Solar Thermoelectric Energy Conversion

Transcription

1 Solar Thermoelectric Energy Conversion Gang Chen Massachusetts Institute of Technology Cambridge, MA NSF Nanoscale Science and Engineering Grantees Conference December 5-7, 2011, Arlington, VA

2 Nano for Energy Increased surface area Interface and size effects Molecules Λ = nm λ=1 nm Λ---Mean free path λ---wavelength Photons Λ > 10 nm λ= μm Electrons Λ= nm λ=10-50 nm Thermodynamics Kinetics Phonons Λ= nm λ=1 nm

3 Energy Technology Constraints Cost Efficiency Favorable Thermodynamics Favorable Transport Environmental Portability

4 Thermoelectric Energy Conversion COLD SIDE COLD SIDE - + HOT SIDE I N P HOT SIDE Nondimensional Figure of Merit Joule Heating Seebeck Coeff. Electron Cooling ZT = 2 σs T k Reverse Heat Leakage Through Heat Conduction

5 Device Efficiency Zebarjadi et al., Energy & Env. Sci., in press.

6 Nanoscale Effects for Thermoelectrics Interfaces that Scatter Phonons but not Electrons Electrons Λ= nm λ=10-50 nm Phonons Λ= nm λ=1 nm THERMAL CONDUCTIVITY (W/ mk) K X,BULK (FOURIER LAW) K Z,BULK (FOURIER LAW) K Z,FILM, EXPERIMENTAL Si K X,FILM, EXPERIMENTAL 0.5 Ge 0.5 BULK ALLOY (300K) In-Plane P=0.6 P=0.5 Cross-Plane Lines--Fitting with CHen'sModel Superlattices 10 0 P= TEMPERATURE (K) Nanocomposites

7 Nanostructured Thermoelectric Materials Poudel et al. Science, v. 320, p. 634, 2008

8 Nanocomposite Synthesis Increase interfacial scattering by mixing nano-sized particles. Batch fabrication for large scale application. Graphite piston Graphite cylinder Sample powder A Current for heating Force for pressing Poudel et al. Science, v. 320, p. 634, 2008 Nano Bi 2 Te 3 Professor Z.F. Ren Boston College

9 Recent Progress in ZT Zebarjadi et al., Energy & Env. Sci., in press.

10 From Micro Watts to Giga Watts Vehicles Power Plants μw W kw MW GW Sensors Stove Furnace Solar Industrial Waste Heat

11 Solar Energy Utilization Solar Fuel Solar Electricity: PV ynth/overview.html Solar Heating homesolarpvpanels.com Solar Electricity: Thermal-Mechanical

12 Solar Hot Water Systems

13 Solar Thermal Installed Capacity, 2009 China in 2009, total of 134 Million m 2 Evacuated Tubes

14 Solar Thermoelectric Energy Conversion US Patent No : E. Weston in 1888 M. Telkes, JAP, 765, 1954 Efficiency: 0.63%

15 Heat Flux Consideration q = k ΔT L 1 W m K 100 K L q=1000 W/m 2 (1 Sun); L=100 mm q=100,000 W/m 2 (100 Sun); L=1 mm

16 Possible Configurations Solar Radiation Optical Concentrator Optical Concentration p n Selective Surface Area A s Enclosure

17 Solar Thermoelectric Power Conversion Kraemer et al., Nature Materials, 10, 532, 2011

18 GMZ/ goal x current state 18 Efficiency (%) Eye-Balled Data from 1 st Solar APS Presentation Series Year

19 Phonon Engineering Host Λ nano < Λ bulk Λ bulk Nanoparticles Thermal Conductivity k 1 1 = CωvωΛωdω = CvΛ 3 3 Specific Heat Speed of Sound Mean Free Path

20 First-Principles Computation of Phonon Thermal Conductivity

21 Phonon Mean Free Path Distribution Zebarjadi et al., Energy & Env. Sci, in press.

22 Optical Measurement of Phonon Mean Free Path D=55μm D=30μm D=15μm Thermal conductivity (W/mK) Temperature (K) Literature TTR, D=55 μm TTR, D=30 μm TTR, D=15 μm Minnich et al., PRL, 107, , 2011

23 Phonon MFP Distribution D q q Bω Dω ~ D Λω Minnich et al., PRL, 107, , 2011

24 Pushing to Nanoscale Bulk TC of sapphire T = 300 K 400 nm

25 Modulation Doping Zebarjadi et al., Nano Letters, 11, 2225, 2011.

26 High Thermal Conductivity Polymers NSF Grant No. CBET Shen et al, Nature Nanotechnology, Shen et al, Nature Nanotechnology, Henry and Chen, Physical Review Letters, 101, , 2008.

27 Summary Significant progress made in materials ZT. New solar thermoelectric generators with excellent application potential. Understanding phonon and electron transport in bulk nanostructures is very important for further ZT improvements and thermoelectric technology. Sponsors: DOE EFRC S 3 TEC on solar thermoelectric NSF on polymers and phonon transport