Carbon Capture Technologies
Carbon capture and sequestration technologies are being developed as part of the plan for a sustainable energy future. The U.S. Department of Energy (DOE) has set goals for carbon capture systems at 90% carbon dioxide (CO2) capture with less than a 35% increase in cost of electricity. Carbon capture is the separation of CO2 from the exhaust gas of a power plant for later sequestration. There are several pre- and post- combustion designs being investigated for carbon capture systems. The CEL investigates the operation post-combustion carbon capture using low temperature supported polyamine based solid sorbents. Solid sorbent systems offer an advantage over other capture technologies because they can reduce the regeneration energy associated with CO2 capture and reduce parasitic load. As part of the DOE's Carbon Capture Simulation Initative (CCSI) we develop device-scale models of solid sorbent carbon capture systems. The work focuses on modeling the multi-phase reactive transport and heat transfer in fluidized bed systems which are being devleoped for use with large scale coal burning power plants.
Volume Fraction of Solid Sorbent Particles
High Temperature Fuel Cells
Solid oxide fuel cells (SOFCs) are high temperature fuel cells, which are being developed for large scale and distributed power systems. SOFCs promise to provide cleaner, more efficient electricity than traditional fossil fuel burning power plants. Research over the last decade has improved the design and materials used in SOFCs to increase their performance and stability for long-term operation; however, there are still challenges for SOFC researchers to overcome before SOFCs can be considered competitive with traditional fossil fuel burning and renewable power systems. In particular degradation due to contaminants in the fuel and oxidant stream is a major challenge facing SOFCs. In the CEL we investigate degradation in SOFC electrodes through computational modeling at the meso- and continuum-scales. We develop reactive transport and electrochemistry models to study the fundamental mechanisms of degradation and to understand how low conditions with the electrodes affect the overall performance of the SOFC.
Chromium Poisoning in the Cathode Sulfur Poisoning in the Anode
Subsurface Reactive Transport
Understanding the transport and reactions of species in connected porous media and macro-pores in porous media is central to many engineering and science problems such as contaminants in the subsurface, and carbon capture and sequestration. For example, at the U.S. Department of Energy’s Hanford site in southeastern Washington State, the subsurface transport and reactions of uranium species is an issue, which engineers and scientists have been studying for a number of years. Storage of radioactive waste in trenches and underground storage tanks led to the release of large amounts of radioactive waste into the subsurface at the Hanford site, including a 350 m3 plume of radioactive waste containing over 7000 kg of hexavalent uranium (U(VI)) (Liu et al., 2006). The composition of the subsurface at the Hanford site is a mix of sand and gravel which leads to a porous medium with large connected macro-pores, and smaller pores ranging in size from sub-microns to tens of microns in width.
The complex multi-scale nature of porous media often leads to anomalous transport conditions, and presents a major challenge for computational models. We aim to develop multi-scale and meso-scale models which are able to simulate transport in porous media and connected macro-pores surrounded by a porous medium with a wide range of pore sizes and connected macro-pore apertures. In such porous media, a pore-scale model with a very large number of degrees of freedom would be needed to adequately resolve both the connected macro-pores and the small intra-granular voids in the porous matrix around the macro-pores. The computational cost of such a model limits the size of the domain and the time scales which can be investigated. Instead multi-scale and hybrid models can be used to simulate the complex multi-physics in these systems. The hybrid model explicitly discretizes the connected macro-pores and uses a continuum model with effective transport properties to represent the porous matrix.
Advanced Battery Technologies
Li-air batteries have a theoretical specific energy rivaling gasoline and could provide practical specific energies equivalent to gasoline. They are able to achieve a high specific energy because of the high energy content of Li and the use of O2 as a reactant, which negates the need to store the reactant in the battery; instead O2 is accessed through a porous, open air cathode design. Li-air batteries have shown the greatest potential for developing a high capacity, rechargeable batteries for applications in hybrid and electric vehicles. Some of the main barriers to commercialization for Li-air batteries center on: degradation with cycling, low achievable specific capacity, dendrite formation on the Li anode and the formation of insoluble products in the cathode.
Computational modeling can be used to investigate the performance and degradation of Li-air batteries and to develop novel microstructures and cell designs to reduce degradation with cycling and improve the performance and stability of Li-air batteries.