Post on 14-Apr-2017
MEEN 489/689:
Entrepreneurship & Nanomaterials for
Energy Applications
Lecture 6:
Diffusion & Failure at the Nanoscale
Synopsis of the Energy Sector
James Donnell, Andreas Polycarpou,
Tanil Ozkan, Haejune Kim
Fall 2015
19/8/2015
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You won’t be tested on the derivation but
should be able to explain why diffusion is
faster at the nanoscale.
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What can be done to avert mechanical
failure while keeping the process scalable?
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Application: Hard disk drives
R. Wood, J. Magn. Magn. Mater. (2008)
Nanotechnology 1:Ultra thin (and robust) films and super smooth (or structured) surfaces
Nanotechnology 2:Head-disk interface (nanometer level spacing and features) at 100 mph
A. Recent Thermal Flying Control technology shifted the interface interactions to smaller (nm) scales B. Proposed Heat Assisted Magnetic Recording possesses temperature challenges
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Hard disk drive (HDD) mechanics
D. Weller, Seagate
Slider
Magnetic disk
Slider
Original Flying Height Adjusted Flying Height
Protruded Pole Tip
)747(66.70
57.0
25.1
10)( Boeing
m
mm
mm
nmSlider =
< 1mm
Runway or road
Need reliable flying at 100 mph of few nm spacingHow to do it?Is small better?
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0 1 2 3 4 5 60
10
20
30
40
50
60
Separation, h (nm)
Ad
hes
ive
Fo
rces
(m
N)
Table 1: FvdwEq. (4): FIDMTEq. (1): FelEq. (16): Fel,roughEq. (17): Proposed Model
3 3.5 4 4.5 5 5.50
0.1
0.2
0.3
0.4
0.5
0.6
Separation, h (nm)
Ad
hes
ive
Fo
rces
(m
N)
Two flat parallel surfacesProposed (rough surface)
0 1 2 3 4 5 60
10
20
30
40
50
60
Separation, h (nm)
Ad
hes
ive
Fo
rces
(m
N)
Table 1: FvdwEq. (4): FIDMTEq. (1): FelEq. (16): Fel,roughEq. (17): Proposed Model
3 3.5 4 4.5 5 5.50
0.1
0.2
0.3
0.4
0.5
0.6
Separation, h (nm)
Ad
hes
ive
Fo
rces
(m
N)
Two flat parallel surfacesProposed (rough surface)
Roughness = 0.74 nm
Radius = 5.22 µm
Asperities = 9.33 µm-2
Total lube = 10 ÅMobile lube = 5 ÅContact Force = 0.151 N/m
Nominal contact = 300 um2
Adhesive Force Comparison (Flat-on-Flat vs. Rough
Surface)
The most important difference between idealistic smooth and “rough” cases is that the range of adhesive forces is LARGER when roughness is included
Rough surface model indicates rise of adhesion at higher flying-height
Suh and Polycarpou, JAP (2006)
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9/8/2015
Coal:
10,000 tons of coal per day
(1 freight train)
Nuclear:
100 tons of uranium per year
Hydroelectric:
60,000 tons of water per second
Comparison of power plants for 1 GW
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9/8/2015
Energy portfolio of industrialized nations
Although most of our energy originally comes from the Sun (except nuclear), only a
minuscule amount of solar energy is being used today.
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Electrical Storage
Chemical Storage
Storing energy
Energy/Weight
Energ
y/Volu
me
0
10
20
30
0 10 20 30 40
Energy Storage Density Gasoline
Batteries
Supercapacitors
• How do we store solar electricity overnight, wind electricity when calm ?
• The range of all-electric cars is short due to poor storage by batteries.
• Batteries have 30-50 times lower energy density than gasoline.
• Chemical energy is easy to store in fuel, but electricity is not.
Ethanol
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Electricity potential of our Sun (photovoltaics)
100×100 square kilometers of solar cells could produce all the
electricity for the US. But they are still too costly.
0.4 TW
US Electricity Consumption
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The required area of solar cells
1 kW/m2 (Incident solar power)
× 1/4 (Fraction of useful daylight)
× 0.16 (Efficiency of a solar cell ≅ 16%)
× 100×100 ·106 m2 (100×100 km2)
= 4 · 108 kW (Electric power generation in the US)
0.4 TW
US Electricity Consumption 16
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COMPANYPERCENT
SOLARIKEA 87%
GM 43%
VF Outdoor 33%
Johnson &
Johnson24%
REI 21%
Costco 17%
Kohl's 13%
Anheuser-
Busch 13%
Campbell's
Soup 12%
Hartz 11%
Walmart 5%
Macy's 5%
Whole Foods 5%
Bloomberg 4%
Tiffany's 3%
Safeway 3%
Commercial Users by Percent of Facilities with Solar PowerThe table below lists companies in order of the percentage of their facilities that are solar powered.This list provides another comparison for those companies that ranked highly in both installed capacity and number of installations. Note, this list is exclusively populated by companies surveyed for this report and does not include smaller companies that might otherwisebe considered to have higher ratios than presented below.
www.seia.org/researc
h-resources/solar-
means-business-2014-
top-us-commercial-
solar-users
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How much would it cost to generate all
the electricity in the US by solar cells ?
1 $/W (Price of solar cells)
× 4 ·108 kW (Electric power generated in the US)
= 4 ·1011 $
= 400 Billion Dollars
The support structure adds substantial costs.20
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Fuel from the Sun ?
• Photosynthesis
• Biofuels
• Split Water
Plants convert solar energy to chemical energy
but the efficiency is low (1%-2%)
Convert plants to fuel: Make ethanol, diesel fuel from
sugar, corn starch, plant oil, cellulose ...
Split water into hydrogen and oxygen using sunlight.
Use hydrogen as fuel. No greenhouse gases. (Futuristic)
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Biofuels versus photovoltaics (PV)
How far could one drive a car with the energy produced by 100x100 m2 (2.5 acres) of land in a year ?
Biodiesel: 21 500 kmBioethanol 22 500 kmBiomass to liquid: 60 000 kmPhotovoltaics, electric car: 3 250 000 km
Solar cells are more efficient than photosynthesis.Electric motors are more efficient than combustion engines.
PHOTON International, April 2007, p. 106 (www.photon-magazine.com)25