Motivation

Energy and NanotechnologyGang Chen

Rohsenow Heat and Mass Transfer LaboratoryMechanical Engineering DepartmentMassachusetts Institute of TechnologyCambridge, MA 02139

Sourceshttp://www.sc.doe.gov

Nano for Energy Increased surface area Interface and size effects

Nanoscience Research for Energy NeedsCatalysis by nanoscale materialsUsing interfaces to manipulate energy carriersLinking structures and function at the nanoscaleAssembly and architecture of nanoscale structuresTheory, modeling, and simulation for energy nanosciencesScalable synthesis methodsNational Nanotechnology Initiative Grand Challenge Workshop, March, 2004

ExamplesGrtzel cell for photovoltaic generation and water splittingCatalytic nanostructuredhydrogen storage materialsRadiation transport to maximize absorptionTwo phase flowElectrochemical transport Multiscale, multiphysics transportMass transportHeat transfer (intake and release)Small scale thermodynamicsTwo phase flowMultiscale and multiphysics

Thermoelectrics DevicesFigure of Merit: Thermal ConductivityElectricalConductivitySeebeckCoefficient Critical Challenges:Reduce phonon heat conduction while maintaining or enhancing electron transportElectronPhonon Power Generation: T(hot)=500 C, T (cold)=50 C ZT=1, Efficiency = 8 % ZT=3, Efficiency =17 % ZT=5, Efficiency =22 % Refrigeration

Nanoscale Effects for ThermoelectricsElectronPhononInterfaces that Scatter Phonons but not ElectronsMolecular Dynamics (Freund)

State-of-the-Art in Thermoelectrics

Potential ApplicationsIn US, transportation uses ~26% of total energy.Transportation

Challenges and OpportunitiesMass production of nanomaterialsEnergy systems: high heat flux