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Energy Storage & Conversion Lab
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Selected Projects
Design Space of High-Porosity Foams
The graphic comparisons of dimensionless effective properties of lattice-based structures, shell-based triply periodic minimal surface (TPMS) structures, and hybrid foams clearly illustrate structurally dependent trends. Effective properties include effective thermal conductivity, permeability, and mechanical stiffness. The charts comparing dimensionless effective properties are independent of the properties of the base materials, and only reflect the impact of topology. These charts can aid in the selection of porous structures in diverse applications.
Topology Reconstruction
We used a parallel superposition scheme to accelerate the Yeong-Torquato (Y-T) algorithm for digital microstructure reconstructions. This method can produce large-scale 2D and 3D structures of porous battery and fuel cell electrodes from a single 2D SEM or TEM image within minutes.
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Machine Learning Assisted Property Predictions
We used a convolutional neural network (CNN) model to predict effective thermal conductivity from images. The prediction time is 15 ms for a single image with 128 × 128 pixels, which is 3-5 orders of magnitude faster than a computational fluid dynamics simulation. This approach with high accuracy and computational efficiency enables iterative topology optimizations.
Characterize Physical Properties of 3D Printed Structures
The next-generation thermal- and water-management systems are critical to NASA's economical, reliable, and safe access to space. Novel capillary evaporators and condensers using specially designed wicks can enable high heat fluxes with extremely low thermal resistance. The capillary forces in these wick structures will have superior evaporator and condenser performance to create lightweight thermal and water management systems for NASA missions. We measure pore-scale morphology of porous wick structures made from additive manufacturing and other approaches, carry out the pore-scale simulations of liquid-vapor two-phase heat and mass transfer, and design experiments to validate simulation results.
Direct Methanol Fuel Cells
The direct methanol fuel cell (DMFC) generates electricity directly from methanol at near room temperature. This project is a multi-university collaboration that aims to directly use highly concentrated methanol solutions or even pure methanol as the fuel without increasing the methanol crossover rate. The project will systematically investigate and engineer both the water and methanol managements of DMFCs through experiments and model simulations in order to obtain high fuel cell performance with various concentrations of methanol solutions.
Lithium-Air/O2 Battery
The rechargeable lithium-air battery has a very high specific energy but the low oxygen concentration in battery electrodes usually lead to low reaction rates and currents. Moreover, the solid products generated during discharging, such as Li2O2, block micro pores in the cathode electrode and impede the oxygen transfer. The transport phenomena in the electrode have great impacts on the efficiency, capacity, current density and the capacity retention rate after cycles. This project investigates the pore-scale morphology of the battery electrode, understand the mechanism of the solid precipitation in the porous electrode, and design novel electrodes with advanced discharge and charge performance.
Battery Thermal Management
During operation, the LIB’s high energy density generates large amounts of thermal energy during battery operation. Without proper thermal management, these batteries experience accelerated performance degradation and are at higher risk for thermal runaway, especially when operated at high temperatures or high current rates. The core of our battery management system is the integration of low-density metal foams with phase change materials (PCMs) to leverage metal foams’ high thermal conductivity and mechanical strength and PCM’s high energy density. This project will measure and predict effective thermophysical properties (conductivity, permeability etc.) of various PCM-foam composite materials based on high-resolution tomography measured by tomographic X-ray microscope. The knowledge learned from the pore-scale simulation enables design and manufacture of foam materials with unique non-isotropic properties.
Techno-Economic Analysis
The techno-economic analysis will quantitatively compare the life cycle cost (LCC) of several energy storage and conversion technologies used in material handling industry, portable devices, transportation applications, residential and commercial buildings: internal combustion engine, rechargeable battery, and fuel cells. The analyses will included the initial cost of the power sources, operating cost, as well as the greenhouse gas (GHG) and particulate matter (PM) emissions considering the full fuel cycle of the fuel. In order to compare the GHG and PM emissions of different fuels (gasoline, propane, electricity, hydrogen, natural gas, biofuel etc.) on a fair basis, this project will compare the emissions throughout the full fuel cycle of these fuels rather than only the emissions on the end user site. The environmental, social, and economic impacts of new energy technologies will clearly indicate their feasibility as the next generation technologies.