EnergyandNanotechnology-MIT.pptVIP

Motivation Energy and Nanotechnology Gang Chen Rohsenow Heat and Mass Transfer Laboratory Mechanical Engineering Department Massachusetts Institute of Technology Cambridge, MA 02139 Sources Nano for Energy Nanoscience Research for Energy Needs Examples Thermoelectrics Devices Nanoscale Effects for Thermoelectrics State-of-the-Art in Thermoelectrics Potential Applications Challenges and Opportunities Mass production of nanomaterials Energy systems: high heat flux * Photons L 10 nm l=0.1-10 mm Phonons L=10-100 nm l=1 nm Electrons L=10-100 nm l=10-50 nm L---Mean free path l---wavelength Molecules L = 1-100 nm l=1 nm Increased surface area Interface and size effects Catalysis by nanoscale materials Using interfaces to manipulate energy carriers Linking structures and function at the nanoscale Assembly and architecture of nanoscale structures Theory, modeling, and simulation for energy nanosciences Scalable synthesis methods National Nanotechnology Initiative Grand Challenge Workshop, March, 2004 Gr?tzel cell for photovoltaic generation and water splitting Catalytic nanostructured hydrogen storage materials Radiation transport to maximize absorption Two phase flow Electrochemical transport Multiscale, multiphysics transport Mass transport Heat transfer (intake and release) Small scale thermodynamics Two phase flow Multiscale and multiphysics COLD SIDE HOT SIDE Power Generation I N P I I Cold Side Hot Side Diffusion Figure of Merit: Thermal Conductivity Electrical Conductivity Seebeck Coefficient Critical Challenges: Reduce phonon heat conduction while maintaining or enhancing electron transport Electron Phonon Power Generation: T(hot)=500 C, T (cold)=50 C ZT=1, Efficiency = 8 % ZT=3, Efficiency =17 % ZT=5, Efficiency =22 % Refrigeration Phonons L=10-100 nm l=1 nm Electrons L=10-100 nm l=10-50 nm Electron Phonon Interfaces that Scatter Phonons but not Electrons Molecular Dynamics (Freund) PbTe/PbSeTe S2s (mW/cmK2) 32