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11/6/2012
1
Overview to Solar PV
Professor Richard R. Lunt Department of Chemical Engineering and Material Science,
Department of Physics, Michigan State University
Solar PV Training Session I
Nov 2nd, 2012
Outline – Week 1
• Review of Solar Energy Potential
• How PVs Work
• Materials New and Old
• Theoretical Limits/Next Generation
____Break_____
• PV Configurations and Wiring
• PV Toys!
• Conclusions
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2
Map of the World Scaled to Energy Consumption by Country
Newman, U. Michigan, 2006
In 2002 the world burned energy at a rate of 13.5 TW/yr
How fast will we burn energy in 2050 ?
Energy use estimates from Nocera, Daedalus 2006 & Lewis and Nocera, PNAS 2006
If we use energy like in U.S. we will need 102TW
Conservative estimate 28~35TW
How much is 13TW per Year?
100 Billion 100W Bulbs Running all
Year
82,000 Billion Hamburgers =
32 burgers per day per person!
Drive in car (40mi/gal.) =
Driving 1 time around earth per person per
year
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Worldwide Energy Supply
REN21 2006 global status report on renewables
Geothermal
Hydroelectric
Nuclear
Solar
Where do we use energy:
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How does the US use energy?
Motivation for Clean Renewable Energy
IPCC 4th Assessment Report, plot from NASA
Climate Change Predictions
High growth Moderate growth
Low growth
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5
0
10
20
30
40
50
Energ
y Pote
nti
al (T
W)
Potential of Alternative Energy Sources
Practical potential
(10% eff., 1.5% of Land)
N. Lewis “Powering the Planet” (MRS Bulletin 32, 2007)
• 13TW – Worldwide Consumption, 3TW - US consumption
• 120,000 TW provided by the sun
• 300 x 300 km2 at 10% = 3TW <2% of land mass Total PV ever produced, worldwide
Global LCD production in 2008
U.S. Newspaper production, per year
Photovoltaics
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6
There are several Major Reasons
• It costs too much. And it requires a lot of area (even
though it is a small fraction)
• Our Electrical grid can only handle ~20% input from intermittent sources
• There is no Sun at night so we need BIG batteries
There are several Major Reasons
• It costs too much. And it requires a lot of area (even
though it is a small fraction)
• Our Electrical grid can only handle ~20% input from intermittent sources
• They can be unsightly
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7
Flavors Of Solar Energy Generation
Luminescent Solar Concentrator
Solar Thermal - Heating
Solar Thermal - Geometric Collector
Steam Turbine Electricity
P Abs Carnot
Solar Electrical – PV
1 CCarnot
H
T
T
~
J. Kalowekamo and E. Baker, Solar Energy 83, 1224 (2009).
Cost
US Average 2010: 5¢/kW-hr
20% Most Expensive 2010: 12¢/kW-hr
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Present AVERAGE
Cost of Deploying
Solar Energy
is 20¢ to 40¢/kWh
Cost of a kWeh varies across the U.S.
TODAY SOLAR CAN COMPETE IN SOME OF THESE ELECTRICITY MARKETS
(without additional government incentives)
Aim to capture 10% of electrical generation with Solar PVs
14¢
US Average 2010: 5¢/kW-hr
20% Most Expensive 2010: 12¢/kW-hr
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9
Cost
1Kalowekamo, et al. Solar Energy 83 (2009) 1224-1231. 2Lushetsky, “The prospect for $1/Watt Electricity from Solar,” $1/W Workshop, August 10, 2010.
Costs (Cont.)
DOE, $1/Watt White Paper
DOE Targets
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Costs (Cont.)
DOE, $1/Watt White Paper
DOE Targets
Costs (Cont.)
DOE, $1/Watt White Paper
11/6/2012
11
What happens if we get to $1/W Equivalent?
Locations (by State) where Solar PV become price competitive
DOE White Paper: “$1/W Photovoltaic Systems”
Efficiency Comparison
18%
20%
29%
29%
31%
31%
63%
DOE White Paper: “$1/W Photovoltaic Systems”
Suntech,
First Solar
Heliatek
GaAs
http://www.solar-facts.com/panels/panel-manufacturers.php Long list of Manufacturers:
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12
0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.20
5
10
15
20
25
30
35
Effic
ien
cy (
%)
Band Gap (eV)
Approaching Shockley-Quiesser
GaAs 85% of SQ, Si 75% of SQ
Which is more widespread? Depends on Application
Green Prog. Photovolt.: Res. Appl, 2011. NREL, available online http://www.nrel.gov/ncpv/
(2012)
c-GaAs c-Si
c-InP
CIGS CIS
c-Ge CZTSSe
a-Si
CdTe c-GaInP
Organic
AM1.5G Isotropic
1% PL
Figures of Merit: kW/m2, $/kW-hr, kW/kg,
kW-hr/$-kg
Cost of Si
• High Temperature Processing: 1687K-2000K
• $1/g $20/m2 (Raw Material Cost), $200-$400/m2 (full device)
• Ultra High Purity Needed
a = 102 cm-1
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Cost of Organic Materials
• Abundant: ~100,000 tons of CuPc/year
• Low materials costs: ~$1/gm 17¢/m2 , $20-100/m2 (full device)
• Low Temperature Processing RT-500K
This is where Chemical Engineers Come in!
