Thermoelectrics (TE) at the Nanometer
Sun-to-Fiber (S2F) at the Micrometer
Nobuhiko “Nobby” Kobayashi
Nanostructured Energy Conversion Technology and Research (NECTAR) Baskin School of Engineering, Univ. of California Santa Cruz
(Santa Cruz, California)
Advanced Studies Laboratories Univ. of California Santa Cruz and NASA Ames Research Center
(Moffett Field, California)
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013 1
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Santa Cruz off-Campus (2300 Delaware Ave. Santa Cruz)
Introduction to Univ. of California Santa Cruz
Silicon Valley Campus (Advanced Studies Laboratories at NASA ARC)
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
TE @
the Nanometer
1x10-6m
3
200 nm
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
Background and Motivation
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Solid state heat engine
Hot Cold Heat
engine
Work
Mechanical heat engines with
efficiencies ~40% produce 90%
of the required energy.
Waste heat generated
annually is ~18TW .
Converting even 1% of the
waste heat into electricity
($0.11/kWh) could create a
$20B annuity.
http://www.instantg
oldrefining.com/
http://www.thedaily
green.com/
interestingenergyfacts.blogspot.com/
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
Background and Motivation
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Solid state cooler
Hot Cold Cooler
Work
www.zalman.com S. Borkar (Intel)
http://www.ecse.rpi.edu/frisc/the
ses/GargThesis/chapter6.html
Annual energy cost of the
U.S. data centers was $4.5B.
(61BkWh) in 2006 (EPA 2007).
Cooling consumes ~40%.
Heat generation is spatially
and temporally non-uniform.
Hot spot can be >650W/cm2.
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
Background and Motivation
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Competitors
http://en.wikipedia.org/wiki/Stirling_engine www.sunshinekelly.com
Refrigerator COP ~5.9
TE cooler COP ~0.7
Stirling engine h ~40%
TE module h ~10%
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
Traditional Thermoelectrics
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Limitations of bulk materials
ZT = S2sT
kl + ke
S: Seebeck coefficient
s: Electrical conductivity
kl : Lattice thermal conductivity
ke: Electronic thermal conductivity
T: Temperature
hmax = hc (1+ZT)0.5-1
(1+ZT)0.5+1
Maximize s: metal
Minimize kl + ke wood
S ~ ds(E)/dE, s(E) = n(E)m(E)q
S ~ dn(E)/dE dm (E)/dE
S ~ dg(E)/dE dt (E)/dE
g: Density of states
t: Scattering time
E: Energy http://britneyspears.ac/physics/dos/dos.htm
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
Traditional Thermoelectrics
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Limitations of bulk materials
http://www.its.caltech.edu/~jsnyder/thermoelectrics/
S ~ dg(E)/dE dt (E)/dE
http://britneyspears.ac/physics/dos/dos.htm
Low-dimensional semiconductor
Energy filter
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
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Our “Nano” approach 1: Metal-semiconductor nanocomposites
200 nm
Advanced Approaches
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
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Our “Nano” approach 2: Nanowire network
Flexible TE device employing
silicon nanowires Physica Status Solidi (a) 209, 171 (2012)
Nanowire network (silicon)
Advanced Approaches Hot Power Inc.
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
S2F @
the Micrometer
1x10-6m
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5nm
5nm
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
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A large amount of energy from the sun
Background and Motivation
In a single hour the sun delivers the same amount of energy as consumed by all
of humanity in a year – about 5 × 1020J.
http://www.keepbanderabeautiful.org
Sun light Light No transportation Light Light Light Heat
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
Sun light Electricity Transport Electricity Light Electricity Heat
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Concentrated sun light into an optical fiber
Strategy
Sun light Concentration Transportation Light Daylighting
Use as heat or
storage for later uses
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
http://en.wikipedia.org/wiki/Thermal_energy_storage
http://www.syneco.co.uk
http://kjcoop.com
greenpowerscience.com
http://www.familievink.nl
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Concentrated sun light into an optical fiber
Strategy
Himawari System
La Foret Eng (Tokyo, Japan)
Oak Ridge System
Sunlight Direct (Oak Ridge, TN)
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
Concentrated sun light into an optical fiber
Goal
Optical tr
ansm
issio
n
line
Optical colle
cto
r/con
centr
ato
r
Solar light
Solar light
NA mismatch
Mode size mismatch
Refractive index mismatch
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f 5m f 60mm
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
Concentrated sun light into an optical fiber
Goal
Need thin films with 1.4 < n < 2.8 for 400-1000nm and k as small as possible
16 NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
Optical fiber
n = 1
n = 1.5
Enabling thin film technology
Concentrated Sun Light into an Optical Fiber
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Niobium oxide (TEM, scale bar 5nm) Zirconium oxide (Right TEM x200k)
Aluminosilicate (SEM, scale bar 3mm)
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
1mm
with without without with
without with
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Devices
Concentrated Sun Light into an Optical Fiber
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
Courtesy: David Berkstresser and Allan Lewandowski
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Ultimate application
Concentrated Sun Light into an Optical Fiber
http://inhabitat.com
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
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Really ultimate applications
Concentrated Sun Light into an Optical Fiber
http://mcensustainableenergy.pbworks.com www.getsolar.com
www.rainbowskill.com
Eliminate working fluid Eliminate heat engine
Eliminate tower
1m2 concentrator for
solar daylighting
25m2 concentrator for
solar thermal power
generation
Demaray and Kobayashi at the NREL solar furnace
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013
Acknowledgement
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Sponsors and Students
Kate Norris David Fryauf Junce Zhang
Juan Diaz Amanda Flores
NCCAVS Joint User Group Topical Conference, San Jose, California, February 21, 2013