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Simulations Couple with Experiment to Boost Energy Research

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Top: Simulated image of a nanoporous graphene sheet. Bottom: graphical representation of lignocellulosic biomass based on a supercomputer model

Two recent studies highlight important synergy between theory and experiment and between key DOE facilities in cutting-edge energy research.  In both, the researchers are at Oak Ridge National Laboratory (ORNL) and they used ORNL experimental facilities with NERSC supercomputers.

Scientists working to improve gas extraction and storage conducted experiments at the High Flux Isotope Reactor facility and NERSC to study more efficient extraction methods from shale using nanoporous materials. Another group used the Spallation Neutron Source and NERSC to study more effective ways of converting biomass consisting of woody plant matter into biofuels.

Why it Matters: The gas extraction research is considered an important step toward establishing cleaner coal-based energy production and improved carbon sequestration technologies for problematic greenhouse gases. 

The biomass research is important because although there are abundant biomass resources available, current processes for using it are extremely expensive and understanding the mechanism of biomass breakdown via pretreatments will lead to more efficient use. 

Key Challenges: A key challenge in custom desigining materials for gas storage is understanding how traits like pore size affect natural gas adsorption.  This means understanding the relationship between local structure and macroscopic properties as well as fundamental mechanisms that control nanomaterial properties in bulk. 

A key challenge in biomass fuel production is creating inexpensive, efficient methods of pretreating the highly resistent protective plant cell walls that evolved in plants for strength and resistance to degradation.  This requires a molecular-level understanding of processes that span huge time and spatial scales, from atomistic levels to larger cellulose and lignin polymer structures.  

Accomplishments: Electronic structure computations have allowed an accurate description of adsorbate–adsorbent interaction, complementing experimental techniques that can be used to examine the function of pore sizes. Calculations provide reasonable agreement for pore-size-dependent adsorbent properties, for both hydrogen and methane uptake. 

The biomass researchers identified fundamental forces that change plant structures during pretreatment.  The team’s experiments and simulation revealed, unexpectedly and counterintuitively, that as biomass is heated, the bundle of cellulose fibers dehydrates.  This water release causes the cellulose fibers to move closer together and become more crystalline, which makes them harder to break down.

More Information: Gas extraction work: NERSC PI: Valentino R. Cooper (ORNL); NERSC Project Title: Theoretical Studies of Complex Materials; NERSC Resources Used: Edison, Hopper, Global Scratch, Global Project, HPSS;  paper published in the Journal of Materials Chemistry A; NERSC news story

 More Information: Biomass recalcitrance work:  NERSC PI: Jeremy Smith (ORNL); NERSC Project Title: Molecular Dynamics Simulations of Protein Dynamics and Lignocellulosic Biomass;  paper published in Green Chem. , 2014, 16, 63-68, DOI: 10.1039/C3GC41962B; ORNL news story