Copper Phthalocyanine
a = 105 cm-1
Operating Principles
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500 750 1000 1250 1500 1750 20000
1
2
3
4
5
0.0
0.5
1.0
1.5
2.0
Sola
r F
lux (
Photo
n/n
m3-s
)
Wavelength (nm)
Photo
pic
Lum
inosi
ty (
norm
.)
500 750 1000 1250 1500 1750 20000
1
2
3
4
5
0.0
0.5
1.0
1.5
2.0
Sola
r F
lux (
Photo
n/n
m3 -s
)
Wavelength (nm)
Photo
pic
Lum
inosi
ty (
norm
.)
VIS
Solar Flux
Absorption Spectra of PV Materials
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15
Processes in PV
A DS CC
p n i
Processes in Bilayer PV
A ED CT DS CC A ED CT DS A ED CT A ED A
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16
Processes in Organic Bilayer PV
Ideal Diode
Jph
0 exp 1p
SC
S P
RI qVJ J J
Area R R nkT
V
J
Current-Voltage Simplified Equation
OC SC
Power VI
Max Power V I FF
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18
Third Generation Concepts • Primary Losses of Efficiency for Single-Junction
1) Incomplete Absorption, 2) Thermal Relaxation (Heating),
3) Carrier Recombination, 4) VOC must be < EG,
5) Shape of Photocurrent curve
Henry, C. JAP 51, 4494, 1980
Third Generation Concepts
• Concepts to go beyond Single Junction Limits
– Primarily to reduce thermal, voltage, or abs. losses: (Hot-carrier, Concentrator, Singlet Fiss., MEG, Tandem)
Up-Converter
Henry, C. JAP 51, 4494, 1980
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A Taste of The Research That We Do Here at MSU
e-
Windows – 55-80% Transmission1)
Can Do it with Molecules Excitons!
Absorb NIR, Transmit VIS
Need OPV with abs. peak outside VIS
- Sig. surface area with glass surfaces
- Glass 1/3 Module Cost
- Infrastructure – 1/2- 2/3 BOS Cost
Is there a way to do this with inorg. SC?
Transparent Solar Cells
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• 2/3 Solar Flux in NIR/IR Single Junction Limit (20%), 10-cell
Tandem (33%)
• Use Excitonic Materials to optimize Transparency and Efficiency
Transparent Solar Cells
Practical Demonstration
Lunt, R. et al. APL, 98, 113305 (2011).
Single Devices:
Monolithic Series Integration:
Large-Area Integration:
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21
Lets Talk PV Practicals!
PV Configuration
Grid-tied with battery
backup system.
Off-Grid DC system
(with/without inverter):
PVinsights.com
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22
Panel Assemblies
• How much voltage do we get
in each cell, panel?
• Why are they wired up this
way?
PV Education.Org
11/6/2012
25
Solar Charger
Can we do this?! Yes, Sometimes.
It depends on the Sun Intensity!
Solar Charger
Charging Battery
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Solar Charger
Charging iPod
Solar Charger
Battery Acts as Buffer!
We use it for Temporary Storage
11/6/2012
27
Solar Charger
If there is not a lot of light, we will not charge battery!
We will DISCHARGE BATTERY!
Solar Charger
Diode acts a one-way valve for the Current
Flow
Insert Diode ?
11/6/2012
28
How Long will it Take to Charge?
What will it depend on?
1) Area of Solar Cell
2) Amount of Sunlight
3) Solar Cell Efficiency
Lets do a calculation
4) Solar Cell Orientation
Determine Local Solar Insolation
NREL, PVWatts v1
11/6/2012
29
Units for Solar Calculation!
/W J s
63.6 10kW hr x J
2 241
kW hr W
m day m
Sun Intensity at High Noon average for US
(titled at 37° tilt):
21 1000
WSun
m
Average over year in Lansing
(including night) for flat panel:
2 23.83 160
kW hr W
m day m
Used in electricity billing!
Solar Insolation Units
Watts = Energy Flux
Max flux higher! (~760W/m2)
Ideal Diode
_OCMP
LOAD MP
MP SC
VVR
I I
OC SC
Power VI
Max Power V I FF
To get here: we need a load:
Load
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30
PV Configurations
Series Connection: Parallel Connection:
Combination:
Maximum Power Point Tracking
Current-Voltage Characteristics are Dependent on Light Intensity
Current-Voltage changes, changes Maximum Power Point
Added electronics to get most power out of Solar Cells – Add Cost
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31
Finger Spacing – Collecting Charges
PV Education.org
Degradation and Failure
Solar Cell Degradation (Corrosion, H20, O2)
Short-Circuited Cells
Open-Circuited Cells
Module Glass Breakage
Module Delamination
Hot-Spot Failures
By-Pass Diode Failure
Encapsulant Failure
PV Education.Org
11/6/2012
32
• There is enough solar energy to power USA, and entire World!
Quick Summary
• To do this we need:
– Better Grid
– Better Energy Storage
– Cheaper Solar Cells
• Inexpensive materials and processing
• Lightweight
• We Learned about practical aspects
- Types of Solar Energy
- Factors impacting efficiency, cost
- Configuration/Wiring
- Calculate charging time