass loadings and lower latent heat is possible with these materials, which would represent a fundamental breakthrough in performance of adsorption chiller technology.
The second project is working towards lower cost, higher efficiency geothermal applications using new biphasic metal organic working fluids. The metal organic solid is molecularly engineered to reversibly uptake and release selected compounds during the Rankine cycle. A geothermal system that uses biphasic working fluid would be able to extract more heat from the source, reducing the capital costs and expanding the range of geothermal resources.
Finally, I'm also working on an advanced carbon capture and sequestration project that hopes to develop storage technology with a near-zero emissions - a grand challenge with enormous economic benefits. We're developing and testing various classes of micro-porous materials to selectively separate CO2 over other gases. The selective uptake and faster kinetics of these materials could reduce the cost of carbon capture and sequestration technology by a factor of fifty percent or more.
Q: As a post-doc, you developed frustrated organic solids - what makes this compound unique?
PT: The frustrated organic solids are bowl-shaped molecules that trap solvent molecules. This material appears to be very promising for separating carbon dioxide from gas mixtures. Another great advantage of this material is hydrophobicity - it does not react or uptake water.
Q: Tell us about Molexol materials - how can these help advance carbon capture technology?
PT: Molexol is a new class of crystalline material that is engineered to selectively capture carbon dioxide at standard temperature and pressure. These materials can potentially be implemented in a coal-based power plant for low cost carbon dioxide capture from flue, synthetic and natural gas streams. Molexol materials have many advantages over other materials including a higher capacity to hold CO2 than frustrated solids, hydrophobicity, low cost regeneration and high selectivity to CO2.
Q: Which projects are you watching (beside your own)?
PT: The recently announced Fuels from Sunlight Energy Innovation Hub.
Q: Did you have a role model who inspired you to become a scientist?
Dr. Thallapally's favorite tool, pressure vessels | Photo Courtesy of PNNL
PT: My role model is my father. Though he does not have any science training, he is interested in nature and the environment around him. He inspired me to become a scientist.
Q: Just a few more questions - what can you never start a day at the lab without?
PT: A weighing balance.
Q: What is your favorite tool in the lab?
PT: Pressure vessels that are used to discover new Molexol materials.
Q: What do you enjoying doing in your free time?
PT: Playing games with my three year old son.
Find out more about Dr. Thallapally and other projects at PNNL at www.pnl.gov.